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.[99] 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;[100] 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,[101] and a variety of tree species, ranging from eucalyptus to oil palm (palm oil).
The International Geothermal Association (IGA) has reported that 10,715 MW of geothermal power in 24 countries is online, which is expected to generate 67,246 GWh of electricity in 2010.[131] This represents a 20% increase in geothermal power online capacity since 2005. IGA projects this will grow to 18,500 MW by 2015, due to the large number of projects presently under consideration, often in areas previously assumed to have little exploitable resource.[131]

A Darrieus type vertical axis wind turbine (the egg-beater type) can in theory work almost as good as a horizontal axis turbine. Actual measurement of one of the better designs out there, the UGE VisionAir5, does not bear that out though: It measures in at a pitiful 11% efficiency at 11 m/s wind speed, while a Bergey Excel-6 HAWT clocks in at 22% efficiency for that same wind speed, twice as much. You can read about it in Paul Gipe’s article.  Besides efficiency issues, a Darrieus VAWT unfortunately has a number of inherent issues that put them at a disadvantage: Since they are usually tall and relatively narrow structures the bending forces on their main bearing (at the bottom) are very large. There are similar issues with the forces on the blades. This means that to make a reliable vertical axis turbine takes more material, and more expensive materials, in comparison to a horizontal type turbine. For comparison, that same UGE VisionAir5 weighs 756 kg vs. the Bergey Excel-6 at 350 kg. Keep in mind that the UGE turbine only sweeps about half the area of the Bergey, the latter is a much larger turbine! This makes VAWTs inherently more expensive, or less reliable, or both.
A more recent concept for improving our electrical grid is to beam microwaves from Earth-orbiting satellites or the moon to directly when and where there is demand. The power would be generated from solar energy captured on the lunar surface In this system, the receivers would be "broad, translucent tent-like structures that would receive microwaves and convert them to electricity". NASA said in 2000 that the technology was worth pursuing but it is still too soon to say if the technology will be cost-effective.[77]

Biofuels - Rather than burning biomass to produce energy, sometimes these renewable organic materials are transformed into fuel. Notable examples include ethanol and biodiesel. Biofuels provided 2.7 percent of the world's fuels for road transport in 2010, and have the potential to meet more than 25 percent of world demand for transportation fuels by 2050.


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.
In the 1980s and early 1990s, most photovoltaic modules provided remote-area power supply, but from around 1995, industry efforts have focused increasingly on developing building integrated photovoltaics and power plants for grid connected applications (see photovoltaic power stations article for details). Currently the largest photovoltaic power plant in North America is the Nellis Solar Power Plant (15 MW).[24][25] There is a proposal to build a Solar power station in Victoria, Australia, which would be the world's largest PV power station, at 154 MW.[26][27] Other large photovoltaic power stations include the Girassol solar power plant (62 MW),[28] and the Waldpolenz Solar Park (40 MW).[29]
My system has been installed for about a year now. When I first contracted with Envismart, the sales rep was very available and eager to help with my questions but after the installation, he was very hard to make contact with, seldom returned my calls, and when he did seemed to tell me what he thought I wanted hear and very seldom followed through. The system had a shaky start, it died after one day and after two new inverters and several optimizers over several months of on again, off again operation it seems to be running smoothly, at least for the last few months. Customer support was not very good, to be kind, but the service personnel that came out were prompt and there when they said they would be and very open about what the problems were and quickly fixed them. I was told my recurring system problems were a little unusual and I have to take their word on that but they gave me their personnel cell numbers and told me to call them when I couldn't get Customer Support to call - and when I called them, they came through and got me serviced a lot more quickly. They are the main reason I rated the company a 3.I have to say, the last month or so, it seems like the company is starting to work on changing its image. I have been called on several occasions by the "Quality Assurance" group at their initiation and asked if everything was OK with my system and I usually had an issue about something (admittedly, sometimes very minor). They always followed through with answers and corrected my concerns which was a big change from my previous experiences. I want to encourage them to continue improving their Customer Support after the sale in this manner as that is the real reputation for their company. I am still reserving my opinion but I am very much encouraged by their recent efforts - Keep it up!... read more
Even if you can’t directly purchase and install a solar system because you rent your home, have inadequate solar resources, or lack financing, you may still benefit from switching to solar electricity, and there numerous business models that make solar easier, cheaper, and more accessible. Options such as community or shared solar programs, solar leases, and power-purchase agreements allow millions of households to take advantage of solar energy. Learn about the various ways you can go solar.
The use of a gearbox allows for better matching of the generator speed to that of the turbine but the disadvantage of using a gearbox is that as a mechanical component it is subjected to wear and tear reducing the efficiency of the system. Direct drive however may be more simple and efficient, but the generators rotor shaft and bearings are subjected to the full weight and rotational force of the rotor blades.
If you do install an anemometer and measure the wind over one or more years, you should compare the annual average wind speed obtained from your anemometer data to the annual average of the nearest airport or meteo-station for that same year. This will tell you if your site is more or less windy than that airport or meteo-station, and by how much. Then compare that year’s data  to the long-term annual average wind speed, and you will know what to expect over the long term, corrected for your particular site. It will not be exact, but it will make your short-term anemometer data much more useful.
Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. One advantage of this arrangement is that the turbine does not need to be pointed into the wind to be effective, which is an advantage on a site where the wind direction is highly variable. It is also an advantage when the turbine is integrated into a building because it is inherently less steerable. Also, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, improving accessibility for maintenance. However, these designs produce much less energy averaged over time, which is a major drawback.[24][27]
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]
A few localities have exploited the attention-getting nature of wind turbines by placing them on public display, either with visitor centers around their bases, or with viewing areas farther away.[59] The wind turbines are generally of conventional horizontal-axis, three-bladed design, and generate power to feed electrical grids, but they also serve the unconventional roles of technology demonstration, public relations, and education.

