Heating and cooling with the sun

April 21, 2010

By Drs. Robert & Sonia Vogl
President and Vice President
Illinois Renewable Energy Association

The 4,000-square-foot Freedom Field headquarters in a Rock River Water Reclamation District building is both heated and cooled by the sun. Dave Martindale, president of Ballard Engineering, explained the workings of the system. Cooler water flows past the tips of five banks of Sundra evacuated solar tubes on the roof where it is heated, then to a 1,225-gallon indoor storage tank. A supplemental boiler will occasionally cut in if the water temperature falls to 100 degrees Fahrenheit. If the temperature rises to 200 degrees Fahrenheit, excess heat will be dumped into non-potable water via a heat exchanger.

In winter, radiant floor heating is used to maintain comfort. Hot water runs through PEX tubing looped in a serpentine pattern on a pegged insulated grid foam floor. The floor is covered with concrete, paint, decorative random inlaid chips and a clear, hard finish. Two heating zones—one near the outer wall and the second in the center of the room and near the inner wall—are controlled by local temperature sensors. Automatic settings are adjustable and have proven to maintain 71 degrees Fahrenheit and 40 percent humidity.

In summer, the heated water is used for air conditioning. The process takes place in an almost complete vacuum within an absorption chiller. A lithium bromide solution is the refrigerant. This solution is ebulliently pumped through a heat exchanger for preheating, which separates a portion of the water from the lithium bromide. This then leaves behind concentrated lithium bromide solution, which is cooled by a heat exchanger. The water vapor condenses, then with both the water and concentrated lithium bromide solution cooled via the heat exchangers, recombine in extreme vacuum, creating the cooling effect. The sun’s energy creates needed heat, so no fuel is burned. In summary, with 200-degree water and a cooling tower operating at 85 degrees, the absorption process can create 45-degree water that is then used for air conditioning. This total solar-driven unit is one of four in operation in the U.S.

The sanitary district is interested in partnering with Freedom Field on its projects. They anticipate that by producing their own power, customer rates will be kept low. Martindale praised them for being a good neighbor. Other renewable energy projects will include using sludge biomass, algae studies, biogas to energy, wind energy, regenerative fuel cells and geothermal studies.

Martindale explained that since Freedom Field wanted data about weather, solar input and production to analyze the performance of renewable energy applications, the system is highly instrumented and monitored. A tremendous amount of data is being collected and is updated every five minutes. The real-time operational data is on the Freedom Field Web site, www.freedomfieldenergy.com, under the “projects” tab. Martindale feels the project will provide a useful training center for students in engineering studies and that assembling the data into something useful would be an excellent graduate student project.

A fully operational weather station sits on the highest roof. This real-time data is also being logged and is on the same public Web site mentioned above. Photovoltaic panels will be installed near it to produce 12.5 kW of electricity, enough to power the entire system. Heat, air conditioning and electricity will be provided simultaneously for Freedom Field.

Drs. Robert and Sonia Vogl are founders and officers of the Illinois Renewable Energy Association (IREA) and coordinate the annual Renewable Energy and Sustainable Lifestyle Fair. The Vogls and the IREA are members of the Environmental Hall of Fame. Dr. Robert Vogl is vice president of Freedom Field, and Dr. Sonia Vogl is a member of Freedom Field’s Executive Committee. The Vogls consult on energy efficiency, renewable energy and green building. They have 3.2 kW of PV and a 1 kW wind generator at their home. Forty acres of their 180-acre home farm are in ecological restorations. They are active in preserving natural areas and are retired professors from Northern Illinois University. E-mail sonia@essex1.com.

From the April 21-27, 2010 issue

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