More study is needed of the impact of flooded biomass on life-cycle emissions associated with hydroelectric plants. No LCA data were reviewed for tidal or wave electricity-generating technologies, which are still very much in the pilot or demonstration stage. One would expect LCA emissions to be low and to occur primarily during material manufacturing and plant construction.
Storage is not a generating system, but it can be combined with generating technologies to provide backup power for intermittent and peak power needs.
Storage options reviewed in the LCA literature included pumped hydropower storage, compressed air energy storage, and battery energy storage BES Denholm and Kulcinski, ; Denholm, No data on SO 2 emissions were found for tidal or energy storage technologies.
Rates of SO 2 emissions associated with electricity generation from PV are most affected by the energy intensity of the manufacturing process and the efficiency of the PV material, as well as the energy mix used to manufacture the PV material and the solar insolation at the site where the PV is installed. PV installation with lower insolation rates and a greater reliance on coal for electricity generation compared to that of Europe Spitzley and Keoleian, Fthenakis et al.
Interestingly, studies suggest that the most efficient PV material is not necessarily the best for minimizing emissions. For example, cadmium telluride CdTe technologies have the lowest conversion efficiencies 9 percent yet produce lower SO 2 emissions because less energy is consumed during CdTe manufacturing than with other PV technologies that have higher conversion efficiencies This relationship may change as technology innovations decrease energy consumption during manufacturing.
Mann and Spath suggest that much of this variation arises from differences in power plant efficiency. Cases with results in the mid-range include two hypothetical integrated gasification combined cycle IGCC plants with different fuels. The other U. As a rule, energy sources based on combustion have significantly higher levels of NO x emissions than do those that do not involve combustion.
The NO x produced from combustion arises from two sources: the oxidation and volatilization of the nitrogen contained in the fuel, and the high-temperature reactions involving atmospheric nitrogen and oxygen. The production of NO x from atmospheric sources can be reduced or even completely eliminated by carrying out the combustion under high-oxygen conditions, so-called oxy-fuel combustion. Because of a lack of LCAs, the levels of NO x emissions described here do not reflect the performance of these systems.
SO 2 and NO x emission results cited here have been corrected to be consistent with Heller et al. This range largely reflects the differing mixes of grid energy used to produce the PV material as well as the conversion efficiencies and life expectancies of the PV facility.
PV installation with lower insolation; the greater reliance on coal for electricity generation in the United States as compared to Europe leads to greater life-cycle emissions in the United States Spitzley and Keoleian, A study by Fthenakis et al. They compared — PV technologies for similar systems using the average U.
Mann and Spath found that NO x emissions are most sensitive to variations in crop yield, feedstock fuel used, and power plant efficiency, and that most NO x emissions in the biopower life cycle about 70 percent are from combustion. Whether the feedstock is a fossil fuel or is biomass, the amount of NO x produced during combustion depends on the nitrogen content of the fuel and the temperature of combustion. The higher the temperature, the more NO x is produced.
As a result, production of electricity from biopower produces NO x at rates comparable to that of fossil fuels. No LCA data on emissions of particulate matter were found for geothermal, tidal, or energy storage technologies. Only one, a U. PV installation with lower insolation rates and a relatively large reliance on coal in electricity from the grid. Some have proposed that land use may be a limiting factor for the use of renewable energy technologies Pimentel et al.
Other studies have focused on one aspect of an energy technology e. These estimates of land use can be misleading because they fail to present an accurate understanding of the entire life-cycle land-use requirements of a technology. The LCA land-use data discussed here are from Spitzley and Keoleian , whose land-use metric accounts for the total surface area occupied by the materials and products of an energy technology, including the time of land occupation over the total life-cycle energy generated.
Source: Developed from data provided in Spitzley and Keoleian, Key assumptions in the Spitzley and Keoleian analysis are 1 exclusion of fuels and materials with insignificant land acquisition requirements compared to other life-cycle stages, and 2 inclusion of end-of-life land disposal requirements for nuclear fuel only.
The Spitzley and Keoleian analysis does not allow for distinctions for intensity of land use. A key factor affecting land use is the generating efficiency of the technology per unit area.
By design, technologies using high energy density power sources use less land to produce more electricity at the point of generation than do the more diffuse renewable technologies. For this reason, analyses such as the ones cited here find that renewables have relatively large land-use requirements.
