A more reliable grid: Even if we're not ready to completely transition to renewable energy sources of power, supplementing the grid with green electricity helps increase grid reliability. You can also produce your own green electricity by installing solar panels or wind turbines at home. If the grid goes down for some reason, you may be able to keep your power on using your on-site renewable power generation system.
The US National Renewable Energy Laboratory (NREL), in harmonizing the disparate estimates of life-cycle GHG emissions for solar PV, found that the most critical parameter was the solar insolation of the site: GHG emissions factors for PV solar are inversely proportional to insolation.[125] For a site with insolation of 1700 kWh/m2/year, typical of southern Europe, NREL researchers estimated GHG emissions of 45 gCO2e/kWh. Using the same assumptions, at Phoenix, USA, with insolation of 2400 kWh/m2/year, the GHG emissions factor would be reduced to 32 g of CO2e/kWh.[126]
A report by the United States Geological Survey estimated the projected materials requirement in order to fulfill the US commitment to supplying 20% of its electricity from wind power by 2030. They did not address requirements for small turbines or offshore turbines since those were not widely deployed in 2008, when the study was created. They found that there are increases in common materials such as cast iron, steel and concrete that represent 2–3% of the material consumption in 2008. Between 110,000 and 115,000 metric tons of fiber glass would be required annually, equivalent to 14% of consumption in 2008. They did not see a high increase in demand for rare metals compared to available supply, however rare metals that are also being used for other technologies such as batteries which are increasing its global demand need to be taken into account. Land, whbich might not be considered a material, is an important resource in deploying wind technologies. Reaching the 2030 goal would require 50,000 square kilometers of onshore land area and 11,000 square kilometers of offshore. This is not considered a problem in the US due to its vast area and the ability to use land for farming and grazing. A greater limitation for the technology would be the variability and transmission infrastructure to areas of higher demand.[54]

Hydro-electricity and geothermal electricity produced at favourable sites are now the cheapest way to generate electricity. Renewable energy costs continue to drop, and the levelised cost of electricity (LCOE) is declining for wind power, solar photovoltaic (PV), concentrated solar power (CSP) and some biomass technologies.[100] Renewable energy is also the most economic solution for new grid-connected capacity in areas with good resources. As the cost of renewable power falls, the scope of economically viable applications increases. Renewable technologies are now often the most economic solution for new generating capacity. Where "oil-fired generation is the predominant power generation source (e.g. on islands, off-grid and in some countries) a lower-cost renewable solution almost always exists today".[100] A series of studies by the US National Renewable Energy Laboratory modeled the "grid in the Western US under a number of different scenarios where intermittent renewables accounted for 33 percent of the total power." In the models, inefficiencies in cycling the fossil fuel plants to compensate for the variation in solar and wind energy resulted in an additional cost of "between $0.47 and $1.28 to each MegaWatt hour generated"; however, the savings in the cost of the fuels saved "adds up to $7 billion, meaning the added costs are, at most, two percent of the savings."[101]

Over $1 billion of federal money has been spent on the research and development of hydrogen and a medium for energy storage in the United States.[150] Both the National Renewable Energy Laboratory[151] and Sandia National Laboratories[152] have departments dedicated to hydrogen research. Hydrogen is useful for energy storage, and for use in airplanes and ships, but is not practical for automobile use, as it is not very efficient, compared to using a battery — for the same cost a person can travel three times as far using a battery electric vehicle.[153]


In 2007, the world's first turbine to create commercial amounts of energy using tidal power was installed in the narrows of Strangford Lough in Ireland. The 1.2 MW underwater tidal electricity generator takes advantage 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 minimal environmental impact, as it is almost entirely submerged, and the rotors turn slowly enough that they pose no danger to wildlife.[48][49]

