Sustainable energyFrom Wikipedia, the free encyclopedia

Sustainable energy is the sustainable provision of energy that meets the needs of the present withoutcompromising the ability of future generations to meet their needs. Technologies that promote sustainable energyinclude renewable energy sources, such as hydroelectricity, solar energy, wind energy, wave power, geothermalenergy, and tidal power, and also technologies designed to improve energy efficiency.

Contents1 Definitions2 Renewable energy technologies

2.1 First-generation technologies2.2 Second-generation technologies2.3 Third-generation technologies

3 Energy efficiency3.1 Energy Star3.2 Smart-grid Technology

4 Green energy4.1 Local green energy systems4.2 Using green energy

4.2.1 Carbon neutral and negative fuels4.3 Green energy and labelling by region

4.3.1 European Union4.3.2 United States

5 Sustainable energy research5.1 Solar5.2 Wind5.3 Ethanol biofuels5.4 Other Biofuels5.5 Geothermal5.6 Hydrogen

6 Clean energy investments6.1 Limits of government support for renewable energy investments

7 Nuclear power8 Related journals9 See also10 References

Definitions

Energy efficiency and renewable energy are said to be the twin pillars of sustainable energy.[1] Some ways in

which sustainable energy has been defined are:

"Effectively, the provision of energy such that it meets the needs of the present without compromising theability of future generations to meet their own needs. ...Sustainable Energy has two key components:renewable energy and energy efficiency." – Renewable Energy and Efficiency Partnership (British)[2]

"Dynamic harmony between equitable availability of energy-intensive goods and services to all people andthe preservation of the earth for future generations." And, "the solution will lie in finding sustainable energysources and more efficient means of converting and utilizing energy." – Sustainable energy by J. W. Tester,et al., from MIT Press."Any energy generation, efficiency & conservation source where: Resources are available to enable massivescaling to become a significant portion of energy generation, long term, preferably 100 years.." – Invest, agreen technology non-profit organization.[3]

"Energy which is replenishable within a human lifetime and causes no long-term damage to the environment."– Jamaica Sustainable Development Network[4]

This sets sustainable energy apart from other renewable energy terminology such as alternative energy andgreen energy, by focusing on the ability of an energy source to continue providing energy. Sustainable energy canproduce some pollution of the environment, as long as it is not sufficient to prohibit heavy use of the source for anindefinite amount of time. Sustainable energy is also distinct from Low-carbon energy, which is sustainable only inthe sense that it does not add to the CO2 in the atmosphere.

Green Energy is energy that can be extracted, generated, and/or consumed without any significant negative impactto the environment. The planet has a natural capability to recover which means pollution that does not go beyondthat capability can still be termed green.

Green power is a subset of renewable energy and represents those renewable energy resources and technologiesthat provide the highest environmental benefit. The U.S. Environmental Protection Agency defines green power aselectricity produced from solar, wind, geothermal, biogas, biomass, and low-impact small hydroelectric sources.Customers often buy green power for avoided environmental impacts and its greenhouse gas reduction benefits.[5]

Renewable energy technologiesMain articles: Renewable energy and Renewable energy commercialization

Renewable energy technologies are essential contributors to sustainable energy as they generally contribute to worldenergy security, reducing dependence on fossil fuel resources,[6] and providing opportunities for mitigatinggreenhouse gases.[6] The International Energy Agency states that:

Conceptually, one can define three generations of renewables technologies, reaching back more than100 years .

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

Second-generation technologies include solar heating and cooling, wind power, modern forms ofbioenergy, and solar photovoltaics. These are now entering markets as a result of research,

One of many power plants atThe Geysers, a geothermalpower field in northernCalifornia, with a total outputof over 750 MW.

Hydroelectric dams are one of themost widely deployed sources ofsustainable energy.

development and demonstration (RD&D) investments since the 1980s. The initial investment wasprompted by energy security concerns linked to the oil crises (1973 and 1979) of the 1970s but thecontinuing appeal of these renewables is due, at least in part, to environmental benefits. Many of thetechnologies 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 energy, andocean energy. Advances in nanotechnology may also play a major role.

—International Energy Agency, RENEWABLES IN GLOBAL ENERGY SUPPLY, An IEA FactSheet[6]

First- and second-generation technologies have entered the markets, and third-generation technologies heavilydepend on long term research and development commitments, where the public sector has a role to play.[6]

A 2008 comprehensive cost-benefit analysis review of energy solutions in the context of global warming and otherissues ranked wind power combined with battery electric vehicles (BEV) as the most efficient, followed byconcentrated solar power, geothermal power, tidal power, photovoltaic, wave power, coal capture and storage,nuclear energy, and finally biofuels.[7]

First-generation technologies

First-generation technologies are most competitive in locations withabundant resources. Their future use depends on the exploration of theavailable resource potential, particularly in developing countries, and onovercoming challenges related to the environment and social acceptance.

—International Energy Agency, RENEWABLES IN GLOBAL ENERGYSUPPLY, An IEA Fact Sheet[6]

Among sources of renewable energy, hydroelectric plants have the advantages ofbeing long-lived—many existing plants have operated for more than 100 years.Also, hydroelectric plants are clean and have few emissions. Criticisms directedat large-scale hydroelectric plants include: dislocation of people living where thereservoirs are planned, and release of significant amounts of carbon dioxideduring construction and flooding of the reservoir.[8]

However, it has been found that highemissions are associated only withshallow reservoirs in warm (tropical)locales, and recent innovations inhydropower turbine technology areenabling efficient development of low-impact run-of-the-river hydroelectricity projects.[9] Generally speaking,hydroelectric plants produce much lower life-cycle emissions than othertypes of generation. Hydroelectric power, which underwent extensivedevelopment during growth of electrification in the 19th and 20thcenturies, is experiencing resurgence of development in the 21st century.The areas of greatest hydroelectric growth are the booming economies ofAsia. China is the development leader; however, other Asian nations are

Hydroelectric dam in cross section

Wind power: worldwide installedcapacity [11]

installing hydropower at a rapid pace. This growth is driven by much increased energy costs—especially forimported energy—and widespread desires for more domestically produced, clean, renewable, and economicalgeneration.

