Taking Solar Energy to the Cities

The project was funded by $1 million in Recovery Act funding from the Department of Energy’s Solar America Communities program as well as by matching funds from District Energy St. Paul, a Twin Cities utility company that heats 80 percent of downtown buildings in the city.

The Twin Cities have teamed up to jumpstart the widespread deployment of solar technologies as part of the Solar America Communities program. Together, the two cities have launched the Solar in the Cities initiative, which takes a comprehensive approach to expanding solar energy in Minneapolis and St. Paul. The Twin Cities are marshalling a wide array of expertise to implement commercial and residential solar installations, provide technical training programs, and conduct a review of city and state policy.

We spoke with Susan Carollo, who works for the Department’s Solar Energy Technologies Program. Susan told us more about the Solar America Communities program and more specifically, the Twin Cities’ Solar in the Cities initiative.

“There are several facets of the Department of Energy’s solar program, including the SunShot Initiative, which is committed to reducing the cost of solar through research and development, but what Solar America does is decrease the ‘soft costs’ of solar. These can be costs associated with installation, permits, training — all things that happen at the local level,” she said.

According to Susan, the Twin Cities initiative is unique for a few reasons. First, the two municipalities applied to the program together and have now partnered with the local utility to launch the centralized solar thermal project at the St. Paul RiverCentre. The other 24 cities in the Solar America Communities program, which are located across the country, are taking part in the program as independent municipalities.

Second, the Solar in the Cities projectis the first project of its kind in the United States. The project will heat water for the convention center’s restrooms and kitchens, and warm the 162,000-square-foot building’s indoor air. Any leftover energy will flow into a hotwaterheating loop built by District Energy. The solar energy that is not used by the building will be directed out into a hot water distribution network serving the city’s downtown area. District Energy will operate this installation as an additional energy source for its current heating system, which already receives the majority of its energy from a biomass-fueled combined heat and power plant. According to District Energy, the rooftop project could supply up to five percent of the district’s needs for heating water in the summer and one percent of total demand year-round.

According to a National Academies Press report, district heating and cooling systems are thermal energy networks that distribute waters at different temperatures through insulated pipes for heating and cooling purposes throughout a core of high-use buildings (like a business or university campus, military base, multifamily residence — or in this case the downtown area of St. Paul). While the use of solar power in district energy systems is popular in Europe, this is the first time the technology has been applied to a city in the North America. Officials at the utility company and the Department of Energy hope this installation will spark interest from other cities.

The installation itself will add 144 solar thermal collectors to the existing energy districtin Saint Paul, and produce hot water for space heating and domestic hot water. The system will reduce carbon dioxide emissions by 900,000 pounds annually — the equivalent to eliminating 90 vehicles from the road each year.

By April Saylor, Online Content Producer and contractor to the Office of Public Affairs, blog.energy.gov/