Environmental impact of electricity generation

Electric power systems consist of generation plants of different energy sources, transmission networks, and distribution lines. Each of these components can have environmental impacts at multiple stages of their development and use including in their construction, during the generation of electricity, and in their decommissioning and disposal. These impacts can be split into operational impacts (fuel sourcing, global atmospheric and localized pollution) and construction impacts (manufacturing, installation, decommissioning, and disposal). The United States Environmental Protection Agency clearly states that all forms of electricity generation have some form of environmental impact.[1] The European Environment Agency view is the same.[2] This page looks exclusively at the operational environmental impact of electricity generation. The page is organized by energy source and includes impacts such as water usage, emissions, local pollution, and wildlife displacement.

More detailed information on electricity generation impacts for specific technologies and on other environmental impacts of electric power systems in general can be found under the Category:Environmental impact of the energy industry.

Water usage

Water usage is one of the main environmental impacts of electricity generation.[3] All thermal cycles (coal, natural gas, nuclear, geothermal, and biomass) use water as a cooling fluid to drive the thermodynamic cycles that allow electricity to be extracted from heat energy. Other energy sources such as wind and solar use water for cleaning equipment, while hydroelectricity has water usage from evaporation from the reservoirs. The amount of water usage is often of great concern for electricity generating systems as populations increase and droughts become a concern. In addition, changes in water resources may impact the reliability of electricity generation.[4] The power sector in the United States withdraws more water than any other sector and is heavily dependent on available water resources. According to the U.S. Geological Survey, in 2005, thermo-electric power generation water withdrawals accounted for 41 percent of all freshwater withdrawals or 760 million m3 (201 billion US gal) per day. Nearly all of the water withdrawn for thermoelectric power was surface water used for once-through cooling at power plants. Withdrawals for irrigation and public supply in 2005 were 37% and 13% of all freshwater withdrawals respectively.[5] Likely future trends in water consumption are covered here.[6]

Discussions of water usage of electricity generation distinguish between water withdrawal and water consumption.[4] According to the USGS, "withdrawal" is defined as the amount of water removed from the ground or diverted from a water source for use, while "consumption" refers to the amount of water that is evaporated, transpired, incorporated into products or crops, or otherwise removed from the immediate water environment.[5] Both water withdrawal and consumption are important environmental impacts to evaluate.

General numbers for fresh water usage of different power sources are shown below.

  Water Consumption (gal/MW-h)
Power source Low case Medium/average case High case
Nuclear power 100 (once-through cooling) 270 once-through, 650 (tower and pond) 845 (cooling tower)
Coal 58 [7] 500 1,100 (cooling tower, generic combustion)
Natural gas 100 (once-through cycle) 800 (steam-cycle, cooling towers) 1,170 (steam-cycle with cooling towers)
Hydroelectricity 1,430 4,491 18,000
Solar thermal 53 (dry cooling)[8] 800[8] 1,060 (Trough)[8]
Geothermal 1,800 4,000
Biomass 300 480
Solar photovoltaic 0 26 33
Wind power 0[4] 0[4] 1[4]

Steam-cycle plants (nuclear, coal, NG, solar thermal) require a great deal of water for cooling, to remove the heat at the steam condensers. The amount of water needed relative to plant output will be reduced with increasing boiler temperatures. Coal- and gas-fired boilers can produce high steam temperatures and so are more efficient, and require less cooling water relative to output. Nuclear boilers are limited in steam temperature by material constraints, and solar thermal is limited by concentration of the energy source.

Thermal cycle plants near the ocean have the option of using seawater. Such a site will not have cooling towers and will be much less limited by environmental concerns of the discharge temperature since dumping heat will have very little effect on water temperatures. This will also not deplete the water available for other uses. Nuclear power in Japan for instance, uses no cooling towers at all because all plants are located on the coast. If dry cooling systems are used, significant water from the water table will not be used. Other, more novel, cooling solutions exist, such as sewage cooling at the Palo Verde Nuclear Generating Station.

Hydroelectricity's main cause of water usage is both evaporation and seepage into the water table.