Geothermal power plants can operate 24 hours per day, providing base-load capacity, and the world potential capacity for geothermal powergeneration is estimated at 85 GW over the next 30 years. However,geothermal power is accessible only in limited areas of the world,including the United States, Central America, East Africa, Iceland,Indonesia, and the Philippines. The costs of geothermal energy havedropped substantially from the systems built in the 1970s.[6] Geothermalheat generation can be competitive in many countries producinggeothermal power, or in other regions where the resource is of a lowertemperature. Enhanced geothermal system (EGS) technology does notrequire natural convective hydrothermal resources, so it can be used inareas that were previously unsuitable for geothermal power, if theresource is very large. EGS is currently under research at the U.S. Department of Energy.

Biomass briquettes are increasingly being used in the developing world as an alternative to charcoal. The techniqueinvolves the conversion of almost any plant matter into compressed briquettes that typically have about 70% thecalorific value of charcoal. There are relatively few examples of large scale briquette production. One exception isin North Kivu, in eastern Democratic Republic of Congo, where forest clearance for charcoal production isconsidered to be the biggest threat to Mountain Gorilla habitat. The staff of Virunga National Park have successfullytrained and equipped over 3500 people to produce biomass briquettes, thereby replacing charcoal producedillegally inside the national park, and creating significant employment for people living in extreme poverty in conflictaffected areas.[10]

Second-generation technologies

Markets for second-generation technologies are strong andgrowing, but only in a few countries. The challenge is to broadenthe market base for continued growth worldwide. Strategicdeployment in one country not only reduces technology costs forusers there, but also for those in other countries, contributing tooverall cost reductions and performance improvement.

—International Energy Agency, RENEWABLES IN GLOBALENERGY SUPPLY, An IEA Fact Sheet[6]

Solar heating systems are a well known second-generation technologyand generally consist of solar thermal collectors, a fluid system to movethe heat from the collector to its point of usage, and a reservoir or tank for heat storage and subsequent use. Thesystems may be used to heat domestic hot water, swimming pool water, or for space heating.[12] The heat can alsobe used for industrial applications or as an energy input for other uses such as cooling equipment.[13] In manyclimates, a solar heating system can provide a very high percentage (50 to 75%) of domestic hot water energy.Energy received from the sun by the earth is that of electromagnetic radiation. Light ranges of visible, infrared,ultraviolet, x-rays, and radio waves received by the earth through solar energy. The highest power of radiationcomes from visible light. Solar power is complicated due to changes in seasons and from day to night. Cloud covercan also add to complications of solar energy, and not all radiation from the sun reaches earth because it is

11 MW solar power plant near Serpa,Portugal

Sketch of a Parabolic Trough Collector

Information on pump, California

absorbed and dispersed due to clouds and gases within the earth's atmospheres.[14]

In the 1980s and early 1990s, most photovoltaic modules providedremote-area power supply, but from around 1995, industry efforts havefocused increasingly on developing building integrated photovoltaics andpower plants for grid connected applications (see photovoltaic powerstations article for details). Currently the largest photovoltaic power plantin North America is the Nellis Solar Power Plant (15 MW).[15][16] Thereis a proposal to build a Solar power station in Victoria, Australia, whichwould be the world's largest PV power station, at 154 MW.[17][18]

Other large photovoltaic power stations include the Girassol solar powerplant (62 MW),[19] and the Waldpolenz Solar Park (40 MW).[20]

Some of the second-generation renewables,

such as wind power, have high potential and have already realisedrelatively low production costs. At the end of 2008, worldwidewind farm capacity was 120,791 megawatts (MW), representing anincrease of 28.8 percent during the year,[21] and wind powerproduced some 1.3% of global electricity consumption.[22] Windpower accounts for approximately 20% of electricity use inDenmark, 9% in Spain, and 7% in Germany.[23][24] However, itmay be difficult to site wind turbines in some areas for aesthetic orenvironmental reasons, and it may be difficult to integrate windpower into electricity grids in some cases.[6]

Solar thermal power stations have been successfully operating inCalifornia commercially since the late 1980s, including the largestsolar power plant of any kind, the 350 MW Solar Energy Generating Systems. Nevada Solar One is another64MW plant which has recently opened.[25] Other parabolic trough power plants being proposed are two 50MWplants in Spain, and a 100MW plant in Israel.[26]

Brazil has one of the largest renewable energy programs in the world,involving production of ethanol fuel from sugar cane, and ethanol nowprovides 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 fordomestic consumption, recently reached complete self-sufficiency inoil.[27][28][29]

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 vehiclesdesigned 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.[30]

38°1′51″N 7°37′22″W

MIT's Solar House#1 built in 1939used Seasonal thermal energy storage(STES) for year round heating.

The world's first commercial[33] tidalstream generator – SeaGen – inStrangford Lough. The strong wakeshows the power in the tidal current.

Third-generation technologies

Third-generation technologies are not yet widely demonstrated orcommercialised. They are on the horizon and may have potentialcomparable to other renewable energy technologies, but stilldepend on attracting sufficient attention and RD&D funding. Thesenewest technologies include advanced biomass gasification,biorefinery technologies, solar thermal power stations, hot dryrock geothermal energy, and ocean energy.

