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| − | === 7. Environmental Aspects of Grid Interconnection ===
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| − | == 7.1. Introduction == | + | = Overview<ref>Much of the text in this Chapter was adapted from D. F. Von Hippel and J. H. Williams (2003), Environmental Issues for Regional Power Systems in Northeast Asia. Prepared for the Third Workshop on Northeast Asia Power Grid Interconnections, September 30 - October 3, 2003, Vladivostok, Russian Federation , and dated 12/2003. Available as http://nautilus.org/archives/energy/grid/2003Workshop/Env_Issues_DVH_JW_final_pdf.PDF.</ref> = |
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| − | Construction and operation of transmission grid interconnections, and the power plants that feed them, have impacts—both positive and negative—on the local, and sometimes regional and global environments. In addition, transmission grid interconnections will affect the generation of electricity in the receiving country, and also, possibly, the production and use of other fuels. Evaluating and accounting the full-fuel-cycle environmental impacts of grid interconnections is an important element of the overall process of evaluating grid interconnection opportunities. Impacts and benefits may occur at any or all points in the fuel chain, from extraction of fuels for electricity generation, to construction and operation of plants and construction and operation of transmission facilities. Environmental considerations have sometimes received less emphasis in energy planning in general than technical, economic, and (often) political issues. In the case of grid interconnections in developing regions, however, the early consideration of environmental impacts in evaluating interconnection options will help to identify key potential problems—including sensitive ecosystems to be traversed by the power lines—as well as potential opportunities that could enhance the interconnection project—including credits for avoided air pollutant and greenhouse gas emissions115. | + | Construction and operation of transmission [[Portal:Grid|grid]] interconnections, and the power plants that feed them, have impacts (both positive and negative) on the local, and sometimes regional and global environments. In addition, transmission grid interconnections will affect the generation of electricity in the receiving country, and also, possibly, the production and use of other fuels. |
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| − | == 7.2. Overview of Potential Environmental Benefits and Costs of Grid Interconnections ==
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| − | Most of the potential classes of environmental benefits of grid interconnections are treated in more detail in later sections of this Chapter. A brief listing of these benefits and impacts is presented here by way of an introduction to the variety of environmental issues that should be considered. • Air pollutant emissions including local air pollutants, regional air pollutants (such as the precursors of acid precipitation and some particulate emissions), and greenhouse gases. Modest quantities of emissions may be produced during power line construction, but the main influence of grid interconnections on air pollutant emissions will be through the impact of transmission interconnections on which power plants are run where and when in the interconnected nations. Major air pollutant emission benefits therefore accrue overall (counting all the countries in the interconnection project) if the emissions from the generation that is used with the interconnection in place is less than the emissions that would have been produced in the absence of the interconnection. Where hydroelectric generation, for example, provides export power through an interconnection and displaces existing or planned fossil-fueled power plants in the importing country, net emissions benefits will occur in most cases. The net air pollutant emissions benefits or costs for individual countries depend on which power plants run more, or less, in the presence of the interconnection, and where those plants are located. • Water pollution impacts, including erosion and water pollutants produced as a result of power line construction and operation, and incremental water pollution from power plant construction, power generation, and fuel extraction/storage. As with air pollutant emissions, on a net basis, overall water pollution impacts can show either a net cost or a net benefit for the interconnection project as a whole, or for the different countries and localities involved, depending on the specifics of how the project is configured, and what would energy facilities would have been built and operated had the interconnection not been built. • Solid waste impacts, mainly coal ash and high- and low-level nuclear wastes from electricity generation, but also including wastes from fuel extraction and possibly from power line and/or power plant construction. Net solid waste benefits accrue to the project mostly if coal-fired power is displaced by hydro, renewable, or gas-fired power, which net solid waste costs will occur, overall, if coal-fired plants are built to fuel the production of power exported over the interconnection. • Land-use impacts, including costs such as the restriction of uses of land through which a power line passes, and benefits such as potential avoided land-use impacts from electricity generation or fuel extraction facilities avoided by the use of an interconnection. • Wildlife/biodiversity impacts, including costs such as the potential impacts of power line construction and operation on flora and fauna in the power line area, and benefits such as potential avoided impacts due to avoided generation and fuel extraction. • Human health impacts, including the impacts of electromagnetic fields (EMFs) from power lines on humans living and working in the power line vicinity (net costs of the interconnection project), and benefits through avoided human health impacts through avoided air and water pollution. As is clear from even these brief discussions of classes of impacts, international electricity grid interconnections offer the potential for impacts at each different part of the fuel cycle. The full range of fuel cycle steps at which environmental benefits and costs of an interconnection project can occur—through impacts caused by the interconnection net of impacts avoided by the project relative to other means of providing the same energy services as the interconnection—include construction of the power line and related infrastructure, operation of the power line, construction and operation for the power plants feeding the grid interconnection (or plants that are avoided by the use of the line), impacts related to fuel supplies for power plants, and impacts related to power plant wastes.
