The unique demonstration project at Goodfellow Air Force Base in San Angelo, Texas, will be the subject of a series of articles in retrofit. The individual component technolo- gies have been evaluated and used commercially for many years. However, the integration of the technologies as distinct components of an inte- grated metal roof retrofit assembly has never before been demonstrated.
During the next year, we will highlight the technolo- gies used on the roof, cul- minating in a final article showcasing the results of Oak Ridge, Tenn.-based Oak Ridge National Labo- ratory’s data acquisition system.
34 RETROFIT // September October 2012
a water/glycol mix heat-exchange medium was installed over the radiant barrier to optimize the heat transfer.
■ The thermal purlin used to position the solar thermal system tubing is configured to allow for above- sheathing ventilation (convective cooling) to take place from the eave to the ridge.
■ Panels of 24-gauge standing-seam metal roofing, prepainted with a polyvinylidene fluoride cool coating, were laminated with a thin-film PV system and then installed directly over the solar thermal system.
The holistic use of these integrated
components into one retrofit system is designed to maximize electricity genera- tion and minimize the cooling load of the building. In addition, the solar-thermal technology that is integrated into the retrofit cavity will optimize the energy gen- erated for domestic hot water and space heating. The project is expected to yield more
than 750,000 KBtu of energy per year through savings from energy-efficiency improvements to this building or har- vested energy generated from solar-power systems on the roof. With the local utility costs taken into account, Goodfellow Air Force Base is estimating a savings of $11,750 per year on this building thanks to the retrofit roof.
With the retrofitted integrated metal
roof system in place, the surface of the roof is now being used to capture rainwater in an above-ground cistern with a 10,000 gallon capacity. It is estimated that a typi- cal 2-inch rainfall in the San Angelo region will generate 6,500 gallons of rainwater being captured from one side of the roof. The rainwater will be used for irrigation purposes on the base. Estimates suggest 131,000 gallons of potable water per year will be saved from being used for irrigation.
The Data With the full installation and commission- ing now complete, the plan is to have ORNL continue monitoring data during the next 12 months. Data will be taken on: ■ temperatures ■ heat transfer ■ energy output from the photovoltaics ■ energy consumed by the building ■ water usage The ESTCP, DoD and project team are
confident this integrated retrofit roof system will perform as predicted and al- low for the technology to be transferred throughout DoD, as well as to other federal agencies and ultimately into the commer- cial building sector.