—International Energy Agency, RENEWABLES IN GLOBALENERGY SUPPLY, An IEA Fact Sheet[6]

Bio-fuels may be defined as "renewable," yet may not be "sustainable,"due to soil degradation. As of 2012, 40% of Americas corn productiongoes toward ethanol. Ethanol takes up a large percentage of "CleanEnergy Use" when in fact, it is still debatable whether ethanol should beconsidered as a "Clean Energy."[3](http://www.nationalreview.com/planet-gore/270494/40-percent-corn-goes-ethanol-greg-pollowitz)

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 previouslythought.[31] Cellulosic ethanol can be made from plant matter composed primarily of inedible cellulose fibers thatform the stems and branches of most plants. Crop residues (such as corn stalks, wheat straw and rice straw), woodwaste, and municipal solid waste are potential sources of cellulosic biomass. Dedicated energy crops, such asswitchgrass, are also promising cellulose sources that can be sustainably produced in many regions of the UnitedStates.[32]

In terms of Ocean energy, another third-generation technology, Portugalhas the world's first commercial wave farm, the Aguçadora Wave Park,under construction in 2007. The farm will initially use three Pelamis P-750 machines generating 2.25 MW.[34][35] and costs are put at 8.5million euro. Subject to successful operation, a further 70 million euro islikely to be invested before 2009 on a further 28 machines to generate525 MW.[36] Funding for a wave farm in Scotland was announced inFebruary, 2007 by the Scottish Executive, at a cost of over 4 millionpounds, as part of a £13 million funding packages for ocean power inScotland. The farm will be the world's largest with a capacity of 3 MWgenerated by four Pelamis machines.[37] (see also Wave farm).

In 2007, the world's first turbine to create commercial amounts of energyusing tidal power was installed in the narrows of Strangford Lough inIreland. The 1.2 MW underwater tidal electricity generator takesadvantage of the fast tidal flow in the lough which can be up to 4m/s.

Although the generator is powerful enough to power up to a thousand homes, the turbine has a minimalenvironmental impact, as it is almost entirely submerged, and the rotors turn slowly enough that they pose no dangerto wildlife.[38][39]

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 theproducts. Nanosolar has secured more than $100 million from investors to build a factory for nanotechnology thin-film solar panels. The company's plant has a planned production capacity of 430 megawatts peak power of solarcells per year. Commercial production started and first panels have been shipped[40] to customers in late 2007.[41]

Large national and regional research projects on artificial photosynthesis are designing nanotechnology-basedsystems that use solar energy to split water into hydrogen fuel.[42] In 2011, researchers at the MassachusettsInstitute of Technology (MIT) developed what they are calling an "Artificial Leaf", which is capable of splittingwater into hydrogen and oxygen directly from solar power when dropped into a glass of water. One side of the"Artificial Leaf" produces bubbles of hydrogen, while the other side produces bubbles of oxygen.[43]

Most current solar power plants are made from an array of similar units where each unit is continuously adjusted,e.g., with some step motors, so that the light converter stays in focus of the sun light. The cost of focusing light onconverters such as high-power solar panels, Stirling engine, etc. can be dramatically decreased with a simple andefficient rope mechanics.[44] In this technique many units are connected with a network of ropes so that pulling twoor three ropes is sufficient to keep all light converters simultaneously in focus as the direction of the sun changes.

Energy efficiencyMoving towards energy sustainability will require changes not only in the way energy is supplied, but in the way it isused, and reducing the amount of energy required to deliver various goods or services is essential. Opportunities forimprovement on the demand side of the energy equation are as rich and diverse as those on the supply side, andoften offer significant economic benefits.[45]

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 slowsdown energy demand growth so that rising clean energy supplies can make deep cuts in fossil fuel use. If energy usegrows too fast, renewable energy development will chase a receding target. Likewise, unless clean energy suppliescome online rapidly, slowing demand growth will only begin to reduce total emissions; reducing the carbon contentof energy sources is also needed. Any serious vision of a sustainable energy economy thus requires commitments toboth renewables and efficiency.[46]

Renewable energy (and energy efficiency) are no longer niche sectors that are promoted only by governments andenvironmentalists. The increased levels of investment and the fact that much of the capital is coming from moreconventional financial actors suggest that sustainable energy options are now becoming mainstream.[47] An exampleof this would be The Alliance to Save Energy's Project with Stahl Consolidated Manufacturing, (Huntsville,Alabama, USA) (StahlCon 7), a patented generator shaft designed to reduce emissions within existing powergenerating systems, granted publishing rights to the Alliance in 2007.

Climate change concerns coupled with high oil prices and increasing government support are driving increasing ratesof investment in the sustainable energy industries, according to a trend analysis from the United NationsEnvironment Programme. According to UNEP, global investment in sustainable energy in 2007 was higher thanprevious levels, with $148 billion of new money raised in 2007, an increase of 60% over 2006. Total financialtransactions in sustainable energy, including acquisition activity, was $204 billion.[48]

Investment flows in 2007 broadened and diversified, making the overall picture one of greater breadth and depth ofsustainable energy use. The mainstream capital markets are "now fully receptive to sustainable energy companies,supported by a surge in funds destined for clean energy investment".[48]

A solar trough array is an example ofgreen energy

Energy Star

Main article: Energy Star

Energy Star is a company provides energy efficiency products for individuals or businesses. It is originated in theUSA, but now it becomes an international standard energy efficiency provider. From TV to a whole building,Energy Star can provide energy efficiency technology support.

