Renewable energy 25784 225583411 2008-07-14T12:32:07Z Cosmo0 4648865 grammar correction: removed confusing commas {{pp-semi-vandalism|small=yes}} [[Image:Ren2006.png|thumb|right|300px|Renewable energy sources worldwide at the end of 2006. ''Source: REN21''<ref name="REN21-2007"> [http://www.ren21.net/pdf/RE2007_Global_Status_Report.pdf Global Status Report 2007] (PDF).</ref>]] {{renewable energy sources}} '''Renewable energy''' is [[energy]] generated from [[natural resource]]s&mdash;such as [[sunlight]], [[wind]], [[rain]], [[tidal energy|tides]] and [[geothermal energy|geothermal heat]]&mdash;which are [[Renewable resource|renewable]] (naturally replenished). Renewable energy technologies range from [[solar energy|solar power]], [[wind power]], [[hydroelectricity]]/[[micro hydro]], [[biomass]] and [[biofuels]] for transportation. In 2006, about 18% of global final energy consumption came from renewables, with 13% coming from traditional [[biomass]], such as [[Wood fuel|wood-burning]]. Hydropower was the next largest renewable source, providing 3%, followed by hot water/heating, which contributed 1.3%. Modern technologies, such as geothermal, wind, solar, and ocean energy together provided some 0.8% of final energy consumption.<ref name="REN21-2007"/> The technical potential for their use is very large, exceeding all other readily available sources.<ref>World Energy Assessment (2001). [http://www.undp.org/energy/activities/wea/drafts-frame.html Renewable energy technologies], chapter 7.</ref><ref>{{cite web | url= http://www.planetark.com/dailynewsstory.cfm/newsid/46325/story.htm | title= Renewables Supply 14 Pct of German Power - Industry |date= January 9, 2008 |work= |publisher= [[Reuters]] | accessdate= 2008-01-17 }} </ref> Renewable energy technologies are sometimes criticised for being [[Intermittent power source|intermittent]] or unsightly, yet the market is growing for many forms of renewable energy. Wind power is growing at the rate of 30 percent annually, with a worldwide installed capacity of over 100 GW,<ref>EWEA press release April, 2008 [http://www.ewea.org/fileadmin/ewea_documents/documents/press_releases/2008/EWEC_press_release_day_2.pdf] (PDF)</ref> and is widely used in several European countries and the [[United States]].<ref name="Glob"> [http://www.gwec.net/uploads/media/07-02_PR_Global_Statistics_2006.pdf Global wind energy markets continue to boom – 2006 another record year] (PDF).</ref> The manufacturing output of the [[photovoltaics]] industry reached more than 2,000 MW in 2006,<ref>[http://www.cleanedge.com/book/Chapter1_The_Clean_Tech_Revolution.pdf Solar Energy: Scaling Up Manufacturing and Driving Down Costs] (PDF), p. 30.</ref> and [[Photovoltaic power station|photovoltaic (PV) power stations]] are particularly popular in Germany.<ref>[http://www.pvresources.com/en/top50pv.php World's largest photovoltaic power plants]</ref> [[Solar thermal power]] stations operate in the USA and Spain, and the largest of these is the 354 MW [[SEGS]] power plant in the [[Solar power plants in the Mojave Desert|Mojave Desert]]. <ref>[http://www.osti.gov/accomplishments/pdf/DE00014520/DE00014520.pdf Solar Trough Power Plants] (PDF).</ref>. The world's largest [[geothermal power]] installation is [[The Geysers]] in California, with a rated capacity of 750 MW.<ref name = "calpine"> {{cite web | title = Calpine Corporation — The Geysers | url = http://www.geysers.com | accessdate = 2007-05-16 }}</ref> Brazil has one of the largest renewable energy programs in the world, involving production of [[ethanol fuel]] from sugar cane, and ethanol now provides 18 percent of the country's automotive fuel.<ref>[http://www.renewableenergyaccess.com/rea/news/story?id=44896 America and Brazil Intersect on Ethanol]</ref> Ethanol fuel is also widely available in the USA. While there are many large-scale renewable energy projects and production, renewable technologies are also suited to [[Remote Area Power Supply|small off-grid applications]], sometimes in [[rural]] and remote areas, where energy is often crucial in human development.<ref>World Energy Assessment (2001). [http://www.undp.org/energy/activities/wea/drafts-frame.html Renewable energy technologies], p. 221.</ref> Kenya has the world's highest household solar ownership rate with roughly 30,000 small (20–100 watt) solar power systems sold per year.<ref>[http://www.renewableenergyaccess.com/rea/news/reinsider/story?id=49617 What Solar Power Needs Now] ''Renewable Energy Access'', 13 August 2007.</ref> [[Climate change]] concerns coupled with [[Oil price increases since 2003|high oil prices]], [[peak oil]] and increasing government support are driving increasing renewable energy legislation, incentives and [[renewable energy commercialization|commercialization]]. European Union leaders reached an agreement in principle in March 2007 that 20 percent of their nations' energy should be produced from renewable fuels by 2020, as part of its drive to cut emissions of carbon dioxide, blamed in part for [[global warming]].<ref> [http://www.planetark.com/dailynewsstory.cfm/newsid/44517/story.htm news] and [http://www.europarl.europa.eu/sides/getDoc.do?type=TA&reference=P6-TA-2007-0406&language=EN&ring=A6-2007-0287 Official EP resolution of 25 September 2007 on the Road Map for Renewable Energy in Europe]</ref> Investment capital flowing into renewable energy climbed from $80 billion in 2005 to a record $100 billion in 2006.<ref name="UNEP"> United Nations Environment Programme and [http://www.newenergyfinance.com New Energy Finance Ltd.] (2007). [http://sefi.unep.org/fileadmin/media/sefi/docs/publications/SEFI_Investment_Report_2007.pdf ''Global Trends in Sustainable Energy Investment 2007: Analysis of Trends and Issues in the Financing of Renewable Energy and Energy Efficiency in OECD and Developing Countries''] (PDF), p. 3.</ref> This level of investment combined with continuing double digit percentage increases each year has moved what once was considered [[alternative energy]] to [[mainstream]]. Wind was the first to provide 1% of electricity, but solar is not far behind.<ref>[http://www.ren21.net/publications/ Global Status Report 2007]</ref> Some very large corporations such as [[BP]], [[General Electric]], [[Sharp Corporation|Sharp]], and [[Royal Dutch Shell]] are investing in the renewable energy sector.<ref> [http://www.boston.com/news/nation/washington/articles/2007/03/02/two_oil_giants_plunge_into_the_wind_business/ Two oil giants plunge into the wind business: Shell, BP intend to play major role]</ref><ref>[http://www.gepower.com/about/index.htm GE Energy]</ref> ==Main renewable energy technologies== [[Image:Alternative Energies.jpg|thumb|Three energy sources]] The majority of renewable energy technologies are directly or indirectly powered by the sun. The Earth-Atmosphere system is in equilibrium such that heat radiation into space is equal to incoming [[solar radiation]], the resulting level of energy within the Earth-Atmosphere system can roughly be described as the Earth's "climate." The hydrosphere (water) absorbs a major fraction of the incoming radiation. Most radiation is absorbed at low latitudes around the equator, but this energy is dissipated around the globe in the form of winds and ocean currents. Wave motion may play a role in the process of transferring mechanical energy between the atmosphere and the ocean through wind stress.<ref>Renewable Energy, Sorensen, Elsevier 2004</ref> Solar energy is also responsible for the distribution of precipitation which is tapped by hydroelectric projects, and for the growth of plants used to create biofuels. Renewable energy flows involve natural phenomena such as [[sunlight]], [[wind]], [[tide]]s and [[Geothermal heating|geothermal heat]], as the [[International Energy Agency]] explains: <blockquote> "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."<ref> [http://www.iea.org/textbase/nppdf/free/2000/Renew_main2003.pdf Renewable energy... into the mainstream] p. 9.</ref> </blockquote> Each of these sources has unique characteristics which influence how and where they are used. === Wind power === {{main|Wind power}} [[Image:HornsrevMOELLEDRIFT 250.jpg|thumb|220px|right|Vestas V80 wind turbines]] Airflows can be used to run [[wind turbine]]s. 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.<ref name="EWEA">{{cite web | title = Analysis of Wind Energy in the EU-25 | publisher = European Wind Energy Association | url = http://www.ewea.org/fileadmin/ewea_documents/documents/publications/WETF/Facts_Summary.pdf EWEA Executive summary |format= [[PDF]] | accessdate = 2007-03-11}}</ref> Areas where winds are stronger and more constant, such as offshore and high altitude sites, are preferred locations for wind farms. Since wind speed is not constant, a [[wind farm]]'s annual energy production is never as much as the sum of the generator nameplate ratings multiplied by the total hours in a year. The ratio of actual productivity in a year to this theoretical maximum is called the [[capacity factor]]. Typical capacity factors are 20-40%, with values at the upper end of the range in particularly favourable sites.<ref> [http://www.awea.org/faq/basicen.html How Does A Wind Turbine's Energy Production Differ from Its Power Production?] </ref><ref> [http://www.ceere.org/rerl/about_wind/RERL_Fact_Sheet_2a_Capacity_Factor.pdf Wind Power: Capacity Factor, Intermittency, and what happens when the wind doesn’t blow?] retrieved 24 January 2008.</ref> For example, a 1 megawatt turbine with a capacity factor of 35% will not produce 8,760 megawatt-hours in a year, but only 0.35x24x365&nbsp;=&nbsp;3,066&nbsp;MWh, averaging to 0.35 MW. Online data is available for some locations and the capacity factor can be calculated from the yearly output.<ref>[http://view2.fatspaniel.net/FST/Portal/LighthouseElectrical/maritime/HostedAdminView.html Massachusetts Maritime Academy — Bourne, Mass] This 660 kW wind turbine has a capacity factor of about 19%.