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Gale Encyclopedia of US History:

Renewable Energy

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Wood, wind, water, and sun power have been used for cooking, heating, milling, and other tasks for millennia. During the Industrial Revolution of the eighteenth and early nineteenth centuries, these forms of renewable energy were replaced by fossil fuels such as coal and petroleum. At various times throughout the nineteenth and twentieth centuries, people believed that fossil fuel reserves would be exhausted and focused their attentions on sources of renewable energy. This led to experiments with solar steam for industry and solid wood, methanol gas, or liquid biofuels for engines. Attention has refocused on renewable energy sources since the 1960s and 1970s, not only because of concern over fossil fuel depletion, but also because of apprehension over acid rain and global warming from the accumulation of carbon dioxide in the atmosphere.

Acid rain is clearly the result of the use of fossil fuels, and most authoritative climatologists also believe that these fuels are contributing to global warming. Many scientists and environmentalists have, therefore, urged a global switch to renewable energy, which derives from the sun or from processes set in motion by the sun. These energy forms include direct use of solar power along with windmills, hydroelectric dams, ocean thermal energy systems, and biomass (solid wood, methane gas, or liquid fuels). Renewable energy thus differs not only from fossil energy sources such as petroleum, gas, and coal, but also from nuclear energy, which usually involves dividing uranium atoms.

In the early 1990s, one-fifth of worldwide energy use was renewable, with by far the largest portion of this coming from fuel wood and biomass. Hydroelectric dams made up most of the rest. More than half the world's population relied on wood for cooking and heating, and although wood is generally considered to be renewable, excessive reliance has long been recognized as a cause of deforestation. Forests disappear faster than they can be renewed by natural processes. Energy "crops" —for example, fast-growing acacia or eucalyptus trees planted for fuel wood in the Third World—and more efficient wood stoves may be useful to poor, wood-reliant nations.

Solar energy is a term for many techniques and systems. The sun's energy can be trapped under glass in a greenhouse or within solar panels that heat water. It can also be concentrated in a trough or parabolic collector. In arid climates a small version of a concentrator is sometimes used to substitute for wood. Although economical, it is unreliable, hard to transport, and difficult to operate. Larger concentrators can produce steam economically for industry or for electric utilities in some climates. Another form of solar energy comes from photovoltaic cells mounted on panels. These panels are economical for all kinds of remote power needs, from cheap hand calculators to mountaintop navigational beacons to orbiting satellites. Costs have dropped dramatically since the mid-1970s, from hundreds of thousands of dollars to several thousands per installed kilowatt, and are expected to drop to under a thousand dollars early in the twenty-first century. At some point they may become competitive with nuclear and fossil energy.

Water power has been well known since its use in the Egyptian and classical Greek civilizations, and at the outset of the Industrial Revolution, it was widely used in Europe and the Americas to grind grain and run looms and in other small-scale industrial processes. Today water power is by far the cheapest of all fossil, nuclear, and renewable forms of energy for producing electricity, but the ecological disruptions caused by hydroelectric dams have caused many environmental controversies. Ocean energy takes advantage of the movement of water in tides or waves or of the temperature difference between sun-heated surface water and cold deep water. A few tidal energy projects have been built, but this form of energy production is expensive and remains largely experimental. Like tidal energy, geothermal energy is produced by continuous natural processes not directly related to solar cycles. Geo-thermal energy takes advantage of hot water trapped deep inside the earth to produce electricity or heat for homes and industry.

Wind power has been used for grinding grain, pumping water, and powering sawmills since the Middle Ages, and thousands of windmills once dotted coastal areas of northern Europe. Water-pumping windmills were a fixture in the American Midwest well into the twentieth century. Windmills are returning in a high-tech form in places like Altamont Pass in California, where they produce electricity. They are widely used for pumping water in the Third World.

Biomass energy involves a wide range of low and high technologies, from wood burning to use of manure, sea kelp, and farm crops to make gas and liquid biofuels. Brazil leads the world in use of pure ethyl alcohol derived from sugarcane as a replacement for petroleum. A common fuel in the United States is corn-derived ethyl alcohol, which is used as a low-pollution octane booster in a 10-percent blend with gasoline called "gasohol." Another form of renewable energy used in the rural Third World is the gas-producing biogas digester. Human and animal wastes are mixed with straw and water in an airless underground tank made of brick or cement. Methane gas is siphoned from the tank to a cooking stove. Meanwhile, the tank gets hot enough to kill disease-causing bacteria, which is an important sanitary improvement in many countries. Over the past few decades, 5 million biogas tanks have been built in China and half a million in India.