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| − | == 7.3. Potential Air Pollution Impacts of Grid Interconnections == | + | = Evaluating and Accounting Impacts = |
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| − | Grid interconnections may, depending on how they are configured, create or avoid (or both) air pollution impacts as a result of their operation. The following subsections provide a review of the potential local, regional, and global air pollution impacts and benefits from grid interconnections, summarize how the net air pollutant emissions or emissions savings (and their impacts) of an interconnection might be assessed, and briefly presents potential strategies for maximizing air pollution benefits of a grid interconnection. Detailed evaluation of air pollution impacts at each of these scales can be extremely complex, and many reports and, indeed, entire volumes, projects, and analytical tools have been dedicated to the evaluation of air pollutant emissions and impacts116. The brief treatment below is therefore intended only as an overview, to be considered as a generic structure underpinned by much more detailed work in the field by a number of authors117. Consideration of the net impacts of grid interconnections on air pollution involves consideration of net emissions of in several pollutant classes and over the range of emissions sources that comprise the full electricity generation/transmission/distribution fuel cycle. The type, timing, and location of pollutant emissions need to be considered, as all of these elements play a role in determining the impacts of emissions. Even a transmission interconnection that yields the same emissions, relative to a no-interconnection alternative, can offer significant benefits if the power plants that run more to feed power to the interconnection are far from population centers and/or sensitive environmental areas, and the power plants that are operated less because the interconnection is used are located near population centers. For analytical purposes, one way to divide the different types of air pollutant emissions is by the scale of their impacts. A typical division of air pollutants by their scale of impacts is as follows: • Local air pollutants, which typically largely affect the area in or near which they are emitted. Local air pollutants can have impacts on human, animal, and plant health, as well as on visibility, and can also have impacts. • Regional air pollutants, including those pollutants that are play a role in acid precipitation, can have a variety of impacts on health, ecosystems, and structures. • Global air pollutants, particularly greenhouse gases, can affect global climate. Individual air pollutant species may have impacts and one or more of these scales. The subsections below provide brief discussions of air pollutants related to grid interconnections and their impacts at each of these scales. In general, this section attempts to include discussions of the air pollution impacts of all of the parts of the full electric fuel cycle that might occur in any (or all) of the interconnected countries. In practice, however, the major air pollutant emissions changes due to the installation of grid interconnections are likely to be from power generation. Emissions from other parts of the fuel cycle, including air pollutant impacts of line construction (including diesel exhaust and fugitive dust), are therefore mentioned, but not treated in any detail, as these impacts are relatively transient and of short duration. The focus below is therefore on air pollutant impacts of power system operation with and without a grid interconnection between nations.
| + | Evaluating and accounting the full-fuel-cycle environmental impacts of grid interconnections is an important element of the overall process of evaluating [[Economic and Financial Impacts of Grid Interconnections|grid interconnection]] opportunities. Impacts and benefits may occur at any or all points in the fuel chain, from extraction of fuels for electricity generation, to construction and operation of plants and construction and operation of transmission facilities. Environmental considerations have sometimes received less emphasis in energy planning in general than technical, economic, and (often) political issues. In the case of grid interconnections in developing regions, however, the early consideration of environmental impacts in evaluating interconnection options will help to identify key potential problems (including sensitive ecosystems to be traversed by the power lines) as well as potential opportunities that could enhance the interconnection project - including credits for avoided air pollutant and greenhouse gas emissions.<br/> |
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| − | == 7.3.1. Local air pollutant impacts ==
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| − | The local air pollution impacts of power plants run to provide electricity for a line, and the local air pollution benefits of not operating certain power plants due to the availability of electricity from a grid interconnection, will be a function of the type of power plant used or avoided, its proximity to populations or ecosystems that might be affected, the types of control equipment used on the plant, and the species of pollutant emitted. Another key variable is atmospheric conditions, including the presence of other pollutants. Many species of air pollutants react with each other and with other molecules in the atmosphere to form compounds of greater concern. Photochemical smog is an example of a pollution problem caused by the presence of several different pollutant species. The summaries that follow provide very brief reviews of some of the key human health impacts of each pollutant species. • Carbon monoxide, or CO, which results from incomplete combustion of carbon-based fuels. Carbon monoxide is typically a relatively minor component of emissions from electricity generation facilities that are properly operated, as most electricity generation facilities burn fuels under conditions of excess oxygen. Vehicle exhaust, on the other hand, including exhaust of transportation and heavy construction equipment involved in power line construction, is often relatively rich in CO. Carbon Monoxide is a local air pollutant with respiratory impacts, and contributes both directly (as it oxidizes to CO2) and indirectly to the increase in greenhouse gas concentrations in the atmosphere (see below). COs respiratory impacts on human and animal health stem primarily from the ability of the CO molecule to bind to hemoglobin, the oxygen-carrying molecule in blood, and thereby reduce the supply of oxygen to the brain in human and other tissues. Even relatively low concentrations of CO in the air can lead to carbon monoxide poisoning, which is characterized by headaches, dizziness, and nausea in mild cases, and loss of consciousness and death in acute cases. • Sulfur oxides, of which sulfur dioxide (SO2), which is typically the major species in the broader class of sulfur oxides (SOx, in general), are formed when the sulfur in fuel is oxidized during the combustion process. As a consequence, SOx emissions, if not controlled, may be substantial for power plants fired with relatively sulfur-rich fuels such as coal and heavy fuel oil. Some grades of diesel fuel also include significant concentrations of sulfur compounds, and as a consequence the emissions from trucks and other heavy equipment can be a source of SOx. SOx can react with water and oxygen in the atmosphere to yield sulfuric acid, one of the major components of acid rain (see below). SO2 itself can damage plants, with acute exposure to the gas causing death of part or all of a plant, and chronic exposure, though the threshold at which plants are affected varies widely among different plant species. In humans, exposure to SO2 at high levels (above about 5 parts per million, or ppm; the average concentration in urban air in the U.S. is about 0.2 ppm) causes respiratory problems, though exposure to significantly lower doses can sometimes exacerbate existing respiratory problems in sensitive individuals. In developing countries and other areas where coal is used as a home heating and/or cooking fuel, SOx can be an important health hazard as an indoor air pollutant. • Nitrogen oxides (NOx), principally NO and NO2, are formed both by oxidation of nitrogen compounds present in fuel and by high-temperature oxidation of the molecular nitrogen that is the main constituent of air. As a consequence, combustion of all fuels, even fuels with no nitrogen component, can yield NOx. Nitrogen oxides can contribute to environmental problem in several ways. Short-term exposure to elevated NO2 concentrations (0.2 to 0.5 ppm) can cause respiratory symptoms among asthmatics. Indoor fuel combustion, particularly