If you see the Energy Star label on a laptop or printer, that means the product is in the Energy Star program whichis aiming at helping customers to save money and reduce green house gas. "ENERGY STAR is the trusted,government-backed symbol for energy efficiency helping us all save money and protect the environment throughenergy-efficient products and practices."[49]

Smart-grid Technology

Main article: Smart grid

Smart grid refers to a class of technology people are using to bring utility electricity delivery systems into the 21stcentury, using computer-based remote control and automation.[50] These systems are made possible by two-waycommunication technology and computer processing that has been used for decades in other industries. They arebeginning to be used on electricity networks, from the power plants and wind farms all the way to the consumers ofelectricity in homes and businesses. They offer many benefits to utilities and consumers—mostly seen in bigimprovements in energy efficiency on the electricity grid and in the energy users’ homes and offices.[50]

Green energyGreen energy includes natural energetic processes that can be harnessedwith little pollution. Anaerobic digestion, geothermal power, wind power,small-scale hydropower, solar energy, biomass power, tidal power,wave power, and some forms of nuclear power (ones which are able to"burn" nuclear waste through a process known as nuclear transmutation,e.g. an Integral Fast Reactor), and therefore belong in the "GreenEnergy" category). Some definitions may also include power derivedfrom the incineration of waste.

Some people, including Greenpeace founder and first member PatrickMoore[51][52][53],George Monbiot[54], Bill Gates[55] and JamesLovelock[56] have specifically classified nuclear power as green energy.Others, including Greenpeace[57][58] disagree, claiming that the problemsassociated with radioactive waste and the risk of nuclear accidents (such as the Chernobyl disaster) pose anunacceptable risk to the environment and to humanity. However, newer nuclear reactor designs are capable ofutilizing what is now deemed "nuclear waste" until it is no longer (or dramatically less) dangerous, and have designfeatures that greatly minimize the possibility of a nuclear accident. (See: Integral Fast Reactor)

No power source is entirely impact-free. All energy sources require energy and give rise to some degree ofpollution from manufacture of the technology. Some have argued that although green energy is a commendableeffort in solving the world's increasing energy consumption, it must be accompanied by a cultural change, namely

one that encourages the decrease of the world's appetite for energy, if it is to have the impact the world so eagerlyanticipates.[59]

In several countries with common carrier arrangements, electricity retailing arrangements make it possible forconsumers to purchase green electricity (renewable electricity) from either their utility or a green power provider.

When energy is purchased from the electricity network, the power reaching the consumer will not necessarily begenerated from green energy sources. The local utility company, electric company, or state power pool buys theirelectricity from electricity producers who may be generating from fossil fuel, nuclear or renewable energy sources.In many countries green energy currently provides a very small amount of electricity, generally contributing less than2 to 5% to the overall pool. In some U.S. states, local governments have formed regional power purchasing poolsusing Community Choice Aggregation and Solar Bonds to achieve a 51% renewable mix or higher, such as in theCity of San Francisco.[60]

By participating in a green energy program a consumer may be having an effect on the energy sources used andultimately might be helping to promote and expand the use of green energy. They are also making a statement topolicy makers that they are willing to pay a price premium to support renewable energy. Green energy consumerseither obligate the utility companies to increase the amount of green energy that they purchase from the pool (sodecreasing the amount of non-green energy they purchase), or directly fund the green energy through a green powerprovider. If insufficient green energy sources are available, the utility must develop new ones or contract with a thirdparty energy supplier to provide green energy, causing more to be built. However, there is no way the consumercan check whether or not the electricity bought is "green" or otherwise.

In some countries such as the Netherlands, electricity companies guarantee to buy an equal amount of 'greenpower' as is being used by their green power customers. The Dutch government exempts green power frompollution taxes, which means green power is hardly any more expensive than other power.

In the United States, one of the main problems with purchasing green energy through the electrical grid is the currentcentralized infrastructure that supplies the consumer’s electricity. This infrastructure has led to increasingly frequentbrown outs and black outs, high CO2 emissions, higher energy costs, and power quality issues.[61] An additional$450 billion will be invested to expand this fledgling system over the next 20 years to meet increasing demand.[62]

In addition, this centralized system is now being further overtaxed with the incorporation of renewable energies suchas wind, solar, and geothermal energies. Renewable resources, due to the amount of space they require, are oftenlocated in remote areas where there is a lower energy demand. The current infrastructure would make transportingthis energy to high demand areas, such as urban centers, highly inefficient and in some cases impossible. In addition,despite the amount of renewable energy produced or the economic viability of such technologies only about 20percent will be able to be incorporated into the grid. To have a more sustainable energy profile, the United Statesmust move towards implementing changes to the electrical grid that will accommodate a mixed-fuel economy.[63]

However, several initiatives are being proposed to mitigate these distribution problems. First and foremost, the mosteffective way to reduce USA’s CO2 emissions and slow global warming is through conservation efforts. Opponentsof the current US electrical grid have also advocated for decentralizing the grid. This system would increaseefficiency by reducing the amount of energy lost in transmission. It would also be economically viable as it wouldreduce the amount of power lines that will need to be constructed in the future to keep up with demand. Mergingheat and power in this system would create added benefits and help to increase its efficiency by up to 80-90%.This is a significant increase from the current fossil fuel plants which only have an efficiency of 34%.[64]

A more recent concept for improving our electrical grid is to beam microwaves from Earth-orbiting satellites or the

5 Kilowatt Vertical axis wind turbineby Green EcoSys & Electron SolarEnergy

moon to directly when and where there is demand. The power would be generated from solar energy captured onthe lunar surface In this system, the receivers would be “broad, translucent tent-like structures that would receivemicrowaves and convert them to electricity”. NASA said in 2000 that the technology was worth pursuing but it isstill too soon to say if the technology will be cost-effective.[65]

