20 November 2012 – At Gateway Theatre of Shopping in KwaZulu-Natal, energy tariffs skyrocket when power consumption exceeds the notified maximum demand (NMD). Since August 2011, however, power consumption has been closely monitored and managed, a move that will save property owners Old Mutual Property (OMP) a considerable amount in energy costs a year.
Gateway is one of the most prestigious shopping malls in South Africa with 150,000m2 of general letting area, almost 400 shop fronts, and 24 million people a year passing through its doors. The centre faces the same energy costing challenges as any large facility in South Africa where Eskom’s NMD tariff rules are in force. If the centre exceeds notified maximum demand, the facility is charged a premium on power usage.
Ken Davidson of the property investments division of OMP, says, “Maintaining a cost effective green facility is non-negotiable criteria for OMP as a founding member of the Green Building Council of SA. With the implementation of this energy monitoring and management solution, one of our most important long term goals – a key driver of the R6 million integrated intelligent building automation strategy launched at the Gateway centre in 2009 is being realised.”
The power management solution has been made possible through better exploitation of the automation capabilities and embedded energy management solution within the Johnson Controls Metasys Building Management System (BMS) installed at the centre.
Ian Hargreaves of Johnson Controls describes the challenge faced at Gateway: “Eskom defines highest averaged demand as the highest measured kVA or kW during any 30-minute integrating period within a designated billing period. If this average is higher than the notified maximum demand, the facility is charged a premium on usage. To adequately manage its consumption and utility bill, the facility thus needs to measure power usage in real time and act quickly to keep usage in peak periods below the maximum.
“We have been able to do this by integrating a panel track energy metering system to the shopping centre’s now upgraded and IP enabled Metasys building management system,” says Hargreaves.
The panel track system meters eight defined rings or streams of energy consumption at the facility. That information is fed into the Metasys BMS which has been configured to trigger load shedding activities when defined maximum use thresholds are reached. Load shedding is done by shutting down power hungry non-essential equipment like the two carrier screw chillers, two carrier centrifugal chillers and three Trane centrifugal chillers with pumps and cooling towers at the shopping centre.