To operate fossil-fuel and nuclear plants, however, the fuel must first be extracted or mined. Most LCAs, including those used in this study, do not account for that process in their assessment of land-use requirements.
Moreover, the land used by some diffuse renewable electricity technologies usually allows for multiple uses, or the technology makes use of sites that also serve an alternate purpose e. Of the renewable energy technologies, solar has the lowest land-use values, ranging from 9 to The lowest estimated value for PV is for an installation in Phoenix where higher insolation rates yield more energy potential per unit area. The lower land-use value is from the wind farm with higher wind speed and reflects the greater power generation potential per unit area and per unit of equipment.
Additionally, only about 1 percent of wind farm land is used by the turbines and associated facilities, thus allowing for multiple uses e. The literature also contains a wide range of non-LCA land-use data for hydroelectric power.
The range includes very small values for run-of-river hydroelectric facilities to very. The highest value is from a direct-fired boiler biopower facility with a small generating capacity. All four examples cited in the Spitzley and Keoleian study use cropping to supply biomass. Biopower from waste would be expected to have much lower land-use values. Although most renewable technologies use only a fraction of the water used by thermoelectric plants, some renewables, such as geothermal, hydroelectric, and solar thermal, can be water intensive.
For example, flash geothermal plants consume reservoir water and require makeup water. This facility uses water recycled from a wastewater facility as an innovative makeup water source DOE, Newer geothermal plant designs such as binary plants use little water.
Hydroelectric power, which generates electricity from the kinetic energy of water itself, uses vast quantities of water. CSP technologies can also be water intensive see Table 5. Parabolic dish-engine solar technologies are air-cooled and use minimal water DOE, Energy technologies that withdraw and consume less water will have both public benefit and economic advantages in the marketplace moving forward. One option is to develop electricity from sources that use very little water, such as wind and PV.
Other options include developing technologies that limit the use of water with fossil-fuel electricity sources or use alternate sources of water, such as reclaimed or saline water. Makeup water is the water added to the existing flow of cooling water to replace the water lost during passage through the cooling towers or other power plant processes. Other alternative sources of water include produced water from oil and gas operations and brackish groundwater aquifers.
Developing alternate water sources requires careful consideration of economic and ecosystem impacts. For example, brackish groundwater requires additional conditioning to meet power plant water chemistry specifications. At the same time, groundwater withdrawals can affect freshwater aquifers and lead to saltwater intrusion. Relying on marine water has the same impacts for fish and other aquatic organisms as freshwater use.
Generating electricity from energy technologies that rely on water to produce electricity from steam thermoelectric generation is very water-intensive. In recent years, concerns regarding water use have led to the denial of water permits for new power plant construction in various locations throughout the United States Feeley III et al.
In areas of the United States experiencing. The benefits of present and future water use by energy technologies must be carefully weighed in examining the implications of a finite water resource. Competition over water is intensifying, because water supports agricultural, industrial, and domestic needs, as well as the need for electricity.
Thermoelectric plants generate electricity using steam from a variety of fuel sources including fossil fuels, geothermal energy, concentrated solar power, and biopower. However, most thermoelectric power in the United States is generated from conventional fossil sources. Water use by thermoelectric power plants is categorized as water withdrawn or consumed.
Thermoelectric power plants use large quantities in each category but withdraw more than is actually consumed. According to the U. This accounted for about 40 percent of all freshwater withdrawals in the United States, and almost 15 percent of all non-agricultural consumption. However, Dziegielewski et al. They reported that water-use data for thermoelectric power plants compiled by the USGS did not include water from public water supplies, nor was it clear whether water use by independent non-utility power plants was included.
Independent non-utility power plants generated an additional 16 percent of electricity in On average, approximately 26 gallons of water is used to produce 1 kWh of electricity. Total per capita water withdrawals for electricity in amounted to gallons per person per day, which is about four and a half times the direct per capita use Table 5.
Power plants use water primarily for cooling, but significant quantities of water are also used in other plant activities. Because of this dependency, power plants have traditionally been sited near rivers, lakes, or oceans. Most of the water consumed by thermoelectric power plants is lost through evaporation.
Cooling system options include once-through, recirculating, or air-cooled systems. Water use by thermoelectric technologies with these cooling options is shown in Table 5.
TABLE 5. It is critical to consider siting and permitting issues. The permitting process addresses the wide range of localized impacts that might result from the construction of a renewables facility or related infrastructure, such as transmission lines.