The World Wide Fund for Nature and several green electricity labelling organizations have created the EugeneGreen Energy Standard under which the national green electricity certification schemes can be accredited to ensurethat the purchase of green energy leads to the provision of additional new green energy resources.[66]

Local green energy systems

Main article: Microgeneration

Those not satisfied with the third-party grid approach to green energy viathe power grid can install their own locally based renewable energysystem. Renewable energy electrical systems from solar to wind to evenlocal hydro-power in some cases, are some of the many types ofrenewable energy systems available locally. Additionally, for thoseinterested in heating and cooling their dwelling via renewable energy,geothermal heat pump systems that tap the constant temperature of theearth, which is around 7 to 15 degrees Celsius a few feet undergroundand increases dramatically at greater depths, are an option overconventional natural gas and petroleum-fueled heat approaches. Also, ingeographic locations where the Earth's Crust is especially thin, or nearvolcanoes (as is the case in Iceland) there exists the potential to generateeven more electricity than would be possible at other sites, thanks to amore significant temperature gradient at these locales.

The advantage of this approach in the United States is that many statesoffer incentives to offset the cost of installation of a renewable energysystem. In California, Massachusetts and several other U.S. states, a newapproach to community energy supply called Community ChoiceAggregation has provided communities with the means to solicit a competitive electricity supplier and use municipalrevenue bonds to finance development of local green energy resources. Individuals are usually assured that theelectricity they are using is actually produced from a green energy source that they control. Once the system is paidfor, the owner of a renewable energy system will be producing their own renewable electricity for essentially nocost and can sell the excess to the local utility at a profit.

Using green energy

Main articles: Energy storage and Grid energy storage

Renewable energy, after its generation, needs to be stored in a medium for use with autonomous devices as well asvehicles. Also, to provide household electricity in remote areas (that is areas which are not connected to the mainselectricity grid), energy storage is required for use with renewable energy. Energy generation and consumptionsystems used in the latter case are usually stand-alone power systems.

Some examples are:

A 01 KiloWatt Micro Windmill forDomestic Usage

energy carriers as hydrogen, liquid nitrogen, compressed air, oxyhydrogen, batteries, to power vehicles.flywheel energy storage, pumped-storage hydroelectricity is more usable in stationary applications (e.g. topower homes and offices. In household power systems, conversion of energy can also be done to reducesmell. For example organic matter such as cow dung and spoilable organic matter can be converted tobiochar. To eliminate emissions, carbon capture and storage is then used.

Usually however, renewable energy is derived from the mains electricity grid. This means that energy storage ismostly not used, as the mains electricity grid is organised to produce theexact amount of energy being consumed at that particular moment.Energy production on the mains electricity grid is always set up as acombination of (large-scale) renewable energy plants, as well as otherpower plants as fossil-fuel power plants and nuclear power. Thiscombination however, which is essential for this type of energy supply (ase.g. wind turbines, solar power plants etc.) can only produce when thewind blows and the sun shines. This is also one of the main drawbacks ofthe system as fossil fuel powerplants are polluting and are a main cause ofglobal warming (nuclear power being an exception). Although fossil fuelpower plants too can made emissionless (through carbon capture andstorage), as well as renewable (if the plants are converted to e.g.biomass) the best solution is still to phase out the latter power plants overtime. Nuclear power plants too can be more or less eliminated from theirproblem of nuclear waste through the use of nuclear reprocessing andnewer plants as fast breeder and nuclear fusion plants.

Renewable energy power plants do provide a steady flow of energy. For example hydropower plants, oceanthermal plants, osmotic power plants all provide power at a regulated pace, and are thus available power sources atany given moment (even at night, windstill moments etc.). At present however, the number of steady-flowrenewable energy plants alone is still too small to meet energy demands at the times of the day when the irregularproducing renewable energy plants cannot produce power.

Besides the greening of fossil fuel and nuclear power plants, another option is the distribution and immediate use ofpower from solely renewable sources. In this set-up energy storage is again not necessary. For example, TREC hasproposed to distribute solar power from the Sahara to Europe. Europe can distribute wind and ocean power to theSahara and other countries. In this way, power is produced at any given time as at any point of the planet as the sunor the wind is up or ocean waves and currents are stirring. This option however is probably not possible in theshort-term, as fossil fuel and nuclear power are still the main sources of energy on the mains electricity net andreplacing them will not be possible overnight.

Several large-scale energy storage suggestions for the grid have been done. This improves efficiency and decreasesenergy losses but a conversion to an energy storing mains electricity grid is a very costly solution. Some costs couldpotentially be reduced by making use of energy storage equipment the consumer buys and not the state. Anexample is car batteries in personal vehicles that would double as an energy buffer for the electricity grid. Howeverbesides the cost, setting-up such a system would still be a very complicated and difficult procedure. Also, energystorage apparatus' as car batteries are also built with materials that pose a threat to the environment (e.g. sulphuricacid). The combined production of batteries for such a large part of the population would thus still not quiteenvironmental. Besides car batteries however, other large-scale energy storage suggestions for the grid have beendone which make use of less polluting energy carriers (e.g. compressed air tanks and flywheel energy storage).

