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Solar power project a double win...

A recently completed 4.5-MW single-axis tracking solar project at Cal Poly environmental benefits and will also maximize educational opportunities for faculty and students.

By Paul MacDonald

A new solar power project on the Cal Poly campus in San Luis Obispo, in California's Central Coast region, has proven to be a winner on several different fronts.

The 20-acre, 4.5-MW solar project will generate 11 million kWh per year, the equivalent of about 25 percent of Cal Poly's total energy needs. It is expected to provide direct savings of $17 million on the university's utility bills over 20 years.

Along the way, the project will also be generating a great deal of energy-related data for the use of faculty and will create "Learn by Doing" opportunities for students.

The university partnered with San Luis Obispo-based REC Solar (which was founded by Cal Poly graduates) to design, construct, and maintain the solar facility. REC Solar is now a Duke Energy-owned company and was a good fit for the project, being a leading provider of solar solutions for colleges, universities, and school districts, with more than 100 completed solar projects for schools that together generate more than 30 megawatts. REC Solar also develops solar curriculum and other means of academic enrichment for school clients.

The Cal Poly project uses single-axis tracking technology, producing nearly a third more energy than a stationary system. It was financed by REC Solar via a power purchase agreement (PPA) with Duke Energy Renewables, which allows Cal Poly to purchase energy at a lower rate, without paying any upfront costs for the system construction and maintenance.

The solar farm was designed to maximize academic applications for both students and faculty by creating a solar engineering and microgrid laboratory in the Electrical Engineering building for students to conduct experiments with solar technology in a hands-on environment—the Learn by Doing plan. A wide variety of solar farm performance data will be continuously measured and made available through a web-based dashboard to aid in solar technology research.

In addition, Cal Poly's Animal Science program will use the site to research vegetation management practices for utility-scale solar farms by grazing the site with its sheep herd.

REC Solar is partnering with the university to provide funds for student and faculty involvement; help develop curriculum that meets Cal Poly's sustainability learning objectives and educate future renewable energy professionals; and collaborate on applied research.


Dennis Elliot, Cal Poly director of energy, utilities, and sustainability, explained that the project required a great deal of planning. "It involved a very complicated land use issue, a very complicated procurement issue, and a very complicated utility interconnection issue, so we had to navigate a lot of items," he said. "A number of things had to come into place for the solar project to happen."

About 13 years ago, the university installed a 135 kW rooftop system that, at the time, was the largest single solar project in San Luis Obispo County.

The university was interested in moving forward with other solar projects, but the power rates were complicating things; Cal Poly owns its substation and is a transmission-level power customer of utility PG&E, and as such, enjoys very low power rates.

"That was a big constraint on us—the solar power technology in the market could compete with primary or distribution level customers, but for it to compete with transmission level customers such as Cal Poly, we had to go large, with multiple megawatts and go with a ground-mount array to minimize the cost of capital and maximize the production of solar power per dollar," explained Elliot.

Key to the 4.5-MW project moving ahead was a California tariff program, the Renewable Energy Self-Generation Bill Credit Transfer (RES-BCT), which provides benefits for local governments to move to renewable energy—and the program also applies to universities in the state.

"The RES-BCT program got us motivated to go through potential site assessment, and we evaluated 11 different sites, mostly on Cal Poly land. The university has a college of agriculture with significant landholdings, and there were some parcels of privately owned land next to campus. We evaluated all those sites with a variety of criteria, slope, terrain, sun exposure, shading, constructability."

 Dennis Elliot (above), Cal Poly director of energy, utilities, and sustainability, at the official opening of the university's solar project. Elliot says a key to the project moving ahead was a California tariff program, the Renewable Energy Self-Generation Bill Credit Transfer, which provides benefits for moving to renewable energy.

A key consideration was also how close each site was to a point of connection to the utility.

"Clearly, building a solar project far from connectivity, and then having to build 10 miles of line to get it connected, would be very expensive—connecting it into a piece of the utility infrastructure that would require significant upgrades could stop a project in its tracks," said Elliot.

Helpful to this process is an online tool that California utilities make available for solar developers so they can do assessments of the system. This PV Renewable Auction Mechanism (PVRAM) is a graphical review of the entire transmission and distribution infrastructure, with data for every substation and segment of the circuit.

"Solar developers can see what the capacity of a circuit is, how much load is on it, how much room is left on it to accept renewable power generation—PVRAM was very helpful for us, and we were able to vet the 11 different sites."

They decided on a 20-acre site that was a sheep pasture of Cal Poly's animal science program. It was immediately adjacent to a PGE-owned substation. "It was literally a stone's throw away," said Elliot, "and it could easily accept 4.5 MW AC of solar power with minimal upgrades."

