The photovoltaic thermal (PV/T) driven desiccant air cooling process could be a good solution to the conventional air cooling cycle in terms of energy saving, where the latent cooling load would be removed adiabatically. However, problems exist where the required desiccant regeneration temperature (60oC - 80oC) often exceeds the outlet fluid temperature from standard PV/T collectors. In addition, operating the PV/T collector at high temperature reduces its electrical performance and lifetime. This study presents a desiccant air cooling process coupled with PV/T water heating cycle and a ground coupled cooling cycle which solves the above limitation. The inclusion of the ground coupled cooling increased the inlet air relative humidity and reduced the required regeneration temperature.
It was found that the required regeneration temperature increased with higher inlet air temperature and specific humidity for both conventional and ground coupled desiccant cooling cycle with pre-cooling. In comparison to the conventional desiccant cooling process, the ground coupled desiccant cooling process had lower regeneration temperature requirement and would be less affected by the inlet air conditions. Furthermore, low water flow rates would be preferred with higher outlet fluid temperature to suit the desiccant regeneration.
With defined thermal coefficient of performance (COP) and solar fraction (SF) as the main performance indicators, this ground coupled PV/T desiccant air cooling cycle was simulated under the Sydney summer climate condition in January. The results showed that the ground coupled PV/T desiccant cooling process could supply air temperature ranged between 21o C to 23o C with a constant designed specific humidity of 0.008 kg/kg. Furthermore, the climate conditions would strongly affect both the thermal COP and the solar fraction, thus auxiliary heating would be needed.