GM installs its first solar tracking tree for EV charging

  • 30-Nov-2011 08:17 EST
Solar Tree at GM.JPG

GM's CVO parking lot in Warren, MI, features a Tracking Solar Tree from Envision Solar. A multi-axis tracking system is designed to increase output by 20% compared to a conventional fixed photovoltaic array, according to the companies.

The trunk is concrete on this branchless tree, but its expansive solar canopy shades six vehicle stations capable of fully charging six Chevrolet Volts.

Technical specialists will spend time under this unique solar tree with a multi-axis sun-tracking design that is the newest fixture in the parking lot of General Motors' Company Vehicle Operations (CVO) in Warren, MI.

"It's really a development tool" in addition to being a way to cut electricity costs for the CVO building and to charge Volts, Timothy Miller, Director of GM's CVO, told AEI after a Nov. 16 ribbon-cutting ceremony for GM's first Tracking Solar Tree, an Envision Solar trademarked brand name.

CVO manages and administers the GM company vehicle fleet in North America related to all aspects of vehicle engineering, product development, short- and long-term quality/durability, and plant production, in addition to other fleet needs.

The tree's photovoltaic array uses a proprietary and patent-pending sun-tracking system. Said Desmond Wheatley, President and CEO of San Diego, CA-based Envision Solar: "Each morning the tree tracks to the part of the sky where the sun will rise in the east. It then receives commands from an internal computer to re-orient periodically during the day to always face the sun. The tracking software is proprietary to us and was developed by our partner Lauritzen Controls."

Envision Solar also remotely monitors all of its tracking systems with technical specialists viewing the information on a graphical user interface map.

The ability to track the sun without swinging the solar canopy, which spans 33-ft-10-in x 33-ft-10-in (10.31-m x 10.31-m), is a key feature of the system.

"This is a vital and unique differentiator for us," Wheatley told AEI. "We found a way of effectively ‘bending’ the steel column—which is supported by a concrete base—so that the column will tip the tree’s solar array to always face the sun. One of the crucial factors to this occurring is that the column never rotates the solar array. The column only tips the solar array.”

Although the tree has a tracking span of 360°, it normally tracks through less than 270° to follow the sun's motion through the sky.

"We can set the tilt at any angle, but we try to stay at around 10 to 20° relative to a horizontal plane" for architectural reasons:

Integrated into the solar tree's base are six Level 2 chargers. Each charger is capable of fully re-charging a Volt in 4-6 h.

In addition to Envision's solar tracking tree, GM has been installing stationary solar-powered charging stations from Sunlogics at Volt dealerships in North America via the Chevy Green Zone initiative. The program underscores GM Ventures' $7.5 million investment in Sunlogics PLC, a solar energy manufacturing and development company.

The automaker's solar push is also focused on various GM locations, including the Detroit Hamtramck plant, where the Volt is assembled. The Hamtramck site includes a solar charging canopy as well as ground-mounted panels that provide energy to support the plant.

There are 500 charging stations on GM properties, including the Warren Tech Center, the Milford Proving Ground, and GM's Detroit Renaissance Center headquarters, according to Tony Posawatz, Vehicle Line Executive for the Chevrolet Volt.

"I think we have more workplace charging stations than any other company in the country. So we're supporting electric vehicles not only by making the cars but also by providing the [charging] infrastructure," Posawatz told AEI.

Depending on terrain and other variables, the Volt provides between 25 and 50 mi (40 and 80 km) of pure electric driving via a 16 kW·h lithium-ion battery pack and 111-kW electric drive unit, and up to 344 mi (554 km) of extended range with an onboard 1.4-L engine.

"We have now captured more than 10 million mi (16 million km) powered from the grid with Volts and our retail fleet. I think the age of the electric car—the plug-in car—is really upon us," Posawatz said.

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