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A Level Environmental Science > Energy Resources - Renewables > Flashcards

Energy Resources - Renewables Flashcards

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1
Q

Which energy resources can be described as solar-driven?

A
  • Solar
  • Biofuels
  • Wind
  • Wave
  • HEP
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2
Q

How do photothermal systems work?

A

Photothermal panels absorb sunlight to heat water (does not produce electricity)

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3
Q

What are photothermal systems used for?

A
  • Space heating
  • Domestic hot water
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4
Q

How are photothermal systems designed?

A

Long thin pipes to increase SA:V

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5
Q

How does passive solar architecture work?

A

Buildings can be designed in certain ways either to heat or cool them

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6
Q

What are examples of PSA in the Northern Hemisphere?

A
  • Build windows on long, south-facing walls to absorb more heat
  • Build windows on long, north-facing walls to absorb less heat
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7
Q

What is an example of PSA which is globally applicable?

A

Use light reflective surfaces or dark surfaces to alter heat absorption

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8
Q

How does a solar-assisted heat pump work?

A
  • Liquid/refrigerant with a low BP changes state to a gas when passed through the panel
  • Gas is compressed back into a liquid and releases heat energy
  • Liquid passed through a heat exchanger to heat water
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9
Q

How is a photovoltaic cell configured?

A
  • Silicon sandwich
  • Top layer is negative as it is doped with phosphorus (adds e-)
  • Bottom layer is positive as it is doped with boron (removes e-)
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10
Q

How can the layers of a PV cell be described?

A
  • N layer is electron rich
  • P layer is electron poor
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11
Q

How does a PV cell work?

A
  • Excess electrons in N layer gain Ek in the Sun
  • Electrons move through the conductor to the P layer
  • Continuous movement of electrons creates a current
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12
Q

What is a heliostat?

A

A device which alters the angle of a solar panel so it is at the optimum angle for sunlight absorption

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13
Q

What is a parabolic reflector?

A

A concave structure which concentrates sunlight to a focus point (produces increased temperatures)

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14
Q

What is concentrating solar power?

A

Mirrors are used to reflect sunlight to a central point and heat salt to a molten salt

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15
Q

What is the main advantage of CSP?

A
  • Salt heated to above 100C
  • Molten salt retains heat for long periods and can be used to boil water at night
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16
Q

How do anti-reflective surfaces work?

A

Solar panels can be grooved or textured instead of having a shiny layer to increase sunlight absorption

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17
Q

How do multi-junction PV cells work?

A

Multiple layers of material absorb different wavelengths of light (greater amount can be absorbed)

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18
Q

How do PVT hybrid systems work?

A

Heat energy is absorbed for space heating when temperature is to high for PV cells to work efficiently

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19
Q

Where are transparent PV cells used?

A

Windows

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20
Q

How do self-cleaning solar panels work?

A
  • Hydrophobic layer
  • Rainfall runs off at an increased rate and carries off dust particles
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21
Q

What is GPE?

A

The energy of an object due to its position above Earth

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22
Q

What features are needed for a HEP scheme?

A
  • Large catchment area
  • Regular precipitation
  • Valley with steep sides
  • Low turbidity water
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23
Q

What is a high head HEP scheme?

A
  • Head in excess of 50m
  • Low rate of water flow with greater vertical drop
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24
Q

What is a low head HEP scheme?

A
  • Head below 5m
  • High rate of water flow with smaller vertical drop
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25
Q

What is a run of the river HEP scheme?

A

HEP scheme which doesn’t store water or divert its natural flow

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26
Q

What is a Kaplan turbine?

A

HEP turbine with blades which can be rotated to increase efficiency

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27
Q

What is a helical turbine?

A

HEP turbine where water flows down a screw to turn it and generate electricity

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28
Q

What are advantages of helical turbines?

A
  • Fish can be carried through without harm
  • Can use high turbidity water without being damaged
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29
Q

How is wind generated?

A

Blows to equalise differences in high and low pressure caused by heating from the Sun

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30
Q

What are some locational factors required for wind energy?

A
  • Regular high wind velocity
  • High altitudes or coastal
  • UK has SW prevailing winds
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31
Q

What type of wind turbines are the most common

A

HAWTs

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32
Q

What are advantages of HAWTs?

A
  • Advanced technology
  • More efficient than VAWTs
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33
Q

What are advantages of VAWTs?

A
  • Wind can be from any direction (can be used in cities)
  • Less noise pollution
  • Operate at lower wind velocities
34
Q

What are disadvantages of HAWTs?

A
  • Stress cracking on the blades
  • Requires taller towers
  • Heavier generator
35
Q

What are disadvantages of VAWTs?

A
  • No very large VAWTs have been built
  • Lower efficiency than HAWTs
36
Q

How do blade tip fins work?

A

Curved edges on blades reduce wind resistance and turbulence, therefore increasing efficiency

37
Q

What are blade tip fins an example of?

A

Biomimetics - shark fins

38
Q

What are nacelle brushes?

A

Brushes places between blades and the nacelles to reduce air escaping (more Ek can be absorbed by the blades)

39
Q

What are direct drive turbines?

A

No gearbox is present so electricity can be generated at lower wind velocities

40
Q

What is the main disadvantage of direct drive turbines?

A

Generates DC rather than AC and therefore requires an inverter

41
Q

What are helical VAWT blades?

A

Concave blades which reduce wind resistance and therefore generates at lower velocities

42
Q

What is a wind-assisted ship?

