Cherry Valley ducks energy costs

Lincolnshire, UK - Cherry Valley Farms, the UK’s largest duck producer has reduced its energy costs by £25,000 a year after installing ABB standard drives in some of its refrigeration plant. This represents a saving of 49.6% of the energy previously consumed by these applications.

Lincolnshire-based Cherry Valley Farms processes 45,000 ducks per day, each weighing from 2 to 4kg. Each duck is chilled so the chilling plant is a major part of the factory’s operation and accounts for a high proportion of its operating costs.

Cherry Valley wanted to explore ways of reducing its energy costs. Darren Bolton, operational improvement manager at Cherry Valley, said: “I read in a magazine about an ABB case study where low voltage AC drives had been used by Northern Foods to save energy. We contacted the UK government backed Faraday Partnership to seek advice on variable speed drives, as well as ABB and its channel partner Inverter Drive Systems (IDS) of Nottingham.”

In the food and beverage sector, refrigeration plant is often the single greatest consumer of electrical power. Such plant is often sold in a very price sensitive market, so its manufacturers use direct-on-line control as standard to keep costs down. This means that there is no potential to vary the speed of motors to save costs.

Most users of refrigeration plant are wary of carrying out modifications for fear of interrupting the process and do not generally have the confidence to make the conversion to variable speed drives without specialist knowledge and support.

IDS took on responsibility for finding and implementing energy savings on a ‘no savings, no fee’ basis. The project carried out by IDS initially involved a seven day energy analysis of the existing direct-on-line controlled condenser fans to establish operating costs at fixed speed. The four fans had a combined measured power of 38kW.

Blaise Ford of IDS says: “The condenser fans are important due to the nature of the operation. In the first stage of the refrigeration cycle, the refrigerant high pressure liquid expands and absorbs heat from the ducks being cooled, tuning into a warmer gas. This gas is then compressed. The compressor transforms the vapour from a low-pressure gas into a high-pressure gas.

“The refrigerant gas enters the condenser, where fans are used to help cool it down to atmospheric temperature and turn it back into a liquid, ready to expand and cool once again.

“We used the head pressure signal to control our drive to keep this pressure perfectly at its design point, varying the fan’s speed to meet the chilling demand.

“Previously, at Cherry Valley, this was only an on-off cycle – the ABB drives also reduce the inherent energy wasteful ‘cycling’ of the original control.”

ABB standard drives were then installed, controlled by the existing sensors for compressor fixed head pressure. On completion of the project, a further seven day energy analysis was carried out and the savings and payback periods calculated. It was shown that the drives had saved 13kW in total representing an annual saving of £7,400.

As well as the energy saving on the condenser fans, the reduced on-off cycling of the refrigeration plant lead to a further 10% reduction in compressor power reduction. It also significantly reduced fan noise, improving the environment for neighbouring properties.

Drives were installed on several other types of plant, including air compressors and water pumps, and the facility is now making energy savings of £25,000 a year after installing £16,000 worth of ABB standard drives. The original forecast estimated that payback would be in 12.6 months; yet actual payback time was only 7.7 months.

“There are many areas where drives could be used but IDS [only picked] up on those that could really make a saving. Those compressors that were working fine were left alone at IDS’ recommendation," said Bolton.  “Their theoretical results were all backed up with good graphs and charts. Quite simply IDS are very, very good - we doubted the energy savings and needed IDS to prove each drive in turn.".