Nellis Air Force Base
SunPower's PV panels and tracking system combine for a 25% conversion rate.

It may be wintertime, but the sun still shines bright in Southern Nevada where a new $100-million, 14-MW solar power plant finished on Monday, Dec. 17, at Nellis Air Force. The photovoltaic system will provide nearly one-third of the 12,000-employee base's total electrical consumption during summer months for a $1-million annual cost savings. It will additionally reduce carbon dioxide emissions by 24,000 tons annually, which is equivalent to removing 185,000 cars from the roadways.

"Nellis is now home to the largest solar electric plant in all of North America," says Col. Michael Bartley, 99th Air Base Wing commander. "Our base and indeed our entire nation will benefit from the predictable, secure supply of clean energy that this landmark power plant is now generating."

The solar array is located atop a 140-acre sanitary landfill on the west side of the 14,000-acre base. The project, which has been in planning for three years and under construction since April,  is a public-private joint-venture between the U.S. Air Force, PowerLight, a unit of San Jose, Calif.-based SunPower Corp., Nevada Power Co., a unit of Sierra Pacific Resources, Reno, and MWA Renewable Ventures LLC, San Francisco, a unit of Municipal Mortgage & Equity LLC.

PowerLight is the project's developer, designer, contractor and operator. The “Solar Star“ facility consists of 72,000 of SunPower’s proprietary A-300 photovoltaic monocrystalline wafer panels containing nearly 6-million solar cells. The panels, each rated with a 3.1-watt power value, place metal contacts needed to collect and conduct electricity on cell backsides. This eliminates reflectivity thereby creating a uniformly black front surface for enhanced sunlight absorption.

The project additionally uses PowerLight’s PowerTracker technology, consisting of 5,179 single-axis mechanisms that rotate photovoltaic panels throughout the day to follow the sunlight. There will be one tracker per about every 12 panels, each powered by a 1/2-hp A/C motor. The ground-mounted fixed-tilt system uses a space-frame construction anchored by 1-ton precast concrete above-grade footings. The facility, as a result, will achieve a 25% conversion rate, which is about 10% higher than the industry average, claims Thomas H. Werner, PowerLight’s CEO.

Nellis Air Force Base
The $100-million, 14-MW Solar Star facility stretches across a 140-acre landfill area at Nellis Air Force in Southern Nevada.

“There are many silicon products that now get a 20% efficiency rating. It's not that uncommon anymore,” said George Douglas, spokesman for the National Renewable Laboratory, Golden, Colo. “Things have improved in terms of conversion rates.”

The project, in addition to a renewable energy, provides the base with a significant cost savings. The military installation in the northeast Las Vegas Valley currently spends about $10-million annually on energy, including electricity, natural gas, gasoline and diesel. Electricity is the largest part of that tab, accounting for 70% of expenses. The Air Force base pays an annual average of 8 cents per kWh. If Solar Star generates the projected 25-million-kWh annually, it would equate to savings of about 4 cents per kWh, says a Nevada Power spokesperson.

MMA Renewable Ventures secured the project financing and owns and operates the plant, selling power back to Nellis under a 20-year power-purchase agreement. The facility has a 20-year renewable ground lease, with room to expand by 25% in the future, says Howard Wegner, PowerLight's executive vice president.

The plant helps fulfill Nevada Power’s renewable energy requirements. State Assembly Bill 431 enacted in 2003 and AB3 in 2005 requires up to 20 percent of Nevada’s power to come from a renewable resource by 2015 with roughly 5% originating from solar power.

"This solar project at Nellis is a first step of many toward making renewable electricity integral to the operations of the U.S. Air Force," said William Anderson, assistant secretary of U.S. Air Force Installations, Environment and Logistics, during a recent project completion ceremony. "As the largest consumer of energy in the federal government, the Air Force is well-positioned to promote both solar technology and new approaches to its implementation."