Solar goes big with a huge rooftop project.

By Peter Hildebrandt

Tony’s Fine Foods in West Sacramento, CA, wanted to take control of rising energy costs.

The company is a longtime perishable foods marketer, consolidator, and distributor, with nearly 120,000 square feet of temperature-controlled warehouse space. Thirty-eight thousand square feet of its warehouses must be constantly kept at –10°F. Another 60,000 square feet must stay at 34°F. These temperatures must be maintained constantly in their facilities.

All the other air conditioning and lighting, as well as nearly 50 pieces of battery-powered moving equipment, charge from the grid and require a tremendous amount of energy—fueling the company’s decision to find another power source. “Our utility needs are enormous,” says Scott Berger, chief financial officer and co-owner of the company.

The plant is well insulated, but Tony’s uses 4 million kWh of electricity annually.

Solar power was a natural choice. But the food consolidation plant is massive, and solar is usually an option for smaller units needing power. Tony’s looked at solar and a variety of other energy-saving packages, receiving a few bids before a deal was cut in 2005 with Solar Development Inc., a Sacramento, CA–based solar power firm.

The Right Fit for Cooling
The resulting solar array, now one of the world’s largest such installations, is a 1-MW AC system. There are 5,782 modules in the installation, covering an area of approximately three football fields.

The modules were supplied by Sharp Electronics Corp. of Memphis, TN. Each module is rated at 208 watts DC. The life expectancy of this solar array is fairly long. Photovoltaic (PV) modules have a performance warranty of 25 years, but the system is expected to produce electricity for more than 30 years.

The connection is made on the load side, so Tony’s uses it when needed, and any excess electricity generated during peak periods of sunshine is automatically exported into the grid. The meter actually runs backward when the sun shines. The savings the company will gain on its electric bill, based on annual figures for solar generation, is approximately $2,000 per month at the present rate of charges for electricity.

The Self-Generation Incentive Program (SGIP) rebate administered by Pacific Gas and Electric (PG&E) was reserved in May 2005. The engineering design, the building permit process, and the supply of equipment took several months to pull together. The installation started in November 2005, and the array was switched on for testing and commissioning in May 2006.
The food company’s new solar array will supply over 40% of 4 million kWh every year, the equivalent of electricity used for 233 average-sized homes.
“During the daytime we’re producing more power with our solar system than we consume,” says Berger. “But then at night we consume grid power once again. If the grid goes down, the solar system shuts down automatically. This is not a system designed to be a backup to a failure of the grid.”

The primary purpose of this new system is that of helping offset and manage the cost of utility power. With the price of electricity rising—as it appears to do fairly consistently—the company has now sheltered itself to the tune of about 40%. That was what got Tony’s interested in the program to begin with. “Then, when you do the financial analysis of a project like this, of course you look at the power savings,” says Berger.

Other benefits from the program include a 30% federal tax credit, a 7.5% state tax credit on the first 200 kW (approximately $50,000), a property tax exemption, the SGIP rebate for 50% of the total acquisition cost, and a five-year tax depreciation. “There was quite a bit of tax incentive going on to get us over the hump financially,” says Berger. “These all put our project at about a six- to six-and-a-half-year payback.

“That’s still a fairly long payback, but our company has been around since the 1930s, and we have a long-term view of the world. We look at it and say, ‘In six years this will be paid for, and we’ll have an advantage over our competition.’”

Solar Development Brings Parts and Phases of Project Together
Solar Development Inc. of Roseville, CA, hasn’t let its being around just less than two years stop it from taking the plunge with this huge solar project. Kevin Davies, owner of Solar Development, is a UK native with training as a mechanical engineer. Davies first worked designing special-purpose machinery that involved robotics for the plastics, automotive, and nuclear industries.

When he first came to the United States, he worked building a startup plant for BP Solar involving thin film photovoltaics. “Thin film is a different technology than crystalline, and BP Solar worked for a number of years to develop its own product in the thin film business,” says Davies. “They have since dropped out of this market.” Davies then moved to R.W. Schotz, another worldwide solar company. In total, he has at least 10 years of experience in the solar industry.

Solar Development has its own solar contractor’s license and tries to employ local firms for many of the projects, just as it did on this one. This saves on travel expenses and allows the company to keep the price down. “We do a lot of jobs in this area of Sacramento, and it’s great to work with local providers of solar resources, equipment design, and installation, but if I go to do a job in southern California I will also try to employ local solar installers or electricians in that area,” says Davies.

Team Solar Inc. of McClellan, CA, was a local company and functioned as the installer. It pre-panelized the modules in its workshop and then arranged for a crane to lift them onto the roof for installation. “They have excellent, experienced crews for doing the installation work,” says Davies.

Hurdles Come With Seeking Energy Rebate From PG&E
The real challenges for Solar Development came with obtaining the rebate from PG&E. “It all came down to being largely a timing issue,” says Davies. “You apply for the rebate and start moving up a waiting list without ever knowing how fast that’s occurring. This rebate involved a large sum of money—$3.5 million—and there was the issue of when the funds were available from PG&E and the Public Utilities Commission. There is a long waiting list of outfits like ourselves who have submitted a rebate application on behalf of potential customers.”

