Power plants that work with concentrated solar power use special molten salt to convert the sun’s heat into steam which turns the generators that produce electricity. Researchers at the Georgia Institute of Technology say using molten metal instead of salt may increase the efficiency of the generators. The innovative design was presented at the recent energy summit in Washington.
While water circulates in this scale model of a concentrated solar power plant, a full-size plant uses molten salt. But the man behind the radical new design says using tin instead of molten salt could make the process dramatically more efficient.
“The main thing that makes it better than the state of the art is really the fact that by pushing up the temperature we were able to use a higher efficiency power cycle and the higher efficiency means for the same size of field you get more power out," said Asegun Henry of the Georgia Institute of Technology.
Molten tin can get hotter than molten salt, but it cannot flow through metal pipes. Experimenting in his lab, Henry found that it easily flows through pipes and valves made of graphite.
“It's machineable so it allows us to make complicated components like this where you can thread them, you can still use mechanical interfaces you are used to," said Henry.
His design uses ceramics that can also withstand high temperatures, do not corrode and do not react with tin. With good insulation, tin can stay liquid even overnight. So far, all the critical parts have been tested.
“We can pump liquid metal, we can valve it, and control it, we can bond these tubes together without getting leaks," explained Asegun Henry.
Taking into account the size of the required mirror field and the cost of the special salt, Henry expects using molten tin should reduce the overall cost of building a concentrated solar heat plant by as much as 30 percent.