Solar Power

The issue

Solar power is a form of renewable energy in which electricity is generated using sunlight. Solar power is generated from one of two types of configurations: photovoltaic arrays and concentrating solar power.

Photovoltaic (PV) power

PV cells convert sunlight directly into electricity. PV technology is the dominant form of solar technology based on number of applications. It has the advantage of being modular, using PV cells to create PV panels and using PV panels to create PV arrays. These arrays can be varying sizes depending on the user’s needs and the sunlight available.

U.S. PV Potential with PV Units At Least 10 MW
The Solar Energy Industries Association ranks America’s top 10 solar states for 2012. See the full infographic.

PV comes in two forms: crystalline silicon and thin-film panels. Crystalline silicon panels are the solar panels that can often be seen mounted on rooftops. They can be fixed or track the movement of the sun, which allows them to capture more sunlight. Crystalline silicon is the more efficient form with average efficiency between 13.5% and 17.5%, with best-in-class efficiency between 17% and 19%.

Thin-film solar cells are the fastest growing segment of the PV market. In contrast to the crystalline silicon panels, the thin-film panels are amorphous and can be mounted on surfaces such as windows and skylights, making them ideal for diffuse applications. Thin-film modules have an average efficiency between 6.5% and 10% with best-in-class efficiency between 7% and 11%. Sempra Energy has the largest facility to use thin-film technology, its 10-MW El Dorado Energy solar facility in Boulder City, NV.

Wyandot Solar Panel fields, 2010
Wyandot Solar Panel fields, 2010

Solar at AEP

Solar energy has an important role for the future. In 2009, AEP Ohio signed a 20-year power purchase agreement for solar energy with Wyandot Solar LLC, a subsidiary of PSEG Energy Holdings. AEP Ohio will purchase energy from the 10.08 MW Wyandot Solar facility, interconnected to AEP Ohio's North Upper Sandusky substation. The project, located on about 80 acres in Salem Township, consists of 160,000 photovoltaic modules supplied by First Solar, Inc., a Perrysburg, Ohio, manufacturer.

We have also installed rooftop solar arrays at several facilities to learn more about the technology's performance.

Concentrating solar power (CSP)

CSP technology uses sunlight to generate steam to power a conventional turbine and is best used in areas with high solar exposure and low humidity. Mirrors collect sunlight and focus it on a receiver that then transmits the heat to a liquid that is either used to generate steam or power an engine. Existing CSP technologies can track the sun using a one-axis or two-axis tracking. A single axis tracker tracks the sun east to west and a two-axis tracker tracks the daily east to west movement of the sun and the seasonal declination movement of the sun. CSP plants typically require about 800 gallons of water per megawatt-hour generated for cooling purposes but this amount can be reduced by installing a dry evaporative cooling system at the expense of efficiency losses and additional installation capital.

The primary form of CSP currently in use is the parabolic trough, which uses sunlight to generate steam that spins a conventional turbine generator. The power tower is another form of CSP that redirects sunlight to generate steam and spin a conventional turbine generator. By contrast, the third form of CSP is the dish/engine system that redirects sunlight to heat liquid used to move pistons in an engine.