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Performance Evaluation of a HP/ORC (Heat Pump/Organic Rankine Cycle) System with Optimal Control of Sensible Thermal Storage

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Abstract

In energy systems with high share of renewable energy sources, like wind and solar power, it is paramount to deal with their intrinsic variability. The interaction between electric and thermal energy (heating and cooling) demands representa potential area for balancing supply and demand that could come to contribute to the integration of intermittent renewables.This paper describes an innovative concept that consists of the addition of an Organic Rankine Cycle (ORC) toa combined solar system coupled to a ground-source heat pump (HP) in a single-family building. The ORC enables the use of solar energy in periods of no thermal energy demand and reverses the heat pump cycle to supply electricalpower. A dynamic model based on empirical data of this system is used to determine the annual performance. Furthermore, this work assesses the benefits of different control strategies that address the critical concern that thermal supplyshould always operate considering the actual load conditions in the overall system performance. The performance is assessed in terms of energy efficiency of the system, the integration of renewable energy in the energy supply of thesystem and the level of comfort of the users. Results show that real load control logic can lessen the adverse effects ofcycling in the compressor of the system as well as increase the thermal demand (up to 33%) and the electrical demand (max. 8.4%) covered by renewable energy (solar). However, the extension of these improvements is highly dependenton the thermal mass of the building and the volume of the sensible storage.