The Desert Sunlight Solar Farm is a 550 MW power plant in Riverside County, California, that uses thin-film CdTe-modules made by First Solar.[41] As of November 2014, the 550 megawatt Topaz Solar Farm was the largest photovoltaic power plant in the world. This was surpassed by the 579 MW Solar Star complex. The current largest photovoltaic power station in the world is Longyangxia Dam Solar Park, in Gonghe County, Qinghai, China.
Nearly all the gasoline sold in the United States today is mixed with 10% ethanol,[128] 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. By mid-2006, there were approximately 6 million ethanol compatible vehicles on U.S. roads.[129]
The electrical machine most commonly used for wind turbines applications are those acting as generators, with synchronous generators and induction generators (as shown) being commonly used in larger wind turbine generators, while smaller and home made wind turbines tend to use a low speed DC generator or Dynamo as they are small, cheap and a lot easier to connect up.

“California Invests in ‘By Location’ Distributed Energy Resources” • California leads the US with several pilot projects to reward rooftop solar energy generators and other distributed energy resources in specific locations as an alternative to having utilities meet needs by investing in upgrading their electricity generation networks. [CleanTechnica]
flywheel energy storage, pumped-storage hydroelectricity is more usable in stationary applications (e.g. to power homes and offices). In household power systems, conversion of energy can also be done to reduce smell. For example, organic matter such as cow dung and spoilable organic matter can be converted to biochar. To eliminate emissions, carbon capture and storage is then used.
All these electrical machines are electromechanical devices that work on Faraday’s law of electromagnetic induction. That is they operate through the interaction of a magnetic flux and an electric current, or flow of charge. As this process is reversible, the same machine can be used as a conventional electrical motor for converting the electrical power into mechanical power, or as a generator converting the mechanical power back into the electrical power.
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.[136] As of 2010, an estimated 3 million households get power from small solar PV systems.[137] 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 1[138]2 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.
Using 100% renewable energy was first suggested in a Science paper published in 1975 by Danish physicist Bent Sørensen.[150] It was followed by several other proposals, until in 1998 the first detailed analysis of scenarios with very high shares of renewables were published. These were followed by the first detailed 100% scenarios. In 2006 a PhD thesis was published by Czisch in which it was shown that in a 100% renewable scenario energy supply could match demand in every hour of the year in Europe and North Africa. In the same year Danish Energy professor Henrik Lund published a first paper[151] in which he addresses the optimal combination of renewables, which was followed by several other papers on the transition to 100% renewable energy in Denmark. Since then Lund has been publishing several papers on 100% renewable energy. After 2009 publications began to rise steeply, covering 100% scenarios for countries in Europe, America, Australia and other parts of the world.[152]

Several refineries that can process biomass and turn it into ethanol are built by companies such as Iogen, POET, and Abengoa, while other companies such as the Verenium Corporation, Novozymes, and Dyadic International[163] are producing enzymes which could enable future commercialization. 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.[164]
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. Leading renewable energy companies include First Solar, Gamesa, GE Energy, Hanwha Q Cells, Sharp Solar, Siemens, SunOpta, Suntech Power, and Vestas.[142]

In 2011 Mark Z. Jacobson, professor of civil and environmental engineering at Stanford University, and Mark Delucchi published a study on 100% renewable global energy supply in the journal Energy Policy. They found 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". They also found that energy costs with a wind, solar, water system should be similar to today's energy costs.[153]

It is hard to beat the advantages of solar: No moving parts. Warranties of 25 years are common for PV modules. No maintenance, other than the occasional hosing-off if you live in a dusty place. The installed price of a 6 kW wind turbine on a good height tower is about $50,000 (and we are not even counting the money you are going to sink into maintenance of that wind turbine). At the time of this writing, half that money will buy you about 7 kW of installed solar panels. In our not-so-sunny Ottawa location those solar modules will produce around 8,000 kWh of electrical energy per average year, and they will do that for 30 years or more.