from gas stoves or traditional fuel use, can lead to elevated indoor levels which have been associated with increased respiratory illness and reduced disease resistance among children. Nitrogen oxides contribute to the formation of tropospheric ozone and nitrate aerosols (fine particulates), which are major air pollutants in themselves. Atmospheric emissions of NOx also contribute to the formation of the photochemical smog prevalent in many urban areas, and thus have a general detrimental effect on the respiratory health of humans and other animals, as well as on visibility. In high concentrations, NOx can injure plants, though the required concentrations usually only exist near a large (and uncontrolled) point source of the pollutant. The major hazard to plants from nitrogen oxide emissions may be through the effect of NOx on ozone formation. Atmospheric nitrogen oxides in high concentrations cause respiratory system damage in animals and humans, and even in relatively low concentrations they can cause breathing difficulties and increase the likelihood of respiratory infections, especially in asthmatics and other individuals with pre-existing respiratory problems. • Volatile organic compounds, or VOCs, are sometimes referred to as “Hydrocarbons” or “Non- Methane VOCs”. The many different species in this class of compounds results from incomplete combustion of organic materials in carbon-based fuels, but combustion conditions play a critical role in determining both the types and amount of VOCs emitted from a given device. Again, typically, power plants that are well-run and in good condition will emit relatively low concentrations of VOCs, as most VOCs in combustion gases will be fully oxidized to CO2, but poor or poorly controlled power plant boilers, and many vehicle engines, can emit substantial concentrations of VOCs. In addition to VOC emissions as products of incomplete combustion of carbon-based fuels, VOCs are also emitted from evaporation or leakage of fuels and lubricants from fuel production, transport, and storage facilities (for example, oil wells, tanker ships and trucks, and petroleum refineries) or from fuel-using devices (such as automobile gas tanks and engine crankcases). Sub-classes of VOCs that are often of particular include PAH (polycyclic aromatic hydrocarbons), POM (Polycyclic Organic Molecules) and other VOC species whose molecular structure gives them biological activity of particular importance. These and other individual VOC species exhibit various degrees of toxicity in different animal species. Many hydrocarbons are also carcinogenic (promote the growth of cancers) and/or promote genetic mutations that can lead to birth defects. As a class, hydrocarbons contribute to the production of photochemical smog and of ground level ozone, which are dangerous to human health due to their effects on the respiratory system. High ozone levels also damage crops, forests, and wildlife. • Particulate matter, also referred to as “particulates”, “dust”, or “smoke”, and sometimes abbreviated TSP for Total Suspended Particulates, includes a variety of different compounds—including inert materials such as ash, organic molecules, unburned fuel, and particles of sulfate—that form microscopic and larger particles. Particulate emissions are emitted by power plants (particularly those burning coal and heavier oil fuels), and by heavy equipment using diesel fuel. Fugitive emissions of particulate matter (such as wind-blown dust) related to energy facilities can come from coal storage piles, coal mining operations, or ash storage of disposal sites. Particulate matter (PM) is often divided into categories based on the average size of the particles. “PM10”, denoting the fraction of particulate matter with particle diameter of 10 microns (10 x 10-6 meters) or less, and “PM2.5”, denoting the fraction of particulate matter with particle diameter of 2.5 microns or less. The PM10 and PM2.5 fractions are important because they penetrate further into the respiratory system than larger PM particles, where they can aggravate existing respiratory problems and increase the susceptibility to colds and other diseases. Particulates can also serve as carriers for other substances, including carcinogens and toxic metals, and in so doing can increase the length of time these substances remain in the body. Particulate matter in the air impairs visibility and views, and particulate matter settling on buildings, clothes, and other humans may increase cleaning costs or damage materials. Particulate matter is an important indoor air pollutant in areas where open or poorly-vented household cooking and heating equipment is used, particularly with “smoky” fuels such as wet biomass, crop and animal residues, and low-grade coals. A subset of particulate emissions that has been a topic of considerable research in recent years is “black carbon”, which, in addition to its local health and other impacts, appears to have implications for regional climate, as described in section 2.3.3 below. • Heavy metals are often associated with the combustion of coal and some heavy oils, and are often emitted in association with particulate matter. Heavy metals of concern for emissions from energy facilities include lead, arsenic, boron, cadmium, chromium, mercury, nickel, and zinc. The impacts of metals on the environment and on human health vary with the metal element (and sometimes compound) emitted, and how they are emitted—for example, as a part of particulate matter. Some metals are plant nutrients in low concentrations, but toxic in higher concentrations. Metals of concern in the environment include Lead, Arsenic, Boron, Cadmium, and Mercury, with human health impacts ranging from central and peripheral nervous system effects to blood problems, carcinogenicity, and birth defects. Heavy metals are often retained in the bodies of animals, and “bioconcentrated” in the food chain, leading to high concentrations of heavy metals in animal species that are “top predators” (such as large carnivorous birds, fish, and mammals). • Radioactive emissions to the atmosphere stem primarily from the operation, maintenance, and decommissioning of nuclear power plants and the production, refining, storage, and disposal of the materials that fuel them, but can also be released in very small quantities during activities such as coal mining and combustion. Routine emissions from nuclear reactor and nuclear fuel chain operations are typically relatively minor. Accidents at nuclear facilities, however, can release radioactive materials to the atmosphere ranging in amount from modest to highly significant. The effects of radioactive emissions on human health have been documented119. These health effects include acute effects such as radiation sickness (characterized by nausea, damage to bone marrow, and other symptoms), and chronic effects such as increases in cancer rates, genetic effects, prenatal problems, effects on fertility, shortening of life, and cataracts of the eye. It should be noted that the amount of radioactivity to which the public is exposed during routine operation of nuclear plants is generally not thought to be sufficient to contribute to these problems. As possible configurations of grid interconnections often include trade-offs of fossil-fueled generation in different locations, the net local air pollution benefits (or impacts) of a grid interconnection will in those cases depend upon where the power plants run more and those that run less are located, as well as upon the types of power plants (and their air pollution control equipment) in each case. For example, in Northeast Asia, an interconnection that results in the extended use of coal-fired power plants in remote areas of the Russian Far East but avoids coal-fired generation in more heavily populated China, the ROK (Republic of Korea), or the DPRK (Democratic Peoples Republic of Korea) may result in a net positive impact on human health, although such factors as topography, local weather conditions (and other local pollutant emissions), and impacts on plants, (non-human) animals, and ecosystems must also be taken into account. As noted by Dr. David Streets, the displacement of power generation from typically urban power plants in China, Mongolia, and the DPRK, to remote areas of the RFE may result in considerably reduced human exposure to air pollution hazards120. Grid interconnections that result in improved availability of electricity in specific areas, particularly in developing regions, may have significant impacts on local and indoor air pollution. To the extent that, for example, electricity from a grid interconnection can offset the use of relatively poor quality or polluting fuels, such as the use of low-quality coals or biomass for cooking and heating, the grid interconnection may provide significant local health benefits.