Carbon neutral and negative fuels

Main article: Carbon neutral fuel

A carbon neutral fuel is a synthetic fuel — such as methane, gasoline, diesel fuel or jet fuel — produced fromrenewable or nuclear energy used to hydrogenate waste carbon dioxide recycled from power plant flue-gasemissions, recovered from automotive exhaust gas, or derived from carbonic acid in seawater.[67][68][69][70][71]

Such fuels are carbon neutral because they do not result in a net increase in atmospheric greenhouse gases.[72][73]

To the extent that carbon neutral fuels displace fossil fuels, or if they are produced from waste carbon or seawatercarbonic acid, and their combustion is subject to carbon capture at the flue or exhaust pipe, they result in negativecarbon dioxide emission and net carbon dioxide removal from the atmosphere, and thus constitute a form ofgreenhouse gas remediation.[74][75][76] Such fuels are produced by the electrolysis of water to make hydrogen usedin turn in the Sabatier reaction to produce methane which may then be stored to be burned later in power plants assynthetic natural gas, transported by pipeline, truck, or tanker ship, or be used in gas to liquids processes such asthe Fischer–Tropsch process to make traditional transportation or heating fuels.[77][78][79]

Carbon neutral fuels can provide easily distributed storage for renewable energy, eliminating the problems of windand solar intermittency, and enabling transmission of wind, water, and solar power through existing natural gaspipelines. Such renewable fuels alleviate the costs and dependency issues of imported fossil fuels without requiringeither electrification of the vehicle fleet or conversion to hydrogen or other fuels, enabling continued compatible andaffordable vehicles.[77] Germany has built a 250 kilowatt synthetic methane plant which they are scaling up to 10megawatts.[80][81][82] Commercial developments are taking place in Columbia, South Carolina,[83] Camarillo,California,[84] and Darlington, England.[85]

The least expensive source of carbon for recycling into fuel is flue-gas emissions from fossil-fuel combustion whereit can be extracted for about USD $7.50 per ton.[69][73][78] Automobile exhaust gas capture has also been shownto be economical in theory, but would require extensive design changes or retrofitting.[70] The carbonic acid inseawater is in chemical equilibrium with atmospheric carbon dioxide. The United States Navy has done extensivework studying and scaling up the extraction of carbon from seawater.[86][87] Work at the Palo Alto ResearchCenter has improved substantially on the Navy processes, resulting in carbon extraction from seawater for about$50 per ton.[71] Carbon capture from ambient air is very much more costly, at between $600 and $1000 per ton.At present that is considered an impractical cost for fuel synthesis or carbon sequestration.[73][74]

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 blowslightly more at night than during the day. Therefore, the price of nighttime wind power is often much less expensivethan any alternative. Off-peak wind power prices in high wind penetration areas of the U.S. averaged 1.64 centsper kilowatt-hour in 2009, and only 0.71 cents/kWh during the least expensive six hours of the day.[77] Typically,wholesale electricity costs 2 to 5 cents/kWh during the day.[88] Commercial fuel synthesis companies suggest theycan produce fuel for less than petroleum fuels when oil costs more than $55 per barrel.[89] The US Navy estimatesthat shipboard production of jet fuel from nuclear power would cost about $6 per gallon. While that was abouttwice the petroleum fuel cost in 2010, it is expected to be much less than the market price in less than five years ifrecent trends continue. Moreover, since the delivery of fuel to a carrier battle group costs about $8 per gallon,shipboard production is already much less expensive.[90] The Navy's estimate that 100 megawatts can produce41,000 gallons of fuel per day indicates that terrestrial production from wind power would cost less than $1 pergallon.[91]

Green energy and labelling by region

European Union

See also: Green electricity in the United Kingdom

Directive 2004/8/EC of the European Parliament and of the Council of 11 February 2004 on the promotion ofcogeneration based on a useful heat demand in the internal energy market[92] includes the article 5 (Guarantee oforigin of electricity from high-efficiency cogeneration).

European environmental NGOs have launched an ecolabel for green power. The ecolabel is called EKOenergy. Itsets criteria for sustainability, additionality, consumer information and tracking. Only part of electricity produced byrenewables fulfills the EKOenergy criteria.[93]

A Green Energy Supply Certification Scheme was launched in the United Kingdom in February 2010. Thisimplements guidelines from the Energy Regulator, Ofgem, and sets requirements on transparency, the matching ofsales by renewable energy supplies, and additionality.[94]

United States

The United States Department of Energy (DOE), the Environmental Protection Agency (EPA), and the Center forResource Solutions (CRS)[95] recognizes the voluntary purchase of electricity from renewable energy sources (alsocalled renewable electricity or green electricity) as green power.[96]

The most popular way to purchase renewable energy as revealed by NREL data is through purchasing RenewableEnergy Certificates (RECs). According to a Natural Marketing Institute (NMI)[97] survey 55 percent of Americanconsumers want companies to increase their use of renewable energy.[96]

DOE selected six companies for its 2007 Green Power Supplier Awards, including Constellation NewEnergy;3Degrees; Sterling Planet; SunEdison; Pacific Power and Rocky Mountain Power; and Silicon Valley Power. Thecombined green power provided by those six winners equals more than 5 billion kilowatt-hours per year, which isenough to power nearly 465,000 average U.S. households.

The U.S. Environmental Protection Agency (USEPA) Green Power Partnership is a voluntary program thatsupports the organizational procurement of renewable electricity by offering expert advice, technical support, toolsand resources. This can help organizations lower the transaction costs of buying renewable power, reduce carbonfootprint, and communicate its leadership to key stakeholders.[98]

Throughout the country, more than half of all U.S. electricity customers now have an option to purchase some typeof green power product from a retail electricity provider. Roughly one-quarter of the nation's utilities offer greenpower programs to customers, and voluntary retail sales of renewable energy in the United States totaled more than12 billion kilowatt-hours in 2006, a 40% increase over the previous year.