Renewable energy resources are cleaner and far more abundant than fossil resources, but they tend to be dispersed and more expensive to collect. Many of them, such as wind and solar energy, are intermittent in nature, making energy storage or distributed production systems necessary. Therefore, the direct cost of renewable energy is generally higher than the direct cost of fossil fuels. At the same time, fossil fuels have significant indirect or external costs, such as pollution, acid rain, and global warming. How to account for these external costs and assign the savings to renewable energy is a matter of continued policy debate. Another policy issue is research and development support. Conventional forms of energy, such as fossil fuels and nuclear power, receive more financial support from the federal government than does renewable energy. U.S. government policy toward renewable energy has been a roller coaster of support and neglect. By the end of President Jimmy Carter's administration in 1981, federal contributions to research in solar photovoltaics, solar thermal energy, solar buildings, biofuels, and wind energy research had soared to almost $500 million, but by 1990 the figure was only $65 million. A global transition to renewable energy will have to include developing nations, where energy use in proportion to the world total grew from 20 percent in 1970 to 3l percent in 1990.

Bibliography

Berinstein, Paula. Alternative Energy: Facts, Statistics, and Issues. Westport, Conn.: Oryx Press, 2001.

Blackburn, John O. The Renewable Energy Alternative: How the United States and the World Can Prosper Without Nuclear Energy or Coal. Durham, N.C.: Duke University Press, 1987.

Butti, Ken, and John Perlin. A Golden Thread: 2,500 Years of Solar Architecture and Technology. New York: Van Nostrand Reinhold, 1980.

Flavin, Christopher. Beyond the Petroleum Age: Designing a Solar Economy. Washington, D.C.: Worldwatch Institute, 1990.

Kovarik, Bill. Fuel Alcohol: Energy and Environment in a Hungry World. London: International Institute for Environment and Development, 1982.

Sørensen, Bent. Renewable Energy: Its Physics, Engineering, Use, Environmental Impact, Economy and Planning Aspects. San Diego, Calif.: Academic Press, 2000.

—Bill Kovarik/H. S.

Wikipedia on Answers.com:

Renewable energy

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Burbo Bank Offshore Wind Farm, at the entrance to the River Mersey in North West England, United Kingdom.
Nellis Solar Power Plant, 14 MW power plant installed 2007 in Nevada, USA.
Renewable energy
Wind turbine

Biofuel
Biomass
Geothermal
Hydroelectricity
Solar energy
Tidal power
Wave power
Wind power

Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable (naturally replenished). About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from hydroelectricity. New renewables (small hydro, modern biomass, wind, solar, geothermal, and biofuels) accounted for another 3% and are growing very rapidly.[1] The share of renewables in electricity generation is around 19%, with 16% of global electricity coming from hydroelectricity and 3% from new renewables.[1]

Wind power is growing at over 20% annually, with a worldwide installed capacity of 238,000 megawatts (MW) at the end of 2011,[2][3][4] and is widely used in Europe, Asia, and the United States.[5] Since 2004, photovoltaics passed wind as the fastest growing energy source, and since 2007 has more than doubled every two years. At the end of 2011 the photovoltaic (PV) capacity worldwide was 67,000 MW, and PV power stations are popular in Germany and Italy.[6] Solar thermal power stations operate in the USA and Spain, and the largest of these is the 354 MW SEGS power plant in the Mojave Desert.[7] The world's largest geothermal power installation is the Geysers in California, with a rated capacity of 750 MW. Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugarcane, and ethanol now provides 18% of the country's automotive fuel.[8] Ethanol fuel is also widely available in the USA.

While many renewable energy projects are large-scale, renewable technologies are also suited to rural and remote areas, where energy is often crucial in human development.[9] As of 2011, small solar PV systems provide electricity to a few million households, and micro-hydro configured into mini-grids serves many more. Over 44 million households use biogas made in household-scale digesters for lighting and/or cooking, and more than 166 million households rely on a new generation of more-efficient biomass cookstoves.[10] United Nations' Secretary-General Ban Ki-moon has said that renewable energy has the ability to lift the poorest nations to new levels of prosperity.[11]

Climate change concerns, coupled with high oil prices, peak oil, and increasing government support, are driving increasing renewable energy legislation, incentives and commercialization.[12] New government spending, regulation and policies helped the industry weather the global financial crisis better than many other sectors.[13] According to a 2011 projection by the International Energy Agency, solar power generators may produce most of the world’s electricity within 50 years, dramatically reducing the emissions of greenhouse gases that harm the environment.[14]

Contents

Overview

Global renewable power capacity excluding hydro[15]

Renewable energy flows involve natural phenomena such as sunlight, wind, tides, plant growth, and geothermal heat, as the International Energy Agency explains:[16]

Renewable energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly from the sun, or from heat generated deep within the earth. Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources.

