Renewable energy resources Flashcards
1
Q
Describe how photothermal systems work
A
- 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
2
Q
Key things to remember about how photothermal systems work
A
- never boils the water - used for bathing and washing clothes
- does not produce electricity
3
Q
Describe how passive solar architecture can heat and cool buildings
A
- 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
4
Q
Describe how solar associated heat pumps work
A
- 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
5
Q
Describe how photovoltaic systems work
A
- 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
6
Q
Advantages of using solar power
A
- renewable energy source
- job creation
- doesn’t release CO2 upon combustion
- safer than others
7
Q
Disadvantages of solar power
A
- intermittent
- high initial costs
- weather dependent
- made with rare and finite materials
8
Q
What is a heliostat
A
- an apparatus containing a movable mirror, used to reflect sunlight in a fixed direction
9
Q
What is a parabolic reflector
A
- a reflective surface used to collect or project energy such as light, sound or radio waves
10
Q
What is concentrating solar power with thermal storage
A
- 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
11
Q
What is anti-reflective surfaces
A
- cells with a-rs are textured and bumpy
- some structures mimic corneas of moth eyes because they are very efficient at absorbing light
12
Q
What is multi-juction photovoltaic cells
A
- has multiple layers that each absorb different wavelengths of light
- meaning more energy can be released
13
Q
What are photvoltaic/thermal hybrid systems
A
- mix up of old-style photothermal and are producing electricity with photovoltaic sandwich
- heating water and producing electricity
14
Q
What are transparent pv cells
A
- can use them as windows
- increase surface that we can utilise
15
Q
What are self-cleaning panels
A
- hydrophobic layer on them - repels water
- helps carry dust and particles with it
16
Q
Define gravitational potential energy
A
- the energy an object has due to its position above earth, energy due to its height
17
Q
What features of the environment allow for the development of a HEP scheme
A
- large river catchment area
- high and regular rainfall
- valley with steep sides
- want the water to have low turbidity
18
Q
Define what high head means
A
- how high the water falls
- might include fast flowing upland stream schemes
19
Q
Define what low head means
A
- water falls from a lower distance
- may include old mill sites with a weir
20
Q
Define run of the river
A
- operating the flow of the river without modification by upstream storage
21
Q
What are the advantages of HEP
A
- renewable energy source
- flood control + water supply
- creation of freshwater habitats
- use for recreational use
22
Q
What are the disadvantages of HEP
A
- environmental impact - construction
- displacement of communities
- dependent on weather
- cause sedimentation
23
Q
How is wind generated
A
- from difference in temperature pressure (caused by the sun’s energy)
- air moves in an attempt to reach equilibrium
24
Q
What locational factors are needed for wind farms
A
- ^ winds for a lot of the year
- local constraints - may impact construction
- public opposition - providing incentives
- they interfere with telecommunications
25
What does HAWT stand for
- horizontal axis wind turbines
26
What are advantages of HAWT’s
- renewable energy source
- lower maintenance costs
- efficient
- simple technology
27
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
28
What does VAWT stand for
- vertical axes wind turbines
29
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
30
What are the disadvantages of VAWT’s
- lots of disadvantages are similar to previous
- produce less energy compared to HAWT’s
31
What are some advantages of wind power
- abundant
- predictable
- renewable energy source
- lower maintenance cost
- reliable
32
What are some disadvantages of wind power
- weather dependent
- noise pollution
- visual impacts
- intermittent
- space requirement
33
How has blade tip fins improved energy production
- curved tips
- reduce air resistance
- reduce turbulence
- blades move faster
34
What are blade tip fins an example of
biomimetics
35
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
36
How has direct drive turbines improved energy production
- increases revolutions per minute
- generates electricity at low wind speeds
37
How has helical VAWT blades improved energy production
-reduce air resistance because turbines are curved
- generate electricity at low wind speeds
38
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
39
What type of energy is harnessed from waves
- kinetic energy
- vertical wave movement
40
What factors produce large waves
- strong winds
- movement of water
41
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
42
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
43
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
44
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
45
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
46
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
47
What are some advantages of wave power
- renewable energy source
- predictable
- minimal enviro impacts
- useful in more coastal, remote areas
48
What are some disadvantages of wave power