Prior to the development of coal in the mid 19th century, nearly all energy used was renewable. Almost without a doubt the oldest known use of renewable energy, in the form of traditional biomass to fuel fires, dates from 790,000 years ago. Use of biomass for fire did not become commonplace until many hundreds of thousands of years later, sometime between 200,000 and 400,000 years ago.[31] Probably the second oldest usage of renewable energy is harnessing the wind in order to drive ships over water. This practice can be traced back some 7000 years, to ships in the Persian Gulf[32] and on the Nile.[33] Moving into the time of recorded history, the primary sources of traditional renewable energy were human labor, animal power, water power, wind, in grain crushing windmills,[32] and firewood, a traditional biomass. A graph of energy use in the United States up until 1900 shows oil and natural gas with about the same importance in 1900 as wind and solar played in 2010.
Wind turbines need wind. Not just any wind, but the nicely flowing, smooth, laminar kind. That cannot be found at 30 feet height. It can usually not be found at 60 feet. Sometimes you find it at 80 feet. More often than not it takes 100 feet of tower to get there. Those towers cost as much or more, installed, as the turbine itself. How much tower you need for a wind turbine to live up to its potential depends on your particular site; on the trees and structures around it etc. Close to the ground the wind is turbulent, and makes a poor fuel for a small wind turbine.
Several large-scale energy storage suggestions for the grid have been done. Worldwide there is over 100 GW of Pumped-storage hydroelectricity. This improves efficiency and decreases energy losses but a conversion to an energy storing mains electricity grid is a very costly solution. Some costs could potentially be reduced by making use of energy storage equipment the consumer buys and not the state. An example is batteries in electric cars that would double as an energy buffer for the electricity grid. However besides the cost, setting-up such a system would still be a very complicated and difficult procedure. Also, energy storage apparatus' as car batteries are also built with materials that pose a threat to the environment (e.g. Lithium). The combined production of batteries for such a large part of the population would still have environmental concerns. Besides car batteries however, other Grid energy storage projects make use of less polluting energy carriers (e.g. compressed air tanks and flywheel energy storage).
Concentrating solar power plants with wet-cooling systems, on the other hand, have the highest water-consumption intensities of any conventional type of electric power plant; only fossil-fuel plants with carbon-capture and storage may have higher water intensities.[135] A 2013 study comparing various sources of electricity found that the median water consumption during operations of concentrating solar power plants with wet cooling was 810 ga/MWhr for power tower plants and 890 gal/MWhr for trough plants. This was higher than the operational water consumption (with cooling towers) for nuclear (720 gal/MWhr), coal (530 gal/MWhr), or natural gas (210).[134] A 2011 study by the National Renewable Energy Laboratory came to similar conclusions: for power plants with cooling towers, water consumption during operations was 865 gal/MWhr for CSP trough, 786 gal/MWhr for CSP tower, 687 gal/MWhr for coal, 672 gal/MWhr for nuclear, and 198 gal/MWhr for natural gas.[136] The Solar Energy Industries Association noted that the Nevada Solar One trough CSP plant consumes 850 gal/MWhr.[137] The issue of water consumption is heightened because CSP plants are often located in arid environments where water is scarce.

List of books about renewable energy List of countries by electricity production from renewable sources List of geothermal power stations Lists of hydroelectric power stations List of largest hydroelectric power stations List of people associated with renewable energy List of renewable energy companies by stock exchange List of renewable energy organizations List of renewable energy topics by country List of U.S. states by electricity production from renewable sources
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]
In 2007, the world's first turbine to create commercial amounts of energy using tidal power was installed in the narrows of Strangford Lough in Ireland. The 1.2 MW underwater tidal electricity generator takes advantage 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 minimal environmental impact, as it is almost entirely submerged, and the rotors turn slowly enough that they pose no danger to wildlife.[48][49]
Projections vary. The EIA has predicted that almost two thirds of net additions to power capacity will come from renewables by 2020 due to the combined policy benefits of local pollution, decarbonisation and energy diversification. Some studies have set out roadmaps to power 100% of the world’s energy with wind, hydroelectric and solar by the year 2030.
There is no energy in the wind at those wind speeds, nothing to harvest for the turbine. While it may make you feel good to see your expensive yard toy spin, it is not doing anything meaningful in a breeze like that: To give you some idea, a wind turbine with a diameter of 6 meters (pretty large as small wind turbines go) can realistically produce just 120 Watt at 3.5 m/s wind speed. That same turbine would be rated at 6 kW (or more, see the next section), so energy production at cut-in really is just a drop in the bucket. What is more, due to the way grid-tie inverters work, you are about as likely to be loosing energy around cut-in wind speed to keep the inverter powered, as you are in making any energy, resulting in a net-loss of electricity production.
For several years, worldwide growth of solar PV was driven by European deployment, but has since shifted to Asia, especially China and Japan, and to a growing number of countries and regions all over the world, including, but not limited to, Australia, Canada, Chile, India, Israel, Mexico, South Africa, South Korea, Thailand, and the United States.