Renewable energy replaces conventional fuels in four distinct areas: electricity generation, hot water/space heating, motor fuels, and rural (off-grid) energy services:[17]

  • Power generation. Renewable energy provides 19% of electricity generation worldwide. Renewable power generators are spread across many countries, and wind power alone already provides a significant share of electricity in some areas: for example, 14% in the U.S. state of Iowa, 40% in the northern German state of Schleswig-Holstein, and 20% in Denmark. Some countries get most of their power from renewables, including Iceland and Paraguay (100%), Norway (98%), Brazil (86%), Austria (62%), New Zealand (65%), and Sweden (54%).[18]
  • Heating. Solar hot water makes an important contribution to renewable heat in many countries, most notably in China, which now has 70% of the global total (180 GWth). Most of these systems are installed on multi-family apartment buildings and meet a portion of the hot water needs of an estimated 50–60 million households in China. Worldwide, total installed solar water heating systems meet a portion of the water heating needs of over 70 million households. The use of biomass for heating continues to grow as well. In Sweden, national use of biomass energy has surpassed that of oil. Direct geothermal for heating is also growing rapidly.[18]
  • Transport fuels. Renewable biofuels have contributed to a significant decline in oil consumption in the United States since 2006. The 93 billion liters of biofuels produced worldwide in 2009 displaced the equivalent of an estimated 68 billion liters of gasoline, equal to about 5% of world gasoline production.[18]

In international public opinion surveys there is strong support for promoting renewable sources such as solar power and wind power, requiring utilities to use more renewable energy (even if this increases the cost), and providing tax incentives to encourage the development and use of such technologies. There is substantial optimism that renewable energy investments will pay off economically in the long term.[19]

Mainstream forms of renewable energy

Wind power

Main article: Wind power
A wind farm located in Manjil, Iran.

Airflows can be used to run wind turbines. Modern wind turbines range from around 600 kW to 5 MW of rated power, although turbines with rated output of 1.5–3 MW have become the most common for commercial use; the power output of a turbine is a function of the cube of the wind speed, so as wind speed increases, power output increases dramatically.[20] Areas where winds are stronger and more constant, such as offshore and high altitude sites, are preferred locations for wind farms. Typical capacity factors are 20-40%, with values at the upper end of the range in particularly favourable sites.[21][22]

Globally, the long-term technical potential of wind energy is believed to be five times total current global energy production, or 40 times current electricity demand. This could require wind turbines to be installed over large areas, particularly in areas of higher wind resources. Offshore resources experience average wind speeds of ~90% greater than that of land, so offshore resources could contribute substantially more energy.[23]

Hydropower

See also: Hydroelectricity and Hydropower
Grand Coulee Dam is a hydroelectric gravity dam on the Columbia River in the U.S. state of Washington. The dam supplies four power stations with an installed capacity of 6,809 MW and is the largest electric power-producing facility in the United States.

Energy in water can be harnessed and used. Since water is about 800 times denser than air, even a slow flowing stream of water, or moderate sea swell, can yield considerable amounts of energy. There are many forms of water energy:

Solar energy

See also: Solar energy, Solar power, and Solar thermal energy
Monocrystalline solar cell.

Solar energy is the energy derived from the sun through the form of solar radiation. Solar powered electrical generation relies on photovoltaics and heat engines. A partial list of other solar applications includes space heating and cooling through solar architecture, daylighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes.

Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.

Biomass

Biomass (plant material) is a renewable energy source because the energy it contains comes from the sun. Through the process of photosynthesis, plants capture the sun's energy. When the plants are burnt, they release the sun's energy they contain. In this way, biomass functions as a sort of natural battery for storing solar energy. As long as biomass is produced sustainably, with only as much used as is grown, the battery will last indefinitely.[24]

In general there are two main approaches to using plants for energy production: growing plants specifically for energy use (known as first and third-generation biomass), and using the residues (known as second-generation biomass) from plants that are used for other things. See biobased economy. The best approaches vary from region to region according to climate, soils and geography.[24]

Biofuel

Main article: Biofuel
Brazil has bioethanol made from sugarcane available throughout the country. Shown a typical Petrobras gas station at São Paulo with dual fuel service, marked A for alcohol (ethanol) and G for gasoline.

Biofuels include a wide range of fuels which are derived from biomass. The term covers solid biomass, liquid fuels and various biogases.[25] Liquid biofuels include bioalcohols, such as bioethanol, and oils, such as biodiesel. Gaseous biofuels include biogas, landfill gas and synthetic gas.

Bioethanol is an alcohol made by fermenting the sugar components of plant materials and it is made mostly from sugar and starch crops. With advanced technology being developed, cellulosic biomass, such as trees and grasses, are also used as feedstocks for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil.