Reference: Nuclear Energy Institute factsheet using EPRI data and other sources.

Electricity industry (incl. gas & liquid fuels) value chain – water consumption,[9] LCA emission intensity & capacity factor
Feedstock/ fuel/ resource Raw material production
L/MW·h
[L/GJ]		 Fermentation/ processing/refining
L/MW·h
[L/GJ]		 Electricity generation with closed-loop cooling Total water consumption
L/MW·h[9]		 CO2 -eq
kg/MW·he
 SO2
kg/MW·h
 NOx
kg/MW·h
 H2S
kg/MW·h
 Particulate
kg/MW·h
 Cd
mg/MW·h
 Hg
mg/MW·h
 On-site accidents
deaths/TW·yr
 Average capacity factor
%
Traditional oil 10.8–25.2
[3–7]		 90–234
[25–65]		 1,200~ 1,300.8–1,459.2 893[10] 814[11] 43.3[12] 9[13] 60~[14]
Enhanced oil recovery 180-32,400
[50-9,000]		 90–234
[25–65]		 1,200~ 1,470–33,834 893[10] 814[11] 43.3[12] 9[13] 60~[14]
Oil sands 252-6,480*
[70-1,800*]		 90–234
[25–65]		 1,200~ 1,542–7,914 893[10] 814[11] 43.3[12] 9[13] 60~[14]
Biofuels:
corn		 32,400–360,000
[9,000–100,000]		 169.2–180
Ethanol:[47-50]		 1,200~ 33,769.2–361,380 893~[10] 814~[11] 9~[13] 52~[10]
Biofuels:
soybean		 180,000–972,000
[50,000–270,000]		 50.4
Biodiesel:[14]		 1,200~ 181,250.4–973,250.4 893~[10] 814~[11] 9~[13] 52~[10]
Coal 20–270
[5–70]		 504–792
-to-liquids:[140-220]		 200-2,000[7] Coal-to-liquids:N.C.
220-2,270		 B:863–941
Br:1175[15]		 4.71[11] 1.95[11] 0[11] 1.01[11] H:3.1-
L:6.2[12]		 14-
61[13][16]		 342[17] 70–90[14]
Traditional gas Minimal 25.2
[7]		 700 725.2 577:cc[15]
(491–655)		 550[11] 0.2[12] 0.1-
0.6[16]		 85[17] 60~[14]
Natural gas:
shale gas		 129.6–194.4
[36–54]		 25.2
[7]		 700 854.8–919.6 751:oc[15]
(627–891)		 550[11] 0.2[12] 0.1-
0.6[16]		 85[17] 60~[14]
U nuclear 170–570 See:Raw Material 2,700 2,870–3,270 60–65 (10–130)[15] 0.5[12] 8[17] 86.8[18]-92[14]
Hydroelectric 17,000:Evap.Avg 17,000 15[15] 0.03[12] 883[17] 42[10]
Geothermal power Fresh:0–20[11]
5,300		 Fresh:0–20[11]
5,300		 TL0–1[10]
TH91–122		 0.16[11] 0[11] 0.08[11] 0[11] 73-90+[10]
Conc. solar 2,800–3,500 2,800–3,500 40±15# 56.2–72.9[19]
Photovoltaics Minimal Minimal 106[15] 0.3–0.9[12] 14[10]-19[20]
Wind power Minimal Minimal 21[15] 271[21] 21[10]-40[20][22]
Tidal power Minimal 55,917.68[23] 26.3[23] 0.0622[23] 0.159[23] 0.032[23] 46[23]
Feedstock/ fuel/ resource Raw material production
L/MW·h
[L/GJ]		 Fermentation/ processing/refining
L/MW·h
[L/GJ]		 Electricity generation with closed-loop cooling L/MW·h Total water consumption
L/MW·h[9]		 CO2-eq
kg/MW·he		 SO2
kg/MW·h		 NOx
kg/MW·h		 H2S
kg/MW·h		 Particulate
kg/MW·h		 Cd
mg/MW·h		 Hg
mg/MW·h		 Lethal on-site accidents
deaths/TW·yr		 Average capacity factor
%

