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Energy Storage for Solar Power

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Startup Brightsource announces a new system that could allow future solar plants to run at night.

Stored sunlight: A rendering shows Brightsource’s new thermal storage design. The two large tanks will store molten salt, which can be used to generate steam to drive a turbine.

Brightsource Energy has become the latest solar thermal power company to develop a system for generating power when the sun isn’t shining. The company says the technology can lower the cost of solar power and make it more reliable, helping it compete with conventional sources of electricity.
The company, based in Oakland, California, is building one of the world’s largest solar thermal power plants. The 392-megawatt solar plant in Ivanpah, California, however, will not include the storage technology. Instead, Brightsource is working with utilities to determine which future projects could best benefit from storage.
Solar thermal systems use mirrors to focus sunlight, generating temperatures high enough to produce steam to drive a turbine. One of the advantages of the solar thermal approach, versus conventional photovoltaics that convert sunlight directly into electricity, is that heat can be stored cheaply and used when needed to generate electricity. In all solar thermal plants, some heat is stored in the fluids circulating through the system. This evens out any short fluctuations in sunlight and lets the plant generate electricity for some time after the sun goes down. But adding storage systems would let the plant ride out longer periods of cloud cover and generate power well into, or even throughout, the night. Such long-term storage could be needed if solar is to provide a large share of the total power supply…. Read the rest of this entry »

Written by physicsgg

August 9, 2011 at 12:42 pm

Posted in TECHNOLOGY

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Space solar power: Let the sun shine in

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Energy: Satellites that beam solar power to earth have often appeared in science fiction. Will they ever become reality?

“REASON”, a short story written by Isaac Asimov that was published in 1941, is set on a space station which collects solar energy from the sun and sends it, via microwave beams, to earth and other planets. The robots that control the beams are under the command of a more advanced model called Cutie, which turns out to have developed its own religion, and ignores the wishes of two astronauts who visit the station. As a solar storm approaches, the humans worry that Cutie will be unable to control the beam sending power to earth, causing it to fall on cities and incinerate them. But in the event, the robot’s religious yearning to keep the power flowing means that no harm is done. The moral: actions matter more than beliefs.
Today it is not just robots in science-fiction tales who are believers in the wonders of space solar power (SSP); the idea also has a small but growing number of human adherents. The basic idea is simple. Light from the sun is the most abundant and cleanest source of energy available in the solar system. Around the clock, 1.3 gigawatts of energy pour through every square kilometre of space around the earth. This energy could be captured by vast arrays of photovoltaic cells mounted on a satellite in orbit around the planet. These solar cells would be illuminated at all times of day, whatever the weather or the season, overcoming one of the main drawbacks of solar power on the earth’s surface. And with no atmosphere in the way to absorb or scatter the incoming sunlight, solar panels in space would produce over five times as much energy as those on the ground. (Some proposals for SSP involve large arrays of mirrors or lenses to concentrate the light onto a smaller array of panels.)

The logical place to put the satellite would be in a geostationary orbit, 35,800 kilometres above the earth’s equator, so that it completes one circuit of the planet per day, and thus appears (from the ground) to hover in a fixed place in the sky, like the communications satellites used to broadcast television signals. The solar-power satellite would send the collected energy down to earth in the form of a microwave beam, which would be picked up on the ground by a huge array of antennae, spread over several square kilometres in open country. The power density of the beam at the receiver would be little greater than what leaks out from a domestic microwave oven, so there would be no danger of incinerating entire cities. Microwave communications links are already used in the telecoms industry without doing any harm to wildlife…… Read the rest of this entry »

Written by physicsgg

July 4, 2011 at 2:31 pm

Posted in SPACE

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