Biodiesel is made from vegetable oils, animal fats or recycled greases. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe.

Biofuels provided 2.7% of the world's transport fuel in 2010.[26]

Geothermal energy

Main article: Geothermal energy
Steam rising from the Nesjavellir Geothermal Power Station in Iceland.

Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%).[27] The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective geothermal originates from the Greek roots geo, meaning earth, and thermos, meaning heat.

The heat that is used for geothermal energy can be stored deep within the Earth, all the way down to Earth’s core – 4,000 miles down. At the core, temperatures may reach over 9,000 degrees Fahrenheit. Heat conducts from the core to surrounding rock. Extremely high temperature and pressure cause some rock to melt, which is commonly known as magma. Magma convects upward since it is lighter than the solid rock. This magma then heats rock and water in the crust, sometimes up to 700 degrees Fahrenheit [28]

From hot springs, geothermal energy has been used for bathing since Paleolithic times and for space heating since ancient Roman times, but it is now better known for electricity generation.

Renewable energy commercialization

Main article: Renewable energy commercialization

Growth of renewables

Renewable power generation and capacity as a proportion of change in global power supply[29]
Growth of wind power and photovoltaics

From the end of 2004, worldwide renewable energy capacity grew at rates of 10–60% annually for many technologies. For wind power and many other renewable technologies, growth accelerated in 2009 relative to the previous four years.[17] More wind power capacity was added during 2009 than any other renewable technology. However, grid-connected PV increased the fastest of all renewables technologies, with a 60% annual average growth rate.[17] In 2010, renewable power consisted about a third of the newly built power generation capacities.[29] By 2014 the installed capacity of photovoltaics will likely exceed that of wind, but due to the lower capacity factor of solar, the energy generated from photovoltaics is not expected to exceed that of wind until 2015.

Selected renewable energy indicators[4]
Selected global indicators 2008 2009 2010
Investment in new renewable capacity (annual) 130 160 211 billion USD
Renewables power capacity (existing) 1,140 1,230 1,320 GWe
Hydropower capacity (existing) 950 980 1,010 GWe
Wind power capacity (existing) 121 159 198 GWe
Solar PV capacity (grid-connected) 16 23 40 GWe
Solar hot water capacity (existing) 130 160 185 GWth
Ethanol production (annual) 67 76 86 billion liters
Countries with policy targets
for renewable energy use		 79 89 98

Scientists have advanced a plan to power 100% of the world's energy with wind, hydroelectric, and solar power by the year 2030.[30][31]

According to a 2011 projection by the International Energy Agency, solar power generators may produce most of the world’s electricity within 50 years, dramatically reducing the emissions of greenhouse gases that harm the environment. Cedric Philibert, senior analyst in the renewable energy division at the IEA said: “Photovoltaic and solar-thermal plants may meet most of the world’s demand for electricity by 2060 -- and half of all energy needs -- with wind, hydropower and biomass plants supplying much of the remaining generation”. “Photovoltaic and concentrated solar power together can become the major source of electricity,” Philibert said.[14]

Economic trends

All forms of energy are expensive, but as time progresses, renewable energy generally gets cheaper,[32][33] while fossil fuels generally get more expensive. A 2011 IEA report said: "A portfolio of renewable energy technologies is becoming cost-competitive in an increasingly broad range of circumstances, in some cases providing investment opportunities without the need for specific economic support," and added that "cost reductions in critical technologies, such as wind and solar, are set to continue."[34]

The International Solar Energy Society argues that renewable energy technologies and economics will continue to improve with time, and that they are "sufficiently advanced at present to allow for major penetrations of renewable energy into the mainstream energy and societal infrastructures".

Hydroelectricity

See also: List of largest hydroelectric power stations
Three Gorges Dam (left), Gezhouba Dam (right).

The Three Gorges Dam in Hubei, China, has the world's largest instantaneous generating capacity (22,500 MW), with the Itaipu Dam in Brazil/Paraguay in second place (14,000 MW). The giant Three Gorges Dam (22,500 MW when completed) is operated jointly with the much smaller Gezhouba Dam (3,115 MW). As of 2009, the total generating capacity of this two-dam complex is 21,515 MW. The whole project is planned to be completed in 2012, when the total generating capacity will be 25,615 MW. In 2008, this complex generated 97.9 TWh of electricity (80.8 TWh from the Three Gorges Dam and 17.1 TWh from the Gezhouba Dam), which is 3.4% more power in one year than the 94.7 TWh generated by Itaipu in 2008.

