Designers are blending energy-producing systems into urban architecture to reduce the nation's dependence on the grid and produce clean, green power

Photovoltaic systems primarily powered off-grid and remote applications in the early days of the technology, but engineers, architects, and designers are now powering large-scale residential developments and commercial high-rises with energy from the sun.

In New York City, solar panels soak up the sun's energy on the western façade of Solaire, the nation's first green residential tower. The 30-story, $100 million building features 33kW of photovoltaic systems, energy-efficient lighting, and energy-saving appliances. Two systems are located on the south and west wall of the buildings' mechanical bulkhead, and custom German-manufactured solar panels are integrated into the building's glass curtain wall and clear glass entrance canopy.

“It's a high-profile building in the solar world,” says Anthony Pereira, president of Altpower, Inc., a New York City-based design/build specialty-contracting firm that focuses on renewable energy systems for urban areas. “Solar is not the cheapest product per square foot, so if you're going to put it on a building, why not have it work as your building's façade to bring down the cost?”

Solaire's photovoltaic system meets Battery Park City Authority's green building guidelines, which mandate that every new building built in Battery Park City must have at least 5% of its base building load served by renewable energy systems. Solaire is 30% more efficient than any other building constructed in Manhattan to date, Pereira says. During the construction project, the team had to purchase as many materials as possible from within a 500-mile radius of the jobsite, recycle building materials, and use paints and finishes with low volatile organic compounds. The contractors even installed photovoltaic panels on their jobsite trailers to save energy during the construction process.

The New York State Energy Research and Development Authority provided funding for the project, which began in June 2001 and was completed in December 2003. Solaire became the first building constructed in lower Manhattan since 9/11. Altpower is now working on several other renewable energy projects, including the design and construction of a zero energy skyscraper that will produce as much energy as it consumes. Slated to be the second tallest building in New York City, the structure will feature such distributed generation technologies as wind turbines, photovoltaics, and microturbines.

“We're trying to understand how to implement these types of systems on skyscrapers in congested urban areas,” Pereira says. “You're starting to see it on people's homes more and more in some parts of the country, but buildings are a whole other challenge.”

Building-Integrated Photovoltaics (BIPV), which is popular in Europe and Asia, is beginning to gain more awareness in the United States. Richard Schoen, executive vice president of BIPV for Solar Integrated Technologies, created the world's first architecturally integrated roof in 1978, according to NASA's Jet Propulsion Laboratory. He fused crystalline photovoltaics to a conventional batten and seam metal roof for ARCO Solar, and installed the roof on a model home in Phoenix two years later. Schoen, a professor emeritus at the University of California — Los Angeles, is now working for Solar Integrated Technologies, which has taken the concept he invented more than 25 years ago to create a new approach to an integrated roofing product for the commercial construction industry. By fusing a thin film photovoltaic technology called amorphous silicon directly to the roofing membrane, no racks or other support structures are required, and no wires or cables are visible on the roof after the installation is complete.

“Rather than being on the roof, the photovoltaic system is the roof,” Schoen says. “That way the customer gets a photovoltaic system and a new 20-year to 30-year roof at the same time. Eventually, walls and windows will have that same kind of treatment.”

Architects and engineers are now replacing basic construction materials, such as roofing and glass walls, with photovoltaic systems through BIPV. To teach college students about renewable energy and BIPV, Progressive AE, an architecture and engineering firm, designed a photovoltaic system for Aquinas College in Grand Rapids, Mich. To blend the system into the building's design, the solar module was adhered directly to standing seam roof panels.

“We designed the roofing structure to coordinate with the building's overall look,” says Don Nolte, PE, an electrical engineer for Progressive AE, a Grand Rapids, Mich.-based firm. “One of our goals was to make this installation not an add-on look but an integral part of the building that would just blend right in.”

Because the roof structure wasn't square and had an angle on one side, Nolte and the engineering team had to devise a way to calculate the proper number of panels and interconnections to make a balanced 3-phase system design. Progressive has since worked on some buildings that are certified by Leadership in Energy and Environmental Design (LEED), the U.S. Green Building Council's environmental performance rating system.

“Energy conservation is an issue that we have to address as responsible engineers,” Nolte says. “The LEED program has dovetailed into what we're already doing. It's kind of a natural occurrence for us to go in this direction.”

Today's photovoltaic market.

The push to design green has turned the photovoltaic market into a $4 billion global industry that grows an average of 20% to 25% a year. Richard King, team leader for photovoltaics research and development for the U.S. Department of Energy (DOE), says the U.S. photovoltaic industry currently generates about 120MW a year, but by 2020, the nation could produce a few gigawatts. By bringing down the cost of the technology, the photovoltaic market could follow its current growth pattern and double every two to three years. To fuel growth in the industry, the DOE launched its Million Solar Roofs Initiative to install solar energy systems on 1 million U.S. buildings by 2010.

“Photovoltaics could eventually become 10% of the new electricity generation going up in the country,” King says. “Since 1980 we've created an industry, and now it's up and running. The more electricity we can get from clean technologies, the better off we are.”

The photovoltaic market has also experienced a fundamental shift from a “mom-and-pop” business to a multi-billion dollar global industry. Large corporations are now trying to become more competitive by establishing “green teams” to look for ways to eliminate waste, conserve energy, and build energy-efficient buildings.

Several factors are driving the commercialization of photovoltaics — state rebates and incentives, the current cost of conventional electricity in large cities like New York City and Los Angeles, environmental building guidelines, concern over climate change, and net metering. About 36 states currently have net metering laws, which allow a consumer to run the electrical meter backward if the energy production exceeds the energy consumption.

