Other renewable energy technologies are still under development, and include cellulosic ethanol, hot-dry-rock geothermal power, and marine energy.[156] These technologies are not yet widely demonstrated or have limited commercialization. Many are on the horizon and may have potential comparable to other renewable energy technologies, but still depend on attracting sufficient attention and research, development and demonstration (RD&D) funding.[156]
Wind-to-rotor efficiency (including rotor blade friction and drag) are among the factors impacting the final price of wind power.[16] Further inefficiencies, such as gearbox losses, generator and converter losses, reduce the power delivered by a wind turbine. To protect components from undue wear, extracted power is held constant above the rated operating speed as theoretical power increases at the cube of wind speed, further reducing theoretical efficiency. In 2001, commercial utility-connected turbines deliver 75% to 80% of the Betz limit of power extractable from the wind, at rated operating speed.[17][18][needs update]
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]

The trouble with rated power is that it does not tell you anything about energy production. Your utility company charges you for the energy you consume, not power. Likewise, for a small wind  turbine you should be interested in the energy it will produce, for your particular site, with your particular annual average wind speed. Rated power of the turbine does not do that. To find out about energy production take a look at the tables presented earlier.
Wind power is widely used in Europe, China, and the United States. From 2004 to 2014, worldwide installed capacity of wind power has been growing from 47 GW to 369 GW—a more than sevenfold increase within 10 years with 2014 breaking a new record in global installations (51 GW). As of the end of 2014, China, the United States and Germany combined accounted for half of total global capacity.[83] Several other countries have achieved relatively high levels of wind power penetration, such as 21% of stationary electricity production in Denmark, 18% in Portugal, 16% in Spain, and 14% in Ireland in 2010 and have since continued to expand their installed capacity.[105][106] More than 80 countries around the world are using wind power on a commercial basis.[76]

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

Within emerging economies, Brazil comes second to China in terms of clean energy investments. Supported by strong energy policies, Brazil has one of the world’s highest biomass and small-hydro power capacities and is poised for significant growth in wind energy investment. The cumulative investment potential in Brazil from 2010 to 2020 is projected as $67 billion.[155]
The combination of wind and solar PV has the advantage that the two sources complement each other because the peak operating times for each system occur at different times of the day and year. The power generation of such solar hybrid power systems is therefore more constant and fluctuates less than each of the two component subsystems.[21] Solar power is seasonal, particularly in northern/southern climates, away from the equator, suggesting a need for long term seasonal storage in a medium such as hydrogen or pumped hydroelectric.[117] The Institute for Solar Energy Supply Technology of the University of Kassel pilot-tested a combined power plant linking solar, wind, biogas and hydrostorage to provide load-following power from renewable sources.[118]
When power flows from the generator to your house, electrons get mixed together on the wires. You can't specify which electrons you get, but you can make sure that your money goes to support clean, sustainable  generators, which has the effect of making the whole system "greener". To do this, you will need to look closely at utility marketing claims and materials. To ensure that the claims are truthful, many states now require disclosure labels, just like the nutrition labels on food packages. But don't hesitate to ask for more information directly from potential suppliers, including the percentage of power derived from each fuel source and the level of each of the above emissions compared with the regional average.
The primary obstacle that is preventing the large scale implementation of solar powered energy generation is the inefficiency of current solar technology. Currently, photovoltaic (PV) panels only have the ability to convert around 24% of the sunlight that hits them into electricity.[125] At this rate, solar energy still holds many challenges for widespread implementation, but steady progress has been made in reducing manufacturing cost and increasing photovoltaic efficiency. Both Sandia National Laboratories and the National Renewable Energy Laboratory (NREL), have heavily funded solar research programs. The NREL solar program has a budget of around $75 million [126] and develops research projects in the areas of photovoltaic (PV) technology, solar thermal energy, and solar radiation.[127] The budget for Sandia’s solar division is unknown, however it accounts for a significant percentage of the laboratory’s $2.4 billion budget.[128] 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 by using it to produce hydrogen fuel from water.[129] Such research is targeted at addressing the obstacle that solar development 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 prototype converts 33.9% of the sunlight that hits it to electricity, more than double the previous high-end conversion rate.[130] Major projects on artificial photosynthesis or solar fuels are also under way in many developed nations.[131]

