Solar Cogeneration  

Inhabitat has an interesting post on a company called Solarwall who are developing rooftop solar cogeneration systems.

Solar photovoltaics are, depending on the day, between 8-15% efficient meaning much of the sun’s energy’s is lost as heat. While solar thermal systems offer a way to harvest this heat energy for heating water or interior spaces, this option has usually displaced the electricity generating PV on rooftops. A new system from SolarWall, the SolarDuct PV/T, offers a combination of solar photovoltaic and solar thermal in one assembly providing a means to heat and power from the sun with one product.

The system is an evolution of the SolarWall system, a vertical mounted solar thermal and heat recapture system that transfers heat into or away from a building’s HVAC mechanicals depending on the season. The SolarDuct PV/T is based on the same principle of capturing heat from the sun and heat generated from excessive solar gain on buildings. The new system adds photovoltaic over thermal ducts to maximize energy efficiency.

The captured warm air can be vented into the HVAC system, preheated, to decrease the building’s energy load. The draw of air away from the photovoltaics “also enhances the electrical operating efficiency of the PV by up to 10%,” according to the manufacturer Conserval Engineering Inc. The solar thermal duct system acts as the mount for the PV, pre-angled to maximize solar gain and making it ideal for flat roof installations.

In addition to optimizing rooftop real estate with a two-in-one solar energy system, the Solar Duct PV/T seems to hold the potential to shorten the payback time on investment, since it decreases a building’s heating demand while producing electricity.