Energy system design for deep decarbonization of a sunbelt city by using a hybrid storage approach

With continuously falling cost of renewable power generation and ambitious decarbonization targets, renewable sources are about to rival fossil fuels for energy supply. For a high share of fluctuating renewable generation, large-scale energy storage is likely to be required. In addition to selling electricity, the reliable supply of heat and cold is a further interesting revenue pool, which makes hybrid storage technologies an interesting option. The main feature of hybrid energy storage – as defined here is to offer charging and especially discharging in different forms of energy by combining different charging, discharging and storage devices. They can address various demands (e.g. electricity and cold) simultaneously. Two hybrid storages, pumped thermal energy storage (PTES) and power-to-heat-to-x (x: heat and/or electricity) energy storage (PHXES), are investigated based on a technoeconomic analysis within this work. Both hybrid storage technologies are charged with electricity and can supply heat and electricity during discharging. They are implemented into a simplified energy system model of a prototype city in the earth’s sunbelt in the year 2030 to find a cost-optimal configuration. Different cases are evaluated: a power-to-power case (P2P), where only an electric demand must be addressed and a power-topower-and-cooling (P2P&C) case, where the electric demand from the P2P case is divided into a residual electric demand and a cooling demand. For both cases, a natural gas-based benchmark scenario and a decarbonized, renewable-based scenario including the hybrid energy storage technologies are calculated. Both, total expenditures and CO2 emissions are lower in the P2P&C scenarios compared to P2P scenarios. PHXES plays a major role in both cases. PTES is part of the costoptimal solution in the P2P&C decarb scenario, only if its specific cost are further decreased. Keywords—Hybrid energy storage, Energy system modeling, Decarbonization