A PV concentrator utilizes a fused glass structure as an airtight enclosure similar to an automotive sealed-beam headlamp. One half is aluminized to provide a reflector for the impinging sunlight and for focusing it on a photocell within the enclosure.
An example of increased solar efficiency comes from Boeing-Spectrolab, Sylmar, Calif., a manufacturer of multijunction solar cells, which recently claimed a record efficiency of 39% at 236 suns. (The number of suns indicates how concentrated the sunlight was. The efficiency of a solar cell is measured by the percentage of the sun's energy the device converts to electricity.)
PV concentrators are unlike the 1,200 MW of flat PV modules sold last year around the world. Best suited for large utility installations, concentrators usually come in sizes of 20 to 35 kw each and are designed to track the sun during the day.