San Diego Convention Center Reduces Electric Bill, Monitors Power Quality With Submetering

Oct 15, 2003 12:00 PM, Don Millstein, E-MON LP

With today’s high cost of energy, just paying the electric bill for an average home can cause sticker shock. Imagine, then, how the operators of the San Diego Convention Center—a seven-city-block long, 2.6 million sq-ft state-of-the art complex—must feel. When you factor 72 rooms and a 25,000-sq-ft kitchen into the mix, fewer priorities are higher than trimming the fat from the facility’s giant monthly power bill.

The perennially high cost of California energy is only one of the factors that drove the need to lower operational costs in this sprawling conglomeration of public exhibit halls, conference rooms, offices, and underground parking areas. The recently completed $216 million expansion project has also added significantly to the convention center’s electrical load.

Realizing that he couldn’t save what he didn’t measure, Ron Barham, operations/electrical manager for the San Diego Convention Center Corp., investigated the situation and suggested that the convention center select a submetering system that would allow facility engineers to monitor, record, and report energy usage as a tool for conserving energy and for lowering overall operating costs. The selection of the system was based on price, customer service, and flexibility in allowing future expansion. The company also needed a hybrid solution in order to record power consumption and demand and monitor power factor, total harmonic distortion, and other power quality parameters.

The facility’s main electrical service entrances are located in two large sub-level electrical vaults, where multiple 480V 1,600A and 3,200A loads are individually submetered. Low-voltage output current sensors, installed around the electrical feeds in both vaults, supply the raw electrical data to five submeters in the west vault and four in the east. A computer interface module in each vault accumulates pulse outputs from the individual submeters, digitizes the data and transmits it via RS-485 communications link 1,600 ft to the laptop PC in Barham’s office.

The Windows-based software installed in the laptop can display electrical data gathered in 5-min, 15-min, 30-min, or 60-min intervals. The load data is exported to a spreadsheet for analyzing energy consumption, accounting, and other functions. “Thanks to real-time metering capability, we’re able to look at our energy consumption and make load adjustments in real-time to avoid additional ratcheting charges, thus saving energy dollars,” Barham said.

The program can profile the information in a number of ways, allowing management to view energy consumption, demand, and power quality functions in real-time. Power quality or monitoring problems are time-stamped for Barham and his team to investigate, and, in this way, areas of inefficiency are quickly identified and corrected.

Currently, nine of the 11 meters in the convention center complex are submetered, with the remaining two meters slated for retrofit by the end of this year. Up and running for more than two years now, the submetering system has already paid for itself in terms of the savings. Barham estimates that the convention center saves about $13,000 a year.

“Business decisions are easy to justify if they have a positive impact on the product we deliver to our guests,” Barham says. “The whole point of the exercise was to better understand how and when our energy was being used, to use our resources better, and to offer a superior product to our guests. This system helps us do that.”

Millstein is president of E-MON LP in Langhorne, Pa.