It is conventional that CHP when used in domestic environment, it is a heat led solution.
Whisper Gen has responded to this by creating a CHP which can nominally produce 7kW thermal for every kWe it produces. It can match the peak heat requirements of a large domestic house during the winter, replacing a boiler. The extra electricity produced is a bonus. But there are some basic problems with this solution.
Firstly, the problem lies in the production of electricity. 1kWe does not match the peak loads of a building. During the night, the demand is around 50-100W. The additional electricity has to be exported, which can only be sold to the grid at around 20% of the rate you buy. This makes it neither cost-effective nor a simple system to take up.
Secondly, the problem lies in the domestic heat requirements. Although the winter space heating requirements of a large house can be as high as 10kW during the winter but during the summer there is no load. This large variation is not suited for CHP, as it works best at high efficiency, when there is a large constant heat requirement. Most CHP units have to be turned off during summer months when the heat load is down, making it far less economical.
We found that, although CHP can reduce the bills, its long payback period do not encourage to invest in the system.
Thus optimising a badly designed CHP, to cope up with the problems is not the answer, but to change the mindset on how CHP can be used. Thus it is essential, to integrate demand and supply together in a holistic solution.
© University of Strathclyde 2009
