What a Dish! Solar Energy Alchemy Creates Water

Two-for-one is usually a superior deal, especially when it comes to renewable energy and efficiency.

And that’s what is happening with a new solar dish that does what solar installations do, convert sunlight into power, but with an interesting twist: clean water.

The efficiency of the typical solar installation ranges from 10 to 20 percent, with the rest waste heat. Swiss researchers associated with IBM have developed the High Concentration PhotoVoltaic Thermal system (HCPVT), which uses that waste solar heat to generate fresh water.

It’s the equivalent of the ancient craft of turning lead into gold. Only real.

IBM says the solar dish is built from low-cost materials, making the per area price of set-up significant lower than comparable solar systems.

The dish is covered in small mirrors that concentrate sunlight on a small module of photovoltaic cells. That design makes the dish highly efficient, converting 30 percent of the received solar radiation into electricity and providing 25 kilowatts of power. But it also means the solar module faces an enormous heat concentration. To keep it from melting, the HCPVT employs a liquid coolant system that IBM first developed for high-performance computers: it is 10 times more effective than traditional passive air cooling.

The liquid keeps the solar cells operating safely at up to 5,000 times the normal solar concentration by drawing away the waste heat, after which the heated coolant is used to vaporize salty water in a desalinization system.

As a result, the HCPVT recovers half the waste heat and puts it to productive use as drinkable water.

An initial demonstrator of the multi-chip receiver was developed under a previous collaboration between IBM and the Egypt Nanotechnology Research Center.

"We believe that we can achieve this with a very practical design that is made of lightweight and high strength concrete, which is used in bridges, and primary optics composed of inexpensive pneumatic mirrors -- it's a frugal innovation, but builds on decades of experience in microtechnology,” said Bruno Michel, manager, advanced thermal packaging at IBM Research.

"The design of the system is elegantly simple," added Andrea Pedretti, chief technology officer at Airlight Energy. "We replace expensive steel and glass with low cost concrete and simple pressurized metalized foils. The small high-tech components, in particular the microchannel coolers and the molds, can be manufactured in Switzerland with the remaining construction and assembly done in the region of the installation. This leads to a win-win situation where the system is cost competitive and jobs are created in both regions."

With such a high solar concentration and a radically low cost design, scientists estimate they can achieve a cost per aperture area below $250 per square meter, or three times lower than comparable systems. The leveled cost of energy will be less than 10 cents per kilowatt hour (KWh). In comparison, feed-in tariffs for electrical energy in Germany are currently still larger than 25 cents per KWh and production cost at coal power stations are around 5-10 cents per KWh.

One square meter of receiver area in the HCPVT system can provide 30 to 40 liters of drinkable water per day — about half the needed daily amount for the average person, according to the United Nations. Researchers believe a large array of the dishes could produce enough fresh water to sustain a town.

A prototype of the HCPVT system is currently being tested at IBM Research - Zurich. Additional prototypes will be built in Biasca and Rueschlikon, Switzerland as part of the collaboration.

It sounds like something from a science fiction story, but if technologically and commercially feasible on a large scale—wow.

[Image: Prototype Solar Dish captured from "A Solar Energy Breakthrough" by IBMSocialMedia on YouTube]