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AAAS Policy Brief: Renewable Energy

Issue Summary | Resources | Comparison Table | Definitions and Conversions

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Introduction

Among efforts to curtail greenhouse emissions, one of the areas receiving the most attention is the electrical power generation sector, which represents approximately 26 percent of global carbon emissions and is the largest overall contributor.¹ Additionally, as more countries experience economic growth and raise their standards of living, particularly those with large populations such as China and India, the demand for inexpensive electrical power will continue to grow, a demand that is currently met largely with carbon-intensive fossil fuels like coal and natural gas. To prevent a continued reliance on large amounts of carbon-emitting fossil fuels for power, many governments and private businesses are looking to alternatives that are carbon-neutral and have the added benefit of being renewable. These options include familiar power sources like solar, wind, hydroelectric, and geothermal, as well as more advanced uses of renewable resources such as wave and tidal energy. Developing and deploying these energy sources at the scale needed to mitigate climate change will require substantial investments in science, technology and infrastructure, as well as economic incentives and other policy mechanisms to foster their widespread use in the global power market.

Solar
Wind
Hydroelectric
Geothermal
Biomass
Efficiency
Policy Options
Research and Development

Solar

Overview: While solar power has been used for decades in various applications, from satellites to digital watches, because of its relatively high cost its use as a large-scale electrical power source has been very small, representing only a fraction of a percent of total U.S. power generation and about 1.7 percent of renewable power.² Solar energy can be harnessed for electrical power generation in one of two ways: it can be used to boil water and drive a turbine or it can generate an electrical current directly using a photovoltaic cell. Buildings can also use solar energy to make hot water and provide heating, reducing or eliminating the need to use electricity for these purposes. Given that buildings currently use 71 percent of the electrical power generated in the U.S.³, solar represents one opportunity to reduce power use.

Advantages: Solar is quiet, produces no pollution during its operation, and can be sited almost anywhere, including on rooftops and onboard moving vehicles like cars, trains, and ships. Solar generating devices are also very reliable and can last a long time, especially photovoltaic cells since their components have no moving parts.⁴

Drawbacks: At the present time, solar is still not cost competitive for electrical power generation without economic subsidies. Also, centralized large scale generation using current technology requires huge arrays, which take up large areas of land and require tremendous up-front investments in capital, especially if they use photovoltaic cells. Additionally, because it relies on direct sunlight, solar is subject to interruptions in supply at night and during cloudy weather that must be backed up by another power source. Production of photovoltaic cells also involves the use of toxic materials such as cadmium, although the amounts used are very small and improvements in production technology have reduced emissions of cadmium to almost negligible amounts.⁵

New Technology: Research on solar currently focuses mainly reducing the cost of photovoltaic cells, increasing the generating capacity of solar plants, and optimizing the locations and positioning of solar generating facilities. More advanced applications of solar plants can store excess power for use at night or whenever demand exceeds the generating capacity of the plant, helping to prevent interruptions in supply. A public utility in Arizona has plans for such a plant, which will be the first of its kind in commercial use in the United States.

Wind

Overview: Like solar, wind energy has also been in use for generating electricity for several decades, although until recently its use for this purpose in the U.S. has been relatively minor, limited to a few select areas. With the rise in concern in recent years over carbon emissions and the prospect of future legislation to control emissions, interest in wind as a power source has grown dramatically. Installed capacity in the Unites States tripled between 2003 and 2007⁶ and a report from the U.S. Department of Energy estimated that wind could power up to 20% of the U.S. grid by the year 2030. In 2007 alone, the U.S. increased its wind generation capacity by 5,244 megawatts (MW), an amount representing 30% of newly installed power generation from all sources that year and an increase of 45% in wind capacity over the previous year. The state of Texas was the largest market for wind, having added 1,618 MW in 2007, about 37 percent of all new U.S. wind capacity added that year and more than the total existing capacity of any state except California.⁷ Other nations, including China and Germany, have also been rapidly expanding their wind generation capacity. This rapid growth has occurred not only because of concerns about carbon emissions, but because policy mechanisms are in place to encourage its use by making it more affordable compared to fossil fuels. More on these policy mechanisms is presented below.