Source(s): Adapted from US Department of Energy, Energy Demand on Water Resources. Report to Congress on the Interdependence of Energy and Water, December 2006 (except where noted).
*Cambridge Energy Research Associates (CERA) estimate. #Educated estimate.
Water Requirements for Existing and Emerging Thermoelectric Plant Technologies. US Department of Energy, National Energy Technology Laboratory, August 2008.
Note(s): 3.6 GJ = gigajoule(s) == 1 MW·h = megawatt-hour(s), thus 1 L/GJ = 3.6 L/MW·h. B = Black coal (supercritical)-(new subcritical), Br = Brown coal (new subcritical), H = Hard coal, L = Lignite, cc = combined cycle, oc = open cycle, TL = low-temperature/closed-circuit (geothermal doublet), TH = high-temperature/open-circuit.

Fossil fuels
Main article: Fossil fuel
See also: Environmental impact of the oil shale industry

Most electricity today is generated by burning fossil fuels and producing steam which is then used to drive a steam turbine that, in turn, drives an electrical generator.

More serious are concerns about the emissions that result from fossil fuel burning. Fossil fuels constitute a significant repository of carbon buried deep underground. Burning them results in the conversion of this carbon to carbon dioxide, which is then released into the atmosphere. The estimated CO2 emission from the world's electrical power industry is 10 billion tonnes yearly.[24] This results in an increase in the Earth's levels of atmospheric carbon dioxide, which enhances the greenhouse effect and contributes to global warming.[25]

Depending on the particular fossil fuel and the method of burning, other emissions may be produced as well. Ozone, sulfur dioxide, NO2 and other gases are often released, as well as particulate matter.[26] Sulfur and nitrogen oxides contribute to smog and acid rain. In the past, plant owners addressed this problem by building very tall flue-gas stacks, so that the pollutants would be diluted in the atmosphere. While this helps reduce local contamination, it does not help at all with global issues.

Fossil fuels, particularly coal, also contain dilute radioactive material, and burning them in very large quantities releases this material into the environment, leading to low levels of local and global radioactive contamination, the levels of which are, ironically, higher than a nuclear power station as their radioactive contaminants are controlled and stored.

Coal also contains traces of toxic heavy elements such as mercury, arsenic and others. Mercury vaporized in a power plant's boiler may stay suspended in the atmosphere and circulate around the world. While a substantial inventory of mercury exists in the environment, as other man-made emissions of mercury become better controlled, power plant emissions become a significant fraction of the remaining emissions. Power plant emissions of mercury in the United States are thought to be about 50 tons per year in 2003, and several hundred tons per year in China. Power plant designers can fit equipment to power stations to reduce emissions.

According to Environment Canada:

"The electricity sector is unique among industrial sectors in its very large contribution to emissions associated with nearly all air issues. Electricity generation produces a large share of Canadian nitrogen oxides and sulfur dioxide emissions, which contribute to smog and acid rain and the formation of fine particulate matter. It is the largest uncontrolled industrial source of mercury emissions in Canada. Fossil fuel-fired electric power plants also emit carbon dioxide, which may contribute to climate change. In addition, the sector has significant impacts on water and habitat and species. In particular, hydro dams and transmission lines have significant effects on water and biodiversity."[27]

Coal mining practices in the United States have also included strip mining and removing mountain tops. Mill tailings are left out bare and have been leached into local rivers and resulted in most or all of the rivers in coal producing areas to run red year round with sulfuric acid that kills all life in the rivers.

The efficiency of some of these systems can be improved by co-generation and geothermal (combined heat and power) methods. Process steam can be extracted from steam turbines. Waste heat produced by thermal generating stations can be used for space heating of nearby buildings. By combining electric power production and heating, less fuel is consumed, thereby reducing the environmental effects compared with separate heat and power systems.

Switching from fuels to electricity
These paragraphs are an excerpt from Electrification § Electrification for sustainable energy.[edit]

As clean energy is mostly generated in the form of electricity, such as renewable energy or nuclear power, a switch to these energy sources requires that end uses, such as transport and heating, be electrified for the world's energy systems to be sustainable.