Biofuels include a wide range of fuels which are derived from biomass. The term covers solid, liquid, and gaseous fuels.[73] Liquid biofuels include bioalcohols, such as bioethanol, and oils, such as biodiesel. Gaseous biofuels include biogas, landfill gas and synthetic gas. Bioethanol is an alcohol made by fermenting the sugar components of plant materials and it is made mostly from sugar and starch crops. These include maize, sugarcane and, more recently, sweet sorghum. The latter crop is particularly suitable for growing in dryland conditions, and is being investigated by International Crops Research Institute for the Semi-Arid Tropics for its potential to provide fuel, along with food and animal feed, in arid parts of Asia and Africa.[74]
Although many older thermoelectric power plants with once-through cooling or cooling ponds use more water than CSP, meaning that more water passes through their systems, most of the cooling water returns to the water body available for other uses, and they consume less water by evaporation. For instance, the median coal power plant in the US with once-through cooling uses 36,350 gal/MWhr, but only 250 gal/MWhr (less than one percent) is lost through evaporation.[139] Since the 1970s, the majority of US power plants have used recirculating systems such as cooling towers rather than once-through systems.[140]
Most small wind turbines do not perform quite as well as their manufacturers want you to believe. That should come as no surprise at this point. What may be surprising is that even the turbines of the more honourable manufacturers that are honest about performance fall short, more often than not. The likely cause is turbulence and improper site selection.
Other renewable energy technologies are still under development, and include cellulosic ethanol, hot-dry-rock geothermal power, and marine energy.[156] These technologies are not yet widely demonstrated or have limited commercialization. Many are on the horizon and may have potential comparable to other renewable energy technologies, but still depend on attracting sufficient attention and research, development and demonstration (RD&D) funding.[156]
The stiffness of composites is determined by the stiffness of fibers and their volume content. Typically, E-glass fibers are used as main reinforcement in the composites. Typically, the glass/epoxy composites for wind blades contain up to 75 weight % glass. This increases the stiffness, tensile and compression strength. A promising source of the composite materials in the future is glass fibers with modified compositions like S-glass, R-glass etc. Some other special glasses developed by Owens Corning are ECRGLAS, Advantex and most recently WindStrand glass fibers. [49]
“California Looks to Stationary Energy Storage as a Solution to Peaker Plants” • Central California electric utility Pacific Gas & Electric is planning to replace three old natural gas power plants in its network with stationary energy storage installations from Tesla. California is looking to add 1.3 GW of storage to its power grid by 2020. [CleanTechnica]
Geothermal energy is produced by tapping into the thermal energy created and stored within the earth. It arises from the radioactive decay of an isotope of potassium and other elements found in the Earth's crust.[144] Geothermal energy can be obtained by drilling into the ground, very similar to oil exploration, and then it is carried by a heat-transfer fluid (e.g. water, brine or steam).[144] Geothermal systems that are mainly dominated by water have the potential to provide greater benefits to the system and will generate more power.[145] Within these liquid-dominated systems, there are possible concerns of subsidence and contamination of ground-water resources. Therefore, protection of ground-water resources is necessary in these systems. This means that careful reservoir production and engineering is necessary in liquid-dominated geothermal reservoir systems.[145] Geothermal energy is considered sustainable because that thermal energy is constantly replenished.[146] However, the science of geothermal energy generation is still young and developing economic viability. Several entities, such as the National Renewable Energy Laboratory[147] and Sandia National Laboratories[148] are conducting research toward the goal 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 development research.[149]
Today that initiative, the Green Climate Fund, is an “empty shell,” Mr. Ban said in a recent phone interview. The lifelong diplomat — who recently assumed the presidency of the Global Green Growth Institute, an international organization based in Seoul, South Korea, that focuses on clean energy development — said he hoped to use the next chapter of his career to help poor countries meet their goals under the Paris agreement on climate change.

