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]

Enhanced geothermal systems (EGS) are a new type of geothermal power technologies that do not require natural convective hydrothermal resources. The vast majority of geothermal energy within drilling reach is in dry and non-porous rock.[161] EGS technologies "enhance" and/or create geothermal resources in this "hot dry rock (HDR)" through hydraulic stimulation. EGS and HDR technologies, such as hydrothermal geothermal, are expected to be baseload resources which produce power 24 hours a day like a fossil plant. Distinct from hydrothermal, HDR and EGS may be feasible anywhere in the world, depending on the economic limits of drill depth. Good locations are over deep granite covered by a thick (3–5 km) layer of insulating sediments which slow heat loss.[162] There are HDR and EGS systems currently being developed and tested in France, Australia, Japan, Germany, the U.S. and Switzerland. The largest EGS project in the world is a 25 megawatt demonstration plant currently being developed in the Cooper Basin, Australia. The Cooper Basin has the potential to generate 5,000–10,000 MW.
Green Pricing is an optional utility service for customers who want to help expand the production and distribution of renewable energy technologies. With green pricing, you do not have to change your electricity provider. Instead, customers choose to pay a premium on their electricity bill to cover the extra cost of purchasing clean, sustainable energy. As of March 2006, more than 600 utilities, electricity providers in 36 states offer a green pricing option.

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


Then I pick up a Home Power Magazine, or a Backwoods Home, or a Mother Earth News.  I read the letters to the editor and I think, These are my people!  This is my tribe—the tribe of folks striving for independence of thought and lifestyle, who are creative in their choice of building materials, who try to make responsible choices about how their choices affect the environment they live in.
The energy number that is left over should be a good approximation of what you can expect from that VAWT. Compare the resulting numbers with those mentioned in just about all sales brochures of VAWT type turbines and it should be immediately clear that their marketing people are smoking The Good Stuff. There is no relation to physical reality in their numbers, they are consistently much too high. Keep in mind that the energy production numbers calculated here are ‘best case’; for a turbine in nice, smooth air. Most VAWTs are placed very close to the ground, or on buildings, where there is little wind and lots of turbulence. Under those conditions they will do much, much worse than predicted.
Large three-bladed horizontal-axis wind turbines (HAWT), with the blades upwind of the tower produce the overwhelming majority of windpower in the world today. These turbines have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a yaw system. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.[25] Some turbines use a different type of generator suited to slower rotational speed input. These don't need a gearbox, and are called direct-drive, meaning they couple the rotor directly to the generator with no gearbox in between. While permanent magnet direct-drive generators can be more costly due to the rare earth materials required, these gearless turbines are sometimes preferred over gearbox generators because they "eliminate the gear-speed increaser, which is susceptible to significant accumulated fatigue torque loading, related reliability issues, and maintenance costs."[26]
If you can turn a wrench and operate an electric drill, you can build this simple generator in two days: one day for chasing down parts, and one day for assembling the components. The four major components include a vehicle alternator with a built-in voltage regulator, a General Motors (GM) fan and clutch assembly (I used one from a 1988 GM 350 motor), a tower or pole on which to mount the generator (15 feet of used 2-inch tubing cost me $20), and the metal to build a bracket for mounting the generator on the tower or pole. If you’re a Ford guy or a Mopar gal, that’s fine — just make sure your alternator has a built-in voltage regulator. You’ll also need some electrical cable or wires to hook the alternator up to your storage batteries. I used 8-gauge, 3-conductor cable pilfered from the oil patch. (And they said the transition from fossil fuels to renewables would take years. Pfft!)

Floating solar arrays are PV systems that float on the surface of drinking water reservoirs, quarry lakes, irrigation canals or remediation and tailing ponds. A small number of such systems exist in France, India, Japan, South Korea, the United Kingdom, Singapore and the United States.[168][169][170][171][172] The systems are said to have advantages over photovoltaics on land. The cost of land is more expensive, and there are fewer rules and regulations for structures built on bodies of water not used for recreation. Unlike most land-based solar plants, floating arrays can be unobtrusive because they are hidden from public view. They achieve higher efficiencies than PV panels on land, because water cools the panels. The panels have a special coating to prevent rust or corrosion.[173] In May 2008, the Far Niente Winery in Oakville, California, pioneered the world's first floatovoltaic system by installing 994 solar PV modules with a total capacity of 477 kW onto 130 pontoons and floating them on the winery's irrigation pond.[174] Utility-scale floating PV farms are starting to be built. Kyocera will develop the world's largest, a 13.4 MW farm on the reservoir above Yamakura Dam in Chiba Prefecture[175] using 50,000 solar panels.[176][177] Salt-water resistant floating farms are also being constructed for ocean use.[178] The largest so far announced floatovoltaic project is a 350 MW power station in the Amazon region of Brazil.[179]


A heat pump is a device that provides heat energy from a source of heat to a destination called a "heat sink". Heat pumps are designed to move thermal energy opposite to the direction of spontaneous heat flow by absorbing heat from a cold space and releasing it to a warmer one. A solar-assisted heat pump represents the integration of a heat pump and thermal solar panels in a single integrated system. Typically these two technologies are used separately (or only placing them in parallel) to produce hot water.[180] In this system the solar thermal panel performs the function of the low temperature heat source and the heat produced is used to feed the heat pump's evaporator.[181] The goal of this system is to get high COP and then produce energy in a more efficient and less expensive way.

