Solar Builder Project of The Year Winner: Staten Solar’s Levee Mount

Levee Mount

Category: Ground-Mount (C&I)
Delano, Calif. | 522 kW

BRAR-pic-2-for-use

The agricultural segment has a conundrum when it comes to adding solar: it could benefit greatly from the power generation, but dedicating too much land for a sizable enough project will cut too deeply into its revenue. Wasting productive land just isn’t an option.

“Typically, farmers love their trees like their children, and they don’t want any harm to them or to their revenue,” says Sandipan Bhanot, president and CEO of Staten Solar Corp.

The owners of a farm in Delano, Calif., were just the latest example for Staten Solar, which has these conversations time and again since 30 to 40 percent of its revenue comes from agricultural installs. Solving this conundrum would be both a huge deal to its customers and its own business.
So, they solved it.

ground mount wnner'Enter the Levee Mount

To avoid using up too much agricultural land, the Staten team looked to an area you’d normally be advised to avoid — a nearby body of water. Farmers construct lagoons to pool water for any sediment to settle so it will not clog sensitive drip irrigation systems. The idea was to install solar panels along the levees of the irrigation lagoons to avoid wastage of more productive space.

In terms of space-saving, it was a no-brainer. Generally, a 500-kW solar system covers about two acres of land, but by strategically placing solar panels along the levees of the lagoon, 20 to 30 percent of the productive land and the associated annual crop revenues are saved. This also helps avoid deforestation. The farmer can now save tens of thousands of dollars every year by harnessing the power of solar energy.

But obviously, execution of the idea is easier said than done, especially considering no one had done it before.  “There are no off-the-shelf racking systems available,” Bhanot says. “Most of the companies you can think of will not supply anything for a project like this.”

Staten engineered its own solution, dubbed the Levee Mount, that had to be both structurally sound for this unconventional location and meet the stringent approval of the local building department.

By strategically placing solar panels along the levees of the lagoon, 20 to 30 percent of the productive land is saved.

By strategically placing solar panels along the levees of the lagoon, 20 to 30 percent of the productive land is saved.

Special considerations

Like any project, the Levee Mount started by accounting for regional wind loads, which is why they chose a strong galvanized steel foundation. But given the close proximity to water, this agricultural solar facility was constructed with special designs from Staten’s structural and electrical engineering staff.

Some examples: AHJ requirements called for at least 10 ft of clearance to the back. The structure also required sacrificial steel so that in the event of any corrosion, the integrity of the project would not be compromised for at least 25 years. They also galvanized the steel to improve its resistance to corrosion and weathering.

All of the posts that support the racking system were driven, which required equipment large enough to ram a 19-ft post into the ground. Some areas of the levees went up to 6 ft and had narrow embankments.

“There were lots of construction challenges; we had to build specialty platforms for the machines to stand on to start ramming through the levee into the ground,” Bhanot says. “This took place in Kern County [Calif.], and they have special inspectors that sit on site to watch and make sure that what was drawn is done in the field. So, that was an added source of anxiety, being unsure how they would respond, but it all turned out great.”

Oh, and there’s also the small matter of direct current lines being so close to a pool of water. Staten Solar wanted to use string inverters and try to minimize the DC wiring as much as possible.

“Normally we’d have, let’s say eight tables feeding one inverter, so we’d put that inverter in the middle of a table so that the cabling from all those tables can be minimized,” Bhanot explains. “In the Levee Mount, we didn’t want to do that. Here we have the inverters on the ground, with longer homeruns, which adds to the cost, but in the overall context it’s a miniscule cost increase for providing more safety because there is no AC voltage on the levees.”

Check out the other 2016 Project of the Year Winners

The levees went up to 6 ft and had narrow embankments.

The levees went up to 6 ft and had narrow embankments.

More Levee Mounts to come

This 522-kW Levee Mount project in Delano is just the first of many that have gone through the permitting stage and are awaiting construction as Staten Solar looks to make this strategy a bigger part of its focus going forward.

“We can go out to the customer and, if others say you have to cut down 300 trees, we can say they can preserve maybe 200 of them. Makes a huge difference,” Bhanot says.

In fact, the company is pitching customers as early as it can on the innovation to hopefully influence construction of the lagoons at the outset.

“Typically, we only install south-facing panels, so Levee Mounts can be done on the northern and southern edges of the lagoons,” he says. “We have been working with farmers so that they are now constructing their reservoirs based on our recommendation where the northern and southern edges are much longer than the east and west.”

After climbing this hill and placing PV on top of it, Bhanot thinks the next step to further improve PV’s value in the ag sector is getting AHJs on board with floating solar on top of the lagoon itself.

“We need to work with the AHJs to get them over the hump on that. We hopefully will have announcements on that next year,” Bhanot says, in what we can only assume is a spoiler alert for the 2017 Project of the Year awards.

— Solar Builder magazine

Ground-Mount Project of the Year: USVI Solar I

usvi-1

St. Thomas, U.S.  Virgin Islands | 5 MW

Daunting. That was the first word Sam Ley, energy systems engineer for AES Distributed Energy, used to describe USVI Solar I, our Ground-Mount Project of the Year. And really, we could have just printed that one word in bold, 72-point type near the photos and summed up USVI Solar I without telling the whole story. But let’s go ahead and tell it anyway.

chart 3Located on a rocky, overgrown steep hill that was freely available to the Virgin Islands’ Water and Power Authority (WAPA) because it was unusable for development, the USVI Solar I project required some serious engineering and patience to get online. But USVI Solar I is more than just a harrowing solar development war story as this project is hugely important for the 40,000 people living on the island.

