Presentations on Photovoltaics, Hurricane Research, Testing and Protocols Featured at Fall Meeting
September 2, 2010Building Integrated Photovoltaics (BIPV) Could Enable Zero Energy Buildings
Brendan Dillon of Pythagoras Solar reviewed the benefits and development status of BIPV, broadly defined as photovoltaic solar devices that replace conventional building material to improve the energy efficiency of the construction while generating electricity and providing an aesthetically appealing appearance.
Driving potential BIPV acceptance are economic, environmental, community-related and regulatory factors. Economically, BIPV units would replace (not add to) currently-used building materials while leveraging current construction techniques and qualify for incentives such as the current 30% tax credit and an accelerated depreciation allowance. The nature of distributed energy production enabled by BIPV, which makes more efficient use of the built environment, contributes to environmental goals. BIPV also works to help meet “zero net energy” building goals and LEED requirements with less community impact than centralized power (even solar) plants.
While current BIPV products have their drawbacks in terms of cost/payback, low power generating density (in watts/sq.ft.) and U-value/SHGC performance, the technology is rapidly developing. New insulating photovoltaic glass units (PVGU) can outperform earlier versions by 50% to as much as 300% in terms of power density with better solar heat gain and comparable U-value performance.
Clearing all three hurdles for BIPV – energy efficiency (effective use of daylighting while reducing solar gain and acting as an efficient thermal barrier), electric power generation density (up to four times higher than current BIPV systems) and architectural appeal (adaptable design and a variety of colors) – is a tall order, but the future of PIBV is bright. The zero-energy building is just around the corner.
Development of the IBHS Natural Hazards Laboratory
Dr. Timothy Reinhold, Ph.D., PE (Colorado), Sr. VP for Research and Chief Engineer for the Institute for Business and Home Safety (IBHS), began by noting “lessons learned” about building design from recent hurricanes, notably:
- Structures were built without adequate plans and without the advice or supervision of qualified designers
- Millions of dollars are spent on construction, but very little on ensuring adequate design or inspection
Reinhold noted that Hurricane Andrew in 1992 provided the needed impetus for researchers to begin in earnest to develop ways to accurately reproduce hurricane winds and wind effects and evaluate as-built systems at full scale to avoid scaling issues.
Recognizing that the conventional boundary layer wind tunnel approach would not work due to the lack of active control needed to simulate gusts, IBHS took up the effort to build a full-scale multi-peril applied research testing and training facility. Known as the Safety Research Center, the insurance industry-sponsored facility is nearing completion at a site in Chester County, South Carolina, about 45 minutes south of the Charlotte airport. It will focus on catastrophe-related issues, including the natural hazards of wind, fire, wind-driven water intrusion and hail.
The center will be able to conduct full-scale testing of full-sized, 2,000 square foot, one- and two-story homes, light commercial construction and agricultural buildings to a variety of hazards, including realistic Category 3 hurricanes, wind-blown fire (mimicking wildfire embers) and hailstorms. It will also enable physical testing of individual structural components and building systems. The houses will be installed on a turntable so that as the house rotates, the effects of the wind in all directions can be studied.
To determine the actual wind characteristics that needed to be simulated, the project relied on Dr. Forrest Masters’ (University of Florida) work and data gleaned from portable weather stations placed in the paths of hurricanes bound for landfall, as well as instruments installed in certain houses as part of the Florida Coastal Monitoring Program.
The resulting IBHS Natural Hazards Lab will feature a 145’W x 145’L x 70’H test chamber with a movie-screen size (65’W x 30’H) wind inlet, and the ability to introduce variable droplet-sized rain at rates up to eight inches per hour, as well as realistic hailstones and hailstorms. Firebrand generation is also being developed as a means to simulate wind-driven wildfires. High-speed, high-definition cameras and TV lighting will record results.
The initial research focus of the facility will concentrate on roofs, although the test building mock-ups will have windows and doors, offering an opportunity for fenestration research and testing in cooperation with AAMA.
Rounding of AAMA 520-09 Test Data Can Introduce Misleading Results
Experience is showing that measurement protocols detailed in AAMA 520-09, Voluntary Specification for Rating the Severe Wind-Driven Rain Resistance of Windows, Doors and Unit Skylights, can lead to mistaken conclusions. This is traceable to detailed descriptions on rounding of measured and calculated values for the amount of water penetration obtained per ASTM E2268-04 tests (Standard Test Method for Water Penetration of Exterior Windows, Skylights, and Doors by Rapid Pulsed Air Pressure Difference). The procedure can cause a unit, which should pass the test, to be interpreted as having failed or vice-versa.
The current procedure instructs the laboratory to weigh collected water that penetrates the innermost plane of the product or which passes through the product’s mainframe or overflows the sill to the nearest gram and converts to the nearest equivalent whole milliliter or measure the volume directly to the nearest whole milliliter. The rounding involved in arriving at the nearest gram or nearest whole milliliter is the source of the problem.
The Southeast Region Technical Committee recommended changes to fix this problem are to reword section 7.2.3 of AAMA 520 to simply instruct the laboratory to measure the water volume and compare it to the calculated allowable volume vs. measuring and converting the weight of the collected water.
It was also recommended that the definition of “water penetration” be clarified for Section 8.5 to specify that it refers to any water that penetrates the innermost plane of the product or which passes through the product’s mainframe or overflows the sill during the 300-cycle test period.
AAMA 506-08 to be Updated
To address language in ASTM E 1996-09 requiring products containing a given glass type to be tested, the AAMA 506 Impact Task Group will be re-assembled to edit AAMA 506-08, Voluntary Specifications for Impact and Cycle Testing of Fenestration Products, to coincide. AAMA 506 currently allows glass substitution. Meanwhile, an ASTM ad hoc workgroup is investigating the performance of tempered glass vs. annealed glass in the off lite of an insulating glass unit (IGU).
Also related to glass, there is some news from the ASTM E1300 Task Group. Research indicates that the strength factors of heat strengthened and tempered glass may be overly conservative. Perhaps the factors will increase in the not so distant future?
Copies of these presentations are available in the Members Only section of the AAMA website under Member Tools>Event Minutes and Presentations.
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