Earlier this year, the Trump administration imposed a significant tariff on imported solar panels. The tariff caused a major stir in the industry. Opinions vary over the impact the move will have on the market. Some suggest it will boost domestic solar manufacturing while others point to the cancellation or stalling of multibillion-dollar installations as a major blow to renewable energy.Despite the fact that installation growth is projected to remain flat through 2018 as the industry adjusts to the tariff, solar continues to be a very bright spot on the renewable energy horizon, according to the Solar Energy Industries Association (SEIA), Washington, D.C. Solar has experienced an annual growth rate of 59 percent during the past decade and accounted for 30 percent of all new electric capacity in the past three years, SEIA reports. Additionally, prices have dropped 52 percent during the past five years though declines slowed somewhat in 2017. Further, SEIA notes the rapid rise of community solar has boosted the non-residential segment in recent years, coupled with increasing numbers of offsite and rooftop corporate procurement by such companies as Amazon, Apple, Target and Walmart.
But wide-scale adoption and integration of photovoltaics (PV) in the commercial buildings segment remains somewhat of a challenge. “Five years ago, the building industry wasn’t even really thinking about solar,” says Christopher Klinga, P.E., technical director of the Architectural Solar Association (ASA), Boulder, Colo., and owner of engineering design company SolMotive Design, Boulder. “It was just kind of a pain […] to them, and it wasn’t integrated into their supply chain at all. It was just happening elsewhere in the solar industry.”
Klinga notes while solar panels are easy to install on rooftops and on ground mounts, the building envelope itself remains largely untapped—and building integration with PV represents a tremendous opportunity for the commercial market.
“We believe that the only way for solar to get integrated into the envelope or into architecture in any way, the building industry really needs to have buy-in,” Klinga explains. Although the concept of building-integrated photovoltaic (BIPV) isn’t new, the term can be confusing because it doesn’t necessarily mean total integration into the envelope itself, which can be a problem if there’s a panel failure, Klinga says. Rather, BIPV can be used as an overhead glass canopy, standalone architectural structures, window awnings, rainscreens, balustrades or even flooring. As such, he prefers the term “architectural solar” to BIPV and believes there’s a larger market opportunity when people better understand what BIPV means and its potential applications.
Challenges to Building Integration
While opportunities for building integration abound, so do the challenges, which range from site orientation and storage to codes and permitting, as well as aesthetics. But none are insurmountable and, with thoughtful planning, they can be effectively addressed.
Perhaps the most obvious hurdle to implementing solar is the fact that the sun simply doesn’t shine all the time and, as such, storage is a major factor in successfully implementing the technology. Taylor Harvey, Ph.D., co-director, NSF I/UCRC on Next Generation Photovoltaics, Texas A&M University, Central Texas, Killeen, says: “There’s a lot of advantages that could be gained if you were able to build a larger system to provide both your power but also dump some of the energy into batteries and be able to use that at nighttime or for smoothing purposes. I think that’s a big thing.” [Note: Smoothing is required because renewable energy is intermittent.]
Robert C. Tenent, Ph.D., senior scientist at the National Renewable Energy Laboratory (NREL), Golden, Colo., says while higher-performance next-generation solar materials are available, silicon-based panels still dominate the commercial building market because they are the least expensive—but also the most difficult to integrate. “One, there’s the roof space issue that certainly presents a problem,” he says, which can effectively be addressed offsite with community solar programs. But in terms of the building itself, Tenent says silicon panels tend to be problematic.
“Silicon panels can have a good bit of dependence on basically how they’re oriented toward the sun with how they perform,” he explains. “Some technologies can allow you to put things into a non-optimal orientation and still be OK, but silicon is one that’s got some problems with that.” For example, if they are installed on a vertical surface or one that is predisposed to shading, “you end up losing a lot of performance pretty quick with some of those baseline technologies,” Tenent observes.
“Permitting is still, in my view, a big issue,” Harvey adds. “In the U.S., every single municipality has a slightly different permitting process and slightly different paperwork, so it makes it so that you have to have a local expert to get through the permitting—and that costs additional money.” In Germany, on the other hand, Harvey points out solar permitting involves a two-page applica- tion that is consistent across the entire country. [Note: SEIA and non-profit solar advocacy group The Solar Foundation, Washington, are working with cities and counties in the U.S. to streamline permitting processes and reduce local barriers to going solar.]
Likewise, building codes reference solar panels and modules differently than they do for glass, which can make building integration—even on non-structural applications—difficult. Klinga suggests the codes need to pull these two references together so that the building side addresses structural panels and the electrical side of the code deals with instances when solar is fully integrated. “It doesn’t do that quite yet,” he observes.
However, he says there are standards in development that are BIPV-focused, and “what they’re doing is, they’re connecting the standards that are specific to solar and standards that are specific to the building industry and providing a way of looking at BIPV and understanding which standards should apply rather than writing a whole new standard, which I think is a good approach.”
Finally, with typical silicon solar panels, the ugly truth is they are not very attractive—and that can be a turn-off to architects and building owners. “That’s a real concern, the aesthetics of the actual panels,” Tenent says. “If we could make them look better, more people would put them on their buildings, and that is really difficult to do with silicon because silicon in a lot of ways is not a great solar material even though we use it so much.”
