Grid Scale, Solar, Storage

Despite Hurdles, Private PV System Grows

One of the largest privately-owned solar PV systems in the world is now soaking up the southern Georgia sun as Big Frog Mountain, a Tennessee Renewable Energy company, finished installation of a 32 kW, grid-tied, battery-back up PV system, at a private residence.

Warner Robins, Georgia – April 21, 2003 [SolarAccess.com] The approximately US$300,000 PV system is the latest incarnation of an earlier 18 kW system that was destroyed by lightning over a year ago. This time around the new developers were not going to chance a repeat catastrophe that was most likely the combined result of less precautions from the original installers and bad luck from the weather. Thomas Tripp of Big Frog Mountain brought in a lightning expert from NASA to ensure the new system was adequately protected in the event of another lightning strike. The area’s light soil was an immediate concern since dropping water table levels would leave the soil particularly dry and therefore less grounded. The preventative solution was to run several large grounding rods 20 feet deep into the soil below the array and tie the entire system and ground rods together with a buried grid of galvanized conduit. While PV panels can often sustain lightning strikes without much damage, the inverters can be quickly destroyed by a direct hit if the area is not well grounded and the charge is not allowed to dissipate before finding its way into the sensitive inverters. For a system that is not only the largest privately owned PV array east of the Mississippi and perhaps the country, Tripp believes it’s worth the extra effort and precaution. The power generated from the 40 pole-mounted modules each containing eight 100 W panels are fed into 10 Trace SW 5548 inverters. Eight inverters are for individual load sections to feed both the batteries and the residence, and two feed the grid where the owner capitalizes on net-metering legislation to spin his meter backward during times the system’s electrical output dwarfs his electrical needs. According to Tripp, negotiations are underway between the homeowner and the local utility for the excess power to be sold to the utility for possible use in green-tags electricity sales. The hefty up-front price could have been reduced by as much as US$100,000 by leaving out the battery-back up system, but for those seeking the autonomy of uninterruptible power, the battery banks are the best means to the end. Despite attention to efficiency including Energy Star appliances and geothermal ground pumps, the 22,000 square foot home, and family electricity use including that by five children, the large system is required. Online since February, the system has functioned flawlessly and allowed for several hundred dollars worth of savings each month off the owners energy bills. The pole mounted modules take advantage of the increased PV efficiency when panels are mounted at an appropriate angle to the sun depending on the season. Big Frog Mountain set up a plan where they adjust the units twice a year. The panels are now tilted to a more summer-specific angle of 15 degrees, while they were originally placed at 35 degrees in late February. “Not one single drop of sunshine is wasted, we found a home for every bit of it,” Tripp said. “There are plenty of people who can do these systems, and maybe this one will help some others along who have been considering it for too long. This is how real people can do their part to build up the planet in a good way.” Jesse Broehl can be reached at [email protected]