| + | = Further Information<br/> = |
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| − | == 7.3.2. Potential regional air pollutant impacts ==
| + | *[http://www.un.org/esa/sustdev/publications/energy/chapter7.pdf Download the full Article "Environmental Aspects of Grid Interconnection" from UN here.] |
| | + | *<span style="font-size: 0.85em"></span>[[Portal:Grid|Grid Portal on energypedia]] |
| | + | *[[Impacts_Environmental|Category Impact Environmental on energypedia]] |
| | + | *[[Grid Interconnection of Micro-hydro Projects (MHPs) in Nepal|Grid Interconnection of Micro-hydro Projects (MHPs) in Nepal]] |
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| − | Although some photochemical smog and other air pollution impacts can, at times, be sufficiently widespread as to be nearly regional in nature, arguably the major regional air pollution impact is acid precipitation, sometimes called “acid rain”, which is a significant environmental issue in North America, Northern Europe, and Northeast Asia, though not yet a serious issue in other regions. Depending on the way that a grid interconnection is operated, net regional emissions of acid gases could be reduced or displaced. Brief descriptions of some of the issues associated with the emissions of air pollutant precursors to acid precipitation are provided below122. Acid deposition results when nitrogen and sulfur oxides (“NOx” and “SOx”) react in the atmosphere with oxygen and water droplets to form nitric and sulfuric acids (HNO3 and H2SO4). As the water droplets condense, they fall as rain, snow, or fog, hence the common name “Acid Rain”. While acid rain is the most frequently discussed pathway for these compounds to return to earth, nitrates and sulfate ions123 (NO3 -and SO4 2-) also can combine with positive ions or adhere to the surface of particles in the atmosphere, sometimes falling to earth in a dry form (“dry deposition”). SOx and NOx can also directly adhere to soil or plant surfaces, eventually reacting with water and oxygen to form acids. As a consequence, the terms “Acid Rain” and “Acid Precipitation” are somewhat incomplete—though more common—terms for the broader phenomenon of acid deposition. The effects of acid rain vary considerably with the vegetation, soil types, and weather conditions in a given area. Under some conditions, the addition of sulfate and nitrate to the soil helps replace lost nutrients, and aids plant growth. In other instances, however, acid deposition can cause lakes and streams to become acid, damage trees and other plants, damage man-made structures, and help to mobilize toxic compounds naturally present in soil and rocks. The countries of Northeast Asia have already begun to experience some important impacts of acid rain. Forest health in some areas of the Koreas, China, and Japan has already revealed evidence of degradation that points to acid rain124. Man-made materials such as zinc-plated steel have drastically shorter-than-normal lifetimes in south China, and irreplaceable cultural landmarks made of limestone and other substances are being degraded at an accelerating rate. As noted above, sulfur oxides are produced during combustion of coal, which contains varying amounts (about 0.5 to 5 or more percent) of sulfur, and during combustion of fuel oil, particularly the heavier grades. These fuels are most commonly used in large industrial facilities and in electric power generation. Nitrogen oxides are produced at varying rates by all types of fossil and biomass fuel combustion; the nitrogen in the NOx produced during combustion is derived both from nitrogen in the fuel and from the molecular nitrogen (N2) that makes up nearly four-fifths of the air we breathe. Gasolinepowered autos and trucks are major emitters of NOx. Though acid deposition can be a local phenomenon, particularly in urban areas and in areas near a large point source of emissions, the extent to which acid gases are carried by prevailing weather patterns makes acid rain a truly regional issue, one that frequently crosses national boundaries. For example, many of the acidified lakes in Eastern North America are hundreds of kilometers from major sources of emissions, and emissions from as far away as the United Kingdom have contributed to acid rain and forest decline in Scandinavia126. A paper by Prof. Zhu Fahua prepared for the Third Northeast Asia Power Grid Interconnection Workshop and entitled “Environmental Impacts and Benefits of Regional Power Grid Interconnections for China”, provides a review of the air pollution impacts, including local and regional (acid gas) emissions, of thermal power plants in use in China. Prof. Zhu’s paper also estimates the potentially significant reductions in local and regional air pollutants that might accrue from substituting hydro-based imported power for local thermal generation in Northeast China127. The potential of transmission interconnections to displace from one location to another or (in some configurations and depending on which plants are used to feed electricity into the line) to reduce overall regional emissions may be one element of an overall acid gas emissions reduction strategy for a region. What this suggests is that the evaluation of the net changes due to a transmission interconnection in emissions of sulfur oxides, nitrogen oxides, and the several other species of pollutants that interact with those gases should be assessed for each interconnection scheme considered. Such assessments must take into account, at least crudely, the locations where net emissions will change, the seasonal meteorology of and timing of emissions changes, the pattern of long-range transport of pollutants from where they are emitted (or avoided) and the sensitivity of the areas where deposition from the emissions will occur. This sort of modeling is not at all easy, and in most places where interconnections are contemplated will require capacity building, data sharing, and above all, extensive coordination in modeling efforts in order to obtain credible results. Recent research has indicated that the emissions of “black carbon” (soot) particulates, mostly emitted from indoor and local air pollutants, be causing changes in regional and even global climate128. Black carbon particles in the atmosphere absorb sunlight and “heat the air, alter regional atmospheric stability and vertical motions, and affect the large-scale circulation and hydrologic cycle with significant regional climate effects”129. Higher recent incidence of floods in South China, and drought in North China, as well as moderate cooling in China and India during a period when most of the rest of world has experience warming, may, modeling results suggest, be impacts of regional black carbon emissions. To the extent that they can assist in reducing black-carbon-emitting use of coal and biofuels, regional grid interconnections may be able to claim additional regional environmental benefits.
