Solar Energy Systems Oxford MS
Solar Energy Systems
Imagine buying a car and finding out that the only way you can get the upgraded engine you want is to have it bolted to the roof. That analogy is not too far off when it comes to residential solar electricity.
Many homeowners like the idea of offsetting their utility-generated power supply with renewable energy from the sun. Some are willing to tackle the various challenges, such as cost and design, for the benefits of solar electricity. But a lot of homeowners balk at the idea of hanging an array of metal-framed panels on the roof, especially on a new, custom-designed home.
Some manufacturers of solar energy systems have responded to those concerns by developing solar cells that are built right into shingles, slates or other roofing materials. Called building-integrated photovoltaics, or BIPVs, these new solar cells are designed to disguise the cells and overcome one major obstacle to the greater use of solar electricity - cumbersome technology.
The development of BIPV systems seems to be a new tack for solar technology. "The solar industry continues to think cost is the main issue" hindering widespread implementation of solar energy, says Gay Canough, owner of ETM Solar Works in Endicott, N.Y., an installer of both conventional and BIPV systems. Canough believes aesthetics is a growing consideration, and sees appearance overtaking cost as the leading factor in the decision to go solar.
It makes sense that when solar energy is specified in a new house, it should be an integrated part of the roof, rather than attached to the roof as an afterthought. Music enthusiasts used to add speakers to car doors and hang tape players from their dashboards. Today, mobile sound systems are built in. In a similar way, BIPV manufacturers are implementing new technology to appeal to consumers.
One innovative product, called Sunslates, mimics the look of a slate roof by using a fiber-cement shingle popular in Europe. The manufacturer, Atlantis Energy Systems of Sacramento, Calif. ( http://www.atlantisenergy.org ), glues conventional crystalline PV panels to the shingle surface. The shingles overlap, like on a typical slate roof. They are wired in strings of 24 and connected by a cable that runs into a junction box in the attic.
The slate-like shingles form a weather-tight roof that can withstand winds of up to 125 mph. They also have a tempered glass panel surface that sheds heavy snow.
A typical installation on a home in a location such as southern California would include 216 Sunslates and cover 300 square feet - roughly a 17-by-17-foot area. It would generate 3 kw - enough power to meet nearly three-quarters of a home's annual demand. The cost before any rebates or tax incentives is around $12 a watt, or $36,000 for a 3-kw system.
While most products are made to be noticed, Sunslates are designed to blend in. Many visitors to Doug Daniels' house in Sonora, Calif., don't even realize his roof is covered with Sunslates.
Daniels has 648 Sunslates on his south-facing roof, capable of generating nearly 8 kw. That's more than double the output of a typical home system. But what visitors see is a black slate roof.
"People drive into my yard, and I say, 'How do you like my solar roof?'" Daniels says. "They say, 'Where?'"
Daniels chose Sunslates because he wanted his home to be energy self-sufficient but was worried about leaks from panels mounted on his roof. He hasn't paid a power bill since 2002. And because his system generates more power than his home needs, he uses the excess to charge an all-electric battery-powered car made by Massachusetts-based Solectria Corp. He uses the car for short trips around the area.
"I'm the envy of everyone in town when I tell people I don't have an electric bill or buy gasoline," Daniels says.
Bragging rights come at a cost, however. Daniels' oversized system cost $87,000 - a price knocked down to $57,000 after government rebates and tax credits. Daniels figures the roof will pay for itself in 15 years or so. And when it comes time to sell, a house with no electric bill should net a premium price, he reasons.
He's probably right. Feedback from homeowners suggests that homes with Sunslates are easier to resell, according to Morrissey. And despite the fact that Sunslates cost 25 percent more than frame panels, Morrissey agrees with Canough of ETM Solar Works that the industry has underplayed the architectural appeal of BIPVs. "I don't think we've made a big enough deal of promoting that advantage," he says.
One caveat: Be sure to check the warranty period on any solar energy system you might install. Sunslates offers a 20-year warranty on its modules and a 25-year warranty on roof integrity (against decomposition or decay caused by the passage of water, for example), which is well within most payback periods. Also, remember that payback periods vary by location. A system in Seattle or Buffalo will receive only half as much sunshine as one in California or Arizona, and can take twice as long to pay back, so be sure to take that into account when purchasing a system.
Most of today's BIPV roof systems use the conventional crystalline cells common in frame solar panels. A less common approach is the one being taken by United Solar Ovonic of Auburn Hills, Mich. ( http://www.smartroofsolar.com ), which sells its products under the Uni-Solar name.
Uni-Solar uses a thin-film technology known as amorphous silicon, which forms a layer rather than a crystal structure. One Uni-Solar product looks like asphalt shingles and comes in 4-by-8-foot sheets. The shingles can be walked on without damage. They are watertight and rated to withstand wind loads below 80 mph. They can be nailed directly onto wood decking with a fire-resistant underlayment.
The company's other product is a laminate for steel roofs. The laminate, which has a peel-and-stick adhesive backing, is designed to be applied directly to 16-inch-wide (minimum) metal roofing. Suitable for both renovations and new construction, it is watertight and can withstand wind loads of 160 mph, so it's suitable for use in hurricane-prone regions.
The average cost for a 2-kw system - enough to meet roughly half an average home's electricity bill in southern California - is $20,000 before any government rebates or tax incentives, says Allan Gregg, Uni-Solar's director of system engineering and marketing. The market for the company's products is currently confined largely to southern California, he notes.
A Better Approach
Design and orientation are critical with all photovoltaics. A system that deviates too far from true south, is shaded by buildings or trees, or isn't tilted on an optimum angle will have diminished performance on an annual basis.
These factors are especially true with building-integrated systems that are retrofitted to existing homes. Unlike conventional framed panels, BIPV systems have little or no flexibility when it comes to angles and orientation. The roof faces the direction it faces - and so do any solar panels integrated into the roof. So while a few BIPV systems end up on existing roofs, the technology really is aimed at new construction - and that's enticing the world's major electric companies to enter the field.
"It's the next logical step," says Marc Cortez, director of marketing for Sharp's solar division in Huntington Beach, Calif.
Sharp will market its tiles predominately to homebuilders for new construction. The installed cost is roughly $8 a watt, or $24,000 for a 3-kw system in California.
The challenge now for Sharp and the other manufacturers is to convince the homebuilding industry that BIPV is a better approach to solar power.
"We're a long way away from being a commodity product," Cortez says, "but we're heading there."
Tux Turkel writes frequently about home energy and solar issues. He's based in Yarmouth, Maine.