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Snippet from Wikipedia: Renewable energy

Renewable energy is energy that is collected from renewable resources, which are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat. Renewable energy often provides energy in four important areas: electricity generation, air and water heating/cooling, transportation, and rural (off-grid) energy services.

Based on REN21's 2017 report, renewables contributed 19.3% to humans' global energy consumption and 24.5% to their generation of electricity in 2015 and 2016, respectively. This energy consumption is divided as 8.9% coming from traditional biomass, 4.2% as heat energy (modern biomass, geothermal and solar heat), 3.9% from hydroelectricity and the remaining 2.2% is electricity from wind, solar, geothermal, and other forms of biomass. Worldwide investments in renewable technologies amounted to more than US$286 billion in 2015. In 2017, worldwide investments in renewable energy amounted to US$279.8 billion with China accounting for US$126.6 billion or 45% of the global investments, the United States for US$40.5 billion and Europe for US$40.9 billion. Globally there are an estimated 7.7 million jobs associated with the renewable energy industries, with solar photovoltaics being the largest renewable employer. Renewable energy systems are rapidly becoming more efficient and cheaper and their share of total energy consumption is increasing. As of 2019, more than two-thirds of worldwide newly installed electricity capacity was renewable. Growth in consumption of coal and oil could end by 2020 due to increased uptake of renewables and natural gas.

At the national level, at least 30 nations around the world already have renewable energy contributing more than 20 percent of energy supply. National renewable energy markets are projected to continue to grow strongly in the coming decade and beyond. Some places and at least two countries, Iceland and Norway, generate all their electricity using renewable energy already, and many other countries have the set a goal to reach 100% renewable energy in the future. At least 47 nations around the world already have over 50 percent of electricity from renewable resources. Renewable energy resources exist over wide geographical areas, in contrast to fossil fuels, which are concentrated in a limited number of countries. Rapid deployment of renewable energy and energy efficiency technologies is resulting in significant energy security, climate change mitigation, and economic benefits. In international public opinion surveys there is strong support for promoting renewable sources such as solar power and wind power.

While many renewable energy projects are large-scale, renewable technologies are also suited to rural and remote areas and developing countries, where energy is often crucial in human development. As most of renewable energy technologies provide electricity, renewable energy deployment is often applied in conjunction with further electrification, which has several benefits: electricity can be converted to heat (where necessary generating higher temperatures than fossil fuels), can be converted into mechanical energy with high efficiency, and is clean at the point of consumption. In addition, electrification with renewable energy is more efficient and therefore leads to significant reductions in primary energy requirements.

, sun, and biomass are three renewable energy sources.]]

, at the entrance to the River Mersey in North West England.]]

is a commercial parabolic trough solar thermal power plant, located in Spain. The Andasol plant uses tanks of molten salt to store solar energy so that it can continue generating electricity even when the sun isn't shining.<ref>

</ref>]]

Renewable energy is generally defined as energy that comes from resources which are naturally replenished on a human timescale such as sunlight, wind, rain, tides, waves and geothermal heat.<ref>

</ref> Renewable energy replaces conventional fuels in four distinct areas: electricity generation, hot water/space heating, motor fuels, and rural (off-grid) energy services.<ref name=ren15>REN21 (2010). Renewables 2010 Global Status Report

p. 15.</ref>

About 16% of global final energy consumption presently comes from renewable resources, with 10% <ref>http://www.iea.org/publications/freepublications/publication/cooking.pdf</ref> of all energy from traditional biomass, mainly used for heating, and 3.4% from hydroelectricity. New renewables (small hydro, modern biomass, wind, solar, geothermal, and biofuels) account for another 3% and are growing rapidly.<ref name=“ria21”>

</ref> At the national level, at least 30 nations around the world already have renewable energy contributing more than 20% of energy supply. National renewable energy markets are projected to continue to grow strongly in the coming decade and beyond.<ref name=“REN21 2013”>

</ref> Wind power, for example, is growing at the rate of 30% annually, with a worldwide installed capacity of 282,482 megawatts (MW) at the end of 2012.