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| − | == 7.3.3. Global air pollution impacts ==
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| − | International electricity grid interconnections, depending on how they are designed and operated, may offer significant benefits in terms of avoided emissions of “global” air pollutants. Two possible types of emissions can be considered here. The first are emissions of “greenhouse gases” that contribute to climate change. The second are emissions of gases and particles that recent research suggests may be transported considerable distances even across oceans. These classes of global air pollution impacts are described briefly below, and discussions are provided as to how grid interconnections might affect emissions that cause these classes of impacts. “Global warming”, “climate change”, and the “greenhouse effect” are common expressions used to describe the threat to human and natural systems resulting from continued emissions of heat-trapping or “greenhouse” gases (GHGs) from human activities. These emissions are changing the composition of the atmosphere at an unprecedented rate. Although the complexity of the global climate system makes it difficult to accurately predict the impacts of these changes, the evidence from modeling studies as of the mid-1990s, as interpreted by the world’s leading scientists assembled by the Intergovernmental Panel on Climate Change (IPCC), indicates that global mean temperature will increase by 1.5 to 4.5º C with a doubling of carbon dioxide concentrations, relative to pre-industrial levels130. Given current trends in emissions of greenhouse gasses, this doubling—with its attendant increase in global temperatures, would likely happen in the middle of the 21st century. For reference, a global increase of 2º C from today’s levels would yield global average temperatures exceeding any the earth has experienced in the last 10,000 years, and an increase of 5º C would exceed anything experienced in the last 3,000,000 years. Moreover, it is not simply the magnitude of the potential climate change, but the rate of this change that poses serious risks for human and ecosystem adaptation, with potentially large environmental and socioeconomic consequences. The essence of the greenhouse effect is that particular trace or “greenhouse” gases in the atmosphere absorb some of the outgoing radiation on its way to space from the surface of the earth. These gases, principally water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3), together act as a transparent atmospheric “blanket” that allows sunlight to warm the earth but keeps infra-red radiation (heat) from leaving the earth and radiating out to space Without this atmospheric “blanket” of trace gases, the equilibrium surface temperature of the earth would be approximately 33° C cooler than today’s levels, averaging -18ºC rather than +15ºC, and making the earth too cold to be habitable. It is this blanketing effect of the atmosphere that is referred to as the greenhouse effect. A greenhouse is a useful analogy; the atmosphere behaves somewhat like the glass pane of a greenhouse, letting in visible or short-wave radiation, but impeding somewhat the exit of thermal energy, thereby increasing the equilibrium temperature inside the greenhouse. The present concern with global warming does not center on the natural greenhouse effect of the atmosphere on global equilibrium temperature and climate. Rather, concern arises from the potential additional global warming that may occur due to the rapidly increasing concentrations of heat-trapping greenhouse gases caused by human activities such as the combustion of fossil fuels and the reduction of carbon stored in biomass through conversion of forests and other natural land types to settlements, agricultural land, and other uses. The combustion of all carbon-based fuels, including coal, oil, natural gas, and biomass, release carbon dioxide (CO2) and other “greenhouse gases” to the atmosphere. Over the past century, emissions of greenhouse gases from a combination of fossil fuel use, deforestation, and other sources have increased the effective “thickness” of the atmospheric blanket by increasing the concentration of greenhouse gases (or GHGs) in the troposphere, or lower part of the atmosphere (ground level to about 10-12 km). It is this “thicker blanket” that is thought to be triggering changes in the global climate. Other major “direct” greenhouse gases emitted by combustion activities and other fuel cycle activities are methane (CH4), and nitrous oxide (N2O). Both of these gases have substantial non-energy sector sources, and emissions of methane from coal mines is often also significant. Chlorofluorcarbons (CFCs), which are man-made chemicals used as refrigerants, as fire retardants, and for other purposes, are another major class of direct greenhouse gases, but their direct emissions from the energy sector are not significant. A number of gases may also indirectly affect global climate131. Another potential source of greenhouse gases that should be investigated in any grid interconnection scheme that is likely to involve construction of new hydroelectric facilities is biomass decomposition in areas flooded for hydroelectric reservoirs. Decomposition of biomass in the flooded areas releases carbon dioxide, but more importantly, also results in the significant release of methane—the product of anaerobic decomposition of biomass. Hydro reservoirs can also change the fate of carbon-rich sediments that wash into rivers, perhaps rendering the carbon compounds in the sediments more likely to undergo methane producing anaerobic decomposition than to be degraded aerobically to carbon dioxide or incorporated into longer-lived soil carbon. This difference is very significant when the relative impacts of methane and CO2 emissions on climate are considered, as methane has an impact on climate more than 20 times as strong, on a per-unit-mass basis, as CO2. Some researchers have found net greenhouse gas emissions, expressed on CO2-equivalent basis per unit of electricity generated, for specific Brazilian hydroelectric reservoirs, to be many times larger, on an annual basis, than for natural gas-fired combinedcycle power plants. In the context of discussions of grid interconnections from Quebec, Canada to the Northeast United States, the following point was made132. “ On a large scale and from an environmental point of view, hydroelectric energy development can be an ideal complement to energy needs and parallel commitments to reduce greenhouse gas emissions. The analysis, however must account for the greenhouse gases produced by biomass degradation in reservoirs, and Hydro-Quebec is presently studying this phenomenon.” Based on research into methane production in hydroelectric reservoirs in Amazonia and other areas, Philip Fearnside of the Brazilian National Institute for Research in the Amazon concludes133: “ . . . reservoirs become virtual methane factories, with the rise and fall of the water level in the reservoir alternately flooding and submerging large areas of land around the shore; soft green vegetation quickly grows on the exposed mud, only to decompose under anaerobic conditions at the bottom of the reservoir when the water rises again. This converts atmospheric carbon dioxide into methane, with a much higher impact on global warming than the CO2 that was removed from the atmosphere when the plants grew.” Assessment studies have shown how climate changes and sea level rise may give rise to a vast array of biological and physical impacts. In many cases, these impacts