Stirling engine can convert solar energy to electricity with an efficiency better than non-concentrated photovoltaic cells,

http://en.wikipedia.org/wiki/Stirling_engine 

Solar power generation

Placed at the focus of a parabolic mirror a Stirling engine can convert solar energy to electricity with an efficiency better than non-concentrated photovoltaic cells, and comparable to Concentrated Photo Voltaics. On August 11, 2005, Southern California Edison announced^[64] an agreement with Stirling Energy Systems to purchase electricity created using over 30,000 Solar Powered Stirling Engines over a twenty year period sufficient to generate 850 MW of electricity. These systems, on an 8,000 acre (19 km²) solar farm will use mirrors to direct and concentrate sunlight onto the engines which will in turn drive generators. Construction is expected to begin on the farm in 2010^[65], although there are disputes over the project^[66] due to concerns of environmental impact on animals living on the site.