Since only part of the return fluid stream of the chilled water is cooled by the solar driven absorption chiller, the influence of the system performance of the quantity of this mass flow rate was investigated. Because the mass flow on the “cold side” was more or less fixed due to the flow rate required by the absorption chiller only the “hot side” flow rate, which is the side of the chilled water of the existing system, was changed. Three different mass flow rates were simulated: 2000, 3000 and 4000 kg/h. Results are presented, in fig. 12 and fig. 13, for the systems with 2 m3 storage volume and varying number collectors. As expected the solar fraction SF as well as the total system performance increases with higher flow rates on the “hot side” of the heat exchanger (see fig. 12).

This is because the storage can be discharged faster (with larger temperature differences) in discharge mode. Moreover the chiller performs better in direct mode due to the higher inlet temperatures in the evaporator heat exchanger (i. e., less part load operation). Increasing the mass flow rate from 2000 kg/h to 4000 kg/h results in increment of about 1% of the solar fraction for a specified number of collectors, However, higher flow rate means larger pump, higher costs and

electricity consumption. And thus, a middle value of 3000 kg/h was selected as the flow rate for the cold side of the system.