An approach to energy saving assessment of solar assisted heat pumps for swimming pool water heating

A steady state off-design model of a Water Solar Assisted Heat Pump (W-SAHP) and the results of monthly-based averaged simulations are presented. The W-SAHP system is arranged with a commercial water- towater heat pump, coupled with unglazed flat plate solar collectors. The study is purposely developed for swimming pools, however most of the analysis criteria and outcomes are valid for any building (user) having hot water needs. Calculations are made for given thermal load and user operating temperatures with reference to the climatic data of all Italian Municipalities, that is degree days (DD) in the range from 700 to 3000, altitude from 0 to 1500m (above sea level), and latitude from 36.5\ub0N to 46.3\ub0N. The primary energy saving capability of the W-SAHP solution, compared to a traditional gas-boiler plant, is analyzed as a function of the DD index of each site. Despite the large spread of climatic and altitude data, the results show that the W-SAHP performance are usually well correlated to DD, which can therefore be assumed as the main independent variable for the energy saving assessment of these systems, and make the results easily extended to other possible geographical locations