In South Africa, a significant amount of electrical energy is used for air conditioning in commercial buildings, on account of the high humidity experienced. Due to its geographical location, the levels of solar irradiation and the demand for air-conditioning of commercial buildings reach maximum levels simultaneously. The South African region daily solar radiation average varies between 4.5 and 6.5 kWh/m2 and when compared to the United States 3.6 kWh/m2 and Europe’s 2.5 kWh/m2 , solar thermal powered cooling technologies has significant potential as this solar irradiation is also available all year around [1]. Utilizing solar energy for an air conditioning system has the advantage that the availability of solar radiation and the need for cooling reach maximum levels simultaneously and proportionally. This type of air conditioning system has an electrical energy saving benefit in light of increasing energy tariffs and the energy crisis currently facing Eskom in South Africa. Solar-assisted Absorption Cooling systems decreases the peak electricity consumption, is less noisy and vibration free, since it does not contain a compressor and this gives a higher reliability, low maintenance and its electricity consumption is approximately four times less (21.8kW versus 5.5kW for 35kW of Cooling) than that of an electric driven chiller containing a mechanical compressor [2]. However, due to the high capital cost of solar powered air-conditioning plants, it is essential that a feasibility analysis be undertaken to indicate and establish a return on capital investment. The main objective of the present study is to investigate and establish the feasibility of a solar-assisted air-conditioning system based on Lithium Bromide and Water (LiBr/H2O) absorption chillers on a medium scale for commercial buildings in terms of energy saving and performance. This study presents the results of the experiment on a solar-assisted air-conditioning facility constructed and installed in October 2009 at Pretoria’s Netcare Moot Hospital. This study has confirmed that a payback period of 13 months can be achieved and the performance parameters of the manufacturer’s specifications for a solar-assisted air conditioning system are exceeded for the South African climate. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

Increased standards of living and indoor comfort demands have led to an increase in the demand for air-conditioning in buildings in South Africa. Conventional vapor compression systems use refrigerants that damage the ozone layer and contribute significantly to the global warming effect. Therefore, there is an urgent need to implement environmentally cleaner ways of satisfying this air-conditioning demand and absorption cooling systems have shown great potential to do so. This project is concerned with finding the technical and economic effectiveness of solar powered absorption cooling systems for South African climatic conditions. Solar cooling systems are made up of a solar collector array, water storage tank, absorption chiller and cooling tower for heat rejection. In this study, two complete systems, one utilizing an open wet cooling tower and another using a dry cooler were studied and their technical and economical performance analyzed. One system was installed at Netcare Moot Hospital in Pretoria and comprised of a solar collector array made up of 52 evacuated tube collectors, two 6000 litre hot water storage tanks, 35kW LiBr-water absorption chiller, and a wet cooling tower. This system was coupled to an existing vapor compression chiller so that cooling is provided even when no solar energy is available. The installation controlled and remotely monitored through the internet and parameters logged through a Carel Building Management System. The other system is at Vodacom World in Midrand, Johannesburg and is an autonomous solar heating and cooling system aimed at maintaining the building environment at comfort conditions throughout the year. It is made up of a 116m2 evacuated tube collector array, a 6500litre hot water storage tank, 35kW LiBr-Water absorption chiller, 1m3 of cold water storage, a dry cooler for the chiller, and two underground rock storages to pre-cool the supply air to the building and the dry cooler respectively. Long term system performance studies were carried out by varying the system control strategy for the chiller, hot water storage tank, existing vapor compression chiller (in the case of the Moot Hospital installation), hot water storage tank, dry cooler (for the Vodacom installation) and the system Coefficient of Performances were calculated and life cycle cost analysis carried out. Due to the fact that solar availability and cooling demand are approximately in phase, solar powered absorption cooling presents a great opportunity for reducing peak electrical cooling energy demand. It was also discovered that the economic effectiveness of the system increases with the absorption chiller capacity, and it‟s more advisable to operate the solar absorption cooling system with a vapor compression chiller as a backup for facilities that require uninterrupted cooling. The solar autonomous system is oversized for most of the year since it is designed to cover the peak cooling loads. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.