“Net-zero energy” is the new “LEED-certified” when it comes to environmental boasting rights for commercial-building developers. With on-site energy production a key element in earning certification as a building that produces as much energy as it uses, designers are looking beyond simple, roof-mounted photovoltaic (PV) panels to new ways of incorporating electricity-generating equipment into buildings. Such “building-integrated” products could represent the next evolution in high-performance design and tie electrical contractors even more closely to building-design teams.
Challenge and opportunity
This spring saw two major milestones in efforts to rein in the impact of human activity on the global climate. In mid-May, carbon dioxide (CO2) levels hit a record 400 parts per million (ppm) at the Mauna Loa Observatory in Hawaii, which is considered the primary benchmark site for CO2 measurement. Scientists believe the planet hasn’t seen this level in the last 2 million to 10 million years, i.e., millions of years before humans evolved. Two million years ago in the Pleistocene Era, forests grew in Northern Greenland, and sea levels were between 30 feet and 60 feet higher than today, said National Oceanic and Atmospheric Administration senior scientist Pieter Tans in a press release.
A month before this ominous announcement, however, another development offered some hope of humankind’s capacity for reducing its CO2 output, when a Seattle structure billing itself the “world’s greenest office building” opened its doors to tenants. Among its significant features are PV panels rated to generate more than 230,000 kilowatt-hours (kWh), enough to power the building and its occupants’ activities. Faced with the need to build 575 panels into their plans, architects at Seattle’s Miller Hull Partnership engineered a cantilevered canopy that provides both shading and signature-building panache. Here, PV panels aren’t hidden behind a rooftop canopy; they are, at least partially, the roof itself.
This is, in essence, the definition of building-integrated renewable energy, in which energy generation is placed into the design of a structure, not treated as a value-added option. And, as the efforts of groups like Architecture 2030 (which seeks to make all buildings carbon-neutral by 2030) are gaining favor among architects and owners, manufacturers are beginning to respond with new dual-function products.
Building-products giant Saint-Gobain entered into the residential solar market several years ago, originally with standard roof-mounted panels through its CertainTeed subsidiary. However, the company saw opportunity in a more truly building-integrated approach and launched its Apollo II solar shingles just this February. The product is mounted directly to the roof deck, like standard asphalt shingles, with flashing similar to that used with skylights, to allow the solar units to remain in place if the surrounding roofing needs to be replaced.
“It’s been tremendously well received,” said Mike Bottoms, CertainTeed’s Eastern United States solar PV sales manager. “We’re getting a lot of interest in the roof-integrated product; homeowners seem to gravitate to the aesthetics.”
The 54-watt modules are sold in kits that include all appropriate wiring and inverter equipment, and they weigh only 12 pounds, about the same weight, per square foot, as standard asphalt shingling. Initial orders are made through CertainTeed-certified roofing contractors, who send measurement data to the company’s solar-engineering staff. This group creates the line drawings and site plans needed by local building officials, along with a detailed proposal for the homeowner, outlining potential payback periods based on estimated solar exposure and local utility rates.
While roofers might be the initial sales contact, the shingles could offer significant business opportunities for electrical contractors. Roofers can link the individual shingles together, but electrical pros take over the installation once wiring penetrates the roof deck (through a single point of entry).
“We’re strongly recommending [roofing contractors] establish a relationship with an experienced electrical contractor for the installation,” Bottoms said.
Interestingly, this system’s inverter is designed to connect to the customer’s side of the breaker, not the utility side, as is often the case. This means electricity from the system is, in fact, directly supplying the home’s electrical needs, with excess power fed through the meter to the local utility’s distribution grid. This arrangement differs from more common designs, in which the inverter directly connects to the meter, with the rooftop panels serving more as a distributed generation resource for the utility than as an immediate resource for the homeowner.
CertainTeed’s shingles are made of monocrystalline silicon, the most common material used to manufacture the kind of PV panels usually seen on ground-mounted and rooftop installations. However, until a year or so ago, most observers expected thin-film PV products to take the lead in building-integrated applications. These offerings are manufactured by depositing PV material onto a flexible backing, such as rolled stainless steel. Beginning four or five years ago, a number of membrane roofing-makers began offering thin-film PV as an upgrade to commercial building customers. But this technology was particularly hard hit by low-cost Chinese competition—in fact, the Chinese companies underpriced their products so significantly that a number of them have ended up going out of business.
Pradeep Haldar is chief operating and technology officer for the U.S. Photovoltaic Manufacturing Consortium (USPVMC), a group that’s hoping to turn around thin-film’s fortunes in the United States. He sees the recent collapse of a number of thin-film fabricators as a natural step in the market’s evolution.
“Basically, the solar industry is going through a typical growth and collapse cycle,” he said.
The USPVMC is headquartered at the State University of New York’s College of Nanoscale Science and Engineering in Albany, N.Y. Working closely with the National Renewable Energy Laboratory, its researchers are focused on a specific kind of thin-film material—copper indium gallium selenide (CIGS)—that it sees as particularly promising for building-integrated photovoltaic (BIPV) applications; it has formed a working group to explore BIPV opportunities.
“The big market opportunity for PV is in distributed [energy]. That’s the ideal use for PV,” Haldar said. “And where does that happen? That happens mostly in buildings.”
One of the biggest thin-film players to fail in the recent shakeout was Uni-Solar, which led the market in partnerships with commercial membrane roofing companies. Haldar said the CIGS technology USPVMC is advancing and has potential to be both less expensive and more efficient than Uni-Solar’s nanocrystalline silicon material.
“That’s where some of the technologies we’re pursuing are starting to come online, and the roofing guys are really interested,” he said, noting how today’s CIGS products are approaching the efficiency levels of crystalline-silicon panels and that their manufacturing costs will fall in line as production quantities rise. “When you can get thin-film to scale, the cost can get to be a lot lower.”
Regardless of efficiency improvements and cost reductions, solar power still faces the challenge of intermittency. Even during the sunniest days, panel output can shift as quickly as it takes a cloud to pass in front of the sun. With both utility-scale and rooftop projects becoming more prevalent, utilities are beginning to see the potential for distribution-system voltage problems.
“Solar can change 80 percent of its profile in a few minutes,” said Doug Staker, business development director at Demand Energy, an energy storage manufacturer based in Liberty Lake, Wash. “That is problematic. It changes some of the schemes you have for voltage regulation and voltage protection. We’re starting to reach a limit.”
Batteries are often the first thing that come to mind when one mentions energy storage, but Demand Energy is focused on the software that controls how those batteries store and discharge energy. With this capability tied to smart-grid networks, utilities can start calling on customer-sited batteries with just seconds of notice for the added power needed to balance out periodic voltage drops. Additionally, Demand’s Joule.System can help building owners take some or all of their facility’s loads offline during peak pricing periods.
With advantages for both customers and electric utilities, storage will only become more important to building-integrated energy plans—at least, that’s how Demand Energy sees it.
“What I like about storage is there is no singular answer; all this stuff fits together,” said Erick Petersen, the company’s sales and marketing vice president. “Storage is smart, and when you put storage at the very end of the grid, you get the most benefit. We’re at the forefront at this next big stage of the industry.”