Techno-economic assessment of a small-scale biomass ORC-CHP for district heating

Abstract

The present work focuses on the techno-economic assessment of a small-scale (1000 kWth) biomass-fired Organic Rankine Cycle (ORC) plant for combined heat and power (CHP) generation coupled to a district heating network. The ORC is designed to maximize its nominal installed power for several natural refrigerants and R1233zd. A part-load model is developed to determine the plant’s annual electrical energy and heating output when covering the heating loads of energy-efficient buildings of communities of various sizes in three cities representing the main climate zones of Europe, namely Athens, Berlin and Helsinki, with a peak load of up to about 10,200 kWth. A series of parametric analyses are carried out to investigate the plant cost-effectiveness under different assumptions. The plant’s economic performance is very low, as only under the combined existence of multiple favorable factors (high electricity and heat prices, low biomass cost) and long operating hours it is possible to achieve discount payback periods of at least 5–7 years. Three factors that result in the unsatisfactory economic performance of the plant are its high specific cost, reduced operating hours and reduced electricity production, which is caused by the maximum temperature limitation of screw expanders at the investigated scale.