A showcase project to prove the efficacy, efficiency and economic viability of commercial solar driven air-conditioning has been implemented in Pretoria, South Africa.

It is an interesting paradox of South Africa's sunny climate that the very source of heat, which necessitates cooling in buildings can in turn, be utilized to cool the buildings. 

The project, currently underway in Pretoria utilizes absorption chiller technology and aims to define a new method of cooling buildings in Southern Africa.

Voltas Technologies, a Johannesburg-based company that specializes in solar technology products, is the South African importer and distributor of the absorption water chillers, which are produced by Yazaki, a Japanese company. According to Cristian Cernat, CEO of Voltas Technologies, the use of absorption cooling technology has reached an acceptable level of process stability and its use is highly recommended.

“New innovative absorption chillers are now available,” says Cernat. “The newly developed chillers are suitable for use with low hot water (less than 90°C) temperatures. This characteristic makes them a very interesting application for systems based on wasted/recovered heat or solar heating systems. In South Africa, few absorption systems have been implemented and as far as we know, none has been solar power driven.”

Finding a host for the project
After months of negotiations with different entities trying to find a host for the showcase plant, Cernat approached a long-time client, Netcare Hospitals Pty Ltd. Netcare Hospitals agreed to provide Voltas Technologies with sufficient roof space and the opportunity to install and operate the system in parallel with the existing air conditioning plant at one of their facilities – the Moot Hospital in Pretoria.

“In order to demonstrate the economics and the operating characteristics of absorption cooling systems in South African conditions, Voltas Technologies, in partnership with several reputable solar installers, installed the solar chiller plant,” says Cernat. “The plant, known as the 'First Solar Thermal Driven Chilled Water System' (STDCHW) is a first in Southern Africa. The STDCHW is a showcase project, with a 35 kW cooling capacity, based on the Yazaki WFC 10 chiller and a number of solar collectors for a heat source on the roof of the Netcare facility. The installation will produce chilled water, utilizing the cooling agent in the building's air conditioning system, by deploying a thermally driven absorption cycle-based chiller unit in lieu of an electrically driven compression chiller. Thus, solar thermal energy can be used to efficiently cool in the summer, and heat domestic hot water and buildings in the winter.”

Upgrading the system to 200 kW nominal cooling
The installation of the solar driven air-conditioning system is being carried out in two phases. The first phase, already completed, consisted of the installation of an absorption based system, 35 kW nominal cooling capacity complete with a dual storage system and full monitoring as well as a web accessible bms system. Conclusive data was collected and the heat source/cooling ratio was confirmed. The second phase, currently underway, involves upgrading the system to 200 kW nominal cooling capacity. 

“Our project tasks include the calculation and validation of the relation between the cooling capacity of the chiller and the solar absorption area where evacuated tube collectors, 'U-tube' and 'heat-pipe' types are used; the calculation and validation of the minimum thermal storage required in order to ensure a 12 hour operation of the system; and the measurement and verification, both in-house and by a third party, of the electrical energy saving associated with this type of air conditioning system. A feasibility study of the implementation proven 'life' will be carried out by using the acquired data,” says Cernat. Data from this project is currently being collected and monitored for later analysis.

“The project will enable Voltas Technologies to establish a real baseline for consumption so that eventual savings can be presented in perspective.”

For more information, visit www.voltastechnologies.co.za, to which full acknowledgement and thanks are given.