Renewable energy resources exist over wide geographical areas, in contrast to other energy sources, which are concentrated in a limited number of countries. Rapid deployment of renewable energy and energy efficiency is resulting in significant energy security, climate change mitigation, and economic benefits.<ref name=“International Energy Agency 2012”>

</ref> In international public opinion surveys there is strong support for promoting renewable sources such as solar power and wind power.<ref name=“UNEP”>United Nations Environment Programme ''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>

While many renewable energy projects are large-scale, renewable technologies are also suited to rural and remote areas and developing countries, where energy is often crucial in human development.<ref>World Energy Assessment (2001). Renewable energy technologies, p. 221.</ref> 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.<ref name=“renewableenergyworld1”>

</ref>

Overview

accounted for 11%, and hydropower 3%]]

/>

Renewable energy flows involve natural phenomena such as sunlight, wind, tides, plant growth, and geothermal heat, as the International Energy Agency explains:<ref>IEA Renewable Energy Working Party (2002). Renewable Energy… into the mainstream, p. 9.</ref>

Wind power is growing at the rate of 30% annually, with a worldwide installed capacity of 282,482 megawatts (MW) at the end of 2012, and is widely used in Europe, Asia, and the United States. At the end of 2012 the photovoltaic (PV) capacity worldwide was 100,000 MW, and PV power stations are popular in Germany and Italy. 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. 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 sugar cane, and ethanol now provides 18% of the country's automotive fuel. Ethanol fuel is also widely available in the USA.

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.<ref name=“REN21 2011 14”>

</ref> 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.<ref name=“renewableenergyworld1”/>

Renewable energy resources and significant opportunities for energy efficiency exist over wide geographical areas, in contrast to other energy sources, which are concentrated in a limited number of countries. Rapid deployment of renewable energy and energy efficiency, and technological diversification of energy sources, would result in significant energy security and economic benefits.<ref name=“International Energy Agency 2012”/>

Renewable energy replaces conventional fuels in four distinct areas: electricity generation, hot water/space heating, motor fuels, and rural (off-grid) energy services:<ref name=“ren15”/>

  • 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 49% in Denmark. Some countries get most of their power from renewables, including Iceland (100%), Norway (98%), Brazil (86%), Austria (62%), New Zealand (65%), and Sweden (54%).<ref name=ren53>REN21 (2010). Renewables 2010 Global Status Report

    p. 53.</ref>

  • 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.<ref name=ren53/>
  • Transport fuels. Renewable biofuels have contributed to a significant decline in oil consumption in the United States since 2006.<ref name=ren53/> 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.<ref name=ren53/>

At the national level, at least 30 nations around the world already have renewable energy contributing more than 20% of energy supply. National renewable energy markets are projected to continue to grow strongly in the coming decade and beyond, and some 120 countries have various policy targets for longer-term shares of renewable energy, including a 20% target of all electricity generated for the European Union by 2020. Some countries have much higher long-term policy targets of up to 100% renewables. Outside Europe, a diverse group of 20 or more other countries target renewable energy shares in the 2020–2030 time frame that range from 10% to 50%.<ref name=“REN21 2013”/>

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.<ref>

</ref>

Climate change and global warming concerns, coupled with high oil prices, peak oil, and increasing government support, are driving increasing renewable energy legislation, incentives and commercialization.<ref name=“UNEP”/> New government spending, regulation and policies helped the industry weather the global financial crisis better than many other sectors.<ref name=obama>Clean Edge (2009). Clean Energy Trends 2009 pp. 1-4.</ref> 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.<ref name=“Ben Sills”>

</ref>

Renewable energy sources, that derive their energy from the sun, either directly or indirectly, such as Hydro and wind, are expected to be capable of supplying humanity energy for almost another 1 billion years, at which point the predicted increase in heat from the sun is expected to make the surface of the Earth too hot for liquid water to exist.<ref name=Schroeder>

See also

</ref><ref>

</ref>

History

Prior to the development of coal in the mid 19th century, nearly all energy used was renewable. Almost without a doubt the oldest known use of renewable energy, in the form of traditional biomass to fuel fires, dates from 790,000 years ago. Use of biomass for fire did not become commonplace until many hundreds of thousands of years later, sometime between 200,000 and 400,000 years ago.<ref name=Fire>

</ref>

Probably the second oldest usage of renewable energy is harnessing the wind in order to drive ships over water. This practice can be traced back some 7000 years, to ships on the Nile.<ref>

</ref>

Moving into the time of recorded history, the primary sources of traditional renewable energy were human labor, animal power, water power, wind, in grain crushing windmills, and firewood, a traditional biomass. A graph of energy use in the United States up until 1900 shows oil and natural gas with about the same importance in 1900 as wind and solar played in 2010.

By 1873, concerns of running out of coal prompted experiments with using solar energy.<ref>

</ref> Development of solar engines continued until the outbreak of World War I. The importance of solar energy was recognized in a 1911 Scientific American article: “in the far distant future, natural fuels having been exhausted [solar power] will remain as the only means of existence of the human race”.<ref>“Power from Sunshine”: A Business History of Solar Energy May 25, 2012</ref>

The theory of peak oil was published in 1956.<ref>

</ref> In the 1970s environmentalists promoted the development of renewable energy both as a replacement for the eventual depletion of oil, as well as for an escape from dependence on oil, and the first electricity generating wind turbines appeared. Solar had long been used for heating and cooling, but solar panels were too costly to build solar farms until 1980.<ref>

</ref>

Mainstream renewable technologies

<!– This section is for a basic description of the main renewable energy technologies. New and emerging technologies should be added to the section towards the end of the article. Pros and cons of different technologies are discussed in Renewable energy debate. Thanks. –>

Wind power

is a 845 megawatt (MW) wind farm in the U.S. state of Oregon.]]