Wind power market

See also: List of onshore wind farms and List of offshore wind farms
Wind power: worldwide installed capacity [35]
Fenton Wind Farm at sunrise

Wind power is growing at over 20% annually, with a worldwide installed capacity of 238,000 MW at the end of 2011,[2][3][4] and is widely used in Europe, Asia, and the United States.[5][36] Several countries have achieved relatively high levels of wind power penetration, such as 21% of stationary electricity production in Denmark,[37] 18% in Portugal,[37] 16% in Spain,[37] 14% in Ireland[38] and 9% in Germany in 2010.[26][37] As of 2011, 83 countries around the world are using wind power on a commercial basis.[26]

Top 10 wind power countries[39][37]
Country Total capacity
end 2009 (MW)		 Total capacity
June 2010 (MW)		 Total capacity
end 2010 (MW)		 Total capacity
June 2011 (MW)
China 26,010 33,800 44,733 52,800
United States 35,159 36,300 40,180 42,432
Germany 25,777 26,400 27,215 27,981
Spain 19,149 19,500 20,676 21,150
India 10,925 12,100 13,066 14,550
Italy 4,850 5,300 5,797 6,200
France 4,521 5,000 5,660 6,060
United Kingdom 4,092 4,600 5,204 5,707
Canada 2,550 3,319 4,008 4,611
Portugal 3,357 3,465 3,734 3,960
Rest of world 21,698 24,500 26,154 29,500
Total 159,213 175,000 196,630 215,000

As of 2011, the Roscoe Wind Farm (781 MW) is the world's largest wind farm.[40] As of February 2012, the Walney Wind Farm in United Kingdom is the largest offshore wind farm in the world at 367 MW, followed by Thanet Offshore Wind Project (300 MW), also in the UK. The London Array (630 MW) is the largest project under construction. The United Kingdom is the world's leading generator of offshore wind power, followed by Denmark.[41]

There are many large wind farms under construction and these include Anholt Offshore Wind Farm (400 MW), BARD Offshore 1 (400 MW), Clyde Wind Farm (548 MW), Fântânele-Cogealac Wind Farm (600 MW), Greater Gabbard wind farm (500 MW), Lincs Wind Farm (270 MW), London Array (1000 MW), Lower Snake River Wind Project (343 MW), Macarthur Wind Farm (420 MW), Shepherds Flat Wind Farm (845 MW), and the Sheringham Shoal (317 MW).

New generation of solar thermal plants

Solar Towers from left: PS10, PS20.
Main article: List of solar thermal power stations
See also: Solar power plants in the Mojave Desert

Large solar thermal power stations include the 354 MW Solar Energy Generating Systems power plant in the USA, Solnova Solar Power Station (Spain, 150 MW), Andasol Solar Power Station (Spain, 100 MW), Nevada Solar One (USA, 64 MW), PS20 solar power plant (Spain, 20 MW), and the PS10 Solar Power Plant (Spain, 11 MW).

The Ivanpah Solar Power Facility is a 392 MW solar power facility which is under construction in south-eastern California.[42] The Solana Generating Station is a 280 MW solar power plant which is under construction near Gila Bend, Arizona, about 70 miles (110 km) southwest of Phoenix. The Crescent Dunes Solar Energy Project is a 110 MW solar thermal power project currently under construction near Tonopah, about 190 miles (310 km) northwest of Las Vegas.[43]

The solar thermal power industry is growing rapidly with 1.2 GW under construction as of April 2009 and another 13.9 GW announced globally through 2014. Spain is the epicenter of solar thermal power development with 22 projects for 1,037 MW under construction, all of which are projected to come online by the end of 2010.[44] In the United States, 5,600 MW of solar thermal power projects have been announced.[45] In developing countries, three World Bank projects for integrated solar thermal/combined-cycle gas-turbine power plants in Egypt, Mexico, and Morocco have been approved.[46]

Photovoltaic market

Main article: List of photovoltaic power stations
Photovoltaic power
(GW)[6]
2005 5.4
2006 7.0
2007 9.4
2008 15.7
2009 22.9
2010 39.7
2011 67.4
Year end capacities
Okhotnykovo Solar Park in Ukraine is one of the largest photovoltaic power stations in the world.
US President Barack Obama speaks at the DeSoto Next Generation Solar Energy Center, in the USA.

