Fuel partialization and power/heat shifting strategies applied to a 30 kWel high temperature PEM fuel cell based residential micro cogeneration plant

• Mathematical modeling of an HT-PEMFC based micro CHP plant is developed and explained.
• Three different strategies have been proposed for partial load operation of the plant.
• The performance of the system using different strategies are represented and compared.
• Fuel partialization leads to electrical efficiency increment and thermal efficiency decrement.

The present study is dedicated to the investigation of applying different strategies on an HT-PEM fuel cell based micro cogeneration plant in order to evaluate the capability of this system to cope with intermittent electrical and thermal load profiles. The performance of the system under fuel partialization strategy is first studied and the thermal and electrical efficiencies of the plant at different partial loads are determined. It was found that due to partialization of the fuel down to 50% of the initial value, the electrical efficiency increases from 29.3% to 33.6% while the thermal efficiency decreases from 53.0% to 47.6%. Power to heat shifting strategy, as a faster approach, is then employed in which, by altering the anodic stoichiometric ratio, the electrical generation is decreased while higher thermal power is produced. The results showed that this partialization method leads to harsh drop, around 13%, in the electrical efficiency of the plant. In the last analysis, the previous strategies are combined and the power to heat shifting approach is implemented on the system operating at partial load. The main advantage of the last strategy is the flexibility of the system in covering a wide range of thermal demand.