Exploring the potential synergy between micro-cogeneration and electric vehicle charging

Abstract The economic viability of micro-cogeneration (micro-CHP) systems strongly depends on the value of the co-produced electricity. In case electricity produced by the micro-CHP is used inside the house (‘behind the meter’), the electricity has the same value as the price otherwise paid to the utility. If the electricity cannot be used inside the house and needs to be exported to the grid, it generally has a much lower value. For jurisdictions that do not have an active support for micro-CHP, this value could range from zero to at most the whole-sale market price. The primary function of most micro-CHP systems applied in residences is to provide heat for space heating and sometimes also for domestic hot water. The micro-CHP system generally operates under a heat-load following control strategy, which causes the system to run more in winter and during the night. A large fraction of the electricity is thus produced at times when the electric load of the house is low, requiring substantial amounts of electricity to be exported with low or zero revenues. Electric vehicles (EVs) consume considerable amounts of electricity. EVs are mostly driven during the day and charged at home during the night. The recharging of EVs could thus be a way to drastically increase the own use of electricity produced by the micro-CHP and to boost the profitability of the system. A simulation study was performed to explore the potential synergy between electric vehicles and micro-CHP systems by combining the results of the whole building simulation program TRNSYS and NRCan's Plug-in Electric Vehicle – Charge Impact Model (PEV-CIM). Detailed measured profiles of residential electricity consumption were used to determine the economics of a micro-CHP system applied in a single detached house in Ottawa, Ontario, Canada. EV charging showed to have a great potential to improve the profitability of micro-CHP systems. Level 1 charging significantly reduced electricity exports and created substantial additional micro-CHP revenues of $200–$300 per year for common daily driving distances. Significant economic benefits were found over the full range of residential non-HVAC electricity consumption, clearly proving the robustness of the concept and the existence of a strong synergy between micro-cogeneration and overnight electric vehicle charging.