Performance implications of heat pumps and micro-cogenerators participating in demand side management

This work considers the potential impact of participating in demand side management on the performance of air source heat pumps and micro-cogenerators. As significant consumers and generators of electricity at the distribution level, large numbers of heat pumps and micro-cogenerators would provide considerable scope for participation in demand-side management systems. However, it is possible that operating regimes which are optimised for grid considerations will not achieve the maximum performance that is possible from these units.
Modelling has been conducted to investigate the significance of this effect, considering the case where local distribution constraints are the main driver for demand side interventions. A model of domestic electrical demand has been adapted to consider a neighbourhood of 128 dwellings in order to identify when interventions are necessary. This has been combined with dynamic models of two micro-cogenerators (derived by IEA ECBCS Annex 42 and based on Stirling engine and internal combustion engine prime movers) and a similar model of an air source heat pump. A simple thermal model of each building is combined with a range of user preferences in order to determine the preferred operating profiles of the heating units.
The efficiency of the air source heat pump units is generally found to suffer by about 5% but additional heat losses bring the total increase in primary energy required by the air source heat pumps to 10% to 25%. Although the performance of the micro-combined heat and power units is observed to vary with the operating conditions, this variation is not specifically an effect of demand side management. The effects are not as significant as the observed variations in performance due to differences in installation and operation of the units but are large enough to warrant consideration when assessing the benefits and costs of a similar scheme.