A new thermal-hydraulic process for solar cooling

Air conditioning is usually realized by electricity-powered mechanical vapor compression cycles. However, during the summer the demand for electricity increases drastically because of the extensive use of these systems. This paper presents a novel and innovative solar cooling process (so-called CHV3T) for air-conditioning for individual buildings using common flat plate collectors. The principle of the process is based on an original coupling between two dithermal thermodynamic cycles. The engine cycle and the reverse cycle, which are respectively a Rankine-like cycle and a reverse Rankine cycle, use their own working fluid (HFC's) and their performances are close to Carnot cycles. The coupling of these dithermal cycles allows obtaining a global tri-thermal system with an internal work transfer realized by an inert liquid LT which plays the role of a liquid piston. This new system appears as an attractive alternative for solar cooling technologies due to its ability to use low temperature driving heat source. Several versions of the thermo-hydraulic system has been investigated in order to obtain the best cost-effective compromise for an individual building application. A modelling of a solar process coupled with 20 m² of flat plate solar collectors and providing 5 kW cooling capacity is developed by using the concept of Equivalent Gibbs Systems. This method, issued from thermodynamics of irreversible processes is applied here to describe the dynamic behaviour of all the components of the system. This model allows determining the performances of the machine on the stationary and non-stationary regimes. The pressure, temperature and thermal powers evolutions are observed during the cyclic operating in all the components of the system. The performances seem to be very competitive with existing solar cooling systems. A 5 kW cooling capacity prototype is under construction and will be in operation during the next summer.