IBM researchers in Switzerland have designed a high concentration photovoltaic thermal system (HCPVT) that concentrates solar radiation by a factor of 2,000, and converts 75% into usable energy. A parabolic reflector tracks the sun and focuses its rays onto an array of triple-junction photovoltaic chips. To prevent them melting, the array uses microchannel water-cooling, a technique also used in high-performance computers, which circulates the coolant to within a few tens of micrometres of the chips.
The array holds hundreds of 1cm2 standard commercial chips, each generating 50W of electricity – a 30% solar energy conversion rate. (Without concentrated sunlight, each chip would generate just 25 milliwatts.) The system’s energy conversion rate is boosted to over 75% by using the coolant’s waste heat to power desalination or air-cooling units. Currently, the best conversion rate for concentration photovoltaic systems is around 60%.
Dr Bruno Michel of IBM Research in Zurich expects their 100m2 dish prototype system to be ready in three years. “Our design, which uses concrete and pressurised metal foil instead of steel and glass, reduces the reflector’s costs by about two-thirds”, he says, “and we estimate the system will produce electricity for roughly $0.1/kWh over the plant’s lifetime – similar to the cost of electricity produced by coal fired plants.” A prototype is currently being tested at IBM Research in Zurich, and the concrete structures and high-tech components for two more will also be built in Switzerland.
IBM is collaborating on the project with Airlight Energy, the Swiss Federal Institute of Technology, and the NTB Interstate University of Applied Sciences. The Swiss Commission for Technology and Innovation has awarded the project a three-year $2.4 million grant.
“This cogeneration solar project is challenging and ambitious”, says Dr Andreas Bett of the Fraunhofer Institute for Solar Energy Systems in Freiburg, Germany. “It promises practical, highly efficient solar radiation conversion systems in the foreseeable future.”