By: Peter Rowles
You can’t manage what you don’t measure. This is the nuts and bolts of the continuous improvement energy management model. In energy management circles it is referred to as Monitoring & Targeting (M&T). Managing energy without an M&T program is like playing golf without a scorecard.
M&T involves the monitoring and analysis of energy use data and the reporting of this information to the appropriate personnel. M&T works by comparing actual energy use to a baseline, a budget or preset targets. In the case of preset targets, energy use is related to key performance indicators, which are typically operational factors such as production, or occupancy. By continuously comparing actual energy use against the model (or target), personnel can identify energy waste and take action to reduce waste or maintain energy efficiency improvements.
A good M&T system for utilities will assist in:
- Reducing energy costs through on-going optimization;
- Identifying energy supplier billing errors;
- Increasing options and minimizing risks for energy procurement;
- Quickly identifying energy usage problems or wasted energy;
- Prioritizing energy related capital expenditures;
- Providing feedback to managers and employees reinforcing energy awareness activities;
- Improving forecasting and budgeting of energy use and cost; and
- Enabling compliance with emissions reporting requirements.
The main components of an M&T program are monitoring, analysis, reporting and follow-up.
Monitoring involves the regular and consistent collection of energy use and energy cost data. This data can be retrieved from utility invoices on a monthly basis, from utility metering devices, which are equipped with outputs for customer use, and sub-metering devices (located in process, production or other operational areas). M&T can be applied to any energy-related consumable such as natural gas, electricity, steam, water, and/or compressed air. M&T systems can be manual, stand-alone data acquisition or integrated with existing building energy management systems. Information can be collected monthly, weekly, daily, hourly depending on the cost-benefit to the end user.
Analysis of historical energy data is used to create a baseline or benchmark against which future energy use data can be compared. The objective of this analysis is to determine the mathematical relationships (or model) between energy use and factors affecting energy use. As mentioned earlier this can include weather or specific production and operational parameters.
The resulting baseline model can be used to represent energy use in the past or expected energy use in the future. It provides a valuable benchmark for measuring the results of procedural changes that affect energy use, tracking investments in energy efficiency projects, or identifying new patterns of energy waste.
In most cases the model is a simple linear relationship correlating energy use and specific parameter such as heating or cooling degree days. In some cases, it can be more complex and may include other factors (i.e. multi-variant regression) such as work-in-process inventories, product mix, and process variables.
In addition to the baseline model, a target model should also be established based on budgets, best practices or energy reduction goals. Best practice criteria can be based on industry norms or benchmarks from similar or identical processes. The targets need to be a combination of best practices and best performance. When the targets are compared against the actual energy use on a regular basis, a framework is established for maintaining accountability and providing clear information on energy use performance.
Reporting & Follow Up
Reporting from an M&T system must provide the basis for action. These actions could include responding promptly to unexpected energy use changes or providing input into long-term decision making with respect to budgeting, forecasting or performance measurement. The application of a statistical technique called CUSUM (cumulative sum of differences) provides the ability to measure these changes. Basically, the difference between actual energy use and predicted energy use is accumulated over time. An upward trend indicates poor performance; a downward trend indicates good performance and flat segments indicate periods of consistent performance. For this reason, the continuous monitoring of CUSUM provides a good tool for short-term feedback on unexpected energy use. In the longer term, When the CUSUM technique is integrated with traditional energy reporting, it provides new information and clarifies important events. Energy related decision-making can be simplified and actions taken can become increasingly proactive.
Once operational, an effective M&T program is instrumental to measuring performance of energy efficiency projects and programs. This leads to my next topic of discussion — Measurement and Verification. How do you prove that you didn’t take any mulligans if you’re filling in your own scorecard?
Peter is entrepreneurial energy engineer with over 20 years of experience in the energy industry. Peter is a principal at ICF Marbek.