Sustainable energy

This article is about a concept related to renewable energy, of which sustainable energy is a superset.

Sustainable energy sources are energy sources which are not expected to be depleted in a timeframe relevant to the human race, and which therefore contribute to the sustainability of all species. This concept is termed sustainability. An additional criterion for strict sustainability, useful for short- and medium-term decisions is social and political sustainability of an energy technology.

Sustainable energy sources are most often regarded as including all renewable sources, such as solar power, wind power, wave power, geothermal power, tidal power, and others.

Fission power and fusion power meet the definition of sustainability, but there is controversy over whether or not they should be regarded as sustainable for social and political reasons.

Renewable energy technologies

Main article: Renewable energy commercialization

Renewable energy technologies are essential contributors to sustainable energy as they generally contribute to world energy security, reducing dependency on fossil fuel resources, and providing opportunities for mitigating greenhouse gases. The International Energy Agency has defined three generations of renewable energy technologies, reaching back more than 100 years:

• First-generation technologies emerged from the industrial revolution at the end of the 19th century and include hydropower, biomass combustion, and geothermal power and heat. Some of these technologies are still in widespread use.

• Second-generation technologies include solar heating and cooling, wind power, modern forms of bioenergy, and solar photovoltaics. These are now entering markets as a result of research, development and demonstration (RD&D) investments since the 1980s. The initial investment was prompted by energy security concerns linked to the oil crises of the 1970s but the continuing appeal of these renewables is due, at least in part, to environmental benefits. Many of the technologies reflect significant advancements in materials.

• Third-generation technologies are still under development and include advanced biomass gasification, biorefinery technologies, concentrating solar thermal power, hot-dry-rock geothermal power, and ocean energy. Advances in nanotechnology may also play a major role.

First- and second-generation technologies have entered the markets, and third-generation technologies heavily depend on long term RD&D commitments, where the public sector has a role to play.

First-generation technologies

Hydroelectric dam in cross section

First-generation technologies are most competitive in locations with abundant resources. Their future use depends on the exploration of the available resource potential, particularly in developing countries, and on overcoming challenges related to the environment and social acceptance. Among sources of renewable energy, hydroelectric plants have the advantages of being long-lived -- many existing plants have operated for more than 100 years. Also, hydroelectric plants are clean and have few emissions. Criticisms directed at large-scale hydroelectric plants include: dislocation of people living where the reservoirs are planned, and release of significant amounts of carbon dioxide during construction and flooding of the reservoir. However, it has been found that high emissions are associated only with shallow reservoirs in warm (tropical) locales. Generally speaking, hydroelectric plants produce much lower life-cycle emissions than other types of generation. Hydroelectric power, which underwent extensive development during growth of electrification in the 19th and 20th centuries, is experiencing resurgence of development in the 21st century. The areas of greatest hydroelectric growth are the booming economies of Asia. China is the development leader; however, other Asian nations are installing hydropower at a rapid pace. This growth is driven by much increased energy costs -- especially for imported energy -- and widespread desires for more domestically-produced, clean, renewable, and economical generation.

Second-generation technologies

The CIS Tower, Manchester, England, was clad in PV panels at a cost of £5.5 million. It started feeding electricity to the national grid in November 2005.

Markets for second-generation technologies are strong and growing, mainly in countries such as Germany, Spain, the United States, and Japan. The challenge is to broaden the market base for continued growth worldwide. Strategic deployment in one country not only reduces technology costs for users there, but also for those in other countries, contributing to overall cost reductions and performance improvement.

Solar heating systems are a well known second-generation technology and generally consist of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage, and a reservoir or tank for heat storage and subsequent use. The systems may be used to heat domestic hot water, swimming pool water, or for space heating. The heat can also be used for industrial applications or as an energy input for other uses such as cooling equipment. In many climates, a solar heating system can provide a very high percentage (50 to 75%) of domestic hot water energy.

In the 1980s and early 1990s, most photovoltaic modules provided Remote Area Power Supply, but from around 1995, industry efforts have focused increasingly on developing building integrated photovoltaics and power plants for grid connected applications (see Photovoltaic power stations article for details). There is currently a proposal to build a Solar power station in Victoria, Australia, which would be the world's largest PV power station, at 154 MW. Other large photovoltaic power stations, which have been proposed or are under construction, include: the Girrasol solar power plant (62 MW), Waldpolenz Solar Park (40 MW), and the Nellis Solar Power Plant (15 MW).

Worldwide installed capacity and prediction 1997-2010, Source: WWEA

Information on pump, California.

