Energy Flashcards
What are planetary boundaries?
Boundaries in which humans can survive and support future generations
Name one planetary boundary which has been exceeded and the problems
Biogeochemical flows- phosphate and nitrogen.
Problem because they help to make soils fertile producing crops for a growing population, phosphates arent renewable.
Phosphates and nitrogen also cause eutrophication.
Explain primary oil recovery
20% of oil is extracted, method uses the pressure of water below the gas/oil to force it up towards the well for collecting
Explain secondary oil recovery
40% of oil is extracted, method pumps oil or natural gas down an injection well to maintain pressure and flow of oil.
Explain tertiary oil recovery
60% of oil is extracted, this method reduces the viscosity of oil by pumping steam down an injection to heat oil and adding detergents to reduce surface tension and allow easier flow.
What is tertiary oil recovery also known as?
Enhanced oil recovery
What is the other method used in tertiary oil recovery?
Bacteria can be added to digest the heavier hydrocarbons, leaving lighter more viscous oils, the CO2 produced in respiration of bacteria maintains the pressure
What is directional drilling?
A drill which allows many wells to be produced from one hole
What are the advantages of directional drilling?
Allows drilling under areas where drilling rigs could not be built, like urban areas
A higher oil recovery rate because the drills can follow soft rock which allows faster drilling
What are Tar sands?
Heavy low viscosity oils
What are oil shales?
Solid hydocarbons
Explain the method to extract tar sands
Sand is heated with hot water, this produces emulsions of oil droplets which can be separated and collected.
Has a 75% recovery
Explain how oil shales are extracted
Oil shales are mined then the oil is extracted by heating the shales to drain off the liquid hydrocarbons.
What is CCS?
Carbon capture and storage, a method of storing CO2 from fossil fuels by pumping it underground into empty spaces
how does hydraulic fracking work?
Uses high pressure to open fissures in the surrounding rock which allows oil/gas to flow towards recovery well. Water, sand or solvents can be added to increase recovery rate.
When is hydraulic fracking used?
Used on tight oil or gas.
What is tight oil/gas?
Oil/gas that is trapped in pores of rocks with low permeability
What are the concerns with hydraulic fracking?
Natural gas entering aquifers
Chemicals entering aquifers
Toxic metals becoming mobile
large volumes of water are used
earthquakes more common due to tension
What is coal gasification?
Coal too deep to be mined is burnt underground. This produces a mixture of fuel gases, like methane, hydrogen and carbon monoxide
What is coal liquefaction?
The conversion of coal to liquid hydrocarbons.
Coal can be converted directly with solvents or indirectly by conversion to gas then it can undergo chemical changes to a liquid
What are methane hydrates?
Solid, ice-like crystals found in cold regions or high pressure regions
What are the potential methods of excavating methane hydrates?
Water heating
Depressurisation
Co2 injection
What is water heating?
Hot water is pumped into sediments to melt the hydrate crystals which release methane
What is depressurisation?
Drilling into hydrates to decrease the pressure, this allows the methane to gradually dissociate
What is CO2 injection?
At high pressures Co2 forms stronger bonds with ice crystals so methane becomes displaced and is released. This method can also be used as CCS
Why is methane hydrates not the best?
Any uncollected methane will contribute to global warming
What is fission?
The spiltting of nuclei of uranium-233 and plutonium-239.
Produces large amounts of energy
Why are nuclear reactors used as base load electricity?
Because they have a constant large power output
What are the problems with nuclear fission?
Non-renewable resource
Uranium is expensive to extract and is rare
High tech so not available everywhere
Expensive technology
Public opposition due to accidents like chernobyl
Uncertainty over disposal of radioactive waste
What are the advantages of nuclear energy?
High energy density
Can generate electricity
Uranium generators last longer, use less fuel and are reliable
What are the environmental impacts of nuclear power stations?
Habitat loss, hazardous wastes, noise and dust pollution
Ionising radiation which cause health risks in potential accidents
What are the improved uranium extraction methods?
Polymer adsorption
Phosphate mining
coal ash- uranium can be collected from it
How is polymer adsorption used to extract uranium?