New renewable electric facilities can affect water supplies, ecosystems, and the natural landscape and hence can meet with local opposition. Though renewable facilities are obtaining permits and completing impact assessments, the knowledge of the full impacts of renewables and the guidance for permitting projects are nascent in comparison to those for fossil fuels.
Further, renewable energy resources are generally more distributed than concentrated, especially those powering the technologies dominating the near term wind power, solar PV, and CSP. As noted previously, renewables have relatively large land-use requirements.
The process of siting and permitting these facilities has the potential to place burdens on local jurisdictions that regulate land use and create a hodgepodge of rules and requirements for renewable energy deployment. Siting issues could be a significant concern with renewables. The NIMBY not in my back yard effect, which describes local opposition to a new development intended to distribute broad benefits, has delayed the construction of several major renewable energy projects in the United States.
While proponents cite the environmental, economic, and energy security benefits to be gained from these projects, opponents cite the negative impacts, which often include potential damage to local ecosystems, loss of aesthetic value to the natural landscape, and the opportunity cost of land use. Biomass and biofuels, for example, require large amounts of land that could instead be used for agricultural purposes.
Hydropower is becoming increasingly difficult to site; most major potential sites are already being used, and ecological considerations are preventing the exploitation of remaining ones. Siting renewable energy projects can also pit environmentalists against one another. In Cape Cod, Massachusetts, local residents who fear harm to aquatic life have fought the construction of wind turbines; in southern California, advocates of solar power face resistance from environmental groups that fear potential disruption to the Mojave Desert ecosystem Barringer, Local opposition has also stymied the development of new transmission lines Silverstein, Review of siting issues occurs during the permitting process discussed below.
Most if not all technologies for generating electricity will require multiple permits. These permits are intended to consider the local impacts on the land, water, and air that occur during the installation and operation of these technologies. Depending on the size and location of the generating facility, permits from local zoning boards, state agencies, and federal agencies may be required.
In the case of traditional electricity-generating facilities, such as those that use coal and natural gas, there is a long and evolving permitting process that has been applied across the country.
For most renewable technologies, the process is more in the developmental stage. As of January , at least two states, California and Wisconsin, have enacted state laws preempting or limiting local siting jurisdiction for wind power Green, Because wind power has been the most extensively deployed renewable electricity technology in recent times, guidance for permitting a wind power project is more advanced. For biomass, geothermal, and solar, the guidance for permitting is less well developed.
However, there are many current regulations that apply to all generating facilities. Although an exhaustive review of local impacts and permitting issues is beyond the scope of this study, a short summary of permitting issues for wind, geothermal, and CSP is presented below. Due to the increasing number of wind power projects, more information is being developed concerning the process for permitting them. The most prominent issues of concern are land use and the possible impacts on birds and bats.
In addition, concerns have been raised about noise, aesthetics, and the use of herbicides to clear and maintain sites, particularly where endangered species are involved.
Recent reports and references on permitting wind power projects include the American Wind Energy Association AWEA siting handbook, which presents information about regulatory and environmental issues associated with developing and siting wind energy projects in the United States AWEA, The AWEA handbook covers the components of a typical wind power project: the stages of a wind power project; the federal, state, and local regulatory frameworks relevant for wind power; and the array of environmental and human impacts to consider.
Source: U. An example of a state handbook on wind power permitting is the guidance developed by the Kansas Energy Council for siting wind power projects in that state Kansas Energy Council, In terms of impacts on wildlife, the New York State Department of Environmental Conservation recently proposed guidelines on how to characterize bird and bat resources at onshore wind energy sites and how to estimate and document impacts New York Department of Environmental Conservation, Although bird deaths are often characterized as one critical potential impact from wind turbines, the NRC study cited above concluded that, while the impacts on bat populations were unclear, there was no evidence that bird fatalities caused by wind turbines result in measurable demographic changes to bird populations in the United States NRC, One purpose of the NRC study was to develop an analytical framework for impact evaluation to inform siting decisions for wind-energy projects.
The NRC study found that because wind energy is new to many state and local governments, the quality of the permitting process is uneven, and it pointed out that a coordinated and consistent process would greatly aid planning and regulating wind-energy development at smaller scales. The report recommended that representatives of federal, state, and local governments work with wind developers and interested parties to develop guidance and permitting guidelines NRC, The scope and objective of the committee, as outlined in its charter, is to provide advice and recommendations to the Interior secretary on developing effective measures to avoid or minimize impacts on wildlife and habitats related to land-based wind energy facilities.
