Case story

Belfast International Airport drops its carbon emissions by 500 tonnes per year

— MONDAY, 23 NOVEMBER 2015 BY DANFOSS DRIVES

Following the previous success of retrofitting VSDs to two 30 kW circulating pump drives, Airport Technical Supervisor Colin Sloan decided to fit variable speed drive control to the 28 fans on the AHUs covering 35 – 40 % of the main airport.

“From past experience we knew that VSDs could offer substantial energy savings and with rapidly rising electricity prices, and prompted by the availability of a 30% grant from our energy supplier, Energia, under their Energy Efficiency Scheme, we decided to refurbish a number of our air handling units with variable speed drive control.”

Belfast International Airport handles over 5,000,000 passengers per year and the air conditioning system is in operation continuously to guarantee passenger comfort. Some 28 fans, totalling 240 kW of installed load, represent a significant proportion of the airport’s annual energy bill.

Previously the fans were running uncontrolled at full speed with direct on-line start and preliminary measurements had indicated that the motors were oversized and running inefficiently and well below full capacity. Fitting variable speed control would not only offer energy savings but would improve passenger comfort throughout the airport.

The building management department of Belfast company VIS Security Solutions carried out a detailed site survey of existing loads and presented a report with showed that with only a 20% turndown on fan speed, the system would return energy saving sufficient to pay for itself in less than 1 year. It highlighted that conditions within the airport, varying widely with daily and seasonal temperature conditions and passenger numbers, could be stabilised by linking the drives through ModBus & BACnet communications with CO2 monitors, which measure the energy savings in each of the passenger processing areas.

Subsequently, 28 Danfoss VLT® 6000 HVAC drives, supplied by local Danfoss partner Greenville Electrical, were installed and commissioned, initially with the drive outputs limited to 30 – 37Hz, pending full commissioning of the air quality monitors. Despite the hot summer conditions, during which the air-con system functioned satisfactorily with the fans at 80% speed, the actual savings exceeded expectations and the energy bill was down by over €16,800 for the three month period. In cooler weather conditions, it is anticipated that savings will be even greater, especially with the AHUs under full automatic environmental control.

According to Colin Sloan “the return on energy saving is so good that the investment has paid for itself in less than one year. Comfort conditions for our customers have definitely improved,” says Colin Sloan. “And it was vital that there should be minimal disruption to the airport during the refurbishment, so VIS Security Solutions took every opportunity to simplify the installation process. The use of fieldbus communication reduced the complexity and cost of the control wiring. Moreover, the new control panels were pre-built and installed with the existing control panels used temporarily as a junction box.”

All of the work was carried out during normal working hours but nonetheless, downtime was absolutely minimal during the change-over and neither the staff nor the passengers noticed any disruption.

Thanks to this success, the airport management is currently looking at the remainder of the air-handling units and every variable load device across the airport, with a view to fitting variable speed drives to them and making even greater savings. Better air quality is being delivered to the passengers and at the same time the airport saves 1 million kWh and a lot of money every year through the installation of variable speed drives. “Due to rising electricity prices, the savings are now €112,000 per annum. It’s much more than the €67,000 we had estimated,” Colin Sloan. technical supervisor at Belfast International Airport, says. The insatllation of VLT® drives have turned the airport into a greener facility, resulting in considerable energy savings and reductions in carbon emissions.