Development of a micro-cogeneration laboratory and testing of a natural gas CHP unit based on PEM fuel cells

This work discusses the design and the development of a Laboratory of Micro-Cogeneration (LMC) at Politecnico di Milano. The LMC laboratory is a unique structure devoted to small-scale power generation, with the main goals of testing and improving the performance of systems that produce or utilize electric and thermal (hot and/or cold) power in a very general sense, spanning from combined heat and power (CHP) units to heaters, from absorption chillers to heat pumps, but also able to perform tests on fuel processors and electrolyzers. The laboratory features a supply of natural gas as well as H2 and O2 from a high pressure electrolyzer and of CO, CO2 and N2 from bottles, permitting to carry out experiments with simulated synthesis fuels. The maximum allowable electrical power produced, exported to the grid or to an electronic loadbank, or consumed by the system under test is 100 kW; maximum allowable thermal power is roughly 200 kW with variable temperature water circuits (from chilled water up to a 150 °C at 8 bar superheated water loop). This work outlines also the instruments used for on-line recording of thermodynamic properties, emissions and power, aiming at monitoring and reconstructing mass and energy balances. the first experimental campaign has been carried out on a CHP system based on polymer electrolyte membrane fuel cells (PEM), a promising candidate for distributed CHP thanks to low pollutant emissions and good efficiency, rapid startup and flexibility, although affected by a rather complex fuel processing section to provide the appropriate fuel to the PEM. This work presents the experimental analysis of a 20 kW prototype PEM CHP system complete of natural gas processor. The prototype is operated at LMC to characterize the processing section and the thermodynamic performances of the overall system. Despite its non-optimized layout, the unit has shown encouraging total efficiency (76%) and primary energy saving index (6%).