The committee members represent the varied interests associated with wind energy development and wildlife management. Another group that will address fauna issues is the recently formed American Wind Wildlife Institute, created through cooperation between members of the environmental community and the wind industry.
The institute will focus on efforts to facilitate timely and responsible development of wind energy while protecting wildlife and wildlife habitat. It will do this through research, mapping, mitigation, and public education on best practices in wind farm siting and wildlife-habitat protection. Because of the long history of geothermal hydrothermal projects in the western United States, there is a mature record of the permitting of these plants.
Battocletti provides an overview of the geothermal permitting process. Most federal statutes listed in Table 5. Because much of the geothermal resources occur on lands managed by the U.
California has its own geothermal permitting requirements, which are issued by the California Energy Commission CEC, Permitting for CSP plants falls under general requirements for utility-scale solar projects. At present, CSP plants are the only utility-scale solar plants that have been built. Figure 2. As with geothermal energy, BLM manages much of this land and must issue permits for these plants. Because of concerns about the potentially large land resources needed for CSP projects, the BLM recently announced that it would produce a programmatic environmental impact statement to evaluate the environmental, social, and economic impacts associated with the applications for solar energy development on BLM-managed public land BLM, The announcement also called for a moratorium on the acceptance of any new applications for CSP development on BLM lands, but this policy was rescinded.
To provide joint National Environmental Protection Act and California Environmental Quality Act review and a more efficient process, the BLM and the California Energy Commission have entered into a memorandum of understanding that contains projects of joint jurisdiction and provides a timeline for the joint review process.
However, the Department of Energy, in conjunction with the Departments of Commerce and the Interior, is studying these issues at the request of the U. Congress 8 and will issue a report that is scheduled for publication in July The goal of that report is to address the potential effects of marine and hydrokinetic energy projects, options to prevent adverse impacts, and potential roles and components for environmental monitoring and adaptive management.
For the pur-. The report will not address energy from impoundments or other diversionary structures. Given the scarcity of real operational data, the report will not constitute a definitive impact assessment but will highlight areas of potential concern and areas of research and monitoring necessary to gain needed data.
A wide spectrum of other environmental impacts are not addressed by LCA and are not discussed here. They are nevertheless of potential importance and, in some particular locations, can include the impact that raises the greatest concern on the part of local populations and regulators. For example, all large power plants and transmission corridors require large tracts of land that must be kept at least partially clear of unwanted vegetation to maintain security, operational performance, and access for maintenance.
To the extent that herbicides are used to clear and maintain areas for such sites, localized impacts will occur. Other technology-specific impacts associated with the use of renewable sources of electricity include the following:.
Hydroelectric— Ecosystem changes including impacts on fish migration and mortality, habitat damage, degradation of water quality, and loss of sediment transport to delta systems Goodwin et al. Wind— Potential climatic and meteorological perturbations, especially in the vicinity of large wind farms; noise pollution; aesthetic impacts; and bird and bat deaths Keith et al.
Biopower— Ground and surface water pollution from fertilizers and depletion of water for irrigation cultivated biomass ; removal of organic material from soil waste biomass Marland and Obersteiner, Geothermal— Metals arsenic and gas H2S from power plant operations, groundwater and surface water pollution, and potential for land subsidence and induced seismicity DiPippo, Energy is essential for modern life as we know it, and all energy use implies environmental impacts upstream of the point at which work is done.
These impacts range widely in locus, intensity, and significance depending on the primary source of the energy and means used to deliver and convert it into useful work.
Understanding of these impacts has improved with advancements in environmental sciences and in analytical processes used to assess present and future environmental impacts. Armed with better analytical tools and a greater appreciation of the systematic and long-term impacts of energy resource decisions, the basic question we face regarding environmental impacts, then, is the extent to which the continuation of impacts is acceptable to society, and more importantly, how the evaluation and consideration of potential environmental impacts should influence the policy that affects energy resource decisions.
Renewable electricity technologies have inherently low life-cycle CO 2 emis sions as compared to fossil-fuel-based electricity production, with most emissions occurring during manufacturing and deployment.
Along with water pollution, natural resources can be maintained and greenhouse effect and air pollution can be mitigated by the proper usage of renewable energy sources [ 23 ] as shown in Table 4. Carbon dioxide emission with the generation of electric power using different energy resources is given in Figure 2.