Uranium dissolved in seawater adsorbs onto certain polymers, the uranium can be washed off with acid and collected
How is phosphate mining used to extract uranium?
Uranium is often found in phosphate deposits, it can be separated then collected
What is a breeder reactor?
A reactor used to convert the fertile fuel into fissile fuel
What is a fissile fuel?
A fuel that releases energy when bombarded with neutrons
How do you get the fissile fuel plutonium-239?
Uranium-238 is usually found but it is not fissile so has to be converted. The fertile fuel uranium-238 is converted to plutonium-239 by neutron bombardment.
What is a fertile fuel?
A fuel that has to be converted to a fissile fuel because it does not release energy when bombarded with neutrons.
Uranium-233 and Thorium-232
What is a fast reactor?
A reactor which is used when the fissile fuel does not need neutrons to be slowed down during neutron bombardment.
What happens in a thorium reactor?
Thorium-232 is a fertile fuel so has to be converted by neutron bombardment to the fissile fuel uranium-233.
What is thorium-232 converted to?
Uranium-233
What is uranium-238 converted to?
Plutonium-239
Advantages of thorium reactors?
Thorium is more common
less radioactive waste
radioactive waste has a shorter half life
Disadvantages of thorium-232 reactors?
Conversion to uranium-233 is slow
Uranium-233 releases alpha radiation
Expensive
What is nuclear fusion?
The joining of nuclei of small atoms, like hydrogen
Whats a toroidal reactor?
Example: ITER reactor, still in development.
-Releases more energy than used
-maintains fusion for longer
-produces tritium fuel from lithium
What is laser fusion?
small scale fusion that avoids plasma contamination and refueling which happens in torus reactors.
-Small spheres of frozen deuterium and small trituim dropped into laser to initiate fusion.
What does Hiper stand for?
High power laser energy research
Why is oil/molten salt used?
It stores heat and can be converted to energy when needed
Describe some problems with solar panels
Not constant because sunlight varies/smoke/dust/clouds
Low energy density
Location constraints
What are the environmental impacts of solar panels?
Making PV solar panels produces toxic wastes like silicon tetrachloride + cadmium
Cleaning solar panels uses alot of water
Conflicting land use with agriculture/providing food
What is cadmium?
A heavy metal
What is a multi junction cell and how does it increase effiency?
It’s layers of different materials which absorb different wavelengths of light which allows more sunlight to be absorbed.
What are anti-reflective surfaces and how do they increase effiency?
Grooved/textured surfaces which reflects the light into the cells so more light is absorbed.
What is CSP?
Concentrating solar power
How is Concentrating solar power used?
Parabolic reflectors are used to increase energy density. The light is absorbed by tubes of oil which are used to heat molten salt. This salt is heated to 550 and can be used as electricity when needed.
Why is molten salt used?
Its used to store heat because it has a high SHC
What is photothermal solar power?
Where sunlight is absorbed by solar panels and is used for domestic use like heating water.
What is passive solar power?
The absorption of sunlight without equipment, e.g. sunlight warming a house via window
What is photovoltaic (PV) solar power?
When a pv cell absorbs photons of light, electrons get dislodged and they flow to the lower positive layer. This flow provides an electric current to power appliances.
What are heat pumps?
They use the change in state of a liquid to a gas to absorb heat and releases it when the gas condenses to a liquid.
How do the state changes happen in heat pumps?
Caused by changes in pressure using a compressor pump.
What is a heliostat?
A mechanism that changes the angle of a solar panel so that it is always at the optimum angle for sunlight absorption.
Describe some problems with HEP
Locational constraints- large catchment area, impermeable bedrock, low seismic activity, no land use conflicts.
Reservoir creation- floods previous habitat, reduces flow of river downstream, the water is static so any DOM will decompose and create anaerobic conditions releasing methane gas.
Creates a barrier for wildlife, isolating populations
What are low head turbines?
Turbines which can be used in low water levels
What are helical turbines?
Turbines that are turned by water flowing down the screw to create electricity.
High efficiency and can be used with high turbidity water.
