news digest ♦ Solar microtechnology.”
“The design of the system is elegantly simple,” adds Andrea Pedretti, chief technology officer at Airlight Energy. “We replace expensive steel and glass with low cost concrete and simple pressurised metalised foils. The small high-tech components, in particular the microchannel coolers and the moulds, 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.”
The solar concentrating optics will be developed by ETH Zurich. “Advanced ray-tracing numerical techniques will be applied to optimise the design of the optical configuration and reach uniform solar fluxes exceeding 2,000 suns at the surface of the photovoltaic cell,” explains Aldo Steinfeld, a professor at ETH Zurich.
With such a high concentration and a radically low cost design scientists believe they can achieve a cost per aperture area below $250 per square meter, which is three times lower than comparable systems. The levelised cost of energy will be less than 10 cents per kilowatt hour (KWh).
For 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.
Water Desalination and Cool Air
Current concentration photovoltaic systems only collect electrical energy and dissipate the thermal energy to the atmosphere. With the HCPVT packaging approach scientists can both eliminate the overheating problems of solar chips while also repurposing the energy for thermal water desalination and adsorption cooling.
Adsorption chillers, with water as working fluid, can replace compression chillers, which stress electrical grids in hot climates and contain working fluids that are harmful to the ozone layer.
Scientists envision the HCPVT system providing sustainable energy and potable water to locations around the world including southern Europe, Africa, Arabic peninsula, the southwestern part of the United States, South America, and Australia.
Remote tourism locations are also an interesting market, particularly resorts on small islands, such as the Maldives, Seychelles and Mauritius, since conventional systems require separate units, with consequent loss in efficiency and increased cost.
A prototype of the HCPVT system is currently being tested at IBM Research in Zurich. Additional prototypes will be built in Biasca and Rueschlikon, Switzerland as part of the collaboration.
To capture the medium grade heat IBM scientists and engineers are utilising an advanced technology they developed for water-cooled high performance computers, including Aquasar and SuperMUC. With both computers water is used to absorb heat from the processor chips, which is then used to provide space heating for the facilities.
“Microtechnology as known from computer chip manufacturing is crucial to enable such an efficient thermal transfer from the photovoltaic chip over to the cooling liquid,” says Andre Bernard, head of the MNT Institute at NTB Buchs. “And by using innovative ways to fabricate these heat transfer devices we aim at a cost- efficient production.”
In the HCPVT system, instead of heating a building, the 90 degree Celsius water will be used to heat salty water that then passes through a porous membrane distillation system where it is vaporized and desalinated. Such a system could provide 30-40 litres of drinkable water per square metre of receiver area per day, while still generating electricity with a more than 25 percent yield or two kilowatt hours per day - a little less than half the amount of water the average person needs per day according to the United Nations, but a large installation could provide enough water for a town.
The HCPVT system can also provide air conditioning by means of a thermal driven adsorption chiller. An adsorption chiller is a device that converts heat into cooling via a thermal cycle applied to an absorber made from silica gel, for example.
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www.compoundsemiconductor.net June 2013
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