Summary of environmental effects [ 24 ]. Carbon dioxide equivalent emission during power generation [ 7 ]. Various greenhouse gases in atmosphere is being increased by humankind by doing many economic activities.
The role of greenhouse gases and current situation are given in Table 5. Role of different substances in greenhouse effect [ 15 ].
Solar panels are usually installed at the roofs of the buildings that increase the job opportunities in the PV system fabrication and installation. This increases the regional development and reduces the usage of energy from nonrenewable energy projects. It is very useful at the regions where there is no access of electricity.
The major problem with solar system is the high investment and maintenance cost. Biomass energy projects have great contribution in the local job creation and the development of rural areas. Such types of power plants have large opportunities of jobs in construction of plants, management, maintenance of plants, production, and preparation of biomass. Only the noise production and unpleasant smell are the negative impacts of these plants.
Fuel cells have slow implementation because of their high cost of plant construction and energy generation. Their construction and operation create jobs in almost all technical activities. In hydro power plants, the major sociopolitical problem is the shifting of the people from the areas where the plant is going to be constructed.
These plants provide significant jobs for local community and also play an important role in the economic development of the community. The construction of tidal energy plants has no effect on humans, and they have better contribution in the local and official employment. These plants are very expensive and are not common. Wind energy projects do not have any emigration problem, and they create large number of job opportunities especially for engineers.
Geo thermal energy projects provide the following sociopolitical benefits: improvement in the education of local people, improvement in living standards, and improvement in the care of health issues [ 25 ].
When the solar panels are connected to the distribution system, the cost of safety equipment is reduced because their short circuit current is higher than the nominal value. Biomass power plants have the same effects on the gird as do conventional plants.
The integration of wind energy plants, tidal energy, and geothermal energy is complex [ 25 ]. Three case studies were made to investigate the socioeconomic benefits of renewable energy projects, and the three cases were solar, wind, and biofuel energy projects; empirical method was used to collect data.
The basic aim of study was to know the contribution of renewable energy projects to local sustainability, which includes social, economic, and environmental, and to identify the socioeconomic benefits of REPs through the concerned community. It was done by doing survey of the communities. Eleven parameters were used including job creation, impacts on education, easy usage of energy, income development, demographic impacts, social bonds creation and community development, usage of native resources, and tourism.
They concluded that the impacts of REPs on employment are positive, and indirect employment is high in comparison with the size of community, whereas direct employment is moderate [ 26 ]. One of the important assessing factors to generate power from renewable energy sources is the availability and their technical limitation. Each resource has some limitations; photovoltaic has limitation to generate power only because heat energy from sun can only be received during the day time, except cloudy season.
Geothermal has good ability to generate power throughout the day for 24 h but is geography limited according to the presence of resources. Hydro-electric power plants are easy to start, stop, and operate within minutes; hence, they are considered as one of the highest available, reliable, and flexible renewable energy resources. From efficiency point of view, hydroelectric is classified at the top of the list, and then wind energy, photovoltaic, and geothermal are lowest efficient renewable energy resources.
Because of availability of cells in different categories, the efficiency of photovoltaic is very much variable [ 7 ]. According to the efficiency, different energy sources are categorized in Table 6. Efficiency of electricity generation [ 7 ]. The conventional energy resources like oil, gas, and coal are very important for the improvement in economics of a country. When the impacts on land use are measured simply by the surface area they occupy during their life cycle, some renewable energy technologies appear to have heavy land-use requirements Figure However, this approach does not take into account the intensity of land use or whether the technology allows for simultaneous use of land for other purposes.
Whereas coal-fired power plants fully occupy the sites where they are constructed, small-scale PV installations may be placed on rooftops where they cause little or no interference with the. Thus, smaller scale or distributed solar technologies may have less of an impact on land use and habitat loss than large-scale, central station plants.
Land-use concerns may also be addressed by deploying renewable energy systems on previously developed sites, rather than in undeveloped areas Mosey et al. The high land-use requirements for biopower shown in Figure assume that the feedstocks have been cultivated for energy production; if waste biomass is used as the feedstock, the land-use impacts are significantly lower. In China, the biomass materials likely to be used for electricity generation are mainly agricultural residues e.
Plants grown for energy are expected to comprise a very small proportion of biopower feedstocks in China. The potential of waste resources available in China is estimated at about million tons of coal equivalent Tce , equivalent to about 14 percent of total Chinese energy consumption in Incremental land-use requirements for using waste materials as biopower feedstocks are insignificant.
