Concentrating solar power with a Stirling engine

In January 2010, Teserra Solar and Stirling Engine Systems showcased the Maricopa Solar plant in Arizona. This is the first commercial project for the SunCatcher concentrating solar power technology designed and manufactured by Stirling Engine Systems.The innovative and highly-efficient SES SunCatcher is a 25-kilowatt solar power system which uses a 38-foot, mirrored parabolic dish combined with an automatic tracking system to collect and focus the sun’s energy onto a Stirling engine to convert the solar thermal energy into grid-quality electricity. Developer Tessera Solar has created a 1.5 megawatt power plant out of 60 SunCatcher solar thermal devices.

SunCatcher has a number of advantages including the highest solar-to-grid electric efficiency, zero water use for power production, a modular and scalable design, low capital cost, and minimal land disturbance. SunCatcher was designed and developed in America, through a public-private partnership with the U.S. Department of Energy. The SunCatchers unveiled at Maricopa Solar were manufactured and assembled in North America, mostly in Michigan by automotive suppliers.

Now that the plant is up, Stirling will be able to compare the results its gets from its Stirling engines from heliostat prototype power plants erected by eSolar in Southern California and BrightSource Energy in Israel as well as parabolic trough systems that have already been commercially deployed. Parabolic companies, BrightSource and eSolar collect solar heat on mirrors and use it to heat fluid. The warmth causes the fluid to expand, which creates pressure that gets exploited to crank a turbine.

The Company has publicly quoted a fully-installed cost for grid-scale plants of $2.8 million per megawatt.

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World’s largest solar project planned in Sahara

If just 0.3% of the Saharan Desert was used for a concentrating solar plant, it would produce enough power to provide all of Europe with clean renewable energy. That is why 20 blue chip German companies are gathering in July 2009 to discuss plans and investments to create such a massive project. Both the meeting and project are being promoted by the Desertec Foundation, which is proposing to erect 100 GW of concentrating solar power plants throughout Northern Africa.

The red squares in the map to the right represent the land area necessary to meet the energy demand of the world, the EU and MENA in 2005. The last square represents the land necessary for the proposed project to generate 100 GW of concentrating solar power. The project being proposed by Desertec would not all be situated in one location, but scattered throughout politically stable countries. Taken as a whole, the project qualifies as the world’s largest solar installation – 80 times larger than the PG&E and BrightSource project planned for the Mojave Desert. The power generated would be transported over high-voltage DC lines across the Mediterranean Sea to Europe, where it would supply 15% of the energy demand. The project is still 10-15 years from going online, but that’s why major players are getting started now.

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Dyeing for more solar power

The main impediment to the widespread use of solar power – clouds and nightfall aside – is the cost of the silicon cells that actually convert the sun’s rays into electricity. To keep the expense down, people have been searching for ways to minimise the size of solar panels relative to the amount of light they can harvest. Often, this is done using clunky pieces of kit called solar trackers, which tilt an array of mirrors so as to direct large amounts of sunlight onto small, high-performance cells.

An alternative now being tested is called the luminescent solar concentrator (LSC). Instead of focusing the sun’s rays on a cell, as a solar tracker does, an LSC first traps them, wherever they have come from, and then delivers them to the cell using what is known as a waveguide. No moving parts are involved. A group of MIT researchers using this technology believe it could boost a solar panel’s efficiency by up to 50 percent and formed a company, Covalent Solar, to develop the technology.

The team has spent two years identifying organic dyes, painted onto glass or plastic that can effectively concentrate the sun’s light onto solar cells, enabling them to produce more electricity from fewer cells. The dyes basically reflect the light (technically, it’s actually absorbed and then sent back out), so that some of it is trapped inside the plane of glass. With the help of a scientific principal called “internal refraction”, which is the same principal that keeps light trapped in optical fibers, the light bounces to the edges of the glass, which have been equipped with strips of solar cells that convert it into electricity.

Integrated into solar panels available today, the technology could potentially boost the amount of light the panels convert into electricity by as much as 50 percent so consumers would get more electricity for their money.

The company hopes the technology could be used for both rooftop systems and for large solar farms and even one day could be integrated into windows, where a greyish tint would let in 20 percent to 30 percent of the outside light, while simultaneously directing the light toward solar cells around the window’s edges. Covalent Solar expects to bring its first product to market in three years.

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IKEA like solar system

Armageddon Energy has come up with a framing system and a lightweight solar panel that can pretty much go straight from a few cardboard boxes to your roof, sort of like furniture from IKEA.