are local in nature, but may be inherent to many parts of the globe. Particular examples of estimated impacts include: • Changes in temperatures • Changes in the amount of precipitation • Changes in the timing of precipitation • Changes in plant growth rates • Changes in the severity of storms and floods—and erosion exacerbated by storms and floods—as well as in the timing and amount of water discharged by rivers. • Changes in forests due to changes in temperature, precipitation, and evaporation. • Changes in the distribution and prevalence of plant and animal pests and diseases. • Changes in biodiversity and species distribution—all of the changes above have the potential to alter the distribution and range of plant and animal species, including both domesticated crops and livestock and native flora and fauna. • Changes in ocean temperatures and their effects on ocean productivity, including the productivity of and growth rates of reef ecosystems. • Changes in sea level rise brought on by the expansion of warmed ocean waters and by the melting of polar ice. Hundreds of meters to many kilometers of shoreline inundation may result from tens of centimeters of sea level rise. Coastal wetlands are especially at risk from increases in the sea level associated with climate change. The changes in climatic variability discussed above—changes in the severity, frequency, and location of tropical storms, for example—will compound the impact of sea level rise, and place coastal ecosystems, infrastructure, and populations even more at risk. Although the construction and maintenance of transmission lines for grid interconnection will imply modest emissions of greenhouse gases, especially CO2, from fuel burned in transport and construction equipment, the major implications of grid interconnections on climate change will be from emissions related to the generation of electricity. The nations to be interconnected may include power plants the burn coal, oil, and natural gas, as well as nuclear and hydroelectric plants. To the extent that plants that burn coal, especially older, inefficient plants, can be displaced by imported electricity generated using (for example) nuclear and hydroelectric energy, the overall regional greenhouse gas emissions will (likely) decrease. Other net fuel-cycle emissions or savings, including methane emissions from coal mining, gas and oil extraction, and fuel transport, must also be taken into account when figuring the net impact of grid interconnections on greenhouse gas emissions. One potential issue of note that is related to the net greenhouse gas emissions benefits (if any) of grid interconnections has to do with options for the financing of grid interconnections. A demonstration that a grid interconnection will lead to substantial net greenhouse gas emissions reductions may allow the project to qualify from partial funding via the Global Environment Facility (GEF) or through Clean Development Mechanisms (CDM). These possibilities are discussed in greater detail in section 7.9 of this report. In recent years, attention has focused on the possibility that particulate and other pollutants from Eurasia are transported by winds to the Western Hemisphere, and in particular to the areas of North America bordering the North Pacific. A summary article on the topic noted risks to ecosystems and wildlife many thousands of kilometers away from the emissions source134: News reports based on recent suggest that Trans-Pacific air pollutant transport is widespread in destinations, sources, and the types of pollutants involved135. Accurate quantitative estimates of the sources and receptors—and identification of the key species involved in Trans-Pacific air pollution—may be years or decades away, but this global environmental issue bears at least mention in forward-looking environmental assessments—particularly as the atmospheric conditions that carry trans-Pacific pollutants likely exist elsewhere on the globe. Through their impacts on pollutant emissions from electricity generation and other fuel-cycle activities, grid interconnections could influence the types and amounts of pollutants available for long-distance transport.
| + | = References<br/> = |
| | | | |
| − | == 7.3.4. Requirements for calculation of net air pollution costs and benefits of a grid interconnection ==
| + | This Article is originally from "[http://www.un.org/esa/sustdev/publications/energy/chapter7.pdf Environmental Aspects of Grid Interconnection]" |
| | | | |
| − | A brief roster of the types of information and calculations that are likely to be required for the estimation of the air pollutant benefits and costs of a grid interconnection is as follows: • An assessment of which power plants, or classes of power plants, in which locations will run more, and which will run less, as a result of the grid interconnection, and the amount by which electricity generation at each plant (or class of plant) is increased or decreased. An indication of the seasonality of increased or decreased generation will also likely be necessary. This assessment itself is decidedly non-trivial. Although relatively simple modeling or assumptions may be used to provide a rough estimate of which plants might be affected, ultimately a collaborative modeling effort that attempts to optimize generation over the several countries potentially involved in an interconnection will be needed. Even a strict economic optimization, however, may not be adequate, as political, financing, and environmental considerations will play a role in determining which plants are affected by an interconnection, and these consideration need to be taken into account in any analysis. • An assessment of how the interconnection will affect other parts of the fuel cycles that fuel electricity generation, including the impact on the quantity of coal mined (and the location where it is mined), the quantity of gas imported/transported, and the quantity of refined products produced and stored. • An assessment of how the interconnection will affect non-electric fuel use, if at all, including which types of fuels and devices (wood stoves or oil lamps, for example) will be affected, by how much per year, and where the devices are located. • Emission factors for power plants and other fuel-using devices implicated in the interconnection. These factors will express the emissions of atmospheric pollutants in mass (or radiological) units per unit fuel consumed, or per unit of power output. Some key aspects of fuel quality—most notably fuel heat content, carbon content, and sulfur content—are likely inputs to the determination of emission factors. David Streets, in a paper originally prepared for the First Workshop on Power Grid Interconnection in Northeast Asia, provides a sample set of emission factors for power plants (and, in the case of biofuels, residential stoves) using different types of fuels136. These emission factors are expressed in terms of mass of emissions per unit of input fuel. • Emission factors for pollutants associated with other parts of the electricity fuel chain. These would include, for example, estimates of the fraction of gas carried that is lost from pipelines or from LNG shipping and receiving facilities (including gas consumed in transit), methane and coal dust emissions from coal mining operations, and emissions from oil refining. Emissions to the atmosphere from fuel storage and waste disposal should also, if possible, be counted. Emissions related to power line construction could also be included here, although, as noted above, these are likely to be relatively small, and of short duration.