In conclusion, I would say that however great the scientific importance of this discovery may be, its practical value will be no less obvious when we reflect that the supply of solar energy is both without limit and without cost, and that it will continue to pour down upon us for countless ages after all the coal deposits of the earth have been exhausted and forgotten.[36]


Environmental impact of wind power includes effect on wildlife, but can be mitigated if proper monitoring and mitigation strategies are implemented.[76] Thousands of birds, including rare species, have been killed by the blades of wind turbines,[77] though wind turbines contribute relatively insignificantly to anthropogenic avian mortality. For every bird killed by a wind turbine in the US, nearly 500,000 are killed by each of feral cats and buildings.[78] In comparison, conventional coal fired generators contribute significantly more to bird mortality, by incineration when caught in updrafts of smoke stacks and by poisoning with emissions byproducts (including particulates and heavy metals downwind of flue gases). Further, marine life is affected by water intakes of steam turbine cooling towers (heat exchangers) for nuclear and fossil fuel generators, by coal dust deposits in marine ecosystems (e.g. damaging Australia's Great Barrier Reef) and by water acidification from combustion monoxides.

Most horizontal axis turbines have their rotors upwind of its supporting tower. Downwind machines have been built, because they don't need an additional mechanism for keeping them in line with the wind. In high winds, the blades can also be allowed to bend which reduces their swept area and thus their wind resistance. Despite these advantages, upwind designs are preferred, because the change in loading from the wind as each blade passes behind the supporting tower can cause damage to the turbine.
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".[194] 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.[195][196]

Turbines used in residential applications can range in size from 400 Watts to 100 kW (100 kW for very large loads), depending on the amount of electricity you want to generate. For residential applications, you should establish an energy budget and see whether financial incentives are available. This information will help determine the turbine size you will need. Because energy efficiency is usually less expensive than energy production, making your house more energy efficient will probably be more cost effective and will reduce the size of the wind turbine you need (see How Can I Make My Home More Energy Efficient?). Wind turbine manufacturers, dealers, and installers can help you size your system based on your electricity needs and the specifics of your local wind resource and micro-siting.
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Since we mentioned maintenance: Consider that in a reasonably windy place a wind turbine can run 7000 hours or more per year. If it were a car, going at 50 km/h (30 mph), it would travel 350,000 km (or 200,000+ miles). That means you should plan for an annual inspection, and perform the needed maintenance (greasing for example), regardless of the recommendation of the manufacturer. It is just as important to inspect and maintain the tower annually. We know of a tower that collapsed because nuts worked themselves loose from their bolts over 2½ years time, no inspection nor maintenance were done during that time, ultimately leading to its undoing. Wind turbines and towers live in a very harsh environment. It is important to check for issues, such as loose bolts or tower guy wires that need re-tensioning, before they become a problem.

Photovoltaics (PV) uses solar cells assembled into solar panels to convert sunlight into electricity. It's a fast-growing technology doubling its worldwide installed capacity every couple of years. PV systems range from small, residential and commercial rooftop or building integrated installations, to large utility-scale photovoltaic power station. The predominant PV technology is crystalline silicon, while thin-film solar cell technology accounts for about 10 percent of global photovoltaic deployment. In recent years, PV technology has improved its electricity generating efficiency, reduced the installation cost per watt as well as its energy payback time, and has reached grid parity in at least 30 different markets by 2014.[115] Financial institutions are predicting a second solar "gold rush" in the near future.[116][117][118]
Moving towards energy sustainability will require changes not only in the way energy is supplied, but in the way it is used, and reducing the amount of energy required to deliver various goods or services is essential. Opportunities for improvement on the demand side of the energy equation are as rich and diverse as those on the supply side, and often offer significant economic benefits.[60]
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.[21] The heat can also be used for industrial applications or as an energy input for other uses such as cooling equipment.[22] In many climates, a solar heating system can provide a very high percentage (20 to 80%) 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 radiation comes from visible light. Solar power is complicated due to changes in seasons and from day to night. Cloud cover can also add to complications of solar energy, and not all radiation from the sun reaches earth because it is absorbed and dispersed due to clouds and gases within the earth's atmospheres.[23]
The locations with highest annual solar irradiance lie in the arid tropics and subtropics. Deserts lying in low latitudes usually have few clouds, and can receive sunshine for more than ten hours a day.[86][87] These hot deserts form the Global Sun Belt circling the world. This belt consists of extensive swathes of land in Northern Africa, Southern Africa, Southwest Asia, Middle East, and Australia, as well as the much smaller deserts of North and South America.[88] Africa's eastern Sahara Desert, also known as the Libyan Desert, has been observed to be the sunniest place on Earth according to NASA.[89][90]
In Denmark by 1900, there were about 2500 windmills for mechanical loads such as pumps and mills, producing an estimated combined peak power of about 30 (MW). The largest machines were on 24-meter (79 ft) towers with four-bladed 23-meter (75 ft) diameter rotors. By 1908 there were 72 wind-driven electric generators operating in the United States from 5 kW to 25 kW. Around the time of World War I, American windmill makers were producing 100,000 farm windmills each year, mostly for water-pumping.[9]
As the primary source of biofuel in North America, many organizations are conducting research in the area of ethanol production. On the Federal level, the USDA conducts a large amount of research regarding ethanol production in the United States. Much of this research is targeted towards the effect of ethanol production on domestic food markets.[105] The National Renewable Energy Laboratory has conducted various ethanol research projects, mainly in the area of cellulosic ethanol.[106] Cellulosic ethanol has many benefits over traditional corn based-ethanol. It does not take away or directly conflict with the food supply because it is produced from wood, grasses, or non-edible parts of plants.[107] Moreover, some studies have shown cellulosic ethanol to be more cost effective and economically sustainable than corn-based ethanol.[108] Even if we used all the corn crop that we have in the United States and converted it into ethanol it would only produce enough fuel to serve 13 percent of the United States total gasoline consumption.[109] Sandia National Laboratories conducts in-house cellulosic ethanol research[110] and is also a member of the Joint BioEnergy Institute (JBEI), a research institute founded by the United States Department of Energy with the goal of developing cellulosic biofuels.[111]
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.[63] An example of 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 power generating systems, granted publishing rights to the Alliance in 2007.