- high initial costs
- limited locations
- maintenance challenges
- intermittent
49
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)
50
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
51
What are some disadvantages of biofuels
- still release CO2
- public opposition
- impact on biodiversity
- seasonal variability
51
What are some advantages of biofuels
- renewable energy source
- reduced greenhouse gas emissions
- waste reduction
- predictable
52
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
53
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
54
What are 2 low temperature schemes
- geothermal springs
- geothermal aquifers
55
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
56
What are geothermal aquifers
- hot groundwater may be pumped to the surface from underground aquifers to be used in district heating schemes
57
What are 2 high temperature schemes
- geothermal steam systems
- hot dry rock systems
58
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
59
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
60
What factors are needed to harness geothermal energy
- areas of hot rock
- under the surface
61
What are advantages of geothermal power
- renewable energy source
- low intermittency
- predictable
- low technological developments
62
What are disadvantages of geothermal power
- high initial costs
- local constraints
- releases CO2
- difficult to transport
63
What are some new future developments for geothermal
- geothermal fluid extraction
- heat exchange
- vaporization
64
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
65
What factors make harnessing tidal power viable
- being able to harness it close to coastline
- topography of the sea bed
66
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
67
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
68
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
69
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
70
What is advantages of tidal power
- renewable
- low emissions
- long lifespan
- predictable
71
What is disadvantages of tidal power
- possible migration barrage
- high initial costs
- intermittent
- potential for erosion
72
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
73
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
74
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
75
What is the most common example of the use of a secondary fuel
- converting primary furl to electricity
76
How does a coal fired power station work
1. pulverising (increase SA)
2. combustion
3. steam generation
4. turbine operation
5. electricity generation
6. cooling system
7. electricity distribution
77
Which energy resources can produce steam which can be used in a steam powered turbine to produce electricity
- coal
- oil
- gas
- uranium
78
Explain how other energy sources produce electricity via kinetic energy
- tidal
- wind
- wave
- HEP
79
What is a fuel cell
- a chemical battery
- uses a chemical reaction to produce energy (electricity)
80
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
81
Define peak shaving
- storing energy at times of excess for a later time of high demand
82
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
83
Advantages of using electricity
- versatile
- ease of transport
- storage options
- reduced pollution upon use
84
Disadvantages of using electricity
- infrastructure costs
- energy losses
- dependence on non-renewable sources
- health and safety risks
85
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
86
How can electrolysis be a long term solution when used with intermittent renewables
- energy storage
- flexibility in use
- long-distance transport
87
How can hydrogen be stored
- pressurized container
- liquid hydrogen storage
- chemical storage
88
What problems are associated with the storage of hydrogen
- safety risks
- leakage
- cost
- public opposition
89
Combustion and hydrogen
- used similarly to natural gas
- pumped into an existing network
90
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
91
Why do we need to store energy
- balancing supply and demand
- reducing energy costs
- enhancing grid stability
92
Why might surplus electricity be available
- high renewable generation
- low demand periods
- wind farms at night
93
Causes in fluctuations in energy supply
- seasonal changes
- demand variability
- equipment failures
94
Causes in fluctuation in energy demand
- time of day
- seasonal changes
- holidays and events
95
How can we store energy
- small scale batteries
- large scale batteries
- pumped hydro storage
96
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
97
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
98
What are small scale rechargeable batteries used in
- remote controls
- toys
- electric vehicles
- consumer electronics e.g phones
99
What are large scale rechargeable batteries used in
- grid energy storage
- electric vehicle charging stations
- microgrids
100
Disadvantages of the use of rechargeable batteries
- limited lifespan
- cost
- enviro impacts - if not disposed properly
- long charging time
101
3 types of storage systems
- high volume storage
- heat energy
- high thermal mass buildings
102
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
103
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
104
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
