Real-time control and continuous high-quality building performance data are the keys to reducing building energy use during day-to-day operations, and to maintaining energy-driven services and occupant comfort. Next-generation highly energy-efficient buildings will be dynamically controlled and monitored.
Energy information systems (EIS) are one type of commercially available system that provides this real-time continuous stream of monitoring information, usually in large commercial and industrial buildings and facilities. Scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) recently studied the capabilities of marketplace EIS, and their use in several large facilities, with the goal of working toward improved systems that will be easier to install and to use; ultimately they will drive buildings toward greater energy efficiency and lower costs. The Berkeley Lab team is developing a handbook and other materials to make it easier for facilities managers to use and specify EIS.
"Energy information systems can process building performance data and turn them into actionable information," says Jessica Granderson, one of the authors of a study on the state of EIS technology. "They make energy data visible to building and facilities managers, helping them reduce unnecessary use, and pinpoint problems with systems that are wasting energy." Granderson is a scientist in Berkeley Lab's Environmental Energy Technologies Division (EETD).
With funding from the California Energy Commission, Granderson and her colleagues studied the capabilities of energy information systems available in the marketplace, and conducted case studies of how an EIS was used by campuses or large enterprises—Walmart; Sysco; the University of California (UC), Merced; and UC, Berkeley as a contrasting case. Their purpose was to determine how the features of various systems helped managers save energy, and what kinds of improvements could help managers do their job better.
"The typical EIS provides at least hourly whole building data on electricity use, with weather, gas, and system submeter information, depending on the particular implementation," says Granderson. "They offer the capability to visualize this data graphically, as well as automated analyses. For example, a building's metered use can be compared to its baseline or to billed utility use.
In the field, the team found that an EIS helped motivate facilities managers to achieve major energy savings, isolate and identify problems with equipment, and manage energy use. But energy managers are time-constrained, and the study found that managers don't always have the time and resources to use the full analysis capabilities of their EIS.
Sysco is one of the largest food distribution companies in the U.S. The company had a corporate goal of improving enterprise-wide energy use 25 percent over three years—a goal that it has exceeded. Granderson studied Sysco's use of an EIS in its Stockton, California, food distribution center, which refrigerates large storage areas to keep food fresh.
At the Stockton facility, an "energy champion" on the facilities staff used a single meter monitor (a graphic on the computer screen showing continuous power use) to keep the temperature of the building's conditioned spaces within the required cooling limits, turning the system on and off as needed. Manual control of the conditions in the space saved 36 percent of the cooling demand when the staff member was present and actively managing the system.
The EIS also helped identify excessive energy use—for example, at the end of the work day, when the electric load didn't decrease as expected, building staff were able to trace its cause to lights that weren't being turned off when workers left the building.
Walmart used its EIS for a number of purposes, including verifying the performance of specially designed high-efficiency superstores. The Berkeley Lab team learned of examples from the company's energy managers in which the EIS showed its worth by identifying systems that weren't working right and were wasting energy. One malfunctioning module for dimming the lighting in a Texas facility, after being fixed, resulted in avoided costs of $35,000 in energy costs.
And at UC Merced, an EIS helped an operator determine that the steam plant was using excessive gas. The 30 percent reduction in gas use at that steam plant saved about $2,500 per month.
"Large savings are possible with an EIS and an innovative operations staff," says Granderson, "as these case studies demonstrate."
The study notes, for example, that analyzing electric load profiles can reveal historic trends in energy use and opportunities for improvement. Daily forecasting of electricity loads, which some EIS can produce, can help facilities staff carry out a daily energy efficiency strategy, customized to such factors as the forecasted weather and the real-time electricity cost.
The EIS scoping study and case studies were the first in a recent EETD research and development program focusing on how to better deploy and scale up the use of the EIS in facilities. With funding from the U.S. Department of Energy, Granderson and her colleagues are developing a handbook for energy managers who have little or no experience in analyzing building energy data. "The handbook will be heavy on application examples—how to interpret what you see in EIS and related performance-monitoring technologies. It also highlights the energy benefits of applying various analysis methods," she says.
The team is also developing a guide specification for EIS and other types of energy-performance monitoring systems on the market such as EMCS (energy management and control system). "The guide spec will help building owners and energy managers better understand what types of capabilities are available," Granderson says, "and will make it easier for them to specify the technical requirements of these systems when they are ready to acquire them for their buildings."
This research is supported by the U.S. Department of Energy, and the California Energy Commission's Public Interest Energy Research program.