Electricity from Renewable Resources Status, Prospects, and Impediments (2010) / Chapter Skim
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5 Environmental Impacts of Renewable Electricity Generation
5 Environmental Impacts of Renewable Electricity Generation
Pages 195-240
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From page 195... ...
attempts to estimate the overall energy usage and environmental impact from the energy produced by a given technology by assess ing all the life stages of the technology: raw materials extraction, refinement, con struction, use, and disposal. Here, LCA is used to compare the relative impacts of various fossil-fuel-based and renewable sources of electricity.
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No LCA information is included for enhanced geothermal systems. The life-cycle impacts considered here include net energy usage; atmospheric emis sions of greenhouse gases expressed in units of carbon dioxide (CO2)
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Net Energy Ratio The NER is defined as the ratio of useful energy output to the grid to the fossilfuel energy consumed during the lifetime of the technology. As such, it is critical to assessing whether or not a renewable energy source reduces our use of fossil fuel.
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For wind and solar technolo gies, the location and the strength of the resource at that location also constitute an important variable. For example, a wind farm sited in a location with higher average wind speeds will generate more energy than will a wind farm sited at a 7.0 3.1 16.0 1.0 70 0.9 (with External Energy Ratio)
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Net energy ratios of 47 and 65 were reported for two large wind farms with higher-capacity turbines and higher average wind speeds. The NER for wind is very dependent on assumptions related to the frequency of blade and turbine replacement, because so much life-cycle energy is consumed in material manufacturing for this technology.
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From page 200... ...
In the LCA literature, the EPBT is most commonly applied to wind and PV technologies as an additional measure of the economic viability of these newer technologies. Wind EPBT of 0.26 and 0.39 years were reported for two large wind farms with higher-capacity turbines and higher average wind speeds (Schleisner, 2000)
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Since CO2 emission reductions depend on displacing fossil-fuel energy, this means that the greenhouse gas emissions reductions from using renewable energy may not be realized for quite some time after the deployment begins. On the other hand, in terms of greenhouse gas emissions, adding new capacity using
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emissions is a major driver in the push for use of renewable energy sources. This section reviews the LCAs of GHG or CO2e for relevant renewable and non-renewable sources of elec tricity.
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Environmental Impacts of Renewable Electricity Generation 0 80 60 Grams CO2 e/kWh 40 20 -1368 -248 0 –20 –40 Hydro Solar Tidal Wind Geothermal Biomass 1500 Average Maximum 1000 Energy Technology Minimum Grams CO2 e/kWh 500 0 –500 with CCS –1000 –1500 Hydro Solar Tidal Wind Geothermal Biomass Coal Gas Nuclear Storage BES Storage CAES Storage PHS Energy Technology FIGURE 5.4 Life-cycle emissions of greenhouse gases (in CO2 equivalents) for various sources of electricity. Average, maximum, and minimum emissions are shown for each R 5.4 technology based on a review of the literature. Note that the inset provides a smaller scale and more details for sources that are not distinguishable in the main figure. Note: Values for biomass, coal, and natural gas include data for carbon capture and storage (CCS)
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wind farm with 103 lower-capacity turbines (250 kW) located in an area with higher average wind speeds (Class 7)
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demonstrate that current technologies for storage are capable of overcoming the limitations of wind generation intermittency without significant carbon emissions. Geothermal The total for CO2e emissions from geothermal electricity generation incorporates the emissions associated with production of the facility and emissions during operation.
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Storage Storage is not a generating system, but it can be combined with generating tech nologies to provide backup power for intermittent and peak power needs. Stor age options reviewed in the LCA literature included pumped hydropower stor age, compressed air energy storage, and battery energy storage (BES)
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–10 Hydro Solar Wind Geothermal* Gas Nuclear 800 600 Energy Technology 400 200 0 Hydro Solar Wind Geothermal*
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PV installation with lower insolation rates and a greater reli ance on coal for electricity generation compared to that of Europe (Spitzley and Keoleian, 2005)
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Emissions of Nitrogen Oxides Figure 5.6 illustrates the range of life-cycle NOx emissions estimated from various electrical generation technologies. Among these technologies, hydroelectric, wind, geothermal, and nuclear technologies have low estimated NOx emissions (<100 mg/kWh)
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Nuclear 900 Average Maximum 800 Minimum 700 Energy Technology NOx (mg/kWh) 600 500 400 300 200 100 0 Hydro Solar Wind Geothermal*
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Biopower Of all the renewable electricity technologies, biopower can have the highest NOx emissions, with estimates ranging from 290 to 820 mg/kWh. Mann and Spath (1997)
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20 Average Maximum 1000 0 Minimum Hydro Wind Geothermal* Biomass Gas Nuclear 800 600 Energy Technology 400 200 0 Hydro Solar Wind Geothermal*
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12 10 600 8 Average 6 Land Use (m2 per MWh/yr) Maximum 500 Minimum 4 400 2 0 300 Coal Gas Nuclear Solar 200 Energy Technology 100 0 Hydro Solar Wind Biomass Coal Gas Nuclear Energy Technology FIGURE 5.8 Life-cycle cost assessment of land use for various renewable and non-renew able technologies in square meters per megawatt-hour per year. Note that the inset pro R 5.8 vides a smaller scale and more details for sources that are not distinguishable in the main figure. Source: Developed from data provided in Spitzley and Keoleian, 2005.
