Concentration of CO2 in the Atmosphere

Designing Solar for High Density Areas

The Solar Settlement with the Sun Ship in the background: two PlusEnergy projects in Freiburg, Germany. Photo:

The Solar Settlement with the Sun Ship in the background: two PlusEnergy projects in Freiburg,
Germany. Photo:

By Steven Winter Associates staff

Hear the term “solar energy” and you’re likely to think of vast fields of glistening panels and hillsides transformed into disco balls. Hear the term “solar energy” and you might picture suburban McMansions with roofs that reflect the sky. Hear the term “solar energy” and you envision… skyscrapers? Affordable housing units? Clusters of panels lurking in the crevices of a city skyline?

By 2050, solar energy is projected to be the world’s largest source of electricity, and it would hardly be reasonable to do so by means of blanketing entire stretches of usable or natural lands with sheets of silicon. Instead, part of the solution lies in the use of high density solar, which is quickly becoming the backbone of the solar boom, providing access to, and availability of, solar energy in densely populated areas.

At the end of 2015, twenty U.S. cities accounted for six percent of the country’s solar photovoltaic (PV) capacity. This is particularly impressive, given that these cities combined account for merely 0.1% of U.S. land area. According to “Shining Cities 2016,” Environment America’s report regarding the status of solar power in United States, sixty-four of America’s cities have installed over 1,700 MW of cumulative solar PV capacity – almost as much as the entire country had installed by the end of 2010.(1)

How are these cities doing it?

Though the addition of solar PV usually offsets only the common area loads of a large building, not tenant loads, it is an attractive solution for infrastructure upgrades that are inherently more difficult to install in areas of high density. Distributed energy resources, such as solar PV, help defer upgrades to the distribution grid by supplying electricity closer to the load. Thus, even while additional energy sources are often required, many newly constructed and renovated city buildings are opting for solar power.

In addition to its practical advantages, the success of solar PV in America’s cities is due to both the improvement of the energy’s economies and the availability of state and federal incentives for solar investors.

First, system costs across all sectors are rapidly decreasing due to technological advances in modules and growing demand. This has resulted in a lower wholesale price for units and panels, making PV more practical not only individuals, but also municipal and public facilities. For example, in Las Vegas, 37 public buildings have reached a solar capacity of 6.2 MW. This includes fire stations, community centers, and parks, as well as a 3.3 MW generating station at the city’s wastewater treatment plant.(2) Tampa, Raleigh, New York City, and Atlanta are also at the forefront of incorporating solar power in their respective government and public facilities.

In addition to the reduced costs and increased supply of solar PV, demand is being bolstered by the availability of incentives. The Federal Investment Tax Credit offers up to a 30% rebate for installation costs through 2019, and continues the offer at regularly diminishing levels through 2022.(3) Local, state, and federal programs across the country offer similar rebates, tax credits, and tax deductions that not only improve the affordability of solar installation, but also drastically shorten the payback period.

So, as the market for solar continues to improve – and access becomes more widespread – how can the design and construction industries promote the continued installation of urban solar?

The most immediate solution would be to update state and local building codes to require solar-ready roofs and incorporate other sustainable best practices. For instance, Cambridge, MA requires all new construction or existing building rehab projects over 25,000 SF to meet at least LEED© Certified or LEED Silver standards – for which solar is a popular contributing factor.

Additionally, while state and federal incentives are widely available now, they are slated to decline over the next five to 10 years. Local incentives will then become the key that emboldens building owners and residents to take part in community solar efforts. “Solarize” campaigns are locally organized community outreach efforts that leverage group purchasing power to encourage homes and businesses to go solar over an established period of time. Solarize NYC, one of the largest and most successful campaigns of its type, is aimed at energizing citizens to take personal responsibility in the city’s goal to reduce greenhouse gas emissions 80% by 2050.

As U.S. citizens and local governments take the reins in the country’s commitment to a clean energy future, solutions such as high density solar are important industry advancements that provide more accessible and widespread opportunity for change.

Steven Winter Associates, Inc. provides energy, sustainability and accessibility consulting as well as certification, research & development and compliance services. Learn more at




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