A

A ship which uses wind power to reduce the energy consumption of a ship

43
Q

What is the main disadvantage of wind-assisted ships?

A

Wind is intermittent and therefore cannot be the only energy resource used

44
Q

What type of energy is harnessed from waves?

A

Kinetic energy from the vertical movement of waves

45
Q

What factor produces large waves?

A

Strong winds

46
Q

Which sites are best for harnessing wave power?

A
  • Far out at sea
  • Large fetch (open water)
47
Q

How does a point absorber work?

A
  • Floating structure which is attached to the seabed
  • Piston rises and falls as waves passes (drives a generator)
48
Q

How does an overtopping device work?

A
  • Breaking waves force water into a storage reservoir above sea level
  • Water flows back to sea through a turbine at the base
49
Q

How does an oscillating wave surge converter work?

A
  • Passing waves produce a cycle of horizontal and vertical movement
  • Large paddle oscillates and pumps fluid over a turbine to generate electricity
50
Q

How does a surface attenuator work?

A
  • Hinged floating device
  • Passing waves push and pull pistons to force fluid over a turbine to generate electricity
51
Q

How does an oscillating water column work?

A
  • Rising and falling water forces air to move vertically in a submerged chamber
  • Air is forced in and out and flows over a turbine to generate electricity
52
Q

What crops can be grown for biofuel use?

A
  • Wood (charcoal)
  • Elephant grass (miscanthus)
  • Corn/sugarcane (ethanol)
  • Rapeseed/sunflowers (biodiesel)
53
Q

Which waste materials can be used as biofuels?

A
  • Incineration of domestic waste
  • Landfill biogas (CH4)
  • Combustion of crop waste (straw)
  • Anaerobic digestion
54
Q

What is the energy density of biofuels?

A

Most are low energy density but alcohol and biodiesel have a similar energy density to fossil fuels

55
Q

What energy do biofuels utilise?

A

Stored energy from recent photosynthesis

56
Q

What is the main advantage of biofuel use?

A

Carbon neutrality - releases the same amount of CO2 as it absorbed during photosynthesis

57
Q

What are the main environmental impacts of biofuels?

A
  • Habitat loss
  • Pesticide use
  • Fertiliser use
  • CO2 from intensive farming
58
Q

What is hydrogen from algae?

A

Some types of algae produce hydrogen during photosynthesis, which can be used as a fuel

59
Q

What is anaerobic digestion?

A

The break down of waste to produce fuel in the absence of oxygen

60
Q

What does anaerobic digestion produce?

A
  • Biogas for fuel or gas supply
  • Digestate for fertiliser or livestock bedding
61
Q

Where does geothermal heat originate?

A
  • Radioactive decay within Earth’s core of elements such as uranium and thorium
  • Residual heat from the formation of the universe
62
Q

How does geothermal heat reach the surface?

A

Molten magma rises within the mantle towards the crust

63
Q

What are the two types of geothermal schemes?

A
  • Low temperature
  • High temperature
64
Q

What are low temperature geothermal schemes?

A
  • Geothermal springs bring heated groundwater to the surface for district heating
  • Geothermal aquifers provide hot groundwater for district heating
65
Q

What is the main disadvantage of low temperature geothermal schemes?

A

No electricity is produced as no steam is present

66
Q

What are high temperature geothermal schemes?

A
  • Geothermal steam systems bring hot water through a borehole to produce steam
  • Hot dry rock systems inject water through a borehole to heat it and recover steam through a second borehole
67
Q

At what temperature do high temperature geothermal schemes occur?

A

100C+

68
Q

What factors are needed to harness geothermal energy?

A
  • Large magma intrusion
  • Heat source 150C+
  • Recent volcanic activity
  • Hot rocks close to the surface
  • Tectonic activity
69
Q

How do binary cycle geothermal power plants work?

A
  • Water as cool as 60C can be used to boil butane or pentane in liquid form
  • Produces electricity at lower temperatures
  • Water pumped underground for heating (not to BP)
70
Q

What technology does a binary cycle power plant use?

A

Heat exchanger

71
Q

What are the main environmental impacts of geothermal energy?

A
  • Waste water contains salts and heavy metals
  • Releases some CO2 and hydrogen sulfide
72
Q

What source of energy is used for tidal power?

A

Gravitational attraction between the Earth and the moon

73
Q

What is a tidal barrage?

A
  • A dam across an estuary or bay
  • Gates are shut at high tide and water is released through turbines at low tide
74
Q

What is a tidal lagoon?

A
  • A barrier surrounding a selected part of an estuary
  • Fills at high tide and water is released through turbines at low tide
75
Q

What are in-stream turbines?

A

Turbines fixed to the seabed which harness the Ek of tidal flow

76
Q

What is the main advantage and disadvantage of in-stream turbines?

A
  • Low environmental impact
  • Harnesses less energy than barrages and lagoons
77
Q

How does a tidal reef differ from a tidal barrage?

A

The reef is not as tall as the barrage and therefore marine wildlife can move over it

78
Q

What are the main disadvantages of tidal power?

A
  • Few suitable locations
  • Sedimentation
  • Pollutant concentration
  • Blocks shipping routes
79
Q

What is the main advantage of tidal power?

A

Predictable (25 hour tidal cycle)

80
Q

What is the 25 hour tidal cycle made up of?

A
  • Two periods of high tide
  • Two periods of low tide

A Level Environmental Science (23 decks)

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