Airflows can be used to run wind turbines. Modern utility-scale wind turbines range from around 600&nbsp;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 available from the wind is a function of the cube of the wind speed, so as wind speed increases, power output increases dramatically up to the maximum output for the particular turbine.<ref name=“EWEA”>

</ref> 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.<ref>

</ref><ref>Wind Power: Capacity Factor, Intermittency, and what happens when the wind doesn’t blow?. Retrieved 24 January 2008.</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, assuming all practical barriers needed were overcome. This would require wind turbines to be installed over large areas, particularly in areas of higher wind resources, such as offshore. As offshore wind speeds average ~90% greater than that of land, so offshore resources can contribute substantially more energy than land stationed turbines.<ref>“<cite>Offshore stations experience mean wind speeds at 80 m that are 90% greater than over land on average.</cite> Evaluation of global wind power<br />”<cite>Overall, the researchers calculated winds at 80 meters [300 feet] above sea level 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>“ Global Wind Map Shows Best Wind Farm Locations . Retrieved January 30, 2006.</ref>

Hydropower

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:

Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. There are now three hydroelectricity plants larger than 10 GW: the Three Gorges Dam in China, Itaipu Dam across the Brazil/Paraguay border, and Guri Dam in Venezuela.<ref name=wi2012>

</ref>

Solar energy

solar complex in northern San Bernadino County, California.]]

is a 150 MW solar photovoltaic power plant in Boulder City, Nevada.]]

Solar energy, radiant light and heat from the sun, is harnessed using a range of ever-evolving technologies such as solar heating, solar photovoltaics, solar thermal electricity, solar architecture and artificial photosynthesis.<ref name=ie11/><ref>Solar Fuels and Artificial Photosynthesis. Royal Society of Chemistry 2012 http://www.rsc.org/ScienceAndTechnology/Policy/Documents/solar-fuels.asp (accessed 11 March 2013)</ref>

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.

Solar power is the conversion of sunlight into electricity, either directly using photovoltaics (PV), or indirectly using concentrated solar power (CSP). Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Commercial concentrated solar power plants were first developed in the 1980s. Photovoltaics convert light into electric current using the photoelectric effect.<ref>

</ref> Photovoltaics are an important and relatively inexpensive source of electrical energy where grid power is inconvenient, unreasonably expensive to connect, or simply unavailable. However, as the cost of solar electricity is falling, solar power is also increasingly being used even in grid-connected situations as a way to feed low-carbon energy into the grid.

In 2011, the International Energy Agency said that “the development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits. It will increase countries’ energy security through reliance on an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments; they must be wisely spent and need to be widely shared”.<ref name=ie11>

</ref>

Biomass

plantation in Brazil (State of São Paulo), cane remains used to production of biomass energy.]]

plant in Metz, France. The station uses waste wood biomass as energy source, and provides electricity and heat for 30,000 dwellings.]]

Biomass is biological material derived from living, or recently living organisms. It most often refers to plants or plant-derived materials which are specifically called lignocellulosic biomass.<ref name=“Biomass Energy Center”>Biomass Energy Center. Biomassenergycentre.org.uk. Retrieved on 2012-02-28.</ref> As an energy source, biomass can either be used directly via combustion to produce heat, or indirectly after converting it to various forms of biofuel. Conversion of biomass to biofuel can be achieved by different methods which are broadly classified into: thermal, chemical, and biochemical methods.

Wood remains the largest biomass energy source today;<ref name=“online.wsj.com”>://online.wsj.com/article/SB10001424052702303740704577524822063133842.html Retrieved on 2012-04-12.</ref> examples include forest residues (such as dead trees, branches and tree stumps), yard clippings, wood chips and even municipal solid waste. In the second sense, biomass includes plant or animal matter that can be converted into fibers or other industrial chemicals, including biofuels. Industrial biomass can be grown from numerous types of plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum, sugarcane, bamboo,<ref>

</ref> and a variety of tree species, ranging from eucalyptus to oil palm (palm oil).

