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Environmental Science > Renewable Energy Resources > Flashcards

Renewable Energy Resources Flashcards

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1
Q

How do photothermal systems work?

A

pump water into cells and run it through thin pipes to increase surface area

water heats up

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2
Q

What is the water from photothermal systems used for?

A

bathing, washing, space heating

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3
Q

Examples of passive solar architecture

A

windows on south facing walls

elongate buildings - largest wall = south facing

light stone = reflects light, dark stone = absorbs light

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4
Q

How do solar assisted heat pumps work?

A

heat pump contains liquid with very low BP, so gas at low temperatures

liquid raises its temp in the panel

gas is compressed to liquid, releasing energy in the form of heat

heat exchanger used to heat water

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5
Q

Photovoltaic system: N-type side

A

doped with phosphorus

adds electrons

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6
Q

Photovoltaic system: P-type side

A

doped with boron

electron deficient

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7
Q

How do photovoltaic systems work?

A

excess electrons on N-type side gain energy from the Sun

electrons move to P-type side

continuous movement of electrons creates a current

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8
Q

What is sandwiched in a photovoltaic cell?

A

silicon

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9
Q

Advantages of solar power

A

renewable
reduces electricity bills
low operating costs
versatile applications
predictable

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10
Q

Disadvantages of solar power

A

high initial costs
intermittent
habitat loss due to space requirements
energy storage costs
limited energy production
made of finite materials recovered by mining
low energy density

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11
Q

Solar power case study: Australia

A

highest solar energy use per capita

10% of electricity in 20-21

more than 30% of households have rooftop photovoltaics

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12
Q

What is a heliostat?

A

device with mirrors that reflect sunlight towards a specific point to generate electricity

mirrors move for optimum angle

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13
Q

What is a parabolic reflector?

A

curved mirror that focuses rays of light onto a single point

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14
Q

New technology: concentrating solar power (CSP) with thermal storage

A

large scale

thousands of mirrors reflecting to central point, often on top of tower

salt heated to over 100 degrees, molten salt retains heat longer/ after Sun’s gone

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15
Q

New technology: anti-reflective surfaces

A

bumpy/ grooved solar panel surfaces = higher surface area

mimic structure of moth corneas

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16
Q

New technology: multi-junction photovoltaic cells

A

more layers than traditional photovoltaic cells

each layer absorbs different wavelengths of light, more light absorbed, more energy produced

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17
Q

New technology: photovoltaic/thermal hybrid systems (PVT)

A

reduces energy lost during conversion

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18
Q

New technology: transparent PV cells

A

used as windows

increases amount of cells that can be put on buildings

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19
Q

New technology: self cleaning panels

A

hydrophobic outer layer

rain runs off and removes dirtt

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20
Q

What features of the environment allow for the development of a HEP scheme?

A

large catchment
high and regular rainfall
steep sided valley with impermeable rock
no seismic activity
low turbidity
close to grid system/end user

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21
Q

HEP schemes: high head

A

use natural downward flow of river to utilise kinetic energy
significant drop in elevation (100m+)

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22
Q

HEP schemes: low head

A

less than 15m drop
utilises existing weirs

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23
Q

HEP schemes: run of the river

A

harvest the energy from flowing water

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24
Q

Advantages of HEP

A

renewable
low emissions
reliable
energy storage
flood control

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25
Q

Disadvantages of HEP

A

habitat loss
displacement of communities
high initial costs
risk of dam failure
sedimentation
high embodied energy
affects migration
lack of nutrients downstream

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26
Q

How is wind generated?

A

differences in temp and pressure

air moves to reach equilibrium

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27
Q

What locational factors impact the placement of wind farms?

A

high winds for significant amount of time
prevailing wind direction
land use conflicts
public opposition
local planning constraints
interference with telecommunications

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28
Q

Horizontal Axis wind turbine

A

centre of turbine is attached perpendicular to the post

most common

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29
Q

Advantages of Horizontal Axis wind turbines

A

renewable
low emissions
increases energy independence
scalability
higher energy outputs (installed at greater heights)
lower maintenance costs as more common

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30
Q

Disadvantages of Horizontal Axis wind turbines

A

noise pollution
ruins aesthetics
bird and bat strikes
high installation costs
high embodies energy
public opposition
reduces soil biota

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31
Q

Advantages of Vertical Axis wind turbine

A

smaller footprint than HA
rotate in any wind direction
rotate in lower wind velocities

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32
Q

Disadvantages of Vertical Axis wind turbine

A

same as HAWTs
produce less energy

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33
Q

Case study: offshore wind farm

A

dogger bank
18-60m depth = shallow
fixed seabed turbines
5% of UK’s demand
1 rotation = power home for 2 days

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34
Q

Case study: onshore wind farm

A

hyndburn wind farm
12 turbines
generate enough electricity to power over half the homes in hyndburn each year
community benefit fund established

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35
Q

Developments in wind energy production: blade tip fins

A

curved edges reduces air resistance
increased efficiency

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36
Q

Developments in wind energy production: nacelle brushes

A

reduce air escaping from the base of the blades and the nacelle
more kinetic energy absorbed by the blades

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37
Q

Developments in wind energy production: direct drive turbines

A

no gearbox so, quieter, cheaper, able to generate electricity at lower wind speeds
electricity produced in DC, so inverter needed

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38
Q

Developments in wind energy production: helical VAWT blades

A

concave blades
reduces wind resistance
increases efficiency
rotates smoother and at lower wind speeds

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39
Q

Developments in wind energy production: wind assisted ships

A

uses wind assisted propulsion
decreases fuel consumption

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40
Q

What type of energy is harnessed from waves?

