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Solar Energy in Spain |
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 The engineering behind such a plant takes into account both the need to heat up the receiver and the importance of moderating the energy directed at it. “At this plant, we’re working with the potential of about 3,000 suns, but the absorption panels can only handle 600 suns,” says Valerio Fernández, head of engineering and commissioning for Solúcar. “We have to control the aiming to protect the solar panels.
So it has to be very well designed and operated to provide the best results.” Fernández says that so far the facility is operating as intended, but improvements will be incorporated into future towers. “This isn’t the best temperature for the highest efficiency,” he says, “but we wanted to test the safety and security of the design for this first installation. We’ll do the remaining research necessary in order to use higher temperatures in future plants.”
He explains that the cooling system for the boiler is more complicated as temperatures increase, but that once those changes are implemented, the tower’s efficiency could improve by 20 percent. The tower is also supported by a small amount of natural gas, used when a stretch of rainy or overcast weather prevents the plant’s full operation and the stored energy cannot stretch far enough to compensate. “It’s good to be able to maintain stability, not be stopping and starting up the turbines more than once a day, as they’re designed to do,” says Fernández. When completed in 2012, the entire Solúcar facility, called the Sanlúcar La Mayor Solar Platform, will generate more than 300 megawatts of solar power, using tower and trough technologies along with PV installations.
Abengoa, owner of Solúcar, has also recently signed plans to build combined-cycle power plants in Algeria and Morocco, using parabolic troughs in conjunction with natural-gas power plants. One of the main advantages of solar thermal power, in addition to the cost benefit, is the potential for power storage. The Solúcar tower uses a system of heat storage based on pressurized water. Sener’s Andasol site will use a more advanced system taking advantage of the specific properties of molten salt. It’s been tested in Spain but has not yet been implemented commercially. Located about an hour outside Granada, home to the world-famous Alhambra, Andasol 1 will provide power well into the evening hours. Sener, which is constructing the plant with a company called Cobra, has built extra troughs that will direct heated oil to 28,000 tons of molten salt (the salt is being imported from Chile). The salt must reach a high enough temperature to liquefy—and then it must be maintained in a liquid state to prevent it from causing blockages. Tubes carrying heated oil will pass through the molten salt, raising the temperature even higher, and the salt will retain the heat energy. As evening falls, the thermal energy will be transferred back to the oil, which wil l cont inue on to the heat exchanger and power the steam turbine.
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