If you regularly find your lawn furniture blown over, or have to collect it from the neighbour’s yard, your house needs to be repainted every year or two because it constantly gets sand-blasted, and where the trees have funny shapes (and not because your power company has been doing the pruning), that is when you know you live in a windy place where a wind turbine is likely to make economic sense.
In the next tutorial about Wind Turbine Generators we will look at DC machines and how we can use a DC Generator to produce electricity from the power of the wind. To learn more about “Wind Turbine Generators”, or obtain more wind energy information about the various wind turbine generating systems available, or to explore the advantages and disadvantages of wind energy, Click Here to get your copy of one of the top “Wind Turbine Guides” today direct from Amazon.
If you regularly find your lawn furniture blown over, or have to collect it from the neighbour’s yard, your house needs to be repainted every year or two because it constantly gets sand-blasted, and where the trees have funny shapes (and not because your power company has been doing the pruning), that is when you know you live in a windy place where a wind turbine is likely to make economic sense.
Jump up ^ Faunce, T. A.; Lubitz, W.; Rutherford, A. W. (Bill); MacFarlane, D.; Moore, G. F.; Yang, P.; Nocera, D. G; Moore, Tom A; Gregory, Duncan H; Fukuzumi, Shunichi; Yoon, Kyung B.; Armstrong, F. A.; Wasielewski, M. R.; Styring, S. (2013), "Energy and environment policy case for a global project on artificial photosynthesis", Energy & Environmental Science, 6 (3): 695–698, doi:10.1039/C3EE00063J, archived from the original on 16 August 2013
As of 2018, American electric utility companies are planning new or extra renewable energy investments. These investments are particularly aimed at solar energy, thanks to the Tax Cuts and Jobs Act of 2017 being signed into law. The law retained incentives for renewable energy development. Utility companies are taking advantage of the federal solar investment tax credit before it permanently goes down to 10% after 2021. According to the March 28 S&P Global Market Intelligence report summary, "NextEra Energy Inc., Duke Energy Corp., and Dominion Energy Inc.’s utilities are among a number of companies in the sector contemplating significant solar investments in the near-term. Other companies, including Xcel Energy Inc. and Alliant Energy Corp., are undertaking large wind projects in the near-term, but are considering ramping up solar investments in the coming years."[96]
By Ellen Coleman—As an American of non-specific cultural identity, I look with envy at families with strong cultural tradition. I wonder who "my people” are. What family traditions will my children (now grown) want to pass on to their own children?  Their exposure has been such a mixed bag of “ritual”—making tamales for Thanksgiving, potstickers for family reunions, fried eggplant for Fourth of July.  What will be their choice of comfort music?  What kinds of homes will they make, what spiritual paths will they take?

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:
By 2040, renewable energy is projected to equal coal and natural gas electricity generation. Several jurisdictions, including Denmark, Germany, the state of South Australia and some US states have achieved high integration of variable renewables. For example, in 2015 wind power met 42% of electricity demand in Denmark, 23.2% in Portugal and 15.5% in Uruguay. Interconnectors enable countries to balance electricity systems by allowing the import and export of renewable energy. Innovative hybrid systems have emerged between countries and regions.[27]
There are more specific questions you’ll have to ask yourself about your location and home—e.g., is my next-door neighbor’s oak tree going to block all my sunlight? You’ll also have to take local weather conditions into consideration. Luckily, there are plenty of other resources to help you find your solar potential. See our Tools section for more info.

