Sharp landing for energy costs at Belfast International Airport

Belfast
Fitting Danfoss variable-speed drives to fans in air-handling units at Belfast International Airport is expected to save over £60 000 a year — with a payback of less than eight months.
Annual energy savings of over 1000 MWh are expected at Belfast International Airport following the refurbishment of a number of air-handling units. The work includes the retrofitting of variable speed drives to the fans of these AHUs. Carbon emissions will be reduced by over 500 t a year. Following the success of retrofitting variable-speed drives to two 30 kW circulating pumps, the airport’s technical supervisor, Colin Sloan, decided to fit variable-speed drives to 28 fans in AHUs covering about 40% of the main airport. He explains, ‘From past experience, we knew that VSDs could offer substantial energy savings. 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.’ These fans represent 240 kW of installed load, representing a significant proportion of the airport’s energy bill. The fans previously had direct-online starters and no speed control. Preliminary measurements showed that the motors were oversized and running inefficiently well below full capacity. The building-management department of Belfast company VIS-Security Solutions carried out a detailed site survey of existing loads and presented a report showing that with only a 20% reduction of fan speed the energy savings would pay for the VSDs in less than a year. The report highlighted that the drives could be controlled through ModBus and BACnet communications with carbon-dioxide sensors in each of the passenger-processing areas. 28 Danfoss VLT6000 HVAC drives were installed and commissioned. Drive outputs were initially limited to 30 to 37 Hz pending full commissioning of the air-quality monitors. The air-conditioning system functioned satisfactorily during the summer with fans at 80% of full speed, with a £15 000 reduction in the energy bill for this 3-month period. In cooler seasons, the savings are expected to be even greater. Colin Sloan says, ‘The first quarter savings indicated we’ll get a return on our investment in less than eight months, and comfort conditions for our customers will certainly be improved. ‘These savings are so spectacular we’re currently looking at the remainder of our AHUs and, indeed, every variable-load device right across the airport with a view to fitting variable-speed drives to them and making even greater savings.’
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