In 2009, the U.S. Department of Energy reported that the Virgin Islands was almost 100 percent dependent on imported oil for electricity, water desalinization and transportation, resulting in electricity costs that were nearly four times the U.S. national average. Since the Hovensa oil refinery closed in 2012, WAPA has utilized expensive, polluting diesel generators for electricity. Now, WAPA has a new vision for generating renewable energy and stabilizing its grid with the goal of reducing fossil fuel use by 60 percent by 2025.

Modules used: Yingli’s 72-cell series for large-scale projects 

This 5-MW PV plant is the largest PV plant in the U.S. Virgin Islands and is expected to generate approximately 7.9 million kWh of electricity annually — which is about 10 percent of the island’s energy needs and provides lower-cost energy to WAPA at a fixed rate. And none of it would be possible without the right screw.

Screw the Bedrock

Ley and his team thought of a few ways to approach the site initially — from terracing the site and doing a ton of civil work, to mostly leaving it as is. They ended up doing a minimal amount of civil work and adapting the racking to the existing contours of the land. This required additional flexibility from their plan and the system architecture because thick patches of shrubbery obscured a lot of those contours. In addition, some areas of the site were dirt and other areas were exposed bedrock.

USVI Solar project winner

“We started by cutting out roads to access areas of the site, and then taking our original layouts and adapting them as we approached each section of the site to add and remove racks,” Ley says.

RBI Solar supplied the racking and also engineered and sourced a ground screw that was able to both dig and hold in soil or dig into the bedrock, jam into the cracks and affix itself there.

“This is a site where it’s difficult to draw what you think will happen, and then have it happen,” Ley says. “Literally as they are drilling in a screw that didn’t take, or if there is a small change in topography, they’d X out a rack and figure out where else to put it.”

Mounting used: RBI ground-mount system minimizes field labor 

Since the layout had to change considerably as the project progressed, the electrical architecture had to be easily adjusted. To that end, AES chose KACO 32- and 50-kW string inverters.

“As we were moving and shuffling racks around, we had inverters spread all over, so it was easier to adjust the stringing maps and inverter assignments as we built,” Ley says. “If the design was too rigid, it wouldn’t have been able to accommodate those changes in the field.”

Ley admits that as much as they prepared for on-the-fly field changes, the amount of flexibility they needed was more than anticipated.

Blame it on the rain

Construction started in earnest in late spring 2014 and started to look like a PV project by early fall. The civil work took a little longer than anticipated, which drug construction into hurricane season. Hurricane Cristobal was unkind.

“We were caught right before the main storm water improvements were ready to go,” Ley says. “Quite a bit of erosion and a tremendous amount of rework had to be done.”

But obviously this was not a unique event. This area is known for heavy rainfall and winds that can approach 195 mph. So, while being hunkered down in a storage container during a storm that produces 2 in. of rain in 24 hours sounds less than ideal, the storm provided the perfect case study for testing the team’s initial water management plan.

“We had an initial comprehensive plan, but like most plans on this project, the plan came crashing into reality. A lot had to be revised,” Ley says.

After individual rain events, whole sections would need to be reworked: erosion would develop too quickly, sections of racking would need supplemental concrete, roads needed rebuilt, lots of additional new drainage paths needed to be created.

“It turned into an empirical process,” Ley says. “The regional EPA has been using some of the results and methods they’ve seen us doing on site as a model for other sites that they are bringing up in similar climates, where the rainfall is high and the soil is prone to erosion.”

The USVI Solar I plant will support 10 percent of the island’s energy needs.

The USVI Solar I plant will support 10 percent of the island’s energy needs.

Distributed design

The distributed design of the project and the selection of string inverters came with several benefits. One is administrative. The system was partially financed by 18 treasury grant applications under the Investment Tax Grant finance structure, which means, electrically speaking, this one project had to be 18 somewhat distinct electrical sub-systems. That wouldn’t be possible with central inverters.

Inverters used: KACO’s line of TL3 inverters 

There are the practical benefits as well. For one, an island like St. Thomas presents logistical obstacles. Getting a 5,000-lb centralized inverter from customs to the site could take weeks to line up. Secondly, string inverters provide more flexibility, which is hugely valuable for site planning and grid stability. The St. Thomas grid is small and stiff but fairly resilient. But the USVI Solar I plant is its first excursion into renewable supply, and there are not a lot of sophisticated grid controls.

“I would have been nervous about putting large, heavy pad-mounted equipment there,” Ley says. “The site is going to move over time. We are going to be adjusting things — an O&M procedure there is just to continue to maintain the drainage systems on the site. And having to do that with 5,000-lb central inverters on huge slabs is not something I’d want to contemplate going back through again.”

Specifically, 96 separate inverters are connected to 10 transformers. Since the array is located in an area prone to hurricanes, the smaller inverters will allow the site to remain online in the case of external or equipment faults.

As mentioned, USVI Solar I was certainly daunting, but in 2015, daunting solar projects are still doable — and, after completion, pretty damn impressive.

— Solar Builder magazine