WAHIAWA, HAWAII-The energy mandate facing the Army- reduce building energy consumption by 30 percent by 2005-is no small challenge. Yet an installation of microprocessor-based controllers on boilers and hot water heaters at the U.S. Army Garrison here in Wahiawa has already solved most of the facility's requirements for water heating with years to spare.

The units, each only a little larger than a shoe box, have cut down on fuel consumption by 23 percent to 26 percent, for a savings of more than $ 177,000 a year. Payback is estimated at a year and a half.

Microprocessor control units, installed on boilers and hoi-water healers, assimilate operating data and automatically determine how long to keep the unit in its "off" cycle, reprogramming she equipment to perform more efficiently.

A vast military installation that includes Schofield Barracks, Fort Shatter, Wheeler Army Airfield, and Helemano Military reservation, the US Army Garrison in Hawaii houses 15,000 soldiers of the 25th Infantry Division. Located near the city of Wahiawa on the island of Oahu. It spans 30 million square feet of building space, and runs an annual energy tab of $30 million.

While the electric heat pump has been one of the local methods of conserving energy in Hawaii, the Army discovered that alternatives are worth a second look. Despite Hawaii's moderate temperatures, humidity and salt in the air can wreak havoc on that equipment, and the state has one of the highest electric rates in the country.

MICROPROCESSOR CONTROLS BOILERS

That's where the Microtherm L.L.C. computers came in. When a unit is installed on a boiler or hot water heater, it monitors the daily routine of the equipment, including its cycles and temperatures.

The microprocessor in the unit assimilates the information, automatically determines how long to keep the boiler or water heater in its "off" cycle, and reprograms the equipment to perform more efficiently. The unit determines if the boiler is oversized or has extra capacity, and scales back the equipment's ignitions to meet the actual needs of the facility. "The computer literally learns what the personality of the boiler is," says Todd Scheibert, owner of Scheibert Energy Co., and the local distributor for the computer manufacturer. "It learns how long it took for the boiler to recover inthe last cycle, how far the temperature dropped, and how far the temperature went up before the boiler shut down. It learns this and then it determines how long to hold the boiler in an 'off' condition to maximize the 'off' cycle."

The Army first agreed to experiment with the units in 1997. At that time, after Scheibert proposed a free trial period, the Army's energy manager, Scott Ely, agreed to the installation of three units. They tested the units for six months on three different systems: a propane manifold system, an individual propane tank, and a diesel, low-pressure boiler fired on diesel fuel.

IMPRESSIVE RESULTS

Impressed with the results. Ely finalized the deal: $260,000 for the 100 units and their installation. Most were installed by July of 1998 on heaters and boilers used for showers, laundry, and food preparation at Schofield Barracks. "We considered adding timers to our boilers or converting to heat pumps, but neither could provide dependable, cost effective, low-maintenance savings and performance of the unit," says Bly. "Although the heat pump may have a higher efficiency rating, the maintenance costs have outweighed the energy savings. Many of our heat pumps failed due to the rust caused by the environment and substandard materials."

In 1997, before the installation, the garrison's propane consumption for July through December totaled 283,595 gallons, averaging 47,265 gallons a month. At the time, 71 boilers were operating. A year later, after the installation, when an additional 10 more boilers were in use, fuel consumption dipped to 250,232 gallons for the same six-month period, for an average of 41,704 gallons a month. End result: A cost savings of $14,785 a month. (The remaining units were installed on synthetic natural gas or diesel-fired boilers; there is no analysis of (hat data.)

SCALING BACK

In many cases, boilers or hot-water heaters are oversized to meet the toughest of conditions, starting and stopping many times a day-often wasting fuel and money and spewing more pollutants than necessary into the atmosphere. Depending on the equipment, a unit may scale back the number of ignitions by 25 or 30 each day, without reducing the temperature. In the case of Schofield, "Every boiler had savings, some were higher, some were lower," says Scheibert. "We had some boilers that got as high as 50 percent savings. They were very much oversized." He adds, "Whenever a boiler turns on, the combustion is very inefficient."

By running diagnostics, the units also identify problems with equipment or ground wiring. At Schofield, the diagnostics test identified some problems with old equipment, which was replaced or upgraded. "In many cases, the installer or diagnostic computer identified opportunities for even greater savings," says Bly.

The unit is a plastic box with a printed circuit board and viewing screen inside. It snaps onto the surface of the boiler, or in some instances at Schofield, on the wall in the boiler room. The unit is equipped with a temperature sensor that attaches to the outgoing hot water pipe, and will override the device if the temperature falls below a programmed minimum temperature because of a sudden change in demand.

FAST PAYBACK

"This is the simplest retrofit project I have been involved with, and it provided the fastest payback," says Bly.

The project is part of a sweeping energy conservation program at the US Army Garrison-Hawaii (USAG-HI), which includes lighting retrofits, chiller replacements, daylighting, and cogeneration. "Microtherm L.L.C. contributed to the USAG-HI being selected as a winner in the Secretary of the Army Energy Conservation Award," says Bly. USAG-HI has claimed the award for the last three years.

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