Florida gets its first zero-net-energy campus

Abuilding complex in Anna Maria City, Fla. will be the state's first zero net energy campus when completed in 2012. Developers plan to make the five LEED-Platinum buildings in the plot generate more energy than they consume.

The Florida buildings incorporate energy saving features that include geothermal cooling and heating, 100 kW of photovoltaic panels to generate electricity on-site, solar thermal panels to produce hot water for a café in the complex, and cisterns to capture rainwater that irrigates plants and flushes toilets. Appliances, of course, are either Energy Star or WaterSense-certified, and the buildings themselves are recycled: They are historic structures. Some have even been moved from a different location. Building refurbishments use recycled materials, low-emitting paints, sealants and solvents, and a range of other sustainable design choices and materials.

The installation includes a three-unit, four-ton geothermal HVAC system from FHP Manufacturing that uses a ground water loop to provide heating and cooling. HVAC contractor Symbiont Service Corp. says geothermal heat pumps will eventually do all cooling for the freezers and refrigerators in the café, as well as for the display cases and ice machines. A plate heat exchanger transfers heat from the geothermal wells while simultaneously isolating well water from the HVAC loop water. Once heat is extracted from the water, the water is re-injected into the ground through a discharge well.

The 7.5-hp source pump which circulates water from the geothermal well is powered by a variable-frequency drive from Yaskawa America. The VFD adjusts the pump speed by controlling the frequency of the electrical power it supplies to the motor, throttling back motor speed to as low as 30% of capacity during times of lower cooling demand. Symbiont says running the VFD at 80% of capacity yields about a 50% energy savings over simply running the motor at rated speed.