Potential Analysis of Pumped Heat Electricity Storages Regarding Thermodynamic Efficiency
- Conference Paper
The rising share of renewable energy sources in power generation leads, due to increasing fluctuations, to the need of higher storage capacities. In this context, also some interest in pumped heat electricity storage (PHES) arises. The basic principle of such a PHES system is simple; in case of oversupply of energy to the grid, a thermodynamic cycle transfers electrical energy to thermal energy and charges the storage. In the event that less electrical energy is generated than consumed, a further thermodynamic cycle discharges the storage and converts thermal energy to electrical energy back again. Against the background that combining two Carnot cycles leads always to a roundtrip efficiency of 1, the maximum possible efficiency as well as important variables of such systems are nearly unknown, so far. In this context Thess , assuming a maximum power cycle, and also, equal charging and discharging times, derived an analytical expression for the roundtrip efficiency as a function of the heat source and heat sink temperatures. The present work also investigates two reversible cycles with irreversible heat transfer but analyses the roundtrip efficiency as a function of storage temperature, power output, thermal resistances (R=1/(U·A)) of the heat exchangers and relative charging and discharging time. From a thermodynamic point of view, an upper limit for the roundtrip efficiency is only found if restrictions like maximum power output are specified. Rather, power output and roundtrip efficiency lead to a Pareto frontier and a selection criterion must finally base on other, probably economic aspects. Regarding an exemplary storage temperature of 400 K, a reduction of the required power output by 10 % (relative to the maximum power output) already leads to a 40% increased roundtrip efficiency and results in a much better evaluation of the theoretical potential of PHES systems. Show more
Book title30th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2017)
Pages / Article No.
SubjectFinite-time thermodynamics; Heat transfer; Pumped heat electricity storage; Thermodynamic limits
Organisational unit09696 - Bardow, André / Bardow, André
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