Advantages: Wind power produces no air or water pollution and can be placed almost anywhere on land where sufficient wind power density exists, as well as offshore.

Drawbacks: Wind turbines make noise and are sometimes considered a visual nuisance, forcing them to be located in remote areas, which increases electrical transmission losses. Additionally, concerns have been raised about the impacts of large wind farms on migrating birds and on global climate patterns, although data shows that the relative risk to birds compared with buildings or vehicles is very small, representing less than a tenth of a percent of human-caused bird mortalities,⁸ and a study on the impact of large wind farms on wind circulation showed that the energy extracted from the atmosphere by wind turbines worldwide has a nearly negligible effect on climate compared to the many other factors affecting it, such as solar radiation and greenhouse gases.⁹ Finally, like solar, wind is an intermittent power source since it only provides power when the wind is blowing, so turbines must be located in optimal locations, must be constantly adjusted as the wind changes direction, and must be backed up by another source to account for dips in supply.

New Technology: Recent technological developments for wind power include refinements to the electrical generators, aerodynamic improvements to the turbine blades, use of more advanced light-weight materials, and improvements to control software that deals with fluctuations in wind speed and direction. These improvements make the turbines quieter, more efficient and reliable, and able to extract more energy from wind. In all, technological improvements have been estimated to increase energy generation by up to 61 percent and reduce the cost of turbines by as much as 36 percent by 2030.¹⁰

Hydroelectric

Overview: In the U.S., hydroelectric power has seen much wider use than other renewable sources, representing over 70 percent of renewable electrical power generation and making up about 6 percent of total electrical power generation.¹¹ However, unlike solar and wind, hydroelectric is relatively limited in its growth potential because of the unique physical requirements for making it effective, either dams that provide stored energy in the form of reservoirs, or large elevation drops such as waterfalls. Because of the highly publicized adverse impacts of dams, especially huge projects such as the Three Gorges Dam in China and the Aswan High Dam in Egypt, hydroelectric power often receives less than favorable evaluations as a future alternative power source. However, small dams and other types of technology can make hydroelectric power available in many more areas and in less damaging ways.

Advantages: Hydroelectric power results in very small emissions, is relatively reliable as long as a constant water source is available, and has potential for signficant expansion using existing infrastructure since only 2 percent dams in the U.S. are used to generate electricity,¹²leaving nearly 30,000 MW of untapped potential.¹³

Disadvantages: The dams and reservoirs often used as a stored energy source can have damaging impacts on river-reliant ecosystems and fisheries as well as effects on the water supplies downstream of dams, a factor of particular concern on rivers that cross international borders. Additionally, the infrastructure necessary for large scale hydroelectric power projects, even beyond the dams themselves, can be very expensive. Finally, annual variations in water resources resulting from changes in weather and agricultural water use can affect hydropower facilities substantially. As a specific example, the difference in hydopower generation in the U.S. in 2003, a relatively high year, and 2001, a relatively low year, was 59 billion kWh, a variation expected to grow larger in the future due to the effects of climate change on water resources.¹⁴

New Technology: Recent technological developments for hydroelectric power involve the use of water movement without relying on dams or waterfalls. This includes the movement of waves, tides, and water currents, all of which have been successfully demonstrated as potential power sources.

