Energy efficiency - the priority in HVAC design

3 min read

The HVAC sector now represents around 25% of the total market for variable speed AC drives - and is growing. This growth will be further fuelled by legislation and a demand for more energy efficient systems, writes Dean Palmer

The HVAC sector now represents around 25% of the total market for variable speed AC drives - and is growing. This growth will be further fuelled by legislation and a demand for more energy efficient systems, writes Dean Palmer New European legislation on energy efficiency is on the horizon, which states that buildings should become more airtight. This will place higher demands on the ventilation systems in these buildings and the way in which they are controlled. Variable speed drives (VSDs) will therefore play an increasingly important role in these HVAC systems, since they are now seen as the most effective method of fulfilling these requirements. In addition, another European standard governing the generation of harmonics by electronic equipment such as drives, is on the way and will become mandatory in the building sector by 2008. IEC/EN 61000-3-12 covers equipment up to 75A. Any drives sourced that carry the approved standard will give the buildings manager complete confidence that the harmonics will not cause a problem. So uptake of AC variable speed drives into the HVAC sector should be fuelled even further. In the UK, the three main drives suppliers to the HVAC sector are Danfoss, ABB and Vacon, although there are other suppliers too. Although exact figures are difficult to get hold of, Danfoss appears to hold the greatest share of the market, with ABB and Vacon next in line. Tony Pickering, sales & marketing director at Danfoss, told Eureka: "The need for efficiency and flexibility has been a major driver in the uptake of variable speed drives to the HVAC sector. Sizing air handling fans and chiller pumps has always been problematical and the application of variable speed drives allows enormous flexibility, as long as the motor selected is big enough. "It's long been a jest that Europe doesn't have the climate, it has weather, and in terms of the unpredictability of the humidity and temperature throughout the year, this is true. High temperatures and high humidity occur infrequently, but systems must be sized to cater for these extremes, yet still deliver efficiency under more normal climatic conditions, season to season, day to day," he added. Total cost of ownership is also lower, said Pickering, with reduced wear and maintenance associated with variable speed drives, compared to more traditional methods of control such as throttles and dampers. "Modern drives also offer the facility for remote interrogation and troubleshooting over the Internet," he reminded us. He cited examples of Danfoss' recent customer wins in the HVAC sector: "Wembley Stadium, Portcullis House, the Scottish Parliament, Derby Hospital, the Swiss Re 'Gherkin' refurbishment, GCHQ and the Esso Glen facility." One recent customer success story involves a company called Dairy Crest, a milk processing site in Gloucestershire. After installing a Danfoss VSD on an 11kW boiler forced draft fan, Dairy Crest achieved energy savings of more than 47,000 kWh per year - worth £1,800. The site also reduced carbon emissions by 5.52 tonnes per year and achieved a payback on its investment (an installed cost of £1,400) in just nine months. By fitting a new electronic fuel control system and a variable speed controller to the forced draught fan motor, more efficient control of the fuel/air ratio was achieved. Vacon has also secured a major HVAC 'win'. Hundreds of the firm's NX range of AC drives will control the pumps and fans for the HVAC plant that forms the core of the environmental management system for Heathrow Terminal 5 airport complex, scheduled to open in 2008. According to Barrie Keen, UK sales director at Vacon, the contract represents "one of the most significant orders we have ever received". Vacon worked closely with system supplier Trend Controls so that its drives could be incorporated easily with the associated building management system. Due to energy efficiency savings, Vacon said payback is expected to be less than one year for its drives. ABB has also secured wins in the UK HVAC market. Edinburgh Hospital is using a range of AC VSDs from ABB to maintain a clean air supply in its 20 operating theatres. Each theatre will use three to four ABB drives. The theatres need a filtered airflow with a maintained air volume. As static pressure builds up over the air filters, the drives will compensate for the reduction in flow rate so as to maintain the air volume. The building management system monitors for any loss in performance. The theatres are not in constant use, therefore the drives are often employed in a standby mode, maintaining a reduced airflow in order to save energy. And a London landmark, the 55 Bishopsgate building, is using 17 ABB drives, between 11kW and 22kW, to control air flow to the office's HVAC system. The units replaced variable pitch fans that were causing numerous breakdowns. Stiff components within the fan impeller units were causing the positioning actuator to come under sever strain, damaging drive gearing and burning out control boards within the actuator. Although the HVAC sector looks certain to continue its uptake of VSDs for energy efficiency, Tony Pickering of Danfoss predicted another niche growth sector: "Refrigeration is the next high growth drives sector. Equipment such as condensing fans for large chillers in supermarkets is one application example. We're currently talking to a major supermarket chain in the UK about how we can help it save energy on its chillers."