It is easier to sustainably produce electricity than it is to sustainably produce liquid fuels. Therefore, adoption of electric vehicles is a way to make transport more sustainable.[28] Hydrogen vehicles may be an option for larger vehicles which have not yet been widely electrified, such as long distance lorries.[29] Many of the techniques needed to lower emissions from shipping and aviation are still early in their development.[30]

A large fraction of the world population cannot afford sufficient cooling for their homes. In addition to air conditioning, which requires electrification and additional power demand, passive building design and urban planning will be needed to ensure cooling needs are met in a sustainable way.[31] Similarly, many households in the developing and developed world suffer from fuel poverty and cannot heat their houses enough.[32] Existing heating practices are often polluting.

A key sustainable solution to heating is electrification (heat pumps, or the less efficient electric heater). The IEA estimates that heat pumps currently provide only 5% of space and water heating requirements globally, but could provide over 90%.[33] Use of ground source heat pumps not only reduces total annual energy loads associated with heating and cooling, it also flattens the electric demand curve by eliminating the extreme summer peak electric supply requirements.[34] However, heat pumps and boilers alone will not be sufficient for the electification of the industry. This because in several processes higher temperatures are required which cannot be achieved with these types of equipment. For example, for the production of ethylene via steam cracking temperatures as high as 900°C are required. Hence, drastically new processes are required. Nevertheless, power-to-heat is expected to be the first step in the electification of the industry with an expected large-scale implementation by 2025.[35]

In order to reduce greenhouse gas emissions, environmental advocates propose transitioning entirely away from natural gas for cooking and heating, replacing it with electricity generated from renewable sources. Some cities in the United States have started prohibiting gas hookups for new houses, with state laws passed and under consideration to either require electrification or prohibit local requirements.[36] The UK government is experimenting with electrification for home heating to meet its climate goals.[37] Ceramic and Induction heating for cooktops as well as industrial applications (for instance steam crackers) are examples of technologies that can be used to transition away from natural gas.[38]

Nuclear power
The Onagawa Nuclear Power Plant – a plant that cools by direct use of ocean water, not requiring a cooling tower
Main article: Environmental effects of nuclear power
See also: Nuclear power debate

Nuclear power plants do not burn fossil fuels and so do not directly emit carbon dioxide; because of the high energy yield of nuclear fuels, the carbon dioxide emitted during mining, enrichment, fabrication and transport of fuel is small when compared with the carbon dioxide emitted by fossil fuels of similar energy yield. However, these plants still produce other environmentally damaging wastes.[39] Pressurized heavy water reactors like the Canadian CANDU or the Indian IPHWR do not need enriched fuel and can operate using natural uranium. This allows better use of the energy contained in the initial uranium ore (while higher enrichment allows higher burnup, the amount of natural uranium needed to produce this fuel increases faster than the achievable burnup)[40] and reduces the energy needed in fuel manufacturing as the conversion of the yellowcake to uranium hexafluoride and back into an oxide fuel as well as the energy-intensive enrichment process can be skipped.

A large nuclear power plant may reject waste heat to a natural body of water; this can result in undesirable increase of the water temperature with adverse effect on aquatic life. Alternatives include cooling towers and use of the waste heat for district heating.[41] As district heating has a seasonal demand curve it is often only a seasonal solution of the waste heat problem. Furthermore district heating is less efficient in less densely populated areas and as nuclear power plants are often constructed far out of population centers due to NIMBY and safety concerns, the usage of nuclear district heating hasn't been widespread.[42] As most commercial nuclear power plants are incapable of online refueling and need periodic shutdowns to exchange spent fuel elements for fresh fuel, many operators schedule this unavoidable downtime for the peak of summer when rivers tend to run lower and the issue of waste heat potentially harming the fluvial environment is most acute.[43] This is especially pronounced in France which produces some 70% of electricity with nuclear power plants and where electric home heating is very widespread. However, in regions with high HVAC power use, the summer season rather than imposing lower power demands may be the peak season of electricity demand complicating scheduled summer shutdowns. Waste heat can also be used for district cooling via absorption refrigeration but this is even less common than nuclear district heating.