Wave Power: A report from the U.S. Department of the Interior in 2006 estimated that wave energy off the coastal United States (including Alaska and Hawaii) at a depth of 60 meters contains a potential 2,100 terawatt-hours of annual generating capacity, nearly 20 percent of annual U.S. demand. Although the level of technological development necessary to make it economically recoverable was unclear, the report describes various technological approaches. In early 2007, a utility company in Oregon received a permit from the Federal Energy Regulatory Commission (FERC) to install up to 50 MW of wave power off the coast of Douglas County, Oregon¹⁵ and in December of that year, Pacific Gas and Electric announced it would install its own wave generation facility off the coast of Northern California.¹⁶
Tidal Power: Recognized since the middle ages as source of energy, tides have only been harnessed for electrical generation in very limited cases, although their potential as a reliable and cyclical clean energy source has drawn attention. Tidal power can be produced by tidal barrages, essentially dams that store the energy of rising tidal waters and release them during ebb tide, by tidal lagoons acting as reservoirs, or by extracting energy from tidal currents. Factors that inhibit development are the costs of the facilities and concerns about environmental impacts associated with structures like barrages.¹⁷ Additionally, tidal power’s effectiveness is dependent on the strength of the tides in a given area. An example of a tidal barrage in use for a long period of time is on the Rance River in France. In the U.S., Verdant Power is conducting an 18-month study in the East River of New York City, a project called the Roosevelt Island Tidal Energy Project, which uses no barrages and could generate up to 10 MW if approved by FERC.
River Currents: Generating power from river currents without using large reservoirs, sometimes referred to as “run-of-the-river” projects, can be an attractive alternative because it doesn’t require flooding large areas of land, although the potential for adversely affecting ecosystems in the utilized river still exists. An example of this type of power in use is the Chief Joseph Dam, on the Columbia River in Washington State and the Ghazi Barotha project on the Indus River in Pakistan.

Geothermal

Overview: The term geothermal applies to any energy source that is recovered from below the earth’s surface in the form of heat. It can be extracted in the form of steam from deep geological sources and used to run turbines or it can be used in smaller amounts from shallow sources and used to run geothermal heat pumps for heating and cooling of buildings. In 2006, U.S. consumption of geothermal energy totaled approximately 0.34 quadrillion BTUs, representing about 5 percent of energy from renewable sources and 0.35 percent from all energy sources, having increased only slightly since 2000,¹⁸ although that amount alone effectively offsets nearly 9 million tons of carbon emissions every year.¹⁹

Advantages: Geothermal energy can be found in many areas, particularly in the western United States, as indicated by the Department of Energy. The total amount of geothermal energy available in the U.S. varies but has been estimated as high as 13 million quadrillion BTUs (quads), over ten thousand times the current energy use of the country (about 95 quads in 2005), although only a small portion of that is recoverable and the processes that use it are not 100 percent efficient.²⁰

Disadvantages: While geothermal energy is present almost worldwide, its accessibility varies by location in that some areas have high temperature water relatively close to the surface and others do not, so its cost will vary and in some locations it will simply be too deep to be a viable option. From an environmental quality standpoint, the water extracted for geothermal energy contains hydrogen-sulfide gas which is a nuisance and could be potentially hazardous if released in significant quantities. Additionally, the large amount of dissolved minerals in water from deep geological sources can be corrosive and cause scaling, or mineral buildup, on machinery and in piping.

New Technology: Much of the work on geothermal energy is associated with extracting more energy in a wider variety of locations with minimal environmental impact. This includes machines that use the extracted energy more efficiently, materials and processes that avoid many of the problematic corrosive and scaling properties of mineral-laden water from within the earth’s crust, and devices that prevent unnecessary release of dissolved gases. Newer processes have been shown to eliminate 99.9 percent of dissolved hydrogen-sulfide and others can largely remove dissolved minerals such as salt and silicates.²¹

Biomass

Overview: The term “biomass” is commonly used in reference to any energy source derived from organic matter that is not a fossil fuel, including plants, wood, waste pump from paper mills, animal waste, landfill waste gases, and even municipal yard waste. Liquid biofuels produced from plants, which are discussed in the AAAS Biofuels Policy Brief, are not currently used for electricity generation in the U.S. and are considered an "open-loop" biofuel that is different from biomass fuels. The use of "closed-loop" biomass fuels for producing electricity includes burning organic waste products from paper mills, lumber mills, farms, and other activities as well as landfill gas. In 2004, biomass made up about 13 percent of electrical generation from renewables and 47 percent of total renewable energy. The total mass of material consumed for energy production, excluding that used for closed-loop biofuels such as ethanol, was approximately 160 million dry tons.²²