Moreover, if not used for biopower, some waste resources, such as municipal solid waste, would otherwise occupy land and could cause environmental damage if not disposed of properly. The hydropower estimate shown in Figure represents land use for the Glen Canyon Dam and Lake Powell, attributing the full area of the reservoir to electricity generation Spitzley and Keoleian, ; in contrast, small-scale hydropower and run-of-the river installations would have minimal land-use requirements.
Land-use requirements for electrical transmission and distribution lines and facilities, which are significant for all centralized electricity generating facilities, are not shown in Figure Water is a scarce resource in large portions of the United States and China. Recent global circulation model projections suggest that, if climate change proceeds as expected, under current business-as-usual scenarios, freshwater supplies will become even scarcer in some parts of the United States Milly et al.
In China, the amount of water available per capita is 2, m 3 , only a quarter of the world per capita average. Water supply problems in China have been exacerbated because the spatial distribution of water is very uneven. Electricity production using thermoelectric technologies requires vast amounts of water, primarily for cooling. In the United States, about 43 percent of existing thermoelectric generating capacity uses once-through cooling, 42 percent uses recirculating wet towers, 15 percent uses recirculating cooling ponds, and 1 percent uses dry cooling Feeley et al.
Water use by power plants is characterized by withdrawals the total amount of water taken from a source and consumption the amount of water not returned to the source.
Although consumption is sometimes emphasized over withdrawals, the latter is important, because power plant operation may be constrained by the amount of water available for withdrawal and power plant uses may compete with other demands for water Gleick, Furthermore, water returns can be significant sources of thermal pollution and may include discharges of chemical pollutants, such as chlorine or other biocides used in cooling towers.
The U. Geological Survey estimates that nearly billion cubic meters BCM of water was withdrawn in for thermoelectric power generation in the United States, accounting for nearly half of total withdrawals USGS, Water consumption by thermoelectric facilities in the United States is much lower, an estimated 4 BCM in estimates for are not available , but this quantity nevertheless constitutes more than 15 percent of U.
Water use by thermoelectric plants in China is also huge. In , the quantity of withdrawals was 49 BCM, accounting for 37 percent of total industrial use. Chinese thermoelectric plants consumed an estimated 7 BCM of water. Water consumption by geothermal plants depends on the technology and geothermal resource, as well as the cooling system.
The balance of water, for recharging the reservoir, comes from secondary-treated wastewater from a nearby community DiPippo, Water consumption in liquid-dominated binary geothermal systems can be very high if wet cooling towers are used, but can be much lower if hybrid or air-cooled systems are used.
Wind and solar PV technologies use very little water. Water-use requirements for solar thermal plants also depend on the cooling system. Finally, if evaporative losses from hydroelectric reservoirs are ascribed fully to the generation of electricity, large-scale hydroelectric power can be considered to consume more water per MWh electricity output than any other electricity generation technology Gleick, However, reservoirs associated with hydroelectric power plants may have other uses, such as storage of irrigation water.
Thus, evaporative losses may not be exclusively attributable to electricity generation. Although thin-film cadmium telluride and amorphous-silicon technologies are gaining ground in the global marketplace, most PV panels produced today are made of single or multicrystalline silicon.
As discussed in Appendix D , in China, the production of high-purity polysilicon for solar cells is a rapidly growing industry, although it has high energy requirements and serious pollution problems at some facilities. To minimize these impacts, polysilicon manufacturers in China, as elsewhere, must use state-of-the-art methods to reduce energy consumption and address problems with hazardous materials and wastes.
In response to these environmental concerns, especially the need to separate and recycle tail gas, China has initiated a key research project on the comprehensive use of by-products from polysilicon production. As indicated above, although life cycle impacts of solar PV are estimated to be much lower than those of electricity generation from fossil fuels, the estimated NER and emissions impacts of PV are somewhat less favorable than for wind technology.
The main reason is that production of PV panels is very energy intensive, with significant associated emissions of CO 2 , NO x , and other air pollutants. Estimates of energy requirements for silicon PV panel manufacturing vary widely, depending in part on the vintage of the manufacturing technology and in part on the sources of process heat and electricity required. Alsema reported that estimates published up to that time ranged from 2, to 7, MJ m -2 for.
