The time will arrive when the industry of Europe will cease to find those natural resources, so necessary for it. Petroleum springs and coal mines are not inexhaustible but are rapidly diminishing in many places. Will man, then, return to the power of water and wind? Or will he emigrate where the most powerful source of heat sends its rays to all? History will show what will come.[35]
Above this rated speed, the wind loads on the rotor blades will be approaching the maximum strength of the electrical machine, and the generator will be producing its maximum or rated power output as the rated wind speed window will have been reached. If the wind speed continues to increase, the wind turbine generator would stop at its cut-out point to prevent mechanical and electrical damage, resulting in zero electrical generation. The application of a brake to stop the generator for damaging itself can be either a mechanical governor or electrical speed sensor.

The International Renewable Energy Agency (IRENA) is an intergovernmental organization for promoting the adoption of renewable energy worldwide. It aims to provide concrete policy advice and facilitate capacity building and technology transfer. IRENA was formed on 26 January 2009, by 75 countries signing the charter of IRENA.[145] As of March 2010, IRENA has 143 member states who all are considered as founding members, of which 14 have also ratified the statute.[146]
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.
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]
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]

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]
With feed-in tariffs, the financial burden falls upon the consumer. They reward the number of kilowatt-hours produced over a long period of time, but because the rate is set by the authorities, it may result in perceived overpayment. The price paid per kilowatt-hour under a feed-in tariff exceeds the price of grid electricity. Net metering refers to the case where the price paid by the utility is the same as the price charged.
Wind turbines do work; put them in nice, smooth air and their energy production is quite predictable (we will get to predicting it a bit further on in this story). The honest manufacturers do not lie or exaggerate, their turbines really can work as advertised in smooth, laminar airflow. However, put that same turbine on a 40 feet tower and even if the annual average wind speed is still 5 m/s at that height, its energy production will fall far short of what you would predict for that value. How short is anybody’s guess, that is part of the point; it is impossible to predict the effect of turbulence other than that it robs the energy production potential of any wind turbine. Roof tops, or other locations on a house, make for poor turbine sites. They are usually very turbulent and on top of that their average wind speeds are usually very low.
Concentrator photovoltaics (CPV) systems employ sunlight concentrated onto photovoltaic surfaces for the purpose of electrical power production. Contrary to conventional photovoltaic systems, it uses lenses and curved mirrors to focus sunlight onto small, but highly efficient, multi-junction solar cells. Solar concentrators of all varieties may be used, and these are often mounted on a solar tracker in order to keep the focal point upon the cell as the sun moves across the sky.[147] Luminescent solar concentrators (when combined with a PV-solar cell) can also be regarded as a CPV system. Concentrated photovoltaics are useful as they can improve efficiency of PV-solar panels drastically.[148]
Second-generation technologies include solar heating and cooling, wind power, modern forms of bioenergy and solar photovoltaics. These are now entering markets as a result of research, development and demonstration (RD&D) investments since the 1980s. The initial investment was prompted by energy security concerns linked to the oil crises (1973 and 1979) of the 1970s but the continuing appeal of these renewables is due, at least in part, to environmental benefits. Many of the technologies reflect significant advancements in materials.
You should know that we at Solacity love wind turbines! Can’t get enough of ’em. Where the neighbours see life-threatening, blade-shedding, bat-and-bird killing, noise-making contraptions, we see poetry in motion. Kinetic art at its finest; combining form, movement, and function all in one. We could stare at them for hours, while contemplating the meaning of life, the universe, and everything… and have… until the beer ran out. Despite all the information presented here, we are big fans of small wind turbines. This page is about informing you, so you can make a decision based on fact and not marketing hype.
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]
In 2007, General Electric's Chief Engineer predicted grid parity without subsidies in sunny parts of the United States by around 2015; other companies predicted an earlier date:[85] the cost of solar power will be below grid parity for more than half of residential customers and 10% of commercial customers in the OECD, as long as grid electricity prices do not decrease through 2010.[81]
Geothermal power is cost effective, reliable, sustainable, and environmentally friendly,[130] but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels. As a result, geothermal power has the potential to help mitigate global warming if widely deployed in place of fossil fuels.