Advantages: Using organic waste products for fuel is relatively inexpensive and reduces carbon emissions because it prevents biogenic decomposition of organic material in the environment, which would produce large amounts of methane, a more potent greenhouse gas. In their total cycle, biomass fuels can remove at least as much carbon from the atmosphere than they release through their combustionm, making them carbon neutral and in some cases carbon negative. Using biomass as fuel also prevents its disposal by open burning, which releases a great deal more hazardous pollutants into the air and provides for no recovery of the energy released.

Disadvantages: Like any fuel source that is combusted, biomass results in air pollution such as ash, soot, nitrous oxide, sulfur dioxide, carbon monoxide, and other chemicals that must be controlled, incurring extra costs. Biomass is also relatively limited in quantity since its availability is dependent on the number of facilities providing waste material, although studies indicate that could be as much as 370 million tons from forest lands and 87 million tons of agricultural waste.²³ Closed-loop biomass could have varying levels of disadvantage depending on which crops are used and how they are harvested. Using food crops for fuel production has been connected with disrupting global food markets and altering prices while the energy used to produce and process biofuels can result in a fuel that is actually more carbon-intensive than a petroleum equivalent. The biofuels policy brief has more.

New Technology: Much of the new technological development in the area of biomass energy has focused on new methods of producing liquid biofuels from a broader variety of plant matter and waste products, although there has also been work done on developing cleaner and more efficient biomass power plants.

Efficiency

Overview: While not a source of energy, improvements in efficiency, both in generation methods and end-use consumption, can dramatically reduce the amount of energy used on a large scale. For this reason, efficiency is sometimes referred to as one of the great untapped resources for addressing climate change and has resulted in concepts like “negawatts,” popularized by the physicist Amory Lovins in 1989, referring to energy that doesn’t have to be produced because of improvements in efficiency.²⁴ In all, of the 41.8 quads (quadrillion BTUs) of energy resources used in the U.S. in 2006 for electricity production, nearly two thirds of it was lost in conversion and transmission, meaning that only about 13.8 quads of electricity was used by customers,²⁵ demonstrating the tremendous reductions in energy demand that could be realized simply by making improvements in how electricity is generated and distributed. Further demand reductions can be made on the end-use side by making efficiency improvements to appliances, heating systems, and other electrical equipment supplied by the grid.

Advantages: Improvements in efficiency can pay themselves over time, meaning the costs of paying for new technology are more than made up for by reduced energy bills.

Drawbacks: Reduces the use of, but does not replace, energy production from fossil fuels. In addition, some of the technology needed to make significant improvements, particularly in the area of long-distance electrical transmission, are not yet cost competitive with existing technology.

New Technology: Many of the improvements made so far have simply been refinements to familiar technology, such as refrigerators, air conditioners, furnaces, and many household appliances. The federal government in the past has been involved in promoting the development of such technology through programs such as Energy Star, which applies more stringent efficiency standards to products that bear its label. The EPA estimated that the program prevented nearly 40 million tons of CO2 emissions in 2007 and has more than doubled the benefits it provides since 2000.²⁶

Examples of larger scale efforts include utilizing the waste heat of industrial processes and electrical power generation that would otherwise be discharged to the environment and changes in building design to minimize heating and air conditioning demands, reduce electricity use from lighting, and reduce water consumption. Examples outside the government include the Leadership in Energy and Environmental Design (LEED) program established by the U.S. Green Building Council, which has become a recognized standard for environmentally sustainable building design.

