Dynamic simulation of an integrated solar-driven ejector based air conditioning system with PCM cold storage

- A TRNSYS simulation of a SECS with PCM cold storage unit was performed.
- The ejector and steam generator were modelled using Fortran and EES.
- Only a small hot storage tank is recommended for high solar fraction.
- PCM cold storage offers an immediate energy supply and stable system operation.

The development of a dynamic model using the TRaNsient System Simulation program (TRNSYS) for the performance assessment of a solar-driven air conditioning system with integrated PCM cold storage is presented. The simulations were carried out for satisfying the cooling needs of a 140 m3 space during the summer season in Tunis, Tunisia. The model is composed of four main subsystems including: solar loop, ejector cycle, PCM cold storage and air conditioned space. The effect of varying the solar collector area (Asc) and the hot storage capacity (Vhs) on the solar fraction are investigated. It was found that the application of a relatively small hot storage tank (700 l) led to the highest solar fraction (92%). A collector area about 80 m2 is needed to assure a solar fraction of 70%. Increasing Asc beyond this value has only a small effect on the overall system efficiency. The influence of applying cold storage is also investigated. The results without cold storage indicated that the comfort temperature was exceeded in more than 26% of the time. With cold storage the periods of high indoor temperatures reduced significantly. An optimal storage volume of 1000 l was identified resulting in the highest cooling COP and excellent indoor comfort (95% of the time with a room temperature below 26 °C). The maximum COP and solar thermal ratio (STR) were 0.193 and 0.097, respectively.