The Army Reserves used its Bryan Army Reserve Center in Bryan, Texas, as a test bed for a geothermal heat pump, solar water heating and a photovoltaic (PV) solar array. The goal was to implement Presidential Executive Order 13423 to reduce energy intensity by three percent annually and implement renewable energy generation projects on Army Reserve property, according to a case study by Colonel Stewart Fearon.
Eighty-three wells were drilled 300-feet deep to feed 37-heat-pump system. The closed loop geothermal system is 90 tons at a cost of $333,000.
Eighty of the wells support the 41,500-sq-foot main training/administrative building, and the remaining three wells support the 7,644-sq-foot base maintenance activity shop.
In Texas, comparatively little energy is expended on heating the building so cooling was the primary driver for the geothermal HVAC system, which completely replaced the old chiller unit. Compared to a typical chiller unit, the initial cost and annual maintenance of the geothermal heat pump were more expensive, but over a 30-year expected life cycle, the energy savings make the geothermal system less expensive. In addition, the heat pump system requires less maintenance than the previous HVAC system.
The ground temperature in Bryan remains relatively constant year round at about 68 degrees Fahrenheit. The heat pump uses the 300-foot deep wells to extract heat from the ground in the cooler months and distribute it through the conventional duct system to warm the center. In the warmer months the process is reversed and the heat is extracted from the building and transferred back into the 83 wells. Two pumps located in the mechanical room circulate a Glycol solution through a closed system.
The Bryan Army Reserve Center project also makes use of solar water heaters. Instead of heating the water from about 68 degrees Fahrenheit to 125 degrees Fahrenheit with gas or electricity, the solar water heaters use the solar panels on the roof to heat the water.
The PV array at Bryan covers 14,220 square feet and is made up of 682 (77”x30”) solar panels for an initial cost of $1.48 million. Each panel is capable of generating 280 watts and has a maximum power of 190.9 kW, but the inverters can only capture 175 kW.