When one of the largest mushroom producers in Ireland, Codd Mushrooms, looked at how to save energy within its factory chilled water system, and at the same time boost reliability, it turned to Mitsubishi Electric and its systems integrator partner MPAC for a solution. The resulting PLC based control system using Mitsubishi Electric variable speed drives to control the various pumps and systems, has now delivered a saving of over 5400kWh in one week.
The system therefore has the potential to deliver up to €40,000 per year in savings depending on seasonal variations.
Based in Tullow, Co. Carlow in Ireland, and owned and run by the Codd family, Codd Mushrooms is Ireland’s most progressive mushroom farmer, with a firm focus on quality and sustainability. The company was started in 1989 and has developed into one of the largest seller of mushrooms to the marketplace.
As the company has grown and built new production facilities, it has maintained a clear focus on the benefits of automation, as director Raymond Codd explains: “Through progressive automation, we have been able to advance our production as the business has grown.”
Energy savings potential
Codd Mushrooms was keen to investigate whether energy savings could be made in the factory chilled water system, and whether reliability could be increased. The chilled water system addresses the different requirements of the various production areas. These production areas all work independently, and need varying amounts of heating or cooling depending on the environmental conditions and the point in the production cycle.
To investigate the possibilities for energy savings in the system, Codd Mushrooms called in local Mitsubishi Electric system integrator MPAC. Director Matt Pender says: “The system didn’t have any way of knowing what the demand would be and so, it was constantly working at full capacity. Meaning it was only ever working efficiently when demand was equal to 100% of capacity, when in reality, demand at the plant is dynamic.”
Thorough investigation
MPAC performed a thorough investigation of the chilled water system, looking at its inefficiencies and areas for possible improvement. The solution developed by MPAC lay with a calculated demand system. The various pumps in the system – including the primary, the secondary pump and the twinset pump feeding the upper side of the factory – were all put under the control of Mitsubishi Electric FR-F740 variable speed drives. These were linked to a Mitsubishi Electric MELSEC Q series PLC via CC-Link.
“We have worked closely with Mitsubishi Electric for many years, and have absolute confidence in the performance and reliability of their products,” says Pender.
All process variables of pressure and temperature are measured by sensors, and all analogue and digital data is fed to the Q series PLC via Mitsubishi Electric STLite remote I/O unit. The PLC calculates the actual demand and calculates the appropriate response to meet the demand, sending control signals to the variable speed drives. By offering precise and appropriate control of the pumps, the volume of water moving through the primary and secondary circuits is always proportional to demand. Operator interaction and plant process visualisation is accomplished through a Mitsubishi Electric GOT series HMI.
Centrifugal pumps operate on a cube law with regard to energy consumption, even small reductions in speed can quickly deliver significant energy savings. “We identified increases and decreases in demand at varying points of the day,” says Pender. “The advantage of our control solution is that it constantly measures the load and responds accordingly, keeping the system at its maximum possible operating point.”
Monitoring the energy consumption
Following the installation of the new control system, MPAC monitored demand over a second seven day period, and saw energy consumption reduced from 6115kWh using the original system running constantly at full speed, to just 664kWh using the new control method – a saving of 5451kWh.
Furthermore, a switch to variable speed drive control from direct-on-line starting has reduced electrical and mechanical stresses on the pump motors, and eliminated water hammer effects by removing the ‘shock’ of starting and stopping the pumps, and eased the operational stresses on the pumps. “Before the upgrade, we had begun to see some failures in various seals and bearings. But the upgrade should have a big impact on maintenance requirements and repair costs, while extending the life of the motor and the driven equipment,” says Pender.
Raymond Codd sums up the benefits of the new control system, saying: “We were delighted to work with MPAC, who have helped us to automate our processes using a range of industry leading solutions from Mitsubishi Electric. These have increased our productivity and overall efficiency.”
“We look forward to working with them and using the innovative solutions of Mitsubishi Electric on future projects to ensure our control systems exceed the demands of future market requirements.”
Mitsubishi Electric Europe B.V. – Irish Branch
Westgate Business Park, Ballymount Road, Dublin 2.4
Tel.: +353 1 419 8800
Fax: +353 14198890
