Buildings that can make their own energy have long been a goal for environmentally motivated architects and engineers, but the means for doing so have mostly been limited to bulky solar panels and wind turbines high enough to raise the ire of almost any community’s zoning board. Now, however, a new generation of photovoltaic curtainwalls, shingles and other products are coming to market, bringing the goal of energy self-sufficiency just a little bit closer to reality. And new technology is allowing these and other generating options to power building systems, enabling true grid-independent operation.
New product efforts primarily are aimed at the solar market, turning the sun’s rays into electricity (although several building-mounted wind turbine designs have been introduced recently). In the past, solar equipment has been seen as a standalone investment, most often as panels bolted onto roofs or mounted on the ground. But a new generation of photovoltaic (PV) material is encouraging manufacturers to modify existing offerings, such as roofing shingles or curtainwalls, to include electricity generation as a value-added benefit. Such building-integrated applications are not as productive as dedicated panels, but their output can add up to make a dent in an owner’s monthly electricity bill.
This new material is based on organic thin-film technology, which enables less-expensive manufacturing and a more flexible product. In fact, some offerings are created using equipment resembling common printing presses, with PV coatings applied like ink on paper. As a trade-off, though, these new devices also are less efficient than standard silicon-based panels. They turn a smaller percentage of the sun’s energy into electricity. But efficiency ratings are improving rapidly, and manufacturers hope the multipurpose design will draw owners who see the benefit in incremental improvements that can add up to big savings.
That’s the goal of Arch Aluminum & Glass Co., a Tamarac, Fla.-based maker of curtainwall and storefronts. The manufacturer has teamed up with Konarka, which produces organic thin-film PV cells in sheets, using a building and equipment formerly owned by Polaroid, in New Bedford, Mass. Konarka’s products are beginning to show up in messenger bags that can be used to charge cell phones and patio umbrellas that generate enough electricity to power laptop computers. Arch is developing insulated window panels that sandwich in a sheet of Konarka’s PV material between two layers of standard glass to create windows that offer truly electrifying views.
The product, which Arch is calling Active Solar Glass, is still in prototype development and is expected to be offered in both window and spandrel versions (“spandrels” are the nontransparent portions of a glass curtainwall that cover a building’s structural elements). Other manufacturers have created transparent, glass-encased solar panels, for use in canopies and other applications where see-through capability isn’t as important. However, Arch representatives say this product will be almost invisible to building occupants.
Conductors run from each sheet, in parallel, traveling through channels in the curtainwall frame, with connectors that terminate at an interactive inverter. The inverter synchronizes the native direct current (DC) power into alternating current (AC) usable by building systems. The AC current enters the building distribution system through an National Electrical Code-mandated, dedicated circuit panel. It’s not anticipated that these systems will generate more electricity than building systems can consume, so reverse-metering arrangements aren’t part of the design.
An Active Solar spandrel panel has been installed at the company’s headquarters, and the manufacturer anticipates see-through “vision” glass pilot projects will be underway by later this year, with full-scale production launching early 2011. The prototype features a red tint (created by the solar sheeting, not an actual glass coating). Arch expects to offer green- and blue-tinted versions once the product reaches the market. Publicized only by a few Konarka press releases, Active Solar already is garnering design-community attention.
“The interest is strong,” said Max Perilstein, Arch’s marketing vice president. “We haven’t done any promotion on this product, and we get three to five people per day filling out the online form for more information.”
Perilstein said the product’s competition will come from other window makers who offer high-end ultraviolet coatings to minimize interior heat gain. Active Solar windows can’t match a roof panel’s electricity output, but their production could put them at an advantage when compared to other premium glass offerings, especially when federal and state incentives are applied. These windows offer the same heat-gain reduction, with an added benefit that can cut a facility’s operating expenses.
“Depending on the building site, the efficiency is never going to be as good as a roof panel,” said Manny Valladares, director of research and development with Arch. “We like to say that it enhances the energy efficiency of that glass at an incremental cost.”
Savvy electrical professionals will understand the opportunities these new on-site-generating options could provide for building their businesses. Solar windows and shingles might be attached to the building by roofers and curtainwall specialists, but the wiring and connections will require electrical expertise. However, these jobs may require contractors and electricians to crack open their DC textbooks because PV products generate DC power.
