Repurposed auto parts aren’t the only way to go. Amy Sun, a graduate student in MIT’s Media Lab, has designed an inexpensive system that uses heat from a solar concentrator to drive a type of turbine originally patented by Nicola Tesla. Rather than making complex, difficult-to-manufacture bladed turbines, Sun turned to the Tesla turbine, which consists of simpler flat disks stacked like records on a central shaft. The disks are carefully spaced to allow steam to flow between them. As the steam flows, friction between the steam and the surface of the disks causes them to rotate. “Once I have rotational shaft work, I can couple it to almost anything – an air pump, compressor, fan, mixer, grinder, sewing machine, refrigeration compressor, and, to power those very few things that are truly electric in nature, an electric generator.” She calculates that this system, which she says is simple enough for an eight-year old to make, can produce cheap power.
Of course the overall economics of these solar generator systems depend on how long they will last and how much maintenance they will require. The lifetime for Orosz’s system could be quite good, since it uses parts designed for rugged service in vehicles. It also works at relatively low temperatures that, in addition to making it safer and easier to work with, won’t strain the performance limits of the plumbing used.
Having already built a working prototype, Orosz’s next step, which he hopes to accomplish starting this September in Lesotho, is to optimize manufacturing and set up a financing system, drawing on a recent $100,000 World Bank grant, to make the system affordable to villagers who would likely use the generator in a community center and as a battery-charging station.
Although their system was originally designed for Lesotho, Orosz and his colleagues believe it might appeal to amateurs elsewhere. “Backyard tinkerers could build it themselves. No doubt about it,” says Amy Mueller, an MIT graduate student who’s taken on a leading role in Orosz’s project. “Matt’s dad has one of these that we built to heat his Jacuzzi.”