Low Temperature Geothermal[29] refers to the use of the outer crust of the earth as a Thermal Battery to facilitate Renewable thermal energy for heating and cooling buildings, and other refrigeration and industrial uses. In this form of Geothermal, a Geothermal Heat Pump and Ground-coupled heat exchanger are used together to move heat energy into the earth (for cooling) and out of the earth (for heating) on a varying seasonal basis. Low temperature Geothermal (generally referred to as "GHP") is an increasingly important renewable technology because it both reduces total annual energy loads associated with heating and cooling, and it also flattens the electric demand curve eliminating the extreme summer and winter peak electric supply requirements. Thus Low Temperature Geothermal/GHP is becoming an increasing national priority with multiple tax credit support[60] and focus as part of the ongoing movement toward Net Zero Energy.[61][30] New York City has even just passed a law[62] to require GHP anytime is shown to be economical with 20 year financing including the Socialized Cost of Carbon.[63][64]
For either photovoltaic or thermal systems, one option is to loft them into space, particularly Geosynchronous orbit. To be competitive with Earth-based solar power systems, the specific mass (kg/kW) times the cost to loft mass plus the cost of the parts needs to be $2400 or less. I.e., for a parts cost plus rectenna of $1100/kW, the product of the $/kg and kg/kW must be $1300/kW or less.[190] Thus for 6.5 kg/kW, the transport cost cannot exceed $200/kg. While that will require a 100 to one reduction, SpaceX is targeting a ten to one reduction, Reaction Engines may make a 100 to one reduction possible.
Dale Ross, the mayor of Georgetown, Texas, has a big smile, a big handshake and a big personality. In last year’s election, he won big, with 72 percent of the vote. The key to his success? “Without being too self-reflective,” he says, “I just like people.” He’s a Republican, and his priorities are party staples: go light on regulation, be tough on crime, keep taxes low. But the thing that is winning him international renown is straight out of the liberal playbook—green power. Thanks to his (big) advocacy, Georgetown (pop. 67,000) last year became the largest city in the United States to be powered entirely by renewable energy.
Shi Zhengrong has said that, as of 2012, unsubsidised solar power is already competitive with fossil fuels in India, Hawaii, Italy and Spain. He said "We are at a tipping point. No longer are renewable power sources like solar and wind a luxury of the rich. They are now starting to compete in the real world without subsidies". "Solar power will be able to compete without subsidies against conventional power sources in half the world by 2015".[75]
Specifications: Colors: Red Rated power: 600W Nominal voltage: 12V Start-up wind speed: 2m/s Rated wind speed: 13m/s Survival wind speed: 45m/s Package weight: 13kg Wind wheel diameter: 0.9M Number of blades: 5 Blades material: Nylon fiber Nylon fiber: Three phase ac permanent magnet generator/Maglev generatorsThree phase ac permanent magnet generator/Maglev generators Controller system: Electromagnetic Speed regulation: The wind Angle automatically Working temperature: -40℃~80℃ Features: 1. Low start-up speed, high wind power utilization, light, cute, low vibration. 2.Simple to install and maintain. 3.For home use, For monitoring use, For boat / marine use, For wind solar hybrid streetlight use. Package: 1 x Wind Turbine Generators(with controller) 1 x Stainless steel.
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.
For a 6 kW wind turbine to produce that much energy per average year, you need an annual average wind speed of close to 5 m/s (11 mph) blowing at turbine hub height. It may not sound like much, but that is a reasonably windy place. Much of North America does not have that much wind at 100′ or below. Keep in mind, you need that much wind just to break even in energy production vs. solar. To outweigh the disadvantages of small turbines you better have more!

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.
Many companies are taking the push for 100 percent renewables seriously because they see it as good business — not just today, but for the long term. At the time of publication, 152 companies of various sizes have made a commitment to go 100 percent renewable through RE100. Big names like Apple and Google have already met their targets, while other companies are looking out further into the future, some as far as 2040. That timeline indicates companies are looking beyond today’s prices and present-day marketing benefits.
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.
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.
Rated power of a wind turbine may not be quite as meaningless as cut-in wind speed, though its use is limited. It could have some utility to quickly compare, or get a feel for, the size of the wind turbine, but only if those rated power numbers were taken at the same rated wind speed, and if the manufacturer is giving you a realistic number (many inflate rated power). A much better measure of turbine size is, simply, their diameter. As shown above it is by far the best predictor for power output.
“[The maps] suggest that our 100 percent renewable energy purchasing goal — which relies on buying surplus renewable energy when it’s sunny and windy, to offset the lack of renewable energy supply in other situations — is an important first step toward achieving a fully carbon-free future,” Michael Terrell, Google’s head of energy markets, wrote in a blog post. “Ultimately, we aspire to source carbon-free energy for our operations in all places, at all times.”

Ross is now an energy celebrity, sitting on conference panels and lending Georgetown’s cachet to environmental-film screenings. And it isn’t only conservatives who buttonhole him. As if to prove the adage that no good deed goes unpunished, he also hears from people who worry about the impact of renewables. “They’ll come up to me and say with a straight face, ‘You know what? Those windmills are killing birds,’ ” Ross says. “ ‘Oh, really? I didn’t know that was a big interest of yours, but you know what the number-one killer of birds is in this country? Domestic house cats. Kill about four billion birds a year. You know what the number-two killer of birds is? Buildings they fly into. So you’re suggesting that we outlaw house cats and buildings?’ They go, ‘That's not exactly what I meant.’”

Energy harnessed by wind turbines is intermittent, and is not a "dispatchable" source of power; its availability is based on whether the wind is blowing, not whether electricity is needed. Turbines can be placed on ridges or bluffs to maximize the access of wind they have, but this also limits the locations where they can be placed.[72] In this way, wind energy is not a particularly reliable source of energy. However, it can form part of the energy mix, which also includes power from other sources. Notably, the relative available output from wind and solar sources is often inversely proportional (balancing)[citation needed]. Technology is also being developed to store excess energy, which can then make up for any deficits in supplies.
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]
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.”

This solar resource map provides a summary of the estimated solar energy available for power generation and other energy applications. It represents the average daily/yearly sum of electricity production from a 1 kW-peak grid-connected solar PV power plant covering the period from 1994/1999/2007 (depending on the geographical region) to 2015. Source: Global Solar Atlas]
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