WIT Press

Micro Cogeneration With A Price-variable Heat Storage Switch


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G. Kaestle


Operating modes of combined heat and power (CHP) units are: heat driven, power driven and grid driven. CHP mini blocks are also known as \“magic boilers” or as electricity generating heating. Several techniques have been developed for optimising the economic dispatch of the CHP-system including the cogeneration unit, a heat buffer, and a peak burner, as well as thermal and electrical loads. This paper will propose a simple and easy to implement method in order to benefit from the different modi operandi. Ordered by contribution margin, the storage level of the heat buffer switches the CHP-system between the modes off, grid or power driven, heat driven, and full load. A daytime variable but static price profile is saved in the system control. It dynamically contracts or expands the threshold levels of the storage switch. Finally, the results of a simulation are presented in which a settlement of 80 CHP-equipped households is turned into a net electricity exporter, thus substituting coal based medium load power by natural gas. Keywords: cogeneration, heat storage, microCHP, power dispatch, price profile. 1 Motivation The sales numbers of the Honda Ecowill in Japan, as well as those of Senertec Dachs in Germany, are showing that micro cogeneration systems are beginning to move out of their niche market. In the UK two Stirling based designs for domestic cogeneration – Microgen and Whispergen – are competing in field tests for being the first one to hit mass production. The question is whether these tiny electricity generators should operate only to meet the local heat demand, or


cogeneration, heat storage, microCHP, power dispatch, priceprofile.