The site posed some small constructability challenges compared to a flat site that is easier to build a solar array on. But only minimal earth moving was required to prep the site. "There were some high spots to knock down and low spots to fill in," said Elliot. "But for the most part, it was relatively undisturbed except to grub the site and take off some surface plant matter. The plant matter was all set aside, though, and redistributed so the native seed would re-take and populate the vegetation on the site."

The 20-acre, 4.5-MW solar project will generate 11 million kWh per year, the equivalent of about 25 percent of Cal Poly's total energy needs. It is expected to provide direct savings of $17 million on the university's utility bills over 20 years. 

Before the project was even started, the university undertook the California Environmental Quality Act (CEQA) process. This involves reviewing a project for its environmental impact and determining what mitigations are possible to reduce any impact. "We understood what environmental mitigations would be required, and we included that as an appendix to the contract so the bidders would know exactly what they would be required to do," explained Elliot.

In terms of the system components, the university left those decisions to the builder/owner. "We left the vast majority of the design decisions to be made by the vendor—they are best positioned to optimize the project financially," said Elliot. "One of the only things we specified in the contact was the system size." The university had already undertaken the interconnection process to determine the system they could build, and they wanted to build the largest system possible—4.5 MW.

"One other thing we specified was that we wanted single-axis tracking, which makes the system 20 to 30 percent more efficient in total energy production versus fixed tilt arrays." A tracked axis allows the system to keep producing power later in the day compared to a fixed-tilt system.

The university also included provisions for battery storage in the contract, so it would have the option to work with REC Solar to add storage, when it becomes viable in the future. "Ultimately, we think it will become financially viable to add battery storage as power rates continue to change," said Elliot.

 For the solar power project, Cal Poly decided on a 20-acre site that was a sheep pasture of the university's Animal Science Program, which is immediately adjacent to a PGE-owned substation. The Animal Science Program is using the site to research vegetation management practices for utility-scale solar farms by grazing the site with its sheep herd.

The project went out to bid, and the successful bidder was REC Solar.

REC had previously done a small solar project for the university on an office building, about the size of a residential solar power system.

The company's principals were very knowledgeable about the campus in another way: as mentioned earlier, REC Solar was actually founded by two Cal Poly grads, Judy Ledford Staley and Fred Sisson.

"When we carried the solicitation to go out to a number of different companies, we were excited to see that REC Solar responded," said Elliot. "They were very motivated to win this job because it's in their backyard, and Cal Poly is their alma mater.

"REC Solar really got creative and came to the table to negotiate with us to go above and beyond the original vision of the RFQ/RFP—and focus not only on providing us with a solar farm that will perform technically and financially, but to build a long-term relationship to collaborate in areas like university curriculum development, applied research, and other opportunities, to get more value from a solar power system at a polytechnic institution such as Cal Poly."

REC met the qualification requirements, with a wealth of projects completed and operating. "They had the kind of experience we needed for this project, and they did an excellent job."

Due to some supply chain interruptions, REC Solar used two different types of panels on the Cal Poly project. The 16,000 solar panels are split between Trina and REC (a company unrelated to REC Solar), all of them 345 watt modules. Array Technologies provided the tracking systems.

One type, the REC Twin Peak module, is a split design and is on a different string, so this will create some interesting research opportunities, says Elliot, on how shading can impact performance.

"On the project, we can have an interesting A/B comparison between the two different types of modules and how to go about modeling the project to achieve maximum performance. We can determine what the ultimate backtracking algorithm should look like."

The extent of research that can be done by students and faculty has been facilitated greatly by the agreement between REC Solar and the university.

"One thing we wanted to build in at the front end of this project is how to make the solar project available as an academic asset even though it belongs to REC Solar," commented Elliot. "We gave them a wish list of all the assets we would like to have, the instrumentations we would like to have, and all the elements of a solar farm that has data imbedded that we would like to have access to—and we were able to get all that with the REC Solar agreement.

"Essentially, we have all these bells and whistles, and all the data flows into a cloud-hosted database with a web interface that we share access with to faculty and student partners."

With REC Solar being founded by Cal Poly grads, this project was a bit of a homecoming for some of the company's staff. Cal Poly graduate Scott Therien, an electrical engineer and project manager at REC Solar, did his master's thesis on Cal Poly's electrical distribution system-and, ironically, how to increase the adoption of solar power for this type of system.

"It's a neat Cal Poly story," says Elliot. "We worked with Scott and provided him with all the data on our energy use and how we manage energy use at the university to help execute his master's thesis."