Solar photovoltaic cells convert sunlight into electricity and photovoltaic production has been increasing by an average of more than 20% each year since 2002, making it a fast-growing energy technology.[47][48] While wind is often cited as the fastest growing energy source, photovoltaics since 2007 has been increasing at twice the rate of wind - an average of 63.6%/year, due to the reduction in cost. At the end of 2011 the photovoltaic (PV) capacity world-wide was 67.4 GW, a 69.8% annual increase. Top capacity countries were, in GW: Germany 24.7, Italy 12.5, Japan 4.7, Spain 4.2, the USA 4.2, and China 2.9.[6]

Many solar photovoltaic power stations have been built, mainly in Europe.[49] As of May 2012, the largest photovoltaic (PV) power plants in the world are the Charanka Solar Park (India, 214 MW), Golmud Solar Park (China, 200 MW), Agua Caliente Solar Project (USA, 100 MW), Perovo Solar Park (Ukraine, 100 MW), Sarnia Photovoltaic Power Plant (Canada, 97 MW), Brandenburg-Briest Solarpark (Germany, 91 MW), Solarpark Finow Tower (Germany, 84.7 MW), Montalto di Castro Photovoltaic Power Station (Italy, 84.2 MW), and the Eggebek Solar Park (Germany, 83.6 MW).[49]

There are also many large plants under construction. The Desert Sunlight Solar Farm is a 550 MW solar power plant under construction in Riverside County, California, that will use thin-film solar photovoltaic modules made by First Solar.[50] The Topaz Solar Farm is a 550 MW photovoltaic power plant, being built in San Luis Obispo County, California.[51] The Blythe Solar Power Project is a 500 MW photovoltaic station under construction in Riverside County, California. The California Valley Solar Ranch (CVSR) is a 250 MW solar photovoltaic power plant, which is being built by SunPower in the Carrizo Plain, northeast of California Valley.[52] The 230 MW Antelope Valley Solar Ranch is a First Solar photovoltaic project which is under construction in the Antelope Valley area of the Western Mojave Desert, and due to be completed in 2013.[53]

Many of these plants are integrated with agriculture and some use tracking systems that follow the sun's daily path across the sky to generate more electricity than fixed-mounted systems. There are no fuel costs or emissions during operation of the power stations.

However, when it comes to renewable energy systems and PV, it is not just large systems that matter. Building-integrated photovoltaics or "onsite" PV systems use existing land and structures and generate power close to where it is consumed.[54]

Biofuels for transportation

See also: Ethanol fuel and BioEthanol for Sustainable Transport

Biofuels provided 3% of the world's transport fuel in 2010.[26] Mandates for blending biofuels exist in 31 countries at the national level and in 29 states/provinces.[26] According to the International Energy Agency, biofuels have the potential to meet more than a quarter of world demand for transportation fuels by 2050.[55]

Since the 1970s, Brazil has had an ethanol fuel program which has allowed the country to become the world's second largest producer of ethanol (after the United States) and the world's largest exporter.[56] Brazil’s ethanol fuel program uses modern equipment and cheap sugarcane as feedstock, and the residual cane-waste (bagasse) is used to produce heat and power.[57] There are no longer light vehicles in Brazil running on pure gasoline. By the end of 2008 there were 35,000 filling stations throughout Brazil with at least one ethanol pump.[58]

Nearly all the gasoline sold in the United States today is mixed with 10% ethanol, a mix known as E10,[59] and motor vehicle manufacturers already produce vehicles designed to run on much higher ethanol blends. Ford, Daimler AG, and GM are among the automobile companies that sell “flexible-fuel” cars, trucks, and minivans that can use gasoline and ethanol blends ranging from pure gasoline up to 85% ethanol (E85). By mid-2006, there were approximately 6 million E85-compatible vehicles on U.S. roads.[60] The challenge is to expand the market for biofuels beyond the farm states where they have been most popular to date. Flex-fuel vehicles are assisting in this transition because they allow drivers to choose different fuels based on price and availability. The Energy Policy Act of 2005, which calls for 7.5 billion US gallons (28,000,000 m3) of biofuels to be used annually by 2012, will also help to expand the market.[60]

Geothermal energy commercialization

The West Ford Flat power plant is one of 22 power plants at The Geysers.
See also: Geothermal energy in the United States

Geothermal power is cost effective, reliable, sustainable, and environmentally friendly,[61] but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have dramatically expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels. As a result, geothermal power has the potential to help mitigate global warming if widely deployed in place of fossil fuels.

The International Geothermal Association (IGA) has reported that 10,715 MW of geothermal power in 24 countries is online, which is expected to generate 67,246 GWh of electricity in 2010.[62] This represents a 20% increase in geothermal power online capacity since 2005. IGA projects this will grow to 18,500 MW by 2015, due to the large number of projects presently under consideration, often in areas previously assumed to have little exploitable resource.[62]

In 2010, the United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants;[63] the largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California.[64] The Philippines follows the US as the second highest producer of geothermal power in the world, with 1,904 MW of capacity online; geothermal power makes up approximately 18% of the country's electricity generation.[63]

Developing country markets

Main article: Renewable energy in developing countries
Solar cookers use sunlight as energy source for outdoor cooking.