Emission of radioactivity from a nuclear plant is controlled by regulations. Abnormal operation may result in release of radioactive material on scales ranging from minor to severe, although these scenarios are very rare.[44] In normal operation nuclear power plants release less radioactive material than coal power plants whose fly ash contains significant amounts of thorium, uranium and their daughter nuclides.[45]

Mining of uranium ore can disrupt the environment around the mine. However with modern in-situ leaching technology this impact can be reduced compared to "classical" underground- or open-pit mining. Disposal of spent nuclear fuel is controversial, with many proposed long-term storage schemes under intense review and criticism. Nuclear reprocessing and breeder reactors which can decrease the need for storage of spent fuel in a deep geological repository have faced economic and political hurdles but are in some use in Russia, India, China Japan and France, which are among the countries with the highest nuclear energy production outside the United States. The U.S. however hasn't undertaken significant efforts towards either reprocessing or breeder reactors since the 1970s instead relying on the once through fuel cycle. Diversion of fresh- or low-burnup spent fuel to weapons production presents a risk of nuclear proliferation, however all nuclear weapons states derived the material for their first nuclear weapon from (non-power) research reactors or dedicated "production reactors" and/or uranium enrichment. Finally, some parts the structure of the reactor itself becomes radioactive through neutron activation and will require decades of storage before it can be economically dismantled and in turn disposed of as waste. Measures like reducing the Cobalt content in steel to decrease the amount of Cobalt-60 produced by neutron capture can reduce the amount of radioactive material produced and the radiotoxicity that originates from this material.[46][47] However, part of the issue is not radiological but regulatory as most countries assume any given object that originates from the "hot" (radioactive) area of a nuclear power plant or a facility in the nuclear fuel cycle is ipso facto radioactive, even if no contamination or neutron irradiation induced radioactivity is detectable.

Renewable energy

Renewable power technologies can have significant environmental benefits. Unlike coal and natural gas, they can generate electricity and fuels without releasing significant quantities of CO2 and other greenhouse gases that contribute to climate change, however the greenhouse gas savings from a number of biofuels have been found to be much less than originally anticipated, as discussed in the article Indirect land use change impacts of biofuels.

Both solar and wind have been criticized from an aesthetic point of view.[48] However, methods and opportunities exist to deploy these renewable technologies efficiently and unobtrusively: fixed solar collectors can double as noise barriers along highways, and extensive roadway, parking lot, and roof-top area is currently available; amorphous photovoltaic cells can also be used to tint windows and produce energy.[49] Advocates of renewable energy also argue that current infrastructure is less aesthetically pleasing than alternatives, but sited further from the view of most critics.[50]

Hydroelectricity
Main article: Hydroelectricity § Advantages_and_disadvantages

The major advantage of conventional hydroelectric dams with reservoirs is their ability to store potential power for later electrical production. The combination of a natural supply of energy and production on demand has made hydro power the largest source of renewable energy by far. Other advantages include longer life than fuel-fired generation, low operating costs, and the provision of facilities for water sports. Some dams also operate as pumped-storage plants balancing supply and demand in the generation system. Overall, hydroelectric power can be less expensive than electricity generated from fossil fuels or nuclear energy, and areas with abundant hydroelectric power attract industry.

However, in addition to the advantages above, there are several disadvantages to dams that create large reservoirs. These may include: dislocation of people living where the reservoirs are planned, release of significant amounts of carbon dioxide at construction and flooding of the reservoir, disruption of aquatic ecosystems and bird life, adverse impacts on the river environment, potential risks of sabotage and terrorism, and in rare cases catastrophic failure of the dam wall.

Some dams only generate power and serve no other purpose, but in many places large reservoirs are needed for flood control and/or irrigation, adding a hydroelectric portion is a common way to pay for a new reservoir. Flood control protects life/property and irrigation supports increased agriculture. Without power turbines, the downstream river environment would improve in several ways, however dam and reservoir concerns would remain unchanged.

Small hydro and run-of-the-river are two low impact alternatives to hydroelectric reservoirs, although they may produce intermittent power due to a lack of stored water.

