9 August 2010 – US-based developer of clean heat and power generating systems Cool Energy has announced that Minneapolis-based utility Xcel Energy will be providing research and analytical support for the first planned pilot field installation of the Stirling engine-based ‘SolarFlow’ solar-CHP system in a commercial building located in Boulder, Colorado.
 
The SolarFlow CHP generation system uses solar energy as its only input ‘fuel’ and is sized for residential and small commercial buildings.
 
The system has several novel features, including energy storage and a control system that maximizes customer value by optimally apportioning the system’s energy output between heat and electricity depending on the season and weather conditions – both current and forecasted.
 
Central to the system is Cool Energy’s low-temperature ‘SolarHeart’ engine, a specialized Stirling engine-powered electricity generator that the system activates whenever the electricity produced is more valuable than the heat consumed.
 
Under laboratory conditions of a temperature differential of 210 ºC, the third generation SolarHeart engine to be used for this field test recently generated over 2 kW of electrical power, and reached a thermal-to-electrical conversion efficiency of over 16%, exceeding expectations, says the company.
 
‘Xcel Energy is pleased to be involved in the benefits evaluation of Cool Energy’s innovative solar thermal system,’ said Dennis Stephens, the utility’s director of smart grid investments.
 
‘The energy industry is particularly interested in the potential to provide dispatchable power on demand at times when energy consumption is high.’