The next time students in Howland take a hot shower, it will be with water heated by the sun. The first week in April witnessed the construction of ten solar hot-water panels on the roof of the rambling, flat-roofed dorm, the latest in a series of moves by Marlboro to increase energy efficiency of campus buildings and rely on more renewable resources. The panels, which turn the sun’s radiation into a usable heat source, were made by the German company Schüco, a world leader in energy-efficient buildings. Each thermal collector measures 28 square feet and has pipes running through it with a non-toxic, anti-freeze fluid, which picks up the solar heat and transfers it to three 80-gallon hot water tanks inside the dorm.
The panels are each rated at 33,400 BTUs (British thermal units) a day, enough to raise the temperature of approximately 433 gallons of water from 45 degrees to a comfy 122 degrees. If you figure on a 10-minute shower, which is certainly an underestimate for your average college student, all ten panels can theoretically provide 170 showers-worth of hot water. Of course that’s with perfectly sunny days and perfect efficiency, or no heat loss in the conversion from the solar-heated fluid to the domestic hot water and no “static heat loss” when the hot water is sitting in the tanks and pipes. Still, all things being imperfect, the thermal collectors should take a big chunk out of Howland’s heating oil use, particularly in the summer when the boiler is only running to heat water.
The three hot water tanks do stand to be more efficient than most systems, thanks to an innovation introduced by Dan Cotter, director of plant and operations. Most systems like this work by “preheating” the water, which then goes to the boiler hot water tank to bring it up to the appropriate temperature. When the hot water in the boiler tank has cooled because of static heat loss, a normal system will start augmenting the water temperature with oil heat, even though there are still three 80-gallon tanks full of perfectly good, solar-heated, hot water. Dan, being the no-nonsense practical Vermont (actually New Hampshire) kind of guy that he is, insisted that it would be more efficient to prioritize the tanks of solar-heated water first, before re-heating any of it with the boiler. Schüco agreed and eagerly re-engineered the system to Dan’s specifications, proving that we are not so far removed from the perfect world after all.