Common battery technologies used in today's home PV systems include, the valve regulated lead-acid battery– a modified version of the conventional lead–acid battery, nickel–cadmium and lithium-ion batteries. Lead-acid batteries are currently the predominant technology used in small-scale, residential PV systems, due to their high reliability, low self discharge and investment and maintenance costs, despite shorter lifetime and lower energy density. However, lithium-ion batteries have the potential to replace lead-acid batteries in the near future, as they are being intensively developed and lower prices are expected due to economies of scale provided by large production facilities such as the Gigafactory 1. In addition, the Li-ion batteries of plug-in electric cars may serve as a future storage devices in a vehicle-to-grid system. Since most vehicles are parked an average of 95 percent of the time, their batteries could be used to let electricity flow from the car to the power lines and back. Other rechargeable batteries used for distributed PV systems include, sodium–sulfur and vanadium redox batteries, two prominent types of a molten salt and a flow battery, respectively.[114][115][116]
With Georgetown emerging as a brave new model for a renewable city, it makes sense to ask if others can achieve the same magical balance of more power, less pollution and lower costs. In fact, cities ranging from Orlando to St. Louis to San Francisco to Portland, Oregon, have pledged to run entirely on renewable energy. Those places are much larger than Georgetown, of course, and no one would expect misty Portland to power a light bulb for long with solar energy, which is crucial to Georgetown’s success. But beyond its modest size, abundant sunshine and archetype-busting mayor, Georgetown has another edge, one that’s connected to a cherished Lone Star ideal: freedom.
What is a small wind turbine? Anything under, say, 10 meters rotor diameter (30 feet) is well within the “small wind” category. That works out to wind turbines with a rated power up to around 20 kW (at 11 m/s, or 25 mph). For larger wind turbines the manufacturers are usually a little more honest, and more money is available to do a good site analysis. The information in this article is generic: The same applies to all the other brands and models, be they of the HAWT (Horizontal Axis Wind Turbine) or VAWT (Vertical Axis Wind Turbine) persuasion.
This sets sustainable energy apart from other renewable energy terminology such as alternative energy by focusing on the ability of an energy source to continue providing energy. Sustainable energy can produce some pollution of the environment, as long as it is not sufficient to prohibit heavy use of the source for an indefinite amount of time. Sustainable energy is also distinct from low-carbon energy, which is sustainable only in the sense that it does not add to the CO2 in the atmosphere.

Solar power panels that use nanotechnology, which can create circuits out of individual silicon molecules, may cost half as much as traditional photovoltaic cells, according to executives and investors involved in developing the products. Nanosolar has secured more than $100 million from investors to build a factory for nanotechnology thin-film solar panels. The company's plant has a planned production capacity of 430 megawatts peak power of solar cells per year. Commercial production started and first panels have been shipped[50] to customers in late 2007.[51]
Jump up ^ Schröder, K.-P.; Smith, R.C. (2008). "Distant future of the Sun and Earth revisited". Monthly Notices of the Royal Astronomical Society. 386 (1): 155–163. arXiv:0801.4031. Bibcode:2008MNRAS.386..155S. doi:10.1111/j.1365-2966.2008.13022.x. See also Palmer, J. (2008). "Hope dims that Earth will survive Sun's death". New Scientist. Retrieved 24 March 2008.
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.
Green Energy Corp’s GreenBus® software interoperability platform enables the adoption of evolving Smart Grid technologies and integration with legacy power and communications infrastructures. Microgrid developers can now design and implement an architecture that supports advanced technology adoption over time, while realizing the business benefits incrementally.

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]


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]
Because one obstacle to adopting wind and solar power is reliability—what happens on calm, cloudy days?—recent improvements in energy-storage technology, a.k.a. batteries, are helping accelerate adoption of renewables. Last May, for example, Tucson Electric Power signed a deal for solar energy with storage, which can mitigate (if not entirely resolve) concerns about how to provide power on gray days. The storage upped the energy cost by $15 per megawatt hour. By the end of the year, the Public Service Company of Colorado had been quoted a storage fee that increased the cost of a megawatt hour by only $3 to $7, a drop of more than 50 percent. In a landmark achievement, Tesla installed the world’s largest lithium-ion battery in South Australia last December, to store wind-generated power. But by then Hyundai Electric was at work in the South Korean metropolis of Ulsan on a battery that was 50 percent bigger.
You have read this far, and still want to install a wind turbine? Then it is time for a reality check: Most (some would say all) installed small wind turbines do abysmally poor in comparison with their energy production numbers as calculated above. That is the message from a number of studies, usually on behalf of governments that subsidize wind turbines. Do not just take our word for this, read it for yourself:
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Adam Schultz, a senior policy analyst for the Oregon Department of Energy, says he’s more encouraged than ever about the prospects for renewables. Because the Pacific Northwest features large-scale hydropower plants built as part of the New Deal, energy already tends to be less expensive there than the U.S. average. But solar and wind power have “gotten cheaper over the last couple years to the point that I can’t even tell you what the costs are because costs have been dropping so rapidly,” Schultz says. “We have enough sunshine,” he says (presumably referring to the eastern part of the state), “so it’s just a matter of time.”
Besides getting a working product, the one measure you are after as a small wind turbine owner is how much electrical energy it will produce for your location. Hopefully by now you know the annual average wind speed for the height that you are planning to put your turbine at, and you have selected a site with little turbulence. Forget about the manufacturer’s claims; it turns out that the best predictors for turbine energy production are the diameter and average wind speed. Here is an equation that will calculate approximate annual average energy production for a grid-tie horizontal axis turbine of reasonable efficiency:
A wide range of concentrating technologies exists: among the best known are the parabolic trough, the compact linear Fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the sun and focus light. In all of these systems a working fluid is heated by the concentrated sunlight, and is then used for power generation or energy storage.[11] Thermal storage efficiently allows up to 24-hour electricity generation.[12]
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