With the growing woes of electricity costs in South Africa, engineering professional services consulting firm WSP | Parsons Brinckerhoff believes that it is imperative to keep up with air-conditioning technology trends that promote energy efficiency and ease of maintenance.
WSP technical director Pieter de Bod points out that WSP has been using heat recovery technology in its air-conditioning systems to reduce running and capital costs.
“We use heat recovery technology as it provides a special configuration of heat exchange between various air-conditioning equipment to save on operating costs.”
Since 2004, De Bod has been using heat recovery wheels on most of his projects. He notes that the wheels have a honeycomb structure, with holes about 1 mm in diameter. They are coated with a heat-retentive material such as silica gel, which has micropores ranging from 3 to 100 Angstrom and high absorption capacity. It absorbs moisture and odour molecules because of its strong hydrophilic characteristics. This means that smaller electrical supplies are needed to provide power for the air conditioner.
Lately, WSP has been recommending trigeneration power plant technology, which involves a sophisticated air-conditioning system that is powered by natural gas.
De Bod highlights that WSP has custom-designed two such plants locally – for mobile service provider MTN’s head offices in Fairland, and financial services provider Standard Bank’s head offices in Rosebank.
“Huge gas-driven power generators generate electricity from natural gas for these buildings at twice the efficiency, compared with a regular power station. The overall efficiency of coal power stations is 25% to 26% of the total energy supply, but a tri-generation power plant’s efficiency is 80%.”
The trigeneration power plant is unique because all the waste heat generated goes into an absorption chiller that converts heat into chilled water, De Bod adds, pointing out that it is similar to the principle that paraffin fridges are based on.
“Trigeneration power plants reduce the need for electricity from government and are energy efficient, with a low cost maintenance if done properly and frequently by experienced air-conditioning technicians,” De Bod says.
Such a plant also enables a company to register to claim carbon credits, since the plants are internationally recognised as clean green technology, he adds.
Projects in Progress
WSP is working on the PwC head office tower currently under construction next to the Mall of Africa, in Midrand. De Bod says that the project started in 2014 and will be completed by the end of this year.
“In this building, we’re installing high-quality water-cooled chillers and multifunctional chillers that recover heat or cooling using built-in heat exchangers. These convert hot air into cold air using heat exchange technology. The building is also equipped with an automated blind system that will control the blinds on all levels of the building,” he explains.
De Bod adds that the automated blinds have solar sensors that determine the time of day and the angle of the sun; these sensors automatically adjust the blinds to open or close to limit solar influx into the building.
Maintenance Is Key
De Bod emphasises the importance of frequent maintenance of air-conditioning equipment, citing that the heating, ventilation and air-condition system specified for PwC is made to last 40 years if it receives regular maintenance by skilled technicians using original-equipment manufacturer parts and following a preventive maintenance framework.
“We, as engineers, inform our clients upfront about the importance of having a proper maintenance plan in place. Once air-conditioning systems have been installed, we can check the systems on behalf of the client and report back to them as an added service. Frequent upkeep lowers the running cost of air-conditioning equipment, while maintaining a standard of sustained energy efficiency,” De Bod concludes.