Abstract
Storage of electricity from fluctuating renewable energy sources has become one of the predominant challenges in future energy systems. A novel system comprises the combination of a heat pump and an Organic Rankine Cycle (ORC) with a simple hot water storage tank. The heat pump upgrades low temperature heat with excess power. The upgraded heat can drive an Organic Rankine Process using the heat pump in reverse operation mode. This approach allows a comparably efficient storage of excess electricity. Waste heat sources usually do not qualify for electricity production even with ORC processes due to low temperatures. Upgrading the temperature of the waste heat by means of excess electricity makes the use of an ORC feasible in order to recover the electricity input. Thermodynamic cycle simulations with IPSEpro software outline that the process provides power-to-power efficiencies in a range of 50% for small-scale applications based on commercially available heat pump components. The isentropic efficiency of compressors/expanders plays a crucial role on the system performance. Applications of the proposed cycle in the megawatt range with more efficient turbines and dynamic compressors will therefore increase the power-to-power efficiency to above 70%.
Highlights
Storage of renewable energies from fluctuating sources needs storage technologies with quite different characteristics
Systems with thermal losses storage of a heat engine operating at low temperatures
More competitive efficiencies are achievable if the excess power is used to operate a heat pump which upgrades a certain amount of heat Q to the heat storage system
Summary
Storage of renewable energies from fluctuating sources needs storage technologies with quite different characteristics. More challenging in terms of efficiency and CO2 savings is the task that requires the storage of solar power from noon peaks in order to shift this energy to evening and night periods Such storage systems have to operate on a daily basis nearly continuously with a high number of operational hours. Anstorage advancement of Dumonts set-up the use ofsystem a single for volumetric machineuse of renewable energy solar or biomass) based an ORC and a heat pump withsystem a separate to reduce the(e.g., complexity and equipment cost.on. Use of renewable energy (e.g., solar or biomass) based on an ORC and a heat pump with a separate expander and compressor [35] has been tested and validated at the NTUA labs in Athens
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