</ref><ref>[http://www.ieso.ca/imoweb/marketdata/windpower.asp Wind Power in Ontario] These wind farms have capacity factors of about 28 to 35%.</ref> 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 large amounts of land to be used for wind turbines, particularly in areas of higher wind resources. Offshore resources experience mean wind speeds of ~90% greater than that of land, so offshore resources could contribute substantially more energy.<ref>"<cite>Offshore stations experience mean wind speeds at 80 m that are 90% greater than over land on average.</cite> [http://www.stanford.edu/group/efmh/winds/global_winds.html Evaluation of global wind power]<br />"<cite>Overall, the researchers calculated winds at 80 meters [300 feet] traveled over the ocean at approximately 8.6 meters per second and at nearly 4.5 meters per second over land [20 and 10 miles per hour, respectively].</cite>" [http://www.ens-newswire.com/ens/may2005/2005-05-17-09.asp#anchor6 Global Wind Map Shows Best Wind Farm Locations] (URL accessed [[January 30]], [[2006]]).</ref> This number could also increase with higher altitude ground-based or airborne wind turbines.<ref>"<cite>High-altitude winds could provide a potentially enormous renewable energy source, and scientists like Roberts believe [[Airborne wind turbine|flying windmills]] could put an end to dependence on fossil fuels. At {{convert|15000|ft|m}}, winds are strong and constant. On the ground, wind is often unreliable — the biggest problem for ground-based wind turbines.</cite>" [http://www.wired.com/news/planet/0,2782,67121,00.html?tw=wn_tophead_2 Windmills in the Sky] (URL accessed [[January 30]], [[2006]]).</ref> [[Wind power]] is renewable and produces no [[greenhouse gas]]es during operation, such as [[carbon dioxide]] and [[methane]]. === Water power === {{main|Hydropower}} Energy in water (in the form of motive energy or temperature differences) can be harnessed and used. Since water is about 800 times [[Density of air|denser than air]],<ref>{{cite web |url=http://wahiduddin.net/calc/calc_da_m.htm |title=Density Altitude Calculator |accessdate=2007-09-17 |author=Richard Shelquist |date=18-Oct-2005}}</ref><ref>{{cite web |url=http://www.csgnetwork.com/h2odenscalc.html |title=Water Density Calculator |accessdate=2007-09-17 |date=Copyright© 1973–2007 |publisher=CSG, Computer Support Group, Inc. and CSGNetwork.Com}}</ref> even a slow flowing stream of water, or moderate sea [[Swell (ocean)|swell]], can yield considerable amounts of energy. [[Image:Pelamis Wellenkraftwerk Portugal 3.JPG|thumb| One of 3 PELAMIS P-750 Ocean Wave Power engines in the harbour of Peniche/ Portugal.]] There are many forms of water energy: * [[Hydroelectric]] energy is a term usually reserved for large-scale hydroelectric dams. Examples are the [[Grand Coulee Dam]] in Washington State and the [[Akosombo Dam]] in Ghana. * [[Micro hydro]] systems are [[hydroelectric power]] installations that typically produce up to 100 kW of power. They are often used in water rich areas as a [[Remote Area Power Supply]] (RAPS). There are many of these installations around the world, including several delivering around 50 kW in the [[Solomon Islands]]. * [[Damless hydro]] systems derive kinetic energy from rivers and oceans without using a dam. * [[Wave power]] uses the energy in waves. The waves will usually make large [[Pontoon (boat)|pontoons]] go up and down in the water, leaving an area with reduced wave height in the "shadow". Wave power has now reached commercialization. * [[Tidal power]] captures energy from the tides in a vertical direction. Tides come in, raise water levels in a basin, and tides roll out. Around low tide, the water in the basin is discharged through a [[turbine]]. * [[Tidal stream power]] captures energy from the flow of tides, usually using underwater plant resembling a small wind turbine. Tidal stream power demonstration projects exist, and the first commercial prototype will be installed in [[Strangford Lough]] in September 2007. * [[Ocean thermal energy conversion]] (OTEC) uses the temperature difference between the warmer surface of the ocean and the colder lower recesses. To this end, it employs a [[heat engine|cyclic heat engine]]. OTEC has not been field-tested on a large scale. * [[Deep lake water cooling]], although not technically an energy generation method, can save a lot of energy in summer. It uses submerged pipes as a [[heat sink]] for [[air conditioning|climate control systems]]. Lake-bottom water is a year-round local constant of about 4&nbsp;°[[Celsius|C]]. * [[Blue energy]] is the reverse of [[desalination]]. This form of energy is in research. ===Solar energy use=== {{main|Solar energy}} [[Image:Klassieren.jpg|thumb|250px|Monocrystalline solar cell]] In this context, "solar energy" refers to energy that is collected from sunlight. Solar energy can be applied in many ways, including to: * Generate electricity using photovoltaic [[solar cells]]. * Generate electricity using [[Solar thermal energy|concentrated solar power]]. * Generate electricity by heating trapped air which rotates turbines in a [[Solar updraft tower]]. * Heat buildings, directly, through [[passive solar building design]]. * Heat foodstuffs, through [[solar oven]]s. * Heat water or air for domestic hot water and space heating needs using [[Solar hot water|solar-thermal panels]]. * Heat and cool air through use of [[solar chimney]]s. * Generate electricity in geosynchronous orbit using [[solar power satellite]]s. * [[Solar air conditioning]] === Biofuel === {{main|Biofuel}} Plants use [[photosynthesis]] to grow and produce [[biomass]]. Also known as biomatter, biomass can be used directly as fuel or to produce liquid [[biofuel]]. Agriculturally produced biomass fuels, such as [[biodiesel]], [[ethanol]] and [[bagasse]] (often a by-product of [[sugar cane]] cultivation) can be burned in [[internal combustion engine]]s or [[boiler]]s. Typically biofuel is burned to release its stored chemical energy. Research into more efficient methods of converting biofuels and other fuels into electricity utilizing fuel cells is an area of very active work. ==== Liquid biofuel ==== [[Image:EthanolPetrol.jpg|right||250px|thumb|Information on pump, California.]] Liquid biofuel is usually either a bioalcohol such as [[ethanol fuel]] or a bio-oil such as [[biodiesel]] and [[straight vegetable oil]]. Biodiesel can be used in modern diesel vehicles with little or no modification to the engine and can be made from waste and virgin vegetable and animal oil and fats ([[lipid]]s). Virgin vegetable oils can be used in modified diesel engines. In fact the Diesel engine was originally designed to run on vegetable oil rather than fossil fuel. A major benefit of biodiesel is lower emissions. The use of biodiesel reduces emission of carbon monoxide and other hydrocarbons by 20 to 40%. In some areas [[maize|corn]], [[cornstalk]]s, [[sugarbeet]]s, [[sugar cane]], and [[switchgrass]]es are grown specifically to produce [[ethanol]] (also known as grain alcohol) a liquid which can be used in [[internal combustion engine]]s and [[fuel cells]]. [[Ethanol]] is being phased into the current energy infrastructure. E85 is a fuel composed of 85% ethanol and 15% gasoline that is sold to consumers. [[Biobutanol]] is being developed as an alternative to bioethanol. There is growing international criticism about biofuels from food crops with respect to issues such as food security, environmental impacts (deforestation) and energy balance. ==== Solid biomass ==== {{main|biomass}} [[Image:Sugar cane leaves.jpg|right|thumbnail|250px|[[Sugar cane]] residue can be used as a biofuel]] Solid biomass is mostly commonly usually used directly as a combustible fuel, producing 10-20 MJ/kg of heat. Its forms and sources include [[wood fuel]], the biogenic portion of municipal solid waste, or the unused portion of field crops. Field crops may or may not be grown intentionally as an [[energy crop]], and the remaining plant byproduct used as a fuel. Most types of biomass contain energy. Even [[cow]] [[manure]], still contains two-thirds of the original energy consumed by the cow. Energy harvesting via a [[bioreactor]] is a cost-effective solution to the [[waste disposal]] issues faced by the [[dairy farm]]er, and can produce enough [[biogas]] to run a farm. With current technology, it is not ideally suited for use as a [[transportation]] fuel. Most transportation vehicles require power sources with high power density, such as that provided by internal combustion engines. These engines generally require clean burning fuels, which are generally in liquid form, and to a lesser extent, compressed [[gas]]eous phase. [[Liquid]]s are more portable because they have high energy density, and they can be pumped, which makes handling easier. This is why most transportation fuels are liquids. Non-transportation applications can usually tolerate the low power-density of external combustion engines, that can run directly on less-expensive solid biomass fuel, for combined heat and power. One type of biomass is wood, which has been used for millennia in varying quantities, and more recently is finding increased use. Two billion people currently cook every day, and heat their homes in the winter by burning biomass, which is a major contributor to man-made climate change global warming. The black soot that is being carried from Asia to polar ice caps is causing them to melt faster in the summer. In the 19th century, wood-fired steam engines were common, contributing significantly to industrial revolution unhealthy air pollution. Coal is a form of biomass that has been compressed over millennia to produce a non-renewable, highly-polluting fossil fuel. Wood and its byproducts can now be converted through process such as [[gasification]] into biofuels such as [[woodgas]], [[biogas]], methanol or ethanol fuel; although further development may be required to make these methods affordable and practical. [[Sugar cane]] [[residue]], [[wheat]] [[chaff]], [[maize|corn cobs]] and other [[Biomass|plant matter]] can be, and are, burned quite successfully. The net carbon dioxide emissions that are added to the atmosphere by this process are only from the fossil fuel that was consumed to plant, fertilize, harvest and transport the biomass. Processes to harvest biomass from short-rotation [[poplars]] and [[willows]], and perennial grasses such as [[switchgrass]], [[phalaris]], and [[miscanthus]], require less frequent cultivation and less nitrogen than from typical annual crops. [[Pelletizing]] miscanthus and burning it to generate electricity is being studied and may be economically viable.