Plant energy is produced by crops specifically grown for use as fuel that offer high biomass output per hectare with low input energy. Some examples of these plants are wheat, which typically yield 7.5–8 tons (tonnes?) of grain per hectare, and straw, which typically yield 3.5–5 tons (tonnes?) per hectare in the UK.<ref>

</ref> The grain can be used for liquid transportation fuels while the straw can be burned to produce heat or electricity. Plant biomass can also be degraded from cellulose to glucose through a series of chemical treatments, and the resulting sugar can then be used as a first generation biofuel.

Biomass can be converted to other usable forms of energy like methane gas or transportation fuels like ethanol and biodiesel. Rotting garbage, and agricultural and human waste, all release methane gas—also called ”landfill gas“ or “biogas.” Crops, such as corn and sugar cane, can be fermented to produce the transportation fuel, ethanol. Biodiesel, another transportation fuel, can be produced from left-over food products like vegetable oils and animal fats.<ref>Energy Kids. Eia.doe.gov. Retrieved on 2012-02-28.</ref> Also, biomass to liquids (BTLs) and cellulosic ethanol are still under research.<ref>

</ref><ref>

</ref>

There is a great deal of research involving algal, or algae-derived, biomass due to the fact that it’s a non-food resource and can be produced at rates 5 to 10 times those of other types of land-based agriculture, such as corn and soy. Once harvested, it can be fermented to produce biofuels such as ethanol, butanol, and methane, as well as biodiesel and hydrogen.

The biomass used for electricity generation varies by region. Forest by-products, such as wood residues, are common in the United States. Agricultural waste is common in Mauritius (sugar cane residue) and Southeast Asia (rice husks). Animal husbandry residues, such as poultry litter, are common in the UK.<ref name=ODI1>Frauke Urban and Tom Mitchell 2011. Climate change, disasters and electricity generation. London: Overseas Development Institute and Institute of Development Studies</ref>

Biofuel

<!– This article is for a basic description of the main renewable energy technologies. Pros and cons of different technologies are discussed in Renewable energy debate. Thanks. –>

Biofuels include a wide range of fuels which are derived from biomass. The term covers solid biomass, liquid fuels and various biogases.<ref>

</ref> 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. The energy costs for producing bio-ethanol are almost equal to, the energy yields from bio-ethanol. However, according to the European Environment Agency, biofuels do not address global warming concerns.<ref name=eea-biofuels>

</ref>

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.<ref name=ren212011>

</ref>

Geothermal energy

in Iceland.]] Geothermal energy is from 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%).<ref>

</ref> 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 from deep within the Earth, all the way down to Earth’s core&nbsp;–

down. At the core, temperatures may reach over 9,000 °F (5,000 °C). 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

.<ref>

</ref>

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

Growth of renewables

[http://www.fs-unep-centre.org/publications/global-trends-renewable-energy-investment-2011 UNEP, Bloomberg, Frankfurt School, Global Trends in Renewable Energy Investment 2011]、Figure 24. />

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.<ref name=ren15/> 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.<ref name=“ren15”/> In 2010, renewable power constituted about a third of the newly built power generation capacities.<ref name=“UNEP_GT_2011_Fig24”/> 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 global indicators<ref name=“REN21 2011 15”/><ref>REN21 (2012). Renewables Global Status Report 2012 p. 17.</ref><ref>

</ref>

2008 2009 2010 2011 2012
Investment in new renewable capacity (annual) (109 USD) 130 160 211 257 244
Renewables power capacity (existing) (GWe) 1,140 1,230 1,320 1,360 1,470
Hydropower capacity (existing) (GWe) 885 915 945 970 990
Wind power capacity (existing) (GWe) 121 159 198 238 283
Solar PV capacity (grid-connected) (GWe) 16 23 40 70 100
Solar hot water capacity (existing) (GWth) 130 160 185 232 255
Ethanol production (annual) (109 litres) 67 76 86 86 83
Biodiesel production (annual) (109 litres) 12 17.8 18.5 21.4 22.5
Countries with policy targets <br /> for renewable energy use 79 89 98 118 138

Projections vary, but scientists have advanced a plan to power 100% of the world's energy with wind, hydroelectric, and solar power by the year 2030.<ref name=wws>

</ref><ref>

</ref>

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.<ref name=“Ben Sills”/>

projects that the levelized cost of wind power will decline 25% from 2012 to 2030.<ref>E. Lantz, M. Hand, and R. Wiser (May 13–17, 2012) "The Past and Future Cost of Wind Energy," National Renewable Energy Laboratory conference paper no. 6A20-54526, page 4</ref>]]

Renewable energy technologies are getting cheaper, through technological change and through the benefits of mass production and market competition. 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.”<ref name=henning>

</ref>

Hydro-electricity and geothermal electricity produced at favourable sites are now the cheapest way to generate electricity. Renewable energy costs continue to drop, and the levelised cost of electricity (LCOE) is declining for wind power, solar photovoltaic (PV), concentrated solar power (CSP) and some biomass technologies.<ref name=irena111>

