**Author details**

In this case a close calculation based on the raw data gave a similar result (5176 kWh) to the rough estimate, but that is mostly because the same assumptions were used. Changing the duration or average power just a little affects the result a lot. The power factor at partial load

Together with information about the rate of production and the working hours, the annual

If this is a representative production week, the result can simply be multiplied by the number of working weeks per year. In this case it is not a typical week but information from the pro‐ duction manager tells us the working days are representative. The average power use during working hours can be calculated and multiplied by the number of working hours per year. In this case the rest of the year can be considered as standby time. In other cases equipment can

We know from previous calculations that about 35 percent of the energy use during working hours is really idling energy. That information is not needed for the allocation of the energy use to the right unit process, but it is important information for further analysis and to suggest measures. A closer look at the graph of the current used during a week also reveals that the machine sometimes is idling for more than one hour without producing (see Figure 9). One example is Monday before midnight, when it is idling for about two hours before it is at last turned off for the day. An automatic control system or changed routines for the operator can be used to switch to standby mode faster. The aim of the analysis was to be able to calculate

This chapter has presented the energy audit methodology being developed at the Division of Energy Systems at Linköping University for a period of more than 30 years. Despite extensive research and experience in the field – about 500 energy audits have been carried out based on this methodology - the energy audit methodology has not been explicitly outlined previously. This chapter may therefore still contain areas for improvements. This chapter has for example

**(h/year)**

**Energy (MWh/year)**

and at standby load is also unknown, which affects the accuracy of the calculations.

*3.2.5. Analyse the data again*

138 Sustainable Energy - Recent Studies

energy use for this equipment can be calculated.

be completely turned off during longer holidays.

**Table 6.** Calculated annual energy use for a hydraulic press.

**4. Concluding discussion**

**Mode Power, average (kW) Duration**

the energy use, but on the way some possible measures were also found.

Working hours (active and idling mode) 84 3456 290 Standby 3,5 5304 19 SUM 8760 309 Jakob Rosenqvist\* , Patrik Thollander, Patrik Rohdin and Mats Söderström

\*Address all correspondence to: jakob.rosenqvist@liu.se

Department of Management and Engineering, Linköping University, Linköping, Sweden