Sustainable energy researchThere are numerous organizations within the academic, federal, and commercial sectors conducting large scaleadvanced research in the field of sustainable energy. This research spans several areas of focus across the

The National Renewable EnergyLaboratory projects that the levelizedcost of wind power in the U.S. willdecline about 25% from 2012 to2030.[109]

sustainable energy spectrum. Most of the research is targeted at improving efficiency and increasing overall energyyields.[99] Multiple federally supported research organizations have focused on sustainable energy in recent years.Two of the most prominent of these labs are Sandia National Laboratories and the National Renewable EnergyLaboratory (NREL), both of which are funded by the United States Department of Energy and supported byvarious corporate partners.[100] Sandia has a total budget of $2.4 billion [101] while NREL has a budget of $375million.[102]

Solar

Main article: Solar power

The primary obstacle that is preventing the large scale implementation of solar powered energy generation is theinefficiency of current solar technology. Currently, photovoltaic (PV) panels only have the ability to convert around16% of the sunlight that hits them into electricity.[103] At this rate, many experts believe that solar energy is notefficient enough to be economically sustainable given the cost to produce the panels themselves. Both SandiaNational Laboratories and the National Renewable Energy Laboratory (NREL), have heavily funded solar researchprograms. The NREL solar program has a budget of around $75 million [104] and develops research projects in theareas of photovoltaic (PV) technology, solar thermal energy, and solar radiation.[105] The budget for Sandia’s solardivision is unknown, however it accounts for a significant percentage of the laboratory’s $2.4 billion budget.[106]

Several academic programs have focused on solar research in recent years. The Solar Energy Research Center(SERC) at University of North Carolina (UNC) has the sole purpose of developing cost effective solar technology.In 2008, researchers at Massachusetts Institute of Technology (MIT) developed a method to store solar energy byusing it to produce hydrogen fuel from water.[107] Such research is targeted at addressing the obstacle that solardevelopment faces of storing energy for use during nighttime hours when the sun is not shining. In February 2012,North Carolina-based Semprius Inc., a solar development company backed by German corporation Siemens,announced that they had developed the world’s most efficient solar panel. The company claims that the prototypeconverts 33.9% of the sunlight that hits it to electricity, more than double the previous high-end conversion rate.[108]

Wind

Main articles: Wind power and Wind farm

Wind energy research dates back several decades to the 1970s whenNASA developed an analytical model to predict wind turbine powergeneration during high winds.[110] Today, both Sandia NationalLaboratories and National Renewable Energy Laboratory have programsdedicated to wind research. Sandia’s laboratory focuses on theadvancement of materials, aerodynamics, and sensors.[111] The NRELwind projects are centered on improving wind plant power production,reducing their capital costs, and making wind energy more cost effectiveoverall.[112]

The Field Laboratory for Optimized Wind Energy (FLOWE) at CalTech was established to research renewableapproaches to wind energy farming technology practices that have the potential to reduce the cost, size, andenvironmental impact of wind energy production.[113]

A wind farm is a group of wind turbines in the same location used to produce electric power. A large wind farm

Bangui Wind Farm in the Philippines.

Lillgrund Wind Farm in Sweden

First wind farm consisting of 7,5 MW Enercon E-126 turbines, Estinnes, Belgium, 20 July 2010, twomonths before completion; note the 2-part blades.

may consist of several hundred individual wind turbines, andcover an extended area of hundreds of square miles, but theland between the turbines may be used for agricultural orother purposes. A wind farm may also be located offshore.

Many of the largest operational onshore wind farms arelocated in the USA and China. The Gansu Wind Farm inChina has over 5,000 MW installed with a goal of 20,000MW by 2020. China has several other "wind power bases"of similar size. The Alta Wind Energy Center in California isthe largest onshore wind farm outside of China, with acapacity of 1020 MW of power.[114] As of February 2012,the Walney Wind Farm in United Kingdom is the largestoffshore wind farm in the world at 367 MW, followed byThanet Offshore Wind Project (300 MW), also in the UK.

There are many large wind farms under construction andthese include Anholt Offshore Wind Farm (400 MW),BARD Offshore 1 (400 MW), Clyde Wind Farm (350MW), Greater Gabbard wind farm (500 MW), Lincs WindFarm (270 MW), London Array (1000 MW), LowerSnake River Wind Project (343 MW), Macarthur WindFarm (420 MW), Shepherds Flat Wind Farm (845 MW),and Sheringham Shoal (317 MW).

Ethanol biofuels

Main article: Ethanol

As the primary source of biofuels in North America, manyorganizations are conducting research in the area of ethanolproduction. On the Federal level, the USDA conducts alarge amount of research regarding ethanol production in theUnited States. Much of this research is targeted towards theeffect of ethanol production on domestic food markets.[115]

The National Renewable Energy Laboratory has conducted various ethanol research projects, mainly in the area ofcellulosic ethanol.[116] Cellulosic ethanol has many benefits over traditional corn based-ethanol. It does not takeaway or directly conflict with the food supply because it is produced from wood, grasses, or non-edible parts ofplants.[117] Moreover, some studies have shown cellulosic ethanol to be more cost effective and economicallysustainable than corn-based ethanol.[118] Sandia National Laboratories conducts in-house cellulosic ethanolresearch [119] and is also a member of the Joint BioEnergy Institute (JBEI), a research institute founded by theUnited States Department of Energy with the goal of developing cellulosic biofuels.[120]