Solar electricity is inherently variable and predictable by time of day, location, and seasons. In addition solar is intermittent due to day/night cycles and unpredictable weather. How much of a special challenge solar power is in any given electric utility varies significantly. In a summer peak utility, solar is well matched to daytime cooling demands. In winter peak utilities, solar displaces other forms of generation, reducing their capacity factors.
The world of small wind turbines is much like the wild-west of a century ago: Anything goes, and no claim is too bold. Wind turbine manufacturers will even routinely make claims that are not supported by the Laws of Physics. Energy production claims are often exaggerated, as are power curves. In fact, this is the rule, not the exception. Those manufacturers that tell the truth are the exception. Many manufacturers have never tested their wind turbines under real-world conditions. Some have never tested their turbine before selling it to unsuspecting customers. We are not joking! Because we sell grid-tie inverters for small wind turbines we have a front-row seat when it comes to actual operation of turbines of many makes and models. It turns out that some do not work; they self-destruct within days, and sometimes run away and blow their inverter within seconds after being turned onfor  the first time (clearly nobody at the factory bothered to ever test it).
The Nomad 20 Solar Panel combines highly efficient The Nomad 20 Solar Panel combines highly efficient monocrystalline technology in a foldable portable plug-and-play form. With a built-in junction box and innovative smart chip the Nomad 20 can directly charge handheld USB and 12-Volt devices directly from the sun just as fast as the wall. Combine the Nomad 20 ...  More + Product Details Close
“Volkswagen Converting Zwickau Automotive Plant to Produce Electric Vehicles” • In a move that it believes is the first of its kind in the world for a major car factory, VW is converting its auto factory in Zwickau, Germany from internal combustion vehicle production to manufacture of electric vehicles. The plant makes 330,000 cars per year. [CleanTechnica]
Micro-hydro configured into mini-grids also provide power. Over 44 million households use biogas made in household-scale digesters for lighting and/or cooking, and more than 166 million households rely on a new generation of more-efficient biomass cookstoves.[26] Clean liquid fuel sourced from renewable feedstocks are used for cooking and lighting in energy-poor areas of the developing world. Alcohol fuels (ethanol and methanol) can be produced sustainably from non-food sugary, starchy, and cellulostic feedstocks. Project Gaia, Inc. and CleanStar Mozambique are implementing clean cooking programs with liquid ethanol stoves in Ethiopia, Kenya, Nigeria and Mozambique.[139]
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]
Thirty years ago Bergey pioneered the radically-simple “Bergey design” that has proven to provide the best reliability, performance, service life, and value of all of the hundreds of competitive products that have come and gone in that time. With only three moving parts and no scheduled maintenance necessary, the Bergey 10 kW has compiled a service record that no other wind turbine can match. We back it up with the longest warranty in the industry.
The market for renewable energy technologies has continued to grow. Climate change concerns and increasing in green jobs, coupled with high oil prices, peak oil, oil wars, oil spills, promotion of electric vehicles and renewable electricity, nuclear disasters and increasing government support, are driving increasing renewable energy legislation, incentives and commercialization.[10] New government spending, regulation and policies helped the industry weather the 2009 economic crisis better than many other sectors.[24][197]
A high-capacity light-weight portable power source for juicing A high-capacity light-weight portable power source for juicing up your personal and household electronic devices power tools appliances and more. Whether you're you an outdoor enthusiast/field professional operating in off-the-grid locations or a home-owner worried about power outages the Bayoutech Mobile Power is your perfect solution that charges up on-the-go ...  More + Product Details Close
Subsequently, Spain, Italy, Greece—that enjoyed an early success with domestic solar-thermal installations for hot water needs—and France introduced feed-in tariffs. None have replicated the programmed decrease of FIT in new contracts though, making the German incentive relatively less and less attractive compared to other countries. The French and Greek FIT offer a high premium (EUR 0.55/kWh) for building integrated systems. California, Greece, France and Italy have 30–50% more insolation than Germany making them financially more attractive. The Greek domestic "solar roof" programme (adopted in June 2009 for installations up to 10 kW) has internal rates of return of 10–15% at current commercial installation costs, which, furthermore, is tax free.
The conversion of the rotational mechanical power generated by the rotor blades (known as the prime mover) into useful electrical power for use in domestic power and lighting applications or to charge batteries can be accomplished by any one of the following major types of rotational electrical machines commonly used in a wind power generating systems:
Wind power first appeared in Europe during the Middle Ages. The first historical records of their use in England date to the 11th or 12th centuries and there are reports of German crusaders taking their windmill-making skills to Syria around 1190.[6] By the 14th century, Dutch windmills were in use to drain areas of the Rhine delta. Advanced wind turbines were described by Croatian inventor Fausto Veranzio. In his book Machinae Novae (1595) he described vertical axis wind turbines with curved or V-shaped blades.
With investment subsidies, the financial burden falls upon the taxpayer, while with feed-in tariffs the extra cost is distributed across the utilities' customer bases. While the investment subsidy may be simpler to administer, the main argument in favour of feed-in tariffs is the encouragement of quality. Investment subsidies are paid out as a function of the nameplate capacity of the installed system and are independent of its actual power yield over time, thus rewarding the overstatement of power and tolerating poor durability and maintenance. Some electric companies offer rebates to their customers, such as Austin Energy in Texas, which offers $2.50/watt installed up to $15,000.[96]
Additions of small amount (0.5 weight %) of nanoreinforcement (carbon nanotubes or nanoclay in the polymer matrix of composites, fiber sizing or interlaminar layers can allow to increase the fatigue resistance, shear or compressive strength as well as fracture toughness of the composites by 30–80%. Research has also shown that the incorporation of small amount of carbon nanotubes/CNT can increase the lifetime up to 1500%.
In 2011, the International Energy Agency said that "the development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits. It will increase countries' energy security through reliance on an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments; they must be wisely spent and need to be widely shared".[49] Italy has the largest proportion of solar electricity in the world, in 2015 solar supplied 7.8% of electricity demand in Italy.[54] In 2016, after another year of rapid growth, solar generated 1.3% of global power.[55]
Solar power - The most prevalent type of renewable energy, solar power is typically produced using photovoltaic cells, which capture sunlight and turn it into electricity. Solar energy is also used to heat buildings and water, provide natural lighting and cook food. Solar technologies have become inexpensive enough to power everything from small hand-held gadgets to entire neighborhoods.

