Energy Resources (AS) (Complete) Flashcards
Why and how have energy resources developed?
-Using human labour to do every task is slow, hard work
-Using animals or harnessing power of water/wind released time to develop new activities; make life easier
-Changes in energy resources continued w/ development of new technologies that harnessed new resources, increased efficiency of energy use/allowed energy to be converted—> more useful forms
What enabled the development of useful items and tools like cutting blades?
Smelting of metals using wood & charcoal enabled development of a range of useful items, eg cutting blades, nails, wheel rims, ploughs, & other tools
What energy developments did the Industrial Revolution bring from the 1700s?
-Developed use of coal & coke to produce steel—> was used to manufacture sophisticated machines, eg steam engines. These were used in many ways, like to pump water out of mines, transport goods, plough, drive timber saws & grain-threshing machines, and textile mills
-A major development= ability to generate power where it was needed by transporting coal in contrast to wind & water power that had to be used where they could be harnessed
What increased the amount of energy that can be used in the 1800s?
Crude oil, natural gas + other fuels
What has access to large amounts of fossil fuel energy enabled?
The production of a wide range of things including unnecessary products, non-essential travel and has permitted waste of energy.
Why have secondary fuels, like electricity, become increasingly important?
-Are often more useful than primary fuels from which they were produced -Many tools + convenient equipment like telecommunications systems, motors, lighting & electromagnets in appliances like audio speakers require electricity, could not be run directly from primary fuels harnessed directly from environment
What is the impact of converting energy from primary to secondary fuels not being 100% efficient?
Reduces the amount of energy that is available to be used
How have ancient civilisations and industrial societies contrastingly developed?
-Ancient civilizations developed when + where soil & climate made possible production of sufficient food to support population
-Industrial societies developed in places where fossil fuels occurred naturally/where they could be transported easily
What can the increasing use of renewable resources create?
New industrial centres locally where energy is harnessed/more disparately as energy storage & transfer become more effective
How have new uses of energy allowed the development of society?
-Tasks completed more easily
-New activities allowed
Why has the per capita energy consumption increased?
As population has grown, world’s consumption of energy has ↑in total as has per-capita consumption
What are examples of direct and indirect consumptions of energy?
-Direct uses include energy used by people individually, eg heating & lighting ther homes, cooking, personal transport, use of electrical appliances etc
-Indirect uses include; energy used by commercial organisations, schools, government + industry to provide goods & services, support economic activity, eg transport of goods, manufacturing processes, water treatment, & energy used in agricutture
Factors affecting per capita energy consumption in different countries; Affluence?
-Higher income= people buy, consume & use more energy in activities like travelling, using less efficient vehicles, heating larger home & having more energy-using appliances
-More energy is used during manufacture of additional products bought
-Affluent countries use significantly more energy to construct housing in production of bricks, glass, tiles & fittings like carpets, furnishings & appliances
-Not all countries have access to readily available sources of energy; shortages limit transportation, ability to access water, power equipment & preserve foods
-Supply + demand for energy resources set prices on world market
-Global market prices= usually low enough for more affluent communities to afford to purchase energy tor essential uses like purifying water, running hospitals & transporting food. May be able to afford energy for non-essential uses that make life more enjoyable
-Poorer communities may be unable to pay for energy needed for essential uses; can slow development of these societies, reduce quality of life
Factors affecting per capita energy consumption in different countries; Relative cost of energy?
-In countries w/ large, easily accessible local sources, energy is cheap
eg petrol= much cheaper in US than UK—> more petrol can be used for same cost. Has encouraged use of larger, less fuel-efficient cars. Fuel efficiency; likely to be lower priority if energy= relatively cheap
-Some developed countries have a low per capita energy use within own country
-However, they import goods that used a lot of energy in their manufacture in other countries, eg steel, copper, aluminium
-Per capita energy consumption in countries like UK has gone down in recent years—> partly due to decline of industries like steel & aluminium smelting; now produced for us in other countries, eg China
What are the 4 different types of industry and their levels of energy use?
-Primary industry; agriculture, mining, raw material extraction. General level of energy use= high
-Secondary industry; heavy manufacturing industry,eg metal smelting, chemical industry. General level of energy use= high
-Tertiary industry; services like transport, finance, retail I recreation education. General level of energy use= low
-Quaternary industry; information & IT. General level of energy use= very low
How have social and environmental awareness driven changes in energy use?
-Regions & locations which historically had difficulty satisfying demand for energy often have tradition of managing energy use carefully. Scandinavia → energy shortages in past, especially remote communities; driven strong energy conservation culture
-In UK → access to large deposits of coal drove Industrial Revolution & society’s development, but energy also used wastefully. As coal mining ↓, access to natural gas & oil from N sea extended extravagant use of energy
How does the climate affect energy usage?
-Buildings in locations w/ cold winters require heating & those in v hot areas require air conditioning
-High winds ↑ heat losses while sunny weather ↑ passive solar heat gains
What are examples of how energy is used in agriculture and fisheries?
-Fuel for machinery, eg tractors & combine harvesters, water pumping, fish farm aeration
-Manufacture of chemicals like fertilisers
-Food processing, eg sugar refining, grain drying & milling
-Transport of materials & harvested food
-Storage, especially refrigerated foods
-Fuel for fishing boats, water pumping & aeration in aquaculture
What are examples of how energy is used in other industries?
-Machinery operation; excavators, rock crushing, pumps, presses, conveyor belts, mixers, cutters, lathes
-Heat to melt materials for moulding & casting of metals & plastics
-Energy for chemical reactions; smelting metals, thermal decomposition of limestone in cement manufacture
-Heat for baking, eg pottery, bricks
-Heat for distillation, eg fractional distillation of crude oil
-Water treatment for public supply
-Sewage treatment
What are examples of how energy is used domestically?
-Space heating
-Lighting
-Running appliances, eg refrigerators, washing machines, dishwashers, cookers
What are examples of how energy is used for transport?
-Transport of goods; ships/ trains/trucks/conveyor belts/pipelines
-Transport of people; cars, buses, trains, planes
What are examples of how industrial development has caused changes in energy use?
-As countries like Brazil, China & India have industrialised, their use of energy has ↑ rapidly, especially in mining & manufacturing industries
-As heavy industry + manufacturing activity have ↓ in UK, so has industrial energy use
What are examples of how income levels have caused changes in energy use?
-↑ in income = consumers afford to pay more for energy, eg heating, lighting & transport
-Affluence enables higher consumption of goods, ↑ energy required for manufacture & transport
-Household appliances like washing machines, TVs & fridges require energy to run. As segments of societies in developing countries like India
& China became more affluent, domestic consumption ↑
What are examples of how population growth has caused changes in energy use?
-Total energy use ↑ w/ population growth even if per-capita use remains the same
-If population of developing country = graving rapidly, may struggle to ↑ energy supplies fast enough to match demand
What are examples of how changes in environmental awareness have caused changes in energy uses?
-May lead to choices that lead to lower energy consumption, like;
- Better building energy conservation
- Choices of vehicle type & usage
- Choices of consumer goods
- Food choices
- lLevel of recycling
Features of energy resources; what is the different between renewable and non-renewable energy resources?
-Renewable; naturally re-form relatively quickly so using them doesn’t necessarily ↓ future availability, eg solar, wind, wave, tidal, geothermal & biofuel energy
-Non- renewable; not being formed/ re-form so slowly that current use ↓ amount available for future use, eg fossil fuels, uranium
Features of energy resources; what are depletable energy resources?
Where use can ↓ future availability. Include all non-renewable resources & those renewable resources where unsustainable exploitation may ↓ availability, eg wood; forests are felled faster than they re-grow
Features of energy resources; what is the abundance of an energy resource and what factors impact its availability?
Measures # of resource existing; not the same as # available for use as there may be other factors restricting availability, eg;
- fossil fuels deep underground, cannot be extracted
- winds high above ground when aerogeneraters can’t be located
- wave power far from coast where water = too deep to anchor equipment
- low intensity sunlight that can’t produce high temps
New technologies &↑ energy prices may make resources that can’t currently be used viable in future
Features of energy resources; how do locational constraints impact energy resources?
-Energy resources aren’t evenly distributed; each has its own locational factors
-Energy sources that can only be accessed via extraction like fossil fuels & uranium ore must be located in more favourable deposits
-Energy sources that harness natural processes may depend on regional/ local features like climate & topography
What are the main locational factors & required conditions for fossil fuels?
-Can only be extracted where economically exploitable deposits exist
-Power stations require access to; fuel supplies, condenser cooling water (large river/ lake/sea), suitable construction site
What are the main locational factors and required conditions for nuclear power?
-High energy density fuel = easily transported
-Power stations require access to; condenser cooling water (river/ lake/ sea), suitable construction site
What are the main locational factors & required conditions for solar power?
-High light intensity
-Low cloud cover
What are the main locational factors & required conditions for wind power?
-Areas w/ strong, reliable winds like; shallow seas, open plains, upland areas
-Areas w/ low land-use conflicts (especially for large wind farms); not areas of high ecological sensitivity, not close to urban areas, not in areas of high scenic importance
What are the main locational factors & required conditions for wave power?
Coastal areas w/; strong, reliable winds over water, reliable prevailing wind direction, long fetch (long stretch of water over which wind blows)
What are the main locational factors & required conditions of Hydro Electric Power (HEP)?
Areas w/;
-High, reliable rainfall
-Site for small dam w/ large reservoir basin
-Large catchment area
-Impermeable bedrock
-Stable geology
What are the main locational factors & required conditions for biofuels?
-Nearby forest areas
-Farmland for biofuel crops
-Farmland for crop/ livestock waste
-Nearby urban areas for food waste/sewage
What are the main locational factors & required conditions for geothermal power?
Areas w/;
-Hot rocks near ground surface
-Recent volcanic activity
What are the main locational factors & required conditions for tidal power?
Areas where;
- Tidal range= large
-Coastal features that focus tidal flow to ↑ flow velocity/tidal power
Features of energy resources; what is intermittency in energy resources?
If an energy resource isn’t available at times when it’s needed then it’s difficult to rely on it, eg wind, solar, tidal power
Features of energy resources; what is predictability within energy resources?
-It’s important to know how much energy will be available & whether it’ll meet demand for energy
-Some resources= intermittent but time they’ll be available can be predicted accurately, eg tidal power, ; means plans can be made to use alternative resources when they’re unavailable
-Other resources are both intermittent & unpredictable, eg solar power & wind power
Features of energy resources; what is energy density and how is it significant?
-Measure of # of energy in given mass of energy resource, eg. oil, coal, uranium, wood.
-For some resources, eg many renewable resources, it’s the # of energy harnessed by given mass of equipment
-Generally, high energy density resources are most useful as smaller quantities are needed so storage + transport are easier and it is easier to reach ↑ temps
-A low energy density resource is often less useful if used directly, but it can still be useful. Eg; Solar & wind power have low energy density but electricity produced can be used to paver technologies w/ a high energy requirement
What is the order of energy density from highest to lowest of selected energy resources?
Nuclear fusion/fission, hydrogen, fossil fuels, wood, wind power and solar power
Features of energy resources; how is resource availability impactful?
-Potential contribution of a resource to energy supplies= clearly affected by # of energy available
-Can be difficult to estimate how much of resource can be harnessed
-May be abundant resources which can’t be exploited w/ any existing technology/ likely to be developed, eg wind at high altitude
Features of energy resources; why is there a need to convert energy resources to increase usefulness?
-Form in which energy is harnessed → not necessarily form in which will be delivered to end-user
-eg chemical energy of fossil fuels is converted to heat, potential, kinetic then electrical energy before it can be used to power electrical appliances
-Some resources that currently seem to be of little use may become important if appropriate technologies are developed to convert them to more useful energy forms
Features of energy resources; how is applicability to specific uses significant?
