Improving the power share of waste-driven CHP plants via parallelization with a small-scale Rankine cycle, a thermodynamic analysis

Waste-fired CHP plants are largely contributing to the base load supply of heat and electricity sectors of several European countries. In such systems, about two-third of the production is heat and about one-third is electricity. In this study, the utilization of a certain portion of the heat production of a waste-fired CHP plant as the heat source of an Organic Rankine Cycle (ORC) is proposed. The main objective is to maximize the share of electricity production of waste-CHP plants instead of a higher heat production rate in a cost-effective way. The inspiration for this idea is that not only electricity is extremely more valued in most of the European energy markets, but also their heat sectors are to be occupied with efficient electricity-driven technologies, e.g. heat pumps. This work presents a detailed thermodynamic analysis of the proposed combined system and the best share of heat supply for driving the ORC unit is investigated. The results show that an electricity efficiency improvement of up to 25% is achievable via this integration while the heat production capacity of the power plant still remains significant. It is shown that the integration picks up of exergy efficiency of the power cycle.