Some of the second-generation renewables, such as wind power, have high potential and have already realised relatively low production costs. At the end of 2006, worldwide capacity of wind-powered generators was 74,223 megawatts, and although it currently produces less than 1% of world-wide electricity use, it accounts for approximately 20% of electricity use in Denmark, 9% in Spain, and 7% in Germany. However, it may be difficult to site wind turbines in some areas for aesthetic or environmental reasons, and it may be difficult to integrate wind power into electricity grids in some cases.

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 result of this, together with the exploitation of domestic deep water oil sources, Brazil, which years ago had to import a large share of the petroleum needed for domestic consumption, recently reached complete self-sufficiency in oil.

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, DaimlerChrysler, 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 six million E85-compatible vehicles on U.S. roads.

Third-generation technologies

Third-generation technologies are still under development and include advanced biomass gasification, biorefinery technologies, solar thermal power stations, hot-dry-rock geothermal power, and ocean energy. Third-generation 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 RD&D funding.

According to the International Energy Agency, new bioenergy (biofuel) technologies being developed today, notably cellulosic ethanol biorefineries, could allow biofuels to play a much bigger role in the future than previously thought. 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.

Sketch of a Parabolic Trough Collector

File:Pelamis.JPG

Pelamis machine pointing into the waves: it attenuates the waves, gathering more energy than its narrow profile suggests. See Pelamis Wave Energy Converter

Solar thermal power stations have been successfully operating in California commercially since the late 1980s, including the largest solar power plant of any kind, the 350 MW Solar Energy Generating Systems. Nevada Solar One is another 64MW plant which has recently opened. Other parabolic trough power plants being proposed are two 50MW plants in Spain, and a 100MW plant in Israel.

In terms of Ocean energy, another third-generation technology, Portugal has the world's first commercial wave farm, the Aguçadora Wave Park, under construction in 2007. The farm will initially use three Pelmis P-750 machines generating 2.25 MW. and costs are put at 8.5 million euro. Subject to successful operation, a further 70 million euro is likely to be invested before 2009 on a further 28 machines to generate 525 MW. Funding for a wave farm in Scotland was announced in February, 2007 by the Scottish Executive, at a cost of over 4 million pounds, as part of a £13 million funding packages for ocean power in Scotland. The farm will be the world's largest with a capacity of 3 MW generated by four Pelamis machines. (see also Wave farm).

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

Solar power panels that use nanotechnology, which can create circuits out of individual silicon molecules, may cost half as much as traditional photovoltaic cells, according to executives and investors involved in developing the products. Nanosolar has secured more than $100 million from investors to build a factory for nanotechnology thin-film solar panels. The company expects the factory to open in 2010 and produce enough solar cells each year to generate 430 megawatts of power.

Sustainable energy

Renewable energy and energy efficiency are sometimes said to be the “twin pillars” of sustainable energy policy. Both resources must be developed in order to stabilize and reduce carbon dioxide emissions. Efficiency slows down energy demand growth so that rising clean energy supplies can make deep cuts in fossil fuel use. If energy use grows too fast, renewable energy development will chase a receding target. Likewise, unless clean energy supplies come online rapidly, slowing demand growth will only begin to reduce total emissions; reducing the carbon content of energy sources is also needed. Any serious vision of a sustainable energy economy thus requires commitments to both renewables and efficiency.

Renewable energy (and energy efficiency) are no longer niche sectors that are promoted only by governments and environmentalists. The increased levels of investment and the fact that much of the capital is coming from more conventional financial actors suggest that sustainable energy options are now becoming mainstream.

Climate change concerns coupled with high oil prices and increasing government support are driving increasing rates of investment in the sustainable energy industries, according to a trend analysis from the United Nations Environment Programme. The report says investment capital flowing into renewable energy climbed from $80 billion in 2005 to a record $100 billion in 2006. In 2007, the upward trend is continuing, with capital investments occurring in sectors and regions previously considered too risky and too illiquid to merit the attention of the institutional investment community. A recent report from Helmut Kaiser Consultancy of Zurich states that the generation and storage of renewable energy will be the fastest growing sector in energy market over the next 20 years.

Sustainable sources not considered renewable

Sustainable energy sources that aren't renewable are those whose stock is not replenished, but for which the presently available stocks are expected to last for as long as human civilization cares to use them.

These energy sources are derived from nuclear energy, as other forms of stored energy found on Earth do not have sufficient energy density to supply humanity indefinitely.