-Available energy resources have shaped the way that societies have developed, so it can be difficult for society to change to using energy resources w/ different characteristics
-Renewable energy resources → making more significant contribution to our energy supplies, have different characteristics from fossil fuels & nuclear power
-^While a number can generate electricity, none can reach temp levels that fossil fuels create/produce liquid fuels in good quantities to power all vehicles
Features of energy resources; why is ease of storage significant?
-Energy demand & supply levels vary, rarely balance
-Being able to store energy → important so it’s available when required
-Some energy resources like chemical energy in fossil fuels can be stored easily, especially due to their high energy density; where small mass/ volume stores large # of energy
-Some energy resources, eg solar, wind, wave can’t be stored unless they’re converted into other forms. Can be converted thermal/chemical/ GPE which can be stored
Features of energy resources; why is ease of transportation significant and what is it impacted by?
-Energy resources are rarely found in areas where demand is highest, so must be transported
-Affected by properties like form of energy & energy density
How is coal mainly transported and what happens alternatively if too difficult?
-Ship, train
-Often used in large scale industries like electricity generation/ smelting iron. It’s often easier to transport electricity & steel than coal, so power stations + iron & steel works → often located near coal fields/deep water parts where coal is imported
How is crude oil mainly transported and how is it utilised?
-Pipeline, ship, rail tanker
-Transported in large quantities from oil fields to oil refineries where refined products are made, like aviation fuel, petrol, diesel, fuel oil
-Bulk transport methods used
How are refined oil products transported and where are they distributed?
-Pipeline, ship tanker, rail tanker, truck
-Products of oil refining → usually distributed to relatively local consumers in ↓ quantities than crude oil
What are the ways in which natural gas is transported and why?
-Pipeline, liquefied natural gas (LNG) ship tanker, rail tanker
-Can be piped easily from gas fields—> areas where demand is high, eg large industries/urban areas w/ large # of consumers
-Natural gas, in its gaseous form, has a ↓ energy density so transport by ship where pipelines don’t exist require liquefaction to ↑ energy density
How are fissile fuels, like uranium, transported and why?
-Solid fuel rods/pellets by rail or truck
-Relatively small quantities of fissile fuels need to be transported due to high energy density
-Are transported in solid form in containers designed to withstand fire and impact; may have outer casting for more protection
How are biofuels transported and why?
-Road, rail, ship
-Each has its own transport features
-Liquid biofuels, og alcohol, have quite ↑ energy density so transport over long distances = practical
-Solid biofuels, eg straw → very bulky law mass per unit volume so long distance transport may not re practical as transport energy inputs may be high
What is done to primary fuels; solar, wind, hydroelectric tidal and geothermal because they can’t be transported?
-Conversion to other energy forms that can be transported
-Can be used to generate electricity that can be transported
How is electricity transported and why?
-High voltage AC/DC electricity grid
-Overhead power cables = cheaper to install & maintain than underground cables
Features of energy resources; why are environmental impacts significant?
-Exploitation of all energy resources damages environment in variety of ways; some obvious, like pollution during extraction & use of fossil fuels but link w/ impacts like global climate change may be less obvious
-All energy resances cause damage via manufacture of equipment needed to exploit them
Features of energy resources; why is technological development significant?
-All technologies have period of development before they can be used practically, followed by period of further development when technology is refined to improve it so becomes more efficient, effective, cheaper
-Can be difficult for new technology to be financially viable during early development if has to compete w/ existing technologies; whose development costs have already been paid for + have economic benefits of mass production
Features of energy resources; how do political influences aid the energy industry?
Governments may decide to provide assistance to particular sections of the energy industry, to;
-Support development costs of new technology, eg grants for developing new renewable energy technologies
-Increase national energy security, eg grants/ tax reduction for oil exploration
-Reduce environmental impacts, eg EU grants for low carbon technologies
Features of energy resources; how do energy resources cause economic implications?
-It’s not easy to calculate full cost of using energy; price paid by energy user doesn’t always cover total costs including environmental damage & cost of mitigating these
-Burning fossil fuels → pollution, including acid rain; produces financial impacts elsewhere, eg building damage. Cost aren’t paid by energy users
-It’s difficult to assess cost of some impacts, as issues aren’t fully understood
Features of energy resources; how are different energy projects paid for?
-Cost of energy project can be divided into running costs during operational life & set-up costs to make & install equipment
-Running costs → paid w/ income from energy produced
-Set-up costs → often paid for w/ loans with interest
-If renewable energy project is compared w/ non-renewable of same actual post renewable energy project may still be at financial disadvantage
-Cost of renewable energy projects= mostly initial cost of equipment, w/ very low running costs, so most of expenditure= from loan. Cost of non-renewable energy project—> mainly running costs, especially fuel, which won’t require loan w/ interest payments
-So, renewable project has to cover higher interest payments, making total cost higher than the non-renewable energy project
How has resource depletion impacted the sustainability of current energy use?
-Fossil fuels provide most global energy supplies but are non-renewable; availability must decline in future as reserves deplete
-New technologies & ↑ market prices may convert more of resource into reserves so they can be exploited, but principle of resource depletion = still controlling factor that must restrict supplies eventually
-There are still large reserves of fossil fuels that haven’t been exploited, but rate of discovery of new deposits has ↓ dramatically since 1980s
Why will choices made about energy resources affect economic sustainability?
-Depleted non-renewable resources will become more expensive. As energy is needed for so many aspects of life; could ↓ future affluence
-Commitments made now for long-term use of expensive technologies like nuclear power could ↓ future affluence, but may help secure energy supplies
-Failure to invest in development of future energy supplies may → shortages for future gens. When a new technology is 1st introduced it’s usually expensive as development costs are still being paid for, no economies of scale in manufacturing that would eventually ↓ costs. It’s hard for these now technologies to compete w/ well established, cheap ones like fossil fuels. Waiting until depleted fossil fuels → expensive & new technologies → competitive would make energy gap as it would take time to develop technology & necessary infrastructure
How can environmental impacts of energy resources reduce sustainability?
-All energy resource exploitation has an environment impact but there’s differences in scale, type & timing of impacts
-Many impacts = temporary/local/small, so they don’t affect global sustainability but combination of these may → significant
-New technologies may be developed that’ll ↓ environmental impacts like ability to capture CO² emissions but it’d be risky to commit to further large-scale fossil fuel use before technique has been proven
What are the impacts before use of different energy resources?
-Fuel extraction; coal mining, oil extraction
-Fuel processing; coal, crude oil
-Equipment manufacture; causes environmental damage in material extraction & processing
-Site development / operation; preparing sites for equipment & associated infrastructure → habitat damage
-Transport; (of fuels) uses fossil fuels
-Embodied energy in equipment; manufacture for every resource uses energy, although # varies greatly between different resources
-Acid mine drainage & subsidence; coal mining
-Methane releases; extraction of all fossil fuels
What are the pollution damages consequential of energy resource use?
-Atmospheric pollution; fossil fuels
-Oil pollution; oil, tar sands, oil shales
-Radioactive waste; nuclear power
-Noise pollution; wind power
-Thermal pollution; steam turbine power stations
What are the habitat damages consequential of energy resource use?
-During extraction of energy resource; fossil fuels uranium, biofuel crops
-Power station & equipment location; all energy resources during equipment installation
-Ecological impacts of tidal power schemes; changes in flow velocity, tidal range, sedimentation, turbidity
-Ecological impacts of HEP schemes; downstream changes in flow velocity, turbidity, dissolved oxygen, barrier to movements of wildlife
-Pipelines & cables; oil, gas, electricity
-Depletion of reserves; non-renewable energy resources
What are the reasons for the ways that energy is supplied changing in the future?
-Some existing resources like fossil fuels & wood are becoming depleted
-Concerns on environmental damage are affecting political policies & public opinion
-Current supplies can’t meet growth in demand due to increasing affluence & population growth
-New technologies becoming available to harness, store, transport, convert energy into forms required
Future energy supplies 1- Fossil fuels; how were all fossil fuels produced?
The partial decomposition of dead organic matter under anaerobic conditions beneath layers of sediments that were deposited on Earth’s surface/seabed. Took place over long periods of time, most coal was formed 300- 360m years ago
Future energy supplies 1- Fossil fuels; what are the features that make fossil fuels ideal to use?
- They’re easy to store
-They have high energy density so can power high energy intensity activities like powering steam engines. Also means they’re relatively efficient to transport; given volume/mass contains a lot of energy
-Are often found in very abundant local deposits
Future energy supplies 1- Fossil fuels; why is the chemical energy of fossil fuels useful?
It’s easy to store and easy to convert into heat energy that’s usually required
Future energy supplies 1- Fossil fuels; why is the high energy density of fossil fuels so useful?
-High temperatures made by burning coal enables smelting of metal ores
-Burning fossil fuels reach temperatures high enough to produce high pressure steam which can spin turbines & generators in power stations to generate electricity
-Allows small mass of fuel to do a lot of work, so 5L of petrol can carry 1 tonne of car for 80km
-75t of aviation fuel can carry a 400t Boeing 747, including 400 passengers for 5,600km. If fuel had ↓ energy density then weight of fuel carried may make flight impossible
Future energy supplies 1- Fossil fuels; why are fossil fuels being finite resources significant?
-Non-renewable energy resources = finite resources → exploitation means they’ll became depleted
-Is important where industrial communities have grown up on local fuel supplies. Once local supplies are exhausted industry may only survive if supplies from elsewhere can be transported easily & economically
Future energy supplies 1- Fossil fuels; why is the amount of available resource of some fossil fuels an issue?
-Significant amounts of oil & coal = unexploitable as deposits are too deep/ found in small amounts/ located in hard to reach areas
-A lot of natural gas → trapped in fine-grained impermeable shale deposits
-Oil shale= fine-grained sedimentary rock containing solid hydrocarbons that can yield substantial # of oil & combustible gas upon destructive distillation. Most of the organic matter → insoluble in ordinary organic solvents, cannot flow to surface like crude oil. So, it must be decomposed by heating to release oil by melting it so it can flow to surface. Total contained in shale deposits> total reserves of crude oil
Future energy supplies 1- Fossil fuels; why may the large-scale use of recoverable fossil fuels not be possible despite their large quantity?
-It’s not economically viable
-May cause unacceptable pollution
-May involve habitat damage in ecologically sensitive areas
-Extraction process may cause local earth tremors
Future energy supplies 1- Fossil fuels; why is the level of technological development significant for fossil fuels?
-Industrial societies have developed using fossil fuels so technologies to exploit them = well-developed
-Many applications that use energy have been developed so they use fossil fuels, like cars, trucks, aircraft
-To change to other sauces of energy will involve many changes in the infrastructure of society
Future energy supplies 1- Fossil fuels; why can fossil fuels cause political and international trade problems?
-↑ demand drives energy-hungry countries to satisfy own energy needs; can influence political decisions to protect future supplies at expense of ↓ both local & global environmental impacts
-Crude oil → basis of most of world’s energy but deposits are unevenly distributed across globe; majorly in Middle East, so is the focus of both trade & political interest
Future energy supplies 1- Fossil fuels; how have fossil fuels created economic issues?
-Economic activity + international trade can drive countries to make decisions based on cheapest options; may not be best long-term
-When cheap natural gas became available in UK → contributed to closure of deep coal mines even though many coal deposits remained, could still be extracted. Even though North Sea gas reserves will be exhausted in next 30/ 40 years, it want be possible to reopen coalmines as they have flooded & are unsafe
-Fossil fuels generate economic costs like pollution damage; not paid for by energy industry but by others like agriculture, forestry, health service
Future energy supplies 1- Fossil fuels; what are the extraction methods for coal and how are they done?
