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Making solar technology invisible

Matthew Charles and Bill Sepmeier
Vail, CO, Colorado

New solar power systems called “building integrated photovoltaic” are becoming the hottest technology in renewable energy design in the construction world for one reason: They either can’t be seen or blend in so well with the architecture they go unnoticed.

The most common material for the new system is a type of flexible plastic that is bonded to the top of common metal, or “standing seam,” roofs. In order to produce electricity, the plastic is impregnated with layers of an amorphous semiconductor that changes sunlight into electrical energy.

When used over multiple sections of standing seam, the entire south facing rooftop of a home becomes an efficient solar power station, without the presence of traditional glass-framed solar modules. DC power generated by the roof material is transformed into household AC current to power the home during the day. Any excess power is sold to the local electric grid though the local utility’s “net metering” program.

Some forward-thinking companies have products that take built-in renewable systems to the next level by incorporating both photovoltaics for electricity production and solar thermal for heating water into one complete package. Thermal collector pipes are installed on a building’s unfinished roof deck atop special insulation material. Metal standing seam roof is then laid on top of these heat collector pipes to finish the roof and completely hide the solar thermal system from view. Flexible plastic photovoltaic laminate is then bonded to the top of the standing seams to complete the hybrid system.

The systems complement each other because of the nature of how they operate. The solar panels need direct sunlight to produce electricity but are less efficient the warmer the ambient air becomes. Solar thermal also needs direct sunlight but can operate efficiently in a much wider range of ambient temperatures. Because it uses solar radiation to heat the liquid solution travelling through the heat collector pipes, the thermal system helps cool the roof as it continually transfers heat to the collector pipes. The cooler the roof stays, the more efficiently the panels will be able to produce electricity. It’s a win-win situation.

Due to modern advances in this technology, building integrated photovoltaics are not limited to standing seam roofs. Special shingles and roofing tiles, which look almost identical to their traditional counterparts, are quickly gaining popularity as an attractive addition to almost any style of roof. All the new technology available today has undergone extensive testing and carry 20-year-plus warranties.

But don’t rush off to buy a built-in renewable system until you know you have the right conditions these systems were designed for. Your home or office needs to have a good expanse of roof that faces somewhat south. Since true south and magnetic south are different, it can be tricky just assessing which direction your building faces.

The slope, or pitch, of your roof will also play a big role in determining the feasibility of the system. Both photovoltaic and solar thermal work best when installed on a surface that is sloped relative to area latitude ” around 40 degrees in the Vail Valley.

If your roof pitch is less than 40 degrees, the system output will suffer. A roof pitch that is at or steeper than 40 degrees will also help shed snow that tends to accumulate on more slightly sloped roofs. If your renewable energy system is covered in snow for five months of the year, you’re obviously not getting the most out of your investment.

If your roof doesn’t sound like it’s perfect, don’t worry. A roof that faces somewhat south and has a pitch of less than 40 degrees can work, it just might take a little effort to make sure your solar setup doesn’t hibernate underneath a foot of snow all winter.

Local solar energy consultants can easily calculate production capability during all four seasons given specific rooftop plans to help you determine the feasibility of any proposed system.

Building integrated renewable energy systems aren’t perfect for everyone, but can be viable for people with the right conditions who want to reduce home energy operating expenses without the visual impact sometimes associated with traditional solar energy collection.

Bill Sepmeier is the chief technical officer and Matthew Charles is a design and sales specialist for Grid Feeders, a renewable energy firm in Eagle-Vail. For more information, call 688-4347, or go to http://www.gridfeeders.com.


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