Renewable energy resources Flashcards
Describe how photothermal systems work
- use light to increase temperature
- used to heat water
- you pump water into cells, run it up and down into a pipe
- exposes more water to sunlight which releases energy
- this increases SA:VOL
Key things to remember about how photothermal systems work
- never boils the water - used for bathing and washing clothes
- does not produce electricity
Describe how passive solar architecture can heat and cool buildings
- can have lots of windows on the south facing walls
- big, long walls south facing, shorter on the other sides
- light reflective surface - lose heat (white buildings
- dark absorbant surfaces - retain the heat
Describe how solar associated heat pumps work
- heat pump contains a liquid with very low boiling point
- that liquid can turn into a gas at low temps
- the liquid raises its temperatures in the panel
- the gas produced goes to a compresser
- heat goes to a heat exchanger
Describe how photovoltaic systems work
- N type is doped with phosphorus and this adds electrons so is electron rich (very negative)
- the p side is doped with boron electron poor - lacks negative electrons
- excess electrons on the n type layer gain energy
- they move to the p type sode
- continuous movement of electrons = a current
Advantages of using solar power
- renewable energy source
- job creation
- doesn’t release CO2 upon combustion
- safer than others
Disadvantages of solar power
- intermittent
- high initial costs
- weather dependent
- made with rare and finite materials
What is a heliostat
- an apparatus containing a movable mirror, used to reflect sunlight in a fixed direction
What is a parabolic reflector
- a reflective surface used to collect or project energy such as light, sound or radio waves
What is concentrating solar power with thermal storage
- operation on a large scale
- mirrors that reflect suns energy to a central point
- producing salt - retain heat thats able to boil water through the night
What is anti-reflective surfaces
- cells with a-rs are textured and bumpy
- some structures mimic corneas of moth eyes because they are very efficient at absorbing light
What is multi-juction photovoltaic cells
- has multiple layers that each absorb different wavelengths of light
- meaning more energy can be released
What are photvoltaic/thermal hybrid systems
- mix up of old-style photothermal and are producing electricity with photovoltaic sandwich
- heating water and producing electricity
What are transparent pv cells
- can use them as windows
- increase surface that we can utilise
What are self-cleaning panels
- hydrophobic layer on them - repels water
- helps carry dust and particles with it
Define gravitational potential energy
- the energy an object has due to its position above earth, energy due to its height
What features of the environment allow for the development of a HEP scheme
- large river catchment area
- high and regular rainfall
- valley with steep sides
- want the water to have low turbidity
Define what high head means
- how high the water falls
- might include fast flowing upland stream schemes
Define what low head means
- water falls from a lower distance
- may include old mill sites with a weir
Define run of the river
- operating the flow of the river without modification by upstream storage
What are the advantages of HEP
- renewable energy source
- flood control + water supply
- creation of freshwater habitats
- use for recreational use
What are the disadvantages of HEP
- environmental impact - construction
- displacement of communities
- dependent on weather
- cause sedimentation
How is wind generated
- from difference in temperature pressure (caused by the sun’s energy)
- air moves in an attempt to reach equilibrium
What locational factors are needed for wind farms
- ^ winds for a lot of the year
- local constraints - may impact construction
- public opposition - providing incentives
- they interfere with telecommunications
What does HAWT stand for
- horizontal axis wind turbines
What are advantages of HAWT’s
- renewable energy source
- lower maintenance costs
- efficient
- simple technology
What are disadvantages of HAWT’s
- intermittent
- noise pollution
- visual impact - ruins aesthetic
- bird and bat strike (deaths)
- soil boots can be impacted by the vibrations when turbines are turning
What does VAWT stand for
- vertical axes wind turbines
What are the advantages of VAWT
- smaller footprint
- spin no matter the wind direction
- start turning at lower wind velocities
- have them in more built up areas
What are the disadvantages of VAWT’s
- lots of disadvantages are similar to previous
- produce less energy compared to HAWT’s
What are some advantages of wind power
- abundant
- predictable
- renewable energy source
- lower maintenance cost
- reliable
What are some disadvantages of wind power
- weather dependent
- noise pollution
- visual impacts
- intermittent
- space requirement
How has blade tip fins improved energy production
- curved tips
- reduce air resistance
- reduce turbulence
- blades move faster
What are blade tip fins an example of
biomimetics
How has nacelle brushes improved energy production
- reduce air escaping from the base of the blades to the nacelle
- increase kinetic energy that can be absorbed by the blades
How has direct drive turbines improved energy production