In October 2018, the American Council for an Energy-Efficient Economy (ACEEE) released its annual "State Energy Efficiency Scorecard." The scorecard concluded that states and electric utility companies are continuing to expand energy efficiency measures in order to meet clean energy goals. In 2017, the U.S. spent $6.6 billion in electricity efficiency programs. $1.3 billion was spent on natural gas efficiency. These programs resulted in 27.3 million megawatt hours (MWh) of electricity saved.[160]
The British Energy Savings Trust report titled “Location, location, location”: This requires some reading-between-the-lines as the Trust is rather closely aligned with the small wind industry. They looked at 57 turbines for a year, a number of them building mounted, others tower mounted, and concluded that building mounted turbines did very poorly.
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.
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 energy in the wind goes up with the cube of the wind speed. Double the wind speed and you have 2 * 2 * 2 = 8 times the energy! Sit back and let the full weight of that sink in for a moment: It means that even a small difference in annual average wind speed will make a BIG difference in how much your wind turbine will produce: Putting that turbine in a place that has just 10% more wind will net you 1.1 * 1.1 * 1.1 = 1.33 = a full 33% more energy!

On most horizontal wind turbine farms, a spacing of about 6–10 times the rotor diameter is often upheld. However, for large wind farms distances of about 15 rotor diameters should be more economical, taking into account typical wind turbine and land costs. This conclusion has been reached by research[62] conducted by Charles Meneveau of the Johns Hopkins University,[63] and Johan Meyers of Leuven University in Belgium, based on computer simulations[64] that take into account the detailed interactions among wind turbines (wakes) as well as with the entire turbulent atmospheric boundary layer.


Most installers overrate the available wind resource. The majority of small wind turbine installations underperforms their predictions, often by a wide margin. Since wind speed is the most important parameter for turbine energy production, getting that wrong has large consequences (the power in the wind goes with the cube of the wind speed, so double the wind speed and the power in it is 2 * 2 * 2 = 8x as much). You have to be realistic about your annual average wind speed.
Other cities won’t have it so easy. Take Atlanta. Residents buy energy from Georgia Power, which is owned by investors. As things stand, Atlantans have no control over how their power is generated, though that may change. In 2019, Georgia Power, by state law, has to update its energy plan. Ted Terry, director of the Georgia chapter of the Sierra Club, says the nonprofit is working with Atlanta officials to incorporate renewables, primarily solar, into the state’s plan. Developing such energy sources on a scale that can power a metro area with 5.8 million people, as in Atlanta, or 7.68 million in the San Francisco Bay Area, or 3.3 million in San Diego, will prove challenging. But it doesn’t seem impossible. In 2015, California set a goal of deriving 50 percent of its energy from renewable sources by 2030. Its three investor-owned utilities—Pacific Gas & Electric, Southern California Edison and San Diego Gas & Electric—are poised to achieve that goal just two years from now, or ten years early.
From the end of 2004, worldwide renewable energy capacity grew at rates of 10–60% annually for many technologies. In 2015 global investment in renewables rose 5% to $285.9 billion, breaking the previous record of $278.5 billion in 2011. 2015 was also the first year that saw renewables, excluding large hydro, account for the majority of all new power capacity (134 GW, making up 53.6% of the total). Of the renewables total, wind accounted for 72 GW and solar photovoltaics 56 GW; both record-breaking numbers and sharply up from 2014 figures (49 GW and 45 GW respectively). In financial terms, solar made up 56% of total new investment and wind accounted for 38%.
The heat that is used for geothermal energy can be from deep within the Earth, all the way down to Earth's core – 4,000 miles (6,400 km) down. At the core, temperatures may reach over 9,000 °F (5,000 °C). Heat conducts from the core to surrounding rock. Extremely high temperature and pressure cause some rock to melt, which is commonly known as magma. Magma convects upward since it is lighter than the solid rock. This magma then heats rock and water in the crust, sometimes up to 700 °F (371 °C).[58]
From 1978 to 1996, the National Renewable Energy Laboratory experimented with producing algae fuel in the "Aquatic Species Program."[112] A self-published article by Michael Briggs, at the University of New Hampshire Biofuels Group, offers estimates for the realistic replacement of all motor vehicle fuel with biofuels by utilizing algae that have a natural oil content greater than 50%, which Briggs suggests can be grown on algae ponds at wastewater treatment plants.[113] This oil-rich algae can then be extracted from the system and processed into biofuels, with the dried remainder further reprocessed to create ethanol. The production of algae to harvest oil for biofuels has not yet been undertaken on a commercial scale, but feasibility studies have been conducted to arrive at the above yield estimate. During the biofuel production process algae actually consumes the carbon dioxide in the air and turns it into oxygen through photosynthesis.[114] In addition to its projected high yield, algaculture— unlike food crop-based biofuels — does not entail a decrease in food production, since it requires neither farmland nor fresh water. Many companies are pursuing algae bio-reactors for various purposes, including scaling up biofuels production to commercial levels.[115][116]
