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The sun’s rays shone almost perpendicularly on Evanston on Sept. 22. It was the equinox and time for this year’s tour of homes that use energy generated by sunlight to power or complement the other power sources in their homes.
Solar power is one of the fastest growing energy sources in the world, says Brandon Leavitt of Solar Service, Inc. He has been installing solar panels in Evanston since the 1980s and has outfitted 60-80 homes with solar-generating equipment. Among his most recent projects was Northwestern University’s new lakefront athletic facility.
Two of the many solar homes in Evanston show how uncomplicated it can be to harness solar energy. In the home of Dori Conn and Jeff Balch, equipped with solar panels since 1980, solar thermal technology allows water heated in pipes beneath the roof-mounted panels to flow to the basement of the home, where it is stored in two tanks. The smaller, 12-gallon tank is the heat-exchange tank, from which room temperature water is piped to the roof and to which hot water is returned. Another set of pipes takes the heated water to a larger, 160-gallon, tank.
“The water in the [large] tank is very hot,” said Mr. Balch. The system shuts off when the water temperature exceeds 170 degrees Fahrenheit.
The family uses the hot water for laundry and, at times, for heat. Another set of pipes connects the large tank to the furnace, where the hot water heats the air that heats the house in a gas forced-air system.
A few blocks away, Michael Moran’s home includes a second-floor addition that offered an opportunity to go solar, when it was constructed in 2007. Mr. Moran’s system, though about 30 years newer, is similar to that in the Balch-Conn home.
One difference is that the Morans’ two 4-by-10-foot panels heat propylene glycol, a food-grade antifreeze solution, rather than water.
“The highest level of technology is probably the thermostat that controls the system. There is a sensor up in the panels that tells the system to wake up when the panels are 7º warmer than the water in our storage tank. When that happens, small pumps push the anti-freeze solution up to the panels on the roof to go take a sunbath,” Mr. Moran said.
The heat-exchange in the basement is similar, with a smaller, 10-gallon tank holding the antifreeze solution and transferring heat to an 80-gallon storage tank that sends water – which has been heated to about 170º F – to the household taps.
“So basically, the whole system just preheats the water that goes into the water heater, and prevents it from turning on and using gas. If we’re not using any hot water for half a day or so, the water heater will cycle on to keep the 40 gallon tank ready with hot water. … You can use Monday’s sunshine in Wednesday’s shower,” Mr. Moran said. He also said, “It takes 4 months for the sun to bring the temperature of Lake Michigan up 40º, but it takes only a few hours for a solar panel to heat 80 gallons of water up 115º from 55º to 170º.”
Photovoltaic panels are an alternative to solar-thermal systems, Mr. Leavitt said. The price has come down dramatically with newer technology. “Major production costs of photovoltaics have dropped 70% in the last decade,” he said. “Illinois has traditionally had pretty strong support for solar energy,” Mr. Balch said, “but we’re up against a strong tradition of carbon-based technology.”
Federal and state incentives as well as environmental concerns are enticing people away from fossil fuels. The City of Evanston has adopted a goal of achieving a “100% renewable electricity supply for all Evanston accounts by 2035.” The City has purchased renewable energy credits to work towards this goal, according to a draft of the City’s Climate Action and Resilience Plan, but “the City also values onsite generation of renewable energy through sources such as wind and solar installations within Evanston.”
The report also recommends that the City “host a shared solar project or serve as an anchor subscriber to a shared solar project and allow residents and businesses to subscribe to the project.” There are various subscription models for solar projects. Under one model discussed in a report prepared for the Cook County Community Solar Project, subscribers which are either households or businesses can purchase or lease solar panels, place them on their property, and then get credited on their electric bills for their share of the power generated on their property.
Mr. Leavitt said, “In the ’80s, people were environment-minded. Now they are financially minded. . . . Energy is a product. You can rent it, or you can own it.”