Energy & Water Conservation

SOLAR-HEATED POOL WATER

The water temperature in the pool is kept at a constant 81 degrees. Fifty solar panels on the roof of the Sports & Recreation Center help offset the cost of keeping the pool water warm.

In this entirely automatic system, temperature sensors in the pool water circulation system monitor the water temperature. As the temperature of the water falls below or rises above the 81 degrees set point, process control valves for chilled or heat exchanger water modulate to maintain the temperature set point. The solar panels heat a closed circuit of piping filled with water and propylene glycol, which connects to the heat exchanger. When the sun shines, the water mixture in the solar panel system piping is heated and flows continuously through the heat exchanger. During non-sunny or nighttime periods the heat exchanger is maintained through steam generation from the campus power house or natural gas.

The solar panels consist of long-lasting and lightweight fiberglass used for the frames of the solar collectors. Of equal importance is the special safety glass, required for stability, and the selective coating for optimum energy yields. These high-performance collectors are hermetically sealed, filled with an inert gas to reduce heat loss and use an innovative double meander tube design for greater heat transfer capability.

The sun provides the fuel of the future—solar energy, shining on us, providing heat, light, and energy. When the sun is shining, the solar system provides 100% of the pool water heating. On average, the solar panel system provides 42% of the annual pool water heating; the campus’s central steam plant provides 33% of the annual heating, and natural gas boilers in the Sports & Recreation Center provide 25% of the annual pool water heating.

RAINWATER HARVESTING

As a large consumer of potable water, evaporative cooling water systems including cooling towers are an obvious target for water conservation efforts. A system was developed to collect rainwater to address this. Drains were installed on the roof and around the perimeter of the Sports & Recreation Center, where rainwater is collected and directed to two cisterns buried beneath the Quadrangle. Approximately 0.62 gallons of water can be recovered per inch of rain per square foot of collection surface. For a 40,000 square foot roof, this translates to almost 25,000 gallons of water per inch of rain. These cisterns store 50,000 gallons of rainwater that will be used as makeup water for the cooling tower.

Once collected, this rainwater is filtered and sent to the building, where pumps located on the second floor send the water to the roof to replenish cooling tower makeup water. Meters are installed on the pumps so we know how much rainwater has been used. This make-up water is most beneficial during the hot summer months when the cooling towers are running constantly and generate the highest demand for energy and make-up water. With this system in place, the campus is avoiding the consumption of over 850,000 gallons of fresh water each year.

 
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