The incentive to use 100% renewable energy, for electricity, transport, or even total primary energy supply globally, has been motivated by global warming and other ecological as well as economic concerns. The Intergovernmental Panel on Climate Change has said that there are few fundamental technological limits to integrating a portfolio of renewable energy technologies to meet most of total global energy demand. Renewable energy use has grown much faster than even advocates anticipated.[148] At the national level, at least 30 nations around the world already have renewable energy contributing more than 20% of energy supply. Also, Professors S. Pacala and Robert H. Socolow have developed a series of "stabilization wedges" that can allow us to maintain our quality of life while avoiding catastrophic climate change, and "renewable energy sources," in aggregate, constitute the largest number of their "wedges".[149]
The generator, which is approximately 34% of the wind turbine cost, includes the electrical generator,[38][39] the control electronics, and most likely a gear box (e.g. planetary gear box),[40] adjustable-speed drive or continuously variable transmission[41] component for converting the low-speed incoming rotation to high-speed rotation suitable for generating electricity.
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.
The Solar updraft tower is a renewable-energy power plant for generating electricity from low temperature solar heat. Sunshine heats the air beneath a very wide greenhouse-like roofed collector structure surrounding the central base of a very tall chimney tower. The resulting convection causes a hot air updraft in the tower by the chimney effect. This airflow drives wind turbines placed in the chimney updraft or around the chimney base to produce electricity. Plans for scaled-up versions of demonstration models will allow significant power generation, and may allow development of other applications, such as water extraction or distillation, and agriculture or horticulture. A more advanced version of a similarly themed technology is the Vortex engine which aims to replace large physical chimneys with a vortex of air created by a shorter, less-expensive structure.
Jump up ^ Artificial photosynthesis as a frontier technology for energy sustainability. Thomas Faunce, Stenbjorn Styring, Michael R. Wasielewski, Gary W. Brudvig, A. William Rutherford, Johannes Messinger, Adam F. Lee, Craig L. Hill, Huub deGroot, Marc Fontecave, Doug R. MacFarlane, Ben Hankamer, Daniel G. Nocera, David M. Tiede, Holger Dau, Warwick Hillier, Lianzhou Wang and Rose Amal. Energy Environ. Sci., 2013, Advance Article doi:10.1039/C3EE40534F
Infinitemall stands behind their products and is willing to bend over backwards to help the customer. I live in rural Alaska, power here is very expensive and is generated mainly by diesel generators. My family and I are constructing a grid-tied alternative energy home. Outback Inverters and charge controllers are at the heart of the system, with a total of 8KW in solar panels and 5kw in wind generators. I have also constructed a D/C generator using an old 4 wheeler motor and 2 MWS Freedom II Generals that produces an easy 3.5kw at low engine rpms. The system totals close to 20kw in all. I purchased this wind mill to replace an older wind mill that I had built a few years ago using Windy Nations PMG. When I received the wind generator, I was disappointed to find that the center hole for the shaft had not been machined. Infintemall was very helpful, they got a new turbine out to me right away, and even paid for the defective unit to be returned. All said and done, they are a great company to deal with and I would highly recommend their turbine. It is very quiet, and quite powerful.