A nonrefundable fee must be paid to hold the place in line. The fee shows commitment in contrast with all those simply submitting applications with no intention of following through, according to Davies. “When they finally call you and they tell you you’re at the top of the list and you’ve got the rebate funds, you have 60 days to come back with your three-line electrical drawings, your approved interconnection application (this deals with approval to interconnect to the power grid), and a signed contract from your customer,” says Davies. “That last one is tougher than it sounds. The customer doesn’t just sign a contract and make out a purchase order; they sit you down in front of their attorneys and say they want umbrella insurance in place, other insurances, workman’s compensation, and a list of other requirements all written into the contract. The contract bounces back and forth between their attorneys and ours for weeks with adjustments and amendments.

“In 2004 the time period was 90 days plus an extension that you could apply for. Now it’s 60 days with no extensions under any circumstance: If you’re a day late, it’s to the back of the line, and you may have to wait another year. This was a nerve-wracking, sleepless-night experience for us. We did it with a day to spare. The last piece was getting the insurance certificate with the A-Invest insurance requirement table met.”

Solar Development paid a $39,000 insurance premium for this job, and the building permit cost $21,000. “This permit was from West Sacramento, and we’ve never been charged that much before, even for all our combined prorated smaller jobs,” says Davies. “That $21,000 fee was unbelievable; it was the biggest cost surprise for me in the entire project. This was the one thing I actually had underestimated.

“The bottom line on most solar jobs is very tight; these are very competitive bids, and the business is simply not a big profit-margin business. We’re not selling volume. When you just have one or two big projects, you have to make money or you’ll lose your shirt; there isn’t another chance next week to sell another project. This is the nature of this business, and I suppose it’s the reason a lot of people don’t get into this type of work.”

Well over $5 million of the $7.5 million on this project were simply for materials, which have been going up in price. “Material costs were very disproportionate to what had been my experience in working in the special-purposes machinery market. The next biggest cost on the project was that of labor and installation,” says Davies.

It was a catch-22 situation with the modules, too, according to Davies. Even though the modules were made in Memphis and the salespeople with Sharp Electronics are in Huntington Beach, CA, Solar Development was put on a “forecast list,” because all the modules are spoken for, thanks to the demand for solar systems and limited supply. There was simply no spare capacity.
Solar Development wanted a megawatt of modules, an unusual amount for anyone to request. Sharp required that the company show up with both a signed contract from the customer and a letter from PG&E confirming that the rebate had been allocated and that the project qualified under the terms of that agreement.

“My problem was that Sharp would never give me a delivery price for the modules until I came in with the documents. You’re playing a game all the time, doing guesswork. Sharp did come in a bit higher than the price we’d anticipated, but the contract was already signed and we had to make up the difference ourselves. Amazingly enough, it all worked out in the end.”

In the end, the rebate came to Solar Development. Tony’s did not want responsibility for handling it. The total price was $7.5 million. The $3.5 million rebate was already spent on materials for the project, according to Davies.

Roof Installation Proves Relatively Easy
Since there are no moving parts, required maintenance for the solar array is minimal. Solar is a very passive clean energy. The PV modules do need to be cleaned once or twice a year to get the best performance. The supporting structure on the roof and on the ground is made of aluminum and stainless steel fasteners, so the system has a long life expectancy.

Few, if any, engineering difficulties had to be overcome during the installation of the project, according to Davies. “The building received a new roof covering to make sure the array was added to a roof surface with a long life expectancy and a new roof warranty. Structural analysis was also carried out to ensure the roof could take the additional weight.”

The solar panels were supported by an aluminum and stainless-steel framework. Each module stands only about 8 inches off the deck and is inclined at 5 degrees.

“They’re framed modules, but they are still individual modules,” says Davies. “Therefore, there’s nothing to support them and anchor them to the roof. You have to look around and pick the best solution for the rooftop; this customer really wanted a penetration-less system.”

Solar Development ended up choosing Sunlink LLC of Larkspur, CA, a company that develops solar module–mounting systems. “We went through the engineering analysis, looking at all their wind-tunnel calculations, because solar systems must meet criteria for wind,” says Davies. “Because they are a ballasted system, they rely purely on the weight to keep them on the roof.”

The project resulted in one of the largest solar-array installations in the world.

Up on the Roof
In California, complete seismic bonding must take place as well, according to Davies. At Tony’s warehouse the aluminum baseplates around the perimeter of the solar array underneath the substructure are actually glued to the deck of the roof. The bond strength must meet the seismic requirements for attachment to the roof.

“A great deal of repair work had been done to the roof over the years,” says Davies. “Because we were adding 3 pounds per square foot with the modules and the support system, we didn’t want to add any excess weight. We decided that instead of leaving the old roofing material on, we would take it completely off.”