A: Modern solar panels typically last twenty to thirty years before there’s a noticeable increase in output loss. Most residential solar providers offer a 20- to 25-year warranty, but many such warranties only guarantee a certain power output (e.g., a guarantee of 80% output for twenty years). Carefully read through the fine print to make sure you understand the warranty and what it covers.
Since you are working hard to read this rather lengthy article, here is some entertainment. The ‘intermission’ if you like. So, put your feet up and enjoy the next picture: It’s a prime example of much that is wrong with the small wind world. The fact that an installer would even consider installing in a place like that. Customers that are too uninformed to know better (and their installer clearly is not interested in educating them). Turbine manufacturers that deliver standard towers that are much too short to be effective; this tower plus turbine is just 23 feet tall! Then there is the claim by the manufacturer (dutifully parroted by the installer) that this turbine will offset “up to 30%” of their electricity bill. The last one is not really a lie I suppose: If in reality it offsets just 2% of the owners bill, technically that still falls within that “up to 30%”…
Artificial photosynthesis uses techniques including nanotechnology to store solar electromagnetic energy in chemical bonds by splitting water to produce hydrogen and then using carbon dioxide to make methanol.[182] 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).[183] However, prominent research faces hurdles, Sun Catalytix a MIT spin-off stopped scaling up their prototype fuel-cell in 2012, because it offers few savings over other ways to make hydrogen from sunlight.[184]

Sunforce Wind Generators are primarily used to recharge all types of 12-Volt batteries, including lead-acid automotive batteries, deep-cycle (traction type) batteries, gel-cell batteries, and heavy-duty (stationary type) batteries. When using this wind generator to run appliances on a regular basis, the use of deep-cycle marine batteries is recommended. This type of battery is designed to withstand the frequent charge and discharge cycles associated with wind power use. Attempting to run the wind generator on an open circuit without a battery may cause damage to the generator or connected equipment.


In 2010, the United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants;[132] the largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California.[133] 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.[132]
Rated power of a wind turbine may not be quite as meaningless as cut-in wind speed, though its use is limited. It could have some utility to quickly compare, or get a feel for, the size of the wind turbine, but only if those rated power numbers were taken at the same rated wind speed, and if the manufacturer is giving you a realistic number (many inflate rated power). A much better measure of turbine size is, simply, their diameter. As shown above it is by far the best predictor for power output.
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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.[8] The results of a recent review of the literature[9] concluded that as greenhouse gas (GHG) emitters begin to be held liable for damages resulting from GHG emissions resulting in climate change, a high value for liability mitigation would provide powerful incentives for deployment of renewable energy technologies. In international public opinion surveys there is strong support for promoting renewable sources such as solar power and wind power.[10] 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.[11] 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. For example, in Denmark the government decided to switch the total energy supply (electricity, mobility and heating/cooling) to 100% renewable energy by 2050.[12]
In 2010, the International Energy Agency predicted that global solar PV capacity could reach 3,000 GW or 11% of projected global electricity generation by 2050—enough to generate 4,500 TWh of electricity.[40] Four years later, in 2014, the agency projected that, under its "high renewables" scenario, solar power could supply 27% of global electricity generation by 2050 (16% from PV and 11% from CSP).[2]
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