<ref name="uiuc"> [http://www.ace.uiuc.edu/pERE/conference/papers/long.pdf Biomass Crops as a Source of Renewable Energy: European Experience with Miscanthus and Projections for Illinois] (PDF).</ref> ==== Biogas ==== {{main|Biogas|Anaerobic digestion}} Biogas can easily be produced from current waste streams, such as: paper production, sugar production, sewage, animal waste and so forth. These various waste streams have to be slurried together and allowed to naturally ferment, producing methane gas. This can be done by converting current sewage plants into biogas plants. When a biogas plant has extracted all the methane it can, the remains are sometimes better suitable as fertilizer than the original biomass. Alternatively biogas can be produced via advanced waste processing systems such as [[mechanical biological treatment]]. These systems recover the recyclable elements of household waste and process the biodegradable fraction in [[anaerobic digester]]s. [[Renewable natural gas]] is a biogas which has been upgraded to a quality similar to [[natural gas]]. By upgrading the quality to that of natural gas, it becomes possible to distribute the gas to the mass market via gas grid. === Geothermal energy === {{main|Geothermal energy}} [[Image:Krafla Geothermal Station.jpg|thumb|right|250px|[[Krafla]] Geothermal Station in northeast Iceland]] Geothermal energy is energy obtained by tapping the heat of the earth itself, usually from kilometers deep into the Earth's crust. It is expensive to build a power station but operating costs are low resulting in low energy costs for suitable sites. Ultimately, this energy derives from heat in the [[Earth]]'s core. The government of [[Iceland]] states: "It should be stressed that the geothermal resource is not strictly renewable in the same sense as the hydro resource." It estimates that Iceland's geothermal energy could provide 1700 MW for over 100 years, compared to the current production of 140 MW.<ref name=heat> [http://www.geothermie.de/egec-geothernet/ci_prof/australia_ozean/new_zealand/0080.PDF RESPONSE OF WAIRAKEI GEOTHERMAL RESERVOIR TO 40 YEARS OF PRODUCTION], 2006 (pdf) Allan Clotworthy, Proceedings World Geothermal Congress 2000. (accessed [[30 March]]).</ref> The [[International Energy Agency]] classifies geothermal power as renewable.<ref> [http://www.theaustralian.news.com.au/story/0,20867,21525816-30417,00.html Geodynamics says it has the "hottest rocks on earth"]</ref> Three types of power plants are used to generate power from geothermal energy: dry steam, flash, and binary. Dry steam plants take steam out of fractures in the ground and use it to directly drive a turbine that spins a generator. Flash plants take hot water, usually at temperatures over 200&nbsp;°C, out of the ground, and allows it to boil as it rises to the surface then separates the steam phase in steam/water separators and then runs the steam through a turbine. In binary plants, the hot water flows through heat exchangers, boiling an organic fluid that spins the turbine. The condensed steam and remaining geothermal fluid from all three types of plants are injected back into the hot rock to pick up more heat. The geothermal energy from the core of the Earth is closer to the surface in some areas than in others. Where hot underground steam or water can be tapped and brought to the surface it may be used to generate electricity. Such [[geothermal power]] sources exist in certain geologically unstable parts of the world such as [[Chile]], [[Iceland]], [[New Zealand]], [[United States]], [[Philippines|the Philippines]] and [[Italy]]. The two most prominent areas for this in the United States are in the [[Yellowstone National Park|Yellowstone]] basin and in northern [[California]]. [[Iceland]] produced 170 MW geothermal power and heated 86% of all houses in the year 2000 through geothermal energy. Some 8000 MW of capacity is operational in total. There is also the potential to generate geothermal energy from [[Hot dry rock geothermal energy|hot dry rocks]]. Holes at least 3&nbsp;km deep are drilled into the earth. Some of these holes pump water into the earth, while other holes pump hot water out. The heat resource consists of hot underground radiogenic granite rocks, which heat up when there is enough sediment between the rock and the earths surface. Several companies in Australia are exploring this technology. == Renewable energy commercialization == {{main|Renewable energy commercialization}} ===Costs=== Renewable energy systems encompass a broad, diverse array of technologies, and the current status of these can vary considerably. Some technologies are already mature and economically competitive (e.g. geothermal and hydropower), others need additional development to become competitive without subsidies. This can be helped by improvements to sub-components, such as [[electric generator]]s. The table shows an overview of costs of various renewable energy technologies. For comparison with the prices in the table, electricity production from a conventional coal-fired plant costs about 4¢/kWh.<ref> {{cite book |author=Economic Analysis Division of the International Energy Agency |title=World Energy Outlook 2004 |year=2004 |format= [[PDF]] |url=http://www.iea.org/textbase/nppdf/free/2004/weo2004.pdf |accessdate=2007-09-17 |publisher= Organisation for Economic Co-operation and Development/International Energy Agency |location=Paris |pages=P.195 |quote= Figure 6.3: Indicative Mid-Term Generating Costs of New Power Plants}}</ref> Though in some G8 nations the cost can be significantly higher at 7.88p (~15¢/kWh).<ref> EDF energy, UK, general purpose charging scheme, December 2006.</ref> Achieving further cost reductions as indicated in the table below requires further technology development, market deployment, an increase in production capacities to [[mass production]] levels<ref name=WEA2004/>, and of the establishment of an [[emissions trading]] scheme and/or [[carbon tax]] which would attribute a cost to each unit of carbon emitted; thus reflecting the true cost of energy production by [[fossil fuels]] which then could be used to lower the cost/kWh of these renewable energies. {| class="wikitable" |- || || &nbsp; '''2001 energy costs''' &nbsp; || &nbsp; '''Potential future energy cost''' &nbsp; |- | align=center colspan=3 | '''Electricity''' |- || '''[[Wind power|Wind]]''' || &nbsp; 4–8 ¢/kWh || 3–10 ¢/kWh |- || '''[[Solar photovoltaics|Solar photovoltaic]]''' || 25–160 ¢/kWh || 5–25 ¢/kWh |- || '''[[Solar thermal energy|Solar thermal]]''' || 12–34 ¢/kWh || 4–20 ¢/kWh |- || '''Large [[hydropower]]''' || &nbsp; 2–10 ¢/kWh || 2–10 ¢/kWh |- || '''Small hydropower''' || &nbsp; 2–12 ¢/kWh || 2–10 ¢/kWh |- || '''[[Geothermal energy|Geothermal]]''' || &nbsp; 2–10 ¢/kWh || 1–8 ¢/kWh |- || '''[[Biomass energy|Biomass]]''' || &nbsp; 3–12 ¢/kWh || 4–10 ¢/kWh |- || '''[[Fossil fuel power plant|Coal]]''' (comparison) || &nbsp; 4 ¢/kWh || |- | align=center colspan=3 | '''Heat''' |- || '''[[Geothermal heating|Geothermal heat]]''' || 0.5–5 ¢/kWh || 0.5–5 ¢/kWh |- || '''Biomass — heat''' || 1–6 ¢/kWh || 1–5 ¢/kWh |- || '''[[Solar hot water|Low temp solar heat]]''' || 2–25 ¢/kWh || 2–10 ¢/kWh |- | colspan=3 | All costs are in 2001 US$-cent per [[kilowatt-hour]]. |- | colspan=3 | Source: World Energy Assessment, 2004 update<ref name=WEA2004>World Energy Assessment 2004 Update, (energy costs from Table 7). Available for download at its [http://www.undp.org/energy/weaover2004.htm UNDP site].</ref> |} === Wind power market increase === {{main|Wind farm}} [[Image:Prediction2007s.jpg|thumb|400px|Wind power: worldwide installed capacity and prediction 1997-2010, Source: [http://www.wwindea.org/ WWEA]]] As of April 2008, worldwide [[wind farm]] capacity was 100,000 [[megawatt]]s (MW),<ref>[http://www.worldwatch.org/node/5448?utm_campaign=vital_signs_online&utm_medium=email&utm_source=wind Wind Power Continues Rapid Rise]</ref> and wind power produced some 1.3% of global electricity consumption,<ref>World Wind Energy Association (2008). [http://www.wwindea.org/home/images/stories/pr_statistics2007_210208_red.pdf Wind turbines generate more than 1 % of the global electricity]</ref> accounting for approximately 18% of electricity use in [[Wind power in Denmark|Denmark]], 9% in [[Wind power in Spain|Spain]], and 7% in [[Wind power in Germany|Germany]].<ref>[http://www.ibtimes.com/articles/20070425/european-wind-companies-grow-in-u-s.htm European wind companies grow in U.S.]</ref> The [[Wind power in the United States|United States]] is an important growth area and latest [[American Wind Energy Association]] figures show that installed U.S. wind power capacity has reached 18,302 MW, which is enough to serve 5 million average households.<ref>[http://www.awea.org/projects/ AWEA First Quarter 2008 Market Report]</ref><ref>[http://www.awea.org/newsroom/releases/AWEA_Market_Release_Q108.html U.S. Wind Industry Installs 1,400 MW in First Quarter]</ref> [[Horse Hollow Wind Energy Center]], in [[Texas]], is the world's largest [[wind farm]] at 735.5 MW capacity. It consists of 291 [[GE Energy]] 1.5 MW [[wind turbines]] and 130 [[Siemens AG|Siemens]] 2.3 MW wind turbines.