</ref>

Renewable energy is also the most economic solution for new grid-connected capacity in areas with good resources. As the cost of renewable power falls, the scope of economically viable applications increases. Renewable technologies are now often the most economic solution for new generating capacity. Where “oil-fired generation is the predominant power generation source (e.g. on islands, off-grid and in some countries) a lower-cost renewable solution almost always exists today”.<ref name=irena111/>

A series of studies by the US National Renewable Energy Laboratory modeled the “grid in the Western US under a number of different scenarios where intermittent renewables accounted for 33 percent of the total power.” In the models, inefficiencies in cycling the fossil fuel plants to compensate for the variation in solar and wind energy resulted in an additional cost of “between $0.47 and $1.28 to each MegaWatt hour generated”; however, the savings in the cost of the fuels saved “adds up to $7 billion, meaning the added costs are, at most, two percent of the savings.”<ref name=ArsTechnica>

</ref>

Hydroelectricity

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 Three Gorges Dam is operated jointly with the much smaller Gezhouba Dam (3,115 MW).

, the total generating capacity of this two-dam complex is 25,615 MW. In 2008, this complex generated 98 TWh of electricity (81 TWh from the Three Gorges Dam and 17 TWh from the Gezhouba Dam), which is 3% more power in one year than the 95 TWh generated by Itaipu in 2008.

Wind power development

/>

at sunrise]]

Wind power is growing at over 20% annually, with a worldwide installed capacity of 238,000 MW at the end of 2011,<ref name=“REN21 2011 15”>

</ref><ref name=“businessweek1”>

</ref><ref name=“greeninc.blogs.nytimes.com”>Lars Kroldrup. Gains in Global Wind Capacity Reported Green Inc., February 15, 2010.</ref> and is widely used in Europe, Asia, and the United States.<ref name=“Glob”>Global wind energy markets continue to boom&nbsp;– 2006 another record year

(PDF).</ref><ref>

</ref> Several countries have achieved relatively high levels of wind power penetration, such as 21% of stationary electricity production in Denmark,<ref name=“wwea”>

</ref> 18% in Portugal,<ref name=“wwea”/> 16% in Spain,<ref name=“wwea”/> 14% in Ireland<ref>

</ref> and 9% in Germany in 2010.<ref name=“wwea”/><ref name=autogenerated2>

</ref> As of 2011, 83 countries around the world are using wind power on a commercial basis.<ref name=ren212011/>

Top 10 countries by nameplate windpower capacity <br> (2012 year-end)<ref name=gws-2012>

</ref>

Country Windpower capacity<br />(MW) % world total
China 75,564ǂ 26.8
United States 60,007 21.2
Germany 31,332 11.1
Spain 22,796 8.1
India 18,421 6.5
United Kingdom 8,845 3.0
Italy 8,144 2.9
France 7,196ǂ 2.5
Canada 6,200 2.2
Portugal 4,525 1.6
(rest of world) 39,853 14.1
World total 282,482 MW 100%

As of 2012, the Alta Wind Energy Center (California, 1,020 MW) is the world's largest wind farm.<ref name=terragen>Terra-Gen Closes on Financing for Phases VII and IX

, Business Wire, April 17, 2012</ref> The London Array (630 MW) is the largest offshore wind farm in the world. Phase 1 is complete, it is intended to introduce more turbines for Phase 2.<ref name=“la”>

</ref> The United Kingdom is the world's leading generator of offshore wind power, followed by Denmark.<ref>

</ref>

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).

Solar thermal

, PS20.]]

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

The Ivanpah Solar Power Facility is a 392 MW solar power facility which is under construction in south-eastern California.<ref name=mufson>Steven Mufson. Solar power project in Mojave Desert gets $1.4 billion boost from stimulus funds Washington Post, February 23, 2010.</ref> The Solana Generating Station is a 280 MW solar power plant which is under construction near Gila Bend, Arizona, about

southwest of Phoenix. The Crescent Dunes Solar Energy Project is a 110&nbsp;MW solar thermal power project currently under construction near Tonopah, about

northwest of Las Vegas.<ref name=“doe-2011-09-28”>

</ref>

The solar thermal power industry is growing rapidly with 1.3 GW under construction in 2012 and more planned. Spain is the epicenter of solar thermal power development with 873 MW under construction, and a further 271 MW under development.<ref>

</ref> In the United States, 5,600 MW of solar thermal power projects have been announced.<ref>

</ref> 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.<ref name=global>REN21 (2008). Renewables 2007 Global Status Report (PDF) p. 12.</ref>

Photovoltaic power stations

Photovoltaic power<br>(GW)<ref name=epia2012>

</ref>

2005 5.4
2006 7.0
2007 9.4
2008 15.7
2009 22.9
2010 39.7
2011 67.4
| 2012 100
<small>Year end capacities</small>

, 14 MW power plant installed 2007 in Nevada, USA.]]