A single solar “clover” from Armageddon consists of a triangular frame, a micro-inverter and three lightweight silicon hexagonal solar panels. A single can put out 400 watts. A few Tab A into Slot Bs and it’s complete. Three on the roof together can provide a house with a kilowatt of power. The clovers still have to be secured to the roof, angled toward the sun and plugged into the electrical system – which works best when handled by professionals – but much of the grunt work associated with conventional solar systems is already done. As a result of pre-fabbing, the cost of an Armageddon system will be lower, the company asserts.

The clovers are also lightweight. A single hexagonal solar panel weighs around 10 to 12 pounds. A conventional silicon solar panel might weigh 40 pounds. Lower weight means cheaper shipping, lower carbon taxes (where applicable) and a more rapid install. And installation costs could stand some trimming. Installation still accounts for around 30 percent to nearly 50 percent of the cost of a solar system. Over the past three decades, the vast majority of research in the industry has focused on increasing the efficiency of solar cells and reducing the amount of raw material required for solar cells.

The hexagonal panels weigh less than conventional panels because the cells are encased in a Teflon coating from DuPont rather than glass. The company also believes the hexagonal shape makes it more efficient. Circles tend to be strong, but contain a lot of wasted space. Rectangles are, by their nature, off-balance. Hexagons are inherently strong and efficient. Hexagonal solar panels means the company can also use triangular racks, and triangles tend to be fairly stable.

Original article: Michael Kanellos. Greentechmedia. 13 May 2009. Read more…

Solar Updraft Tower to generate Food and Energy

A new breed of solar tower may soon be sprouting up in Namibia, providing the nation with a carbon-free source of electricity and food during the day and night. At one and a half kilometers tall and 280 meters wide, these massive solar updraft towers could potentially produce 400MW of energy each – enough to power Windhoek, the nation’s capital. Proposed by intellectual property company Hahn & Hahn, the towers generate energy by forcing heated air through a shaft lined with wind turbines. Additionally, the base of each tower will function as a 37 km² greenhouse where crops can be grown.

Solar updraft towers are an oft-overlooked source of alternative energy, although they do require a great expanse of space and copious amounts of sunlight. Fortunately Namibia’s arid desert region provides plenty of space for such a generator, and the country sees around 300 days of sunshine per year.

Solar updraft towers generate energy by using sunlight to heat the air within a vast transparent greenhouse situated at the base of the chimney. As the hot air rises, it is funnelled into the reinforced concrete chimney, driving a series of wind turbines which in turn generate energy.

The structure’s greenhouse base provides the perfect environment for growing crops, which actually allow the plant to produce energy after the sun has set. The water used for crops is heated during the day and transfers this energy to the tower at night.

Original article: Mike Chino. Inhabitat. 10 September 2008. Read more…

Solar reaches low-income Indians

Bangalore, India-based social venture SELCO India recently raised growth financing to expand its program to provide renewable energy to low-income homes and businesses in India. The amount of funding was undisclosed and was led by an equity investment by Swiss-registered nonprofit Good Energies Foundation, which shares ownership with global venture capital firm Good Energies. The Lemelson Foundation and nonprofit E+Co also contributed.

SELCO India, short for Solar Electric Light Company, has sold, financed and serviced solar power units to 100,000 homes in India through microfinance and other models from a network of 25 rural service centres across the southern state of Karnataka. About two-thirds of its customers survive on less than $4 a day. The company is also working on cleaner versions of cookstoves, solar-powered water pumps and wireless communication.

According to India’s Central Electrical Authority, the country currently has the capacity to produce 130,000 MW of electricity every year but has a peak energy shortage of more than 15 percent.

SELCO was the recipient of the FT ArcelorMittal Boldness in Business Award for Corporate Social Responsibility.

Original article: Emma Ritch. Cleantech Group. 13 January 2009. Read more…

Could Solar Highways Power our Cities?

In the search for a solar solution to power our cities, one of our biggest obstacles is the massive acreage required by conventional arrays. Photovoltaic panels are flat and expansive, and urban centres are at a serious loss for free space.

Now Australian renewable energy retailer Going Solar has conceived of a clever strategy that infuses urban transit systems with energy producing potential – install solar panels in highways as sound barriers! Going Solar’s first highway installation was completed on the Tullamarine Calder Interchange in Australia. The solar sound barrier comprises 500 meters of photovoltaic panels that are attached to a public display showing the project’s power output.

As the highway is located near some residential areas, energy doesn’t have to travel far to reach its destination and the massive solar panels provide much needed soundproofing to the houses nearby.
It is expected that the installation will produce 18.7 megawatts per year, which is enough to cover its cost in about 15 years. The innovative application has netted Going Solar the ATRAA’s award for best grid-connected system.

Original article: Jorge Chapa. Inhabitat. 30 August 2008. Read more…