EFFICIENCY'S IN THE AIR

PAT NATSCHKE LENIUS

Energy costs of heating, ventilation and air conditioning systems may pale in comparison to dollars spent on refrigeration, the in-store "energy hog," but efforts to maximize efficiency are no less aggressive.

Although HVAC systems represent less than 20% of a store's total power consumption, energy management executives recognize the rewards of upgrading and modifying equipment to enhance performance and save energy dollars.

Utility company rebates

sweeten the deal and motivate retailers to do yet more.

Hannaford Bros., Scarborough, Maine, for example, recently implemented two energy-saving measures that add an "intelligent" factor to existing systems. The retailer is regulating air-handling motors with variable speed drives and, when outside weather conditions permit, an innovative cooling method that draws on outdoor air is used instead of mechanical cooling.

"The two measures we have taken are probably worth 120,000 kilowatt hours per year on average," said Tom Mathews, director of mechanical and energy services at Hannaford Bros.

Hannaford's program also earned rebates from the local utility company. "One of the rebates will continue to pay for 10 years. The others tend to be single-pay rebates to offset a portion of the initial cost," he added.

Utility company rebates may be a feather in the cap for energy management executives, but the rewards are not the sole driver for retailers taking the longer view.

Progressive retailers are seeking payback over time, in better systems performance and reduced power usage. Some of the measures being taken to bring HVAC costs in check include:

· Variable speed drives: Added to air-handling systems, the devices adjust power according to time of day or activity levels in the store.

· Intensive monitoring: Better analysis of power usage helps flag system trouble spots -- and utility billing errors that previously went undetected. Remote monitoring from laptop computers, which is done at Shaw's Supermarkets, East Bridgewater, Mass., allows for quicker response time when a problem arises.

· Lighting retrofits: Better use of natural daylight, instead of heat-generating artificial lighting, can reduce the power load of air conditioning systems.

Sometimes the energy management measures are simply procedural or involve store policy. In a bid to improve air quality and ventilation, King Soopers, Denver, now prohibits smoking on company premises.

"We had provided smoking lounges, but the cost was becoming too high to maintain indoor air quality," explained Leonard Micek, manager of engineering.

To reap long-term benefits of more efficient systems, retailers are more frequently installing regulator devices that control HVAC systems in a more economical way. The devices can be programmed to make adjustments appropriate for different times of day and outdoor climate conditions.

At more than half of Hannaford's 120 stores, HVAC equipment was modified to allow for "economizer" cooling, which uses outdoor air during moderate weather conditions.

"On a day where it might be 55 degrees Fahrenheit outside, most modern supermarkets would still require air conditioning. However, [by using economizer cooling] rather than run the mechanical cooling, it is possible to take in the outside air to provide cooling for the store," Mathews said.

"The economizer has a lot more applications to supermarkets today than in past years," he added. "Some people think it brings in too much humidity, but that is not true when done under the right conditions. You have to monitor the outside air humidity. If it is too high, you don't bring in the air."

At nearly all stores operated by Kroger Co., Cincinnati, an HVAC panel monitors inside temperature and humidity as well as outdoor temperature and time of day, according to Keith Oliver, associate manager of facility engineering at the Dallas division, Irving, Texas.

At night, or when store activity drops dramatically, the speed of ventilation fans in Kroger stores may be reduced. "The use of a two-speed, 15-horsepower motor on HVAC units results in a 66% savings of energy when operating in low speed," which is 1,200 revolutions per minute compared with a high-speed operation at 1,800 rpm, he said.

"As a result, fan horsepower is reduced from 15 hp to five hp. So, with a reduction of only 33% in air flow, about 66% less energy is consumed by the fan motor," Oliver said.

"Store conditions can be satisfied during the majority of the year by running [fans] at low speed," he added. Given an energy cost of 35 cents per kilowatt hour, annual savings are in the range of $2,000 and payback is a little more than a year.

Sometimes fans in Kroger stores may be shut down entirely. "The inertia of the air temperature in the store is sufficient during temperate outdoor conditions to allow the fan motor to remain off for up to eight hours," Oliver noted. "As the outdoor temperature drops below 50 degrees, the period of time that the motor remains off is reduced.

"This feature, along with a 'ramp warm-up' period in the morning, can provide considerable savings," he said. "Ramp warm-up simply delays back-up electric and gas heaters from turning on during the morning warm-up period, so that heat reclaimed from the condensing units can do the job."

At Larry's Markets, Seattle, a comprehensive energy management program -- encompassing lighting, refrigeration and air conditioning -- reduced total power usage in one of its stores by about 25% in a year, said Brant Rogers, environmental affairs manager.

In the HVAC portion of the program, variable-speed drives were retrofitted for the air-handler motors for the air conditioning system. In addition, a direct digital controller was installed that can control both antisweat heater cycling and the variable-speed drives for the air-handler motors in Larry's Bellevue, Wash., store.

"Where a mechanical antisweat control may keep heaters on for hours, direct digital control allows cycles in seconds or minutes. We expect savings of 40% to 50% on an annual basis," explained an engineer working on the program with Larry's.

Micek of King Soopers said there are limited opportunities to reduce HVAC operation in the chain's 24-hour stores, but tests of skylighting systems have succeeded in cutting energy costs.

"We don't have glass windows at the front of our new or remodeled stores [because] a lot of energy can be wasted through front windows," he said.

Instead, "The last two stores we remodeled in the past year have skylights. A device tracks the sun and increases the amount of light perceived by the skylight, enhancing the light coming through. This is a test right now, but we are fairly confident we will be doing more," Micek said.

Another area of development for King Soopers is more sophisticated tracking of utility bills. The chain has used a spreadsheet software program for some time but is now looking to develop a program for trend analysis.

Shaw's monitors its power usage with a spreadsheet program developed in-house, said P. Andrew Hayes, energy manager.

In addition, Shaw's refrigeration technicians monitor store systems off-site. "We have computerized energy management systems with capabilities to talk to stores remotely from the office," Hayes said.

"They log and monitor running times of the heating and air conditioning," he explained. "We keep a history of run times of the HVAC systems in the stores."