Sustainable Cities: Vision of Solar-Powered Skyscrapers Nearer Reality

As urbanization, and urban populations, continue to spread, finding ways to enhance the quality of urban life and make urban living socially, ecologically and economically more sustainable has become a critical issue in our times. Much attention is being focused on reducing waste and pollution and making buildings more energy, water and waste-efficient, as well as powering them with clean, renewable energy.

Lined with high-rise buildings and skyscrapers, designing economically viable distributed renewable energy systems for the densely-packed built environment of cities presents a stiff challenge for architects, builders, urban planners, and renewable energy technology and project developers.

At least a couple of innovative startups are making strides toward developing a product that could go a long way toward realizing this goal, however, by creating transparent organic solar photovoltaic (PV) films that can be applied to commercial glass plates.

Last week, 3p's Mary Mazzoni noted the progress being made by German solar company Heliatek, which unveiled a 40 percent transparent organic solar cell that’s ideal for generating energy from windows, façades and glass car roofs. There's at least one other entrant in the field. If remaining hurdles can be overcome, solar-glass developers at New Energy Technologies envision SolarWindow arrays being installed on and producing clean, renewable electricity for high-rise buildings, apartment and office towers in cities around the world.

Urbanization and energy consumption

The social, ecological and economic pressures from rapid industrialization came into sharp focus at the “Planet Under Pressure 2012” conference in London. With world population forecast to increase from 7 billion today to more than 9 billion by 2050, humanity’s urban footprint will take up 1.5 million more square kilometers of land by 2030 at current rates -- an area comparable to that of France, Germany and Spain combined, it was noted during the conference.

According to conference organizers:

"That translates into an average 1 million more city dwellers every week for the next 38 years, with the world’s total urban population forecast to increase from 3.5 billion today to 6.3 billion by 2050."

And when it comes to energy use, nearly 40 percent of total U.S. energy consumption in 2012 (about 40 quadrillion BTUs) came from residential and commercial buildings, according to the Department of Energy's Energy Information Administration (EIA).

Energy, moreover, is the single biggest operating expense for a commercial building, accounting for 30 percent of the typical office building's running costs, the Georgia Department of Natural Resources Pollution Prevention Assistance Division highlights in its “Sustainable Office Toolkit.”

Meeting the challenges of ongoing urbanization

Enabling all those buildings to generate their own electricity from clean, renewable energy sources would be a giant leap forward in terms of reducing urban pollution, resource use and waste -- and enhancing the health and quality of life for city residents the world over. It's still some ways away, but nearer to becoming physical reality then it's ever been.

New Energy Technologies has been working closely with the DOE's National Renewable Energy Laboratory (NREL) to develop see-through SolarWindow coatings capable of generating electricity on glass and flexible plastics. On March 26, the company released photos of the largest, high-performance SolarWindow arrays it has developed to date.

At more than 232 square centimeters, the latest SolarWindow arrays are more than 35 percent larger than any the company has fabricated before. In addition, they're produced with “highly-uniform, colored tints preferred by commercial window manufacturers for installation on skyscrapers worldwide,” New Energy Technologies highlights in a press release.

“Among the most important criteria for developing SolarWindow™ applications for today’s skyscrapers is providing a set of neutral colors that remain see-through and are uniform in fabrication,” John A. Conklin, New Energy Technologies' president and CEO was quoted as saying.

“Today, we’ve revealed a record-breaking, largest-area see-through, organic photovoltaic (OPV) SolarWindow™ array that addresses tall-tower and commercial building glass requirements, they also bear the promise of facile scale-up capabilities and unparalleled manufacturability.”

Self-sufficient skyscrapers

Energy conversion efficiencies of organic PV coatings are not nearly as high as they are for inorganic solar photovoltaic cells and modules made from silicon and cadmium-telluride; they make up for that in other ways. As New Energy Technologies' principal scientist Dr. Scott Hammond explained, “The unique properties of OPV allow for low-cost, high-volume manufacturing and provide many advantages over conventional, inorganic PV technologies for window applications."

For one, SolarWindow coatings could be applied to all four sides of a building, vastly increasing the surface area capable of producing electricity. In addition, New Energy's SolarWindow can produce electricity in diffuse and shaded sunlight, as well as from artificial lighting, including fluorescent, LED and incandescent lighting, conditions in which conventional PV systems suffer large efficiency losses or can't produce electricity at all.

Another advantage the organic PV SolarWindow has when compared to conventional solar PV cells and modules is its ease, and its low cost, of manufacturing. As New Energy explains, SolarWindows can be manufactured “using high-speed and high-volume systems such as roll-to-roll or large area sheet-to-sheet processes.”

Images courtesy of New Energy Technologies