“Volkswagen Converting Zwickau Automotive Plant to Produce Electric Vehicles” • In a move that it believes is the first of its kind in the world for a major car factory, VW is converting its auto factory in Zwickau, Germany from internal combustion vehicle production to manufacture of electric vehicles. The plant makes 330,000 cars per year. [CleanTechnica]
$Stop getting twisted!! Gold Plated Contacts Heavy 30 amp Per conductor slip ring total 90 amps....Great for even heavy 12 volt environment wind generators as used in our Hurricane XP turbines Specs ---30 amps per conductor --- 250 volts AC/DC per circuit ---2200 watts per conductor --- rpms 0-300 ---Gold Plated Contacts ---Operational Lifespan: 80,000,000 revolutions depending on temperature, rotation speed and enviroment This rotating connector will be great for the wind generator. The current can be split up in DC applications by using two conductors to cut down on the resistance. If you have application specific questions feel free to ask me before buying. Has 3 mounting holes in colar and long wires for easy installation. To International buyers: the sales price does not include customs or duties that your country may include.
The stiffness of composites is determined by the stiffness of fibers and their volume content. Typically, E-glass fibers are used as main reinforcement in the composites. Typically, the glass/epoxy composites for wind blades contain up to 75 weight % glass. This increases the stiffness, tensile and compression strength. A promising source of the composite materials in the future is glass fibers with modified compositions like S-glass, R-glass etc. Some other special glasses developed by Owens Corning are ECRGLAS, Advantex and most recently WindStrand glass fibers. [49]