Tidal
Further information: Tidal power § Environmental concerns
Tidal turbines

Land constrictions such as straits or inlets can create high velocities at specific sites, which can be captured with the use of turbines. These turbines can be horizontal, vertical, open, or ducted and are typically placed near the bottom of the water column.

The main environmental concern with tidal energy is associated with blade strike and entanglement of marine organisms as high speed water increases the risk of organisms being pushed near or through these devices. As with all offshore renewable energies, there is also a concern about how the creation of EMF and acoustic outputs may affect marine organisms. Because these devices are in the water, the acoustic output can be greater than those created with offshore wind energy. Depending on the frequency and amplitude of sound generated by the tidal energy devices, this acoustic output can have varying effects on marine mammals (particularly those who echo-locate to communicate and navigate in the marine environment such as dolphins and whales). Tidal energy removal can also cause environmental concerns such as degrading far-field water quality and disrupting sediment processes. Depending on the size of the project, these effects can range from small traces of sediment build up near the tidal device to severely affecting nearshore ecosystems and processes.[51]

Tidal barrage

Tidal barrages are dams built across the entrance to a bay or estuary that captures potential tidal energy with turbines similar to a conventional hydrokinetic dam. Energy is collected while the height difference on either side of the dam is greatest, at low or high tide. A minimum height fluctuation of 5 meters is required to justify the construction, so only 40 locations worldwide have been identified as feasible.

Installing a barrage may change the shoreline within the bay or estuary, affecting a large ecosystem that depends on tidal flats. Inhibiting the flow of water in and out of the bay, there may also be less flushing of the bay or estuary, causing additional turbidity (suspended solids) and less saltwater, which may result in the death of fish that act as a vital food source to birds and mammals. Migrating fish may also be unable to access breeding streams, and may attempt to pass through the turbines. The same acoustic concerns apply to tidal barrages. Decreasing shipping accessibility can become a socio-economic issue, though locks can be added to allow slow passage. However, the barrage may improve the local economy by increasing land access as a bridge. Calmer waters may also allow better recreation in the bay or estuary.[51]

Biomass
Further information: Biomass § Environmental impact

Electrical power can be generated by burning anything which will combust. Some electrical power is generated by burning crops which are grown specifically for the purpose. Usually this is done by fermenting plant matter to produce ethanol, which is then burned. This may also be done by allowing organic matter to decay, producing biogas, which is then burned. Also, when burned, wood is a form of biomass fuel.[52]

Burning biomass produces many of the same emissions as burning fossil fuels. However, growing biomass captures carbon dioxide out of the air, so that the net contribution to global atmospheric carbon dioxide levels is small.

The process of growing biomass is subject to the same environmental concerns as any kind of agriculture. It uses a large amount of land, and fertilizers and pesticides may be necessary for cost-effective growth. Biomass that is produced as a by-product of agriculture shows some promise, but most such biomass is currently being used, for plowing back into the soil as fertilizer if nothing else.

Wind power
Main article: Environmental effects of wind power

Onshore wind

Wind power harnesses mechanical energy from the constant flow of air over the surface of the earth. Wind power stations generally consist of wind farms, fields of wind turbines in locations with relatively high winds. A primary publicity issue regarding wind turbines are their older predecessors, such as the Altamont Pass Wind Farm in California. These older, smaller, wind turbines are rather noisy and densely located, making them very unattractive to the local population. The downwind side of the turbine does disrupt local low-level winds. Modern large wind turbines have mitigated these concerns, and have become a commercially important energy source. Many homeowners in areas with high winds and expensive electricity set up small wind turbines to reduce their electric bills.