<ref name="fplen">{{cite web | last =FPL Energy, LLC | title =Horse Hollow Wind Energy Center now largest wind farm in the world | publisher =FPL Energy, LLC | date =2007-09-07 | url =http://www.fplenergy.com/news/contents/090706.shtml | accessdate =2007-06-14 }}</ref> In the UK, a licence to build the world's largest offshore windfarm, in the Thames estuary, has been granted. The [[London Array]] windfarm, 20 km off Kent and Essex, should eventually consist of 341 turbines, occupying an area of 230 km². This is a £1.5 billion, 1,000 megawatt project, which will power one-third of London homes. The windfarm will produce an amount of energy that, if generated by conventional means, would result in 1.9 million tonnes of carbon dioxide emissions every year. It could also make up to 10% of the Government's 2010 renewables target.<ref> [http://www.telegraph.co.uk/news/main.jhtml;jsessionid=BMRYVNCKZPTCNQFIQMGSFFOAVCBQWIV0?xml=/news/2006/12/19/nwind19.xml Windfarms to power a third of London homes].</ref> A proposed 4,000 MW facility, called the [[Pampa Wind Project]], is to be located near Pampa, Texas. === New generation of solar thermal plants === [[Image:PS10 solar power tower 2.jpg|350px|right|thumb|The 11 megawatt [[PS10 solar power tower]] in Spain produces electricity from the sun using 624 large movable mirrors called heliostats.]] [[Image:Solarplant-050406-04.jpg|350px|thumb|right|Aerial view of one of the [[SEGS]] plants.]] {{main|List of solar thermal power stations}} Since 2004 there has been renewed interest in solar thermal power stations and two plants were completed during 2006/2007: the 64 MW [[Nevada Solar One]] and the 11 MW [[PS10 solar power tower]] in Spain. Three 50 MW trough plants were under construction in Spain at the end of 2007 with 10 additional 50 MW plants planned. In the United States, utilities in California and Florida have announced plans (or contracted for) at least eight new projects totaling more than 2,000 MW.<ref name=global>[[REN21]] (2008). [http://www.worldwatch.org/files/pdf/renewables2007.pdf Renewables 2007 Global Status Report (PDF)] p. 12.</ref> In developing countries, three [[World Bank]] projects for integrated CSP/combined-cycle gas-turbine power plants in Egypt, Mexico, and Morocco were approved during 2006/2007.<ref name=global/> There are several [[solar power plants in the Mojave Desert|solar thermal power plants in the Mojave Desert]] which supply power to the [[electricity grid]]. [[Solar Energy Generating Systems]] (SEGS) is the name given to nine [[solar power plants]] in the [[Mojave Desert]] which were built in the 1980s. These plants have a combined capacity of 354 [[megawatts]] (MW) making them the largest [[solar power]] installation in the world. === World's largest photovoltaic power plants === {{Main|Photovoltaic power stations}} The [[Moura photovoltaic power station]], located in the municipality of Moura, [[Portugal]], is presently under construction and will have an installed capacity of 62 MWp. The first stage of construction should be finished in 2008 and the second and final stage is scheduled for 2010, making it one of the largest photovoltaic projects ever constructed.<ref name=moura>[http://www.guardian.co.uk/renewable/Story/0,2763,1570304,00.html Portugal plans biggest solar station]</ref> Construction of a 40 MW solar generation power plant is underway in the Saxon region of Germany. The [[Waldpolenz Solar Park]] will consist of some 550,000 thin-film solar modules. The direct current produced in the modules will be converted into alternating current and fed completely into the power grid. Completion of the project is expected in 2009.<ref> [http://www.renewableenergyaccess.com/rea/news/story?id=47541 Phase One of 40 MW German Solar Park Begun].</ref> Three large photovoltaic power plants have recently been completed in Spain: the Parque Solar Hoya de Los Vincentes (23 MW), the Solarpark Calveron (21 MW), and the Planta Solar La Magascona (20 MW).<ref>Greenpeace Energy (2008). [http://www.pvresources.com/en/top50pv.php World's largest photovoltaic power plants]</ref> [[Image:SolarPowerPlantSerpa.jpg|300px|right|thumb|11 MW solar power plant near Serpa, Portugal. {{coord|38|1|51|N|7|37|22|W|}}]] Another [[photovoltaic]] power project has been completed in Portugal. The [[Serpa solar power plant]] is located at one of Europe's sunniest areas.<ref>[http://www.stuff.co.nz/stuff/4009836a6026.html Major solar power plant opens in Portugal]</ref> The 11 megawatt plant covers {{convert|150|acre|km2}} and comprises 52,000 PV panels. The panels are raised 2 metres off the ground and the area will remain productive grazing land. The project will provide enough energy for 8,000 homes and will save an estimated 30,000 tonnes of carbon dioxide emissions per year.<ref> [http://news.bbc.co.uk/2/hi/europe/5056012.stm Portugal starts huge solar plant]</ref><ref> [http://www.geenergyfinancialservices.com/press_room/press_releases/prs_2006_0427.pdf World's largest solar photovoltaic power plant to be built] (PDF).</ref> A $420 million large-scale [[Solar power station in Victoria]] is to be the biggest and most efficient solar photovoltaic power station in the world. Australian company Solar Systems will demonstrate its unique design incorporating space technology in a 154MW solar power station connected to the national grid. The power station will have the capability to concentrate the sun by 500 times onto the solar cells for ultra high power output. The Victorian power station will generate clean electricity directly from the sun to meet the annual needs of over 45,000 homes with zero greenhouse gas emissions.<ref> [http://www.solarsystems.com.au/154MWVictorianProject.html Solar Systems — 154MW Victorian Project].</ref> However, when it comes to renewable energy systems and PV, it is not just large systems that matter. [[Building-integrated photovoltaic]]s or "onsite" PV systems have the advantage of being matched to end use energy needs in terms of scale. So the energy is supplied close to where it is needed.<ref> [http://jcwinnie.biz/wordpress/?p=1724 Solar Integrated in New Jersey].</ref> === The California Solar Initiative === As part of Governor Arnold Schwarzenegger's Million Solar Roofs Program, California has set a goal to create 3,000 megawatts of new, solar-produced electricity by 2017 — moving the state toward a cleaner energy future and helping lower the cost of solar systems for consumers. This is a comprehensive $2.8 billion program.<ref name="CAsolar"> [http://www.cpuc.ca.gov/static/energy/solar/ The California Solar Initiative].</ref> The [[California Solar Initiative]] offers cash incentives on solar PV systems of up to $2.50 a watt. These incentives, combined with federal tax incentives, can cover up to 50% of the total cost of a solar panel system.<ref name="CAsolar"/> There are many financial incentives to support the use of renewable energy in other US states.<ref> [http://www.dsireusa.org/library/includes/incentivenew.cfm?&CurrentPageID=3&EE=0&RE=1 Financial Incentives in the USA].</ref> === Use of ethanol for transportation === {{main|Ethanol fuel}} Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane, and ethanol now provides 18 percent of the country's automotive fuel. As a partial result, Brazil, which years ago had to import a large share of the petroleum needed for domestic consumption, recently reached complete self-sufficiency in oil.<ref> [http://www.renewableenergyaccess.com/rea/news/story?id=44896 America and Brazil Intersect on Ethanol].</ref> Most cars on the road today in the U.S. can run on blends of up to 10% ethanol, and motor vehicle manufacturers already produce vehicles designed to run on much higher ethanol blends. [[Ford Motor Company|Ford]], [[DaimlerChrysler]], and [[General Motors Corporation|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 six million E85-compatible vehicles on U.S. roads.<ref name="Worldwatch"/> 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 gallons of biofuels to be used annually by 2012, will also help to expand the market.<ref name="Worldwatch"/> === Wave farms expansion === {{main|Wave farm}} [[Portugal]] now has the world's first commercial [[wave farm]], the ''Aguçadora Wave Park'', established in 2006. The farm will initially use three [[Pelamis Wave Energy Converter|Pelamis P-750]] machines generating 2.25 MW.<ref> [http://news.bbc.co.uk/1/hi/scotland/4805076.stm Sea machine makes waves in Europe]</ref><ref> [http://news.bbc.co.uk/1/hi/scotland/4563077.stm Wave energy contract goes abroad]</ref> Initial costs are put at [[euro|€]]8.5 million. Subject to successful operation, a further €70 million is likely to be invested before 2009 on a further 28 machines to generate 525 MW.<ref> [http://jn.sapo.pt/2006/05/12/economia_e_trabalho/primeiro_parque_mundial_ondas_povoa_.html Primeiro parque mundial de ondas na Póvoa de Varzim].</ref> Funding for a wave farm in [[Scotland]] was announced in February, 2007 by the [[Scottish Government]], at a cost of over 4 million [[pound sterling|pounds]], as part of a £13 million funding packages for [[Renewable energy in Scotland#Wave power|ocean power in Scotland]]. The farm will be the world's largest with a capacity of 3MW generated by four Pelamis machines.<ref> [http://news.bbc.co.uk/2/hi/uk_news/scotland/6377423.stm Orkney to get 'biggest' wave farm].</ref> === Geothermal energy prospects === [[Image:West Ford Flat Geothermal Cooling Tower.JPG|right|thumb|The West Ford Flat power plant is one of 21 power plants at The Geysers]] [[The Geysers]], is a [[geothermal power]] field located 72 miles (116 km) north of [[San Francisco]], [[California]]. It is the largest geothermal development in the world outputting over 750 MW.<ref name = "calpine"> {{cite web | title = Calpine Corporation - The Geysers | url = http://www.geysers.com | format = http | accessdate = 2007-05-16 }}</ref> By the end of 2005 worldwide use of [[geothermal energy]] for electricity had reached 9.3&nbsp;[[watt|GW]]s, with an additional 28&nbsp;GW used directly for heating.