Solar assisted hybrid cooling for high efficient buildings in warm climates: development and experimental testing

In this paper the activity carried out so far within the H2020 project ZeoSol is introduced. An advanced solar cooling and heating system integrating an adsorption chiller and an electric heat pump is being developed. The hybrid system proposed consists of a thermal and an electric unit, capable to operate in parallel. In this configuration, the evaporators of both units are connected to the chilled water circuit and the process heat of both is rejected in the ambient by means of a high-performance dry-cooler. The "ZeoSol" system is based on a commercial unit produced by Fahrenheit and it has a nominal power of 20 kW, but it was optimized with the target or reaching an ESEER of at least 12. Moreover, in order to simplify the design of the solar cooling system, a sizing tool was developed. Input for the sizing tool are the achievable thermal power of solar collectors, as a function of ambient temperature obtained through dynamic simulation, the efficiency of the thermal and electric units and the consumption of auxiliaries as a function of part loads. The methodology implemented can then be easily re-used for the definition of standard sizing procedures. The hybrid chiller unit, complete with an advanced V-shape dry cooler, is under testing in the laboratories of CNR ITAE. The first tests are aimed at assessing the reliability of operation under different part loads. The first results confirm that the target ESEER of 12 can be reached for an optimal control strategy (the thermal chiller only is operated at 25% and 50% part load while electric unit only is operated for 100% part load conditions).