Horizontal electrical wires and vertical metal support braces formed two rectangular grids on Monday on the south-facing roof of a livestock barn at Lamar-Dixon Expo Center in Ascension Parish.

The wires and braces were waiting for what sat in the big cardboard box along the edge of the barn’s roof: new Chinese-made solar panels.

Workers with Sunora Energy Solutions of Phoenix were putting the final touches on the rooftop grids so the solar panels could soon be hooked up, parish and Sunora officials said.

Once assembled, the panels will form two 37,750-square-foot solar arrays on top of Lamar-Dixon’s Barn 4 and are the last of six solar arrays that Sunora workers have installed on the roofs of the Expo Center’s barns.

Ken Dawson, parish chief administrative officer, said that based on early estimates, the new panels are expected to cut the Expo Center’s electrical bills by 10 percent a year. He said bills run about $450,000 to $500,000 per year.

The solar arrays also are expected to offset air pollution that would otherwise be released annually during electrical generation, including 400,000 pounds of carbon dioxide, more than 600 pounds of sulfur emissions and more than 400 pounds of nitrogen oxides emissions.

NRG Energy, a Princeton, New Jersey-based utility, is paying $1.25 million to install the arrays for Ascension Parish.

The Ascension project also involves the installation of solar LED lighting for a trail around an Expo Center lake.

The projects are part of $10.5 million in mitigation that was required under a March 2013 federal consent decree settling Clean Air Act violations alleged over emissions from the coal-fired Big Cajun II power plant near New Roads. NRG, which also had to pay fines and do upgrades to Big Cajun II, owns the plant through subsidiary Louisiana Generating LLC.

Tim Turner, superintendent of Sunora, also an NRG subsidiary, said work on the solar arrays, which have already been installed on barns 5 and 6, started Sept. 4 and should be finished this week.

“It’s going according to plan,” Turner said during a visit to the barns Monday.

Once the last of the 1,056 solar panels are installed in the six arrays, workers will install wiring and other infrastructure so the arrays can start producing electricity, Turner said.

Michael Terry III, parish project engineer, said he expected the 300-kilowatt group of solar arrays to be producing energy by the end of October.

Terry added that based on past weather patterns in southeast Louisiana, an estimated five to six hours of sunlight per day and other factors, the six arrays have been initially estimated to produce as much as 390 megawatt-hours per year — which is enough electricity to meet the electrical needs of 39 average U.S. homes for one year.

“Once we have a year under our belt, we’ll be able to collect more data and have a lot more concrete numbers,” Terry said.

While owned by parish government, the 247-acre multi-use Expo Center near I-10 and Gonzales is treated like a separate parish enterprise under Ascension’s budget. Parish President Tommy Martinez has strived for the center’s $2.2 million annual budget not to draw on the parish’s general fund tax revenues but be paid for through event proceeds, onetime state and federal grants, annual state sales tax rebates, private sponsorships and center surpluses built up a few years ago.

The parish and Entergy Corp., which supplies power to the Expo Center and would see the center’s power use reduced due to the NRG-funded solar panels, also are negotiating an agreement related to the solar project and power use at the center.

Martinez has for several years sought to consolidate the number of electrical meters at the Expo Center, a change he contends also will help the center save money on its electrical bills.

Dawson and Michael Burns, spokesman for Entergy, declined Tuesday to detail the terms of the agreement before it is finalized. Burns said, however, an agreement in principle has been reached and the final agreement will be made public.

Jennifer Vosburg, NRG senior vice president for the Gulf Coast region, said a third party connected NRG and Ascension Parish a few years ago as the parish began exploring solar power to save costs at the Expo Center.

Though the vast majority of NRG’s electrical generation remains in coal, natural gas, oil and nuclear, NRG bills itself as one of the largest solar power developers in the nation and is a partner in the nation’s largest solar-panel power plant, which was recently built in the Arizona desert.

“It was a natural fit, and it turned out to be a great partnership,” Vosburg said of the solar project with Ascension Parish.

Parish officials had initially thought the panels might be installed by the first quarter of 2014, but parish and NRG officials pointed to the need to get federal approval of the mitigation project and to ensure the rooftop solar arrays and their electrical connections were designed properly.

Terry noted the parish leadership knew the arrays, which will have a 25-year warranty, would be installed only once.

“We knew when we started this it was a one-time installation, and we really wanted to make sure we were getting the most bang for our buck,” Terry said.

Follow David J. Mitchell on Twitter at @NewsieDave.