-Deep mining & open cast mining
-Deep mining; labour intensive so relatively expensive to produce large # of coal
-Open cast mining; mechanised so usually more economically viable but as it’s necessary to clear all rock above coal it’s only viable in locations where coal is close to surface
-Deep deposits, very thin seams can’t be accessed by either method
Future energy supplies 1- Fossil fuels; what are the environmental impacts caused by the extraction methods of coal?
-Environmental damage caused by deep mining → predominantly at surface via habitat loss, transport infrastructure & potentially surface subsidence
-Open-cast mining causes greater habitat damage
Future energy supplies 1- Fossil fuels; what are the extraction methods for oil and gas?
-Petroleum (crude oil) in liquid form flows through permeable rock & collects in porous rock in pores between particles
-When a pipe is drilled ↓ to these reservoirs, oil will be forced to surface by natural pressure of gas above oil/water beneath oil
Future energy supplies 1- Fossil fuels; what are the environmental impacts from oil & gas extraction methods?
-Oil spills from oil rigs → pollution
-Oil-based drilling mud used to lubricate drill pipes → pollution in groundwater, rivers & sea
-Surplus gas on oil rigs may be burnt / ‘flared’ to ↓ risk of explosions, causes atmospheric pollution via pollutants like sulfur dioxide, carbon dioxide & smoke
-Natural gas= extracted by similar means to oil extraction, forced to surface by own natural pressure
Future energy supplies 1- Fossil fuels; what are the environmental impacts of coal mining?
Habitat loss, noise, dust, turbid drainage water, spoil heaps, acid mine drainage, methane releases, derelict sites
Future energy supplies 1- Fossil fuels; what are the environmental impacts of oil extraction and transport?
Oil pollution marine, seismic surveys, habitat damage due to pipeline construction
Future energy supplies 1- Fossil fuels; what are the environmental impacts of the combustion of fossil fuels?
-Atmospheric pollution: Carbon dioxide, sulfur dioxide, oxides of nitrogen, carbon monoxide, smoke
-Ash disposal
Future energy supplies 1- Fossil fuels; what are the main uses of crude oil?
- Liquid vehicle fuels; petrol, diesel, aircraft fuel, ship fuel oil
- gas fuels for heating; propane, butane
- petrochemicals; plastics, feritilisers, pharmaceuticals
Future energy supplies 1- Fossil fuels; what are the main uses of natural gas?
-Domestic & industrial heating
-Electricity generation
-Chemicals: nitrate fertilisers
Future energy supplies 1- Fossil fuels; what are the main uses of coal?
-Electricity generation
-Iron & steel industry
New fossil fuel technologies; how does coal gasification benefit coal exploitation?
Coal too deep to be mined can be burnt underground under controlled conditions to produce mixture of fuel gases like hydrogen, carbon monoxide & methane
New fossil fuel technologies; how does coal liquefaction benefit coal exploitation?
-Involves conversion of coal to liquid hydrocarbons which have applications that solid coal can’t perform like liquid vehicle fuels
-Coal may be converted to liquids directly w/ solvents or indirectly w/ gasification then chemical changes to convert gaseous hydrocarbons → liquid hydrocarbons
New fossil fuel technologies; what is primary oil recovery and its process?
-Well-established method using natural pressure of water below oil/ gas present above oil/ dissolved in it
-Pressure forces oil ↑ production well to surface
-Approx 20% of oil is usually extracted
-Pump-jack fitted at ground level on production well may be used to ↑ flow rate
New fossil fuel technologies; what is secondary oil recovery and its process?
-Involves pumping water/natural gas down injection well to maintain pressure & flow of oil
-↑ total recovery rate to approx 40%
-Some CCS schemes pump recovered CO2 underground to ↑ oil recovery
New fossil fuel technologies; what is tertiary oil recovery and its process?
-Includes techniques ↓ viscosity of oil, also called Enhanced Oil Recovery (EOR)
-Steam (generated by burning fuel/solar heating schemes via parabolic concentrators) may be pumped ↓ to heat oil
-Oil viscosity may also be ↓ by controlled underground combustion → heats it up
-Detergents/solvents ↓ surface tension of oil, make it flow more easily
-Bacteria used to partially digest heavy oil & produce lighter oils flowing more easing. They also make CO2 → helps maintain pressure & flow of oil
-Typically ↑ total recovery rate to approx 60%
New fossil fuel technologies; what is directional drilling and what are its advantages?
-Allows wells to be drilled that aren’t vertical, many advantages;
-Many wells can be drilled from single platform
-Possible to drill underneath locations where drilling rigs couldn’t be placed, eg urban areas
-Drilling can follow weaker/ softer rock strata to make drilling quicker & can target multiple small reservoirs up to 10km from well head → can significantly ↑ total recovery rates
New fossil fuel technologies (oil); what are subsea production wells and what do they allow?
-Located on seabed, have no platform at sea surface
-Allow operations in water up to 2000m deep but new developments will allow greater depths
New fossil fuel technologies (oil); What are Remotely Operated Vehicles (ROVs) and Autonomous Unmanned Vehicles (AUVs) used for?
Can be used to carry out seabed surveys, inspect underwater production equipment & pipelines
New fossil fuel technologies (oil and natural gas); what is the process of fracking?
-Large volumes of crude oil & natural gas → trapped in pore spaces of shale rocks w/ Iow permeability (called tight oil & gas)
-Hydraulic fracturing uses ↑ pressure to open fissures in surrounding shale rock along which oil/gas can flow towards recovery well
-Water, sand grains & solvents may be pumped into fissures to ↑ recovery rate
New fossil fuel technologies (oil and natural gas); what are the concerns over fracking?
Experience in USA shows tracking can cause environmental problems but good management may minimize these. Examples;
-Natural gas may enter aquifer water
-chemicals injected underground may enter aquifers/reach surface, cause pollution
-Toxic metals naturally present in rocks may become mobile
-Large volumes of water are needed
-Earthquakes; natural tensions in crust due to continental drift & isostatic movements post erosion may cause earthquakes. Fracking may release some of these tensions, but shoudn’t cause earthquakes that wouldn’t occur naturally
New fossil fuel technologies (oil and natural gas); how can potential problems due to fracking be reduced?
Methods like collection & treatment of waste water, reuse of waste water & restrictions on location of fracking sites in sensitive areas
New fossil fuel technologies (oil); what are the 2 methods of extracting tar sands?
-Sands are quarried w/ large excavators, then treated w/ hot water. Produces emulsion of oil droplets that floats, can be separated. 1 barrel (150L) of oil is produced from 2T of tar sands. About 75% of oil is recovered, waste sand is backfilled into mine
-In-situ production uses steam injection/solvent/controlled combustion in deep deposits to make liquid oil → can be pumped to surface. High energy inputs make extraction expensive
New fossil fuel technologies (gas); what does Enhanced Gas Recovery (EGR) involve?
↑ gas recovery rates w/ techniques like injection of CO2/nitrogen around edge of gas field to maintain pressure & gas flow
New fossil fuel technologies (gas); what is methane hydrate/clathrate and is it exploited?
-Solid ice-like crystalline solid found in locations at low temps like polar regions/under high pressure, eg oceanic sediments around continents
-Not exploited commercially now but could yield more methane than conventional natural gas sources
New fossil fuel technologies (gas); what are the proposed methods for exploiting methane hydrate oceanic sediments?
-Water heating; hot water is pumped into sediments, which melts hydrate crystals, releasing methane gas
-Depressurisation; drilling into sediments causes pressure to ↓. Methane gradually dissociates from hydrate crystal
-CO2 injection; at ↑ pressures, CO2 can form bonds w/ ice crystals but bonds more strongly than methane. Injecting CO2 could displace methane, can then be collected. Could also be used as part of CCS scheme
New fossil fuel technologies; how can CCS benefit fossil fuel use?
-Involves range of developmental technologies which would store coz produced by fossil fuel use &↓ CO2 releases
-In theory could make extended use of fossil fuels possible
-Its unlikely that CCS could be applied to small, dispersed uses like vehicles but it may be possible to use it to capture CO2 at large power stations then use electricity to make non-carbon fuels like hydrogen
Future energy supplies 2: nuclear power; what does nuclear power involve + equation?
Conversion of small amounts of matter into energy as atomic nuclei split/ join: e=mc²
E = energy released
M= mass of matter lost
C= speed of light
Future energy supplies 2: nuclear power; what does nuclear fission and fusion involve and when is energy released?
-Huge # of energy is released during destruction of small # of matter
-Large # of energy are released when small # of matter from nuclei of atoms are destroyed
-Nuclear fission; splitting of nuclei of large atoms like those of isotopes uranium-235 & plutonium-230
-Nuclear fusion; joining of nuclei of small atoms like those of isotopes hydrogen-2 & hydrogen-3
Future energy supplies 2: nuclear power; why is nuclear power usually used for ‘base-load’ electricity supplies, needed all the time?
The power output of nuclear reactors normally changes quite slowly
Future energy supplies 2: nuclear power; what are the factors that have restricted the growth of nuclear power?
-Technology is very complex → difficult to use in less technologically advanced societies which can’t support industrial infrastructure needed
-Complex technology needed= very expensive
-Strong public opposition to nuclear power in some countries due to concerns over safety, esp following reactor accidents, eg Chernobyl, Ukraine 1986 & Fukushima, Japan 2011 + impacts such events have on short & long term health of people + environment
-Concerns about possible links between nuclear materials for civil uses & military/terrorist use
-Uncertainty over permanent disposal of radioactive waste
-uncertainly over total $ of nuclear power since no commercial reactor has been fully decommissioned
Main features of nuclear fission; why is its high energy density beneficial?
-Nuclear fuel used in nuclear power stations have very ↑ energy density so small # of fuel releases large # of energy
-1 kg of uranium fuel can release as much energy as 13T of coal
-So, nuclear power stations do not need continual supplies of large # of fuel, so can be located where transport infrastructure isn’t as good as that required for coal-fired power station
-Nuclear reactors provide power for some surface ships, many submarines; rarely need to be refuelled, don’t need air supply to operate
Main features of nuclear fission; why is the embodied energy required for nuclear fission significant?
-Despite its high energy density, processes required to make fuel & complexity of nuclear power stations require lots of energy
-Coal requires very little processing but uranium must be purified, concentrated & chemically processed to produce fuel
Main features of nuclear fission; why are fissile materials being finite resources significant?
-Fissile materials, eg uranium & thorium= non-renewable resources, so # existing ↓ as they’re used, but depletion will only become an issue if supplies become restricted → more dependent on technological ability to extract them than actual # existing
-A huge amount of uranium exists but most is found in v↓ purity deposits that can’t be exploited economically at current prices
-Energy cost of extracting uranium w/ conventional methods on lower grade deposits may be > would be released when uranium underwent fission
-New technologies in future may extract fissile fuel w/ less energy
Main features of nuclear fission; how has technological development allowed nuclear reactors to be more efficient?
Nuclear reactors powered by uranium have been used for commercial electricity generation since 1950s, reactors currently being built are described as 3rd generation reactors. Lessons learned from previous reactors have allowed improvements in design;
-Longer reacted life (60+ instead of 40+)
-More reliable operation
-Lower fuel consumption
^give advantage over thorium reactors
Main features of nuclear fission; what are the environmental impacts from nuclear energy production?
-Mining & processing of uranium/thorium ore to make nuclear fuel; habitat loss, noise, dust, turbid drainage water, hazardous waste
-High embodied energy of materials used; contribution to global climate change
-Reactor accidents & radioactive waste; health risks of ionising radiation
Main features of nuclear fission; what are the possible political and international difficulties associated with nuclear fission?
Possible link between civil nuclear electricity & preparation of weapons-grade fuel has led some countries to try to restrict availability of technology to other countries considered untrustworthy
Main features of nuclear fission; why has nuclear power caused economic issues?
