Energy Integration and Analysis of Solid Oxide Fuel Cell Based Microcombined Heat and Power Systems and Other Renewable Systems Using Biomass Waste Derived Syngas

Abstract

The objective of this paper was to design energy integrated solid oxide fuel cell (SOFC) based microcombined heat and power (micro-CHP) systems using syngas derived from lignocellulosic biomass waste. The novel contributions of this work include (1) integration of syngas between a community-scale biomass gasification plant and SOFC-based micro-CHP systems in buildings; (2) heat integrated designs of SOFC-based micro-CHP systems; and (3) integration between SOFC and other heat-led renewable technologies, such as, syngas boilers, ground source heat pump (GSHP), and air source heat pump (ASHP). Conceptual process design frameworks including detailed heat recovery strategies were developed using Aspen plus. It is demonstrated that increases in heat integration between the SOFC inlet and outlet gases enhance the power-to-heat generation ratio from the SOFC, albeit at a higher cost of heat exchanger area. A straw (14.6 MJ/kg LHV) based community-scale gasification plant can generate 50−100 kWe of electricity at an overall CHP generation efficiency of ∼42%, while if integrated to SOFC-based micro-CHP systems (1 kWe) in individual dwellings via syngas, the overall energy efficiency can be greatly enhanced to ∼85%. It is envisaged that the SOFC should be operated at the highest electrical efficiency based on optimal heat integration; however, this needs to be coupled to other heat-led renewable technologies in order to meet the high residential heat to power demand ratio in the UK. Around 2.2 times more syngas may be required in boilers for supplementing residential heating. In integration with a GSHP loop, the flue gas from SOFC can itself be used as a refrigerant, and energy integration between the two systems can achieve an overall efficiency of ∼90%.