Fish can be carried down the turbine without being harmed.
What does VAWT stand for?
Vertical axis wind turbine
What does HAWT stand for?
Horizontal axis wind turbine
What are the advantages of VAWT?
Quieter than HAWT
No motor is needed to turn the turbine because they are driven by wind in any direction
They can operate in low wind velocities
What are the advantages of HAWT?
Technology is more advanced
High efficiency than VAWT
What are the disadvantages of VAWT?
Bats fly in low wind and VAWT still operate in low winds so it can harm bats.
Lower efficiency
What are the disadvantages of HAWT?
Stress cracking can occur at the base of blades due to gravitational forces.
Taller towers are needed to keep blades above ground
What is a kaplan turbine?
A type of turbine whose head can be lowered into water when there is low flow
Why is investing in HAWT and VAWTs best for sustainability?
Because HAWTs are more efficient but they cannot work at low wind velocities like VAWTs
Where can wind power be used in transport?
In shipping to reduce energy used by engines.
By trains in the netherlands
What are Helical VAWT blades?
Helical blades which rotate more smoothly, reduce the risk of strain and stress fractures which overall increasing the efficiency compared to straight blades
What are the locational constraints of wind power?
Wind velocity needs to be constant so upland areas, coastal areas and flat areas are best
Location- has to be near to electricity grid to avoid costs of new cables
Ecological impacts- need to be located away from bird migration routes etc
Land requirement- Wind farms can be used in agriculture to prevent land loss
Public opposition- very common so need to be away from urbanisation
What are wind assisted ships?
Ships that use wind power to reduce the energy used by the engine, they have kite sails or mechanically controlled sails to capture the wind.
Maltese falcon is an example
What are blade tip fins?
Fins which are bent at the tip they reduce turbulence and wind resistance which makes turbines more efficient
What are the environmental impacts of wind turbines?
Noise pollution for those who live close
Manufacture and installation uses mineral resources and energy etc
Habitats destroyed by the foundations of aerogenerators is small but large amounts destroyed for access paths
Bird strikes and bat deaths- Rotating blades kill birds, the changes in pressure caused by blades can kill bats as they fly in low velocities.
What are the locational constraints to wave power?
Area needs to have high wind velocities so that waves are constantly being produced.
A long fetch so that waves can build up
How does a point absorber work?
They are a floating structure containing a generator which is attached to a non moving base on the seabed they rises and fall as a wave passes. The movement of this floating structure turns the generator producing energy.
e.g. power bouy
How does a overtopping/terminator device work?
Breaking waves force water into a storage reservoir, the water flows back into the sea after passing a turbine which generates electricity.
e.g. wave dragon
What can be used to make more water go into a terminator device?
Sea walls that will increase the height of waves and therefore the volume of water that enters
How does a oscillating wave surge convertor work?
As waves pass water move horizontally and vertically producing a cycle, the movements push a flat plate which in turn moves pistons to pump water over a turbine producing electricity.
How does surface attenuator wave power work?
A hinged floating device in which when waves pass sections move pushing and pulling pistons which force water over a turbine producing electricity
How does oscillating water column wave power work?
As waves pass the rise and fall of water will force water up and down a chamber. The air that is forced in and out flows over turbines generating electricity.
e.g. limpet
What are some design problems with wave power machines?
The equipment has to be able to withstand storms and corrosion
It can be difficult to build in deep water/stormy coasts
Expensive to transport electricity from isolated areas
What are the environmental impacts of wave power?
Manufacture and installation using alot of energy and exploiting materials
Anchoring of floating systems will damage the seabed but it can create new habitats, this is FAD/fishing aggregation device.
What are some products that can be used for biofuels?
Elephant grass
Wood
Vegetable oils
Incineration which produces methane
Sugar cane
What are some advantages of biofuels?
Supply can be controlled
They can be stored until energy is needed
Carbon neutral because they release the same amount of CO2 they absorbed in photosynthesis.
Alcohol and biodiesels have high energy density
What are some disadvantages of biofuels?
Supply of biofuels from wastes are limited to how much waste there is.
