Electric cool SCADA

When it comes to keeping electrical costs down on truly massive rerigeration plant, a smart SCADA system is the ultimate key BY BRIAN TINHAM

Keeping tabs on energy costs plant-wide – all from your desktop PC, its SCADA and a little clever code

A rather smart PC SCADA system, based on Intellution’s The Fix, and developed by Boward Computer Services, is helping Birds Eye Wall’s to minimise its huge electrical energy costs in Gloucester – site of Europe’s largest ice cream factory.

The site is said to produce about 60% of the whole of Europe’s ice cream – so we’re talking pretty serious refrigeration plant! It buys electricity from the MEB, and unit prices vary significantly at half hour intervals. Paul Boon, site services engineering manager, says that electricity costs about £1 million per annum.

He said that one way to reduce costs was to optimise control algorithms for the compressors. But to achieve this meant getting historical trend and real time data. David Baker, site process engineer said that they needed to be able to analyse plant conditions and reactions. And, hence the SCADA.

In fact, refrigeration is managed by a network of well over 100 Square D PLCs – apparently, second only in size to that at Ford’s Dagenham plant. Real time power demand data is available at the remote PLCs, so the SCADA system reads this from about 10 of them over the site’s Ethernet network.

The Fix has been configured to match these against half hourly unit costs in an associated spreadsheet, and thus to calculate real time costs against current refrigeration plant running powers. Quite sophisticated trend graphs show the peaks, and operators get live energy cost data on screen, plus historical plant data from which to make decisions about plant running. There’s also plant mimics, plant status and alarm coverage, etc.

The SCADA system has six client nodes – two compressor room terminals, two view-only desktop clients and two development nodes. One of the latter has a modem link to Boward, together with a CD cutter for recording plant performance. It allows all involved easy access to historical data. There’s also a desktop client node on the production floor.

According to Steve Grant, principal engineer at Boward, a similar Fix-based system has recently been installed and commisioned at Birds Eye Walls’ Grimsby fish fingers and ready meals plant. Further, using Unilever’s own broadband TCP/IP network, the Grimsby Fix system can talk directly to that at Gloucester.

Grant: `They’ve been seamlessly integrated, allowing the nodes to communicate apparently directly over the WAN, again to provide real time price analysis graphics. In fact, we’ve now proven the comms across all of Unilever’s network. For example, management at the company’s Walton on Thames HQ could see the Fix energy costs also in real time.’

What’s particularly interesting is that both systems have been engineered entirely within The Fix SCADA system standard facilities. Grant: `The Fix database can do a lot more than most people realise. There’s a lot of maths and control functionality. For example, we’ve used it here to perform rolling averages on the data and for totalising the running costs.

`And bearing in mind that The Fix itself is not power tolerant, we simply write the accumulators to areas of PLC storage in the event of PC failure. No specific PLC code was written for this; yet when the SCADA system reboots no data has been lost – and the PC totalising just continues.’

It’s certainly a neat way of getting power-tolerant statistics out of your SCADA.