**2.8. Step 4: Create a power balance, energy balance and allocate energy use**

When you start constructing the energy balance, you will have data with different quality – detailed production data, estimated operating time, rated data, etc. You will have data with different time spans and time resolutions - statistical data for a whole year, one week meas‐ urements, instantaneous measurements, etc. The data will also describe different parts of the energy flow - sometimes the energy supply, sometimes the usage and sometimes the energy loss. In Figure 5, an example of an energy balance is presented.

Below some different common cases related to allocating energy use are outlined.

Case 1 - All the supplied energy is allocated to one specific unit process. Sometimes you can find this phenomenon for support processes, such as fuels for internal transport or district heating for space heating. Some of the supplied energy can also be very specific for a certain production process, such as gas for welding or liquid nitrogen for cooling.

Case 2 - Almost all of the supplied energy is allocated to one specific unit process – all you have to do is to take something away. In Figure 5 this is the case for Space Heating and Hot Tap Water which are the only processes supplied by the oil boiler.

This can often be the case when you use a hot water system for both production and Space Heating and Cooling. One example is a district heating hot water supply used for both a washing machine for surface treatment and for the indoor climate and space heating system. The space heating is mostly weather dependent and varies with the seasons. The energy use of the washing machine totally depends on the rate of production. Given that you have at least monthly data from the district heating supplier and that you know the production rate during the summer, when the heating system is mostly turned off, you can estimate the energy use for the washing. Then you can compare the energy use during the summer and winter, subtract the energy use for washing and assume the rest to be heat for space heating and air handling.

**Figure 5.** Energy balance for an audited plant [19].

add the power used by the ballast (control gear). Make sure to find out if it is a magnetic ballast (very common, always in older installations but still used today) or the more modern electronic ballast. Magnetic and electronic ballast differ in power use. For light strips with the common magnetic ballast it means multiplying the rated power by 1,2 and for the more modern elec‐

The uptime for the lighting might be hard to find out. You can simply ask the staff, log the light or temperature at selected light sources or log current used for lighting to be able to see

This step is performed to find out what equipment is operating during non-production hours and find out if it must be operating. You might find support processes - lights, air handling units, compressors - being switched on though there is nothing to support, but also production

Eyes and ears are useful to find equipment running during non-production hours. The meas‐ urement methods used are the same as during production hours, but the focus may be on other

When you start constructing the energy balance, you will have data with different quality – detailed production data, estimated operating time, rated data, etc. You will have data with different time spans and time resolutions - statistical data for a whole year, one week meas‐ urements, instantaneous measurements, etc. The data will also describe different parts of the energy flow - sometimes the energy supply, sometimes the usage and sometimes the energy

Case 1 - All the supplied energy is allocated to one specific unit process. Sometimes you can find this phenomenon for support processes, such as fuels for internal transport or district heating for space heating. Some of the supplied energy can also be very specific for a certain

Case 2 - Almost all of the supplied energy is allocated to one specific unit process – all you have to do is to take something away. In Figure 5 this is the case for Space Heating and Hot

This can often be the case when you use a hot water system for both production and Space Heating and Cooling. One example is a district heating hot water supply used for both a washing machine for surface treatment and for the indoor climate and space heating system. The space heating is mostly weather dependent and varies with the seasons. The energy use of the washing machine totally depends on the rate of production. Given that you have at least monthly data from the district heating supplier and that you know the production rate during the summer, when the heating system is mostly turned off, you can estimate the energy use

**2.8. Step 4: Create a power balance, energy balance and allocate energy use**

Below some different common cases related to allocating energy use are outlined.

production process, such as gas for welding or liquid nitrogen for cooling.

Tap Water which are the only processes supplied by the oil boiler.

loss. In Figure 5, an example of an energy balance is presented.

tronic ballast it means multiplying by 1,1.

**2.7. Step 3: Visit the company during non-production hours**

the true uptime and downtime.

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processes in idle or stand-by mode.

processes.

Case 3 - Many different unit processes have the same supply, but at least some of them are running in a predictable way. This is often the case when it comes to electricity, as seen in Figure 7. From the switchgear or the distribution board, where you often have the practical possibility to measure, electricity is supplied to many different processes. Typically you find all the processes in one part of the building mixed. Even if the distri‐ bution board is totally dominated by one production process, like a laser cutter, you might also find support processes for that production process, like a compressor and a chiller, attached to the same board. The energy use for the laser cutter itself will vary a lot, but if the chiller works constantly as soon as the cutter is on and the uptime of the compressor already is measured for service reasons, you might be able to allocate the energy use by logging the total current to the distribution board.

It should be noted that the above table concerns energy costs. As regards reduced energy use, load management is not an energy-saving measure as it solely shifts the use of energy to times where it is more appropriate. Moreover, change of energy carrier may be a splendid way to reduce the use of non-renewable resources or energy costs. However, it may not lead to re‐

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duced energy use.

**Figure 6.** Energy balance after suggested adjustments [19].

If you have a common supply for even more processes, try to find the ones with constant power use, like light strips, or constant power use and programmed uptime, like air handling units with constant air volume and an autotimer.

Case 4 - A process has more than one energy supply. This is of course a common case. In a building with many air handling units, the units are all doing the same job – they are running the ventilation process. Even if there is a central remote control system for all air handling units, usually the energy use is not logged. The solution is to add up all the air handling units, accepting that your input data quality will range from rated power and estimated uptimes to detailed measurements.

You can also have one process with different energy carriers, e.g. a dryer consisting of an electric fan and a hot water heater. If you are not able to register everything, you might be able to use data from one of the carriers to calculate the uptime for the other. For example, the temperature of the heat exchanger can reveal if the fan is running or not.

You might also find two separate electricity supplies to the same unit process for safety reasons, i.e., two separate air compressors connected to two different switchgears to prevent stoppage. Of course you can have more than one supply to a single unit process for other reasons, for example if the electric distribution system has been supplemented because the process needs more electricity than the original switchgear was designed for.