Farmland used could be used for cattle or to grow crops for growing population
Some crops have a low energy density
Intensive farming techniques use alot of energy and may release as much CO2 as using fossil fuels.
What is the new biofuel technology hydrogen from algae?
This is where some types of algae produce hydrogen during photosynthesis if they are deprived of sulfur.
The hydrogen can be harnessed to be used as fuel.
What are the environmental impacts of biofuels?
Habitat loss
fertiliser and pesticide use
Use of machinery and use of fossil fuels contributing to global warming
What are the locational constraints of biofuels?
Fertile soils
Suitable climate
How do you get biofuels from microorganisms?
Anaerobic digestion of wastes like sewage, food waste etc releasing methane
Where does geothermal energy come from?
Radioactive decay of isotopes of thorium, uranium and potassium in earth mantle.
What are geothermal springs?
Groundwater that has been heated by hot rocks underground, which comes to the surface in springs.
This can be used in district heating.
What are geothermal aquifers?
Hot groundwater being pumped to the surface from aquifers to be used in district heating.
What type of scheme are geothermal aquifers and geothermal springs?
Low temperature schemes
What are geothermal steam systems?
Where very high temperature ground water is bought to the surface by a borehole, producing steam which can be used to generate electricity.
What are the locational constraints to geothermal energy?
Need a heat source above 150 degrees.
What are the environmental impacts of geothermal?
Pipes can affect the movement of large mammals.
Hot water extracted from the ground can release small amounts of CO2 and hydrogen sulfide.
What are low temperature fluids in geothermal energy?
This is where low temperature water can be used to boil butane/pentane, to turn turbines and generate electricity.
What is a tidal barrage?
A dam across an estuary/bay in which turbines are located, so that water flowing in or out flows over the turbines generating energy.
What are the disadvantages of a tidal barrage?
High cost
High environmental impacts, e.g. injuring fish.
Acts as a physical barrier, can stop fish migrating
What is a tidal lagoon?
A lagoon that surrounds a selected part of an estuary or bay.
How are tidal lagoons in tidal power?
When electricity is being generated but demand is low, water can be pumped into a tidal lagoon. This makes the lagoons level high than sea level, electricity can then be generated when there is no tidal flow.
What are in-stream turbines?
Fixed to the seabed and absorb the kinetic energy from tidal flow.
What are the advantages to tidal power?
Tides are predictable.
Tidal barrages have high electricity output compared to other renewables.
What are the disadvantages of tidal power?
Not constant, so continual demand is hard to reach.
Few suitable sites for construction.
Big environmental impacts.
What are the environmental impacts of tidal barrages?
Barrage requires large amounts of materials to build, so mining has an impact.
Changes tidal range, it is never as high or low as it was before.
Sedimentation build up producing low flow.
Sedimentation can settle so low turbidity, more photosynthetic organisms can survive.
Pollutants may build up in the lagoon.
What are the environmental impacts of tidal lagoons?
Similar to barrages but on a smaller scale.
No barrier across the whole estuary so migrating fish can still pass through.
What are the environmental impacts of in-stream turbines?
Noise pollution
What changes are needed to allow society to be powered by renewables?
New tech so more energy is harnessed more efficiently.
Larger energy storage
Changes to vehicle designs
Changes to the tech that uses electricity to make them more efficient.
What is peak shaving?
Levelling out peaks in electricity demand
How does peak shaving happen?
By businesses storing energy to be used in times of high demand or not using energy in peak times.
What causes fluctuations in energy supply?
Using intermittent energy sources like solar, wind.
Infrequent delivery of energy e.g. coal, biofuels.
War/conflicts
What causes fluctuations in energy demand?
Weather
Seasons
Weekday/weekend
Short term fluctuations like meal times etc
How can peak shaving be done using pumped-storage HEP?
Surplus electricity is used to pump water uphill. The water can then be released in times of high energy demand, it flows through turbines generating electricity.
How are rechargeable batteries used to increase energy storage?
They allow the original chemicals to be reformed using electricity so they can be reused.
What are the factors affecting viability of rechargeable batteries?