Solar photovoltaic cells (PV) 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.<ref name=jr2010>James Russell. Record Growth in Photovoltaic Capacity and Momentum Builds for Concentrating Solar Power Vital Signs, June 3, 2010.</ref><ref>

</ref> While wind is often cited as the fastest growing energy source, photovoltaics since 2007 has been increasing at twice the rate of wind&nbsp;— 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 12.8, Japan 4.7, Spain 4.4, the USA 4.4, and China 3.1.<ref name=epia2012/><ref>

</ref>

Many solar photovoltaic power stations have been built, mainly in Europe.<ref name=“PV”>Denis Lenardic. Large-scale photovoltaic power plants ranking 1 - 50 PVresources.com, 2010.</ref> As of May 2012, the largest photovoltaic (PV) power plants in the world are the Agua Caliente Solar Project (USA, 247 MW), Charanka Solar Park (India, 214 MW), Golmud Solar Park (China, 200 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).<ref name=“PV”/>

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.<ref name=rew11>

</ref> The Topaz Solar Farm is a 550 MW photovoltaic power plant, being built in San Luis Obispo County, California.<ref name=re11>

</ref> 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&nbsp;MW solar photovoltaic power plant, which is being built by SunPower in the Carrizo Plain, northeast of California Valley.<ref>

</ref> 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.<ref>

</ref>

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.<ref>

</ref>

Biofuel development

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 provided 3% of the world's transport fuel in 2010.<ref name=ren212011/> Mandates for blending biofuels exist in 31 countries at the national level and in 29 states/provinces.<ref name=“ren212011”/> According to the International Energy Agency, biofuels have the potential to meet more than a quarter of world demand for transportation fuels by 2050.<ref>

</ref>

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.<ref name=“RFA1E”>

</ref> 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.<ref name=“MLA_2004”>

</ref> 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.<ref name=“Wilson”>

</ref>

Nearly all the gasoline sold in the United States today is mixed with 10% ethanol, a mix known as E10,<ref>Erica Gies. As Ethanol Booms, Critics Warn of Environmental Effect The New York Times, June 24, 2010.</ref> 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.<ref name=“Worldwatch”>

</ref> 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

of biofuels to be used annually by 2012, will also help to expand the market.<ref name=“Worldwatch”/>

Geothermal development

Geothermal power is cost effective, reliable, sustainable, and environmentally friendly,<ref>William E. Glassley. Geothermal Energy: Renewable Energy and the Environment CRC Press, 2010.</ref> 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.<ref name=gea2010/> 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.<ref name=gea2010>Geothermal Energy Association. Geothermal Energy: International Market Update May 2010, p. 4-6.</ref>

In 2010, the United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants;<ref name=geap7/> the largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California.<ref name=“Khan”>

</ref> 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.<ref name=geap7>Geothermal Energy Association. Geothermal Energy: International Market Update - May 2010, p. 7</ref>

Developing countries

s use sunlight as energy source for outdoor cooking.]]

promotional brochure.]]

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>Power for the People

p. 3.</ref>

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.<ref>

</ref> An estimated 3 million households get power from small solar PV systems.<ref name = re10>REN21 (2010). Renewables 2010 Global Status Report

p. 12.</ref> 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. Some Small Island Developing States (SIDS) are also turning to solar power to reduce their costs and increase their sustainability.<ref>Fry, Carolyn. 28 June 2012. Anguilla moves towards cleaner energy</ref>

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.<ref name=“REN21 2011 14”/> Clean liquid fuel sourced from renewable feedstocks are used for cooking and lighting in energy-poor areas of the developing world. Alcohol fuels (ethanol and methanol) can be produced sustainably from non-food sugary, starchy, and cellulostic feedstocks. Project Gaia, Inc. and CleanStar Mozambique are implementing clean cooking programs with liquid ethanol stoves in Ethiopia, Kenya, Nigeria and Mozambique.<ref>

</ref>

Renewable energy projects in many developing countries have demonstrated that renewable energy can directly contribute to poverty reduction 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>Energy for Development: The Potential Role of Renewable Energy in Meeting the Millennium Development Goals pp. 7-9.</ref>

/>

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.<ref name=autogenerated1>Joel Makower, Ron Pernick and Clint Wilder (2009). ''Clean Energy Trends 2009, Clean Edge, pp. 1-4.</ref> Leading renewable energy companies include First Solar, Gamesa, GE Energy, Q-Cells, Sharp Solar, Siemens, SunOpta, Suntech Power, and Vestas.<ref>REN21 (2008). Renewables 2007 Global Status Report (PDF) p. 18.</ref>

