Analysis of the operation and performance of a solar cooling system

Abstract

Significant research is being carried out in the field of renewable energy to develop and improve current technology to reduce or eliminate the dependence on fossil fuels. Such developments include the use of solar cooling systems to provide process or space cooling in diverse industrial processes. A solar cooling system was funded through the Italia-Malta Interreg program. It consists of an ammonia-water vapour absorption chiller and evacuated tube collectors was installed at the Buskett Research centre for Viticulture and Oenology to provide chilled water for wine temperature control during fermentation. The solar collectors generate the required thermal energy for the chiller to operate. One of the objectives was to evaluate the performance and observe the operational characteristics of this solar powered cooling system. These were collected through extensive experimentation sessions both prior and during the fermentation period. Moreover, an extensive literature review was carried out on steady-state and transient modes of operation and its application across the wine industry to determine those factors that have a direct impact on the operational performance of such systems. From the review, it resulted that several configurations and control strategies can be applied to achieve the optimal performance for the various ambient conditions. During the first experimental runs, the solar cooling system could not operate in high solar radiation conditions. The evacuated tube collectors generated thermal energy beyond the required yield causing over-heating of the working fluid, which for this system is water. In this scenario, the system had to be switched off to allow the water to change phase back to liquid and the pressure to return to the nominal value. The solar collector arrays were significantly upgraded to improve the overall performance of the solar cooling system. The system was then tested rigorously across the summer months. Data measured during two distinct experimentation sessions is presented in this dissertation. In the initial runs, the system was unable to operate in high solar radiation conditions which impeded the wine fermentation process. After the experimentation, the system can operate uninterrupted while being remotely monitored, positively impacting the process.