Experimental investigation of a Scroll unit used as a compressor and as an expander in a Heat Pump/ORC reversible unit

This paper presents an innovative system comprising a heat pump connected to a solar roof and a geothermal heat exchanger. This heat pump is able to invert its cycle and operate as an ORC. By using the whole rooftop (hereunder called “absorber”) as a heat source, a large amount of heat is generated throughout the year. This heat is used in priority to cover the building annual heating needs, while the surplus heat (mainly during summer months) is utilized to generate electricity in the so-called HP/ORC module. The same module can be used in winter time as an efficient heat pump which radically simplifies the complexity of the total system compared to competitive products. The main advantage of the proposed technology is related to the reversibility of scroll machines, which have proven to operate efficiently both as a compressor and as an expander. This paper focuses on three aspects: design of the prototype, results from experiments and validation of models based on the experimental data. To size the unit, the expander and the different exchangers are modeled thanks to semi-empirical correlations calibrated on experimental data. The sizing of the prototype is based on yearly simulations with a simulation step of one hour. The algorithm optimizes the operating mode based on the domestic heat demand, the meteorological conditions and the available heat in the storage. This paper demonstrates the feasibility of such a prototype with promizing experimentally-achieved performance (4.1% overall efficiency in ORC mode and a COP of 4.2 in HP mode