- increases revolutions per minute
- generates electricity at low wind speeds
How has helical VAWT blades improved energy production
-reduce air resistance because turbines are curved
- generate electricity at low wind speeds
How has wind-assisted ships improved energy production
-harness the power of wind to supplement the propulsion of a vessel by generation of aerodynamic forces
What type of energy is harnessed from waves
- kinetic energy
- vertical wave movement
What factors produce large waves
- strong winds
- movement of water
What are the best sites to harness wave power
- the further out to sea = the larger the waves
- large fetch = big area of wind and wave speed can increase
What is a point absorber
- have a floating structure which rises and falls as waves pass
- this is attached to a non-moving base located on the seabed
- movement of the floating part turns a generator
What is a overtopping device
- breaking waves force water into a storage reservoir which is above sea level
- the water flows back to the sea passing through a turbine which generates electricity
What is a oscillating wave surge converter
- water moves both horizontally and vertically, producing a cycle
- pushes a flat plate which means pistons to pump fluid over a turbine to generate electricity
What is a surface attenuator
- a hinged floating device
- moving sections push and pull pistons which force a fluid over a turbine
- this generates electricity
What is an oscillating water column
- rise and fall of water = forces water up and down in a submerged chamber
- the air that is forced in and out flow over turbines
- generates electricity
What are some advantages of wave power
- renewable energy source
- predictable
- minimal enviro impacts
- useful in more coastal, remote areas
What are some disadvantages of wave power
- high initial costs
- limited locations
- maintenance challenges
- intermittent
What crops are deliberately grown for their energy value
- wood (convert it to charcoal)
- miscanthus (grows really quickly, low maintenance)
- ethanol (from corn and sugar cane)
Waste materials from other activities used as biofuels
- burn domestic and commercial waste in an incinerator
- methane from landfill sites - combusted
- crop waste (roots etc) - burn it
What are some disadvantages of biofuels
- still release CO2
- public opposition
- impact on biodiversity
- seasonal variability
What are some advantages of biofuels
- renewable energy source
- reduced greenhouse gas emissions
- waste reduction
- predictable
How to achieve hydrogen from algae
- specific algae produced
- mimics sunlight with LED’s
- algae absorbs CO2 + H2O + energy and builds up hydrocarbons and proteins
- extract H+, pressurise and can store it
Where does geothermal energy come from
- residual heat from formation of solar system
- heat rises and is transferred to earth’s crust
- radioactive decay of isotopes of thorium,uranium and potassium in the earth’s mantle releases heat
What are 2 low temperature schemes
- geothermal springs
- geothermal aquifers
What are geothermal springs
- groundwater that has been heated by hot rocks underground may come to the surface in hot springs. This can be used for district heating
What are geothermal aquifers
- hot groundwater may be pumped to the surface from underground aquifers to be used in district heating schemes
What are 2 high temperature schemes
- geothermal steam systems
- hot dry rock systems
What are geothermal steam systems
- groundwater at very high temps may be brought to the surface using an extraction borehole, producing high temperatures
- the steam at the surface can be used to generate electricity by turning a turbine
What are hot dry rock systems
- water is pumped down an injection in the borehole and steam is recovered using a second borehole
- fracturing the rocks underground may increase permeability if rock and the surface area exposed for heat absorption
What factors are needed to harness geothermal energy
- areas of hot rock
- under the surface
What are advantages of geothermal power
- renewable energy source
- low intermittency
- predictable
- low technological developments
What are disadvantages of geothermal power
- high initial costs
- local constraints
- releases CO2
- difficult to transport
What are some new future developments for geothermal
- geothermal fluid extraction
- heat exchange
- vaporization
What is the source of energy used for tidal power
- gravitational attraction between the water and the moon
- gravitational attraction of the moon, is dependent on the sun’s position, near the moon
What factors make harnessing tidal power viable
- being able to harness it close to coastline
- topography of the sea bed
What can be done to increase the velocity of water flow caused by tides
- tide moving into a more narrow space
- this increases velocity of water
What is a tidal barrage
- water flows over it at high tide
- close the gates until the tide has lowered
- open the gates and water escapes and turns turbines that are built in the barrage
What is a tidal lagoon
- build a pool shape
- at high tides the water enters the pool
- once ride has gone down the water is then released and flows over turbines
What is a in-stream turbine
- fixed to the seabed + absorb kinetic energy of the natural tidal flow
- they harness much less energy than the others
- enviro impacts are very low
