Seeking the Sun


June 7, 2012

A California quarry uses the power of the sun to provide energy for its hot-mix plant.

Granite Construction Inc. is proactive when it comes to new technology, especially where the environment is concerned. “We’re engineers and employees who are very interested in technology issues,” says Lee Haven, business development manager for Granite. “If there’s a newer, better, stronger, faster way to do things, we want to be at the forefront of that. We’re very proactive in trying to understand any issue that will make the cost of production a little cheaper and, at the same time, help our communities. We live, play, work, eat, sleep, and raise our children in these communities, and we want to be part of them. It isn’t rhetoric. It’s a way of life.”

In keeping with its proactive policy, Granite began using solar panels at its Indio Quarry last year in hopes that the panels would provide a majority of the power required for the operation of an onsite hot-mix plant.

The Indio solar project was developed using AMONIX CPV (concentrated photo voltaic) technology, and in cooperation with the Imperial Irrigation District, a community-owned utility that provides electric power and irrigation water to the lower southeastern portion of California’s desert. The solar project wasn’t the first industrial-grade project in the Coachella Valley, but it was the first of this particular kind.

“We placed six solar panels on about 14 acres located at our Indio hot-plant facility in an area we call our sustainable green zone,” Haven says. “We actually placed the mega-modules on disturbed ground where we put a lot of our recycled asphalt product. Because of that, we didn’t have to do additional environmental studies for the project. We were able to pull a permit over the counter through the County of Riverside. Make no mistake, the County of Riverside is very interested in assisting opportunities that can provide alternative energy, so they were motivated to assist and see how the whole thing would work.”

AMONIX was one of the first to bring space industry multi-junction solar cell technology to utility-scale projects. The AMONIX CPV 7700 was developed for sunny, dry climates. The dual-access tracking panels follow the sun as it moves from East to West and have Fresnel lenses, which are made of the same acrylic Plexiglas material used to make windshields for fighter jets. “These Fresnel lenses are etched so that they pick up the different auras of the sun — from morning to midday to evening — and concentrate the rays up to 500 times into a high-efficiency, multi-junction cell that excites the electrons and creates the power,” Haven says.

“We installed them ourselves, using our own people,” Haven adds. “We started building the panels in December 2010, and they were ready for commissioning in mid-April 2011. We learned quite a bit while doing it. By the time we finished two of them, we were pretty efficient.”

The six panels, when working at full capacity, should produce about 880,000 kilowatts per year, though Haven says they are finding that’s not going to be the case for the first year. “It’s a windy area,” he says, “and when wind exceeds 25 miles per hour for over 15 minutes, the solar panels go into what’s called ‘stow’ position. When they’re in stow position, they don’t produce power. So it looks like we will produce somewhere between 680,000 and 720,000 kilowatts the first year.”

Because of the plant’s location, Granite has to clean the panels regularly. “We’re out in the desert environment where dust can collect,” Haven says. “When the dust collects on the Fresnel lenses, it hinders production.”

The solar panels are 50 feet tall and 70 feet wide at full array, and maintenance is important for energy production. “We clean each one by hand with a squeegee,” Haven says. “Each panel, at a given moment, produces approximately 53 kilowatts, but just before they are cleaned, they produce approximately 48 kilowatts. Production goes up to as high as 60 kilowatts immediately after cleaning.”

Since this is a net metering project, it’s hot-wired directly into the Indio hot-mix plant. “Our hot plant, at full capacity, needs pretty close to 1.2 million kilowatts per year,” Haven says, “but right at this moment, we’re not at full capacity because of market conditions. When we’re not using the energy, it automatically goes back out to the grid to support the Imperial Irrigation District’s energy production. We’re still analyzing the exact percentage of electricity the solar panels are providing for our hot plant, but it’s probably close to 75 percent, maybe even 80 percent.”

One reason Granite decided to build the solar panels was because of an incentive offered by the Imperial Irrigation District, through a state of California program. Over a five-year period, as long as Granite produces enough power, it can recapture up to $780,000 in incentives. A bi-directional meter measures the total net energy generated and consumed by Granite, as well as the energy generated that is not used by Granite that goes to the electrical grid for use by the community. A yearly audit will determine the amount of the incentive, which will be paid annually, over the five-year period, in the form of a rebate check based on the project’s actual electrical generation amount.

“And of course, there are state tax incentives and federal tax incentives,” Haven adds. “It looks like, on paper, we’ll get the payback in somewhere under 10 years.”

Haven says the incentives are very important in making alternative energy projects happen, and the incentives change from time to time. “More than likely,” Haven says, “it would be difficult to do without the incentives — too costly.”

Granite plans to look for ways to help offset energy costs at more of its plants, and is always looking for opportunities. “We’re very happy with the results at our Indio plant,” Haven says, “but requirements and geography are a bit different at our other plants. When you start thinking about this, you think, ‘Are there wind opportunities? Are there geothermal opportunities?’ We consider all of them and try to find the best alternatives, both in the facilities we run and in understanding what they’re all about, so we can potentially build them for customers as well. The future is exciting. Granite Construction is determined to be a leader in new technology and in improving the environment for future generations.”

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