PHOTOS: courtesy of Architectural Solar Association member Lumos Solar
Simple Strategies for Solar
Nevertheless, there are relatively easy and cost-effective ways building owners and facility managers can retrofit their existing buildings with available solar technology. Klinga suggests there is ample opportunity to utilize BIPV with overhead-glass applications because it doesn’t delve as deeply into structural issues.“I think that’s kind of the low-hanging fruit of architectural solar because it’s not enclosing the envelope,” he says. When solar is integrated into the structure, the complexity increases because warranties come into the picture. If the solar modules fail, for example, they are much more difficult to remove or repair, Klinga says. “So, overhead solar offers a far less risky opportunity to create architectural solutions that people can interact with, and there’s still a great benefit to them.”
Harvey suggests, “Anybody who has a lot of roof space, there’s a lot of configurations that can easily be installed on rooftops at this point for a really reasonable cost.” He adds the caveat that the most important factor with implementing solar panels today is to find a reputable installer.
On the Horizon: Next Gen Technology
Although complete integration of solar solutions into the building envelope is still a ways off, emerging technologies are opening the door to tremendous possibilities, starting at the window.
“There’s currently a handful of technologies that are coming out that lend themselves to the laminated glass fabrication process; that’s super interesting,” Klinga says. “It’s a big change in the industry, and I think once that stumbling block gets broken down, the others will follow. That’s kind of the linchpin of the problem right now,” he says.
The benefit of integrating solar at the window is that it covers much more surface area than on the roof, especially in multi-story commercial buildings. However, a major obstacle with integrating solar into the vertical surface is the tradeoff between capturing as much sunlight as possible while allowing enough sunlight to see through it, according to Tenent. “Most of the solar energy is in that visible light spectrum you can see with your eyes, but you also want to harvest that, so people will either play in the infrared or the UV space to try and harvest energy from there, but you end up leaving a lot of the energy on the table when you do that,” he explains.
NREL is working with a number of early-stage companies to further develop PV technology into windows that have higher conversion efficiency and are more tolerant of the sun-angle issue. Among them are perovskite solar cells, an emerging thin-film PV class of material that reacts
to different wavelengths of light, which lets them convert more of the sunlight that reaches them into electricity. Another promising technology gaining in popularity is cadmium telluride (CdTe) solar cells, a thin-film technology with active layers that are just a few microns thick, or about one-tenth the diameter of a human hair. CdTe represents the largest segment of commercial thin-film module production worldwide, and recent improvements have matched the efficiency of multicrystalline silicon while maintaining cost leadership, according to NREL.
Among the more interesting concepts in solar technology development is the work that Harvey completed during his graduate studies and with the company he subsequently launched, called Lucelo Technologies, creating low-cost, flexible solar cells that can be applied using paint. These ultra-lightweight, flexible solar cells suspend light-absorbing nanocrystals
in paint (just like pigment in traditional paint) to turn virtually any surface into a solar collector. Although the technology is viable, Harvey says it still needs development. But paintable solar is an indication of where the industry may be headed in the future.
“We have to make some layering that’s pretty precise so [the technology is] not quite to where you can go to Home Depot and just buy a can and paint it on your wall, but that’s the idea—and eventually we’ll get there,” he says.
BENEFITS OF INSTALLING SOLAR
There are numerous paybacks that solar installations offer to existing facilities. As outlined in the Washington, D.C.-based U.S. Department of Energy’s Better Buildings report, “On-Site Commercial Solar PV Decision Guide,” the advantages to adding photovoltaic (PV) panels to a commercial building include:
FINANCIAL BENEFITS Solar PV can offset the costs of electricity and reduce monthly electric-bill costs through reduced energy and demand charges. In addition, a variety of federal, state and local incentive programs can reduce the initial cost. Finally, many third- party ownership models have been developed that increase the financial attractiveness of solar PV.
ENVIRONMENTAL BENEFITS Installing solar PV directly offsets purchases of grid- supplied electricity. The emissions offsets of doing so will vary depending on the location but will generally result in reduced carbon dioxide, nitrous oxide, sulfur oxide, and particu- late matter emissions from the combustion of fossil fuels in natural gas- and/or coal-fired power plants.
MARKETING BENEFITS Solar PV can help meet corporate sustainability targets and, for commercial buildings that lease floor space, the energy savings may be passed on through the lease price. Additionally, for schools and other educational buildings, solar PV can be used as an educational tool to teach students about solar energy and sustainability.
RELIABILITY If solar PV is part of a microgrid installed at a facility, it can help power the building during an outage or when disconnected from the grid.
COOLING-LOAD REDUCTION Adding solar PV to a roof will reduce a building’s cooling load. If solar PV is installed as a canopy, it can also provide shading. Both of these configurations reduce the urban heat island effect.
LEED CREDENTIALS Solar PV counts toward a number of credit categories within the LEED rating system.
PHOTOS: courtesy of Architectural Solar Association member Lumos Solar