-New nuclear power stations → large engineering projects, very expensive
-Inclusion of new design features & unforeseen problems often cause total $ to far exceed OG estimates
-Very few old reactors have been fully decommissioned. Costs have proved to be much greater than anticipated & funds have often not been put aside from income during years of operation to pay for decommissioning
-If cost over-run is paid by state then nuclear power → receiving subsidy making it appear more economically competitive than actually is
Main features of nuclear fission; what are the uses of nuclear reactors/fission?
-Generation of electricity
-Used to propel about 150 ships
-Fission products present in used fuel; isotopes w/ other uses like caesium-137 for food irradiation & americium-241 in smoke alarms
Main features of nuclear fission; why is future use of nuclear fission very likely?
-As nuclear fuel has a↑ energy density, nuclear reactors require very little fuel → power stations can be located where transport of large # of fuels w/ ↓ energy density would be a problem
-Reactor only needs to have few tens of tons replaced a year, compared w/ 10000T of coal that’d be burnt every day in coal fired power station w/ similar electricity output
New technologies; what uranium extraction techniques have been developed?
-Polymer adsorption; uranium dissolved in seawater adsorbs onto certain polymers placed in the sea. Uranium can be washed off w/ acids then collected & concentrated
-Phosphate mining; uranium is often present in phosphate deposits, can be separated from material extracted in phosphate mines
-Coal ash; uranium can be extracted from coal ash → will become economic if price of uranium ↑ enough
New nuclear fission reactor designs; what are molten salt reactors and their advantages?
Using molten salt as a reactor coolant ↑ efficiency of electricity generation as reactor can operate at much ↑ temps w/out needing ↑ pressure to prevent coolant boiling. Liquid cooled reactors = much smaller than gas-cooled reactors → cheaper to construct
New nuclear fission reactor designs; what are plutonium reactors and their advantages?
-Almost all nuclear reactors harness energy released by fission of uranium-235, only makes up 0.7% of uranium in mined ore. Remaining 99.3% = uranium-238, not fissile but can be converted into fissile plutonium-239 by neutron bombardment within reactor
-So, reactor is using up fissile fuel but also making more via uranium-238
-Isotope not itself fissile but can be converted → fissile fuel by neutron bombardment = ‘fertile fuel’
-The ‘breeder’ realtors release energy for electricity, can make more new fissile fuel than they use, allow much more energy to be harnessed from OG uranium mined but breeder reactors= more complex, expensive
-Fission of plutonium doesn’t require neutrons to be slowed by moderator so are often called ‘fast reactors’/‘fast breeder reactors’
New nuclear fission reactor designs; what are thorium reactors?
-Thorium-232= not fissile so doesn’t release energy when bombarded w/ neutrons
-It’s a fertile fuel so can be converted to fissile uranium-232
-Reactor designs include fuel rods of uranium-233, which release energy & neutrons to maintain chain reaction
-There are also rods of thorium-232 in reactor core which ‘breed’ uranium-233 as are bombarded w/ neutrons. Uranium-233 can be extracted to make new fuel rods
New nuclear fission reactor designs; what are advantages and disadvantages of thorium reactors?
Advantages;
-Thorium is x3 more abundant than uranium
-It’s much more difficult to make weapon materials than it is using uranium
-Much less radioactive waste is made + has shorter half-lives
-No fuel enrichment is required
Disadvantages;
-Breeding rate for uranium-233 is slow so fuel is expensive
-Uranium-233 releases alpha radiation so is very hazardous
-Being a less-developed technology than uranium reactors, remaining development costs will be high
Future energy supplies 2: nuclear power; Why has producing nuclear fusion been difficult?
-Producing controllable fusion on small scale on Earth has proved difficult
-Development of methods to produce controlled fusion on Earth has proved complex
Future energy supplies 2: nuclear power; What are the sources of fuel for nuclear fusion and the reactions involved?
-Deuterium (hydrogen-2) extracted from water
Fusion of deuterium & tritium; 2/1 H + 3/1 H → 4/2 He + 1/0 n + energy
-Tritium (hydrogen-3) produced by neutron bombardment of lithium
Production of tritium; 6/3 Li + 1/0 n → 4/2 He + 3/1 H
Future energy supplies 2: nuclear power; what are the conditions needed for fusion to occur on Earth?
-Hydrogen in the form of plasma; repelling negatively charged electrons around nuclei must be removed so nuclei can collide
-Heavy nuclei; nuclei w/ greater mass → more momentum, more able to overcome repelling positive nuclei
-Very high temp; to ↑ kinetic energy of nuclei &↑ chance of nuclei colliding
-Vacuum; so plasma isn’t cooled by air
-Magnetic field; to hold plasma centrally in vacuum so doesn’t touch sides of container & cool down
Future energy supplies 2: nuclear power; what is an example of a new toroidal reactor being developed and its properties?
-ITER; new toroidal reactor that builds on the knowledge gained from Joint European Torus (JET), torus reactor near Oxford
-Should become operational around 2025 and is planned to;
-Release more energy than it uses, 500MW from 50MW input
-Maintain fusion for longer periods
-Use blanket of lithium around reactor to breed new tritium fuel
Future energy supplies 2: nuclear power; What is laser fusion and what will it involve?
-The High Power Laser Energy Research (HiPER) project will research this
-Construction planned from late 2020s
-Proposed small-scale fusion technology avoiding problems of plasma containment & refunding existing w/ torus reactors
-Small spheres of frozen deuterium & tritium would be dropped into intense laser beam to imitate fusion
Properties of renewable energy resources; how can renewable energy resources be intermittent?
-Some resources aren’t available all the time so can’t be the only source of energy used, eg solar power isn’t available at night
-Other sources can provide energy continually like biofuels, hep & geothermal power
Properties of renewable energy resources; why is predictability significant?
-It’s impossible to reliably predict # of energy that can be harnessed from some resources, eg # of sunlight reaching Earth’s surface is affected by cloud cover
-# of wind & wave power available depends on weather systems that can’t be predicted accurately
-Some renewable resources are usually available when required, eg HEP using water stored in reservoir/stored biofuels but flow of tides can be predicted accurately as future positions of sun + moon are known
Properties of renewable energy resources; why is energy density important in renewable energy resources?
-Low energy density of most renewable resources ↑ # of equipment needed, can make it difficult to power equipment needing high power/temps
-Eg solar, wind, wave power have ↓energy densities so relatively large# of equipment needed. Biofuels have a higher energy density, can be used to replace liquid fossil fuels used to power vehicles
Properties of renewable energy resources; why is ease of storage significant in renewable energy resources?
-Many renewable resources can’t be stored unless they’re converted into other forms of energy, eg solar power/kinetic energy of wind power
-Biofuels can be stored as can GPE in water in HEP reservoirs
Properties of renewable energy resources; how and why have renewable energy resources been applied to current uses of energy?
-Many modern technologies have been developed that use fossil fuels, eg internal combustion engines powering most cars, trucks, ships
-Many renewable resources provide large # of energy but may be low temp heat/electricity which aren’t useful fer many uses like powering vehicles
Properties of renewable energy resources; what are the possible environmental impacts of renewable resources?
-Usually have low environmental impacts but can restrict locations where they’re used, eg not locating windfarms in scenic areas
-Most impacts → caused by manufacture & instillation of equipment, solar lane,s & wind turbines
Properties of renewable energy resources; what are the geographical constraints of renewable resources?
Most can only be harnessed where natural processes/geographical conditions are suitable, eg solar, wind, wave power
Properties of renewable energy resources; Why is size of available resource significant in renewable resources?
-Available resource → usually controlled by natural processes producing resource
-Total resource existing may be very large but geographical constraints +↓ energy density may limit # that can be exploited
-Eg all moving air involves kinetic energy but practical exploitation needs higher velocities close enough to ground that equipment can be located to harness energy. When wind speed x2 # of energy available ↑x8 = why locating wind farms in windiest areas is so important
Properties of renewable energy resources; why is the level of technological development significant for renewable resources?
-Most renewable technologies aren’t yet fully developed; possible lack of investment/ long time period takes to perfect technology
-It’s hard for new technologies that need further improvements to compete w/ well-established technologies like those that use fossil fuels
Properties of renewable energy resources; what economic issues have renewable resources raised?
-Cost of replacing existing existing equipment w/ new equipment using renewable resources= very high
-It’s hard for renewable energy technologies to compete economically with those such as fossil fuels (early development paid for) as costs have to cover current development costs; relatively expensive due to shortness
-Differences in timing of expenditure + income can be a problem; for fossil fuel power stations, fuel costs= spread over lifetime of station, can be paid for out of income, so there’s no interest charges for fuel purchase
-Most equipment that harnesses renewable energy has no fuel costs, so as almost all costs are for purchase of equipment at start, costs of repayment of interest may make apparently cheap renewable resource financially uncompetitive
-Social & environmental costs of energy use—> rarely paid by energy industry; could include habitat loss, reduced quality of life, acid rain, photochemical smogs & global climate change. These costs are higher for fossil fuels than renewable energy, so society is effectively subsidizing some costs of using fossil fuels
-Some renewable energy technologies have reached point they can compete w/ non-renewable energy technologies, esp wind power + solar PV. The rapid growth of electric vehicles will increase usefulness of renewable energy
What are the problematic properties of solar power?
-Intermittency; availability & intensity of sunlight depends upon daily & seasonal cycles
-Reliability; daily & seasonal cycles can be predicted but changes in energy intensity caused by changes in cloud cover can’t be accurately predicted. Clouds, smoke & dust also scatter light so it can’t be focused & intensified using mirrors & parabolic reflectors
-Energy intensity; low energy density of solar power requires v large areas of solar collectors to harness significant # of energy. Angle of incidence changes in daily & seasonal cycles so there’s no single optimum position for solar power panel to harness solar power—> can reduce energy density further
What are the locational constraints of solar power?
-Can be used anywhere in the world but most viable where light levels—> highest like dry sunny deserts
-Systems that concentrate sunlight w/ parabolic reflectors only work when there’s no cloud so rays of light= parallel & reflect onto absorber
-Areas long away from equator have long summer days—> increases availability of solar power but winter days= short w/ low light levels
Harnessing solar power; how are photothermal systems used?
-Photothermal systems absorb sunlight to produce heat usually to heat water for low-temp uses like space heating/domestic hot water
-Heat harnessed by photothermal panels can be retained in thermal store for later use → usually well-insulated tank containing material like water, sand, concrete. Molten sand cake used if energy has been concentrated to produce much higher temps
Harnessing solar power; what is passive solar architecture?
-Buildings can be designed to maximise absorption of sunlight for heating w/out use of active working equipment
-Overheating in summer can be ↓ w/ fixed solar screen (rise soleil) that deflects light, adjustable screens or ventilation
Harnessing solar paper; how are heat pumps used?
-Uses change in state of fluid from liquid → gas to absorb heat from environment & releases it within building when gas condenses to liquid
-Change in state = caused by changes in pressure using compressor pump to cause gas to condense & pressure relied valve to cause liquid to boil, heat source may be atmosphere/ground
-Heat pumps absorb heat energy from ↓ energy density sources, produce↑ temps in building to be heated, heat energy released can be x4 as much energy to run heat pump but less is released if temp of heat source is lower
-NB heat pumps can harness other sources of heat like geothermal energy
Harnessing solar power; how are photovoltaic (PV) cells used?
-When PV cell absorbs photons of light, electrons → dislodged from atoms in upper layer of PV cell
-These will flow along electrical conductor from electrically negative layer to power electrical appliances
-Wide variety of improved PV cells have been developed. Some = lower efficiencies but cheaper to manufacture others= expensive may have higher efficiencies concerting light → electricity
-Many early solar PV uses were isolated uses of electricity often w/ rechargeable battery for night-time operation
-Solar farms → now used to deliver electricity for grid-connected uses
Harnessing solar power; what is the order of efficiency for different types of PV cells, highest to lowest?
