Solar-thermal Systems When it comes to effective and environ-
ONGOING SERIES
This article is the fifth part in an ongoing series about the integrated metal roof retrofit assembly at Good- fellow Air Force Base, San Angelo, Texas. The first part appeared in retrofit’s September-October 2012 issue, page 30, and was an overview about the dem- onstration project. The second part was published in the November-December 2012 issue, page 34, and focused on the roof’s inte- grated solar-power system. The third part covered the standing-seam metal roof and appeared in the January-February issue, page 32. The fourth installment of the series appeared in March-April, page 30, and addressed the importance of insulation. A final article un- veiling the performance of the integrated roof system on Goodfellow AFB after one year of data is analyzed by Oak Ridge National Labo- ratory, Oak Ridge, Tenn., will appear later this year.
mentally friendly generation of heat, the technologies range from simple passive solar systems to geothermal systems using phase-change materials to more complex and high-efficiency concentrating solar sys- tems that use vacuum tubes and parabolic mirrors. Depending on the project scale, location and building type, solar-thermal production technologies can be mounted on the ground, attached to roofs and walls, or actually integrated into the building’s wall or roof assembly. The combined building envelope plus en-
ergy technology systems fall into a category defined by the Washington, D.C.-based U.S. Department of Energy as Building Integrat- ed Solar Technologies, or BIST systems. These systems collect the sun’s energy as heat and transfer that energy to the building’s space- and water-heating systems via heat exchangers using nontoxic fluids. The most environmentally friendly heat-transfer fluids being introduced to the market are water and nontoxic bio-glycol made from corn. Because BIST thermal systems are
integrated as part of the building envelope, they are protected from the sun’s damaging ultraviolet rays, making them long-lasting and durable. Being completely concealed by a roof or wall surface, they are architectur- ally integrated into the building design and practically hidden from view while remain- ing highly effective as a power source. Building envelopes with architectural integrity, long life and renewable energy have proven to be an attractive combination for the residential, commercial and military building industry, resulting in hundreds of thousands of square feet of installed systems since 2004. These systems have been rigorously evaluated during the years and have been independently tested by the
Florida Solar Energy Center, Cocoa, and certi- fied by the Solar Rating and Certification Corp., Cocoa, Fla. Now the military is taking a harder
look at the effectiveness of BIST systems. As part of a DoD Environmental Security Technology Certification Program (ESTCP) grant, Goodfellow AFB’s 17th Security Forces Squadron completed the installation of a building-integrated solar technology system in conjunction with a retrofitted metal roof. (To learn more about ESTCP, see the first ar- ticle of this series in the September-October 2012 issue, page 30.) This high-performance retrofit roofing system was implemented to demonstrate that fully commercialized building-integrated solar technology solu- tions can be readily and effectively deployed to upgrade the 2 billion square feet of DoD building inventory to 21st century energy- efficiency and power-generation standards. Prompted by the need for a roof replace-
ment, the retrofit system synergistically combines multiple “stacked” technologies to maximize efficiencies and power generation, all as one roof. The retrofit roofing project includes a new metal roof with integrated solar photovoltaic (PV) panels that are cooled by the building-integrated solar-thermal system (increasing PV electricity output while producing hot water), upgraded roof insulation, and a system to collect and reuse rainfall. The concealed solar-thermal system is one of several integrated systems being demonstrated at Goodfellow AFB. Perfor- mance will be determined relative to meet- ing federal efficiency goals, including Execu- tive Order 13423, EPAct 2005 and the Energy Independence and Security Act of 2007. Building-integrated solar technologies
must prove to be life-cycle cost-effective as the DoD will demand. Instead of being a bulky add-on, the integrated roof assembly results in a hardened building envelope
When considering ways in which to increase the energy efficiency of roofing, sub-purlin providers must accommodate energy- saving technologies.
42 RETROFIT // May-June 2013
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