<ref name="REN21-2006"/> If heat recovered by [[Geothermal exchange heat pump|ground source heat pumps]] is included, the non-electric use of geothermal energy is estimated at more than 100 GWt (gigawatts of thermal power) and is used commercially in over 70 countries.(<ref name="REN21-2006"> [http://www.ren21.net/globalstatusreport/download/RE_GSR_2006_Update.pdf Renewables 2006 Update] (PDF).</ref> sec 1.2) During 2005 contracts were placed for an additional 0.5&nbsp;GW of capacity in the United States, while there were also plants under construction in 11 other countries.<ref name="REN21-2006"/> ===Developing country markets=== {{Main|Renewable energy in developing countries}} 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.<ref name=aus>[http://www.ausaid.gov.au/publications/pdf/renewable_energy.pdf Power for the People] p. 3.</ref> 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.<ref>[http://www.worldwatch.org/system/files/ren21-1.pdf Energy for Development: The Potential Role of Renewable Energy in Meeting the Millennium Development Goals] pp. 7-9.</ref> Kenya is the world leader in the number of solar power systems installed per capita (but not the number of watts added). More than 30,000 very small solar panels, each producing 12 to 30 watts, are sold in Kenya annually. For an investment of as little as $100 for the panel and wiring, the PV system can be used to charge a car battery, which can then provide power to run a fluorescent lamp or a small television for a few hours a day. More Kenyans adopt solar power every year than make connections to the country’s electric grid.<ref>[http://rael.berkeley.edu/files/2006/Kammen-SciAm-Renewables-9-06.pdf The Rise of Renewable Energy]</ref> ===Future potential=== Present renewable energy sources supply about 18% of current energy use and there is much potential that could be exploited in the future. As the table below illustrates, the technical potential of renewable energy sources is more than 18 times current global [[primary energy]] use and furthermore several times higher than projected energy use in 2100. [[Image:Available Energy-3.png|thumb|right|260px|Available renewable energy. The volume of the cubes represent the amount of available geothermal, wind and solar energy in [[Watt#Terawatt|TW]], although only a small portion is recoverable. The small red cube shows the proportional global energy consumption.<ref>[http://gcep.stanford.edu/research/exergycharts.html [[Exergy]] (the useful portion of energy) flow charts]</ref>]] {| class="wikitable" | colspan=4 align="center" | '''The Renewable Energy Resource Base ([[Exajoule]]s per year)''' |- ! ! Current use (2001) ! Technical potential ! Theoretical <br> potential |- valign="bottom" ! Hydropower |align="center"| 9&nbsp; &nbsp; |align="center"| &nbsp; &nbsp;&nbsp; &nbsp; 50 |align="right" | 147 &nbsp; &nbsp; &nbsp; |- ! Biomass energy |align="center"| 50&nbsp; &nbsp; &nbsp; |align="center"| &nbsp;&nbsp; >276 |align="right" | 2,900 &nbsp; &nbsp; &nbsp; |- ! Wind energy |align="center"| &nbsp; 0.12 |align="center"| &nbsp; &nbsp;&nbsp; 640 |align="right" | 6,000 &nbsp; &nbsp; &nbsp; |- ! Solar energy |align="center"| 0.1 |align="center"| >1,575 |align="right" | 3,900,000 &nbsp; &nbsp; &nbsp; |- ! Geothermal energy |align="center"| 0.6 |align="center"| &nbsp; -- |align="right" | -- &nbsp; &nbsp; &nbsp; |- ! Ocean energy |align="center"| not estimated |align="center"| not estimated |align="right" | 7,400 &nbsp; &nbsp; &nbsp; |- ! Total |align="center"| 60&nbsp; &nbsp; &nbsp; |align="center"| >1,800 |align="right" | >4,000,000 &nbsp; &nbsp; &nbsp; |- | colspan=4 | Current use is in [[primary energy]] equivalent.<br>For comparison, the global primary energy use was 402 EJ per year in 2001.<br>Source: World Energy Assessment 2001<ref name=WEA2001> World Energy Assessment 2001, Chapter 5: Energy Resources (table 5.26), coordinating lead author Hans-Holger Rogner. Available for download at its [http://www.undp.org/energy/activities/wea/drafts-frame.html UNDP site].</ref> |} There are many different ways to assess potentials. The theoretical potential indicates the amount of energy theoretically available for energy purposes, such as, in the case of [[solar energy]], the amount of incoming radiation at the earth's surface. The technical potential is a more practical estimate of how much could be put to human use by considering [[energy conversion efficiency|conversion efficiencies]] of the available technology and available land area. To give an idea of the constraints, the estimate for solar energy assumes that 1% of the world's unused land surface is used for solar power. The technical potentials generally do not include economic or other environmental constraints, and the potentials that could be realized at an economically competitive level under current conditions and in a short time-frame is lower still. [[Sustainable development]] and [[global warming]] groups propose a 100% Renewable Energy Source Supply, without [[fossil fuel]]s and [[nuclear power]].<ref>http://www.islandsonline.org/res.htm</ref> Scientists from the [[University of Kassel]] have been busy proving that Germany can power itself entirely by renewable energy.<ref> http://www.blog.thesietch.org/2007/12/30/germany-going-100-renewable-or-yet-another-reason-why-america-is-falling-behind/</ref> ===Trends favoring renewables=== The renewable market will boom when cost efficiency attains parity with other competing energy sources. The following trends are a few examples by which the renewables market is being helped to attain critical mass so that it becomes competitive enough vs fossil fuels: Other than market forces, renewable industry often needs government sponsorship to help generate enough momentum in the market. Many countries and states have implemented incentives — like government tax subsidies, partial copayment schemes and various rebates over purchase of renewables — to encourage consumers to shift to renewable energy sources.<ref> [http://www.renewableenergyaccess.com/rea/news/story?id=45831 Solar incentives example — California]</ref> Government grants fund for research in renewable technology to make the production cheaper and generation more efficient.<ref> [http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2005/07/11/BUG7IDL1AF1.DTL Solar nanotech research].</ref> Development of [[loan]] programs that stimulate renewable favoring market forces with attractive return rates, buffer initial deployment costs and entice consumers to consider and purchase renewable technology. A famous example is the [[Indian Solar Loan Programme|solar loan program]] sponsored by UNEP helping 100,000 people finance solar power systems in [[Solar power in India|India]].<ref> [http://www.unep.org/Documents.Multilingual/Default.asp?DocumentID=504&ArticleID=5562&l=en Solar loan program in India].</ref> Success in [[Solar power in India|India's]] solar program has led to similar projects in other parts of developing world like [[Tunisia]], [[Morocco]], [[Indonesia]] and [[Mexico]]. Imposition of fossil fuel consumption and [[carbon tax]]es, and channel the revenue earned towards renewable energy development.<ref> [http://online.wsj.com/public/article/SB117086898234001121.html Is It Time for a New Tax on Energy?]</ref> Also [[oil peak]] and [[world petroleum crisis]] and inflation are helping to promote renewables. Many [[think-tank]]s are warning that the world needs an urgency driven concerted effort to create a competitive renewable energy infrastructure and market. The developed world can make more research investments to find better cost efficient technologies, and manufacturing could be transferred to developing countries in order to use low labor costs. The renewable energy market could increase fast enough to replace and initiate the decline of fossil fuel dominance and the world could then avert the looming climate and peak oil crises.<ref> [http://www.nytimes.com/2007/04/15/magazine/15green.t.html?ex=1334289600&en=77253fdf8f321a95&ei=5088&partner=rssnyt&emc=rss Power of green].</ref> Most importantly, renewables is gaining credence among private investors as having the potential to grow into the next big industry. Many companies and venture capitalists are investing in photovoltaic development and manufacturing. This trend is particularly visible in [[Silicon valley]], [[California]], [[Europe]], [[Japan]].<ref> [http://www.msnbc.msn.com/id/14911532/ Solar power shines bright in Silicon Valley]. </ref><ref> [http://abcnews.go.com/WNT/Technology/story?id=3018981&page=1 Betting on Solar Power]. </ref><ref> [http://www.nanosolar.com/cache/merc081504.htm World events spark interest in solar cell energy start-ups].</ref> == Constraints and opportunities == Critics suggest that some renewable energy applications may create pollution, be dangerous, take up large amounts of land, or be incapable of generating a large net amount of energy. Proponents advocate the use of "appropriate renewables", also known as [[soft energy technologies]], as these have many advantages. === Availability and reliability=== {{See|Energy security and renewable technology}} [[Image:Available Energy-3.png|thumb|right|260px|'''Available renewable energy.''' The volume of the cubes represent the amount of available geothermal, wind and solar energy in [[Watt#Terawatt|TW]], although only a small portion is recoverable. The small red cube shows the proportional global energy consumption.