Posted: 2/6/07
School may modify heating system
by Tom van der Linden
Special to the Caledonia Argus
Would you pay $1,800 for a new furnace if it saved you $500 each and every year thereafter?
You would if you were good at math, because the payback on your investment would be less than five years. After that, the savings would be all yours.
Caledoniaís school board has a similar decision to make: should it invest $181,000 to modify its modern, geo-thermal heating system, in order to save $51,000 per year?
The school board was set to make the decision Monday, at a meeting held after the Argus went to press.
Superintendent Mike Moriarty is recommending the investment, based on a study by Michaels Engineering, La Crosse, which projects the energy savings.
"Thereís less than a four-year payback, thatís why its attractive," said Moriarty.
Caledonia High School was built about six years ago with a state-of-the-art geothermal heating and cooling system. However, the "latest and greatest" ideas change fast in the world of energy efficiency.
With the high school schoolís energy bill sucking about $7,000 a month out of the budget, officials invited in Tri County Electric for an energy audit. Getting everyoneís immediate attention were two 100-horsepower pumps which run day and night. They circulate a mixture of water and antifreeze deep into the earth, from which heat is absorbed.
One pump takes the water into the ground and brings it back to the surface. The other pumps water to and from the school. Both meet at a heat exchanger, where the school loop takes heat from the ground loop.
Michaels Engineering has proposed fusing the two loops into one, thus eliminating one pump. A special three-way valve is required.
Energy savings: $35,000 per year.
An even simpler modification to the schoolsí fresh-air ventilators will save the other $16,000 per year.
The ventilation fans run constantly, attempting to reduce the carbon dioxide level in the school to the same as outdoor air, roughly 300 to 500 parts per million. But, thatís wasteful and not necessary, recommended Michaels. By setting the carbon dioxide sensors to 700 part per million, the school will have plenty of fresh air, while the fans will run less.
As the pumps and fans consume use most of the energy used at the school, optimizing these systems seems to be a smart idea. By contrast, lighting swallows only 16 percent of the energy used at school. Moriarty said the schoolís lights are efficient.
A school system is a big energy user in a small town, using roughly the same energy as 180 homes.
Caledonia Argus
314 West Lincoln St.
P.O. Box 227
Caledonia, MN 55921-0227
507/724-3475
E-Mail: editor.argus@ecm-inc.com