Typically, on-site DC power has to be converted to AC in an inefficient process that creates electricity that is usable by building systems or the larger grid. But manufacturers are seeing opportunities in this area, as well, developing new options for turning on-site power into an efficient on-site resource.
New equipment is coming onto the market to help integrate output from solar, wind and other distributed generation sources directly into building distribution systems, without the need for the efficiency-robbing AC conversion. This effort is being aided by new standards (such as those being developed by the EMerge Alliance) that provide guidance to electrical-system designers and manufacturers and give electrical utilities confidence that building--side innovations won’t affect grid safety or performance.
Detroit-based Nextek Power is a founding member of the EMerge Alliance and a manufacturer of equipment designed to provide a single entry point—called a “power server”—for grid-supplied AC and locally generated DC, without need for complicated safety designs. Most current PV and wind installations bypass building distribution systems and, instead, push electricity onto the grid, with owners receiving credit against their bills for their contributions. Such approaches raise utility concerns regarding “islanding”—a fear that these distributed resources will continue to feed the grid, even when line workers might think area transmission lines are dead. Nextek’s approach isolates on-site power resources, protecting utility workers and enabling systems to operate uninterrupted in an outage.
“You avoid the conversion loss from DC to AC, and from AC to DC,” said Paul Savage, Nextek’s CEO. “And the broader electrical system isn’t obliged to carry that power or to worry about the consequences of distributed generation.”
Under the Nextek plan, utility-supplied AC power and on-site-generated DC power enter the building through the power server. A storage battery also may be connected to the unit, providing some carryover when on-site resources aren’t available. Higher voltage DC power from the server can be distributed to floor-level transformers, where it can be stepped down to a lower voltage to power electronically driven lighting, controls and sensors and variable-frequency motors, eliminating the need for individual, device-level transformers. AC power is distributed through standard means to serve other building needs.
“We like to think of our power server as a point of connectivity at the building site,” Savage said. “The architecture of the whole thing allows the system to be more efficient on AC and dramatically more efficient on DC.”
Improved DC efficiency is important because of the multiplying number of electronic devices now controlling our buildings. In some facilities, such as data centers, even minimal device-level improvements can create a cascade of savings, because more efficient equipment generates less waste heat. Ongoing cooling costs are the biggest line item in a data center’s operating budget, so reducing air conditioning expenses can have an immediate bottom-line impact.
Such an every-little-bit-helps argument works well with today’s environmentally conscious architects and engineers, who are looking at buildings holistically, rather than as collections of isolated systems. In such designs, building-integrated photovoltaics (BIPV) aren’t called on to carry the entire energy load. Instead, these products are among a number of components—along with building-siting practices that enable daylighting while minimizing cooling requirements, advanced insulation that reduces heating needs, and control systems that ensure building systems only operate when needed—that work together to create extremely efficient structures.
This is the approach advocated by the founder of Architecture 2030, a Santa Fe, N.M.-based organization promoting the reduction of fossil-fuel use and related greenhouse gas emissions in building construction and operation. The group’s ambitious goal is carbon neutrality in new building construction and major building renovations by 2030.
“We say there are three ways to get there,” said Ed Mazria, AIA, the group’s founder and president. “First is through design, either from where you locate the building, to whether you use daylighting or a light-colored roof. Second is technology, either from high-efficiency equipment to solar-thermal and photovoltaics or a campus-wide energy system.”
The final component to Mazria’s plan is ensuring the remaining electricity needs are met through the local utility’s renewable-energy purchase plan.
The architect, who sees a carbon tax as an inevitable future expense for building owners, sees a design bonus in products, such as the new thin-film offerings, that can serve dual purposes at an incremental cost over standard-issue components.
“One advantage these products have is a great deal of flexibility. You begin to make up the difference [in efficiency] that way,” he said. “If it becomes a technology that can be easily integrated and built, then it has a bright future.”
ROSS is a freelance writer located in Brewster, Mass. He can be reached at firstname.lastname@example.org.