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GREEN SPOTLIGHT SHINES ON SOLAR ROOFING
publication date: Apr 28, 2008
By Kerry Lansing Advances in solar technology have also transformed roofing options. No longer a monolith mounted on top of a home, solar roofing options have expanded to include tiles, slates and shingles that serve as the roof itself. They can cover the entire roof or portions and blend seamlessly with the surrounding materials. Necessary electrical equipment is integrated into the building structure and hidden from outside view.
One of the companies responsible for these innovations is Atlantis Energy Systems, Inc. (AES). It manufactures Building Integrated Photovoltaic Systems (BIPV), which include Sunslates and MegaSlate as well as the solar glass laminate for Nu-lok. In addition, AES offers hybrid systems in which any of its sloped roofing products can be combined with Dawn Solar Systems (DSS) for a solar and solar thermal product. AES makes custom photovoltaic glass laminate as well as PV shingles. The solar glass can be made into skylights, roofs, atriums, and otherwise integrated into the structure of a building as an architectural element. Future House USA was designed by environmentalist George Bialecki and is based on his Home Biology 101 building method. Energy efficiency is a key component to this design. The house features a hybrid solar roofing system on its south side, which incorporates Sunslates and the Dawn Solar System to create a solar and solar thermal system. For more information on the project, visit www.futurehouseusa.org.
Sunslate shingles are attached to the roof with a counter batten system (pictured at right). A series of vertical 2x2 boards are nailed over the rafters and gridded by a series of horizontal 1x4 boards. The slates are then hung from hooks nailed to the horizontal boards. The system affords a two-inch space between the roof deck and slates, which allows for airflow underneath the tiles. The airflow helps keep the roof cool and increases performance. The cooler the roof is, the more power the cells produce.
The inverter can be connected to the house’s main panel and to the utility grid. Homeowners who want to be “off the grid” need a battery system to store excess power produced. The reserved energy is used at night and during periods of lower production. Homes can also remain connected to the local power grid and tap into it when necessary. Utility companies in 42 states and Washington, D.C., have programs to buy back the watts when a home produces more power than it needs. Using this net-metering program, some utility meters actually run backward during periods of high productively.
The goal of Sunslates is to create something that fits the architecture of the home, said Joe Morrissey, vice president of sales for Atlantic Energy Systems, Inc. For example, approximately 85 percent of American homes having charcoal-colored roofs. The basic Eternit slate is a variation of that color. The tempered glass section of the slate varies from blue to bluish-black. Sunslates work with any other type of roofing material, whether tile, shake, metal or asphalt (composite). According to SolSource, Inc, an installer of Sunslates, “A typical installation of 216 Sunslates (about 300 square feet) will cover from 60 to 80 percent of your power needs.” The cost of Sunslates is about $15 per watt installed. While standard solar panels run from about $8 to $11 per watt, Sunslates provide a roofing and power generation, said Morrissey. Federal incentives include a personal tax credit of up to 30 percent or $2000 for the purchase and installation of a residential solar electric and solar water heating property. This credit was established by the Energy Policy Act of 2005 and recently extended through Dec. 31, 2008. For more information, contact Public Information IRS (www.irs.gov). Many states also offer detailed information on incentives and grants. California, for example, has two such sites: Go Solar California (www.gosolarcalifornia.ca.gov) Local utility companies offer specific information on net metering and how to connect a PV system to the electrical grid. Comments
Copyright 2007, 2008 WPL Publishing Co., Inc.
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Solar roofing is a bright topic on the green building scene. Since its development in the early 1900s, solar (photovoltaic) power has offered a renewable, sustainable and socially responsible means for generating electricity. Yet, growing concern over global warming and the rapid depletion of fossil fuels has once again placed solar in the spotlight as an increasingly obvious and attractive energy source.
Increased product availability combined with programs that offset the cost of photovoltaic systems is making solar roofing more economically feasible for more people. Consideration should be given to the cost of local electricity, eligibility for federal tax rebates, and state and local incentives. These financial options are helping pave the way for solar to go from a green building option to a building standard.
The product combines a roofing slate, called Eternit, with a piece of tempered glass, comprised of six solar cells. Eternit originated in Switzerland and is used widely in Europe. Though the original design incorporated asbestos into the fiberboard product, the carcinogen is no longer used in the manufacturing process.
The shingles are wired together in strings of 24 (pictured at right). At the end of each string, a homerun cable is run through the roof deck to a junction box. A cable is then run from the junction box to an inverter, which converts the direct current (DC) power, generated by the solar cells, to alternating current (AC) power. AC power is the type of electricity supplied by utility companies for home use.
In northern latitudes, Sunslates should be positioned on south-facing roofs that are not shaded. Dummy slates are available for areas, around a chimney for example, that are shaded. These faux slates maintain the roof’s visual effect, such as a finished glass, edge-to-edge look, such as this home in Toronto (at right).
MegaSlates are frameless solar modules and appropriate for residential and commercial buildings. Because they are frameless, a MegaSlates roof provides a clean, glass, edge-to-edge look. MegaSlates can cover an entire roof or work together with other roofing materials (pictured at right). MegaSlates also work well with thermal solar collectors..jpg)
AES manufactures the glass for Nu-lok Solar Slates (pictured at right). Nu-lok has a patented fixing system that does not require the slates to overlap. Slates are mounted to the roof with a steel batten and clip system. The battens are connected with link channels, which are locked into place between the metal battens. Each link channel has a steel clip that holds the leading tile edge in place. The links act as channels between slates for moisture runoff. Nu-lok solar slates can be used for an entire roofing project or be incorporated into projects with more traditional materials, such as ceramic or natural slate. 
Hybrid systems combine any of AES’s sloped-roof systems and the Dawn Solar System. The solar and solar thermal systems work together. The solar tiles heat food-grade glycol (in tubing underneath the slates), which is pumped through heat transfer and distribution systems (pictured at right). This process heats water, which is then used for hot water and radiant and space heating. While the DSS heats water, it simultaneously cools the roof tiles, making them more effective. A cooler attic also keeps the house cooler in warm weather. And of course, the solar tiles generate electricity.