Energy density
Recharging speed
Safety, toxic etc
Cost per unit of energy stored.
How can compressed gas be used to increase energy storage?
Surplus energy can be used to drive a pump which compresses air, this produces heat.
The compressed air can be released later to power machinery.
The heat produced can also be stored in oil or molten salt for use later.
What is an example of a secondary fuel?
Electricity
What is a primary fuel?
They come directly from the environment, and can be converted into a secondary fuel
What are the advantages of electricity?
No pollution created when using
Easy conversion to other forms e.g. light
Easy to transport
What are the disadvantages of electricity?
Primary fuel conversion is not efficient
Storage is difficult
Initial production pollution, e.g. combustion of oil and coal producing CO2, PANs, fly ash
How does a battery work?
It delivers energy it has previously stored
How do fuel cells work?
They convert the energy from a fuel to electricity
What is a hydrogen fuel cell?
An electrochemical power generator, uses hydrogen and oxygen.
The hydrogen loses it’s electrons to oxygen, this movement creates the energy.
What is the hydrogen economy?
Storing surplus energy as different forms of hydrogen
What are some ways hydrogen is stored as?
Compressed gas
Liquid
Ammonia
Metal hydride system
Why is hydrogen good for storing energy?
It is reactive
High energy density
Produced by the electrolysis of water
What are the disadvantages of storing hydrogen?
As a liquid energy is needed for refrigeration.
As metal hydrides the storage tanks are big and heavy
As compressed gas energy is needed to run the compressor
What are the problems energy storage fixes?
Energy production can be kept constant
Surplus energy from non constant supplies can be stored until required.
How do you calculate power?
Energy/time
How do you work out efficiency?
total useful energy/total energy input
What is aerodynamics/hydrodynamics?
Reducing friction as a vehicle moves through air or water to reduce the energy needed to propel it.
What does reducing the mass of vehicles do and how can it be done?
Reduce fuel consumption, so less energy used.
Plastics or carbon fibres instead of metal for the body.
Replacing iron engine blocks with aluminium.
Redesign wiring routes so shorter cables are used.
Use high energy density batteries with low mass.
Designing vehicles with rounded 3D surfaces to reduce the SA, less material is used.
What is a kinetic energy recovery system/ regenerative braking?
A system where when braking the kinetic energy is converted to an energy form that can be used or stored, e.g. electricity which is stored as chemical energy in a battery.
The chemical energy can then be used to produce electricity to propel a vehicle.
Why does bulk transport save energy?
Transportation of larger loads on fewer vehicles is more energy efficient, which saves energy.
How should a vehicle be designed for end of life?
Using recyclable materials
Easier identification of materials and their composition, e.g. stamped with code numbers.
Easier dismantling
Using compostable materials
How should wheels be managed to stop energy losses?
Never be underinflated as they lose energy.
What is the embodied energy of a vehicle?
All the energy taken to produce it.
Energy used in manufacture, energy used in transport, energy used to mine components, energy used to ft material the car etc.
What are active traffic management transport/smart motorways?
Motorways with variable speed limits which prevents congestion that causes delays and wastes energy.
How will integrated transport systems help reduce energy?
If changing vehicles in a journey is easier people are more likely to do it. e.g.
A bus stop close to a train station or trains near airports.
Trains that allow bikes on them, or safe lockers for people to keep their bikes at train stations.
How can combustion efficiency be increased?
Efficient gas exhaust removal via more cylinders.
Better engine temp control via thermostatically operated fans
How can building orientation and their features conserve energy?
Larger paned areas facing south to increase the solar gains.
Why are buildings with a low SA:VOL better?
Because they lose less heat
Why should high thermal mass materials be used to conserve energy?
BC they reduce temperature extremes by absorbing heat to reduce over-heating and emit heat to reduce heating requirements.
Why do cement buildings have high embodied energy?
BC cement uses alot of energy to produce
What low embodied materials can be used in buildings?
Limecrete instead of concrete.
Rammed earth instead of concrete block walls.
Lime mortar instead of cement mortar.
What are earth-sheltered buildings and how do they conserve energy?
Builds that are partially built into the ground.