<ref>[http://gcep.stanford.edu/research/exergycharts.html [[Exergy]] (the useful portion of energy) flow charts]</ref>]] There is no shortage of solar-derived energy on Earth. Indeed the storages and flows of energy on the planet are very large relative to human needs. * The amount of solar energy intercepted by the Earth every minute is greater than the amount of energy the world uses in fossil fuels each year. * Tropical [[ocean]]s absorb 560 trillion [[gigajoule]]s (GJ) of solar energy each year, equivalent to 1,600 times the world’s annual energy use. * The energy in the [[wind]]s that blow across the United States each year could produce more than 16 billion GJ of [[electricity]]—more than one and one-half times the electricity consumed in the United States in 2000. * Annual [[photosynthesis]] by the vegetation in the United States is 50 billion GJ, equivalent to nearly 60% of the nation’s annual fossil fuel use. A criticism of some renewable sources is their [[Intermittent Power Sources|variable]] nature. But renewable power sources can actually be integrated into the grid system quite well, as [[Amory Lovins]] explains: <blockquote> Variable but forecastable renewables (wind and solar cells) are very reliable when integrated with each other, existing supplies and demand. For example, three German states were more than 30 percent wind-powered in 2007—and more than 100 percent in some months. Mostly renewable power generally needs less backup than utilities already bought to combat big coal and nuclear plants' intermittence.<ref name=lov>[http://www.newsweek.com/id/137501 Missing the Market Meltdown]</ref> </blockquote> The challenge of variable power supply may be readily alleviated by energy storage. Available storage options include [[hydroelectricity|pumped-storage hydro system]]s, batteries, hydrogen [[fuel cell]]s, and thermal mass. Initial investments in such energy storage systems may be high, although the costs can be recovered over the life of the system. Lovins goes on to say that the unreliability of renewable energy is a myth, while the unreliability of [[nuclear energy]] is real. Of all U.S. nuclear plants built, 21 percent were abandoned and 27 percent have failed at least once. Successful reactors must close for refueling every 17 months for 39 days. And when shut in response to grid failure, they can't quickly restart. This is simply not the case for wind farms, for example.<ref name=lov/> Wave energy and some other renewables are continuously available. A wave energy scheme installed in Australia generates electricity with an 80% availability factor. === Aesthetics=== Both solar and wind generating stations have been criticized from an aesthetic point of view.<ref> {{cite web |url=http://www.tvenergy.org/sources-windturbine.htm |title=Small Scale Wind Energy Factsheet |accessdate=2007-09-19 |date=Last Updated: 14-02-2007 |publisher=Thames Valley Energy}} </ref> However, methods and opportunities exist to deploy these renewable technologies efficiently and unobtrusively: fixed solar collectors can double as noise barriers along highways, and extensive roadway, parking lot, and roof-top area is currently available; [[photovoltaic cell|amorphous photovoltaic cells]] can also be used to tint windows and produce energy.<ref> {{cite web |url=http://energypriorities.com/entries/2006/05/xsunx_power_glass_bipv.php |title=Thin Film Could Soon Make Solar Glass and Facades a Practical Power Source |accessdate=2007-09-19 |author=Denis Du Bois |date=May 22, 2006 |publisher=Energy Priorities}} </ref> Advocates of renewable energy also argue that current infrastructure is less aethetically pleasing than alternatives, but sited further from the view of most critics.<ref> {{cite web |url=http://news.bbc.co.uk/1/hi/talking_point/3266673.stm |title=What is the worst eyesore in the UK? |accessdate=2007-09-19 |quote=I really wish people wouldn't criticise wind farms. I would much rather have 12 hills full of wind turbines than 1 single nuclear power station. |publisher=BBC News}} </ref> === Environmental and social considerations === While most renewable energy sources do not produce pollution directly, the materials, industrial processes, and construction equipment used to create them may generate waste and pollution. Some renewable energy systems actually create environmental problems. For instance, older wind turbines can be hazardous to flying birds.<ref> {{cite web |url=http://www.rspb.org.uk/ourwork/policy/windfarms/index.asp |title=Policy: Wind farms |accessdate=2007-09-19 |date=Last modified: 14 September 2005 |publisher=Royal Society for the Protection of Birds (RSPB)}}</ref> ==== Land area required ==== Another environmental issue, particularly with biomass and biofuels, is the large amount of land required to harvest energy, which otherwise could be used for other purposes or left as undeveloped land. However, it should be pointed out that these fuels may reduce the need for harvesting non-renewable energy sources, such as vast strip-mined areas and slag mountains for coal, safety zones around nuclear plants, and hundreds of square miles being strip-mined for oil sands. These responses, however, do not account for the extremely high [[biodiversity]] and [[endemism]] of land used for ethanol crops, particularly sugar cane. In the U.S., crops grown for biofuels are the most land- and water-intensive of the renewable energy sources. In 2005, about 12% of the nation’s corn crop (covering 11 million acres (45,000 km²) of farmland) was used to produce four billion gallons of ethanol—which equates to about 2% of annual U.S. gasoline consumption. For biofuels to make a much larger contribution to the energy economy, the industry will have to accelerate the development of new feedstocks, agricultural practices, and technologies that are more land and water efficient. Already, the efficiency of biofuels production has increased significantly<ref name="Worldwatch"/> and there are new methods to boost biofuel production.<ref> [http://environment.newscientist.com/article.ns?id=dn11364&print=true Hydrogen injection could boost biofuel production].</ref> ====Hydroelectric dams==== The major advantage of hydroelectric systems is the elimination of the cost of fuel. Other advantages include longer life than fuel-fired generation, low operating costs, and the provision of facilities for water sports. Operation of pumped-storage plants improves the daily load factor of the generation system. Overall, hydroelectric power can be far less expensive than electricity generated from fossil fuels or nuclear energy, and areas with abundant hydroelectric power attract industry. However, there are several major disadvantages of hydroelectric systems. These include: dislocation of people living where the reservoirs are planned, release of significant amounts of carbon dioxide at construction and flooding of the reservoir, disruption of aquatic ecosystems and birdlife, adverse impacts on the river environment, potential risks of sabotage and terrorism, and in rare cases catastrophic failure of the dam wall. (See [[Hydroelectricity]] article for details.) Hydroelectric power is now more difficult to site in developed nations because most major sites within these nations are either already being exploited or may be unavailable for other reasons such as environmental considerations. ====Wind farms==== [[Image:WEAs in Neuenkirchen.JPG|right|thumb|[[Wind power]] is one of the most environmentally friendly sources of renewable energy]] A [[wind farm]], when installed on agricultural land, has one of the lowest environmental impacts of all energy sources:<ref name="AU"> [http://www.sustainabilitycentre.com.au/WindPowersStrength.pdf Why Australia needs wind power]</ref> *It occupies less land area per kilowatt-hour (kWh) of electricity generated than any other energy conversion system, apart from rooftop solar energy, and is compatible with grazing and crops. *It generates the energy used in its construction in just 3 months of operation, yet its operational lifetime is 20–25 years. *Greenhouse gas emissions and air pollution produced by its construction are tiny and declining. There are no emissions or pollution produced by its operation. *In substituting for base-load coal power, wind power produces a net decrease in greenhouse gas emissions and air pollution, and a net increase in biodiversity. *Modern wind turbines are almost silent and rotate so slowly (in terms of revolutions per minute) that they are rarely a hazard to birds.<ref name="AU"/> Studies of birds and offshore wind farms in Europe have found that there are very few bird collisions.<ref> newscientist.com June 2005 [http://www.newscientist.com/channel/life/mg18625045.500 Wind turbines a breeze for migrating birds]</ref> Several offshore wind sites in Europe have been in areas heavily used by seabirds. Improvements in wind turbine design, including a much slower rate of rotation of the blades and a smooth tower base instead of perchable lattice towers, have helped reduce bird mortality at wind farms around the world. However older smaller wind turbines may be hazardous to flying birds.<ref> {{cite web |url=http://www.countryguardian.net/Chapman.htm |title=Renewable energy industry environmental impacts |accessdate=2007-09-19 |author=Andrew Chapman |date=2003-11-15 |publisher=Country Guardian |quote=Evaluations of the bird kills at Altamont suggested that the small, 18-metre diameter rotor, turbines rotating a high speed, 60 revolutions per minute, were a major contributor.}} </ref> Birds are severely impacted by fossil fuel energy; examples include birds dying from exposure to oil spills, habitat loss from acid rain and mountaintop removal coal mining, and mercury poisoning.<ref> [http://www.capewind.org/FAQ-Category8-Cape+Wind+and+the+Environment-Parent0-myfaq-yes.htm#43 What about offshore wind farms and birds?]