A

KE
vertical movement

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41
Q

What factor produces large waves?

A

strong winds

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42
Q

What are the best sites to harness wave power?

A

far out at sea
areas of large fetch
open water

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43
Q

Wave energy technologies: point absorber

A

rises and falls as waves pass
attached to a base on the seabed
movement of floating part turns generator

44
Q

Wave energy technologies: overtopping device

A

waves force water into an above sea level storage reservoir
water flows back to the sea through a turbine, generating electricity

45
Q

Wave energy technologies: oscillating wave surge converter

A

waves move water cyclically
pushes a paddles which moves pistons that pump fluid over a turbine to generate electricity

46
Q

Wave energy technologies: surface attenuator

A

hinged floating device
moving sections push and pull pistons which force water over a turbine, generating electricity

47
Q

Wave energy technologies: oscillating water column

A

rise and fall of water forces water up and down in a submerged chamber
air that is forced in and out flows over turbines, generating electricity

48
Q

Advantages of wave power

A

high energy density compared to wind and solar
predictable
minimal land use
useful in isolated communities

49
Q

Disadvantages of wave power

A

high initial costs
disrupts marine ecosystems
limited locations
maintenance challenges
conflicts with fishing and shipping industries

50
Q

What crops are deliberately grown for their energy value as biofuels?

A

wood, elephant grass, corn, barley, rapeseed, palm

51
Q

How are biofuels best described?

A

carbon neutral

52
Q

Examples of waste materials used as biofuels

A

domestic and commercial = burned in an incinerator
anaerobic decomposition of DOM = produces methane

53
Q

Advantages of biofuels

A

reduced GHG emissions
increased energy security
waste reduction
compatible with existing infrastructure
easy to store and transport
abundant
predictable
high energy density

54
Q

Disadvantages of biofuels

A

land use competition
resource intensive
CO2 emissions when burned
impact on biodiversity due to monocultures
public opposition

55
Q

Where does geothermal energy come from?

A

radioactive decay of isotopes of thorium, uranium and potassium in the Earth’s mantle
residual heat from the formation of the solar systems
heat rises from within the earth and is transferred to the crust

56
Q

Geothermal low temperature schemes: geothermal springs

A

groundwater heated by hot rocks may come to the surface in hot springs

57
Q

Geothermal low temperature schemes: geothermal aquifers

A

hot groundwater pumped to the surface from aquifers

58
Q

Geothermal high temperature schemes: geothermal steam systems

A

hot groundwater brought to the surface using a borehole, producing steam = used to generate electricity by turning a turbine

59
Q

Geothermal high temperature schemes: hot dry rock systems

A

water is pumped down an injection borehole and steam is recovered using a second borehole
underground rocks are fractured to increase permeability and surface area for heat absorption

60
Q

What factors are needed to harness geothermal energy?

A

high temp schemes require tectonic activity

low temp schemes require large magma intrusions

61
Q

Advantages of geothermal power

A

low intermittency
predictable
low cost per unit of energy
easily converted to electricity
low technological advancements

62
Q

Disadvantages of geothermal power

A

local constraints (requires 150 degrees)
emits CO2 and hydrogen sulfide
waste water contains salts and heavy metals
difficult to transport
dangerous due to tectonic acitivty

63
Q

Geothermal: binary cycle power plant

A

hot groundwater passed through heat exchanger
heats secondary fluid and vaporises due to low BP
steam turns turbine, generating electricity
vapor is cooled and condensed
condensed fluid is pumped back into the heat exchanger to be heated again

64
Q

What causes the tides?

A

gravitational attraction between moon and earth creates tides

65
Q

How often are the tides?

A

2 high and 2 low every 25 hours

66
Q

What factors make harnessing tidal power viable?

A

harnessed at the coast
seabed topography
large intertidal range

67
Q

What can be done to increase the velocity of water?

A

direct water to a narrower channel

68
Q

Ways to harness tidal power: tidal barrages

A

dam across estuary or bay
water flows over/through it at high tide
opens at low tide and water flows through a turbine, generating electricity

69
Q

Ways to harness tidal power: tidal lagoons

A

surrounds a selected part of an estuary or bay
fills at high tide
water released at low tide, flowing over turbines

70
Q

Ways to harness tidal power: in-stream turbines

A

fixed to seabed
absorbs kinetic energy at high and low tide

71
Q

Advantages of tidal power

A

renewable
predictable
no GHG emissions
long lifespan
energy storage potential

72
Q

Disadvantages of tidal power

A

blocks shipping routes
migration barriers
expensive to build
intermittent
maintenance challenges

73
Q

New tidal technology: tidal reefs

A

not as tall as a tidal barrage
water flows over the reef to allow marine wildlife to move over it
tidal flow turns turbines to produce electricity

74
Q

What is a primary fuel?

