Performance optimization of solar driven small-cooled absorption-diffusion chiller working with light hydrocarbons

We present in this paper a HYSYS (Aspen One) model and simulation results for 1 kW capacity water-cooled absorption/diffusion machine using different binary mixtures of light hydrocarbons as working fluids (C3/n-C6, C3/c-C6, C3/c-C5, propylene/c-C5, propylene/i-C4, propylene/i-C5) in combination with helium as inert gas. The driving heat is supposed to be provided by an evacuated solar collector field. TRNSYS is used to address the solar aspects of the simulations. For the optimal chiller the driving heat temperature was found to be 121 °C for an evaporator exit temperature of 0 °C. The cooling water flow rate circulating between chiller and cooling tower is 140 l/h. Bubble pump and generator are heated by pressurized water from an insulated tank (70 l/m2) maintained at a maximum temperature of 126 °C - with make-up heat when needed - and storing solar heat at an estimated 4.2 kW power. The solar energy cover only 40% for the energy supplied to drive the chiller. It's found that the necessary collector surface area is about 6 m2 with annually total costs of 1.60 €/kW h with 20 years lifetime period for the installation. The avoided CO2 emissions are estimated at 1396 kg. The equivalent saved energy is 521 l of diesel or 604 l of gasoline.