Photovoltaic (PV) systems convert sunlight directly into electricity.

TECHNOLOGY

• Crystalline silicon: Most common PV product, has the highest efficiencies, and requires 100 sq/ft per kilowatt.

• Thin film PV: Newer technology growing in market which can be applied on many different materials, has lower efficiencies, and requires 200 sq/ft per kilowatt.

• Module: Many cells connected make up a PV module.

• Array: Many modules interconnected make up a PV array.

• Inverter: Changes direct current (DC) into standard household alternating current (AC) so that the generated electricity can be used by common tools and appliances.1

TYPES
PV systems are commonly found in residential, commercial, and public applications. Over the last few years, the industry has experienced a significant increase in power plant scale applications, typically owned and operated by utility companies or the power is a part of a power purchase agreement entered into by the plant operator with the utility company.
There are two types of PV systems:

• Grid interactive ("on grid") systems require no batteries for storage and backup. System feeds into the utility grid when over generating and feeds off the grid during low-no generation occurrences (i.e. at night).

• Stand-alone ("off the grid") systems require battery backup systems for use during low-no generation times or in the event of a blackout. Batteries can be a a costly on-going investment.

There are many applications for PV systems: ground mounted, rooftop, built-in photovoltaic (BIPV), or photovoltaic roof tiles.

ENVIRONMENTAL IMPACT
Solar generation has the potential to meet 74% to 86% of total U.S. residential electricity demands by 2010 and 2025, drastically reducing the need for fossil fuel electricity generation which is responsible for 36% of the country's emissions of carbon dioxide, with serious effects on human health and climate change.

BENEFITS
Photovoltaic systems are a clean technology with zero emissions. PV systems are reliable; system warranties range from 20-30 years. Solar energy generation decreases dependence on fossil fuel and reduces energy costs. It is projected that the demand for solar electric jobs will be just over 100,000 by 2010.2

DISADVANTAGES

• The initial cost and long term payback of a PV system is a hurdle for consumers, but the California Solar Initiative provides financial incentives for the technology as does the Federal Tax Credit for Renewable Energy.

• Feed-in tariffs, where power generators sell excess power back to the grid, do not exist for residential and commercial applications in California. It is a common misconception, but something that will hopefully come to fruition in the future.

• Solar electricity is not available at night. Therefore, systems must be grid-connected or have a complimentary storage system. Fortunately, most power consumption is during the day, so grid-connected systems can rely on generation credits at night.

VALLEY ACCESS POTENTIAL
The 19 counties of the Central Valley have abundant solar power potential, ranging from 5.6 to 6.0 kWh/m2/day (kilowatt hours per square meter per day).3

SOLAR PV IN THE GREAT CENTRAL VALLEY
There are many examples of solar PV systems throughout the Valley. Most notably is Butte College in Oroville which as of 2009 was able to claim the titel of largest solar campus in California with PV panels generating 44% of electricity used by the college. For more information on solar arrays at Butte College visit www.butte.edu.

For more information on solar PV visit the U.S. Dept. of Energy at
www1.eere.energy.gov/solar/photovoltaics.html

1 US DOE: www1.eere.energy.gov/solar/photovoltaics.html (last accessed April 23, 2009)
2 Green Jobs: www.greenjobs.com/Public/info/industry_background.aspx?id=15 (last accessed April 23, 2009)
3 California Energy Commission: www.energy.ca.gov/2005publications/CEC-500-2005-072/CEC-500-2005-072-D.PDF (last accessed April 23, 2009)