Concentrated solar power is a method of using the Sun's light toproduce useful energy on Earth. A large system of mirrors collectslight during the day and focuses it on a target which is raised toa high temperature. The energy delivered to the target is then usedto generate steam which runs turbines to produce electricity. Themirrors do not have to be circular, and for some designs they focuslight along a line rather than to a point .
Concentrated solar power is a practical alternative to directsolar \"photovoltaic\" electric because the efficiency is high andbecause the energy collected may be stored, for example in moltensalts. However, it has a very significant environmental impact onwildlife because intense converging light may endanger birds andbats. A way to reduce that risk is to lower the temperature bycollecting light in long cylindrical troughs.
1. Suppose you wanted to collect power sufficient for 10,000homes, which on average use about 10,000 kilowatt hours a yeareach. Given a solar constant of 1.4 kW/m2, at a sitewith 300 clear days a year, how much area would be needed to gatherthe power required? Assume the turbines have an efficiency of 40%and there are 8 hours a day of useful sunlight. Given that area, ifit is covered by mirrors in a square array, what is the size of thesquare along one side in meters? Explain.
2. To save birds and avoid singed technicians, you design thearray to use cylindrically shaped mirrors focusing light to a lineon long pipes. In this way the delivered power is distributed overa larger target and the temperature of the target is kept low. Whatis the ideal shape of the mirror? If approximately that shape werea cylinder with a diameter of 4 meters, where would the pipe haveto be above the mirror's surface? Â
3. The source of the energy collected by this power station isthe fusion of hydrogen within the Sun's core where it is convertedto helium with a small loss of mass. How much mass does the Sunlose each year to deliver this energy to a solar power system onEarth?