The site actually had four different roofs. One was the lower-level office roof, which had some modules installed on it. The warehouse was a different type of roof structure, but a 75-foot extension had been added to it.
“When we started the job, we were dealing with three different types of roofing material on four roofs,” says Davies. “In our contract we made a contribution towards a new roof, and we also actually paid for the replacement of all the new T-5 light fittings in the warehouse space itself.

“The old lights we took out were just pumping out heat, which was fighting the refrigeration system in the warehouse and costing them more electricity,” says Davies. “These new T-5 fluorescent fittings made for a ‘win-win-win’ situation: reduced electricity cost by 50% from the lighting, improvement of the lighting, and a reduction in heat added to a refrigerated warehouse going back into the plant.” It wasn’t only the solar energy that Solar Development supplied to Tony’s Fine Foods, but a complete energy-saving package.
The new roofing was a four-ply roofing material with an aluminized coating that makes it even more reflective. The modules are screw-fixed to the aluminum frames, and these frames are on baseplates approximately 3 feet by 1 foot in size. The baseplates are spaced so that they are at the corners of each module. Around the perimeter of the roof, these baseplates are bonded to the roof with glue. “The bonding is strictly to meet the seismic requirement,” says Davies. “It has nothing to do with wind protection. This whole system is, in effect, a ballasted system bonded to meet the seismic requirements. What you don’t want to ever do is have a poor-quality roof that has to be replaced in five to 10 years. Tony’s Fine Foods got a new roof, and now they have solar modules on top of it that are warranted for 25 years but are most likely to actually last for closer to 30 years. Those modules will go on in perpetuity as long as they don’t mechanically break down.”

Solar Development engaged the services of a Sacramento structural engineering firm, Point 2 Engineers. Those engineers inspected all the roof attachments on the inside of the building. With a full set of original as-built drawings, they evaluated the entire building structure. Solar Development told Point 2 Engineers the system weight, and the numbers for the structural analysis were validated before all drawings—whether for electrical, mechanical, structural, or civil engineering—were approved.

“No additional reinforcement of the roof was required to support the array at all,” says Davies. “Actually, most roofs are built to handle additional weight of some sort. The beauty of Tony’s [Fine Foods’] warehouse roof was that there were no air-conditioning units on top, due to the fact that it was a refrigerated warehouse. There were no services such as pipes, condensate pipes, gas lines, or related things running across the roof to deal with. It was a very clean roof, and you don’t get many like that.”

Work was scheduled to begin in November 2005. Not long after that, the area got hit by more rain than is usual for the region. This did not help in the installation of the ground-mount system, but wasn’t so much of a problem with the roof-mount system.

“Things got spongy and muddy underfoot,” says Davies. “We had to place a lot more drainage stone down—thousands of tons of stone under the system.”

The facility’s roof was on a slightly lower level, and this is where four of the system’s five inverters were placed. Solar Development built a reinforced frame for the 22,000 pounds of combined weight of these units; therefore, they bridged it with a mezzanine-like structure bolstered by the actual supporting columns of the building. Additional steelwork was placed across one corner from two vertical columns, part of the original building structure. The result was a platform or deck above the actual roof supporting the inverters.

The fourth inverter was placed on the ground on a new concrete pad for the ground-mount system. The capability of the ground-mount array system was 225 kW, a perfect match with one 225-kW inverter. The other four inverters—three 225-kW inverters and one 100-kW inverter—service the rooftop array.

Completion of the system came with the installation of a bidirectional meter so that power can be “sold” back to the power grid. “Once that meter was installed, everything was clean and signed, and all the documentation shown to PG&E, the job was done and we were ready to walk away from the job site, and they cut us a check,” says Davies. “We in turn could then go to pay back the bank—that money was costing us $620 per day in interest for the loan we had to take out to cover the value of the rebate. We paid that interest for approximately three months.

“The biggest single payment was to Sharp Electronics for the modules: just less than $4 million. Sharp was very good to us; they showed up at the site and presented a plaque to us and one to Tony’s Fine Foods for being the end user. This has been our biggest project to date.”

Leading the Way
Aside from all the satisfaction Tony’s experienced with all the work involved on this massive project, Berger is ready for the payback. “It will be really good to see how everything plays out when we see 12 months’ worth of bills,” says Berger. “It’s an awe-inspiring system; all we have to do is wash it off twice a year, and the rest of the time it pretty much takes care of itself. Also, the system shields the roof and adds to its longevity as well as actually keeping more heat from being absorbed into the building and putting more pressure on our refrigeration system.

“On top of all the success we saw with the smoothness of installation with this project, there is clearly the satisfaction that we are doing our part to take carbon out of the air, to take pressure off the grid, and to be a frontline advocate for solar and other forms of green energy,” says Berger. “We’ve been on something of a ‘save-electricity odyssey’ over here. That’s a good feeling. To take smog out of the air and to be involved in a really sound business decision makes this project extra nice.” 

Peter Hildebrandt specializes in science and engineering topics.

DE - March/April 2007