Rockford Solar Partners

Rockford Solar Partners

Eaton solutions reduced installation time by 50 percent, wiring losses by a factor of two, and maintenance, and continue to support a high-availability system.
— Brett Robinson, Principal, Green Circuit

Background
Rockford Solar Partners received approval in 2011 by the Department of Energy (DOE) and the Federal Aviation Administration (FAA) to build a solar PV farm at the Chicago Rockford International Airport in Rockford, Ill. The renewable energy development will be a 62 MW solar farm on 70 acres— the largest airport-based solar PV electricity generating facility in the U.S. The project was part of a broader initiative in Illinois to ramp up solar production and reduce dependence on fossil fuels.

The first phase of a three-phase development plan involved the construction of a 3.06 MW solar plant on 15 acres.

The solar PV farm in Rockford is an American Recovery and Reinvestment Act (ARRA) project that involved numerous organizations, including:

  • Rockford Solar Partners, which is a joint venture between Elgin, Illinois-based Wanxiang New Energy, LLC and Chicago, Illinois-based New Generation Power, Inc.
  • Chicago-based New Generation Power developed and managed the project • Wanxiang New Energy, LLC supplied the PV solar panels from their nearby assembly plant and provided O&M
  • Green Circuit provided project construction management
  • Eaton provided electrical BOS equipment for the utility-scale project

Challenge
The goal at the Rockford solar plant was to maximize production of solar and electrical.

The following key Eaton advantages are helping to reduce plant levelized cost of electricity (LCOE) and have been proved on this installation:

  • Skidless inverter station with innovative throat connection between inverter and transformer that reduced equipment and installation costs
  • Reliable and robust design that minimized plant downtime and maximized energy yield
  • Field support and customer dedication

It was crucial that project costs and energy harvest were on target to support the economic feasibility of the solar farm. Therefore, choosing the right partners and equipment was paramount to make the financial part work.

The land near the Chicago Rockford International Airport is in a floodplain. The soil conditions were so poor that the land was previously used for dirt farming; the crop yields were low and planted to control soil erosion as much as profit. Also, special care was taken so that there was no soil removed from the site to prevent flooding downstream; any soil removed had to be replaced. This also meant that a large truck and crane could not be brought into the plant to maneuver extra-heavy equipment.

“The project had no impact on air quality, water resources, surface water, ground water or the floodplain,” said Michael Pontarelli, senior vice president, project development at New Generation Power. The Rockford site had specific goals related to the environment because the solar farm is located in a floodplain—it was critical to have no adverse effect on the floodplain, surface water and ground water, as well as air quality or resources.

Rockford Solar Partners relied on Eaton BOS components designed for utility-scale solar installations, and Eaton’s commitment to reliably and economically achieve optimal energy harvest.

Solution
Working with a bankable and diversified supplier for complete solar electrical BOS solutions would improve the bankability of the overall Rockford project. Rockford Solar Partners selected Eaton solutions that included:

  • The “skidless” Power Xpert Solar 1500 kW inverter station
  • Transformers from Eaton’s Cooper Power Systems business
  • Medium voltage switchgear solutions
  • Combiner boxes
  • Comprehensive field service support

With Eaton utility-scale solar technology, Rockford Solar Partners was able to reduce the cost of energy by controlling costs and maximizing energy harvest. The installation demonstrates that Eaton utility scale skidless inverters and the direct connection between the inverter and the transformer optimize installation and save costs.

“Eaton has been around for 100 plus years and has a tremendous balance sheet to support their products. Eaton has been building electrical equipment for longer than just about anyone,” said Pontarelli.

The Eaton inverter station, including the inverter, transformer and re-combiner box helped to reduce the installation costs, drive efficiencies and get the system up and running ahead of schedule. Additionally, the Eaton Power Xpert Solar 1500 kW inverter has been running at a high availability since commissioning, maximizing energy harvest at the Rockford solar farm.

