The new, innovative district cooling (DC) plant for the faculty of engineering at Stellenbosch University was visited when facilities management professionals from all over South Africa came together for the annual HEFMA Conference in Stellenbosch, Western Cape.
HEFMA – Higher Education Facilities Management Association – represents the interest of the facility management department of 27 universities in and outside South Africa and develops and maintains high quality standards in the facilities management of the physical infrastructure of campuses.
David Lombard, managing director of leading mechanical and electrical consulting firm Lombard Consulting Engineers (LCE), hosted the delegates on the site tour to the DC plant. The engineering team of LCE designed and implemented this advanced DC system, which is being constructed in phases. They have been working on this project since 2020 and the final phase is set to be completed in 2024.
The DC plant connects all the faculty’s buildings to one centralised chilled water plant and consists of a four-pipe chilled water and heating hot water reticulation network, meeting both cooling and heating demands.
Lombard says the system provides the buildings with conditioned water and “therefore the buildings do not need their own dedicated cooling and heating plants, split systems or cooling towers.” He adds, “The energy network is achieved via chilled water pipes connecting the engineering campus buildings with one another along the spine of the building complex (main connecting corridor).”
Some of the advantages of using one large plant (6 000 kW) include the following:
- The opportunity to install larger, highly efficient chillers with a tailor-made plant to suit the energy needs of the engineering faculty. It reduces peak demand as well as overall electricity consumption. Chillers can achieve full load COPs of 6.8 to 13 at part-load.
- Less equipment will be needed and is located in one area, making maintenance easier and more cost-effective.
- The life expectancy of a central plant is much longer than that of unitary equipment, giving a long-term reduction in the replacement cost of equipment.
- Winter peak shifting via hot water storage tanks.
- The high-efficiency centrifugal chillers (Carrier 19DV) use Hydrofluoroolefin (HFO) refrigerant gas, which has zero Ozone Depleting Potential (ODP) and very low Global Warming Potential (GWP), which makes this chiller plant more environmentally friendly.
Lombard says they also planned carefully around the Time-of-Use (TOU) electricity tariffs. “In winter, the peak tariff is six times more than the off-peak tariff. Heating hot water is generated during off-peak tariff times and stored in insulated tanks for later use during peak tariff times. This process of ‘shifting the peak’ greatly reduces electrical consumption during peak tariff times and translates directly to cost savings on electricity,” he concludes.