A comparative study of solar cooling technologies

Abstract

The environmental impacts of refrigeration and air conditioning applications include synthetic refrigerant fluids use and the high demand for electrical energy for activation, being critical in places whose energy mix depends on fossil fuels. Brazil has advantages due to hydroelectricity and the high incidence of solar irradiation, enabling solar energy technologies in refrigeration cycles. This work aims to study the technical-economic feasibility of photovoltaic energy to drive the vapor compression refrigeration system, and solar thermal energy for the ammonia-water and water-lithium bromide absorption cycles. It developed thermodynamic models of both vapor compression and absorption cycles using the mass and energy conservation equations under steady-state regime. The systems of linear equations were solved by using the Engineering Equation Solver - EES. One obtained the air conditioning thermal load profile and the characteristics of the thermal collectors and photovoltaic panels from EnergyPlus, from São Paulo-Brazil solar irradiation. Results showed that the monthly energy consumption is reduced from 626 kWh to 196 kWh, achieving a 44% reduction in the value of the electric energy bill for the photovoltaic solar cooling proposed when compared to the conventional one. A 7-years payback time is achieved. For the absorption cycle, the use of a flat thermal collector is unfeasible due to the need for natural gas as a complementary source of energy. It is concluded that solar cooling with photovoltaic has advantages compared to thermal activation, as the overall efficiency has a performance 30% higher than solar cooling by the
thermal collector. Results showed that PREUPV is always higher than PREUST.