Measurement and Verification: Of Energy Management Systems
| Authors: | Brad Acker, Kevin Van Den Wymelenberg |
| Published: | March 2, 2010 |
| Links: | Pre-print pdf |
| Background: | Energy management systems (EMS) can take many different forms but most systems control HVAC equipment and lighting systems. Some systems are installed to control several aspects of a building including lighting and HVAC set points and schedules while other systems are installed with stand alone control of single systems (for example lighting only). EMS can help in reducing energy use, improve thermal comfort and indoor air quality, while at the same time lowering maintenance costs (Piette et al, 2001). EMS control of HVAC systems often couple differing temperature setpoints with multiple schedules and occupancy sensors, and provide “soft starts” for equipment or systems that slowly ramp toward comfort parameters to avoid energy spikes and reduce equipment ware. Used with lighting systems EMS often control schedules, lighting levels and interface with occupancy and daylight photocontrol systems. A complete list of all control parameters is not possible because different buildings have different programs, user needs, and performance criteria. Advancements in computing technologies, sensors, and the industry trend toward open source program languages have allowed EMS to evolve in order to meet a wide range of customer needs.
The role that the EMS plays within the building is in large part dependent upon building operators and institutional goals for, and commitment to, energy and comfort performance criteria. Some building operators use EMS as an operational tool to enhance traditional equipment, providing alarms when maintenance is needed, and to schedule equipment use. The use of EMS often times does not go beyond this level of implementation. Systems that track total building energy use and disaggregated end use by sub-system are often referred to as Energy Information Systems (EIS). Advanced building operators capture this energy use information for benchmarking and continuous improvement purposes. In general, as awareness regarding energy use in buildings increases, building operators and owners are becoming more sophisticated in their use of this information and how it can be used to reach company energy goals, however additional research, and subsequent training and education is required in order for EMS to realize a greater proportion of its potential. Determining the energy savings potential or the realized energy savings of EMS installations is incredibly difficult. Essentially, EMS is a tool that allows building operators and in some cases, building occupants, to balance and prioritize occupant comfort, energy savings, and equipment maintenance routines. When EMS is utilized effectively it can increase user comfort, increase energy savings, prolong equipment life, help to properly schedule maintenance, and save facilities staff time when troubleshooting. However, determining the energy savings of an EMS in a unitized fashion would require an extremely large sample size. This paper proposes a method for estimating energy savings associated with EMS and reports on the results of applying the method to four case study buildings in Idaho. |