When storing high quality chocolate products,maintaining the right temperature is critical, particularly when holding up to £50 million of stock in possibly the largest chilled warehouse in Europe.
This is a daily issue for Cadbury Schweppes, one of the world’s foremost chocolate manufacturers and when the chillers at its huge storage facility in Minworth were nearing the end of their working life, the company decided to review the entire building management system (BMS) for the 530,000m3 site. Satchwell, a leading British building control systems manufacturer, was invited to help develop a solution that would result, not only in a more efficient performance, but also bring down energy and maintenance costs.
Environmental considerations have always been important to Cadbury Schweppes. The company was in the vanguard of zero CFC emission technology at Minworth when it was built,and was keen that any new installation would exceed the latest emission targets regarding greenhouse gases.
Working with Satchwell,Cadbury Schweppes realised that to have the greatest impact on emissions they would need to take an holistic approach to the efficiency of the entire building management system, rather than simply replacing the chillers.
Tony Spencer,Group Energy Manager for Cadbury Trebor Bassett,commented:“For an organisation like Cadbury Schweppes there are a number of factors that need to be considered when looking at a project like this; both financial and environmental. We are proud of our green credentials but also needed a solution that would deliver savings against ever increasing energy costs.”
An added challenge for Satchwell was that Minworth was a live site and all work had to be conducted while keeping millions of pounds of quality sensitive stock at the right temperature. Starting with the chillers, but looking at every aspect of the air conditioning technology at Minworth, Satchwell worked alongside the Cadbury project team to help develop a plan that would not only improve the operation of the plant,but also instigate a more intelligent use of the equipment.
One of the first issues the project team wanted to address was how to make asset maintenance more efficient. Satchwell helped design a real-time condition based monitoring system that could predict problems and make best use of maintenance resources.
The system would measure the vibration, humidity and pressure within machinery such as the chillers and filters through a series of sensors and feed this back into the building management system (BMS). This data was then analysed and reports were produced that were available through the company’s web browser.
Alister Jones, Global Supply Chain Development Manager at Cadbury Schweppes commented: “The benefits of the condition based monitoring system mean that routine maintenance is based more on science and fact than gut feel,and the reduction in costs is dramatic. We are now able to accurately predict when problems will happen and, by accessing the information on the web browser, I can monitor asset performance from anywhere in the world.”
Sensors were also fitted to the filters and fans controlling air coming into the pressurised warehouse. The project team found by analysing the sensors’ data, that varying the speed of the fan, dependent on time of day and year, significantly reduced energy consumption but did not compromise air quality or temperature.
To circulate air around the huge site, the Minworth warehouse has nine 75kw circulation fans and nine 5KW fresh air fans which were previously on constantly, using a significant amount of energy and generating excess heat. A challenge for the team was to find a way to improve the performance of the fans without putting the millions of pounds of stock held at the facility at risk.
Unable to conduct real trials, the team used complex computer modelling to simulate fan performance and the environment within the facility. Using this technology gave the team added confidence that the engineering principles were sound before any changes were actually made. It was discovered that, by installing an inverter drive to vary the speed of the fans, frequency could be reduced by up to 20 percent at certain times, improving efficiency by 50 percent without affecting the overall building temperature.
To improve communication between vital parts of the plant and to accurately monitor temperature within the building, the project team completely overhauled the existing system. Satchwell retrofitted the existing control panels to better manage the HVAC system and fitted Lonworks integration controllers to allow full communication with the new chillers to monitor performance.
Satchwell also installed RAM (Remote Alarm Manager) software to enable any alarms to be sent as text messages to mobile phones. Over 100 sensors for measuring temperature, humidity and pressure were rewired and replaced, plus inverters fitted to all circulation and fresh air fans to allow them to be run at varying speeds.
With the new technology in place, the temperature levels of the stock could be more accurately measured, 24 hours a day. Plus, using Satchwell’s Smart Utility Management system (SUM), Cadbury Schweppes also had a clearer idea of its energy consumption.
SUM took the raw meter data, gathered from all Cadbury’s utility meters and sub-meters on site, and fed it back to Nexus, Satchwell’s remote management centre, for monitoring and analysis. Regular reports are produced, enabling the company to closely measure utility consumption and understand when and why usage was happening.
Previously, the chillers at Minworth were used on demand, during both day and night. Using the temperature information and cross referencing it with the SUM data, Satchwell and Cadbury saw an opportunity for a more intelligent use of the chillers that would bring down energy costs.
Through a combination of mathematical modelling, experimentation and physics, it was discovered that a large quantity of chocolate held its temperature for longer periods than the team initially expected. This meant that, rather than being used for sporadic periods during day and night,the chillers could run for a prolonged time during the off peak period. This extended use would drive stock temperature down to the lower end of the optimum target range and then the chillers could be switched off.They would not need to be turned on again for some hours, thereby making significant savings in energy use during the day.
Richard Goode Asset Care Manager for UK distribution commented: “The work the team have done means that in effect the chillers are now being controlled by the product temperature, rather than the air temperature and that’s an important step forward from a quality control point of view as well as energy reduction.”
The overall project resulted in a reduction of 40 percent in warehouse energy bills plus significant savings on routine maintenance. The project is on track to pay for itself within three years.