| + | <references /> |
| − | For greenhouse gases, the product of changes in electricity consumption (by plant or plant class),
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| − | and emission factors for each plant, plus any changes in other fuel cycle activities multiplied by the
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| − | greenhouse gas (especially CO2 and methane) emission factors for those activities, gives a measure of
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| − | the net impact of an interconnection on climate change. In the case of local and regional air pollutants,
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| − | however, modeling of the fate of emissions, including atmospheric transport and chemistry, deposition,
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| − | and health impacts, will be necessary for a fully rigorous assessment of the environmental consequences
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| − | of net air pollutant emissions or savings due to a grid interconnection. For an approximate assessment,
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| − | however, the quantities of air pollutants, a consideration of where they are emitted, and an approximate
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| − | consideration, based on prior modeling, of where the net impacts of changes in emissions are likely to
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| − | occur, may be sufficient. A key environmental benefit of grid interconnection may be the avoidance or
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| − | displacement of air pollutant emissions from power plants located near urban or ecologically sensitive
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| − | areas. Identifying and quantifying these types of benefits require the power plant operation estimates,
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| − | fuel cycle assessments, estimates of other increased or avoided fuels use, emission factors, and impacts
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| − | analyses noted above.
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| − | ==7.4. Impacts of Grid Interconnection on Water Pollution and Water Quality==
| + | [[Category:Impacts_Environmental]] |
| − | | + | [[Category:Grid]] |
| − | To perhaps a greater extent than air pollution impacts, significant water pollution impacts—both benefits
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| − | and negative impacts—of grid interconnections can come from construction and maintenance of power
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| − | lines, as well as from the different parts of the electricity generation fuel cycles in the interconnected
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| − | countries. Many of these impacts are likely to be extremely location-specific, even site- and plant-specific.
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| − | As a consequence, the discussion below largely only mentions a list of generic impacts that can be detailed
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| − | more fully when an assessment of water pollution impacts of a specific grid interconnection is needed.
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| − | | |
| − | ==7.4.1. Generic Impacts from Construction and Maintenance of Power Line==
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| − | | |
| − | A number of potential impacts on water quality may results from the construction and maintenance of
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| − | transmission lines and their right-of-ways. These potential impacts include:
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| − | • Erosion from soils stripped of vegetation during power line right-of-way clearance and power line
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| − | construction. Erosion impacts are likely to be of concern particularly in areas where forested hillsides
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| − | must be logged to create a transmission right of way.
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| − | • Erosion from access road construction and, during power line operation, from vehicle traffic on
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| − | existing and new access roads.
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| − | • Impacts of heavy machinery operation in rivers and wetlands on water quality.
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| − | • Lubrication oil and fuel leakage and other emissions from heavy machinery used in power lines.
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| − | • Accidental spills and other emissions of liquids used in transmission infrastructure, including transformer
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| − | oils.
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| − | • Pollution of run-off and groundwater from herbicide treatment of power-line right-of ways, if such
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| − | treatments are used.
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| − | Each of these classes of emissions and impacts can in turn directly affect nearby plants and animals
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| − | (through toxic responses or changes in the availability or quality of water), or may affect downstream
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| − | ecosystems and human and animal populations through their impacts on water quality and hydrology.
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| − | Impacts on water quality may include increasing the quantity of sediments, sediment-borne chemicals,
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| − | and chemicals from human activities carried in water. Impacts on hydrology can include changing the
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| − | seasonal rate of flow of water in watersheds, changing the way that water flows through soils, and changing
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| − | the quality and quantity of groundwater in specific locations137.
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| − | | |
| − | ==7.4.2. Impacts at the Power Plant Level==
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| − | | |
| − | As with air pollutant emissions, water pollutant emissions at the power plant level may increase or be
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| − | avoided by the operation of a grid interconnection. For plants burning fossil fuels, water pollutant emissions
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| − | may increase or decrease depending on whether the use of a power plant or a class of power plants
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| − | increases or decreases. The areas in which water pollutant emissions may increase or be avoided include
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| − | routine emissions from boiler feed water tube cleaning (during plant maintenance), spills and leakage of
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| − | liquid fuels during handling and from tanks, and leaching of acids, metals, and other potentially toxic
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| − | materials from coal and coal ash storage piles. These pollutants, if not properly managed or treated,
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| − | may result in a number of different chronic or acute impacts on ecosystems. All types of thermal power
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| − | plants, including nuclear power plants, will likely (unless using dry cooling towers are used exclusively)
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| − | release thermal emissions (warm water) to nearby bodies of water used to cool power plant condensers.
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| − | These emissions, depending on the size and flow of the heat from the power plant relative to the size and
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| − | flow of the water to which the heat is released, may have impacts on the aquatic ecosystems in the area,
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| − | promoting the growth of some aquatic plant and animal species over others, with potential impacts on
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| − | local fisheries.
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| − | An area of potential power-plant-related water quality impacts of particular relevance to many proposed
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| − | developing-country grid interconnections are impacts related to hydroelectric power development.
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| − | Hydroelectric dam construction may (likely will) result in significant at least short-term water quality and
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| − | quantity impacts (including sediment and chemical loads) in the rivers affected by the plant. Hydroelectric
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| − | operation will change the timing and quality of water available downstream, as well as the sediment load of
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| − | the river. Areas inundated for reservoirs may contain natural and man-made compounds and materials that,
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| − | as they decompose or degrade over the years underwater, may leach chemicals into the reservoir, eventually
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| − | affecting downstream water quality. These types of impacts will be very site- and design-specific, but should
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| − | be taken into account when assessing the net environmental impact of a grid interconnection.
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| − | Another set of sources of water pollutant emissions and water quality impacts may stem from other
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| − | fuel cycle activities, such as exploration for, extraction of, and transport of petroleum or coal fuels for
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| − | power generation. Both routine (such as minor oil losses during transfers from ships to shore terminals)
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| − | and accidental (such as pipeline “blowouts”, or spills of oil or oil products resulting from tanker accidents) emissions of water pollutants may need to be considered in a comprehensive assessment of water
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| − | pollution impacts. The likelihood is, however, that the sum of these impacts, when averaged over the net
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| − | impacts of a transmission interconnection on power generation, will be rather modest.