There are different types of inverters for solar use (string, central, micro). If you’re hoping to install the solar PV system yourself, selecting the best inverter will require serious research and careful planning. If you work through a professional solar installer, on the other hand, the company should help take care of inverter selection for you.
Jump up ^ Noth, André (July 2008). "History of Solar Flight" (PDF). Autonomous Systems Lab. Zürich: Swiss Federal Institute of Technology. p. 3. Archived from the original (PDF) on 1 February 2012. Retrieved 8 July 2010. Günter Rochelt was the designer and builder of Solair I, a 16 m wingspan solar airplane ... 21st of August 1983 he flew in Solair I, mostly on solar energy and also thermals, during 5 hours 41 minutes.
Biomass is biological material derived from living, or recently living organisms. It most often refers to plants or plant-derived materials which are specifically called lignocellulosic biomass.[65] As an energy source, biomass can either be used directly via combustion to produce heat, or indirectly after converting it to various forms of biofuel. Conversion of biomass to biofuel can be achieved by different methods which are broadly classified into: thermal, chemical, and biochemical methods. Wood remains the largest biomass energy source today;[66] examples include forest residues – such as dead trees, branches and tree stumps –, yard clippings, wood chips and even municipal solid waste. In the second sense, biomass includes plant or animal matter that can be converted into fibers or other industrial chemicals, including biofuels. Industrial biomass can be grown from numerous types of plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum, sugarcane, bamboo,[67] and a variety of tree species, ranging from eucalyptus to oil palm (palm oil).
In the case of a “wind turbine generator”, the wind pushes directly against the blades of the turbine, which converts the linear motion of the wind into the rotary motion necessary to spin the generators rotor and the harder the wind pushes, the more electrical energy can be generated. Then it is important to have a good wind turbine blade design to extract as much energy out of the wind as possible.

Solar energy is the cleanest and most abundant renewable energy source available, and the U.S. has some of the richest solar resources in the world. Solar technologies can harness this energy for a variety of uses, including generating electricity, providing light or a comfortable interior environment, and heating water for domestic, commercial, or industrial use.

Thermal storage technologies allow heat or cold to be stored for periods of time ranging from hours or overnight to interseasonal, and can involve storage of sensible energy (i.e. by changing the temperature of a medium) or latent energy (i.e. through phase changes of a medium, such between water and slush or ice). Short-term thermal storages can be used for peak-shaving in district heating or electrical distribution systems. Kinds of renewable or alternative energy sources that can be enabled include natural energy (e.g. collected via solar-thermal collectors, or dry cooling towers used to collect winter's cold), waste energy (e.g. from HVAC equipment, industrial processes or power plants), or surplus energy (e.g. as seasonally from hydropower projects or intermittently from wind farms). The Drake Landing Solar Community (Alberta, Canada) is illustrative. borehole thermal energy storage allows the community to get 97% of its year-round heat from solar collectors on the garage roofs, which most of the heat collected in summer.[58][59] Types of storages for sensible energy include insulated tanks, borehole clusters in substrates ranging from gravel to bedrock, deep aquifers, or shallow lined pits that are insulated on top. Some types of storage are capable of storing heat or cold between opposing seasons (particularly if very large), and some storage applications require inclusion of a heat pump. Latent heat is typically stored in ice tanks or what are called phase-change materials (PCMs).

