Marzwell and his colleagues at JPL are studying ways to capture waste heat and convert it to electricity by means of thermal voltaic processes. Special coatings on the mirrors and lenses can also reject portions of the sun's spectrum that PV arrays don't use, further reducing excess heat. One possibility is to convert stored solar energy to microwave radiation and beam it down to a combination rectifier-antenna, called a rectenna, located in an isolated area. According to Marzwell, the dangers of being close to the microwave beam would be similar to the dangers of cell phone transmissions, microwave ovens or high-power electrical transmission lines. You can put these small receivers in the desert or in the mountains away from populated areas.
Lasers are also under consideration for beaming the energy from space.
Using lasers would eliminate most of the problems associated with microwave but under a current treaty with Russia, the U.S. is prohibited from beaming high-power lasers from outer space. All in all, the positive aspects of such a system appear to outweigh the negative ones. Space-based solar power offers energy from an unending source with no emissions and very little environmental impact. According to Marzwell, using today's technology a space solar power system could generate energy at a cost of 60 to 80 cents per kilowatt-hour. This estimate includes construction costs for the first system.