PRODUCTION | ENERGY MANAGEMENT
Key steps in assessing the energy efficiency of a compounding plant: mately 30% of the total load.
n Plot electricity use against produc- tion volume - processed amount of plastic – over a month as a scatter chart. Use the spreadsheet to find the equation of the linear line of best-fit and the correlation coeffi- cient (R2
) – see chart below.
n The intersection of the line of best-fit with the electricity usage axis is the ‘base load’. This is the energy use when no effective production is taking place but machinery and services are available. This should be approxi-
n The slope of the linear line of best-fit is the ‘process load’ for the site and shows the average energy being used to process each kilogram of polymer. The process load varies and is operation specific. For compounding, the value of the process load would be expected to be in the region of 0.4–0.6 kWh/kg.
n A good correlation coefficient (R2 )
value is less than 0.7, which indicates good consistency of ener-
gy use. This is not the same as good energy management, but indicates that the site is consistent and makes improvement easier to manage.
n A poor correlation coefficient (R2 ) is
greater than 0.7, which indicates poor consistency of energy use. This is generally the same as poor energy management and indicates that the site is inconsistent and makes improvement difficult to manage.
Source: Tangram Technologies
PCL gives an insight into how energy is used at a site but there will be no progress in managing energy use unless it is on the management agenda. If energy use is not visible and measured, then there will be no improvement. Every site needs an ‘Energy Policy’ - a statement of commitment on energy use. This should include short, medium and long-term improvement targets. The policy should be widely distributed to encourage awareness of the costs and benefits of energy management,” Kent says.
The Performance Characteristic Line is the starting point for any attempt to improve plant efficiency. Easy calculated, it provides an ‘energy fingerprint’ of a facility and reveals key insight into how it operates. Here, for example, it can be seen that the poorly managed site has a high process load, a high base load and an acceptable correlation coefficient while the well managed site has a low process load, a lower base load and a very good correlation coefficient. The poor site will accumulate energy costs approximately twice that of the good site for the same production volume.
Key points to consider in implementing an Energy Policy:
n Create and distribute a formal site Energy Policy. n Assign clear responsibilities for energy management. n Gather initial data and convert this into information to manage site energy use.
n Use the performance information to target improvements. n Publish performance information widely.
Source: Tangram Technologies 16 COMPOUNDING WORLD | February 2020 Source: Tangram Technology
Driven by production “Energy management should be the clear responsi- bility of the production department because it controls most of the energy use. An ‘Energy Manager’ can only act as the scorekeeper and the process should be driven by production. Funds and time should be allocated to carry out energy management projects. In addition, monitoring and targeting (M&T) are fundamental for energy management. A lot of data is probably already being collected but energy management is not about data, it is about providing information to target improvements. Targeting is the key action - what gets measured, gets done,” he adds. According to Kent, the ideal outcome of a good
energy management programme would be a 30% reduction in energy use and costs. “One-third of this would come from management decisions by simply recognising that there is a problem and taking normal management actions. A further third would come from simple maintenance work costing less than £2,000 [US$2,600], while the final third would come from longer term work requiring investment.” Kent says it is important not to forget that energy is a variable and controllable cost and over 30% of
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