Renewable energy can be particularly suitable for developing countries. In rural and remote areas, transmission and distribution of energy generated from fossil fuels can be difficult and expensive. Producing renewable energy locally can offer a viable alternative.[65]

Technology advances are opening up a huge new market for solar power: the approximately 1.3 billion people around the world who don't have access to grid electricity. Even though they are typically very poor, these people have to pay far more for lighting than people in rich countries because they use inefficient kerosene lamps. Solar power costs half as much as lighting with kerosene.[66] An estimated 3 million households get power from small solar PV systems.[67] Kenya is the world leader in the number of solar power systems installed per capita. More than 30,000 very small solar panels, each producing 12 to 30 watts, are sold in Kenya annually.[68]

Micro-hydro configured into mini-grids also provide power. Over 44 million households use biogas made in household-scale digesters for lighting and/or cooking, and more than 166 million households rely on a new generation of more-efficient biomass cookstoves.[10]

Renewable energy projects in many developing countries have demonstrated that renewable energy can directly contribute to poverty alleviation by providing the energy needed for creating businesses and employment. Renewable energy technologies can also make indirect contributions to alleviating poverty by providing energy for cooking, space heating, and lighting. Renewable energy can also contribute to education, by providing electricity to schools.[69]

Industry and policy trends

See also: Renewable energy commercialization and Renewable energy policy
Global New Investments in Renewable Energy[70]

U.S. President Barack Obama's American Recovery and Reinvestment Act of 2009 includes more than $70 billion in direct spending and tax credits for clean energy and associated transportation programs. Clean Edge suggests that the commercialization of clean energy will help countries around the world pull out of the current economic malaise.[13] Leading renewable energy companies include First Solar, Gamesa, GE Energy, Q-Cells, Sharp Solar, Siemens, SunOpta, Suntech Power, and Vestas.[71]

The military has also focused on the use of renewable fuels for military vehicles. Unlike fossil fuels, renewable fuels can be produced in any country, creating a strategic advantage. The US military has already committed itself to have 50% of its energy consumption come from alternative sources.[72]

The International Renewable Energy Agency (IRENA) is an intergovernmental organization for promoting the adoption of renewable energy worldwide. It aims to provide concrete policy advice and facilitate capacity building and technology transfer. IRENA was formed on January 26, 2009, by 75 countries signing the charter of IRENA.[73] As of March 2010, IRENA has 143 member states who all are considered as founding members, of which 14 have also ratified the statute.[74]

As of 2011, 119 countries have some form of national renewable energy policy target or renewable support policy. National targets now exist in at least 98 countries. There is also a wide range of policies at state/provincial and local levels.[26]

United Nations' Secretary-General Ban Ki-moon has said that renewable energy has the ability to lift the poorest nations to new levels of prosperity.[11] In October 2011, he "announced the creation of a high-level group to drum up support for energy access, energy efficiency and greater use of renewable energy. The group is to be co-chaired by Kandeh Yumkella, the chair of UN Energy and director general of the UN Industrial Development Organisation, and Charles Holliday, chairman of Bank of America".[75]

New and emerging renewable energy technologies

New and emerging renewable energy technologies are still under development and include cellulosic ethanol, hot-dry-rock geothermal power, and ocean energy.[76] These technologies are not yet widely demonstrated or have limited commercialization. Many are on the horizon and may have potential comparable to other renewable energy technologies, but still depend on attracting sufficient attention and research, development and demonstration (RD&D) funding.[76]

Cellulosic ethanol

See also: Cellulosic ethanol commercialization

Companies such as Iogen, Broin, and Abengoa are building refineries that can process biomass and turn it into ethanol, while companies such as the Verenium Corporation, Novozymes, and Dyadic International are producing enzymes which could enable a cellulosic ethanol future. The shift from food crop feedstocks to waste residues and native grasses offers significant opportunities for a range of players, from farmers to biotechnology firms, and from project developers to investors.[77]

Selected Commercial Cellulosic Ethanol Plants in the U.S.[78][79]
(Operational or under construction)
Company Location Feedstock
Abengoa Bioenergy Hugoton, KS Wheat straw
BlueFire Renewables Irvine, CA Multiple sources
Gulf Coast Energy Mossy Head, FL Wood waste
Mascoma Lansing, MI Wood
POET Emmetsburg, IA Corn cobs
SunOpta Little Falls, MN Wood chips
Xethanol Auburndale, FL Citrus peels

Ocean energy

Systems to harvest utility-scale electrical power from ocean waves have recently been gaining momentum as a viable technology. The potential for this technology is considered promising, especially on west-facing coasts with latitudes between 40 and 60 degrees:[80]