Multi junction, single junction gallium arsenide, crystalline silicon, organic cells, amorphous silicon
What are the environmental impacts associated with solar energy?
-Manufacture of solar panels; requires extraction & processing of materials like metals, plastic, paints & silicon. Making PV solar panels produces toxic wastes, og silicon tetrachloride & small amounts of cadium—> can be controlled but adds to cost
-Impacts during use; don’t require much maintenance but cleaning requires water, may be scare in areas best suited to solar power. Large solar farms can occupy land that could’ve been used for other purposes but there are v large areas of urban roof space that could have panels w/ no land use conflicts. In desert areas → can make land productive but may be environmental impacts on local flora & fauna
New solar power technologies; what are the features of multi-junction photovoltaic cells?
Multiple layers made of diff materials, each of which absorbs diff wavelengths of light → greater amount of available light absorbed & converted to electricity
New solar power technologies; what are the features of anti-reflective surfaces?
-PV cells w/ smooth surfaces reflect about 30% of light hitting them
-Having a grooved/textured surface reflects light into cells rather than away from them
-Some designs mimic structure of corneas of moth eyes → v efficient at absorbing light
New solar power technologies; what are the features of Concentrating Solar Power (CSP) w/ thermal storage?
-Parabolic reflectors are used to ↑ energy density
-Light is absorbed by tubes of oil; used to heat molten salt in large insulated tanks. Salt is heated to temps up to 550°C, can be used to boil water & drive steam turbines wherever electricity is required
-This overcomes problem of solar power being intermittent
New solar power technologies; what are the features of photovoltaic/ thermal hybrid systems (PVT systems)
-Efficiency of PV cells drops at higher temps as electrical resistance ↑
-Hybrid systems absorb heat for uses like space/water heating → cools Pu cell & increases the efficiency
New solar power technologies; what are the features of transparent PV cells?
-PV cells that allow most of light through can beincorporated into windows
-Some= so transparent they look like ordinary windows / while others can be used to provide shade/reduce heating
New solar power technologies; what is the function of heliostats?
Alters angle of solar panel so is always at optimum angle for absorbing sunlight
New solar power technologies; what is a features of self-cleaning panels?
Nanohydrophopic surfaces
How is hydroelectric power (HEP) harnessed?
-The GPE of rainwater landing on upland areas can be harnessed as kinetic energy as it flows downhill
-Practical exploitation depends on large enough volume water being available & suitable topography creating ↑ water pressure/ high flow velocities
What are the locational constraints on harnessing HEP?
Ideal sites include;
-Large water catchment area
-↑ total rainfall evenly distributed throughout year
-↓ water turbidity
-Impermeable bedrock beneath reservoir
-Low seismic activity
-Suitable topography: narrow exit to large basin
-No serious land-use conflicts
-Close to consumers/ electricity grid, to ↓ transport $
What are the environmental impacts of reservoir creation for HEP?
-Dam construction requires large # of material like rock, sand, gravel, cement
-Extraction, processing, transport of materials requires energy
-Access roads may be needed
-Reservoir created by dam will flood land → loss of wildlife habitats, farmland, homes
-Reservoir provides area of static water where suspended solids & dead organic matter can produce anaerobic conditions & release of methane
-Reservoir can have positive impact on wildlife by providing new habitat for aquatic wildlife
What are the environmental impacts on the river due to HEP harnessing?
-Sedimentation in reservoir can ↓ turbidity downstream & replenishment of nutrients onto flood plain around river
-Natural flow fluctuations of river → replaced by water flow controlled by power station operators, may involve constant flow rate to produce maximum power output
-Reservoir stores surplus water when flow rate is ↓
-Some HEP stations are used to meet peaks in demand for electricity so water flow rate through dam can vary greatly
-Environmental impacts of changes in flow rate depend upon diff between natural & new flow regimes
How does HEP impact natural flow rates and what environmental impacts does this cause?
Seasonal flow extremes → constant flow; dry season sandbanks used by nesting birds/turtles are lost. Loss of periods of high flow allows sediments to build up so gravel fish spawning sites are lost. Loss of high river levels downstream stops seasonal flooding of surrounding land, may be essential for plants/breeding fish/aquatic species
Constant flow —> sudden flow increases; increased turbidity due to high flow rates makes it hard for fish-eating birds to see their food. Reduces light penetration makes photosynthesis difficult. Species that can’t resist high flow rates may be washed away
New HEP technologies; what are low-head turbines?
Some new developments allow ↑ use of low-head locations where water drops short distance
New HEP technologies - low-head turbines; what are features of waterwheels?
Are less efficient than turbines but don’t suffer from screen blockages with leaves litter → can affect turbine systems
New HEP technologies - low-head turbines; what are features of Kaplan turbines?
-Axial flow turbines w/ blades that can be rotated to allow variations in water flow
-can harness up to 90% of flowing water’s kinetic energy
New HEP technologies - low-head turbines; what are features of helical turbines?
-Similar to Archimedes’ screws used in several ancient civilizations to raise water
-Turned by water flowing down screw to generate electricity
-Have high efficiency, can use water w/ high turbidity and not get damaged
-Fish can be carried down turbine and not get damaged
New HEP technologies - low-head turbines; what are features of micro-hydro schemes?
-Small scale projects, usually used by small rural communities
-Environmental impacts of damming rivers have restricted use of HEP on many rivers; these divert part of the flow of a river to drive a turbine but don’t create a barrier across whole river
New HEP technologies; where are large HEP schemes being developed?
Many countries with expanding industrial economies like China and Brazil
How is wind power generated?
-Differences in atmospheric pressure are produced by regional differences in heating by solar energy
-Winds blow to equalise the pressure differences
How do modern and early ways of harnessing wind power differ?
-Early; harnessed kinetic energy of winds to drive machinery like grain mills & water pumps
-Modern wind turbines generate electricity - most aerogenerators have blades/vanes that rotate around axis in either vertical / horizontal plane; Vertical Axis Wind Turbine (VAWT) & Horizontal Axis Wind Turbine (HAWT)
What are the advantages and disadvantages of HAWTs?
-Adv; technology more advanced, well established, higher efficiency than VAWTs
-Disadv; stress cracking can occur at base of blades due to cyclical gravitational forces, taller towers needed to keep blades above ground, weight of generator requires stronger tower than for VAWTs where generator can be at ground level
What are the advantages and disadvantages of VAWTs?
Adv; turbines driven by wind from any direction so can be used where winds are turbulent like cities, turbines don’t need to be turned to face into wind so no need for motor, quieter than HAWTs, lower wind velocities
Disadv; no very large ones built, lower efficiencies as blades aren’t absorbing wind energy via rotation
Why does the air behind a turbine move more slowly ?
Aero generators absorb kinetic energy of moving air
Why must individual turbines be spaced out?
So they aren’t in the ‘wind shadow’ of nearest turbine
Locational constraints of wind power; why is wind velocity significant?
-Reliability & strength of winds is affected by latitude, w/ windiest areas in temperate & polar regions
-Topography of area will affect wind velocity as friction & turbulence of surface features can slow wind down
-Areas w/ often higher wind velocities = coastal areas, flat areas, upland areas, the sea
-Harnessing wind power in windiest areas is crucial as ↑ wind velocities produce much more power. x2 in velocity → x8 ↑ in kinetic energy
Locational constraints of wind power; how does isolation play a part?
-Small-scale use of wind power can provide electricity for isolated uses like small rural communities
-Large-scale wind farms may be located near existing electricity grid to avoid lost of laying new cables to join electricity grid
Locational constraints of wind power; what are some examples of land use conflicts and how can they be mitigated?
-Ecological impacts; turbines may be located away from bird migration routes, high bat populations or sensitive habitats like bogs where turbine foundations/ access trucks may affect hydrology of area
-Land requirement; turbines in wind farms require large area of land over which aerogenerators can be dispersed. To minimise ‘wind shadow’ effect they’re normally w/ interval of 3-5x diameter of blades. Land between them can still be used for things like agriculture, so area lost not as big
-telecommunication inference; aerogenerators can interfere w/ radio & radar systems
-Public opposition; some people object to wind farms as are often located away from scenic & urban areas
Environmental impacts of wind power; how is manufacture and installation problematic?
As w/ all energy resources, material manufacture & instillation have environmental impacts in production of materials & their transport + installation
Environmental impacts of wind power; how is noise an issue?
-Rotating aerogeneraters → much less noisy than other everyday anthropogenic sources of noise like roads & domestic appliances
-For people who live very close to aerogenerators, rhythmic sound may be irritating
-More aerodynamic blade designs & direct drive aerogenators w/ no gearbox = quieter
Environmental impacts of wind power; how can habitats be destroyed?
Habitat area destroyed by foundations of aerogenerators= relatively small but more habitat is required for access paths & transformers
Environmental impacts of wind power; how can bird strikes happen?
-Rotating blades of aerogenerators can kill birds—> most likely if they’re located along ridges where migrating birds soar, migration routes, where birds congregate, eg wetlands
-Careful location of them can reduce the risk of bird death
-VAWTs= less likely to cause bird death as blades seem more easily
Environmental impacts of wind power; how can bat deaths happen?
-Changes in air pressure caused by passing blades can kill bats
-They usually fly when wind speeds → low (when wind turbines generating little electricity)
-Areas w/ high risk of bat death → turbines may be stopped during periods of law wind velocity
New wind power technologies; how do blade-tip fins work?
Reduce turbulence & wind resistance → increases blade efficiency
New wind power technologies; how do nacelle brushes work?
-Reduce # of air escaping between base of blades & central nacelle (hub)
-↑ amount of kinetic energy absorbed by blades
New wind power technologies; how are direct drive turbines better than most wind turbines and how do they work?
-Most wind turbines have a gearbox to ensure generator turns at 3000rpm, produces 50 cycle per second alternating current (AC) electricity that has to be fed into national grid
-Gearbox = expensive, common cause of mechanical breakdown. Friction within gearbox ↓ efficiency,↑ wind velocity at which blades start to rotate
-Extra weight in nacelle requires tower to be stronger, requires more materials & more expensive
-Direct drive turbines don’t have a gearbox; more reliable, quieter, cheaper, start to generate electricity at ↓ wind velocities
-Generator produces DC electricity → converted to AC electricity, can be fed into electricity grid using inverter
New wind power technologies; why are helical VAWT blades more effective than straight blades?
-VAWTs w/ straight blades don’t rotate smoothly as some positions absorb more energy than others
-↓ efficiency of electricity fed into grid, can lead to strain & stress fractures
-Helical blades rotate more smoothly, avoid above problems
New wind power technologies; how have wind-assisted ships been designed?
-Intermittency of winds & difficulty of sailing against wind direction → commercial shipping is unlikely to solely use wind power
-Wind assisted ships using wind power to ↓ energy provided by ship’s engine have been designed & built using vertical aerofoil wings, mechanically controlled sails, kite-sail
-Maltese Falcon demonstrates sail rig designed for use on wind-assisted cargo ships, can be operated by single crew member
How is wave power generated?
-Friction of winds blowing over water creates waves
-Kinetic energy of vertical movement of water can be harnessed
What are the locational constraints of wave power?
Kinetic energy of waves is greatest where;
-Mean wind velocities= ↑, winds are consistent in strength & direction to allow wave height to ↑
-There’s a long fetch (distance of open water over which waves can build up)
Harnessing wave power; how do point absorbers work?
-Have floating structure which rises & falls as waves pass → attached to non-moving base located on seabed/static deep water
-Movement of floating part turns generator, eg Power Buoy
Harnessing wave power; how does a overtopping/terminator device work?
-Breaking waves force water → storage reservoir (above sea level)
-Water flows black to sea passing through turbine, generates electricity
-Sea walls may be used to ↑ height of waves & volume of water entering reservoir, eg Wave Dragon
Harnessing wave power; how does an oscillating wave surge converter work?