A related efficiency measure that has gained recognition at the state level is demand-side energy management, which aims to reduce the amount of power used at peak times. In addition to energy efficiency incentive programs, all but a few states have incentives for development of demand response programs, which improve reliability and prevent brownouts by reducing load on the grid at peak times. At the federal level, the 2003 energy bill required advanced metering to be in place in federal buildings by 2010, which would help determine power use more accurately and identify areas for targeted efficiency improvement. The federal government, through DOE's Office of Energy Efficiency and Renewable Energy (EERE) is also exploring the benefits of distributed energy, which reduces demand on the grid by generating power on-site, and combined heat and power systems.

Technology that promises to drastically reduce transmission losses from electrical generation over long distances is also beginning to enter the market. Replacement of copper wire with combinations of other metals can provide what is commonly referred to as "high temperature superconductivity" or a near-zero electrical resistance at temperatures above what is typically required for superconductivity to occur. The first system deployed in the market was built by American Superconductor for the Long Island Power Authority in New York and started operation in July 2008, providing enough capacity for about 300,000 homes. While the cables require temperatures in the range of -210 to -200 degrees Celsius to achieve their low resistance, which is provided by cooling them with liquid nitrogen, the company estimates that over the long-run the improved efficiency will make up for the cost of cooling and higher price of the metals used in the cables since they can conduct approximately 150 times the amount of electricity of copper cables.²⁷

Policy Options to Encourage Renewable Energy Growth

Incentives

Various federal and state measures are in place to provide incentives for electrical utilities to generate power from renewable sources and for businesses and individual consumers to use it. The most commonly mentioned federal measure is the Federal Production Tax Credit (PTC), which provides a credit equal to 1.5 cents times the number of kilowatt-hours of electricity produced by qualified sources, including wind, closed and open-loop biomass, geothermal, solar, small irrigation power, municipal solid waste, and some hydroelectric sources.²⁸ However, the credit phases out for a given power source when the price charged to consumers rises above 8 cents/KWh and the entire PTC provision must be periodically renewed by Congress.

The federal PTC expired in December of 2007 and was renewed as part of the Emergency Economic Stabilization Act of 2008 (H.R.1424). The bill also added a PTC for power generated by marine and hydrokinetic sources like waves, tides, and currents, as long as they do not use dams or other forms of water impoundment. Other fiscal incentive programs for use the of renewables include the grants authorized to encourage biomass use under the Energy Policy Act of 2005, which totaled $50 million through 2016,²⁹ among other grant and guaranteed loan programs for renewable energy projects. The Energy Independence and Security Act of 2007 did not provide new incentives for renewable electricity production, although it did repeal tax subsidies for oil and gas.³⁰

Looking specifically to encourage developement of geothermal energy resources, the Department of the Interior completed a resource management plan for untapped geothermal energy sources in the Western United States, which would allow for an expidited and simplified system of leasing federal lands for geothermal energy production. It is estimated that the new development scenario could provide up to 5,500 MW of new geothermal generation in 12 states by 2015 and another 6,600 MW by 2025.³¹

More recently, the American Recovery and Reinvestment Act of 2009 (H.R.1), also known as the stimulus bill, included $6 billion in renewable energy loan guarantees, $3.1 billion for state energy efficiency and renewable energy programs, and $4.5 billion for investment in smart grid infrastructure.³² These measures may somewhat mitigate the large drop in new renewable energy investment caused by the financial crisis, which has been projected by trade groups at 30 to 50 percent in 2009 for wind and solar alone.³³

For more information on various incentives offered:
Federal
State

Mandatory Quotas:

While the nation has a renewable fuels standard, as set in the Energy Independence and Security Act of 2007 (P.L. 110-140, H.R. 6), the act does not include a Renewable Portfolio Standard (RPS) that would have established quotas for the percentage of the nation’s energy coming from renewable sources.³⁴ However, the federal government has set several quotas for the percentage of its own energy consumption that must come from renewable sources. Under the Energy Policy Act of 2005, the level is at least 7.5 percent by 2013³⁵ and an executive order mandated that at least half the renewable energy consumed in a given year must come from new renewable sources.³⁶ These sources include solar, wind, geothermal, hydroelectric, and biomass as well as waste-to-energy and landfill gas.

