ABB makes the saving

A semiconductor manufacturer in Plymouth, UK is saving over £30,000 a year in energy costs, since installing six, 37 kW ABB HVAC drives on its three cooling towers. The £15,000 installation is set to give a payback in only six months. The drives were installed by the local ABB HVAC partner, Drive Control.

X-FAB UK Ltd is one of the largest semiconductor makers in the UK. A clean, vibration-free environment is a top priority in semiconductor manufacturing and the company uses large quantities of air and water to maintain cleanliness. The three cooling towers produce chilled water for the manufacturing process.

The ABB drives are used to control six, 37 kW fan motors in the cooling towers. Originally, the fans were star/delta connected, arranged in cascade style so that they would come in, or disconnect, one by one as demand varied. This meant the final fan would constantly be switching on and off, sometimes as often as every 10 minutes. With a large 37 kW motor, this would draw significant start-up current. Additionally, whenever an odd number of fans were connected, air from the last fan would blow out through one of the other fans.

With the ABB drives, two fans start on the first towers at 20 Hz when the building management system indicates that cooling is needed. If more cooling is required, the next two fans start at 20 Hz and then the remaining two start if there is demand for still more cooling.

For further cooling, all six fans run together between 20 Hz and 50 Hz. At an installed cost of £15,000, an annual saving of £31,400 is achieved.

Maintenance costs have also been reduced, as drive belts would break at least once a month with the old system.

“We have great experience from installing drives in cooling towers so we knew the savings would be massive,” says Jez Wyant, Drive Control’s engineer on the project.

“We worked out the cost at fixed speed, measuring power consumption and power factor and then estimated the savings at variable speed. Erring on the side of caution, we predicted 18 months payback but in the event, X-FAB actually got the money back in six months.”

“I hadn’t used drives very often before Drive Control came along to give me a demonstration,” says Ted Judge, Senior Facilities Engineer at X-FAB UK Ltd.

“However, I now see that using variable speed drives is the most effective way for us to save energy. I have a 10-year plan for how to reduce energy use at this site and it will mainly be achieved with drives; 70% of electricity here at the plant is used by motors so there is vast potential for using drives.”

Further energy saving projects with drives have since been carried out, enabling Judge to reduce electricity use by about 5% across the site so far.

“The savings offered by variable speed drives are too big to be ignored. To help keep the drives running and to identify further energy saving opportunities, we work with Drive Control as a partner. Jez and his colleagues can sort out any minor problems straight away and paying him to do this is more cost-effective than to employ a maintenance engineer,” says Judge.