Energy Distribution per Utility

Normally an energy project includes other utilities, too. Typically the following energy categories will be regarded:

• steam at different pressure levels;

• electricity (sometimes considering different voltages);

• chilled water or brine;

• special energies like ammonia, compressed nitrogen and others.

For energy saving and CO2 reduction projects the consultant needs a comprehensive and, if possible, consistent data set of the real energy consumption in the plants, process steps and equipment. In order to obtain this information he can collect measured and calculated data. Normally every plant, for accounting reasons, has at least one energy metering point at the entrance of the plant for every utility. Therefore the total consumption of the plant is known (assuming that the measurements are correct!).

In order to compare the different energy categories it is necessary to express the consumption in a common dimension. That can be MWh of primary energy or tons of CO2 emitted or costs (€ or $). The conversion factors between the different dimensions depend on local energy prices, the local primary energy mix and the efficiency of the energy generation. For one of our customers we converted the units for example according to Table 4.1.

Distribution of the total energy consumption for the different categories can then be presented as a chart. In this case the energy consumption is expressed as percentage of the emitted CO2 (Figure 4.4) and the total energy costs (Figure 4.5). Alternatively, a calculation based on primary energy consumption is of course possible.

It is helpful to look at the reliability of the measured data, because measurement devices can fail. In many cases redundant measurements occur, for example by a main metering point at the entrance of the plant and additional meters for single process steps. In this case the reliability of the measurement can be evaluated. When there is no redundancy in metering points, then the calculation of the main consumers can give a hint on the plausibility of the measurements (see Section 4.3.3).

In the example presented in Figures 4.4 and 4.5 the intention of the depiction of the energy distribution can be easily seen. The consumption of cooling water and air in terms of costs or CO2 emission is negligible. Here it is obvious that in the following project steps water and air will not be analyzed in detail. An exception would be if the consumption of water or air is caused by only one big consumer. Then we would consider this equipment. In all other cases the consultant

Table 4.1 Conversion of different energy units.





Prim. energy/unit

Steam 6 bara


15 €/t


0.765 MWh/t

Steam 31 bara




0.778 MWh/t





1 MWh/MWh

Cooling Tower Water




0.348 MWh/1000m3

Compressed Air 6 bara




0.095 MWh/1000Nm3

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