Analysis of the potential effects of a 25 percent RPS performed in 2007 showed a reduction in carbon dioxide emissions of 14 percent below the business-as-usual estimate for 2025, an average increase in retail electricity rates of 6.2 percent by 2030 (from 8.0 cents/KWh to 8.5), and an increase in household electricity expenditures of 1.5 percent by 2030 ($30 per household, annually).³⁷

While the federal government does not have an RPS, the Obama administration's energy agenda includes national renewable energy goals of 10 percent by 2012 and 25 percent by 2025. In addition, many states have already enacted standards of their own. Examples can be found at the link below:

State Renewable Portfolio Standards

Research and Development

In the United States:

In the U.S., government research on renewable energy is conducted mainly by the Department of Energy’s National Renewable Energy Laboratory (NREL) although the Department of Energy, Department of Agriculture, and other federal and state agencies also conduct a great deal of research.

Bioenergy – Several policy measures have been implemented over the last decade to stimulate the development in the field of bioenergy. This includes the creation of the Interagency Council on Biobased Products and Bioenergy and an accompanying advisory council under Executive Order 13134 in 1999, which was shortly followed be the Biomass Research and Development Act of 2000. This dedicated about one third of the $219 million in authorized research funding through 2015 to activities including power generation and integrating biomass processing capability into existing facilities.³⁸ Biomass R&D funding in the federal budget has increased substantially in recent years, rising to $225 million in total funding for 2009, up from $82 million in 2006.³⁹

Geothermal – The Department of Energy has several programs dedicated to development of geothermal energy by its own laboratories and by private firms through its “Geo-Powering the West” program. The 2007 energy bill dedicated $90 million annually for federal R&D on geothermal energy.⁴⁰

Solar – The major Department of Energy program involved with development of solar technology its Solar America Initiative, which provides funding and research collaboration for the development of solar technology. The total amount allocated to solar energy R&D in the 2009 federal budget was $156 million, down slightly from 2008.⁴¹

Wind and Hydro – The federal government has largely ceased R&D on wind and hydropower although plans are being developed to begin exploration of new sources of hydropower, including wave and tidal energy, a requirement of the Energy Independence and Security Act of 2007. The 2009 federal R&D budget outlays for wind and hydropower were $53 million and $3 million, respectively.⁴²

Efficiency - Research and development on energy efficiency is spread across a variety of programs, although the specific office at the Department of Energy that addresses it is the Office of Energy Efficiency and Renewable Energy (EERE). In addition, several national laboratories have superconductivity research programs, including the National Renewable Energy Laboratory (NREL), Oak Ridge National Laboratory, and Los Alamos National Laboratory. R&D focusing specifically on grid management occurs at several federally administered facilities, in particular the Electricity Infrastructure Operations Center (EIOC) at Pacific Northwest National Laboratory. Federal R&D funding for electricity reliability and deliverability technology in the FY 2009 budget was $100 million, down about 10 percent from 2008.⁴³

Others - Although not often considered renewable due to the large amounts of energy needed to create it, hydrogen may still see use as a fuel, if only as a storage carrier for other sources of energy such as solar or wind, which do not produce energy constantly. A recent discovery at an MIT lab has yielded a new catalyst that has the potential to dramatically improve the efficiency with which solar energy can be used to produce hydrogen and oxygen. The catalyst also avoids the harsh chemical conditions and expensive materials, such as platinum, that were required before. Such advancements in hydrogen technology could largely eliminate the barriers to making hydrogen fuel cells a viable power source, even if just for localized uses such as emergency generators and remote power stations.

For more inforation on federal funding for energy R&D, see Chapter 8 of AAAS Report XXXIII: Research and Development FY 2009 and for updates, see the website of the AAAS R&D Budget and Policy Program.