**3.1. Allocation of electricity use − Measurement case description**

In a typical measurement case we want to separate the electricity use for the unit processes air handling, lighting, compressed air, internal transports and packing. Instantaneous power measurements, current logging and rated power for equipment are used to allocate the elec‐ tricity use.

Based on information from the staff at the industry, we know that the distribution board in Central Picking Stock is used for ventilation, lighting and electric tools for packing. The Central Garage distribution board is used for ventilation, lighting and a forklift charger. From the board Central Large Hall electricity for lighting, ventilation and packing equipment is dis‐ tributed. Based on that information, and the drawings of the electricity distribution system in Figure 7, the plan for measurements may look like in Table 3.

The logging period is the same for all the current clamp meters, in this case seven days, to cover the variations in energy use in production hours as well as during the weekend. The range setting of the current clamp meters is to be appropriate for the load, but also depends on the type of clamps and loggers available at the moment. In this case we have 500 A, 200 A and 20 A current clamp meters.

When the impact of the proposed measures is calculated, a new balance is presented (Figure 6). The new balance can have two different purposes: It can show the potential for changes in the energy use or it can show the calculated impact of the measures. The potential for energy efficiency can be estimated with standard values for the best available technology. If the impact of the suggested measures is to be presented, more detailed technical and economical calcu‐

This part is of crucial importance, not least in regard to whether the energy audit results will, in fact, be accepted, and not discarded. Normally, a meeting is held with representatives from the industry concerned and the conductors of the audit about the proposed energy efficiency measures, and the analysis of the energy balance. In this step, the primary focus is on the proposed measures. For some processes, there are a number of different alternatives. This step enables the energy auditor and the industry representatives to discuss which measure is most suitable for the industry. Normally, this meeting is not with high level executives but is held

This section shows a few practical examples of measurements and analysis for energy audit purposes, focused on electricity. The building properties and heating and cooling systems are often important to examine in an energy audit. Air flow and temperature measurements are often needed. As there are fairly standardized methods for these tasks, they will not be further

In a typical measurement case we want to separate the electricity use for the unit processes air handling, lighting, compressed air, internal transports and packing. Instantaneous power measurements, current logging and rated power for equipment are used to allocate the elec‐

Based on information from the staff at the industry, we know that the distribution board in Central Picking Stock is used for ventilation, lighting and electric tools for packing. The Central Garage distribution board is used for ventilation, lighting and a forklift charger. From the board Central Large Hall electricity for lighting, ventilation and packing equipment is dis‐ tributed. Based on that information, and the drawings of the electricity distribution system in

The logging period is the same for all the current clamp meters, in this case seven days, to cover the variations in energy use in production hours as well as during the weekend. The range setting of the current clamp meters is to be appropriate for the load, but also depends

lations are made.

132 Sustainable Energy - Recent Studies

discussed in this chapter.

tricity use.

**2.10. Step 6: Confirmation of audit results**

with the maintenance manager or the energy controller.

**3. Practical examples − Measurements and analysis**

**3.1. Allocation of electricity use − Measurement case description**

Figure 7, the plan for measurements may look like in Table 3.

**Figure 7.** Example of a schematic drawing of an electricity distribution system.

The sampling interval for the current clamps can be changed depending on what we want to know. For the air compressor we may log more frequently, for example every five seconds, if we find that the compressor is switching mode very frequently, otherwise logging at 60-second intervals may be enough.

The purpose of the continuous measurement will also affect the logging interval. If the first visit gives us the impression that the compressed air system is an important part of the energy use, we may measure more carefully to have enough information to suggest detailed measures. The drawing of the electric distribution tells us that the fuse for the compressor is 250 A, but based on the information from the instantaneous measurements we plan to carry out, we might be able to replace the 500 A clamp with a 200 A clamp.


**Table 3.** Example of plan for energy measurements to allocate electricity use to unit processes.

In this case we will have a measurement from a switchgear cabinet that covers several unit processes, for example lighting and forklift charging for a garage and picking stock, as shown in Figure 8. The data from clamp no. 1 in the switchgear must be complemented by simulta‐ neous measurements from clamps 2 and 3 in the distribution board, where clamp 2 measures the total incoming current to the Central Garage board and clamp 3 measures the outgoing current to the forklift chargers.

**Figure 8.** Part of a schematic drawing of an electricity distribution system, with locations for current clamps for simul‐ taneous current measurement, to make it possible to subtract a part of the load from the total and separate electricity

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In the example below the case is an hydraulic press, but the same procedure can be used for other equipment, for example to calculate the energy used to cover leakage in compressed air systems. With some more measurements and analysis, it can also be used for a complete

The idling energy, uptime and average power can be calculated in a few steps:

used for different unit processes.

**•** Uptime.

**•** Idling power.

building or workshop.

**2.** Log the current.

**3.2. Calculating the electricity use from logged data**

Logged data can be used for calculating:

**•** Average power for operating hours.

**1.** Measure the power factor at different loads.

Later, the data from clamp 2 in the Central Garage distribution board can be subtracted from clamp 1 in the switchgear to get a picture of the energy use in Central Picking Stock and Central Large Hall.

At the same time you have parallel measurements of the air compressor from clamp no 4. The clamp meter is placed in the switchgear, where the compressor has directly connected con‐ ductors, or in the compressor, depending on where you have the best access.

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