The second-generation prototype came on-line in June 2012.
Power Generation
In the summer of 2012, a team of REhnu and University of Arizona engineers completed the second-generation full-scale module prototype. This prototype module generates 2.7 kW of electricity and uses a 3.1 m square dish reflector and a receiver (power conversion unit) with thirty-six 15 mm square cells, operated at a geometric concentration of 1200x. The active cooling system—two radiators positioned above the receiver—works well, with the cell temperature running only about 20°C above ambient. The parasitic loss is small—the active cooling system consumes no more than 2.5% of the generated electricity.
A closer view of the second-generation power conversion unit.
Second-Generation Improvements
Data for one day with a peak ambient temperature of 40°C.
• Increase in DC system efficiency from 23% to 28%
• Dish reflector with better optical surface quality and improved reflectivity
• Improved PV cell conversion efficiency, to 37–38% at 25°C
• More compact radiator assembly that blocks less light (shown below)
• Ball lens coating that boosts sunlight transmission at blue wavelengths
• Greater reliability: 100 hours on-sun with no failures
The second-generation prototype radiator assembly (shown at right) blocks less incident light to the dish reflector because of its thin, long design and smaller cross section.