To illustrate the distribution of energy requirements among the steps in the process, Figure shows a breakdown for manufacturing of multicrystalline silicon PV modules, beginning with the production of metallurgical-grade M-g silicon. The fractions shown are adapted from estimates by Alsema and Alsema and de Wild-Scholten Whereas Alsema and de Wild-Scholten assumed electricity for polysilicon production was supplied from a mixture of hydroelectric and natural gas combined-cycle generation, the modified results shown here were calculated assuming electricity used at all stages in the process was produced from primary fuel with a net conversion efficiency of 31 percent.
The overall estimate of the energy requirement is in the middle of the range cited by Alsema The results show the importance of electricity used at the silicon-purification stage. If the silicon is purified using inefficient processing technology, electricity is supplied from relatively inefficient power plants, or polycrystalline silicon is wasted in wafer production steps, energy requirements can easily exceed those shown.
By the same token, at some production facilities, the fossil energy required for polycrystalline silicon production has been greatly reduced by process improvements,.
Adapted from estimates provided by Alsema and Alsema and de Wild-Scholten The process of manufacturing PV panels also entails the use, or by-product production, of a number of hazardous materials that must be monitored, handled, and disposed of properly to minimize risks to workers, the public, and the environment.
In addition to SiCl 4 , these substances include silane, a highly flammable intermediate of polysilicon production, and hydrofluoric acid HF and other toxic gases and acids used in cleaning silicon wafers and in texturing and etching. Large amounts of acidic and alkaline wastewater are produced, so wastewater treatment and acid recycling are also critical steps. Fluoride in wastewater poses special problems, because an excessive amount of fluoride in drinking water can cause a variety of diseases.
Thus, strict standards are necessary to regulate the treatment and discharge of water containing HF. These issues are discussed in more detail in Appendix D , where research for reducing environmental and health and safety issues associated with polysilicon manufacturing are highlighted. Renewable energy facilities, like other means of electricity production, can have significant environmental and socio-cultural impacts.
For renewable technologies, these impacts are often, but not always, similar to or milder than the effects of other industrial development on a similar scale. Nonetheless, locating renewable energy projects in sensitive areas can make the environmental licensing of the project difficult and more costly, and so these project-scale impacts can affect the rate of deployment. Among renewable electricity technologies, large-scale hydroelectric projects have historically had especially stark consequences, especially if they involved flooding scenic valleys or town sites.
For example, when the Dalles Dam on the Columbia River was completed in , the associated reservoir flooded Celilo Falls and the village of Celilo, a tribal fishing area and cultural center that archeologists estimated had been inhabited for millennia Oregon Historical Quarterly, Like other dams on the Columbia River, the Dalles Dam serves multiple purposes, including improved navigation, irrigation, flood control, and the generation of nearly 1, MW of electricity.
Although the Dalles Dam has provided. Since the Dalles Dam was completed, a web of U. These include the Wilderness Act, which prohibits activities that damage the character of wilderness in specified areas, the Wild and Scenic Rivers Act, which bans construction of dams and associated hydroelectric projects on protected stretches of rivers, and the National Environmental Policy Act NEPA , which requires that environmental reviews be completed with full opportunities for public input before federal actions are taken.
In part because of these protections, the pace of large-scale reservoir construction in the United States has slowed dramatically since the s, and most new U. At the same time, however, as plans for utility-scale wind and solar projects move forward in the United States, advocates will have to take great care in siting and designing projects and operations that minimize environmental and social costs.
A case in Hawaii is another example of controversy surrounding the siting of renewable energy projects in locations of natural, cultural, or religious value. In , Hawaiians celebrated the protection of a 26, acre tract of lowland rainforest on the island of Hawaii, after more than 20 years of efforts to restore public access and block the development of a geothermal power plant at the site OHA, In the late s, True Geothermal Energy Co.
Native Hawaiians opposed the development because they traditionally used the area for hunting and gathering and for religious purposes.
Some native Hawaiians also objected to the exploitation of geothermal resources in general because of reverence for Pele, the goddess of volcanoes in the native Hawaiian religion. The Wao Kele O Puna geothermal project was abandoned in Most transmission lines are above ground on large towers.
The towers and power lines alter the visual landscape, especially when they pass through undeveloped areas. Vegetation near power lines may be disturbed and may have to be continually managed to keep it away from the power lines. These activities can affect native plant populations and wildlife. Power lines can be placed underground, but it is a more expensive option and usually not done outside of urban areas.
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