Climate change and global warming concerns, coupled with high oil prices, peak oil, 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 global financial crisis better than many other sectors.[24] According to a 2011 projection by the International Energy Agency, solar power generators may produce most of the world's electricity within 50 years, reducing the emissions of greenhouse gases that harm the environment.[25]
There are numerous organizations within the academic, federal, and commercial sectors conducting large scale advanced research in the field of renewable energy. This research spans several areas of focus across the renewable energy spectrum. Most of the research is targeted at improving efficiency and increasing overall energy yields.[157] Multiple federally supported research organizations have focused on renewable energy in recent years. Two of the most prominent of these labs are Sandia National Laboratories and the National Renewable Energy Laboratory (NREL), both of which are funded by the United States Department of Energy and supported by various corporate partners.[158] Sandia has a total budget of $2.4 billion[159] while NREL has a budget of $375 million.[160]
As the section above shows, anything under 5 m/s annual average wind speed is not going to be worth-while if you want any economic benefit out of a wind turbine. Even with government incentives, you would be better off with solar for most places. Let us take this a bit further, and assume your backyard is pretty windy, a full 6 m/s (13.4 mph) annual average wind speed at 100′ height. You get a 6 kW wind turbine installed, and shell out $50,000 for that privilege. If the installer did her job properly, the turbine is spinning in nice, clean, laminar air, and it will produce around 13,000 kWh per year. You are the kind of person that wins the lottery on a regular basis, marries a beauty queen (or king), and has kids that all go to ivy-league universities; your wind turbine never breaks and you do not have to shell out a single buck for maintenance over 20 years. Now your turbine has produced around 260,000 kWh of electricity, which works out to 19.2 cents per kWh in cost. Maybe you pay more than for electricity and it is worth it, but your are likely not getting rich, and any repairs and maintenance will drive that price up in a hurry.
A 1.5 (MW) wind turbine of a type frequently seen in the United States has a tower 80 meters (260 ft) high. The rotor assembly (blades and hub) weighs 22,000 kilograms (48,000 lb). The nacelle, which contains the generator, weighs 52,000 kilograms (115,000 lb). The concrete base for the tower is constructed using 26,000 kilograms (58,000 lb) reinforcing steel and contains 190 cubic meters (250 cu yd) of concrete. The base is 15 meters (50 ft) in diameter and 2.4 meters (8 ft) thick near the center.[43]
Wind turbines are manufactured in a wide range of vertical and horizontal axis. The smallest turbines are used for applications such as battery charging for auxiliary power for boats or caravans or to power traffic warning signs. Slightly larger turbines can be used for making contributions to a domestic power supply while selling unused power back to the utility supplier via the electrical grid. Arrays of large turbines, known as wind farms, are becoming an increasingly important source of intermittent renewable energy and are used by many countries as part of a strategy to reduce their reliance on fossil fuels. One assessment claimed that, as of 2009, wind had the "lowest relative greenhouse gas emissions, the least water consumption demands and... the most favourable social impacts" compared to photovoltaic, hydro, geothermal, coal and gas.[1]
Also, the output voltage and power demand depends entirely upon the appliances you have and how you wish to use them. In addition, the location of the wind turbine generator, would the wind resource keep it constantly rotating for long periods of time or would the generator speed and therefore its output vary up and down with variations in the available wind.
These high strength magnets are usually made from rare earth materials such as neodymium iron (NdFe), or samarium cobalt (SmCo) eliminating the need for the field windings to provide a constant magnetic field, leading to a simpler, more rugged construction. Wound field windings have the advantage of matching their magnetism (and therefore power) with the varying wind speed but require an external energy source to generate the required magnetic field.
Renewable energy, after its generation, needs to be stored in a medium for use with autonomous devices as well as vehicles. Also, to provide household electricity in remote areas (that is areas which are not connected to the mains electricity grid), energy storage is required for use with renewable energy. Energy generation and consumption systems used in the latter case are usually stand-alone power systems.
Compact Linear Fresnel Reflectors are CSP-plants which use many thin mirror strips instead of parabolic mirrors to concentrate sunlight onto two tubes with working fluid. This has the advantage that flat mirrors can be used which are much cheaper than parabolic mirrors, and that more reflectors can be placed in the same amount of space, allowing more of the available sunlight to be used. Concentrating linear fresnel reflectors can be used in either large or more compact plants.[16][17]
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