Vineyard's $4.3 million photovoltaic power-generation system saved by two-inch clamp
By Rob Haddock
The vineyards of Rodney Strong Wines in Sonoma County are perfectly situated to harvest the sun: The rows of fruit are terraced to minimize the amount of shadow one vine might cast upon another at anytime throughout the day. Growing heavy and sweet, the resulting grapes produce award-winning wines, all thanks to the sun.
Wiring the winery's power system to the same sun that produces Strong's amazing fruit was an obvious move - especially with $2.1 million in incentives being handed out by the California Public Utilities Commission.
Each morning, the 100,000 square feet of roofing atop the barrel-aging warehouses takes the sun full on. As visitors arrive lights go on in the tasting rooms and glittering gift shops. Cash registers and electronic payment systems whir and air-conditioners hum while the winery's large refrigeration units operate around the clock.
In 2003 a system was designed to occupy half of the barrel-aging warehouses' roof space; 4,032 photovoltaic modules were purchased, each one capable of producing 190 watts of power. It was the largest photovoltaic (PV) project Berkeley, CA-based PowerLight Corp. had ever undertaken for a standing seam metal roof. The gauntlet had been raised.
Standing seam metal is the most durable roofing material currently produced. The question was how to attach the crystalline PV modules so that they would stay firmly in place throughout the 40-year life of the roofs without actually drilling through the roofs.
PowerLight found the answer in a novel clamping technology from Colorado-based S-5!. S-5! clamps get their strength and durability through two patented set screws, both inserted on the same side of the clamp. The rounded point of the set screws dimple the metal seam of the roof ever so slightly in order to increase purchase and retain the clamp in position. They do not, however, puncture the seam material, damage the roof, alter the roof's overall appearance, or, most importantly, affect its warranty.
Designed by a roofing contractor who grew tired of products that were difficult to install or performed poorly over time, the S-5! lineup of clamps are unrivaled in both ease of installation and longevity of hold. They're ingenious and uncomplicated; just what the Strong project needed.
S-5! customized a U-series clamp for the Galvalume steel roofs of the winery's barrel-aging warehouses. The unique clamp-and-set screw pairing was applied to over 10,000 attachment points without a single incident of penetration or damage to the roofs. The securely installed PV power system now provides around 30 percent of the vineyard's power requirements, including that demanded by the winery's significant refrigeration needs.
The number of designers and consultants in the field of alternative power generation who recommend standing seam metal roofing for PV systems is increasing quickly. The products make a logical pair: Crystalline modules have an average life expectancy of 40 years, and no roofing material choice except for standing seam metal can match that kind of longevity. Even sheet-membrane roofing - often considered the second-best option - requires replacement before the useable life of the PV expires.
Another benefit is weight: The combination of metal roofing and crystalline PV is less than 3.5 pounds net total per square foot of roof area. Such a low weight number liberates designers tremendously as they consider the supporting structure.
Finally, and by no means insignificantly, standing seam metal roofing is highly reflective and must transfer heat. Adding crystalline PV to such a roof could mean unprecedented cooling. In the case of Rodney Strong Vineyards, the PV modules will save the winery big bucks in cooling costs each summer. By installing the modules several inches above the surface of the roof, the array casts a shadow over the metal panels while creating an air plenum. According to a recent study at Oak Ridge National Laboratory in Oak Ridge, TN, this PV module shading effect and the movement of air through the plenum can reduce the temperature of a metal roof by as much as 65 degrees Fahrenheit.
The Rodney Strong project was a learning experience for everyone involved. Planning began in April 2003, with careful consideration given to initial costs, state and federal rebates, power production levels, investment payback estimates, and construction logistics. In September the winery and PowerLight agreed on a plan; once the designs were finalized, the concrete equipment pads were poured and the solar modules and supporting materials were delivered to the site. Installation was completed in less than 5 weeks.
Total cost of the system was $4.3 million, which was partially offset by the $2.1 million in incentives from the California Public Utilities Commission. Federal tax credits and accelerated depreciation make the cost-to-benefit ratio even better. PV power generating systems of this type are both environmentally and economically sound, and, thanks to products such as the S-5! clamp, long-lasting and increasingly easy to install. And that is something worth toasting over.