A

natural resource that can be used directly for energy production

75
Q

Examples of primary fuels

A

coal, oil, gas, nuclear, biomass

76
Q

What is a secondary fuel?

A

an energy source that is derived from the processing or conversion of primary fuels

77
Q

How does a coal fired power station work?

A

pulverise coal
combust pulverised coal
heat produced used to convert water to steam
steam turns turbines connected to generator
steam is cooled and condensed, then pumped back into the system
scrubbers remove sulphur dioxide and electrostatic precipitators capture particulates

78
Q

What is a fuel cell?

A

a chemical battery

uses chemical energy to produce electricity

79
Q

What is the most common type of fuel cell?

A

hydrogen

80
Q

How does a fuel cell work?

A

hydrogen oxidised to H+
H+ move through partially permeable membrane, electrons forced to find alternative pathway, creating an electric current
H+ meet O2- to produce H2O
only waste = water

81
Q

What is peak shaving?

A

storing energy at a time of excess production for a later time of high demand

82
Q

How is electricity transported?

A

electricity generated
step-up transformer=increases voltage
electricity travels faster
travels through cables and pylons
step-down transformer
end user

83
Q

Advantages of using electricity

A

applicable to many uses
clean energy when generated by renewables
easily transported
allows for technological advancements
rapid energy delivery
scalability
reliable
no pollutants released upon use

84
Q

How is hydrogen produced by the electrolysis of water?

A

place electrodes in water
current splits water into H2 + O2
collect gases using an inverted container over the system
H2 is purified

85
Q

How can hydrogen be stored?

A

pressurised container
liquid hydrogen
metal hydrides
chemical storage
adsorption

86
Q

What problems are associated with the storage of hydrogen?

A

explosive
high cost
public opposition
large tanks due to low energy density
hydrogen causes materials to become brittle

87
Q

Ways of releasing chemical energy from hydrogen: combustion

A

used similarly to natural gas

pumped into an existing network

88
Q

Ways of releasing chemical energy from hydrogen: fuel cells

A

feed cell with hydrogen and oxygen
hydrogen loses electrons, becomes H+
H+ move through partially permeable membrane and combine with O2- to form water
electrons forced through alternative pathways, generating a current

89
Q

Why do we need to store energy?

A

balance supply and demand
save excess energy generated during peak production

90
Q

Causes in fluctuations in energy supply

A

variability of renewable energy sources
equipment failures
changes in demand

91
Q

Causes in fluctuations in energy demand

A

seasonal changes
daily patterns
holidays
population growth
increased energy efficiency

92
Q

How can we store energy?

A

batteries
pumped hydro storage
compressed air energy storage
flywheels
thermal energy storage
fuel cells

93
Q

Pumped storage: HEP

A

excess electricity used to pump water from the lower reservoir to the upper reservoir at times of low demand

stores energy at GPE

when demand increases, stored water is released back down to the lower reservoir, drives turbines that generate electricity

94
Q

Advantage of pumped storage

A

quickly responds to changes in demand

95
Q

Compressed gas storage

A

air is compressed using excess electricity and stored in high pressure tanks or underground caverns

released when demand increased, compressed air expands and drives turbines to generate electricity

effective for large scale energy storage

96
Q

Small scale rechargeable batteries

A

smartphones
laptops
electric vehicles
portable electronics
power tools

97
Q

Large scale rechargeable batteries

A

grid energy storage
frequency regulation
backup power
microgrids

98
Q

Disadvantages of the use of rechargeable batteries

A

limited lifespan
high cost
environmental impact
charging time
temperature sensitivity
performance degradation

99
Q

Types of storage systems: V2G systems

A

energy transfer between grid and vehicle batteries
all vehicles plugged into the grid when parked for an extended period of time
avoids cost and environmental impacts of power stations

100
Q

Types of storage systems: P2G systems

A

uses surplus electricity to produce gaseous fuel
water electrolysed to produce hydrogen
hydrogen used to produce methane, which is fed into the natural gas pipe network

101
Q

Types of storage systems: Heat energy

A

short-term storage of thermal energy
uses high thermal mass materials

102
Q

Types of storage systems: High volume storage

A

low SA:VOL, reduces heat loss
used for inter-season energy storage

103
Q

Types of storage systems: molten salt

A

stores heat from concentrated solar power photothermal systems
heat can be used later to boil water in a steam turbine power station

104
Q

Types of storage systems: high thermal mass buildings

A

constructed or material with a high thermal mass
reduces overheating during hot weather
reduces need for space heating in winter

105
Q

Types of storage systems: kinetic energy

A

temporary store of KE
used to drive machinery
generates electricity
e.g. flywheels

106
Q

Types of storage systems: electricity super capacitors

A

uses an electrochemical process
future applications of large scale electricity storage
creates a difference in charge, stop electrons flowing, electricity released when needed

Environmental Science (25 decks)

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