-As waves pass, water moves horizontally & vertically, produce cycle
-Oscillating horizontal/vertical movement pushes flat plate, moves pistons to pump fluid over turbine to generate electricity, eg Oyster
Harnessing wave power; what is a surface attenuator wave power and how does it work?
-Hinged floating device
-As waves pass, moving sections push & pull pistons which force fluid over turbine, generating electricity, eg Pelamis
Harnessing wave power; How does oscillating column wave power work?
-Rise & fall of water, as waves pass, forces water ↑&↓ in submerged chamber
-Air forced in & out flows over turbines, generating electricity, eg Islay Limpet
What are the design problems associated with wave power?
-Equipment needs to be able to withstand storms & corrosion
-Can be difficult to anchor equipment off stormy coasts/in deep water
-May be expensive to transport electricity from isolated areas; where wave energy can be harnessed to consumers
Are there any environmental impacts from wave power?
-Systems have very limited environmental impacts
-As w/ all energy systems, manufacture & instillation has impacts
-Anchoring of floating systems affects seabed but can also create new habitats
What are biofuels and what do they include?
-Where photosynthesis has recently captured sunlight, stored it in materials like vegetable oils/ carbohydrates
-Have been produced by biological processes sufficiently recently that can be renewable
-Some are deliberality produced, others are waste products of other processes & activities
-Globally more people use wood as main energy source than any other, mainly LEDCs. Newer methods are being produced to make biofuels in MEDCs
How can biofuels be harnessed?
-Wood
-Combustible crops like miscanthus, coppiced willow
-Alcohol from carbohydrate crops like sugar cane, sugar beet
-Biodiesel from vegetable oils like sunflower
What waste products can be used as biofuels?
-Methane from anaerobic digestion of wastes like sewage, crop & forestry waste & food waste
-Combustible crop waste like straw
-Incineration of combustible domestic refuse
-Landfill biogas
What are the advantages of biofuels?
-Supply rate of energy crops can be controlled, unlike most other renewable energy resources
-Can be stored until needed so easy to match supplies to demand
-Eg like vegetable oils & sugar can be used to make vehicle fuels to replace petrol/diesel
-Fuels themselves = ‘carbon neutral’, release same # of Carbon dioxide as they absorbed in photosynthesis during growth
-Energy density of alcohol & biodiesel= nearly as high as that of fossil fuels
What are disadvantages of biofuels?
-Supply of them from wastes → limited to # produced by source activity
-Large areas of farmland required for biofuel crop production may compete w/ food production/encourage clearance of wildlife habitats to create more farmland
-Energy density of straw, wood & miscanthus= lower than that of fossil fuels
-Intensive farming methods used to grow some biofuel crops may release nearly as much CO2 as using fossil fuels directly
What are the locational factors of biofuels?
-Need for fertile soil, suitable climate, topography making cultivation easy
-Biofuels coming from wastes → produced wherever source activity located, eg landfill sites & sewage works near urban areas
What are the environmental impacts of biofuels?
Biofuels produced as part of agricultural production system can cause environmental impacts via habitat loss, fertiliser & pesticide use & impacts of using fossil fuels to drive machinery
What are examples of new biofuel technologies?
-Hydrogen from algae; some types of algae produce hydrogen via photosynthesis it deprived of sulfur - can be harnessed & used as fuel
-Anaerobic digestion; being applied to range of biological materials like crop wastes & marine algae. Small scale products w/ manure/sewage becoming common LEDCs
How is geothermal power generated?
-Radioactive decay of isotopes of thorium, uranium & potassium in Earth’s mantle releases heat
-Heat may be moved → surface of crust by molten magma/hot water
-Heat may be exploited for space heating, hot water, electricity generation
Harnessing geothermal power; what are examples of low temperature schemes?
-Geothermal springs; groundwater heated by hot rocks underground may come to surface in hot springs → can be used for district heating
-Geothermal aquifers; hot groundwater may be pumped to surface from underground aquifers to be used in district heating schemes
Harnessing geothermal power; what are examples of high temperature schemes?
-Geothermal steam systems; groundwater at very high temps may be brought to surface using extraction borehole, producing high temp steam at surface that can be used to generate electricity
-Hot dry rock systems; where there are hot rocks near surface but no groundwater, 2 boreholes may be used. Water= pumped down injection borehole & steam is recovered w/ 2nd borehole. Fracturing rocks underground may ↑ permeability of rock & surface area exposed for heat absorption
What are the locational constraints of geothermal power?
-Geothermal stations using steam turbines need heat source w/ temp above 150°C
-Requires relatively recent volcanic activity so hot rocks near surface of crust
-In other areas → hot rocks are so deep that drilling down to reach them = uneconomic
What are the environmental impacts of geothermal power?
Relatively few as long as carefully developed
-Infrastructure; steam & hot water pipes can provide obstacles to movement of large mammals
-Gaseous emissions; hot water extracted from the ground can release gases like small amounts of CO2 & hydrogen sulfide
-Waste water; can contain salts & heavy metals
New geothermal technologies; how can low temperature fluids be used?
-Use liquids which boil & turn turbines at lower temps
-Water as cool as 60°C can be used to boil butane/pentane
-May allow areas w/ lower temp rocks to be used for electricity generation, including some areas in UK
How can tidal power be generated?
-Gravitational attraction between Earth & moon creates tidal flows of water producing 2 periods of high water & 2 periods of low water in each 25h cycle
-Gravitational effect of moon depends upon its position in relation to the sun which also has a gravitational effect on tides although it’s smaller
-When effects combine, there are ‘spring tides’ where tidal range is greater
-When effects work in opposition, there are ‘neap tides’ where tidal range is smaller
-In most areas of sea, speed of water flow= too slow to be harnessed but coastal features & seabed topography may focus flow, ↑ velocity of water &↑ tidal range
Harnessing tidal power; what is a tidal barrage? + evaluate
-Dam across estuary/bay where turbines are located so all water flowing in/out of lake created behind barrage flowing over turbine
-Barrage makes maximum use of tidal flow of water in & out of estuary/bay but financial costs = high, environmental impacts great
Harnessing tidal power; what are tidal lagoons and how do they work?
-Surrounds selected part of estuary/bay
Only part of area is affected, most environmentally sensitive can be avoided
-Some schemes propose multiple lagoons next to each other
-If electricity= being generated but demand= low, water can be pumped into lagoon producing water level ↑ than sea level
-Electricity can be generated later when demand → high but there’s no tidal water flow
Harnessing tidal power; how do in-stream turbines work and are they effective?
-Fixed to seabed & absorb kinetic energy of natural tidal flow
-Harness much less energy than barrage/lagoon but environmental impacts = very ↓ as don’t have any significant impact on tidal power
What are the advantages of tidal power?
-Positions of sun & moon can be predicted so times & ranges of tides= also predictable
-Tidal barrage on large estuary would have large electricity output compared w/ most other renewable energy schemes
What are the disadvantages of tidal power?
-Intermittent periods when electricity generation is possible make it difficult to meet continual demand
-Few suitable sites for construction of barrage where flow of water would produce enough electricity to be economically viable
-Environmental impacts of barrages= large compared w/ impacts of most other renewable energy schemes
What are the locational constraints of tidal power?
-Gravitational forces affect all water bodies but sites suitable for economic exploitation of tidal flows = rare
-Seawater normally moves quite slowly but coastal features like estuaries may concentrate flow, ↑ water velocity
-If tidal range= large & mass of moving water= large, harnessing tidal power may be viable
What are the environmental impacts of tidal barrages?
-Materials; large size of barrage requires v large # of material for construction: sand, gravel, rock, cement, etc. Have environmental impacts during extraction, processing, transport, installation
-Tidal range change; barrage ↓ ease w/ which water can flow in/out of lagoon so low tide level is never quite as low &↑ tide level isn’t quite as high
- Sedimentation; water flow in/out of lagoon behind barrage is in only possible via turbine channels in barrage, so there’s areas of v fast flow where sediments are eroded, carried away. In other areas w/ slower flow, sediments may be deposited & build up. Extended periods of static water at high & low tide will allow sediments to settle so general turbidity will be ↓. This’ll allow light to penetrate deeper water, ↑ temp & allowing more photosynthetic organisms to survive
-Pollutant conc; pollutants from human activities around lagoon/catchment area may build up in lagoon
What are the environmental impacts of tidal lagoons?
-Similar to barrages but un smaller scale
-As don’t involve whole estuary, there’s more opportunities to avoid impacts on most sensitive features like not creating barrier across main channel so migratory species can still pass though
What are the environmental impacts of in-stream turbines?
-Don’t block natural tidal flow so don’t have impacts of barrages/lagoons
-All tidal turbines make noise that may affect marine animals like whales
-Effect is localised but installation of large # of in-stream tidal turbines, dispersed over large area, could have ↑ impact than turbines in barrage/lagoon
Are there examples of new tidal power technologies?
-As tidal power hasn’t been widely used, there are still a large # of proposed designs yet to be tested
-Example= tidal reef; similar to barrage in crossing estuary but not as tall so water can flow over top of reef, allowing movement of fish + other marine organisms & flow of water across full with of estuary
What changes are required for society to transition from fossil fuels to renewable energy?
-New technologies to harness greater # of energy & at ↑ efficiency
-Large-scale energy storage systems
-Changes to energy transport infrastructure & vehicle designs
-Changes in technologies using energy
Why and how are secondary fuels created?
-Primary fuels comes directly from the environment but may not be in a form that’s easy to use
-It may be possible to convert it to another energy form & be used as a secondary fuel
What does the generation of electricity involve?
-Conversion of energy from a range of original primary fuels
-Forms of energy that can be converted directly to electricity =kinetic energy, chemical energy and light
-Several energy conversions may be needed to convert energy of primary fuel → energy form that can be converted to electricity
How can kinetic energy be used to make electricity?
-Spinning electrical conductor within magnetic field in generator
Kinetic energy may be harnessed directly as w/ wind/water power, or it may be produced by converting other types of available energy like heat
-In conventional power stations, heat is used to boil water then movement of ↑ pressure expanding steam is used to spin turbines which spin generators
What are the different functions of the main nuclear power station features?
-Nuclear reactor; heat generated by nuclear fission is used to heat primary coolant (pressurised water)
-Control rods;absorb neutrons. Lowered into reactor/raised out of it to control power output
-Boiler; Hot primary coolant heats water, boils to produce ↑ pressure steam
-Steam turbines; kinetic energy of ↑ pressure steam is absorbed & spins turbines
Generator; rotating turbines turn generator, produces electricity
-Condenser; steam which has cooled & lost its pressure is condensed using cold water from a river, lake, sea. Condensed steam is reused in boiler
How can electricity be generated from light energy via photovoltaic cells?
-Photons of light striking surface of PV cell displace electrons making surface layer negatively charged
-The free elections can flow along conductor to lower layer (relatively positively charged)
-Moving electrons can be used to power electrical appliances
How can chemical energy be converted to electricity?
-In reactions where 1 chemical accepts electrons at electrode & another chemical releases electrons -at another electrode
Electrons flowing between electrodes can be used to power electrical equipment
How can electrochemical cells be used to create electricity?
-Electrochemical cells are used in batteries to store chemical energy, can be converted to electricity
-When chemical reactions take place, battery loses ability to produce more electricity
-Rechargeable batteries use electricity to reform chemicals producing electricity
How are fuel cells used to generate electricity?
-Fuel cells use electrochemical cells to store energy in chemicals like hydrogen & alcohol
-They won’t lose their ability to produce electricity us long as fresh supply of fuel is available for chem reactions
-Use hydrocarbons, alcohols, hydrogen & oxygen
-Simplest type of cell uses hydrogen & oxygen as fuel
-Hydrogen releases electrons while oxygen accepts them, resulting ions combine to create water
What are the advantages and disadvantages of using electricity?