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.<ref>

</ref>

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&nbsp;countries signing the charter of IRENA.<ref>Signatory States

</ref> As of March 2010, IRENA has 143&nbsp;member states who all are considered as founding members, of which 14 have also ratified the statute.<ref>Signatories of IRENA’s statute

</ref>

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.<ref name=ren212011/>

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.<ref name=“renewableenergyworld1”/> 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”.<ref>

</ref>

100% renewable energy

The incentive to use 100% renewable energy has been created by global warming and other ecological as well as economic concerns. Renewable energy use has grown much faster than anyone anticipated.<ref name=pg11>

</ref> The Intergovernmental Panel on Climate Change has said that there are few fundamental technological limits to integrating a portfolio of renewable energy technologies to meet most of total global energy demand.<ref>

</ref> Mark Z. Jacobson says producing all new energy with wind power, solar power, and hydropower by 2030 is feasible and existing energy supply arrangements could be replaced by 2050. Barriers to implementing the renewable energy plan are seen to be “primarily social and political, not technological or economic”. Jacobson says that energy costs with a wind, solar, water system should be similar to today's energy costs.<ref name=enpol2011>

</ref> Critics of the “100% renewable energy” approach include Vaclav Smil and James Hansen.

Emerging technologies

Other renewable energy technologies are still under development, and include cellulosic ethanol, hot-dry-rock geothermal power, and ocean energy.<ref name=“IEA”>International Energy Agency (2007). ''Renewables in global energy supply: An IEA facts sheet''

(PDF), OECD, p. 3.</ref> 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.<ref name=“IEA” />

There are numerous organizations within the academic, federal, and commercial sectors conducting large scale advanced research in the field of renewable energy. This research spans several areas of focus across the renewable energy spectrum. Most of the research is targeted at improving efficiency and increasing overall energy yields.<ref>

</ref> Multiple federally supported research organizations have focused on renewable energy in recent years. Two of the most prominent of these labs are Sandia National Laboratories and the National Renewable Energy Laboratory (NREL), both of which are funded by the United States Department of Energy and supported by various corporate partners.<ref>

</ref> Sandia has a total budget of $2.4 billion<ref>

</ref> while NREL has a budget of $375 million.<ref>*Chakrabarty, Gargi, April 16th, 2009. “Stimulus leaves NREL in cold” Denver Post”</ref>

Cellulosic ethanol

Companies such as Iogen, POET, 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.<ref>Pernick, Ron and Wilder, Clint (2007). The Clean Tech Revolution p. 96.</ref>

Selected Commercial Cellulosic Ethanol Plants in the U.S.<ref>Decker, Jeff. Going Against the Grain: Ethanol from Lignocellulosics, Renewable Energy World, January 22, 2009.</ref><ref>

</ref> (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

Carbon-neutral and negative fuels

Carbon-neutral fuels are synthetic fuels (including methane, gasoline, diesel fuel, jet fuel or ammonia<ref>Leighty and Holbrook (2012) "Running the World on Renewables: Alternatives for Transmission and Low-cost Firming Storage of Stranded Renewables as Hydrogen and Ammonia Fuels via Underground Pipelines" Proceedings of the ASME 2012 International Mechanical Engineering Congress & Exposition November 9–15, 2012, Houston, Texas</ref>) produced by hydrogenating waste carbon dioxide recycled from power plant flue-gas emissions, recovered from automotive exhaust gas, or derived from carbonic acid in seawater.<ref name=Graves2011rev>

(Review.)</ref> Such fuels are considered carbon-neutral because they do not result in a net increase in atmospheric greenhouse gases.<ref name=Lackner2012>

</ref> To the extent that synthetic fuels displace fossil fuels, or if they are produced from waste carbon or seawater carbonic acid,<ref name=Eisaman2012>

</ref> and their combustion is subject to carbon capture at the flue or exhaust pipe, they result in negative carbon dioxide emission and net carbon dioxide removal from the atmosphere, and thus constitute a form of greenhouse gas remediation.<ref name=Goeppert2012>

(Review.)</ref>

Such renewable fuels alleviate the costs and dependency issues of imported fossil fuels without requiring either electrification of the vehicle fleet or conversion to hydrogen or other fuels, enabling continued compatible and affordable vehicles.<ref name=Pearson2012>