Other Biofuels

Main article: Biofuel

From 1978 to 1996, the National Renewable Energy Laboratory experimented with using algae as a biofuelssource in the "Aquatic Species Program.”[121] A self-published article by Michael Briggs, at the University of NewHampshire Biofuels Group, offers estimates for the realistic replacement of all motor vehicle fuel with biofuels byutilizing algae that have a natural oil content greater than 50%, which Briggs suggests can be grown on algae pondsat wastewater treatment plants.[122] This oil-rich algae can then be extracted from the system and processed intobiofuels, with the dried remainder further reprocessed to create ethanol. The production of algae to harvest oil forbiofuels has not yet been undertaken on a commercial scale, but feasibility studies have been conducted to arrive atthe above yield estimate. In addition to its projected high yield, algaculture— unlike food crop-based biofuels —does not entail a decrease in food production, since it requires neither farmland nor fresh water. Many companiesare pursuing algae bio-reactors for various purposes, including scaling up biofuels production to commerciallevels.[123][124] Several groups in various sectors are conducting research on Jatropha curcas, a poisonous shrub-like tree that produces seeds considered by many to be a viable source of biofuels feedstock oil.[125] Much of thisresearch focuses on improving the overall per acre oil yield of Jatropha through advancements in genetics, soilscience, and horticultural practices. SG Biofuels, a San Diego-based Jatropha developer, has used molecularbreeding and biotechnology to produce elite hybrid seeds of Jatropha that show significant yield improvements overfirst generation varieties.[126] The Center for Sustainable Energy Farming (CfSEF) is a Los Angeles-based non-profit research organization dedicated to Jatropha research in the areas of plant science, agronomy, andhorticulture. Successful exploration of these disciplines is projected to increase Jatropha farm production yields by200-300% in the next ten years.[127]

Geothermal

Main article: Geothermal electricity

Geothermal energy is produced by tapping into the thermal energy created and stored within the earth. It isconsidered sustainable because that thermal energy is constantly replenished.[128] However, the science ofgeothermal energy generation is still young and developing economic viability. Several entities, such as the NationalRenewable Energy Laboratory [129] and Sandia National Laboratories [130] are conducting research toward thegoal of establishing a proven science around geothermal energy. The International Centre for Geothermal Research(IGC), a German geosciences research organization, is largely focused on geothermal energy developmentresearch.[131]

Hydrogen

Main article: Hydrogen fuel

Over $1 billion of federal money has been spent on the research and development of hydrogen fuel in the UnitedStates.[132] Both the National Renewable Energy Laboratory [133] and Sandia National Laboratories [134] havedepartments dedicated to hydrogen research. Hydrogen is useful for energy storage and for use in airplanes, but isnot practical for automobile use, as it is not very efficient, compared to using a battery - for the same cost you cango three times as far using a battery.[135]

Clean energy investments2010 was a record year for green energy investments. According to a report from Bloomberg New EnergyFinance, nearly US $243 billion was invested in wind farms, solar power, electric cars, and other alternative

The deuterium-tritium(D-T) reaction

technologies worldwide, representing a 30 percent increase from 2009 and nearly five times the money invested in2004. China had $51.1 billion investment in clean energy projects in 2010, by far the largest figure for anycountry.[136]

Within the emerging economies, Brazil comes second to China in terms of clean energy investments. Supported bystrong energy policies, Brazil has one of the world’s highest biomass and small-hydro power capacities and ispoised for significant growth in wind energy investment. The cumulative investment potential in Brazil from 2010 to2020 is projected as $67 billion.[136]

India is another rising clean energy leader. While India ranked the 10th in private clean energy investments amongG-20 members in 2009, over the next 10 years it is expected to rise to the third position, with annual clean energyinvestment under current policies forecast to grow by 369 percent between 2010 and 2020.[136]

It is clear that the center of growth has started to shift to the developing economies and they may lead the world inthe new wave of clean energy investments.[136]

Limits of government support for renewable energy investments

Research conducted by the World Pensions Council (WPC) suggests that the failure of Solyndra in August 2011should be viewed within the broader context of unsustainable government spending on sustainable energy, and thatthe Solyndra bankruptcy was a harbinger of the collapse of the German solar cell industry in the first quarter of2012- both events being "stark reminders of the risks that go with disproportionate levels of leveraging and thereliance on unsustainable government subsidies and unreasonable fiscal incentives to 'stimulate' demand. In manyways, real estate and solar energy assets were de facto owned by 'unnatural owners' such as banks, and, when thebanks collapsed, by Western governments unable or unwilling to provide fresh capital" in a context of fiscalausterity and tighter credit limits.[137]

Nuclear powerThere are potentially two sources of nuclear power. Fission is used in all currentnuclear power plants. Fusion is the reaction that exists in stars, including the sun, andremains impractical for use on earth, as fusion reactors are not available, and havebeen "fifty years away" - for the last fifty years.[138]

Conventional fission power is sometimes referred to as sustainable, but this iscontroversial politically due to concerns about peak uranium, radioactive wastedisposal, and the risks of a severe accident.

Fission nuclear power has the potential to significantly expand its sustainability from afuel and waste perspective, such as by the use of breeder reactors; however,significant challenges exist in expanding the role of nuclear power in such amanner.[139]

Nuclear fission has four inherent liabilities - radiation, risk of accident, waste, and risk of proliferation of nuclearweapons, and is not likely to have a significant role, due to the vast availability of wind power and solarpower.[140][141]

Related journalsAmong scientific journals related to the interdisciplinary study of sustainable energy are:

Energy and Environmental ScienceEnergy for Sustainable DevelopmentEnergy PolicyEnergy SystemsJournal of Renewable and Sustainable EnergyRenewable and Sustainable Energy Reviews

See also

Ashden Awards for sustainable energyBiosphere TechnologyEnergy and the environmentEnergy Globe AwardsEnergy parkEnergy StarEnvironmental issues with energyHydrogen economyINFORSE, International Network for Sustainable EnergyInternational Renewable Energy AgencyLeadership in Energy and Environmental Design (LEED)REEEP, Renewable Energy and Energy Efficiency PartnershipRenewable Energy (not the same)Smart gridU.S. Department of Energy Solar DecathlonSustainable Energy for All initiativeThe Venus Project

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