Advancements in technology drive change.

The photovoltaic industry has experienced substantial growth in the last decade, but the prohibitive cost of solar cell manufacturing has slowed down the widespread adoption of the technology. To bring down the manufacturing cost, the DOE is researching new materials and technologies. Solar cells are made from the same semiconductor material as computer chips, and the solar panels feature semiconductor devices that convert sunlight directly into electricity. King estimates that 90% of the cells are made of crystalline silicon. To produce these panels, the solar manufacturing community must first grow the purified silicon, cut it into wafers, and then connect the cells back together, which is both energy- and labor-intensive, King says.

Solaicx, a manufacturer in Los Gatos, Calif., is helping to drive down the cost of solar cell manufacturing by designing and building the equipment and processes necessary for mass producing high conversion-efficiency silicon wafers. Wafers account for nearly half of the cost of a solar module, and by reducing the amount of silcon that is used, Solaicx's manufacturing process allows solar cell module manufacturers to lower the cost of solar modules by 70%. Semiconductor manufacturers typically use the same manufacturing equipment to produce wafers for Pentium computer chips and solar modules. However, the computer chips and solar cells have two completely different purposes. While a Pentium computer chip is a highly sophisticated device, the solar cell is essentially a low-level semiconductor. Rather than building units by the inch, Solaicx is manufacturing equipment specifically designed for the solar industry to produce square miles of materials.

“We're making silicon an efficient means of converting the abundant energy provided by the sun into electricity,” says John Sedgwick, co-founder of Solaicx.

Competing in the global market. Through research and development, U.S. manufacturers are working to bring down the cost of photovoltaic components and systems. The United States leads the world in research and development, but the nation trails behind other countries in terms of photovoltaic module production (Figure). While the United States hasn't increased its federal funding of photovoltaic programs, Europe and Japan invested more money into developing the technology.

“Even though America first invented and developed the photovoltaic technology for the last 40 years, now all of sudden we've fallen behind as it's really grown into a fast-growing new energy source,” Pereira says.

Germany installed the first BIPV façade back in 1991 and currently manufactures much of the specialized BIPV panels and equipment that is used in the United States. For example, most of the building-integrated panels used in the Solaire project were assembled in Germany. Because of the increased popularity of BIPV in the building industry, however, a factory recently opened its doors in New York in order to manufacture the specialized panels in the United States.

King says one reason why photovoltaics has grown so much more rapidly overseas than in the United States is because of the nation's relatively low cost of energy. For example, electricity in Japan costs nearly 25 cents/kWh, which is typically two to three times the cost of electricity in the United States. Another factor that is holding back the photovoltaic market is the lack of federal incentives and rebate programs. Back in the '70s, the United States gave tax credits for solar, but today, the incentives and rebates are determined on a state level. To help make photovoltaics more comparable to conventional sources of energy, the DOE is striving to bring down the cost of solar electricity from about 20 cents/kWh to 6 cents/kWh between 2010 and 2020.

“Right now coal, oil, and hydropower are so inexpensive,” King says. “It's really hard for 20- or 25-cent electricity, such as photovoltaics, to compete with a nickel or a dime electricity. We need to continue to do research and improve manufacturing to bring the cost down.”

Solar energy powered space satellites in the late '50s, but the technology is now moving into the mainstream. Electricians and engineers are designing and installing photovoltaic systems to generate clean, green electricity for residential, commercial, and industrial applications. Through rebates and incentives, environmental building guidelines, and an effort to design green, the construction industry is using the power from the sun to fuel the buildings of tomorrow.

Sidebar: What is Photovoltaics?

Photovoltaic cells convert sunlight directly into electricity. These cells are made of semiconductors, such as crystalline silicon or thin-film materials. The DC electricity produced by the photovoltaic system is either stored in batteries or sent to an inverter, where it's converted into AC electricity to power a home or business.

Sidebar: Net Metering States

Net metering allows for electric meters to run backward if an energy-producing system, such as a photovoltaic installation, produces more energy than a building can consume. The electric utilities operating in the 36 states (Map above) that approve of this practice must pay customers who feed power back into the utility's electric system the retail price the utility is charging for electricity. The states that haven't enacted net metering laws normally require the installation of a second meter to measure the electricity that flows back to the utility. The provider then typically purchases this power at a rate much lower than the retail rate they're charging their customers.

Sidebar: Training the Photovoltaic Workforce of Tomorrow

College students have raced solar-powered cars for a decade in the Department of Energy (DOE)-sponsored American Solar Challenge. The DOE is now sponsoring a sustainable building competition to teach future designers and installers how to apply this technology to houses. Teams of engineering and architecture students from 20 universities are designing and building completely self-sufficient solar-powered houses on their college campuses for the DOE Solar Decathlon.

“We need to get photovoltaics more mainstream in the housing sector,” King says. “We've been racing cars for a long time, but the cars aren't moving in the industry, so we thought, let's try to translate it to houses.”

Each school has about two years to build a solar-powered house, which ranges from 500 sq ft to 800 sq ft. In September 2005, all 20 houses will be moved to the National Mall in Washington, D.C., where judges will evaluate the homes based on their energy efficiency. Each home will feature such renewable energy technologies as photovoltaic systems, passive solar heating, daylighting, and energy-efficient appliances. The teams must not only design and build the solar-powered houses, but also live in them for a week to show how they can use the sun's energy to perform everyday tasks like doing laundry or washing dishes. To learn more about the Solar Decathlon, visit