Megawatts for Maryland
A recently-completed 2-megawatt energy savings project in Maryland has delivered the largest solar canopy project at an Army installation in the U.S., with California-based Baja Construction Co. designing and manufacturing the carport structures in conjun
By Vicky Boyd
The recently completed 2-megawatt photovoltaic solar power system at the U.S. Army Laboratory Center near Adelphi, Maryland, is much more than an economic way to generate power that also meets renewable energy goals ahead of time. The system generates benefits that get to the heart of the facility's mission.
"We're here to support the community of tenants that we have on the installation the best we can," said J. David Choat, Adelphi Research Center public affairs. "We support the research and development community and ultimately the soldier."
The PV installation includes three carports totaling 1.79 MW-making it the largest solar canopy project at a U.S. Army installation-and two roof-mount systems accounting for an additional 300 kilowatts.
Although the Army had looked at solar power in the past as part of a much larger energy conservation program, it just didn't pencil out, said Tom Bradford, chief engineer for the garrison.
As solar panel prices and interest rates dropped during the past few years, the idea of solar resurfaced-and this time it did make economic sense.
"Ameresco, the general contractor we were working with on the ESPC (Energy Savings Performance Contract) No. 2, said they thought we could refinance this whole project and add to it the renewable aspects to get our renewable energy goals," Bradford said. "The solar isn't considered low-hanging fruit, so it takes a little creative financing to make it financially viable."
Nicole Bulgarino, senior vice president of federal solutions at Ameresco, said the firm has provided this service to a number of federal clients.
"By refinancing a higher rate ESPC with a lower-rate loan and term extension, a customer can implement additional ECMs (energy conservation measures) and remain budget-neutral," Bulgarino said. "Using this approach, Adelphi was able to benefit from the design and installation of a variety of additional measures including new high-efficiency lighting with occupancy sensors; HVAC controls; data center optimization; heat recovery from a large exhaust fan to preheat incoming ventilation air; rainwater harvesting; and a new solar PV system."
The expansive Adelphi laboratory center about 10 miles north of Washington, D.C., sits on more than 200 acres and includes three dozen buildings that house research activities as well as military-related entities, such as the Army Reserve.
In 2010, the Army issued the 44-page Army Energy Vision 2017, which outlines five goals designed to boost energy efficiency and use of alternative energy, while reducing energy consumption and adverse impacts on the environment. Regardless of the goal, the end result should ensure energy security while enhancing the Army's operational capabilities and its ability to carry out its primary missions.
The document also outlined a myriad of energy improvements to installations worldwide, including the Adelphi Center. At the same time, all Army installations were charged with obtaining at least 25 percent of their energy from renewable or alternate sources by 2025.
"Before this year, we were way behind-almost zero percent," Bradford said. "Now that we have the renewables installed, we're meeting the 25 percent alternate energy requirement ahead of the 2025 schedule."
Energy Savings Performance Contracts allow federal agencies to complete energy savings projects without upfront capital costs or special Congressional approval.
Under an ESPC, a federal agency partners with an energy service company. In this case the U.S. Army teamed with Ameresco Inc. The company conducts a comprehensive energy audit, identifying energy saving improvements. It also designs and constructs the project and at the same time arranges necessary financing and provides maintenance as directed by the customer.
The improvements are designed to generate energy cost savings that pay for the project over the duration of the contract.
With the Adelphi center, Bradford said the two ESPCs involved most of the "low-hanging fruit" in terms of retrofits. These were improvements that would provide the largest paybacks over the shortest timeframe.
The two buildings on which the PV systems were installed had relatively new roofs, so Ameresco went with a ballasted racking system from Andover, Massachusetts-based PanelClaw that required no roof penetrations.
