Testing and preliminary modelling of a 2.5 kW micro-CHP SOFC unit

The experimental activities, carried out at the Laboratory of Micro-Cogeneration (LMC) of the Department of Energy at Politecnico di Milano are hereby outlined in relation to the testing of four 2.5 kWel AC SOFC-based micro-CHP units developed by SOLIDpower S.p.a. The novelty of the work consists in carrying out a complete thermodynamic and environmental performance characterisation of the studied commercial system in a third-party laboratory. The main objectives of the experimental campaign have been the investigation and assessment of the electric and heat recovery performances in different cogeneration thermal power demand loads. The generator has been tested in five different thermal loads, whilst operated at full electric load, in order to simulate the coupling with thermal appliances of diverse nature. The cogeneration water inlet temperature has been varied from 20°C (as in more complex cogeneration systems which may envisage a thermal storage and additional pre-heating section) to 50°C (as for district heating purposes or heating of sanitary water). Each measurement has been acquired with a redundant approach for statistical purposes aiming to the reduction of uncertainty and to guarantee procedure robustness. Moreover, the design point experimental characterisation has been supported by an overall process calibration and simulation performed by means of an in-house software (GS), developed at the Department of Energy. Each component has been modelled using a 0D approach, such that the required mass and energy balances of the plant can be compared with those obtained from the experimental activity. In conclusion, the overall performances have met the expectations, being characterised by a net electric efficiency of approximately 39% and a total efficiency which may overcome 95%.