How to Attack Rising Energy Costs
- By Michael Fickes
- May 1st, 2001
School administrators have traditionally struggled to balance funding limitations and rising costs. As always, tight-fisted taxpayers demand improvements in efficiency as well as educational performance. On the cost side, teachers’ salaries continue to raise operating costs, while capital funding demands increase for building renovation and new schools to accommodate rising numbers of students and their increasingly technological educational needs.
“Teachers’ salaries are the largest general fund expense in schools,” says Allan Gaboric, senior product marketing manager for applied terminal systems with McQuay International in Auburn, N.Y. “The second largest expense is the utility bill.”
In other words, a sudden and perhaps permanent spike in energy costs has tightened the funding-cost vise on general funds and threatens to overwhelm the delicate balance school administrators have always managed -- one way or another -- to maintain.
Industry has recently begun to develop technologies designed to attack the threat posed by rising utility costs that educational facilities need to consider. These include devices such as carbon dioxide (CO2) sensors, direct digital controls (DDCs), true condensing boilers, and new approaches to heating and cooling system design.
CO2 Sensors That Control Air Replacement Costs
Schools have used unit ventilators to cycle fresh air into school spaces for more than 80 years. Herman Nelson, who pioneered the concept of bringing outdoor air directly into classrooms to prevent drowsiness, developed the technology in 1917. Some years later, McQuay International acquired Nelson’s company.
During the energy shortage of the 1970s, architects began to close off outdoor air intakes to save energy. The results included lower utility costs, drowsiness and headaches.
To solve this problem, the industry developed specifications governing minimum acceptable air replacement in schools. The American Society of Heating Refrigeration and Air-Conditioning Engineers (ASHRAE) has set this specification at 15 cubic feet per minute (CFM). Many states have adopted this standard, although some have set higher rates of replacement.
For the past quarter century, relatively low energy costs have allowed a liberal application of this standard. Classrooms designed for 30 students replace air at a rate of 450 CFM, whether 30 students are using the room or not. Gymnasiums and cafeterias designed to accommodate hundreds of people employ unit ventilators that replace 15 CFM of air for the maximum number of people expected to use the space, even when no one is there.
This inefficiency has become a primary target for industry seeking to supply tools that help schools reduce energy costs.
Scientists know that outside air contains roughly 400 parts per million (ppm) of CO2, while a human body effervesces roughly 40,000 ppm of CO2. The discrepancy allows the use of a CO2 sensor to count the number of people in a room. Controls can then adjust the ventilation of a room to match the number of people.
“You need one sensor per room,” Gaboric says. “You can buy sensors that mount on the wall or in the unit ventilator. It’s probably best to house the sensor in the unit ventilator to prevent tampering. Recent declines in the cost of this technology mean that the sensors will pay for themselves in three to four years.”
Overall, Gaboric estimates that CO2 sensors can help cut the ventilation in school spaces by 10 percent to 50 percent and generate an associated savings in the energy required to operate unit ventilators.
“In addition, manufacturers have developed DDCs through the past couple of years,” Gaboric continues. “These devices can sense temperature, humidity and CO2, while controlling outside air, the return air dampers, the amount of air that passes through a unit heat exchanger and the amount of air delivered to a space.
“DDCs also eliminate the need for pneumatic air compressors to run every day of the year. So you only use the energy needed to move the actuator stepper motor.”
Boiler Technology and Two Pipe Systems
Conventional boilers typically run at 180 degrees, according to Gaboric. Metallurgical limits prevent operation at lower temperatures since the exhaust gases produced at those temperatures tend to corrode the boiler.
Industry has overcome this problem in the past 10 years with the development of condensing boilers. “These boilers can operate at lower temperatures because they condense exhaust gases and draw extra energy from the gases,” Gaboric says. “So a boiler can go from 60 percent efficiency into the 90 percent range.”
Not only does boiler efficiency rise, lower temperature requirements for the water reduce operating costs.
By combining the savings of condensing boilers with more efficient system designs, remarkable overall savings have become possible.
Tom Durkin, PE, and principal engineer with Veazey Parrot Durkin & Shoulders of Evansville and Indianapolis, has used the efficiencies available through condensing boilers to add air conditioning to schools, with no net increase in energy costs, despite the recent cost increases in the energy markets.
“I’m an advocate of two-pipe heating and cooling systems for schools,” Durkin says. “These systems were first used about 50 years ago, but they didn’t work well. As a result, most schools use four-pipe systems, with two pipes for heating and two pipes for cooling.”
Durkin has developed a way to use two-pipe systems, with one pipe for heating and one pipe for cooling, to cut energy costs.
“The reason I got into this is that school clients wanted to add air conditioning to previously noncooled buildings,” Durkin continues. “Two-pipe systems offered a cost-effective way to do the job.”
Durkin notes that the primary concern of schools interested in adding air-conditioning lies in the first cost, or the cost of installation. Two-pipe systems cut this first cost by about $4 per square foot or $400,000 for a 100,000-sq.-ft. building.
“After I had done a couple of these systems, again because of the lower first costs, I found that two-pipe systems would also produce remarkable efficiencies,” Durkin says. “In fact, we could change a steam heated building to our two-pipe system and save 60 percent to 70 percent of the gas bill. And if we also changed a conventional hot water system to a low-temperature condensing boiler system, we can save 40 percent to 50 percent of the gas costs for the boiler.
“This is a significant savings and, when done properly, we’ve been able to add air conditioning to previously noncooled buildings with no increase in utility costs.”
One of Durkin’s clients, a parochial school in Indianapolis, converted from a conventional steam heating system to a two-pipe system last summer. Despite a significantly colder winter and the spike in natural gas prices, the school’s gas bill for the year declined by 50 percent.
The key to Durkin’s approach lies in today’s new condensing boiler technology. True condensing boilers with an appropriately designed system will operate using water heated from 125 degrees to 130 degrees when the outside temperature is zero, compared to the 180 degrees required by conventional boilers. The significantly lower temperatures slash the amount, and so the cost, of the natural gas required to heat the water.
It’s a simple idea.
“It is a simple idea,” agrees Durkin. “But like everything, the devil is in the details. It’s difficult to make it happen smoothly and completely. All of the terminal heating and cooling equipment in the building must be designed and sized to use the boiler. You cannot use halfway measures. It has to be a complete, holistic approach to building heating. But, if you can do it, there is the potential for significant savings in gas consumption.”
It’s also an important weapon in the growing arsenal available to school administrators who must mount an attack on rising energy costs.
Michael Fickes is a Baltimore-based freelance writer with experience in education issues.