IBM re-uses PV thermal energy for better efficiency

MUNICH, Germany — IBM researchers recently have shown that the reuse of cooling liquid for computers can increase the total efficiency of a system. Now they do a similar trick on solar cells. The result could be an overall efficiency of better than 50 percent.

Already earlier this year, IBM researchers have improved the efficiency of GaAs solar cells by concentrating the sunlight falling onto the cell. In a trial, they were able to get 70 watts out of a solar cell with a size of one square centimeter by concentrating the sunlight by means of a large magnifying lens.

GaAs solar cells, while much more expensive than standard silicon cells, achieve far better efficiencies, explained Bruno Michel, Manager Advanced Thermal Packaging in IBMs Zurich research lab. The record efficiency published hitherto with GaAs is slightly better than 41 percent, Michel said. This efficiency could more than compensate for the high price.

And there is still headroom to further improve the efficiency. Currently Big Blue is fathoming out the potential of the technology in a project with the Egyptian government.

In the project, the engineers do not only use the electrical energy of the high-power solar cells, but also the heat generated by them. Thus, the overall energy efficiency considering the photovoltaic (electric) output as well as the thermal output of the system can be raised significantly."Our target is an efficiency of better than 50 percent," said Michel.

The waste heat in the project is used for another 'green' application: The engineers use it to desalinate water.

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