Heliostat - Small-scale Projects

Small-scale Projects

Smaller heliostats are used for daylighting and heating. Instead of many large heliostats focusing on a single target to concentrate solar power (as in a solar power tower plant), a single heliostat usually about 1 or 2 square meters in size reflects non-concentrated sunlight through a window or skylight. A small heliostat, installed outside on the ground or on a building structure like a roof, moves on two axes (up/down and left/right) in order to compensate for the constant movement of the sun. In this way, the reflected sunlight stays fixed on the target (e.g. window).

Genzyme Center, corporate headquarters of Genzyme Corp. in Cambridge, Massachusetts, uses heliostats on the roof to direct sunlight into its12-story atrium.

In a 2009 article, Bruce Rohr suggested that small heliostats could be used like a solar power tower system. Instead of occupying hundreds of acres, the system would fit in a much smaller area, like the flat rooftop of a commercial building, he said. The proposed system would use the power in sunlight to heat and cool a building or to provide input for thermal industrial processes like processing food. The cooling would be performed with an absorption chiller. Mr. Rohr proposed that the system would be “more reliable and more cost-effective per square meter of reflective area” than large solar power tower plants, in part because it would not be sacrificing 80 percent of the power collected in the process of converting it to electricity.