Al Gore says the reason is innovation. “The cost-reduction curve that came to technologies like computers, smartphones and flat-panel televisions has come to solar energy, wind energy and battery storage,” he says. “I remember being startled decades ago when people first started to explain to me that the cost of computing was being cut in half every 18 to 24 months. And now this dramatic economic change has begun to utterly transform the electricity markets.”

A wind turbine is made up of two major components and having looked at one of them, the rotor blade design in the previous tutorial, we can now look at the other, the Wind Turbine Generator or WTG’s which is the electrical machine used to generate the electricity. A low rpm electrical generator is used for converting the mechanical rotational power produced by the winds energy into usable electricity to supply our homes and is at the heart of any wind power system.

He was able to begin installation sooner than promised. The finished product looks great. The exterior industrial grade electrical work they did looks stylish. The workers kept a clean job site and fully cleaned up, leaving my place neater than before they began. The workers were knowledgeable and helpful. Other than wishing that it was free, I don't know what they could have done better. I give them my highest recommendation because of a job superbly done.... read more

Green energy, however, utilizes energy sources that are readily available all over the world, including in rural and remote areas that don't otherwise have access to electricity. Advances in renewable energy technologies have lowered the cost of solar panels, wind turbines and other sources of green energy, placing the ability to produce electricity in the hands of the people rather than those of oil, gas, coal and utility companies.


“Five New State Governors Aim for 100% Renewables” • Five governors-elect in Colorado, Illinois, Nevada, Connecticut, and Maine, states with a combined population of 26 million, put forth campaign goals of 100% renewable electricity. Currently, only California and Hawaii have a deadline to move to 100% zero-carbon electricity. [pv magazine International]
Nearly all the gasoline sold in the United States today is mixed with 10% ethanol,[128] and motor vehicle manufacturers already produce vehicles designed to run on much higher ethanol blends. Ford, Daimler AG, and GM are among the automobile companies that sell "flexible-fuel" cars, trucks, and minivans that can use gasoline and ethanol blends ranging from pure gasoline up to 85% ethanol. By mid-2006, there were approximately 6 million ethanol compatible vehicles on U.S. roads.[129]
The solar thermal power industry is growing rapidly with 1.3 GW under construction in 2012 and more planned. Spain is the epicenter of solar thermal power development with 873 MW under construction, and a further 271 MW under development.[112] In the United States, 5,600 MW of solar thermal power projects have been announced.[113] Several power plants have been constructed in the Mojave Desert, Southwestern United States. The Ivanpah Solar Power Facility being the most recent. In developing countries, three World Bank projects for integrated solar thermal/combined-cycle gas-turbine power plants in Egypt, Mexico, and Morocco have been approved.[114]
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.
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.
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).
Many residential PV systems are connected to the grid wherever available, especially in developed countries with large markets.[10] In these grid-connected PV systems, use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such stand-alone power systems permit operations at night and at other times of limited sunlight.
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