2009-05-08 - A school in Helsinki, Finland installed ABB drives to cut energy use in its gymnasium by about 15 percent, a reduction made possible by using the drives to govern energy use according to need.
By
ABB Communications
Konala Comprehensive School’s gym was providing heat, ventilation and air conditioning (HVAC) for 400 people - the room’s maximum capacity - even though on most days the facility was used by fewer than 30 people.
To accomplish this high ventilation output, the HVAC system ran more than 4,500 hours per year at full speed, while ventilation in the changing room operated continuously, whether there was excess moisture, or not.
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- An energy audit of the school conducted by ABB drives distributor Airwecare Oy, found that gym fans alone accounted for a fifth of the building’s electricity consumption, amounting to 34,200 kilowatt hours (kWh);
- Fan efficiency was only 20 percent;
- 117 megawatt hours (MWh) of heat energy was being lost to the outside air every year, equal to a quarter of all heat energy used by the school
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ABB standard drives reduced the school's electricity consumption by more than 14 percent in the first 10 months of operation in 2007, for a power savings of 17,539 kWh. Meanwhile, heat energy consumption dropped by 16 percent (57,389 kWh).
Savings greater than expected
“We originally estimated that the total annual savings compared to the old system would be in excess of $4,450, with a reduction of 26.5 tonnes in carbon dioxide emissions,” explains Petri Peltonen, managing director of Airwecare Oy, system installer and an ABB drives distributor. “However, the actual results show that the savings are greater at about $5,730.This was an important contract for the customer, Helsinki City, which operates a large number of schools in which money saved on energy use can be used to benefit the education of children.”
(The savings are based on $0.10/kWh for electrical energy and $35.7/MWh for thermal energy. The emissions reduction assumes production of 500 kg of carbon dioxide per MWh of electricity, and 286 kg per MWh of heat).
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ABB standard drives for HVAC installed to control new high efficiency Eff1 ABB motors.
As it happened
ABB standard drives for HVAC were installed to control new high efficiency Eff1 ABB motors, which drive the supply and return fans. The supply fan now operates in response to the carbon dioxide reading in the gym and moisture levels in the shower areas.
The return fan echoes the speed of the supply fan, causing a small negative pressure in the building for improved air flow. Running hours are set using the real time clock feature of the ABB standard drive for HVAC.
The air duct of the return fan was repaired to address troublesome air turbulence, which was reducing airflow, and this improved the performance of other return fans. In addition, the fans will now be driven directly by the motor, sharply reducing noise compared to traditional belt-driven fans.
More schools
Timo Posa, energy saving specialist at Helsinki Public Works Department, said there are about 150 city schools in a similar situation. He praised Airwecare’s energy audit for pointing the way to significant future savings.
“The project was executed within the agreed time without causing any disturbance to the school’s normal activities and the energy saving potential is high. If we carry out a similar program at the 50 highest energy-consuming schools, the energy saving potential could be about $300,000 per year, and the carbon dioxide emission reduction would be some 1.3 million kg," he added.
The required investment to accomplish this would be about $1.3 million, and would pay for itself within five years.