Peak consumption in energy is an expensive matter in 2 ways. First we have to make sure that our infrastructure is capable of handling those peaks plus a safety margin, which has its impact on investments or leasing costs, and of course on the ongoing maintenance and complexity of our infrastructure. Secondly, most energy suppliers charge a penalty for peaks in our consumption which exceed a pre-agreed level and believe me that those pre-agreed levels are also reflected in the fee you pay for your energy. So there is due reason to keep taking a close look at your peak consumption and what causes them.
The first step, as always, is to collect and analyze data about the occurring peaks in consumption. Best Practice method is to collect 15-minutes sampling of peak, total and average consumption for both electricity and gas. When you don’t have a local system available to collect this information, you can request your provider to deliver this. Don’t forget to make arrangements to receive this information on daily or weekly basis in the future!
Once you have your data, it is your turn to plot out PEAK, TOTAL and AVERAGE. You will get the best view when you set PEAK and AVERAGE on the same scale and axis, and TOTAL on a second axis with a matching scale to follow the curves of PEAK and AVERAGE. Also make sure that you set the beginning and end of your scale so that you can see the actual movements of the graph.
Once you have all data plotted out, you can easily identify fluctuations between average and peak. Here are some rules of thumb to get you started:
- When PEAK is much higher than AVERAGE but TOTAL is in line with the bordering values, this could indicate an upwards jump in consumption, followed by idling. Root causes for this could be unphased startup or switchovers from equipment. A practical example is switching on additional compressors to compensate for small spikes in consumption which after this goes to idling. A better control and balance of the switchover plan or controls will prevent this from happening.
- When PEAK and TOTAL increase, this clearly indicates that either “something” was switched on or various equipment came in sync and started to consume simultaneously. To understand this properly, it is important to have a good understanding and data about what is happening in production on the same timeline as your peak sampling. To allow you to analyze this properly, it is important to have production and energy data in the same data sampling frequency.
- Whatever doesn’t make sense to you is what you should focus on first. Either there is information missing, e.g. you don’t see in your production data when an additional melting furnace was started, or there is consumption which is not related to or captured as production.
- Startup and shutdown require special attention!
The basic rule applies as always: when you don’t understand the cause of the cost, you can’t explain to others where you need their support in reducing costs. Understanding and awareness is key, so make sure you understand the data and get the support you need to do something constructive with it. Contact me when needed for support in setting up your analyzing methods and bringing awareness to every corner of the organization.
This article is based on the related chapter in “HANDS-ON: Practical Energy Management”, the training method for Production Managers, Energy Managers and Operations Managers by Dr. ir Johannes Drooghaag.