(Review.)</ref> Carbon-neutral fuels offer relatively low cost energy storage, alleviating the problems of wind and solar intermittency, and they enable distribution of wind, water, and solar power through existing natural gas pipelines.<ref name=Pearson2012 /> Nighttime wind power is considered the most economical form of electrical power with which to synthesize fuel, because the load curve for electricity peaks sharply during the warmest hours of the day, but wind tends to blow slightly more at night than during the day, so, the price of nighttime wind power is often much less expensive than any alternative.<ref name=Pearson2012/> Germany has built a 250 kilowatt synthetic methane plant which they are scaling up to 10 megawatts.<ref name=“zsw-bw1”>

</ref><ref name=“zsw-bw2”>

</ref><ref>

</ref>

The George Olah carbon dioxide recycling plant in Grindavík, Iceland has been producing 2 million liters of methanol transportation fuel per year from flue exhaust of the Svartsengi Power Station since 2011.<ref>"George Olah CO2 to Renewable Methanol Plant, Reykjanes, Iceland" (Chemicals-Technology.com)</ref> It has the capacity to produce 5 million liters per year.<ref>"First Commercial Plant" (Carbon Recycling International)</ref>

Marine energy

, second largest tidal power station at

]]

Marine energy (also sometimes referred to as ocean energy) refers to the energy carried by ocean waves, tides, salinity, and ocean temperature differences. The movement of water in the world’s oceans creates a vast store of kinetic energy, or energy in motion. This energy can be harnessed to generate electricity to power homes, transport and industries.

The term marine energy encompasses both wave power&nbsp;— power from surface waves, and tidal power&nbsp;— obtained from the kinetic energy of large bodies of moving water. Offshore wind power is not a form of marine energy, as wind power is derived from the wind, even if the wind turbines are placed over water.

The oceans have a tremendous amount of energy and are close to many if not most concentrated populations. Ocean energy has the potential of providing a substantial amount of new renewable energy around the world.<ref>Carbon Trust, Future Marine Energy. Results of the Marine Energy Challenge: Cost competitiveness and growth of wave and tidal stream energy, January 2006</ref>

Rank Station Country Location Capacity (MW)

1 Sihwa Lake Tidal Power Station

254 <ref>Korea JoongAng Daily: Turning tides

</ref>

2 Rance Tidal Power Station

240 <ref name=TidalPower>

</ref>

3 Annapolis Royal Generating Station

20 <ref name=TidalPower/>
4 Jiangxia Tidal Power Station

3.9 <ref name=TidalPower/><ref>

</ref>

5 Kislaya Guba Tidal Power Station

1.7 <ref name=TidalPower/>

Enhanced geothermal systems

File:EGS diagram.svg

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.<ref name=“Duchane”>

</ref> 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&nbsp;km) layer of insulating sediments which slow heat loss.<ref>20 slide presentation inc geothermal maps of Australia

</ref> 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&nbsp;MW.

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.

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.<ref>Collings AF and Critchley C (eds). Artificial Photosynthesis- From Basic Biology to Industrial Application (Wiley-VCH Weinheim 2005) p ix.</ref> Researchers in this field are striving to design molecular mimics of photosynthesis that utilize a wider region of the solar spectrum, employ catalytic systems made from abundant, inexpensive materials that are robust, readily repaired, non-toxic, stable in a variety of environmental conditions and perform more efficiently allowing a greater proportion of photon energy to end up in the storage compounds, i.e., carbohydrates (rather than building and sustaining living cells).<ref name=faunce>

</ref>

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.<ref>International Energy Agency (2007). Contribution of Renewables to Energy Security

IEA Information Paper, p. 5.</ref>

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.<ref>

</ref> 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. According to a town councilor, the overwhelming majority of locals believe that the Ardrossan Wind Farm in Scotland has enhanced the area.<ref name=“guardian.co.uk”>

</ref>

A recent UK Government document states that “projects are generally more likely to succeed if they have broad public support and the consent of local communities. This means giving communities both a say and a stake”.<ref>Department of Energy & Climate Change (2011). UK Renewable Energy Roadmap (PDF) p. 35.</ref> In countries such as Germany and Denmark many renewable projects are owned by communities, particularly through cooperative structures, and contribute significantly to overall levels of renewable energy deployment.<ref>DTI, Co-operative Energy: Lessons from Denmark and Sweden, Report of a DTI Global Watch Mission, October 2004</ref><ref>Morris C & Pehnt M, German Energy Transition: Arguments for a Renewable Energy Future, Heinrich Böll Foundation, November 2012</ref>

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.<ref name=“UNEP” /> New government spending, regulation and policies helped the industry weather the 2009 economic crisis better than many other sectors.<ref name=autogenerated3>Clean Edge (2009). Clean Energy Trends 2009 pp. 1–4.</ref>

References

Bibliography

renewable_energy.txt · Last modified: 2020/03/12 18:37 (external edit)