Analysis of innovative micro-CHP systems to meet household energy demands

摘要

This paper presents an analysis aimed to evaluate the feasibility of micro-CHP systems to meet the household energy demands of single family users. The considered CHP systems, with an electric power output of a few kW, are based on technologies (internal combustion engines, micro gas turbines, micro Rankine cycles, Stirling engines and thermophotovoltaic generators) which are already available on the market or will be available in the near future. Each CHP system is composed of (i) a prime mover, (ii) a thermal energy storage unit and (iii) an auxiliary boiler used to cover peak thermal demands. The analyses performed in this paper aim to evaluate (i) the energy performance of the CHP systems to meet the energy demand of two single-family dwellings, with different floor areas and shape factors, and (ii) the maximum cost allowed for each CHP system. The results presented in this paper allow the most suitable technology, prime mover and thermal energy storage unit size to be identified. From an energy point of view, the considered CHP systems usually satisfy most of the thermal and electric energy demand, with a primary energy saving index that is always higher than 20%. Moreover, the correct sizing of the thermal energy storage unit capacity proves crucial. As regards economic feasibility, it is shown that a reasonable target for the marginal cost of a CHP system for household heating is approximately 3000 €/kWe, even though the absence of incentives does not make any of the technologies very attractive at present. It is also shown that the highest profitability can be obtained by using the prime mover (i) with the lowest electric power output closest to that of the peak electric demand and (ii) with an electric-to-thermal ratio which fits the electric-to-thermal ratio of the users.