</ref> === Longevity issues=== Though a source of renewable energy may last for billions of years, renewable energy infrastructure, like hydroelectric dams, will not last forever, and must be removed and replaced at some point. Events like the shifting of riverbeds, or changing weather patterns could potentially alter or even halt the function of hydroelectric dams, lowering the amount of time they are available to generate electricity. Although geothermal sites are capable of providing heat for many decades, eventually specific locations may cool down. It is likely that in these locations, the system was designed too large for the site, since there is only so much energy that can be stored and replenished in a given volume of earth. Some interpret this as meaning a specific geothermal location can undergo depletion. === Biofuels production=== {{See also|Ethanol fuel energy balance}} All biomass needs to go through some of these steps: it needs to be grown, collected, dried, fermented and burned. All of these steps require resources and an infrastructure. Some studies contend that ethanol is "energy negative", meaning that it takes more energy to produce than is contained in the final product.<ref> [http://petroleum.berkeley.edu/papers/Biofuels/NRRethanol.2005.pdf Ethanol Production Using Corn, Switchgrass, and Wood; Biodiesel Production Using Soybean and Sunflower] (PDF).</ref> However, a large number of recent studies, including a 2006 article<ref> [http://rael.berkeley.edu/ebamm/FarrellEthanolScience012706.pdf Ethanol Can Contribute to Energy and Environmental Goals] (PDF).</ref> in the journal ''Science'' offer the opinion that fuels like ethanol are energy positive. Furthermore, fossil fuels also require significant energy inputs which have seldom been accounted for in the past. Additionally, ethanol is not the only product created during production, and the energy content of the by-products must also be considered. Corn is typically 66% starch and the remaining 33% is not fermented. This unfermented component is called distillers grain, which is high in fats and proteins, and makes good animal feed.<ref> [http://www.ddgs.umn.edu/more.htm University of Minnesota]</ref> In Brazil, where sugar cane is used, the yield is higher, and conversion to ethanol is somewhat more energy efficient than corn. Recent developments with [[cellulosic ethanol]] production may improve yields even further.<ref> [http://news.bbc.co.uk/2/hi/science/nature/5353118.stm Biofuels look to the next generation].</ref> According to the [[International Energy Agency]], new biofuels technologies being developed today, notably cellulosic ethanol, could allow biofuels to play a much bigger role in the future than previously thought.<ref> [http://www.worldenergyoutlook.org/summaries2006/English.pdf International Energy Agency, World Energy Outlook 2006] (PDF), page 8.</ref> Cellulosic ethanol can be made from plant matter composed primarily of inedible cellulose fibers that form the stems and branches of most plants. Crop residues (such as corn stalks, wheat straw and rice straw), wood waste, and municipal solid waste are potential sources of cellulosic biomass. Dedicated energy crops, such as switchgrass, are also promising cellulose sources that can be sustainably produced in many regions of the United States.<ref> [http://bio.org/ind/biofuel/CellulosicEthanolIssueBrief.pdf Industrial Biotechnology Is Revolutionizing the Production of Ethanol Transportation Fuel] (PDF), pages 3–4.</ref> The ethanol and biodiesel production industries also create jobs in plant construction, operations, and maintenance, mostly in rural communities. According to the Renewable Fuels Association, the ethanol industry created almost 154,000 U.S. jobs in 2005 alone, boosting household income by $5.7 billion. It also contributed about $3.5 billion in tax revenues at the local, state, and federal levels.<ref name="Worldwatch"/> === Diversification === {{globalize/USA}} The U.S. electric power industry now relies on large, central power stations, including coal, natural gas, nuclear, and hydropower plants that together generate more than 95% of the nation’s electricity. Over the next few decades uses of renewable energy could help to diversify the nation’s bulk power supply. Already, appropriate renewable resources (which excludes large hydropower) produce 12% of northern California’s electricity.<ref name="Worldwatch">{{cite web | title = American Energy: The Renewable Path to Energy Security | publisher = Worldwatch Institute |date=September 2006 | url = http://images1.americanprogress.org/il80web20037/americanenergynow/AmericanEnergy.pdf | format = [[PDF]] | accessdate = 2007-03-11}}</ref> Although most of today’s electricity comes from large, central-station power plants, new technologies offer a range of options for generating electricity nearer to where it is needed, saving on the cost of transmitting and distributing power and improving the overall efficiency and reliability of the system.<ref name="Worldwatch"/> Improving [[efficient energy use|energy efficiency]] represents the most immediate and often the most cost-effective way to reduce oil dependence, improve energy security, and reduce the health and environmental impact of the energy system. By reducing the total energy requirements of the economy, improved energy efficiency could make increased reliance on renewable energy sources more practical and affordable.<ref name="Worldwatch"/> == Other issues == === Sustainability === Renewable energy sources are generally sustainable in the sense that they cannot "run out" as well as in the sense that their environmental and social impacts are generally more benign than those of fossil. However, both biomass and geothermal energy require wise management if they are to be used in a sustainable manner. For all of the other renewables, almost any realistic rate of use would be unlikely to approach their rate of replenishment by nature.<ref>[http://openlearn.open.ac.uk/mod/resource/view.php?id=209151 Sustainability of renewable energy sources]</ref> === Transmission === If renewable and [[distributed generation]] were to become widespread, [[electric power transmission]] and [[electricity distribution]] systems might no longer be the main distributors of electrical energy but would operate to balance the electricity needs of local communities. Those with surplus energy would sell to areas needing "top ups". That is, network operation would require a shift from 'passive management' — where generators are hooked up and the system is operated to get electricity 'downstream' to the consumer — to 'active management', wherein generators are spread across a network and inputs and outputs need to be constantly monitored to ensure proper balancing occurs within the system. Some governments and regulators are moving to address this, though much remains to be done. One potential solution is the increased use of active management of electricity transmission and distribution networks. This will require significant changes in the way that such networks are operated. However, on a smaller scale, use of renewable energy produced on site reduces burdens on electricity distribution systems. Current systems, while rarely economically efficient, have shown that an average household with an appropriately-sized solar panel array and energy storage system needs electricity from outside sources for only a few hours per week. By matching electricity supply to end-use needs, advocates of renewable energy and the [[soft energy path]] believe electricity systems will become smaller and easier to manage, rather than the opposite (see [[Soft energy technology]]). === Market development of renewable heat energy === [[Renewable heat]] is the generation of heat from renewable sources. Much current discussion on renewable energy focuses on the generation of electrical energy, despite the fact that many colder countries consume more energy for heating than as electricity. In 2005 the United Kingdom consumed 354 TWh<ref> Department of Trade and Industry report [http://www.berr.gov.uk/files/file39881.pdf UK Energy in Brief July 2007, Page 25] (URL accessed May, 2008)</ref> of electric power, but had a heat requirement of 907 TWh, the majority of which (81%) was met using gas. The residential sector alone consumed a massive 550 TWh of energy for heating, mainly in the form of gas. Almost half of the final energy consumed in the UK (49%) was in the form of heat.<ref>UK Government Call for Evidence on Heat, Office of Climate Change, Jan 2008 [http://www.berr.gov.uk/files/file43609.pdf 'Heat Call for Evidence', Paragraphs 11 and 12] (URL accessed May, 2008)</ref> Renewable electric power is becoming cheap and convenient enough to place it, in many cases, within reach of the average consumer. By contrast, the market for renewable heat is mostly inaccessible to domestic consumers due to inconvenience of supply, and high capital costs. Heating accounts for a large proportion of energy consumption, however a universally accessible market for renewable heat is yet to emerge. Solutions such as [[geothermal heat pump]]s may be more widely applicable, but may not be economical in all cases. Also see [[renewable energy development]]. === Claims that nuclear power is a renewable energy source === {{main|Energy development#Nuclear energy|Nuclear power}} In 1983, physicist [[Bernard Cohen]] proposed that uranium is effectively inexhaustible, and could therefore be considered a renewable source of energy.<ref name="cohen83">{{Cite journal | volume = 51 | issue = 1 | pages = 75–76 | last = Cohen | first = Bernard L. | title = Breeder reactors: A renewable energy source | journal = American Journal of Physics | accessdate = 2007-08-03 | date = 1983-01 |format = [[PDF]] | url = http://sustainablenuclear.org/PADs/pad11983cohen.pdf | doi = 10.1119/1.13440 }}</ref><ref name="stanford-cohen">{{Cite web | url = http://www-formal.stanford.edu/jmc/progress/cohen.html | title = Facts from Cohen and others | accessdate = 2007-08-03 | date = 1996-02-12 | publisher = Stanford | last = McCarthy | first = John | work = Progress and its Sustainability}}</ref> He claims that [[breeder reactor|fast breeder reactors]], fueled by naturally-replenished uranium extracted from seawater, could supply energy at least as long as the sun's expected remaining lifespan of five billion years.