Typically, inverters and transformers require multiple connections that are wired together; the Eaton solution enabled a single, direct connection between equipment through a bussed connection. The direct throat connection between the Power Xpert inverter and the transformer yielded numerous advantages:

  • The bussed throat connection replaced approximately 30 x 500 kcmil DLO cables, cutting installation time from several hours to about 2 man-hours
  • The direct connection was made above grade, so there was no need to build trenches, saving time and avoiding the risk of rodents chewing on the wiring insulation
  • Increased system efficiency due to less copper between the inverter and the transformer, which meant fewer copper losses

Brett Robinson, principal at Green Circuit, said “We expected to save 50 percent on installation, and that proved to be true. Installation time was 50 percent faster than compared with a skidded inverter that required wire connections between the inverter and the transformer. Plus, we have fewer inverter and transformer stations because of the size of the Eaton inverter; having a 1.5 MW inverter (as opposed to three 500 kW inverters) also means that there are one-third as many connections and failure points—reducing mean time between failures (MTBF) by a factor of three.”

However, the key advantage to a direct throat connection between the inverter and the transformer is the time savings realized by avoiding multiple wired connections. Furthermore, the inverter station that Eaton delivered to Rockford Solar Partners was an all-in-one inverter enclosure with an integrated DC re-combiner, AC breaker and auxiliary power components, yielding further savings on ancillary components in the inverter station.

Using a 1500 kW skidless inverter-transformer station instead of bundling sub-megawatt inverters allowed Rockford Solar Partners to avoid the use of a skidded solution.

According to Robinson, “The Eaton skidless solution saved installation and transportation costs—a skidded solution that was all wired together would have taken a much larger crane and a lot more rigging.”

Further, the Power Xpert 1500 kW inverter and transformer weigh about 12,000 pounds each, whereas a skidded inverter station weighs upwards of 40,000 pounds. This means that a smaller crane can be used instead of a massive crane—reducing cost, improving convenience and better accommodating the roads leading up to the Rockford solar farm.

“Eaton engineers and technicians that came out on the site really went the extra mile to get the system to realize the potential of energy harvest available,” according to Robinson.

Further, Pontarelli noted that the technicians “could have left the factory settings in place, but they stayed on-site and tailored the settings per site requirements—harvesting the last couple of percent, when normal technicians would have probably walked away before that. They really showed a tremendous commitment to our installation.”

Results
Electrical BOS solutions that are engineered for utilityscale applications and reliable, efficient and enhanced safety are crucial to the success of utility-scale solar installations—helping to maximize energy harvest and reduce overall equipment, installation and commissioning costs.

Construction on the first phase of the Rockford solar farm started in June 2012 and was completed ahead of schedule in mid-November 2012.

Pontarelli added, “The Eaton solution helped Rockford Solar Partners reduce the price of energy. Also, we’re running on 1000 Vdc instead of 600 V. This means that wiring losses are reduced by a factor of about two—wiring losses are typically 3 percent; at Rockford, wiring losses are about 1 percent by going to 1000 V.”

The bottom line is that there are fewer parts to maintain—increasing the robustness and safety margin moving forward.

“Eaton is a manufacturer that can really back up their product, and has one of the best longterm guarantees from a product and company standpoint—reducing financial risk (and the developers’ financing costs),” according to Pontarelli.

Since commissioning, the Eaton Power Xpert inverters have run at a high availability rate (>99%) when there’s been enough irradiance to keep them up.

Adopting solutions that are specifically developed for large-scale solar installations is helping New Generation Partners avoid costs, improve system reliability and reduce plant LCOE. Further, the 3.06 MW solar farm in Rockford is helping to reduce our collective dependence on fossil fuels while reducing carbon emissions by 24,000 metric tons annually.

Overall, the Rockford installation demonstrated that utility-scale solutions developed and backed by a diverse and longtime industry supplier yield savings that support achievement of grid parity.