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| − | | |
| − | ==7.4.3. Preparing Estimates of Water Quality Impacts==
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| − | The preparation of estimates of net additional or avoided emissions of water pollutants (particularly routine
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| − | emissions from electricity generation or electric fuel cycle activities) resulting from grid interconnections
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| − | may in some instances be relatively straightforward. For these types of routine emissions, estimates
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| − | of net generation (or avoided generation) by power plant or plant type are needed, as described above
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| − | in the context of the estimate of net air pollutant emissions impacts. Also needed are water pollutant
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| − | emission factors, which may be derived from plant operating histories, or estimated from international
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| − | compilations of emission factors (though both may be difficult to find). Estimates of water pollutant
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| − | emissions of a short-duration (for example, during power line construction) or accidental nature are
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| − | much harder to estimate. In addition, the ultimate impact on water quality, plants, animals, ecosystems,
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| − | and humans, of all types of net emissions (or emission savings, including construction-related, routine,
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| − | and accidental water pollutant emissions) may often require a combination of site- and event-specific
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| − | qualitative consideration and/or empirical sampling and/or quantitative modeling. In some cases rough
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| − | calculations can help to identify the range of impacts. For example, given estimates of the area of land
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| − | inundated by a new hydroelectric reservoir, and knowledge about the vegetation and soil in the area to be
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| − | inundated, it may be possible to calculate the release of water pollutants, and rough hydrologic modeling
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| − | may help to indicate downstream water quality impacts.
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| − | | |
| − | ==7.5. Impacts of Interconnection on Generation of Solid and Hazardous Wastes==
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| − | | |
| − | The third category of pollutant emissions considered in this Chapter is solid and hazardous wastes. As
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| − | with air and water pollutants, solid and hazardous wastes can be produced and/or released during power
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| − | line construction and operation, at the power plant level, or at other points in the fuel cycle. These
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| − | wastes may be hazardous to health and ecosystems in and of themselves, may present a disposal problem,
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| − | and, depending on how they are stored and disposed of, may have the potential to create other types of
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| − | environmental impacts. Leaching of water pollutants from coal ash piles is an example of how solid waste
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| − | generation can produce water-borne environmental impacts; similarly, dust blown into the air from ash or
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| − | pulverized coal piles can create an air pollution problem.
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| − | | |
| − | ==7.5.1. Solid and hazardous wastes during interconnection construction and operation==
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| − | | |
| − | The types and extent of solid and hazardous wastes produced during the construction and operation of a
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| − | grid interconnection will vary considerably with the type of power line (and auxiliary equipment such as
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| − | converter stations and substations) installed, and the local topography and geology. Among the potential
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| − | types of solid and hazardous wastes that could be produced are:
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| − | • Dirt, rock, and other materials removed when footings for power line towers are built, right-of-ways are
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| − | cleared, access roads are constructed, or foundations for converter stations and substations are prepared.
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| − | • Trees and other biomass removed to clear right-of-ways (to the extent that these materials are not used
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| − | for wood, fiber, or fuel).
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| − | • Hazardous materials used in substation transformers, including oils. Particularly in cases where transmission
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| − | facilities are upgraded or modernized to install the interconnection line, there may be PCBs
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| − | (Polychlorinated Biphenyls) in older equipment that, if not disposed of appropriately, may cause a
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| − | variety of effects138.
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| − | Assessment of these highly site-specific construction/demolition-related impacts should be a part of the
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| − | assessment of an interconnection project. Most of these impacts, however, are likely to be one-time impacts,
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| − | not ongoing or routine emissions.
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| − | | |
| − | ==7.5.2. Impacts at the Power Plant Level==
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| − | | |
| − | At the power plant level, grid interconnections may result in an increase or decrease in the generation of solid
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| − | wastes and nuclear wastes, depending, as with air and water pollutants, on which power plants or classes of
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| − | power plants in which locations (and using which fuels) are run more or less as a result of the interconnection.
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| − | Changes in emissions of solid wastes from changes in power plant operations as a result of interconnections
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| − | will largely be changes in “fly ash” and “bottom ash”, plus “scrubber sludge” from emissions control
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| − | equipment. Ash is an environmental effluent of considerable importance, particularly for large boilers and
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| − | other types of facilities fueled with solid fuels (especially coal) and heavy oils139. Bottom ash remains in
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| − | the power plant’s boiler after fuel combustion is complete. Fly ash is particulate matter that is captured
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| − | by pollution-control equipment such as cyclone collectors and fabric filters. Beyond the physical effects
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| − | of piles of ash on landscapes and on ecosystems, ash from coal and oil combustion contains heavy metals,
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| − | toxic organic compounds, and other potentially damaging substances that can leach (that is, be dissolved in
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| − | rainwater and flow out of the pile) out of ash disposal sites and potentially affect ecosystems. If piles of ash
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| − | are left uncovered, wind can blow smaller ash particles into the air, where their potential effects are those
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| − | noted for air emissions of particulates. Disposal of ash is also an economic problem, particularly in countries
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| − | where landfill space is scarce, where ash is defined as a hazardous waste, or where ash must be transported
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| − | a long distance for disposal.
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| − | Scrubber sludge is an effluent of some concern for coal-fired industrial and electricity-generation equipment.
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| − | A scrubber is a device in which exhaust gasses pass through (typically) a solution of a chemical such as
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| − | calcium carbonate (limestone) in water. This process “scrubs” sulfur oxides and other components from the
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| − | exhaust gas stream, and produces a sludge containing calcium sulfate, ash particles, and other chemicals. Some
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| − | of these compounds can leach from storage areas into the environment, potentially contaminating surface and
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| − | ground waters, though some, if handled correctly, can be recycled into industrially useful products.
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