Although expensive, the accurate monitoring of energy consumption and building operations is a necessary part of conservation savings analysis. Energy management and control systems (EMCSs), intended for building operations and control functions, already contain most of the same equipment usually installed for energy monitoring and can often be used for this application as well. Since building owners and managers are installing EMCSs in an increasing number of commercial buildings, with proper planning, conventional energy-monitoring equipment might be unnecessary.
However, EMCSs are not designed with end-use monitoring in mind. The features of an EMCS are determined by building rather than monitoring needs, so EMCS-based monitoring faces complications. Differences between the EMCS models, the installed options at sites with the same model, or the degree of system use at a site mean the difference between a system that can be put into service for monitoring energy right away and one that cannot be used at all. Assessing which systems will work is often difficult.
Although there is a wide range in EMCS characteristics, most current- and next-generation EMCSs contain sensors, sophisticated networking hardware, data-storage algorithms, and communications hardware and software, all of which make the EMCS an ideal platform for commercial building performance monitoring.
There are several methods for connecting to an EMCS to collect data. One can tap into the EMCS at a fairly low level and use a data logger, taking advantage of the existing EMCS sensors. Or one can make use of the EMCS's data collection, computation, and reporting capabilities by connecting at a higher level and collecting summary reports. In the latest generation EMCSs, the complex network architecture, multitasking capabilities, and standardized operating systems permit quick and simple data transfer. The best method to use will depend on the characteristics of the EMCS and the needs and resources of the monitoring program.
Some time ago, we evaluated the use of EMCSs as energy monitors in five buildings in Texas and California and developed guidelines based on these evaluations. The guidelines address how to determine whether the elements necessary for energy monitoring are present and what to do if they are not. Recently, we tested these guidelines in several buildings and evaluated their usefulness to the assessment process.
Our evaluation discovered that confounding human factors can override the technical aspects of EMCS monitoring covered by the guidelines. Included in this category are such nontechnical issues as the sharing of system resources and the availability of system maintenance staff when an external party uses equipment owned by building management and designed for control rather than monitoring. We interviewed energy management and EMCS operations staff at several sites to explore these issues. Using an in-place EMCS for monitoring requires assistance from on-site personnel for assessing capabilities, reconfiguring the system, and other consulting during monitoring. In all projects, and especially in EMCS monitoring, it is important to identify organizational contacts with the information, resources, and incentive to help.
We have begun an in-depth case study of EMCS monitoring involving a laboratory building at LBL that was also the subject of a pilot study of shared savings. An outside contractor installed retrofits, and a fraction of the savings realized by the owner will be paid to the contractor, who is responsible for monitoring the building and estimating the savings. The method for determining savings from the retrofits was clearly specified in the contract and will include the use of the EMCS for monitoring. To verify these savings estimates, LBL's in-house energy management group has installed its own submetering.
The next phase of this research will compare the savings estimates resulting from the EMCS-based monitoring and those of the more conventional submetering. Also, we expect to make more detailed engineering estimates of savings with the operational and consumption data collected by the EMCS. A comparison of the resulting savings estimates and the different processes for collecting and analyzing data should reveal a lot about how well the EMCS does its new job.
--Kristin Heinemeier
Kristin E. Heinemeier
Energy Analysis Program
(510) 486-7283; (510) 486-6996 fax