Both rooftop projects used Suntech PV panels manufactured at its plant in Goodyear, Arizona, as well as inverters from Advanced Energy Industries Inc. in Fort Collins, Colorado. Rockville, Maryland-based Standard Solar Inc. was the lead solar subcontractor.
|The PV installation at the U.S. Army Laboratory Center near Adelphi, Maryland, includes three carports totaling 1.79 MW, and two roof-mount systems accounting for an additional 300 kilowatts.|
Cranes lifted materials to the roof, where the racking system was roughed in and the ballast installed. Conduit was roughed in beneath the modules, followed by module installation and stringing.
Ballasted combiner boxes were installed, and DC wiring was completed to the boxes.
After Ameresco prepared a feasibility study on the carport system that was approved in late summer 2013, construction began in the fall.
Parking at the laboratory center has always been at a premium. So it took careful planning and communication to let employees know when one of the lots would be temporarily unavailable because of construction.
"We worked with Ameresco and got their buy-in, and we were able to minimize disruption and were able to set up temporary parking," Bradford said.
In some cases, motorists were allowed to park on the sides of internal roadways where it had been previously prohibited. Ameresco also arranged for temporary offsite parking in a church across the street from the main lot.
"It turns out we didn't have to use it as much as we thought we would," Bradford said. "We made sure that everybody knew well in advance that it was going to happen, so there weren't any traffic surprises."
Of the three lots, the main parking lot-known internally as No. 202-required the most coordination, with construction only occurring on a portion of the lot at one time.
Despite initial concerns about how the project might affect parking, Bradford praised Ameresco for making it as painless as possible.
"Construction occurred over the weekends to expedite the schedule and to minimize the disruption to the parking lot," he said. "They worked three shifts, and it was actually pretty smooth."
Ground preparation for the carports began with geotechnical testing to confirm soil conditions under each of the three parking lots.
|Parking at the laboratory center has always been at a premium. So it took careful planning and communication to let employees know when one of the lots would be temporarily unavailable due to construction of the solar carports.|
"Understanding soil conditions is necessary for engineering the size for the foundations needed for the canopy columns," according to Dean Eastlake, Standard Solar's associate engineering manager.
Site preparation included minor tree and landscape removal. But the asphalt pavement was left fairly much intact. Once the column foundation sizes were determined, holes for the foundations were bored, followed by concrete work and column placement. Much of this was completed off hours to minimize parking disruption, said Charles Geppi, Standard Solar's project manager.
Martinez, California-based Baja Construction Co. designed and manufactured the carport structures in conjunction with Albuquerque, New Mexico-based DPW Solar, incorporating DPW Solar's SR Series Solar Ready Shade Structures, said Matt Harrison, Baja's eastern region operations director.
The carports were also designed with winter in mind, Bradford said.
Maryland doesn't receive nearly the snow that the Northeast does. But when it does snow, it can create parking challenges, especially as the snow slides off carports and piles up.
To reduce related problems, the lowest part of the canopies is 12 feet 7 inches from the ground, providing clearance for even the largest of the garrison's snow-removal equipment, Bradford said.
Once foundations had cured, the Baja carports were installed. Beams and purlins were craned into place and attached, followed by racking installed atop the purlins.
Modules were then installed and the strings completed. Wiring and conduit were run to carport-mounted combiner boxes. From there, output DC was run underground in roughed-in conduit trenches to the inverters.
The carports used the same models of Suntech panels and Advanced Energy inverters as the rooftop systems.
This winter saw some severe cold with some snow. The PV system was designed for the climate in this area. For instance, snowguards were installed late in the project to prevent snow slides from the carports.
Project developers faced a hurdle in obtaining final approval from the local utility, Potomac Electric Power Co., to bring the project online, Bradford said. Although all power is consumed on site and is not fed into the grid, the Army had to meet an interconnection agreement with the utility.
"We have a threshold that we cannot drop below-500 KW of incoming power," Bradford said. "We know that these panels could potentially backflow into the utility grid, and we don't have permission for that. They wanted to make sure they verified the system was working."
Portions of the project began generating electricity in late January, and the remainder was brought online by late February.
Although Bradford said the Adelphi center has several other rooftops that might lend themselves to solar, there aren't any current plans for additional PV installations.