VSD payback of one year or better
August 1st 2006

Dairy Crest is helping to offset the problem of high energy costs with the installation of four turnkey energy saving systems at its Maelor site near Wrexham.Designed, manufactured and installed by WYKO Electronic Services, the systems are fitted to cooling towers and an effluent pump at the Maelor site. Although costing in excess of 14 000 in total, the systems are well on track to achieve their original calculated payback of just one year. In fact especially so, as the original payback figure was calculated on an hourly kW of 0.025; today this figure has risen sharply to 0.046 per kW hour,providing the potential for a much faster payback.

Dairy Crest's site at Maelor is split in to two independent factories. Maelor Pre-Pack is a cheese packing facility and Maelor SDI (Specialist Dairy Ingredients) is a Whey processing plant. SDI takes in tankers of Whey and Whey concentrate from cheese manufacturing sites and produces lactose powder and DeLactose Whey Concentrate.

Central to the production processes at the SDI site are three cooling towers with fans driven by 18.5kW motors, and an effluent pump driven by an 11kW motor. What all these drive motors had in common until recently was that they were all running at high speed most of the time, including weekends.Chris Dale, who is engineering manager at the SDI site, was aware that this type of running was inefficient and was keen to do something about it.

Engineers from the company visited the site and assessed the motors, noting the hours that they were run, their rated speed and current and duty cycle. In addition, the WYKO team were asked to include temperature sensing of the ponds at the base of the cooling towers.This meant that, with the installation of inverter drive systems, there was a facility for interactive control between the temperature of the pond and the speed of the cooling fans; hence, the fans would not be running at full speed for most of the time.

The result of the motor survey was a series of energy saving calculations.These were based upon the use of four, turnkey control systems employing Omron- Yaskawa E7 inverters.Designed for energy saving applications, the inverters have an advanced Level-2 tuning feature that de fluxes motors for enhanced energy efficiency.

WYKO's quote and payback calculations were submitted in a competitive tendering process to Dairy Crest management. Subsequently,Wyko was awarded the project, not only on the basis on of their payback figures, but also because the company assumed full project responsibility for installation and commissioning.

"The VSD installations have delivered the predicted benefits in line with the project plan," said Chris Dale."The specific energy savings are difficult to verify as the performance depends on variables such as ambient temperature for the cooling towers, and tank level for the effluent pump.However, when the cooling towers were switched to the VSD supply there was a step change in electricity usage that indicates energy savings in line with WYKO's calculations."

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