A modern wind farm, when installed on agricultural land, has one of the lowest environmental impacts of all energy sources:[53]

  • It occupies less land area per kilowatt-hour (kWh) of electricity generated than any other renewable energy conversion system, and is compatible with grazing and crops.
  • It generates the energy used in its construction within just months of operation.
  • Greenhouse gas emissions and air pollution produced by its construction are small and declining. There are no emissions or pollution produced by its operation.
  • Modern wind turbines rotate so slowly (in terms of revolutions per minute) that they are rarely a hazard to birds.[53]

Landscape and heritage issues may be a significant issue for certain wind farms. However, when appropriate planning procedures are followed, the heritage and landscape risks should be minimal. Some people may still object to wind farms, perhaps on the grounds of aesthetics, but there is still the supportive opinions of the broader community and the need to address the threats posed by climate change.[54]

Offshore wind

Offshore wind is similar to terrestrial wind technologies, as a large windmill-like turbine located in a fresh or saltwater environment. Wind causes the blades to rotate, which is then turned into electricity and connected to the grid with cables. The advantages of offshore wind are that winds are stronger and more consistent, allowing turbines of much larger size to be erected by vessels. The disadvantages are the difficulties of placing a structure in a dynamic ocean environment.[51]

The turbines are often scaled-up versions of existing land technologies. However, the foundations are unique to offshore wind and are listed below:

Monopile foundation

Monopile foundations are used in shallow depth applications (0–30 m) and consist of a pile being driven to varying depths into the seabed (10–40 m) depending on the soil conditions. The pile-driving construction process is an environmental concern as the noise produced is incredibly loud and propagates far in the water, even after mitigation strategies such as bubble shields, slow start, and acoustic cladding. The footprint is relatively small, but may still cause scouring or artificial reefs. Transmission lines also produce an electromagnetic field that may be harmful to some marine organisms.[51]

Tripod fixed bottom

Tripod fixed bottom foundations are used in transitional depth applications (20–80 m) and consist of three legs connecting to a central shaft that supports the turbine base. Each leg has a pile driven into the seabed, though less depth is necessary because of the wide foundation. The environmental effects are a combination of those for monopile and gravity foundations.[51]

Gravity foundation

Gravity foundations are used in shallow depth applications (0–30 m) and consist of a large and heavy base constructed of steel or concrete to rest on the seabed. The footprint is relatively large and may cause scouring, artificial reefs, or physical destruction of habitat upon introduction. Transmission lines also produce an electromagnetic field that may be harmful to some marine organisms.[51]

Gravity tripod

Gravity tripod foundations are used in transitional depth applications (10–40 m) and consist of two heavy concrete structures connected by three legs, one structure sitting on the seabed while the other is above the water. As of 2013, no offshore windfarms are currently using this foundation. The environmental concerns are identical to those of gravity foundations, though the scouring effect may be less significant depending on the design.[51]

Floating structure

Floating structure foundations are used in deep depth applications (40–900 m) and consist of a balanced floating structure moored to the seabed with fixed cables. The floating structure may be stabilized using buoyancy, the mooring lines, or a ballast. The mooring lines may cause minor scouring or a potential for collision. Transmission lines also produce an electromagnetic field that may be harmful to some marine organisms.[51]

Ecological Impact of Wind Energy

One large environmental concern of wind turbines is the impact on wildlife. Wind turbines and their associated infrastructure – notably power lines and towers – are among the fastest-growing threats to birds and bats in the United States and Canada. Bird and bat deaths often occur when the animals collide with the turbine blades.[55] They are also harmed by collisions and electrocutions with transmission lines. Even though siting of wind energy plants are thoroughly reviewed before construction, they can be a cause of habitat loss.

There is also concern of how wind energy impacts weather and climate change. Although wind energy could have the least amount of contribution to climate change, compared to other electricity generators, it still has some room for improvement. Wind turbines can impact the weather of its close vicinity, affecting temperature and rainfall.[56] There are also studies suggesting that large scale wind farms could increase local temperatures if built on land, while reducing local temperature if built on water. Using wind turbines to meet 10 percent of global energy demand in 2100 could cause local temperatures to rise by one degree Celsius in the regions on land where the wind farms are installed, while decreasing by one degree Celsius in regions where wind farms are installed over water. This effect is a change in redistribution of heat due to changed wind patterns, not a general increase of global temperature. The study is a simulation based on increased friction and the writer recommends further research to investigate if the effect actually exist.[57]

Geothermal power
Main article: Geothermal power

Geothermal energy is the heat of the Earth, which can be tapped into to produce electricity in power plants. Warm water produced from geothermal sources can be used for industry, agriculture, bathing and cleansing. Where underground steam sources can be tapped, the steam is used to run a steam turbine. Geothermal steam sources have a finite life as underground water is depleted. Arrangements that circulate surface water through rock formations to produce hot water or steam are, on a human-relevant time scale, renewable.

