We need to establish the important physical components or processes of both energy and production systems that play a key role in the supply and demand side of manufacturing operations. Usually, process flow charts and single line diagrams are used to establish this.
Single line diagrams present a picture of the entire plant energy system and show nominal capacities, generation, distribution and consumption of energy in forms specific to the present state of the plant. A simplified single line diagram may also be called energy flow chart.
Process flow charts consolidate data from present operations to facilitate production control, record current operating conditions and direct an analysis along a logical path, starting from raw material input, following through the production stages up to the final product packaging. They also show the sequence of tasks with related inputs, outputs, activities and opportunities for the assignment of responsibilities. Such diagrams are simplified and structured visual representations of processes that form the production chain and show the workflow of a company.
To give an overview of the various energy and mass streams, the process flow chart of a sample plant (tuna cannery) and its associated operations is presented in Fig. 2.3. When energy and process flow charts are put together, valuable information is provided on where, why and what type of energy is used. This chart can be the basis for decisions on setting up energy cost centers. Energy cost centers (ECC) are business segments (i.e. departments, areas, units of equipment or single equipment) where activities or production volume are quantifiable and where a significant amount of energy is used.
The same chart (Fig. 2.3) can be used to identify the sources of environmental impacts from the manufacturing operations in the areas or activities where various resources are used.
For instance, the example in Figure 2.3 indicates the ECCs in which waste water and solid waste are generated and air emissions occur. The dotted line represents the factory boundary, so where the arrows on the diagram cross the boundary, these are the instances of direct impact on the external environment.
There are no fixed rules on how to set up ECCs. An ECC can be any department, section or machine that uses a significant amount of energy or creates significant environmental impacts. As the word 'significant'
indicates, the process is quite arbitrary. However, there are several criteria that should be observed when designating ECCs:
• A process or activity that requires energy should have a measurable (preferably single) output or outcome.
• The energy consumption and/or environmental impacts of the process can be measured directly.
• The cost of measurement should be no more than 10-20 % of annual energy or environmental compliance costs related to that ECC.
• Responsibility for energy and environmental performance in the area can be assigned to the person working in or responsible for that area.
• The standardized performance indicator can be expressed.
• Realistic targets for performance improvement can be established.
The guiding principle for ECC set up is to follow the production process stages as given by the process flow chart, and try to set up the ECCs so that they coincide with existing production quantity control boundaries. On the utility side, ECC set up is quite straightforward - each utility system can be regarded as one ECC. For instance, one ECC can be a boiler house, another one a compressed air room and yet another refrigeration plant. Figure 2.4 shows the actual ECC as defined for our sample plant. Obviously, not each production phase constitutes an energy cost center, as can be seen by comparing Figure 2.3 and Figure 2.4.
Energy Electrical 22 kV
Transformer 1250 kVA
I Air Pollution f
ECC 4 Washing
ECC 5 Steaming and Cooling
ECC e Canning
ECC e Canning
ECC l Retorting
ECC 8 Packing
ECC 9 Waste Water Treatment o Measurement
Raw Material: FROZEN TUNA FISH
Figure 2.4 Energy Cost Centers in a Tuna-Canning Factory
Whether to include offices, warehouses and similar areas is a matter for discussion. Although they may not be significant energy users or a source of significant environmental impacts, for the sake of consistency, they should be designated as ECCs, and people working there should be responsible for the energy and environmental issues in those areas, because, as previously established, energy and environmental performance concerns everyone in the company.
As the Figure 2.5 shows, the concept of an ECC is a unifying framework that brings together all the components of EEMS:
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