Exploitation of humid air latent heat by means of solar assisted heat pumps operating below the dew point Federico Scarpa * , Luca A. Tagliafico University of Genoa, DIME/TEC, Division of Thermal Energy and Environmental Conditioning, Via All'Opera Pia 15 A, 16145 Genoa, Italy (*) corresponding author - email: fscarpa@ditec.unige.it - Fax +39 010311870 (2016) Applied Thermal Engineering, 100, pp. 820-828. DOI: 10.1016/j.applthermaleng.2015.12.077 Abstract Nowadays, the exploitation of environmental exergy resources for heating purposes (solar energy, convection heat transfer from ambient air, moist air humidity condensation) by means of properly designed heat pump systems is a possible opportunity. In particular, the use of solar assisted heat pumps (DX-SAHP) is investigated in this study, when a bare external plate (the solar collector) is kept at temperatures lower than the dew point temperature of ambient air, so that condensation takes place on it. The potential of this technology is settled and an instrumented prototype of a small DX-SAHP system is used to verify the actual performance of the system, in terms of specific thermal energy delivered to the user, efficiency and regulation capabilities. Results clearly show that the contribution of the condensation is significant (20% - 30% of the total harvested energy) overnight or in cloudy days with very low or no solar irradiation, and must be taken into account in a system model devoted to describe the DX-SAHP behavior. By investigating along these lines, the heat due to condensation harvested by the collector is found to be a function of the dew-point temperature alone. Keywords: Solar thermal; heat pumps; bare panels; vapor content; dew point; relative humidity 1