<ref name="cohen83" /> {{quote|We thus conclude that all the world’s energy requirements for the remaining 5×10<sup>9</sup> yr of existence of life on Earth could be provided by breeder reactors without the cost of electricity rising by as much as 1% due to fuel costs. This is consistent with the definition of a “renewable” energy source in the sense in which that term is generally used.}} Nuclear energy has also been referred to as "renewable" by politicians like [[George W. Bush]]<ref>{{ cite web | title = Bush: U.S. must end dependence on foreign oil | publisher = Associated Press | work = MSNBC |date=September 4, 2006 | url =http://www.msnbc.msn.com/id/14668738/ | accessdate= 2007-03-11}}</ref><ref>{{Cite web | title = DubyaSpeak.com : Repeat Offender (Renewable Nuclear Power) | accessdate = 2007-08-03 | url = http://www.dubyaspeak.com/repeatoffender.phtml?offense=renewable }}</ref><ref>[http://www.nirs.org/nukerelapse/bush/48orgonbushrenewables012605.htm 48 Organizations Refute President Bush's Claim That Nuclear Power is a "Renewable Sourse of Energy"] January 26, 2005</ref> and [[David Sainsbury]].<ref name="minister declares">[http://business.timesonline.co.uk/article/0,,9078-1850323,00.html Minister declares nuclear 'renewable' — UK Times]</ref><ref>{{Cite web | title = UK To Redefine Nuclear Energy As Renewable? | work = WISE/NIRS Nuclear Monitor | accessdate = 2007-08-03 | date = 2005-11-04 | url = http://www10.antenna.nl/wise/index.html?http://www10.antenna.nl/wise/637/5728.php }}</ref> In remarks at the 2007 Florida Summit on Global Climate Change, Florida Governor [[Charlie Crist]] mentioned nuclear as a renewable alongside biofuels, solar, and wind, due to its environmental effects and ability to reduce dependence on foreign oil.<ref>{{Cite web | title = Governor Crist Opens Florida Summit on Global Climate Change | work = flgov.com | accessdate = 2007-08-03 | date = 2007-07-12 | url = http://www.flgov.com/release/9213 }}</ref><ref>{{Cite news | last = Follick | first = Joe | title = Fla. Green May Mean Nuclear Increase | work = The Ledger | accessdate = 2007-08-03 | date = 2007-07-15 | url = http://www.theledger.com/article/20070715/NEWS/707150420/1039 }}</ref><ref>{{Cite news | last = Hiers | first = Fred | title = Utilities' eyes on energy summit | work = Star-Banner | accessdate = 2007-08-03 | date = 2007-07-12 | url = http://www.ocala.com/article/20070712/NEWS/207120356/1001/NEWS01 }}</ref> Inclusion under the "renewable energy" classification could render nuclear power projects eligible for development aid under various jurisdictions. However, no legislative body has yet included nuclear energy under any legal definition of "renewable energy sources" for provision of development support (see: [[Renewable energy development]]). Similarly, [[Statute|statutory]] and scientific definitions of renewable energies usually exclude nuclear energy. In [[England]] and [[Wales]] there is a [[Non-Fossil Fuel Obligation]], which provides support for renewable energy.<ref name="DTI NFFO page">[http://www.dti.gov.uk/energy/energy-sources/renewables/policy/renewables-obligation/the-non-fossil-fuel-obligation/page18369.html DTI Non-Fossil Fuel Obligation]</ref> Nuclear power production was also subsidised by this obligation from 1990 until 2002. Commonly sourced definitions of renewable energy sources similarly treat solar-derived energy sources as effectively inexhaustible, though they usually omit or explicitly exclude nuclear energy sources as examples.<ref>{{cite web |url=http://dictionary.reference.com/browse/renewable |title=Renewable: Definitions from Dictionary.com |publisher=Lexico Publishing Group, LLC |accessdate=2007-08-25 |work=Dictionary.com website}}</ref><ref>{{cite web |url=http://dictionary.reference.com/browse/renewable%20energy |title=Renewable energy: Definitions from Dictionary.com |publisher=Lexico Publishing Group, LLC |accessdate=2007-08-25 |work=Dictionary.com website}}</ref><ref>{{cite web |url=http://dictionary.reference.com/browse/renewable%20resource |title=Renewable resource: Definitions from Dictionary.com |publisher=Lexico Publishing Group, LLC |accessdate=2007-08-25 |work=Dictionary.com website}}</ref><ref>[http://www.eia.doe.gov/basics/renewalt_basics.htmlRenewable and Alternative Fuels Basics 101]</ref> Nuclear fission is generally not regarded as renewable, as indicated by the U.S. DOE on the website "What is Energy?"<ref>{{cite web | last = | first = | authorlink = | coauthors = | title =Renewable and Alternative Fuels Basics 101 | work = | publisher =[[Energy Information Administration]] | date = | url =http://www.eia.doe.gov/basics/renewalt_basics.html | format = | doi = | accessdate = 2007-12-17 }}</ref><ref>{{cite web | last = | first = | authorlink = | coauthors = | title =Renewable Energy Basics | work = | publisher =National Renewable Energy Laboratory | date = | url =http://www.nrel.gov/learning/re_basics.html | format = | doi = | accessdate = 2007-12-17 }}</ref><ref> [http://www.renewableenergyaccess.com/rea/news/story?id=47296 Nuclear Power Is Not A "Renewable Source of Energy"]. Renewable Energy Access. Retrieved on [[2007-12-17]]. </ref><ref> [http://www.eia.doe.gov/kids/energyfacts/sources/whatsenergy.html What is Energy?]</ref> The environmental concerns with nuclear power are that [[peak uranium|uranium is a finite source of energy]], development of new plants cannot happen quickly enough to reduce {{co2}} emissions, nuclear energy is neither efficient nor effective in cutting {{CO2}} emissions, and [[nuclear waste]] is a dangerous environmental hazard.<ref>[http://www10.antenna.nl/wise/481/4777.html Nuclear power no remedy for the greenhouse effect]</ref> ==See also== {|style="width:100%;" |valign=top| * [[List of large wind farms]] * [[List of photovoltaics companies]] * [[List of renewable energy organizations]] * [[List of renewable energy topics by country]] * [[List of countries by electricity production from renewable source]] * [[List of the largest hydroelectric power stations]] * [[List of solar thermal power stations]] * [[List of wind turbine manufacturers]] |valign=top| * [[Clean Technology Fund]] * [[Directive on Electricity Production from Renewable Energy Sources]] * [[Distributed generation]] * [[Efficient energy use]] * ''[[Energy and American Society]]: Thirteen Myths'' [book] * [[Energy conservation]] * [[Emissions & Generation Resource Integrated Database (eGRID)]] * [[Energy security and renewable technology]] |valign=top| * [[Energy: world resources and consumption]] * [[Eugene Green Energy Standard]] * [[Food, Conservation, and Energy Act of 2008]] * [[Greasestock]] * [[Hybrid power source]] * [[Johannesburg Renewable Energy Coalition]] |valign=top| * [[International Renewable Energy Conference]] * [[International Renewable Energy Agency]] * [[International Renewable Energy Alliance]] * [[Mitigation of global warming]] * [[Non-renewable energy]] * [[Passive solar building design]] * [[Photovoltaic power stations]] * [[Renewable energy commercialization]] * [[Renewable energy development]] * [[Renewable energy industry]] * [[Renewable energy policy]] * [[Renewable heat]] * [[RenewableEnergyAccess.com]] * [[Renewable energy development]] * [[Soft energy technologies]] * [[Sustainable energy]] * [[Waste-to-energy]] * [[Zero energy building]] |valign=top| {{Wikinewscat|Energy}} {{Portal|Sustainable development|Sustainable development.svg|break=yes}} {{EnergyPortal}} |} ==References== {{reflist|2}} ==External links== {{Wikinewscat|Renewable energy}} {{wikinews|Oil prices drive new investment in clean technology}} {{Wikinews|EU adopts renewable energy measures}} {{commonscat|Renewable energy}} {{Wiktionary|renewable energy}} * [http://www.sefi.unep.org Renewable energy] ([[UNEP]]). ** [http://sefi.unep.org/english/globaltrends Global Trends In Sustainable Energy Investment] ([[UNEP]]). * [http://www.nrel.gov NREL] - US National Renewable Energy Laboratory * [http://www.eia.doe.gov/fuelrenewable.html Renewable & Alternative Fuels] data from [[Energy Information Administration]] (EIA) * [http://www.wirec2008.gov/wps/portal/wirec2008 Washington International Renewable Energy Conference (WIREC)] * [http://tonto.eia.doe.gov/energy_in_brief/renewable_energy.cfm How Much Renewable Energy Does the United States Use?] * ''[http://arec.oregonstate.edu/jaeger/energy/realizable%20renewable%20energy%20future.pdf A Realizable Renewable Energy Future]'', [[John A. Turner]], [[Science (journal)|Science]], Vol 285, 30 July 1999. * [http://www.worldwatch.org/node/5630 Renewables 2007 Global Status Report] ([[Worldwatch Institute]]). * [http://www.ren21.net/ REN21] * [http://www.washtimes.com/news/2008/jun/16/nj-weighs-bill-encouraging-alternative-farm-ene-1/ Alternative farm energy] ([[The Washington Times]]). {{environmental technology}} {{Global Warming}} [[Category:Alternative energy]] [[Category:Biomass]] [[Category:Climate change]] [[Category:Renewable energy| ]] [[Category:Renewable energy by country]] [[Category:Sustainable technologies]] {{Link FA|af}} [[af:Hernubare energie]] [[ar:طاقة متجددة]] [[bg:Възобновяема енергия]] [[ca:Energia renovable]] [[cs:Obnovitelný zdroj energie]] [[cy:Egni adnewyddol]] [[da:Vedvarende energi]] [[de:Erneuerbare Energie]] [[el:Ήπιες μορφές ενέργειας]] [[es:Energía renovable]] [[eo:Renoviĝanta energio]] [[fr:Énergie renouvelable]] [[ko:재생가능 에너지]] [[hi:नवीकरणीय ऊर्जा]] [[id:Energi terbaharui]] [[is:Endurnýjanleg orka]] [[it:Energie rinnovabili]] [[he:אנרגיה מתחדשת]] [[lb:Erneierbar Energie]] [[lt:Atsinaujinantys energijos šaltiniai]] [[hu:Megújuló energiaforrás]] [[nl:Duurzame energie]] [[ja:再生可能エネルギー]] [[no:Fornybar energi]] [[pl:Odnawialne źródła energii]] [[pt:Energia renovável]] [[ro:Energie regenerabilă]] [[ru:Возобновляемая энергия]] [[simple:Renewable energy]] [[sl:Obnovljivi viri energije]] [[fi:Uusiutuva energia]] [[sv:Förnybar energi]] [[th:พลังงานทดแทน]] [[vi:Năng lượng tái tạo]] [[uk:Відновлювана енергетика]] [[wa:Todi-poujhåve enerdjeye]] [[bat-smg:Atsėnaujėnontė energėjė]] [[zh:可再生能源]]