Through collaboration, smaller buyers can benefit from economies of scale, while larger buyers can continue to see cost benefits while achieving their renewable energy goals. Aggregation allows companies to procure in a mutually beneficial way with relatively little give and take. For that reason, RMI believes this marks “the beginning of a trend,” Haley said.  
Solar energy, radiant light and heat from the sun, is harnessed using a range of ever-evolving technologies such as solar heating, photovoltaics, concentrated solar power (CSP), concentrator photovoltaics (CPV), solar architecture and artificial photosynthesis.[49][50] Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air. Active solar technologies encompass solar thermal energy, using solar collectors for heating, and solar power, converting sunlight into electricity either directly using photovoltaics (PV), or indirectly using concentrated solar power (CSP).
In 2004, natural gas accounted for about 19 percent of the U.S. electricity mix. Use of natural gas is projected to increase dramatically in the next two decades if we continue on our current path, but supplies are limited and imports are increasing. Our growing reliance on natural gas combined with limited supplies makes this fuel subject to price spikes, which can have a significant impact on consumer energy costs. In addition, though natural gas is much cleaner than coal or oil, it does produce global warming emissions when burned. So, while the use of natural gas serves as a good transition to a cleaner future, it is not the ultimate solution.
Similarly, in the United States, the independent National Research Council has noted that "sufficient domestic renewable resources exist to allow renewable electricity to play a significant role in future electricity generation and thus help confront issues related to climate change, energy security, and the escalation of energy costs … Renewable energy is an attractive option because renewable resources available in the United States, taken collectively, can supply significantly greater amounts of electricity than the total current or projected domestic demand."[154]
Globally, the long-term technical potential of wind energy is believed to be five times total current global energy production, or 40 times current electricity demand, assuming all practical barriers needed were overcome. This would require wind turbines to be installed over large areas, particularly in areas of higher wind resources, such as offshore. As offshore wind speeds average ~90% greater than that of land, so offshore resources can contribute substantially more energy than land stationed turbines.[44] In 2014 global wind generation was 706 terawatt-hours or 3% of the worlds total electricity.[45]
Similarly, in the United States, the independent National Research Council has noted that "sufficient domestic renewable resources exist to allow renewable electricity to play a significant role in future electricity generation and thus help confront issues related to climate change, energy security, and the escalation of energy costs … Renewable energy is an attractive option because renewable resources available in the United States, taken collectively, can supply significantly greater amounts of electricity than the total current or projected domestic demand."[154]
Biomass, biogas and biofuels are burned to produce heat/power and in doing so harm the environment. Pollutants such as sulphurous oxides (SOx), nitrous oxides (NOx), and particulate matter (PM) are produced from this combustion; the World Health Organisation estimates that 7 million premature deaths are caused each year by air pollution.[102] Biomass combustion is a major contributor.[102][103][104]
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]

The first three are active solar systems, which use mechanical or electrical devices that convert the sun's heat or light to another form of usable energy. Passive solar buildings are designed and oriented to collect, store, and distribute the heat energy from sunlight to maintain the comfort of the occupants without the use of moving parts or electronics.


Taken together, the generation and distribution of electric power in the United States is an astonishingly complex undertaking. Utilities may generate their own power or buy it from other utilities; that power travels over a grid of transformers and high- and low-voltage lines to your house. Ownership of utilities varies from nonprofits to cooperatives to for-profits. Federal regulators ultimately oversee the grid. Amazingly, when you flip a switch, electricity is there.
The windwheel of Hero of Alexandria (10 AD – 70 AD) marks one of the first recorded instances of wind powering a machine in history.[2][3] However, the first known practical wind power plants were built in Sistan, an Eastern province of Persia (now Iran), from the 7th century. These "Panemone" were vertical axle windmills, which had long vertical drive shafts with rectangular blades.[4] Made of six to twelve sails covered in reed matting or cloth material, these windmills were used to grind grain or draw up water, and were used in the gristmilling and sugarcane industries.[5]
Research is also undertaken in this field of artificial photosynthesis. It involves the use of nanotechnology to store solar electromagnetic energy in chemical bonds, by splitting water to produce hydrogen fuel or then combining with carbon dioxide to make biopolymers such as methanol. Many large national and regional research projects on artificial photosynthesis are now trying to develop techniques integrating improved light capture, quantum coherence methods of electron transfer and cheap catalytic materials that operate under a variety of atmospheric conditions.[119] Senior researchers in the field have made the public policy case for a Global Project on Artificial Photosynthesis to address critical energy security and environmental sustainability issues.[120]
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