In a major victory for the DC solar market earlier this afternoon, the Council of the District of Columbia unanimously voted in favor ofThe Distributed Generation Amendment Act of 2011. This bill is expected to be signed by the mayor within the next 10 days, and its passage will significantly improve the market for DC Solar Renewable Energy Credits (SRECs) and solar energy generally. The legislation will amend the District of Columbia’s Renewable Energy Portfolio Act to significantly increase the demand for solar energy and ensure the RPS benefits the residents of the District.
The Distributed Generation Amendment Act of 2011 is expected to create over 1500 new green jobs and direct around a billion dollars in investment into the District of Columbia over the next 10 years. This investment stream will generate revenue opportunities for the city and mitigate up to 53,000 tons of carbon dioxide, making for a cleaner, safer, and healthier Washington, DC. Perhaps most importantly, this legislation will facilitate innovative business models that will allow District residents and businesses of all economic backgrounds to adopt solar energy that will provide them with reduced energy bills over the next 30 years.
The legislation comes at a time when the substantial decrease in SREC prices coupled with the exhaustion of the DC Renewable Energy Grant program appeared potentially fatal to a previously booming DC solar market. Energy suppliers (who are mandated by the RPS to procure a certain percentage of solar electricity or pay an alternative compliance fee) could easily fill their quota for solar electricity by purchasing SRECs from systems in states outside the District. This oversupply drove down prices, which led to DC solar businesses and potential customers losing faith in SRECs, one of the key financing tools for a solar system (Income from SRECs typically covers 20 to 40% of a solar system’s cost).
The passage of the Distributed Generation Amendment Act will catalyze the DC solar market. Starting in 2011, the solar requirement for energy suppliers in DC will increase annually to higher percentages than the original RPS. Furthermore, energy suppliers will no longer be able to purchase out of state SRECS to meet their demand. With solar module prices continuing to drop, the passage of this amendment puts DC in a great position to take advantage of one of the fastest growing industries in the country. Solar energy businesses in the District can rely on SRECs for financing, which will lead to significant employment opportunities, stimulate direct commercial investments in the city, and raise the profile of Washington, DC as a leader in green industry.
"This is a huge victory for DC and the solar industry at large," notes Yuri Horwitz, CEO of Sol Systems, a solar finance company based in the District. "This legislation is a direct result of the hard work and dedication of the local solar community working in concert with District’s City Council to craft a piece of legislation that is both realistic and game changing. We have all seized the future."
Solar cells convert sunlight directly into electricity. Solar cells are often used to power calculators and watches. They are made of semiconducting materials similar to those used in computer chips. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is called the photovoltaic (PV) effect.
Solar cells are typically combined into modules that hold about 40 cells; a number of these modules are mounted in PV arrays that can measure up to several meters on a side. These flat-plate PV arrays can be mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight over the course of a day. Several connected PV arrays can provide enough power for a household; for large electric utility or industrial applications, hundreds of arrays can be interconnected to form a single, large PV system.
Solar shingles are installed on a rooftop. Credit: Stellar Sun Shop
Thin film solar cells use layers of semiconductor materials only a few micrometers thick. Thin film technology has made it possible for solar cells to now double as rooftop shingles, roof tiles, building facades, or the glazing for skylights or atria. The solar cell version of items such as shingles offer the same protection and durability as ordinary asphalt shingles.
Some solar cells are designed to operate with concentrated sunlight. These cells are built into concentrating collectors that use a lens to focus the sunlight onto the cells. This approach has both advantages and disadvantages compared with flat-plate PV arrays. The main idea is to use very little of the expensive semiconducting PV material while collecting as much sunlight as possible. But because the lenses must be pointed at the sun, the use of concentrating collectors is limited to the sunniest parts of the country. Some concentrating collectors are designed to be mounted on simple tracking devices, but most require sophisticated tracking devices, which further limit their use to electric utilities, industries, and large buildings.
The performance of a solar cell is measured in terms of its efficiency at turning sunlight into electricity. Only sunlight of certain energies will work efficiently to create electricity, and much of it is reflected or absorbed by the material that make up the cell. Because of this, a typical commercial solar cell has an efficiency of 15%-about one-sixth of the sunlight striking the cell generates electricity. Low efficiencies mean that larger arrays are needed, and that means higher cost. Improving solar cell efficiencies while holding down the cost per cell is an important goal of the PV industry, NREL researchers, and other U.S. Department of Energy (DOE) laboratories, and they have made significant progress. The first solar cells, built in the 1950s, had efficiencies of less than 4%.
Photovoltaic (solar cell) Systems content for this section provided in part by the National Renewable Energy Laboratory and the Department of Energy.