What is advantages of tidal power
- renewable
- low emissions
- long lifespan
- predictable
What is disadvantages of tidal power
- possible migration barrage
- high initial costs
- intermittent
- potential for erosion
What are tidal reefs
- formed by an accumulation of sediments, rocks or coral in areas where tidal currents are strong
- they provide habitats for marine species
- protect shoreline from erosion
What is a primary fuel
- type of energy source that is extracted from natural resources and used directly to produce energy
- typically raw materials that haven’t been processed
What is a secondary fuel
- energy source that is derived from the processing or transformation of primary fuels
- they have undergone some form of conversion
What is the most common example of the use of a secondary fuel
- converting primary furl to electricity
How does a coal fired power station work
- pulverising (increase SA)
- combustion
- steam generation
- turbine operation
- electricity generation
- cooling system
- electricity distribution
Which energy resources can produce steam which can be used in a steam powered turbine to produce electricity
- coal
- oil
- gas
- uranium
Explain how other energy sources produce electricity via kinetic energy
- tidal
- wind
- wave
- HEP
What is a fuel cell
- a chemical battery
- uses a chemical reaction to produce energy (electricity)
How does a fuel cell work
- feed the cell with hydrogen and oxygen
- hydrogen loses electrons and are now H+ ions
- H+ ions move through the membrane to meet O2- ions and produce H20
- electrons are forced to take a different route
- only waste - water
Define peak shaving
- storing energy at times of excess for a later time of high demand
Explain how electricity can be transported
- electricity goes to a step up transformer
- increases voltage
- travels further - travels through cables
- reaches a step down transformer
- decreases voltage
- electric energy is moved through a grid system
Advantages of using electricity
- versatile
- ease of transport
- storage options
- reduced pollution upon use
Disadvantages of using electricity
- infrastructure costs
- energy losses
- dependence on non-renewable sources
- health and safety risks
Explain how hydrogen can be produced by the electrolysis of water
- place anode and cathode in water
- add power
- then splits water molecules to H+ ions and O2- ions
- the H+ move to the cathode
- the O2- ions move to anode
How can electrolysis be a long term solution when used with intermittent renewables
- energy storage
- flexibility in use
- long-distance transport
How can hydrogen be stored
- pressurized container
- liquid hydrogen storage
- chemical storage
What problems are associated with the storage of hydrogen
- safety risks
- leakage
- cost
- public opposition
Combustion and hydrogen
- used similarly to natural gas
- pumped into an existing network
Fuel cells and hydrogen
- feed cells with H+ and O2
- hydrogen loses e- and are now H+ molecules
- H+ moves through membrane to meet O2- ions and produce H2O
- e- are forced to take a different route
- creates a current
Why do we need to store energy
- balancing supply and demand
- reducing energy costs
- enhancing grid stability
Why might surplus electricity be available
- high renewable generation
- low demand periods
- wind farms at night
Causes in fluctuations in energy supply
- seasonal changes
- demand variability
- equipment failures
Causes in fluctuation in energy demand
- time of day
- seasonal changes
- holidays and events
How can we store energy
- small scale batteries
- large scale batteries
- pumped hydro storage
What is pumped storage HEP
- uses 2 water reservoirs at different elevations
- electricity pump water from lower reservoir to the higher reservoir
- ^ energy demand = water is released back down to the lower reservoir, passing through turbines to generate electricity
What is compressed gas
- storing energy by compressing air in underground caverns or storage tanks
- excess energy available = air is compressed using electricity
- compressed air is stored until energy is needed
- demand rises = compressed air released and heated to drive a turbine and generate electricity
What are small scale rechargeable batteries used in
- remote controls
- toys
- electric vehicles
- consumer electronics e.g phones
What are large scale rechargeable batteries used in
- grid energy storage
- electric vehicle charging stations
- microgrids
Disadvantages of the use of rechargeable batteries
- limited lifespan
- cost
- enviro impacts - if not disposed properly
- long charging time
3 types of storage systems
- high volume storage
- heat energy
- high thermal mass buildings
What is high volume storage
- volume of heat store increases - SA:VOL decreases
- large heat stores can be used for interseason energy storage, such as absorbing surplus solar energy from the summer for heating buildings in the winter
What is heat energy
- long term storage is difficult
- short term storage is more efficient
- thermal storage systems = use of molten salt, high volume hot water stores, use of thermal mass materials
What is high thermal mass buildings
- buildings constructed with high SHC materials (concrete), warm up and cool down slowly
- reduces overheating during hot weather, therefore reduces the need for air conditioning
- reduces need for heating at the beginning of cole weather
