James Holloway, writing for Ars Technica:
Ordinarily, the remaining 70 percent of energy would be lost as heat. But by capturing most of that heat with water, IBM Research says it is able to reduce system heat losses to around 20 percent of the total incoming energy. This results in a bottom-line efficiency of 80 percent for its CPV collector, dubbed HCPVT for High Concentration Photovoltaic Thermal. Unlike a regular CPV system, HCPVT delivers its energy in two forms: electricity and hot water.
Technology Review also has a good article on the technology, which uses a mirrored dish to concentrate solar energy on a small photovoltaic. To keep the solar cells cool, IBM adapted the water-cooling system used in their Aquasar supercomputer. It also allows them to recover energy that’s normally lost as waste heat. That hot water can then be used for water purification, heating, or, somewhat counterintuitively, cooling via absorbtion refrigeration.