-Advantages; no pollution caused when used, converting electricity to other energy forms like sound is straightforward, transportation is easy via conducting cables
-Disadvantages; converting primary fuel to electricity isn’t very efficient, storing is difficult as there’s no large scale options available, initial production may be highly polluting
How is electricity often transported? + evaluate
-Locations where electricity can be generated= often geographically limited so may be necessary to transport it using grid of electrical cables
-Laying cables underground → expensive, cables need to be cooled (requires energy for pumping coolant fluid)
-Overhead cables can cause aesthetic issues in scenic areas & birds may be killed if collide w/ cables
What is hydrogen and what does it enable?
-Reactive gas, can be produced by electrolysis of water using electricity from surplus primary energy sources
-Enables unreliable/intermittent energy supplies to be efficiently used by converting → form of energy that can be stored
What are the main uses of hydrogen?
Used to release chemical energy from stored hydrogen
-Combustion to produce heat; then used to heat buildings, water & industrial processes/boil water, create steam to drive turbines & generate electricity
-Fuel cells; electrochemical process, combines oxygen & hydrogen to make water thereby releasing energy
Forms of hydrogen storage; what is the process and disadvantage of compressed gas storage?
Process; compressor pumps up to 700 x normal volume → storage tanks
Disadvantage; energy required to run compressor
Forms of hydrogen storage; what is the process and disadvantage of liquid storage?
Process; liquefied under ↑ pressure at very ↓ temp
Disadvantage; energy required for refrigeration & to run compressor
Forms of hydrogen storage; what is the process and disadvantage of metal hydride systems?
Process; hydrogen absorbed onto surface of metal matrix enabling ↓ pressure hydrogen storage
Disadvantage; storage tanks = larger & heavier than petrol tank that stores same # of energy
Forms of hydrogen storage; what is the process and disadvantage of ammonia storage?
Process; surplus primary energy used to produce ammonia (NH3)
Disadvantage; some energy requires but much less than alternatives as process doesn’t require such ↑ pressures/low temps
What is the ‘hydrogen economy’ and what does it enable?
-Hydrogen storage enables communities to be fueled renewable from an abundant, convenient energy
-Current energy supplies would continue to be used to satisfy current demand; hydrogen would be used to store any surplus energy
-Energy would continue to be stored until needed to meet increase in demand/supply shortage due to unreliable/intermittent supplies
-Stored hydrogen would be used directly to power heating & vehicles/in steam-turbine power stations/fuel cells to generate electricity
-Development of hydrogen economy doesn’t require hydrogen to be main energy source actually used by consumers
-Primary fuels like biofuels can be stored, only used when available and in demand → energy losses created during energy conversions, if all primary energy had been used to make hydrogen, would be ↓
-Unlike many energy resources, hydrogen has a ↑ energy density so could replace fossil fuels for many uses like powering vehicles
What does energy storage enable?
-Large # of fuel can be accumulated for more economic transportation
-Energy production rates can be kept constant for most economic use of equipment & workers like coalmines
-Any surplus energy from intermittent supplies can be stored until it’s required, eg wind/solar power. This is called peak shaving
What are the causes of fluctuations in energy supply?
-Use of intermittent energy resources like solar, tidal, wind
-Bulk delivery of transported energy resources, eg oil, coal, biofuels
What are the causes of fluctuations in energy demand?
-Short-term weather-related fluctuations
-Seasonal fluctuations
-Weekday/weekend fluctuations in industrial use
-24hr day/night fluctuations
-Short-term behaviour-related fluctuations: mealtimes, TV ‘pickup’
Why can there be a surplus of electricity generated but a large scale storage of electricity isn’t yet possible?
-Base-load power stations generating electricity 24h/day even though much less electricity is needed during the night as its uneconomic to turn power stations on/off
-Fluctuations in demand like after meals/ TV breaks, lower industrial demand outside core working hours. Demand for electricity may drop more rapidly than power station output can be ↓
-If generated electricity is unused then it’s lost through heat from cables
Developments in energy storage technologies; how does peak shaving using pumped-storage HEP work?
-Surplus electricity used to pump water uphill, stores energy as GPE
-Potential energy converted → kinetic energy through water flowing to lower reservoir, turning turbines & generating electricity to meet peaks in demand
-So pumped-storage HEP stations can be more responsive to changes in demand than stations powered by coal, gas, nuclear fuel
-Can go from standby → full power in >15s so can meet sudden ↑ in demand
Developments in energy storage technologies; what are ways for chemical energy to be stored?
-Stored fossil fuels, biofuels, hydrogen store chemical energy
-Batteries & fuel cells can be used to store chemical energy
-Rechargeable batteries enable original chemicals to be reformed w/ electricity so batteries can be reused
-However for fuel cells to continue to operate new fuel & oxidant chemicals must be supplied
What are the factors affecting rechargeable battery viability?
-Efficiency of storage cycle; % of electricity used in recharging that’s available later
-# of charge-discharge cycles that can be carried out
-Energy density
-Cost per unit of energy stored
-Recharging speed
-Self-discharge during periods of non-use
-Safety issues: toxicity, fire risk
Developments in energy storage technologies; how do compressed gas systems work?
-Surplus energy can be used to drive pump compressing air → can be released later to power machinery. Method has been used on a small scale since 1870
-Current research focuses on large-scale systems which could produce 200MW + of power from compressed air stored in underground caverns like salt minestrone
-Compressing air produces a lot of heat. May also be stored, like in hot oil/molten salt thermal storage
-Compressed air system w/ heat storage can recover 90%+ of OG energy
Types of storage systems; how do Vehicle to Grid (V2G) systems work?
-Energy can be transferred between national electricity grid & vehicle batteries
-Batteries of road vehicles represent big source of energy for electricity grid if other sources can’t provide enough energy to meet demands
-Proposal= all vehicles are plugged into grid when they’re parked for long periods
-If there’s a peak in demand for electricity then small proportion of energy from vehicle batteries may be used → avoids cost & environmental impacts of using rapid-response, low-efficiency, high-cost power stations like open-cycle gas turbines
-Surplus energy from grid can be used to recharge vehicle batteries
Types of storage systems; how do Power to Gas (P2G) systems work?
-Surplus electricity to produce gaseous fuel which can be stored
-Water is electrolysed to produce hydrogen → can be used to produce methane that can be used into natural gas pipe network
Types of storage systems; how do heat energy storage systems work?
-Heat energy is unavoidably lost from hot materials by conduction, convection & radiation so long-term storage of heat energy is difficult
-Short-term storage of thermal energy can be efficient, especially if few energy conversions are involved
-Thermal storage systems include use of molten salt, high volume not water stores & use of high thermal mass materials
-Material used for heat store should have a high specific heat capacity so greatest possible # of heat energy can be stored in given volume. Such materials are said to have a high thermal mass
Types of storage systems; how do high volume storage systems work?
-As volume of heat store ↑, SA:V ratio ↓so rate of heat loss falls as there’s a smaller SA for each unit of storage volume
-Very large heat stores can be used for inter-season energy storage, like absorbing surplus solar energy from summer for heating buildings in winter
Types of storage systems; how do molten salt systems work?
-Has advantages over water for thermal storage is high temps are required
-Potassium nitrate → much higher BP than water, so is used at temps up to 550°C to store heat from CSP photothermal systems
-Heat can be used later to boil water in steam-turbine power station & generate electricity when needed
-Hot water storage system could only reach such temps if kept under pressure which would ↑costs
Types of storage systems; How do high thermal mass building material systems work?
-Buildings constructed of materials w/ high specific heat capacity like concrete, warm up & cool down comparatively slowly
-↓ overheating during hot weather so ↓ need for air conditioning
Also ↓ need for heating at beginning of cold weather as building materials will keep building warm for some time
Types of storage systems; how do kinetic energy storage systems work?
-Flywheels can be used as temporary store of kinetic energy
-Rotating flywheel can be used to drive machinery/ generate electricity when needed
Types of storage systems; how do electricity supercapacitor systems work?
-Early capacitor designs store electricity as electrical charge on flat plates of conducting materials, separated by insulator
-New ‘super capacitors’ use electrochemical process & have energy density 10-100x↑
-In future, may be possible to use supercapacitors for large-scale storage of electricity
How is energy conserved and how is efficiency measured?
-↑ efficiency of energy use & avoiding wastage of unnecessary use
-Means # of energy needed for task is ↓
-Efficiency is measured by proportion of energy actually achieving desired activity
-Energy used for tasks thought to be unnecessary can be seen as wastage
-Its important to distinguish between low efficiency & wastage
How is transport significant energy wise and how has it developed?
-Transport uses most energy of all activities
-W/ society developing more affluence, they’ve been able to travel more, afford global goods, eat foods transported long distances
-Transport systems have became faster, more convenient & carry large numbers of peoples/quantities of goods
-Transport infrastructure & larger transport forms → enabled industries to develop in wider range of places away from sources of raw materials like metal ores, limestone, coal
What factors determine type of transport used?
-Carrying ↑ loads on fewer vehicles = more energy efficient than using ↑ # of small ones
-Flexibility of routes & destinations, eg inconvenience of public transport compared to door to door transport
-Need for rapid transport of goods like perishable foods
-Level of fuel tax
Vehicle design; How do aerodynamics/hydrodynamics influence energy conservation?
↓ friction as vehicle moves through air/water ↓ amount of energy needed to propel it
Vehicle design; how do regenerative braking/kinetic energy recovery systems (KERS) influence energy conservation?
-To slow vehicle → kinetic energy needs to be converted to other form
-Conventional braking systems use friction brakes to convert kinetic energy to heat, lost to atmosphere
-More fuel must then be used to accelerate vehicle again
-Regenerative braking systems convert kinetic energy to form that can be used/stored rather than being wasted
-Road vehicles use generator to convert kinetic energy—> electricity, stored as chem energy in battery. Can be used to produce electricity propelling vehicle using electric motor
-Some railway locomotives also use generator to slow train but electricity produced is fed back into national grid
Vehicle design; how does reduced mass influence energy conservation and how can this be done?
↓ weight of vehicle will ↓ fuel consumption, eg of how this can be done;
-Plastics used in cars instead of metals where strength = less important. Composition materials like carbon fibres can be used & have ↑ strength: weight ratio than metals
-Steel alloys w/ carbon, titanium & vanadium create ↑ strength steel so thinner, lighter body panels can be used
-Lighter neodymium speaker magnets can replace ferrite ones
-Replacing cast iron engine blocks w/ lighter aluminium ones
-Redesigning wiring routes so shorter cables used & wiring is lighter
-Using ↑ energy density batteries which have ↓ mass per unit of stored energy
Vehicle design; how does reduced mass influence energy conservation and how can this be done?
↓ weight of vehicle will ↓ fuel consumption, eg of how this can be done;
-Plastics used in cars instead of metals where strength = less important. Composition materials like carbon fibres can be used & have ↑ strength: weight ratio than metals
-Steel alloys w/ carbon, titanium & vanadium create ↑ strength steel so thinner, lighter body panels can be used
-Lighter neodymium speaker magnets can replace ferrite ones
-Replacing cast iron engine blocks w/ lighter aluminium ones
-Redesigning wiring routes so shorter cables used & wiring is lighter
-Using ↑ energy density batteries which have ↓ mass per unit of stored energy
Vehicle design; how does wheel design influence energy conservation?
-As air-filled/’pneumatic’ tyres rotate, weight of vehicle squashes tyre, changing its shape
-When vehicle moves frictional heat is created by continual change in tyre shape & movement of air inside tyre
-Underinflated tyres lose even more energy. Less energy lost by using solid wheels but these give bumpy ride unless vehicles using them run on rails like trams & trains
Vehicle design; how does fuel combustion efficiency influence energy conservation and how can this be improved?
