Learning to harness sunshine

May 28, 2009

Contractors from as far away as Toledo, Ohio and Huntington, W. Va., came to Cincinnati State recently to attend a three-day training session on solar hot-water systems.

Participants met for two days in the renewable energy lab at Cincinnati State to hear presentations about the theory and practice behind solar thermal applications, and to learn how to install solar thermal devices. Among those addressing the class were Larry Feist, chairman of the Energy Efficiency and Renewable Energy program at Cincinnati State, and Athan Barkoukis, a program manager for Green Energy Ohio, a nonprofit statewide organization dedicated to promoting environmentally and economically sustainable energy policies and practices in Ohio.

The highlight of the session came on the third and final day, when the class – under the tutelage of Carl Adams with SunRock Solar – installed a full-size, commercial grade solar thermal system at the Maple Ridge Lodge in Mount Airy forest.

Class members installed adjoining 4’ by 8’ collectors (each weighing about 125 pounds) on the roof of the Depression-era structure, then connected insulated copper pipes that ran through the attic and connected with an 80-gallon hot water tank.

The system is elegant in its simplicity. On days when sensors indicate that there’s enough sunlight available to make it worthwhile (essentially, whenever there’s daylight and the collectors are not covered by snow) a small pump sends water in a closed loop up to and through the collectors. On a bright summer day the water in this loop will be heated to as much as 300 degrees Fahrenheit; even on an overcast day the temperatures will generally be well above 100 degrees. The heated water then returns (by gravity) to the hot water tank, where it moves through a heat exchanger and warms the water in the tank.

The tank is equipped with a small, gas-fired auxiliary heater for days when there isn’t enough sunlight to adequately meet demand. But Adams and others report that even on a bone-chilling day in winter, the solar panels are usually able to keep the water in the storage tank at a minimum of 80 degree F or so, thus greatly reducing the demand for natural gas heat to bring the temperature up to a usable range.

By the end of the afternoon the Maple Ridge Lodge system was in place, complete with a special display in the main room of the lodge to show visitors how well it’s working.

The ballpark cost for a private installation of this size would be between $8,000 and $10,000, but state and federal tax credits would reduce the cost by about 30 percent. The professional installers estimate the payback period for such a system in a residential setting is typically six to seven years.

For more information about Cincinnati State’s renewable energy program, contact Larry Feist. For information about Cincinnati State’s sustainable design program, contact Ralph Wells.