According to one estimate, the amount of solar energy that falls on Earth in one hour is more than all the energy used on Earth in an entire year. As the technological and financial barriers to harvest that solar energy diminish, attention turns to barriers that happen closer to home.

What permits does a homeowner need to install solar? How much land does it take to build an array of solar panels big enough to power 100 homes? What incentives exist for companies to install solar in Philadelphia?

This past spring, the City of Philadelphia was named a Solar America City through a partnership with the U.S. Department of Energy (DOE).  The DOE has partnered with a select group of cities across the country that have committed to accelerating the adoption of solar energy technologies at the local level and Philadelphia is on board.

With Mayor Nutter's new Office of Sustainability, Philadelphia is committed to playing a more active role in energy management and to reducing our vulnerability to a future of rising energy prices. Solar will play a key part in that sustainable future.

Solar energy can help safely, reliably, and cost-effectively displace the use of energy generated by fossil fuels. The city's "Solar City Partnership" (the name of Philadelphia's Solar America Cities partnership) will focus on bringing together a group of stakeholders with varying perspectives, a broad knowledge base, and experience who are in the position to identify and remove barriers to solar development in the city.

Kristin Sullivan will lead these efforts as the Program Director for the Solar City partnership. Kristin joins the Office of Sustainability from the Wind and Solar Energy development industry, where she worked on early stage renewable energy development projects. She has been in involved in energy consulting and management since 2000, after serving as a Peace Corps Volunteer in Honduras.

The Solar City Partnership will develop a plan to help Philadelphia generate 2.3 MW of solar electricity by 2011 and 57.8 MW by 2021 within city boundaries, the city's proportional share of the Commonwealth of Pennsylvania's solar installation goal. We are on track to meet that 2011 goal, but the 2021 goal represents a big lift. The city intends to add a large commercial-scale solar installation to its ongoing smaller scale efforts in order to achieve its goals.

Philadelphia will work to develop and adopt a solar implementation plan that is replicable and fully integrated with updated citywide plans and institutional processes for guiding decisions on land use, economic development and infrastructure investment.

The city plans to identify and implement cost-effective tools to overcome commercial and residential solar market barriers in Philadelphia and its partnering communities.  "We also want to initiate planning for solar energy installations that can cost-effectively achieve the city's goals. This includes choosing technologies, targeting districts and sites, and creating financial structures that will support the installations," said Sullivan, the director of the partnership. (She can be reached by email here.)

The Solar City Partnership is just the most recent of our efforts to expand our capacity to build a sustainable future. One key element of that capacity-building is our focus on partnerships with non-profit advocates, public regulators and funders, and private industry. Together, we'll make Philadelphia the greenest city and region in the U.S. by 2015.

Mark Alan Hughes is a senior adviser to Mayor Nutter and the City's first Director of Sustainability.