A recent survey of the Trend building energy management system and the plant it controls at Bridgewater Place, Leeds, should see significant energy savings at Yorkshire’s tallest building.
Conducted by Trend at site property manager, Jones Lang LaSalle’ request, the audit involved close collaboration with M&E maintenance provider, Norland Managed Services. The £3,500 cost was recouped “within weeks” via system changes made during the audit, which also identified a further £35,700 in annual savings achievable through additional investment in the BEMS, now proceeding.
Bridgewater Place is a 32-storey, mixed-use development comprising some 23,000 m2 of commercial office accommodation over three wings, connected by an eight-storey glass atrium, 200 luxury apartments, and 1400 m2 of ground-level retail space.
Each office wing is served by a main air handler with heat recuperation, with some 650 fan coil units providing local air conditioning. Three condensing boilers supply low pressure hot water, with chilled water requirements met by four water-cooled chillers. Control and monitoring of the commercial area’s HVAC services are performed by a Trend BEMS comprising seven IQ3xcite controllers on the main plant, and a dedicated IQL controller on each fan coil unit. All the IQs are network-linked, and the main system access point is a Trend 963 supervisor.
Norland Managed Services saw was considerable scope to save energy through optimisation of the controls, and, with Trend, approached Jonathan Ward, Jones Lang LaSalle’s facilities manager at Bridgewater Place, and proposed an energy audit, which he approved.
A Trend engineer spent three days reviewing the plant’s operation and control, with subsequent changes to control settings and strategy including re-setting of the building occupation times, which govern when the air conditioning is turned on and off. These times were reduced in all 25 office “zones” – typically by three hours per day. This change, and introduction of optimum start/stop control in every zone, has reduced unnecessary air handler and fan coil unit operation, while the boilers and chillers are now enabled for just 50 hours per week, instead of the previous 67 hours.
The boilers’ running hours have been further reduced by lowering the outside air temperature economy set-point from 24°C to 17°C, which, if exceeded, prevents them from operating. The supply air set-point for all three AHUs was also trimmed back, from 19ºC to 18°C, to increase “free” fresh air cooling, and thus cut the chilled water demand of the fan coil units. A simple “staging” strategy was also used – to stop there always being two chilled water pumps running, irrespective of demand.
The audit also recommended installing new hardware, and major reconfiguration of system control strategies, which Jones Lang LaSalle has agreed to. The anticipated £39,500 cost should be re-couped in just over a year – based on an estimated annual cut in gas and electricity consumption of 518,130 kWh, equivalent to a £35,700 saving.
Substantial savings will result from fitting of variable speed drives (VSDs) on the air handlers’ supply and extract fans, with speed controlled based on occupancy – the fans will thus no longer run “flat out” continuously, and on the chilled water pumps.
Boiler and chiller control will be changed to ensure operation only when there is heating or cooling demand. A lower return temperature set-point during low demand will allow the boilers to operate at high efficiency by condensing water out of the flue gases. Adjustment of AHU controls ill allow “night purging” of the building (using free cooling), potentially cutting the cooling system’s daily energy use by 20%.
Once the proposed changes have been completed, the building’s commercial area could be using over 10% less energy than before the audit.
To keep its BEMS operating effectively and maintain energy savings, Jones Lang LaSalle has invested in a Trend IQEye automatic monitoring and reporting package that continuously checks the system, and highlights possible problems.
Trend Control Systems Limited
Albery House, Springfield Road, Horsham, West Sussex, RH12 2PQ, UK.
Tel: +44 (0)1403 211888 Fax: +44 (0)1403 241608 www.trendcontrols.com
