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.
“What Changes Will Maine’s New Government Bring to Your Life?” • Swept to sizable majorities in last week’s elections, Maine’s Democrats will be in full control of state government for the first time since 2010. They are likely to look for ways to address a number of pressing issues, one of which is climate change. [Kennebec Journal & Morning Sentinel]
There is one more area where buyers may get a false sense of security: Several states in the US have lists of “approved” wind turbines for their rebate programs. An example of this is the California list. The problem is that approval for this list, and the performance data provided (such as rated power and energy production) are essentially self-certified. The less-scrupulous manufacturers can ‘manufacture’ data and submit it under the pretence that it was measured. The only value of those lists is in telling you what rebates are available, they do not provide reliable turbine information.
Since 2013 the world's highest-situated wind turbine was made and installed by WindAid and is located at the base of the Pastoruri Glacier in Peru at 4,877 meters (16,001 ft) above sea level. The site uses the WindAid 2.5 kW wind generator to supply power to a small rural community of micro entrepreneurs who cater to the tourists who come to the Pastoruri glacier.
While renewables have been very successful in their ever-growing contribution to electrical power there are no countries dominated by fossil fuels who have a plan to stop and get that power from renwables. Only Scotland and Ontario have stopped burning coal, largely due to good natural gas supplies. In the area of transportation, fossil fuels are even more entrenched and solutions harder to find. It's unclear if there are failures with policy or renewable energy, but twenty years after the Kyoto Protocol fossil fuels are still our primary energy source and consumption continues to grow.
The incentive to use 100% renewable energy, for electricity, transport, or even total primary energy supply globally, has been motivated by global warming and other ecological as well as economic concerns. The Intergovernmental Panel on Climate Change has said that there are few fundamental technological limits to integrating a portfolio of renewable energy technologies to meet most of total global energy demand. Renewable energy use has grown much faster than even advocates anticipated. At the national level, at least 30 nations around the world already have renewable energy contributing more than 20% of energy supply. Also, Professors S. Pacala and Robert H. Socolow have developed a series of "stabilization wedges" that can allow us to maintain our quality of life while avoiding catastrophic climate change, and "renewable energy sources," in aggregate, constitute the largest number of their "wedges".
Most current solar power plants are made from an array of similar units where each unit is continuously adjusted, e.g., with some step motors, so that the light converter stays in focus of the sun light. The cost of focusing light on converters such as high-power solar panels, Stirling engine, etc. can be dramatically decreased with a simple and efficient rope mechanics. In this technique many units are connected with a network of ropes so that pulling two or three ropes is sufficient to keep all light converters simultaneously in focus as the direction of the sun changes.
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.
When energy is purchased from the electricity network, the power reaching the consumer will not necessarily be generated from green energy sources. The local utility company, electric company, or state power pool buys their electricity from electricity producers who may be generating from fossil fuel, nuclear or renewable energy sources. In many countries green energy currently provides a very small amount of electricity, generally contributing less than 2 to 5% to the overall pool. In some U.S. states, local governments have formed regional power purchasing pools using Community Choice Aggregation and Solar Bonds to achieve a 51% renewable mix or higher, such as in the City of San Francisco.
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.
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.”
Most in the industry agree that 11 m/s (24.6 mph) makes for a good rated wind speed. Go above it and very soon the turbine should be hard at work to protect itself from destruction, by furling, governing, or shutting down. Those that do not will likely face a short and tortured life. If we agree on 11 m/s, an equation for a realistic rated power number is as follows:
As the cost of solar electricity has fallen, the number of grid-connected solar PV systems has grown into the millions and utility-scale solar power stations with hundreds of megawatts are being built. Solar PV is rapidly becoming an inexpensive, low-carbon technology to harness renewable energy from the Sun. The current largest photovoltaic power station in the world is the 850 MW Longyangxia Dam Solar Park, in Qinghai, China.