-Internal combustion engines → not able to burn 100% of fuel they use
-If combustion can become more efficient, less fuel is wasted
Combustion efficiency can be improved via;
-Efficient exhaust gas removal: having more valves per cylinder ensures waste combustion gases removed more completely so don’t mix w/ new fuel
-Better engine temp control, eg using thermostatically operated fan only operating when engine temp = ↑optimum
-Ignition control & servicing: timing of ignition spark in petrol engines= important to burn fuel efficiently so it’s critical to ensure engine ignition timing is always correct, eg via electronic ignition control
Vehicle design; what are the ways vehicles have been designed for end of life?
-Traditional vehicle design focuses on ease of manufacture of components & their assembly to create vehicle
-Newer concept → design vehicles to minimise environmental impacts of disposal of vehicles when they’re scrapped. Includes several principles;
-Use of recyclable materials where possible
-Easy identification of components & composition-eg by being stamped w/ code numbers to identify their composition
-Easy dismantling & separation of components
-Use of reusable components for use in new vehicles
-Use of compostable materials for components that can’t be receded
How is embodied energy significant and how can this be reduced?
-A significant #of the energy used by a vehicle during its life is in its embodied energy. For a typical car, this is equivalent to its fuel consumption for 1 1/2 years
-If car is made w/ recycled materials, its embodied energy will be ↓
How does mode of vehicle affect its efficiency and how can this be improved?
-How a vehicle is driven often affects fuel efficiency
-When vehicle travels slowly a lot of energy is used to run engine rather than more vehicle. When it travels fast, energy is wasted via overcoming air resistance. Thus, there’s an optimum speed for efficient energy use which for many cars= 56mph
-If vehicle → unable to travel at its optimum speed, eg due to traffic congestion, fuel will be wasted
-So, automatic stop/start systems that encourage free traffic flow will ↑ energy efficiency
-Driving smoothly, in higher gear & avoiding sudden breaking + acceleration will improve fuel efficiency
What are examples of transport infrastructure and management systems that increase energy efficiency/conservation?
-Integrated transport systems road/rail/cycle; most energy efficient method of transport isn’t necessarily same for whole length of journey but is often inconvenient to change vehicle during journey. Park + ride schemes/facilities to carry bicycles on trains help
-Active Traffic Management (ATM)/‘Smart motorways’; variable speed limits can be used to prevent serious congestion causing delay, wastes energy
-Driverless cars; development may result in smoother traffic flow + ↓fuel consumption
Building energy conservation; how does building design influence energy efficiency and how can conservation be improved?
-Orientation; energy losses= generally greater through windows than walls but solar gains through window depend upon its orientation in relation to sunlight. Use of room may affect area of windows needed & room temp. Northern hemisphere—> passive solar gains through window are greatest via south-facing windows, while losses are greatest in north side of building. Choice of position of diff room types can ↓overall energy use. Rooms needing to be warmer may be placed in side of building w/ greatest passive solar gains
-Building S.A; shape of building & whether neighbouring buildings are joined affects S.A via which heat can be lost. Buildings w/ ↓S.A:V ratio will lose heat easily
Building energy conservation; how does choice of materials affect energy efficiency and how can conservation be increased?
-High thermal mass materials; temp management in buildings can involve resisting times of over-heating & times of low temp. Using materials w/ high thermal mass can help ↓ temp extremes → can absorb heat to ↓ over-heating/emit heat to ↓ heating requirements
-Low embodied energy materials; many buildings need large # of cement for mortar + concrete. Manufacture of cement needs a lot of energy so buildings using it have ↑embodied energy. Alternative materials w/ ↓embodies energy values are available; limecrete, rammed earth
-Earth sheltered buildings; in cold weather, ground is usually warmer than air & flow of air over building ↑heat losses. Sinking some of building into ground can ↓heat losses
How is building insulation significant in energy efficiency and how can conservation be improved?
-Space heating= biggest domestic use of energy
-Building w/ constant internal temp has dynamic equilibrium where heat inputs equal heat losses. If heat losses can be ↓ then inputs can also be
-Range of energy conservation methods have been used for many years to conserve heat energy
What are examples of heat conservation methods?
-Low thermal conductivity methods; insulating materials in roof, walls floor, eg mineral wool, polystyrene, wood, shredded paper. Static air betw glass panels in double glazing= poor thermal conductor. Curtains & internal window shutters ↓contact betw war, internal air w/ window glass
-Reduction of convection of warm air against cold external surfaces; double glazing creates layer of static air too narrow for convection to occur
-↓ radiation losses; reflective foil layer on panels of insulating materials
-↓ loss of warm air; drought proofing seals around doors & opening windows
What factors affect the rate of heat loss from a building?
-Temp gradient; diff in temp betw inside & outside of building
-Thermal conductivity/resistance of materials forming external walls, windows, roof
-Loss of warm air from inside
-Chilling effect due to wind & rain
How have insulating materials been improved?
-Most insulating materials ↓ conduction by trapping airspaces in a porous structure
-Most effective systems often have prefabricated boards w/ reflective foil layer to reflect infrared radiation
-Some insulating materials have ↓ environmental impacts as are manufactured from waste like recycled paper, straw, wool
How can window energy be conserved?
-Multiple layers of glass w/ spaces betw them ↓ energy loss through windows
-Gap should be as large as possible but not so large that convection current can start → optimum gap depends on gas used to fill gap & area of window
Building insulation; what are examples of ventilation?
-Heat recovery during ventilation; heat exchangers can be used for ventilation w/ minimal heat losses. Heat of air leaving building is passed to air coming in. Counter-current flow of stale & fresh air in heat exchanger ensures efficient heat transfer
-Automatic ventilation; large glazed areas ↑ passive solar gains → may be excessive during v sunny weather. Over-heating can be ↓ using thermostatically operated automatic screens -self-operating
Energy management technologies; how do occupancy sensors work?
Work in similar way to most burglar alarms: detect sources of infrared energy & movement, but are different as turn appliance off if can’t detect occupants in room
Energy management technologies; how are programmable thermostats beneficial?
-Temp required in room can vary at diff times of day & on diff days of week
-Changes may vary betw diff rooms in building
-Having programmable thermostats makes it easier to adjust heating of large # of rooms & avoid energy wastage by unnecessary heating
Energy management techniques; how can water heating manage energy?
-Heat loss from hot water is ↓ if is heated as is supplied/as soon beforehand as possible
-If hot water must be stored then well-insulated tank should be used
-↓ vol of hot water used will save energy; can be done by showering instead of bathing, using water-saving washing machine/dish washer & using eco-cycle programmes designed to use ↓ heated water
What are examples appliance energy use being reduced?
-Lightbulbs; CFL lamps replaced w/ LED lights
-Washing machine; low energy by faster spin cycles & cold, low temp wash cycles
-Dish washer; never use less water so less heating used
-Cooker; modern have double/triple glazed door windows so ↓ heat losses
-Refrigerator; low-energy fridges have more efficient compressor, eg linear compressor
-TV/computer monitor; plasma screens use 25% electricity of cathodes they replaced, LED screens use about 50% electricity of plasma screens
-Electronic appliances; new materials in transistors ↓energy age
What are ways in which human behaviour can promote energy management?
In developed & affluent societies, relatively ↓ $ of energy enables use of energy on unnecessary items & activities. Energy wastages can be ↓ by;
-Turning lights off when not required
-Turning thermostats ↓ to prevent unnecessary over-heating
-Turning appliances off
-Only heating water that’s needed
Industrial energy conservation; how is heat recovery carried out and how can heat exchange be more efficient?
-Industrial waste in liquid & gaseous forms is often hot
-Heat energy can be recovered via heat exchangers & transferred to incoming cold gas/liquid. Heat exchangers pass hot & cold liquids through container. They don’t mix as one liquid is carried in pipes
-↑ efficiency of heat exchange can be achieved via better design like SA for heat exchange ↑ via long narrow pipes, pipes made of good thermal conductor like copper and hot & cold flowing fluids in opposite directions
Industrial energy conservation; how can energy be conserved in insulation?
-# of heat energy required to keep materials warm is = to # of heat lost
-By ↓ rate of heat loss there will be an identical reduction in heat inputs required
-As w/ domestic insulation, heat loss can be ↓ by using outer layer made of material w/↓ thermal conductivity/ ↑ thermal resistance
-Insulating pipes, storage tanks & furnaces can save a lot of energy
Industrial energy conservation; how can high volume storage be made more efficient?
-S.A= important factor affecting heat loss
-↓ S.A by using large tank rather than multiple small tanks to store hot fluid will ↓ heat loss
-S.A & resulting heat loss can also be ↓ by changing shape of tank/container, eg sphere has smallest S.A for any vol
Industrial energy conservation; how do Combined Heat and Power (CHP) stations conserve energy?
-CHP power stations recover much of heat loss in electricity generation & uses it for space heating in buildings, eg homes, fish farms, greenhouses
-Maximum efficiency of modern thermal power station, at converting energy of combustible/nuclear fuel into electricity using steam turbines → about 40%
-Remaining 60% is lost as waste heat energy, mainly via cooling water used to condense steam, via cooling towers or into river/lake/sea
-In many CHP stations efficiency of electricity generation is deliberately kept ↓ 40% this ↑ temp of hot water, ↑ its usefulness
Industrial energy conservation; how is energy conserved through intergraded manufacture?
Energy can be saved when material manufacturing processes = located on same site. Saving can be achieved by;
-Waste heat from 1 industry used by another, eg in Kalundborg
-Integrating processes, eg iron & steeI: process of converting iron → steel requires impure iron to be molten so in integrated works the molten iron from blast furnaces is directly converted to steel w/out letting it cool first. -This saves energy that would’ve been used to heat it up & re-melt it
-↓ every that would be used to transport materials betw sites by locating inter-dependent industries near each other
Industrial energy conservation; how can recycling conserve energy and why is it not always energy efficient?
-Can ↓ energy use as producing new products from used materials often uses less energy than making them from fresh raw materials
-While more energy is used producing bottle from glass than producing it from plastic, a glass bottle can be refilled/recycled. If glass bottles are reused enough then total energy is ↓
-Recycling isn’t always energy efficient as there can be economies of scale via mass production & large scale mining when manufacturing items from new raw materials
-Recycling can involve ↑energy use from transport & processing of ↓# of material
Industrial energy conservation; what is mass reduction and how can it conserve energy?
-If product can be redesigned to make it lighter then less energy will be used in its manufacture & transport. Modern glass milk bottles weigh 1/2 as much as early designs
-Plastic bottles & cardboard cartons= lighter than glass bottles but can’t be washed & reused → recycling them takes more energy than washing but their lighter weight may save more energy in transport than is used in repelling if their use involves being transported long distances
Electricity infrastructure management; what does peak shaving/pumped storage HEP involve?
Storage of surplus energy so can be used later to meet demand if other supplies ↓/to meet peak in demand
Electricity infrastructure management; how do high voltage grids work?
-Resistance to flow of electricity in cable causes loss of electrical energy as is converted → heat which is lost from cable. Loss of energy is related to # of electricity flowing (current) rather than its ‘pressure’ (PD/voltage)
-Electric power is the product of current & voltage—> power (watts)= current (amps) x potential diff (volts)
-Electricity grids use transformers to control current & voltage of electricity distributed in grid to minimise energy losses
-National grid transports electricity at v high volt so current can be reduced to minimise energy loss, while maintaining power delivered
Electricity infrastructure management; how does IT management of electricity supplies work?
-IT systems make it possible to accurately predict demand for electricity & monitor + adjust electricity supplies quickly
-This reduces waste of energy due to generating electricity for which there was no demand
Electricity infrastructure management; how will the location of new generation capacity and distribution infrastructure change?
Electricity generation equipment used in future may be in new locations, eg offshore wind farms rather than power stations on coalfields—> will require construction of new grid infrastructure