A subtype of Darrieus turbine with straight, as opposed to curved, blades. The cycloturbine variety has variable pitch to reduce the torque pulsation and is self-starting.[33] The advantages of variable pitch are: high starting torque; a wide, relatively flat torque curve; a higher coefficient of performance; more efficient operation in turbulent winds; and a lower blade speed ratio which lowers blade bending stresses. Straight, V, or curved blades may be used.[34]
If you want to purchase a rooftop solar system for your home, federal tax credits and other state, local, or utility incentives can offset some of the upfront cost. There are also several financing options available for homeowners, including energy-saving mortgages, home equity, Property Assessed Clean Energy Loans, and more traditional bank loans.
A 2014-published life-cycle analysis of land use for various sources of electricity concluded that the large-scale implementation of solar and wind potentially reduces pollution-related environmental impacts. The study found that the land-use footprint, given in square meter-years per megawatt-hour (m2a/MWh), was lowest for wind, natural gas and rooftop PV, with 0.26, 0.49 and 0.59, respectively, and followed by utility-scale solar PV with 7.9. For CSP, the footprint was 9 and 14, using parabolic troughs and solar towers, respectively. The largest footprint had coal-fired power plants with 18 m2a/MWh.[146]
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.
Renewable energy variability is a problem for corporate buyers. But what is undesirable to buyers is attractive for insurance companies, whose core business revolves around managing weather-related risks. VFAs sit on top of a new or existing PPA and are effectively designed to pay the corporate buyer when they’re getting less renewable power than they contracted for, and give money to the insurer when there’s more.
The overwhelming majority of electricity produced worldwide is used immediately, since storage is usually more expensive and because traditional generators can adapt to demand. However both solar power and wind power are variable renewable energy, meaning that all available output must be taken whenever it is available by moving through transmission lines to where it can be used now. Since solar energy is not available at night, storing its energy is potentially an important issue particularly in off-grid and for future 100% renewable energy scenarios to have continuous electricity availability.[106]
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The first electricity-generating wind turbine was a battery charging machine installed in July 1887 by Scottish academic James Blyth to light his holiday home in Marykirk, Scotland.[7] Some months later American inventor Charles F. Brush was able to build the first automatically operated wind turbine after consulting local University professors and colleagues Jacob S. Gibbs and Brinsley Coleberd and successfully getting the blueprints peer-reviewed for electricity production in Cleveland, Ohio.[7] Although Blyth's turbine was considered uneconomical in the United Kingdom,[7] electricity generation by wind turbines was more cost effective in countries with widely scattered populations.[6]

Outline of energy Energy Units Conservation of energy Energetics Energy transformation Energy condition Energy transition Energy level Energy system Mass Negative mass Mass–energy equivalence Power Thermodynamics Quantum thermodynamics Laws of thermodynamics Thermodynamic system Thermodynamic state Thermodynamic potential Thermodynamic free energy Irreversible process Thermal reservoir Heat transfer Heat capacity Volume (thermodynamics) Thermodynamic equilibrium Thermal equilibrium Thermodynamic temperature Isolated system Entropy Free entropy Entropic force Negentropy Work Exergy Enthalpy
The early development of solar technologies starting in the 1860s was driven by an expectation that coal would soon become scarce. Charles Fritts installed the world's first rooftop photovoltaic solar array, using 1%-efficient selenium cells, on a New York City roof in 1884.[28] However, development of solar technologies stagnated in the early 20th century in the face of the increasing availability, economy, and utility of coal and petroleum.[29] In 1974 it was estimated that only six private homes in all of North America were entirely heated or cooled by functional solar power systems.[30] The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy policies around the world and brought renewed attention to developing solar technologies.[31][32] Deployment strategies focused on incentive programs such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Other efforts included the formation of research facilities in the United States (SERI, now NREL), Japan (NEDO), and Germany (Fraunhofer–ISE).[33] Between 1970 and 1983 installations of photovoltaic systems grew rapidly, but falling oil prices in the early 1980s moderated the growth of photovoltaics from 1984 to 1996.
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