They reduce heat losses as the ground is warmer in cold weather.
What do energy conservation programmes do?
Reduce the temperature gradient and increase material thermal conductivity.
How does double glazing work?
Produces a large gap between window panes with static air or argon, air and argon are poor thermal conductors so no convection current occurs.
The layer of air/gas reduces the temp gradient so heat does not pass to the second pane and into the house.
What is low emissivity glass?
Glass which has a surface coating that reflects longwave infrared energy back into the building.
Cools buildings in summer, heats in winter.
What are heat exchangers and how do they work in ventilation?
They are used for ventilation with minimal heat losses.
Warm waste gas/air leaving a building is transferred to entering cooler air this counter current flow ensures efficient exchange.
How does automatic/solar ventilation work?
Large paned areas increases passive solar gains, however in summer this can cause overheating so solar screens, thermostatically operated screens or self-opening windows can be used.
What are occupancy sensors?
They turn appliances off if occupants are not detected, this conserves energy.
How can insulating materials be improved?
Materials with a reflective foil layer to reflect infrared.
How can heat loss from water be reduced?
If water is heated as it is supplied
Storing heated water in insulated tanks
What are some low energy appliances that can be used?
LED lights
Low energy washing machines with faster spin
Low energy dishwasher that uses less water
Modern ovens with double glazed doors so less heat loss.
What new designs of heat exchangers can be used to increase efficieny?
Using long narrow pipes to increase SA.
Using pipes made of copper, a good thermal conductor
Using a counter-current flow system to maintain the temperature gradient
A slow flow rate so more effective heat exchange.
How are heat exchangers used to recovery energy from industrial waste?
Waste in liquid or gaseous form is usually hot, the heat energy can be recovered by being transferred to cold liquid or gas.
The wastes do not mix as they are carried in a pipe
How can heat lost be reduced with insulation in domestic homes?
Reducing heat loss via using material of low thermal conductivity.
As you reduce heat loss you reduce the amount of energy needed to heat homes.
How can you reduce the SA of tanks storing hot water and what does this do?
You can reduce the SA by using a bigger tank rather than loads of small tanks, this reduces heat loss.
A spherical tank will have a smaller SA: vol than a square tank, this will reduce heat loss even more.
What do combined heat and power stations do?
CHP stations recover the heat loss in electricity generation and uses it to heat homes, fish farms etc.
This reduces the amount of energy wasted.
Why is efficiency kept below 40% in CHP stations?
To increase the temp of water, this increases its usefulness
What is integrated manufacture?
This is where material manufacturing processes are located on the same site, it saves energy
How does integrated manufacture save energy?
Waste heat from one industry used in another.
Molten iron from blast furnaces converted directly into steel, this saves the energy of having to melt the iron again.
Less transportation of materials needed as the sites are closer together.
How can recycling reduce energy used?
Reduces the waste and the use of new resources, reduces energy by producing new products from used materials which uses less energy.
How does recycling aluminium save energy?
Most energy used is used to convert aluminium ore into aluminium metal, so by recycling you cut this process out
When would recycling not save energy?
During the transportation and collection of recycled wastes to where they are to be disposed of due to the size of material being recycled.
What is a high voltage grid?
Where transformers are used to control the current and voltage of electricity in the grid to reduce energy loss
Why does the national grid distribute energy at high voltage?
So that the current can be reduced to minimise energy losses, but also maintaining the power
How do you calculate electrical power?
Current X potential difference/volts
What does the resistance to flow of electricity in a cable cause?
loss of energy as it is converted to heat
How does IT management reduce energy loss?
Allows electricity demand to be accurately predicted and monitored.
This reduces the energy wasted in generating electricity when there was no demand for it.
What are the key principles of energy resources?
Energy supplies are vital for the development of society
The properties of energy resources affect their usefulness
Energy resources used now will not be the man resources used in the future
All energy resources have environmental impacts
New tech increases efficiency of energy
How does HEP work?
Water is stored as gravitational potential energy as it is higher than water below the dam, when the water falls the energy is converted to kinetic energy which turns turbines to generate electricity.
