Optimization-Based Reliability Assessment of Multi-Energy Systems

Multi-energy systems (MES) connect different energy networks using conversion technologies, leveraging alternative supply paths and redundancy to improve the integration of renewable energy, the reliability and the profitability of energy supply. This paper investigates MES reliability by integrating a pre- and post-failure operational optimization into a reliability assessment based on an alternating renewal process. Expected energy not supplied and uninterrupted supply times are used to quantify the MES’ ability to withstand failures of technologies, networks and external grid supply. The method is applied to a Swiss MES that supplies thermal and electrical energy demands of a mixed-use district. A comparison of system configurations with electricity- and gas-based conversion technologies, energy storage and distributed photovoltaic generation shows that both electricity- and gas-based MES are highly reliable due to the high reliability of the Swiss electricity grid. Introducing centralized battery storage and distributed photovoltaic panels further increases the probability of uninterrupted supply and decreases the expected energy not supplied. However, reliability is not always increased by introducing conversion technologies that couple energy carriers. In fact, heat pumps introduce a dependency of the heat supply on electricity, while combined heat and power plants can be less reliable than other technologies, thus increasing the expected energy not supplied.