• Fission power uses the nuclear fission of heavy elements to release energy that drives a heat engine. Primary challenges with the use of fission power are the production of small quantities of highly-radioactive waste in the form of spent fuel, larger quantities of less-radioactive waste in the form of activated structural material, and (for use as a long-term power source) the need to perform intensive processing of highly-radioactive fuel bundles, both to reclaim unused fuel in spent fuel rods, and to reclaim plutonium 239 and uranium 233 that have been bred from uranium 238 and thorium 232, respectively.

• Fusion power uses the nuclear fusion of isotopes of hydrogen to release energy that drives a heat engine. Primary challenges with the use of fusion power are that the technology required to build a useful fusion power plant are still under development, and that substantial quantities of radioactive waste in the form of activated structural material is produced.

Fission power's long-term sustainability depends on the amount of uranium and thorium that is available to be mined. Estimates for fuel reserves vary widely, but if breeder reactors and fuel reprocessing are assumed, tend to be tens of thousands of years or longer (uranium is approximately as common in Earth's crust as tin or zinc (2 ppm), and thorium as common as lead (6 ppm)).

Fusion power's long-term sustainability depends on the amount of lithium that is available to be mined (for deuterium-tritium fusion), or the amount of deuterium available in seawater (for deuterium-deuterium fusion). Lithium is a reasonably common component of Earth's crust, being about 10 times as common as thorium (65 ppm). Deuterium (a hydrogen isotope) occurs wherever hydrogen is found (principally in water), at about 150 ppm. As it can be extracted easily from seawater, economically viable reserves of deuterium are for practical purposes unlimited.

Technical sustainability of nuclear power

Discussions are re-emerging on proper classification of nuclear energy under such umbrella terms as "renewable" and "sustainable" These attributes bring moral gains or eligibility for development aid under various jurisdictions.

The primary argument in favor of "renewable" status is the relatively inexhaustible supply of fuel available (uranium and thorium for fission or hydrogen for fusion). See also: Renewable energy, Nuclear power section.

Proponents, such as environmentalists James Lovelock, Patrick Moore (Greenpeace co-founder), Stewart Brand (creator of The Whole Earth Catalog), and Norris McDonald (president of the AAEA), also claim that nuclear power is at least as environmentally friendly as traditional sources of renewable energy, making it the best future solution to global warming and the world's growing need for energy. They note that nuclear power plants produce little carbon dioxide emissions and claim that the radioactive waste produced is minimal and well-contained, especially compared to fossil fuels.

In 2001, professors Jan Willem Storm van Leeuwen and Philip Smith released a study which argued that, though nuclear plants don't produce any Template:CarbonTemplate:Oxygen directly, the energy required for the rest of the nuclear fuel cycle (uranium mining, enrichment, transportation) and power plant life cycle (construction, maintenance, decommissioning) leads to significant carbon dioxide emissions, especially as usage of lower-grade uranium becomes necessary. In 2000, however, Frans H. Koch of the International Energy Agency reported that, although it is correct that the nuclear life cycle produces greenhouse gases, these emissions are actually less than the life cycle emissions of other renewables, like solar and wind, and drastically less than fossil fuels.

Political sustainability of nuclear power

The use of nuclear power is political and controversial because of the problem of storing radioactive waste for indefinite periods, the potential for severe radioactive contamination by accident or sabotage, and the possibility that its use could in some countries lead to the proliferation of nuclear weapons.

Serious nuclear accidents which have occurred include the 1986 Chernobyl disaster, the 1979 Three Mile Island accident, the 1957 Windscale fire, and the 1957 Mayak accident. The nuclear power industry went into a period of decline for some years following the Chernobyl and Three Mile Island accidents (see Nuclear power controversy).

Some critics of nuclear energy argue that deployment of nuclear reactors in many countries would accelerate the proliferation of nuclear weapons technology that has many links with civilian use of nuclear materials. Some nuclear reactors (especially heavy water moderated reactors) create the materials necessary for these weapons.

The issue of fuel reprocessing and/or long-term repository of nuclear waste materials also remains contentious. Very few countries have developed waste depositories for high-level radioactive waste (see: Yucca Mountain Repository USA; Gorleben Germany; Forsmark, Sweden).

Due to opposition to nuclear power many countries (Austria, Italy, Sweden, Germany) have effectively banned further development of nuclear energy showing a clear lack of political sustainability under present conditions. Some other countries, such as Australia, have never built a nuclear power station.

See also

• Avoiding Dangerous Climate Change
• Global warming
• Kyoto Protocol
• Ashden Awards
• Energy Globe Awards

External links

• Europe: No. 1 in Sustainable Energy

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