District Energy St Paul Minn has the Midwests largest solar thermal project

District Energy St. Paul (Minn.) produced the Midwest's largest solar thermal project, which heats 80 percent of the buildings in downtown St. Paul. It was made possible by a $1 million grant from the U.S. Department of Energy's Solar America Communities program and matching funds from District Energy St. Paul.

Solar Heating Considerations for Green Schools (with Related Video)

Understanding the process of installing solar thermal systems can help schools determine whether it will meet needs now and into the future.

As energy costs continue to rise, many schools and universities are considering energy-saving solutions, including solar heating options, to lower costs and to attract students and staff that support environmentally friendly practices.

However, administrators and facility engineers should take several issues into account before pursuing a solar heating system.

Solar System Considerations

When contemplating whether a campus is a good solar candidate, administrators should consider whether the system would be integrated into a centralized system or if the current system is decentralized around the campus; whether the campus has available space on rooftops or land to house solar panels; and whether the solar project would be part of new construction or retrofit to an existing facility.

In addition, campus managers need to determine the year-round heating and domestic water needs and evaluate solar options compared with the current use of other energy sources, including natural or propane gas, fuel oil and electric.

Last year, District Energy St. Paul produced the Midwest's largest solar thermal project. The project offered additional energy output to District Energy's distribution system, which heats 80 percent of the buildings in downtown St. Paul. It was made possible by a $1 million grant from the U.S. Department of Energy's "Solar America Communities" program and matching funds from District Energy St. Paul.

For this project, the solar thermal system was integrated with a central district heating system for the city-owned, 162,000-square-foot convention center. It consisted of 144 solar thermal panels, measuring 20-feet-long by 8-feet-tall, connected in a series of six to seven panels. The new system offers peak energy production of 1.2 megawatts and reduces carbon-dioxide emissions by 900,000 pounds annually. The system was retrofitted atop the city's convention center, which offered more than 1 acre of unshaded area, roughly half the size of a football field.

Additional items for education institutions to consider when exploring energy-efficient options include whether a solar application could be used to support curriculum that teaches alternative energy design; whether a school emphasizes green initiatives to new students and faculty; and if a campus has remote buildings that require heat or electricity.

Recently two solar projects were completed for Dakota County Technical College, Rosemount, Minn. The first involved the design of a photovoltaic solar station that provided electrical power for a remote outdoor sports complex building. The photovoltaic system also offered "real-world" experience for students in its electrical construction and maintenance technology program.

The second project was a solar thermal installation that provides supplemental heating for the greenhouse used by the college's Landscape Horticulture program.

In addition, many schools that build additional surface parking areas or parking ramps are considering solar options to provide energy and heat to the structures. Another way to integrate solar energy is by using it in athletic wellness facilities that are used year-round by students as well as the general public. Given the high domestic hot-water requirement, providing a solar heating system may make sense.

The right application

Green technology continues to evolve, and new applications are being introduced continually. The good news is that the energy efficiency of solar panels is trending upward, and the overall cost is trending downward. It is advisable to model different manufacturers' products under varying conditions to find the best fit. In choosing panels, there are several options to consider including solar thermal, photovoltaic or a combination of the two.

A good solar thermal panel can achieve more than 50 percent thermal efficiency. Solar thermal collectors are classified by the USA Energy Information Administration as low-, medium- or high-temperature collectors. Low-temperature collectors are flat plates generally used to heat swimming pools. Medium-temperature collectors also usually are flat plates, but are used for heating water or air for residential and commercial use. High-temperature collectors concentrate sunlight using mirrors or lenses and are generally used by utility companies for electric power production. Types include:

  • Flat plate. Photovoltaic plates convert solar radiation directly into electrical power utilizing a variety of semiconductor technology. A good photovoltaic panel can achieve more than 20 percent efficiency. The majority of solar thermal applications use flat plate design. These were the type used for the District Energy project and commonly are used for domestic water heating applications.

  • Vacuum tube. These types of thermal panels have a higher efficiency performance but are more expensive. They also are more beneficial in higher-temperature applications.

Kelley is education group manager and FIEDLER, PE, is a senior registered engineer for TKDA, a St. Paul-based firm that provides communities, public agencies and businesses with engineering, architecture and planning services. The firm worked on the District Energy St. Paul project and the Dakota County Technical College project. Kelley can be reached at [email protected]. (651)292-4428

Related video about TKDA:

Sidebar: Solar checklist

Issues to consider when determining whether a campus is a viable candidate for a solar heating system:

  • How centralized is the campus heating and domestic hot-water system? Integration of solar heating with a centralized system has a lower installation cost.

  • What are the year-round heating and domestic hot-water needs? Being able to take advantage of solar energy throughout the year makes for a better return on a school's investment.

  • Does the campus have remote buildings that require heat or electricity? Solar heating or electricity may be an option in lieu of extending utilities long distances.

  • Does the school have space either on existing rooftops or on land that offers a place to install solar panels? A significant footprint area is needed for solar panels and should be considered when conducting long- or short-term planning.

  • What is the existing source of heating energy? An honest evaluation of solar energy should be compared with the existing use of natural or propane gas, fuel oil, electric or other methods.

  • Is the campus planning to convert from steam heating systems to hot-water heating? If schools are considering the switch, it may be a good time to integrate solar options.

  • Is the solar project part of a new building construction project or retrofitting an existing facility? The cost of retrofitting the solar system to an existing facility typically will be more expensive than installing it as part of a new facility.

  • Does the campus emphasize green initiatives? This is of increasing importance to today's students and faculty when choosing schools.

  • Does the school offer programs that teach alternative energy design or the operation and maintenance of alternative energy systems? The installation of a solar heating system can provide for a "hands on" experience.

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