Solar windows
Illustration: Michael Kirkham Solar windows: Glass windows covered with an electricity-generating coating remain transparent, resulting in the world’s smallest functional solar cells (1 square millimeter for a single cell). They measure less than one-fourth the size of a grain of rice. Currently, the coating is able to produce a solar conversion efficiency close to 1 percent, but researchers are hoping that it will reach efficiencies above 5 percent when fully optimized.

It probably comes as no surprise that solar power is currently the least-used energy source in the United States. It has had a lot of catching up to do. According to the Green Building Alliance, solar technology powers only 1 percent of the nation’s total energy consumption. But thanks in part to subsidies like the Solar Investment Tax Credit, solar power’s star is on the rise, and government data estimate that solar harvesting across the U.S. has experienced an average growth rate of more than 50 percent per year in the last decade.

As solar technology continues to become more efficient and more affordable, architects and other professionals are beginning to think more holistically about how solar technology can be incorporated into the design process from the beginning.

“Oftentimes solar panels might be tacked on as an afterthought after the building has already been designed, and that’s pretty unattractive, generally,” says Anthony Denzer, a professor of civil and architectural engineering at the University of Wyoming and a member of the university’s Building Energy Research Group (UW BERG).

Denzer and his colleague Jon Gardzelewski, AIA, believe that solar power might be more widely implemented by architects in both residential and commercial buildings if it were not only more affordable but also more aesthetically appealing. To that end, they’ve created an “architectural taxonomy” for incorporating solar technology into the building design phase.

“If we’re going to boil down our conclusions to a really trite sentence or two, it would be that architects can think about solar panels as a building material, rather than a piece of equipment that’s just thrown on the roof,” Denzer says. The taxonomy includes concepts like planar composition, in the style of Ludwig Mies van der Rohe’s Barcelona Pavilion, to better accommodate panels; another concept is to adapt a building’s shape to the path of the sun. Even if a client isn’t planning on installing solar from the get-go, the taxonomy can help building owners to incorporate solar panels more aesthetically in the future.

A large part of the choice to incorporate solar power into a building’s energy usage for many clients, of course, comes down to money: what they can afford to implement and what the projected payoff will be. The cost of solar panels is at an all-time low, but there’s plenty of room for innovation when it comes to making the installation costs more practical and affordable, and therefore more accessible.

“The panels themselves have really fallen in price the last five years or so—the labor has not,” says Gardzelewski. Currently, a solar panel costs about $0.50 to $0.75 per watt, making a 5-kilowatt-hour system—a standard array for a single-family home—cost anywhere from $2,500 to $37,500 for the panels alone. In terms of return on investment, a 2010 analysis from Brookhaven National Laboratory found that the energy payback time (EPBT) of one solar panel is about six months, a figure that has most likely fallen as prices continue to decrease. Installation costs are more variable and, of course, consist of more than just the panels themselves. A fully functioning photovoltaic system involves at least four components—and the know-how to put them all together.

Thin-film solar
Illustration: Michael Kirkham Thin-film solar: Developed in the late 2010s, can be produced in a roll, and at about $1 a watt, it’s cheaper than the heavy, bulky crystalline panels that have been an industry standard for decades

“When the cost of LED lightbulbs came down, people could just buy them and screw in a lightbulb,” says Denzer. But even though the panels have decreased in cost, their installation “hasn’t yet become do-it-yourself.”

The installation price tag can be mitigated if the process is rolled into the construction process. In the case of a custom home for a private client overlooking Roaring Fork Valley in Aspen, Colo., local firm Cottle Carr Yaw Architects (CCY) incorporated a 7.5-kilowatthour solar array as part of the client’s larger sustainability goals for the structure. According to the house’s owner, the solar array, combined with a geothermal loop field and more passive strategies for controlling the amount of sunlight the house receives, allows the structure to produce about 70 percent of the energy it consumes.

“There are very few of our residential projects right now, in Aspen or Pitkin County [where Aspen is located], which don’t have solar arrays,” says CCY’s Todd Kennedy, AIA, noting that many of the residences in the region are occupied only seasonally. “A solar array can continue to produce [and store] energy, even when they’re not occupied,” Kennedy says. “So in a lot of partially occupied structures, it’s a pretty good strategy.”

Another recurring theme in how solar power is increasingly being incorporated into design is a sense of social and environmental responsibility—a perspective available to only a relatively privileged few—rather than an overarching concern for the bottom line. This ethos is prevalent in the homes in and around Aspen designed by CCY as well as larger-scale structures like the 62,000-square-foot home of the American Geophysical Union (AGU) in Washington, D.C. This circa-1994 building is currently being renovated by Hickok Cole Architects—with the goal of transforming it into a net-zero structure, one of only a few dozen in the country—by the spring of 2018.

“The AGU wants to be a catalyst for showing others the way,” says Yolanda Cole, FAIA, senior principal at Hickok Cole. “They wanted to be targeting net-zero energy, so that other people will do it, too.”

Tesla solar roof tile
Illustration: Michael Kirkham Tesla solar roof tile: Tesla has spent years developing roof tiles with built-in solar panels, and full-scale production started in early 2018. According to the company, the roof tiles will cost $21.85 per square foot. Standard asphalt shingles can cost anywhere from $12 to $40 per square foot.

Since the largest concentrations of net-zero buildings currently exist in sun-drenched states like California and Florida, achieving net-zero status for an urban building located in a historic district in a temperate area of the United States has posed its own unique set of challenges. A 693-panel photovoltaic array on top of the five-story building remains invisible from the street, satisfying the requirements of the surrounding historic Dupont Circle neighborhood. In addition, 24 panels are mounted vertically on the south façade at the roof so, ideally, the building will produce more energy than it consumes.

“The building was operating at about 63.7 EUI [energy use intensity, or the energy use per square foot of a building],” says Roger Frechette III, managing principal of Interface Engineering. “We needed to reduce that significantly to be able to get to that net-zero condition.” When the building is completed, in the spring of 2018, Frechette’s goal is to have it produce 13 EUI with the use of solar while consuming 11 or 12.4 EUI, thereby making it an even rarer thing: a net-positive building that gives energy back to the grid.

One potentially industry-changing innovation on the horizon is Tesla’s solar roof, which could—Tesla hopes—make solar a feasible option for every homeowner at some point in the future. The Tesla system uses custom solar roof tiles to generate power for a given structure and, in combination with the proprietary Powerwall battery, is poised to be a way to think about solar power as an integral part of a structure, rather than a premium add-on. However, the technology is still too new and pricey to make it a pragmatic choice for most consumers.

“People all across the board are very excited about the solar roof, and about the battery—it gives you more control, and it’s a smarter system,” says UW BERG’s Denzer. “The only disadvantage I’m seeing is that we don’t have a lot of examples yet. People are in this holding pattern for the technology to mature.” Consumers who might otherwise be installing standard solar arrays are holding out for the Tesla technology to become more accessible.

Gardzelewski likens the recent advances in solar technology, such as the Tesla Powerwall, to owning a luxury car before there were paved roads. “At some point, the technology and infrastructure aligned,” he says. “I think we’re at that place where the technology and infrastructure are slightly mismatched.”