While a geothermal power plant does not burn any fuel, it will still have emissions due to substances other than steam which come up from the geothermal wells. These may include hydrogen sulfide, and carbon dioxide. Some geothermal steam sources entrain non-soluble minerals that must be removed from the steam before it is used for generation; this material must be properly disposed. Any (closed cycle) steam power plant requires cooling water for condensers; diversion of cooling water from natural sources, and its increased temperature when returned to streams or lakes, may have a significant impact on local ecosystems.

Removal of ground water and accelerated cooling of rock formations can cause earth tremors. Enhanced geothermal systems (EGS) fracture underground rock to produce more steam; such projects can cause earthquakes. Certain geothermal projects (such as one near Basel, Switzerland in 2006) have been suspended or canceled owing to objectionable seismicity induced by geothermal recovery.[58] However, risks associated with "hydrofracturing induced seismicity are low compared to that of natural earthquakes, and can be reduced by careful management and monitoring" and "should not be regarded as an impediment to further development of the Hot Rock geothermal energy resource".[59]

Solar power
Main article: Solar power

Between 2010 and 2020 the installation cost per kilowatt of solar photovoltaic power dropped by 85% and is since among the cheapest alternatives for new power generation in many regions. Also without any financial support, it undercuts the cost of the cheapest new coal alternatives.[60] Photovoltaic power is more cost efficient, as one might expect, in areas where sunlight is abundant.

Solar photovoltaic power works by converting the sun's radiation into direct current (DC) power by use of photovoltaic cells. This power can then be converted into the more common AC power and fed to the power grid.

Its negative impact on the environment lies in the creation of the solar cells which are made primarily of silica (from sand) and the extraction of silicon from silica may require the use of fossil fuels, although newer manufacturing processes have eliminated CO2 production. Solar power carries an upfront cost to the environment via production, but offers clean energy throughout the lifespan of the solar cell.

Large scale electricity generation using photovoltaic power requires a large amount of land, due to the low power density of photovoltaic power. Land use can be reduced by installing on buildings and other built up areas, though this reduces efficiency.

Concentrated solar power
Main article: Concentrated solar power

Also known as solar thermal, this technology uses various types of mirrors to concentrate sunlight and produce heat. This heat is used to generate electricity in a standard Rankine cycle turbine. Like most thermoelectric power generation, this consumes water. This can be a problem, as solar powerplants are most commonly located in a desert environment due to the need for sunlight and large amounts of land. Many concentrated solar systems also use exotic fluids to absorb and collect heat while remaining at low pressure. These fluids could be dangerous if spilled.[61]

Negawatt power
Main article: Negawatt power

Negawatt power refers to investment to reduce electricity consumption rather than investing to increase supply capacity. In this way investing in Negawatts can be considered as an alternative to a new power station and the costs and environmental concerns can be compared.

Negawatt investment alternatives to reduce consumption by improving efficiency include:

  • Providing customers with energy efficient lamps – low environmental impact
  • Improved thermal insulation and airtightness for buildings – low environmental impact
  • Replacing older industrial plant – low environmental impact. Can have a positive impact due to reduced emissions.

Negawatt investment alternatives to reduce peak electrical load by time shifting demand include:

  • Storage heaters – older systems had asbestos. Newer systems have low environmental impact.
  • Demand response control systems where the electricity board can control certain customer loads – minimal environmental impact
  • Thermal storage systems such as ice storage systems to make ice during the night and store it to use it for air conditioning during the day – minimal environmental impact
  • Pumped storage hydroelectricity – can have a significant environmental impact – see Hydroelectricity
  • other Grid energy storage technologies – impact varies

Note that time shifting does not reduce total energy consumed or system efficiency; however, it can be used to avoid the need to build a new power station to cope with a peak load.

See also

References
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