In the United Kingdom, for example, the Carbon Trust recently estimated the extent of the economically viable offshore resource at 55 TWh per year, about 14% of current national demand. Across Europe, the technologically achievable resource has been estimated to be at least 280 TWh per year. In 2003, the U.S. Electric Power Research Institute (EPRI) estimated the viable resource in the United States at 255 TWh per year (6% of demand).[80]

Scotland is home to the European Marine Energy Centre the world's first testing facility for wave and tidal machines, located in the waters around the Orkney Islands. In 2012 at the wave test site, E.ON are testing a Pelamis Wave Energy Converter machine and Aquamarine Power are testing their near-shore Oyster device. Wave farm developments are planned in Scottish waters by E.ON, ScottishPower Renewables, SSE, Pelamis Wave Power, Aquamarine Power and Aegir Wave Power, a joint venture between Pelamis and Vattenfall.[81]

The world's first commercial tidal stream generator was installed in 2007 in the narrows of Strangford Lough in Ireland. The 1.2 MW underwater tidal electricity generator, part of Northern Ireland's Environment & Renewable Energy Fund scheme, takes advantage of the fast tidal flow (up to 4 metres per second) in the lough. Although the generator is powerful enough to power a thousand homes, the turbine has minimal environmental impact, as it is almost entirely submerged, and the rotors pose no danger to wildlife as they turn quite slowly.[82]

Ocean thermal energy conversion (OTEC) uses the temperature difference that exists between deep and shallow waters to run a heat engine.

Enhanced geothermal systems

Main article: Enhanced geothermal system
Enhanced geothermal system 1:Reservoir 2:Pump house 3:Heat exchanger 4:Turbine hall 5:Production well 6:Injection well 7:Hot water to district heating 8:Porous sediments 9:Observation well 10:Crystalline bedrock

Enhanced geothermal systems are a new type of geothermal power technologies that do not require natural convective hydrothermal resources. The vast majority of geothermal energy within drilling reach is in dry and non-porous rock.[83] EGS technologies "enhance" and/or create geothermal resources in this "hot dry rock (HDR)" through hydraulic stimulation.

EGS / HDR technologies, like hydrothermal geothermal, are expected to be baseload resources which produce power 24 hours a day like a fossil plant. Distinct from hydrothermal, HDR / EGS may be feasible anywhere in the world, depending on the economic limits of drill depth. Good locations are over deep granite covered by a thick (3–5 km) layer of insulating sediments which slow heat loss.[84]

There are HDR and EGS systems currently being developed and tested in France, Australia, Japan, Germany, the U.S. and Switzerland. The largest EGS project in the world is a 25 megawatt demonstration plant currently being developed in the Cooper Basin, Australia. The Cooper Basin has the potential to generate 5,000–10,000 MW.

Experimental solar power

Concentrating photovoltaics in Catalonia, Spain
See also: Solar power#Experimental solar power

Concentrated photovoltaics (CPV) systems employ sunlight concentrated onto photovoltaic surfaces for the purpose of electricity generation. Thermoelectric, or "thermovoltaic" devices convert a temperature difference between dissimilar materials into an electric current. Space-based solar power is a theoretical design for the collection of solar power in space, for use on Earth.

Artificial photosynthesis

Artificial photosynthesis uses techniques include nanotechnology to store solar electromagnetic energy in chemical bonds by splitting water to produce hydrogen and then using carbon dioxide to make methanol.[85]

Renewable energy debate

Main article: Renewable energy debate

Renewable electricity production, from sources such as wind power and solar power, is sometimes criticized for being variable or intermittent. However, the International Energy Agency has stated that deployment of renewable technologies usually increases the diversity of electricity sources and, through local generation, contributes to the flexibility of the system and its resistance to central shocks.[86]

There have been "not in my back yard" (NIMBY) concerns relating to the visual and other impacts of some wind farms, with local residents sometimes fighting or blocking construction.[87] In the USA, the Massachusetts Cape Wind project was delayed for years partly because of aesthetic concerns. However, residents in other areas have been more positive and there are many examples of community wind farm developments. According to a town councilor, the overwhelming majority of locals believe that the Ardrossan Wind Farm in Scotland has enhanced the area.[88]

The market for renewable energy technologies has continued to grow. Climate change concerns, coupled with high oil prices, peak oil, and increasing government support, are driving increasing renewable energy legislation, incentives and commercialization.[12] New government spending, regulation and policies helped the industry weather the 2009 economic crisis better than many other sectors.[13]

Legislative and scientific definitions of renewable energy usually exclude nuclear power. However, Physicist Bernard Cohen has proposed that uranium dissolved in seawater, when used in fast neutron breeder reactors, is effectively inexhaustible, and could therefore be considered a renewable source of energy.[89][90]

See also

Portal icon Renewable energy portal
Portal icon Sustainable development portal

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Bibliography

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