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Solar Power and Wine

The Far Niente winery in Oakville, California decided years ago to increase its use of renewable energy, and its sunny location made solar power the perfect option for achieving it.

Well, almost perfect. One major engineering issue stood in the way of Far Niente’s desire to go solar – and it was very major. The best way to generate the kind of solar power necessary to power the winery facilities – 400 kilowatts total – was to install a one-acre, ground-mounted solar array. Far Niente, along with sister wineries Dolce and Nickel & Nickel, has plenty of land, but every possible inch of it is being used to grow grapes.

Giving over an entire acre of it to install a solar array – no matter how positively it would affect the facility’s energy consumption – was a difficult notion to accept. But one solar array company pointed out that there was a part of the winery grounds where no grapes were growing – a half-acre retention pond.

That was Thompson Technology Industries, a sister company of Navarro, California-based SPG Solar, which had already devised a plan for a floating array while bidding a project for the Yuma City wastewater treatment facility. SPG wasn’t awarded the Yuma City bid, but when Far Niente confronted the daunting question of how to get the solar power it needed without sacrificing too much of its growing capabilities, SPG was ready with the answer.

“ Far Niente was willing to give up a minimal amount of vineyard, but it wasn’t going to get them where they needed to be,” said Dan Thompson, CEO of SPG Solar. “So we came to them with the idea of using their irrigation pond, and by doing that we could get another 200 kilowatts on the ground, and get them the return on investment they needed.”

Far Niente operates on 100 acres of vineyard, with an old winery building built of stone in 1885 housing its hospitality offices, sales and marketing offices and production facility – including fermentation tanks and a cellar storing 900 bottles of wine. The cellar connects to a network of 40,000 square feet of additional caves, where another 2,000 bottles are stored.

Add in a carriage house that serves as home to the winery’s accounting department, as well as a fully operational kitchen that serves hospitality events, and the winery uses 750,000 kilowatts hours of electricity on an annual basis, ranging from a low of 40 kilowatts at night to as many as 200 kilowatts during daytime peak usage in the summer, and into harvest.

The floating array represents a departure, in a sense, from the typical SPG project – which is fully ground-mounted. But the basic power-generation challenge is the same. SPG has to position nearly 2,300 solar panels to effectively reflect the most sunlight during the brightest parts of the day, and feed it to an AC converter that in turn feeds the power either directly to the winery or to the local utility grid.

Greg Allen, president of Dolce Winery and also a trained mechanical engineer, headed up the project from the winery side. Allen expressed pride in both the innovation involved and the results he expects to achieve.

“ It’s the first example of a grid-connected system that’s floating on water and providing power to a land-based, connected enterprise,” Allen said. “The goal was to offset 100 percent of our energy requirements, and we had to design a system that, during optimal times, would be producing three times more than we were actually consuming.”

Economically, this became feasible in 1998 when California law was changed to allow “net metering,” which means a user can produce its own solar energy and either sell any excess capacity to the grid, or, in the absence of sufficient capacity, buy from the grid what its own self-generation failed to provide. Prior to that change in the law, any user producing its own energy had to either use it or lose it.

With the reforms in place, Far Niente is able to sell power to the grid at the retail rate when it has excess, and buy it from the grid at the retail rate when it needs more. Net metering opened up the possibility that Far Niente might actually make money off the solar energy it could produce. But first, the floating array had to work.

That required SPG to secure approximately 1,000 solar panels to pontoons, then float the pontoon on the irrigation pond in conjunction with an additional 1,300 panels in an adjacent, more traditional ground-mounted array.

“ We anchored it, and we’ve got some give to make up for about a 12-foot water change,” Thompson said. “It’s not going anywhere. You want to be anywhere from 150 degrees to about 210, so that gives you a southeast or southwest exposure, which is the ideal exposure. There’s a little give and take on that, and that’s where tracking systems come in.”

The array feeds power through a marine-style ship-to-shore application, and when it reaches land, the power feeds to an AC inverter. The land part of the array has its own inverter, and the two inverters feed to a main distribution panel, which uses a main feeder to tie to the winery’s switching gear.

A problem arose because the solar array inverter is rated at 500 kilowatts AC, while the service transformer was rated at only 230 kilowatts. Far Niente had to either cut the system in half – which wasn’t an option – or put in a 500-kilowatt transformer. The utility couldn’t get a line in for the new transformer because it was too close to the winery’s kitchen, so Far Niente made a deal with its neighbor to put the transformer on the neighbor’s property – in exchange for Far Niente removing overhead transition lines above the neighbor’s property and putting them underground instead.

Not only was that aspect complicated, it also endangered the project’s utility rebates. Local utility PG&E requires all rebate-eligible projects to be completed within one year of acceptance, and the need for the new transformer made it impossible to meet that deadline. Under the circumstances, however, the winery was able to negotiate a six-month extension, and beat the new deadline by a week.

All told, the system cost $7 million. Far Niente was able to get $1.5 million in cash rebates from PG&E, and financed the rest.

Allen said the move to solar power went hand-in-hand with a commitment greater energy efficiency, which the organization studied intensely.

“ Before we embarked on this project, we realized that there would be areas of our energy usage that we could reduce or make more efficient,” Allen said. “We commissioned an energy audit from a couple of sources and we received a very comprehensive report in which every single light bulb, every motor device was categorized, and given our best guesses for their usage, we were able to come up with a summary of energy-efficiency opportunities for the winery to make.”

One of the first and most obvious moves was to insulate the winery’s glycol storage tank, while many other opportunities came from the refrigeration plant, which operated using glycol circulation pumps in an on or off state. By replacing that with a variable flow device, the operators could dramatically reduce the amount of energy required to move glycol through the physical plant – and Allen said the move would pay for itself within two years.
Far Niente also has extensive lighting needs, including landscape lighting that is used for frequent nighttime hospitality events. Allen said he is looking into florescent lighting that seems to offer promising future solutions, but is not yet available commercially.

But nothing has made a bigger difference than the floating solar array, and the decision to put approximately 45 percent of it on the pond – saving the winery approximately $150,000 a year just by eliminating the need to destroy vines.

Just getting the arrays to float, however, was only part of the challenge. The installers also had to ensure that the panels would stay in place during the parts of the year when vegetation in the pond altered the water level.

“ I saw a very nervous group of surveyors measuring the depth of the pond,” Allen said. “But SPG successfully met that challenge, and that was one of the major engineering hurdles of this project.”

The peak hours for solar power generation are between noon and 6 p.m. If Far Niente were to buy power from the grid at noon, Allen said, it would cost 31 cents per kilowatt hour, so the ideal positioning during that period is crucial if the winery is to maximize the value of the array.

“ I want to be facing a little more to the west starting at noon if I have the option,” Allen said.

Far Niente settles up with PG&E at the end of the year – either getting billed or getting a check, depending whether it generates enough solar power to meet its own needs. The floating array went on line in October 2007, and while there was not enough solar power generated to meet the winery’s needs during the winter – putting Far Niente’s account with PG&E in debit mode – it has recently made up the difference and gone into a credit mode.

So you might say Far Niente’s solar investment has found its way to the top of the water.

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