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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.g., PV instal lations on roofs or sides of buildings, wind turbines on farms, and hydroelectric reservoirs that provide flood control, recreation, and water supply)
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. Concentrated solar thermal power uses 770–920 gal/MWh, and solar power tower technologies use about 750 gal/MWh for evaporative cooling (DOE, 2006)
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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.
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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.
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Average 500 MW NGCC plant, cooling tower 2.2 million (2.8 million) Power Plant Withdrawal-Consumption Mining Withdrawal-Consumption Power Plant Consumption Mining/Processing Other Power Plant Use Nuclear Coal IGCC NGCC Geo Hydro Solar 25,000 60,000 20,000 50,000 7,500 20,000 4,500 3,000 Gallons per Megawatt-hour Equivalent 2,500 2,000 1,500 1,000 500 S 0 Once-through low Cooling tower low Cooling pond low Once-through high Cooling tower high Cooling pond high Once-through low Tower low Cooling tower low Cooling pond low Once-through high Cooling tower high Cooling pond high Tower high Once-through low Cooling tower low Once-through high Cooling tower high Cooling tower Evaporation Thermal low Thermal high Power tower Dish engine FIGURE 5.9 Estimates of water withdrawal and consumption rates for various thermo electricity generating technologies. R 5.9 Source: DOE, 2006.
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In Cape Cod, Massachusetts, local residents who fear harm to aquatic life have fought the construction of 130 wind turbines; in southern California, advocates of solar power face resistance from environmental groups that fear potential disruption to the Mojave Desert ecosystem (Barringer, 2009)
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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, 2008)
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; Subpart J–Essential Fish Habitat; Subpart K–EFH coordination, consultation, and recommendations Fish and wildlife Fish and Wildlife Coordination Act No implementing regulations (FWCA)
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, Sections 106 and 110: 36 CFR Part 800 P.L. 89-665, as amended; 16 USC 470 Native American graves Native American Graves Protection Native American Graves Protection and Repatriation Act (NAGPRA)
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An example of a state handbook on wind power per mitting is the guidance developed by the Kansas Energy Council for siting wind power projects in that state (Kansas Energy Council, 2005)
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. In order to better assess possible wildlife impacts of wind power, Secretary of the Interior Dirk Kempthorne in 2007 announced the creation of the Wind Turbine Guidelines Advisory Committee, which will function in accordance with the Federal Advisory Committee Act (FACA)
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In California, CSP plants greater than 50 MW in size require approvals from both the BLM and the CEC. 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.
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. • WindPotential climatic and meteorological perturbations, especially in the vicinity of large wind farms; noise pollution; aesthetic impacts; and bird and bat deaths (Keith et al., 2004; NRC, 2007; Morrison and Sinclair, 2004; GAO, 2005)
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Renewable electricity generation also involves inherently low or zero direct emissions of other regulated atmo spheric pollutants, such as sulfur dioxide, nitrogen oxides, and mercury. Biopower is an exception because it produces NOx emissions at levels similar to those asso
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also consume significantly less water and have much smaller impacts on water quality than do nuclear, natural gas-, and coal-fired electricity generation technologies. Because of the diffuse nature of renewable resources, the systems needed to capture energy and generate electricity (i.e., wind turbines and solar panels and concentrating systems)
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2003. Net Energy Balance and Greenhouse Gas Emissions from Renewable Energy Storage System.
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2002. Greenhouse gas emissions from a hydroelectric reservoir (Brazil's Tucurui Dam)
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2004. Wind energy technology, environmental impacts of.
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2002. Greenhouse gas emissions from building and operating electric power plants in the Upper Colorado River Basin.
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1998. Net Energy Payback and CO2 Emissions from Helium-3 Fusion and Wind Electrical Power Plants.
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(This case and the next seven all have the same assumptions for the following parameters: solar insolation of 1700 kWh/m2 per yr, performance ratio of .8, 30 yr lifetime. Did not include a case with crystal-clear project energy mix (natural gas and hydroelectric)
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. 7 European Commission 1997d.
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LCA includes plant construction and decaying biomass from reservoir. A Brazilian reservoir is mentioned that due to very large size and low generation capacity has an estimated CO2e of 237 (Fearnside's estimate is even higher)
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Supercritical pulverized coal (same as above)
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Excludes primary electricity generation. Based on a 2.7 GW proposed facility in Ohio.
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VRB 75%, PSB 63%, Pb-acid 66% efficient. 32.6 PSB 40.2 V redox Note: a-Si, amorphous silicon; BES, battery energy storage; CAES, compressed air energy storage; CCS, carbon capture and storage; CIGS, copper indium gallium selenide; FGC, flue gas clean-up; FGD, flue gas desulphurization; LEBS, low emission boiler system; mc-Si, multicrystalline silicon; MEA, monoethanolamine; PB-acid, lead acid; pc-Si, polycrystalline silicon; PHS, pumped hydro storage; PSB, sodium-bromide/sodium-polysulfide battery; sc-Si, single-crystalline silicon; SCR, selective catalytic reduction; T&D, transmission and distribution; V redox, vanadium acid; VRB, vanadium redox battery.
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