Project Profiles

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The history of southern Oregon’s Buckhorn Springs dates back to the late 1800s when James Clarke Tolman built a resort to take advantage of the site’s mineral water and carbon dioxide springs, which many believed had curative properties. Buckhorn Springs’s current owners, Bruce and Leslie Sargent, purchased the run-down resort in 1987 and embarked on a life-long family effort to restore the historic structures and create a modern retreat center steeped in the site’s rich history. In the summer of 2015, True South Solar (TSS) added a modern event to the property’s historical time line—a 24 kW PV system.

The property’s sloping site was a good candidate for six pole-mounted arrays. The crew outlined property and creek setbacks and mocked up the pole-mount locations with paint to determine the optimal spacing between them. Although they staggered the poles down the hill in an organic manner, the installers made sure to line up each set of poles on the east-west axis to create a nice visual line between them.

TSS selected MT Solar’s Top of Pole Mounts for the project. The product includes a chain hoist and pulley system that allows workers to assemble the array at waist level and lift it into place, minimizing the need for ladders or heavy equipment. MT Solar’s pole mounts integrate with the installer’s preferred top-down rail system. TSS used SnapNrack rails for the project, in part due to the crew’s familiarity with installing this particular rail system.

This was the first time TSS had worked with MT Solar’s pole mounts, and a few unanticipated challenges came up. The system includes a hand crank that allows individuals to easily adjust the array’s tilt angle. However, the crank is on the backside of the pole where a combiner or disconnect is typically located. To avoid working clearance issues, installers may need to mount enclosures and associated circuits on the side of the pole when using the MT Solar mount. Another product-specific consideration is that since installers assemble the array at waist level before lifting it into place, they need to delay the installation of enclosures or conduits that fasten to the pole until they raise the array into its final position. TSS did not find this to be a big issue, but it did alter its standard pole-mount installation workflow.

The project uses three SunPower 7 kW non-isolated inverters with dual MPP trackers. Its physical and electrical layout worked out nicely, with a dedicated MPPT for each pole-mounted array. Each mount supports 12 SunPower modules configured in two six-module source circuits. TSS used MC4-Y connectors to parallel these circuits. Because the system uses non-isolated string inverters, Code requires both ungrounded power conductors to be de-energized when the circuit is opened. Using MC4-Y connectors to parallel two source circuits allowed TSS to use two-pole rather than four-pole disconnects, reducing both material and labor costs.

“The Buckhorn Springs project was our first experience with the MT Solar pole-mount system. Although we encountered a few unanticipated challenges, the added speed and safety of building arrays at waist level with two feet on the ground has sold us on this product.”

Ry Heller, True South Solar

Overview

DESIGNER AND LEAD INSTALLER: Ry Heller, True South Solar, truesouthsolar.net

INSTALLATION CREW: Josh Neale, Colin Bashant, Mike Goglin and Oshia Golden

DATE COMMISSIONED: August 2015

INSTALLATION TIME FRAME: 6 days

LOCATION: Ashland, OR, 42.2°N

SOLAR RESOURCE: 4.9 kWh/m2/day

ASHRAE DESIGN TEMPERATURES:  96.8°F 2% avg. high, 17.6°F extreme min.

ARRAY CAPACITY: 23.54 kWdc

ANNUAL AC PRODUCTION: 32,020 kWh

Equipment Specifications

MODULES: 72 SunPower SPR-E20-327, 327 W STC, +5/-0%, 5.98 Imp, 54.7 Vmp, 6.46 Isc, 64.9 Voc

INVERTERS: Single-phase 120/240 Vac service; three SunPower SMA America SB7000TL-US with Secure Power Supply, 7 kW rated output, 600 Vdc maximum input, 245–480 Vdc MPPT range, 125–500 Vdc operating voltage range, dual MPPT

ARRAY: Six modules per source circuit (1,962 W, 5.98 Imp, 328.2 Vmp, 6.46 Isc, 389.4 Voc); two source circuits per MPP tracker (3,924 W, 11.96 Imp, 328.2 Vmp, 12.92 Isc, 389.4 Voc); four source circuits per inverter (7,848 W, 23.92 Imp, 328.2 Vmp, 25.84 Isc, 389.4 Voc); three inverters total; 23.54 kW array total

ARRAY INSTALLATION: Ground mount, six MT Solar 8-inch Top of Pole Mount, 180° azimuth, fully adjustable array tilt from 0° to 90°

STRING INVERTER AGGREGATION: 125 A inverter combiner panel, 40 A two-pole breaker per inverter

SYSTEM MONITORING: SunPower monitoring system with smartphone app

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Phase I of the Mandalay Bay PV plant has a total capacity of 6.4 MWdc and utilizes approximately 850,000 square feet of the Mandalay Bay Conference Center’s 950,000-square-foot roof area. The system is designed to the 2012 IBC and NEC 2008 per Clark County Codes in May 2014, when the designer submitted the permit application for review and approval.

Sunora Energy Solutions deployed the array on Unirac’s RM roof-mount system, secured by 49,026 ballast blocks (32 pounds each) and 4,310 anchors hot-welded to the surface TPO membrane to satisfy uplift load requirements. There are no mechanical attachments between the racking system and the buildings’ steel structures. Sunora installed the roof-mounted inverter aggregation switchboards and oil-filled transformers on steel racks mechanically attached to the building’s main columns and beams.

This project is unique in that the installers positioned the dc and ac electrical equipment that supports the PV plant on the roof adjacent to the PV arrays. This electrical equipment includes the string inverters, panelboards, switchboards and a DAS system, plus three 1 MVA and one 1.5 MVA transformers. A 12 kVA medium-voltage collection system delivers ac output power to new switchgear on the ground floor. The point of interconnection is approximately 3,800 feet from the switchgear, at one of the main electrical service points between NV Energy (NVE) and Mandalay Bay.

A challenging aspect of the project is that no PPA is in place with NVE. Contractually, all solar-generated power must be delivered to and used by the Manadalay Bay property. For this reason, the project team installed multiple safeguards to ensure that the PV system will not backfeed into NVE’s system. The solution includes a Kirk Key system located at both the designated solar plant switchgear and the main NVE interconnection point to the Mandalay Bay facility, which ensures that no one can open the main NVE breaker without opening the solar breaker first. In addition, a relay and communication system measures the Mandalay Bay facility load and the solar power output. If the PV system output reaches 92% of the total load, a curtailment feature in the relay system forces an automatic reduction in power output. Any issues that occur trigger alarms, and NVE, NRG and Mandalay Bay can use the relay control to remotely limit plant output. The inverter software also features a curtailment function that a system manager can use remotely if power generated is reaching power usage levels. Based on the load profiles and expected output of the solar arrays, NRG anticipates that curtailment will not be necessary in the life of the system.

“The MGM Phase I and Phase II solar projects at the Mandalay Bay Convention Center make use of the world-class Nevada solar resource and allow Mandalay Bay to generate a significant portion of the convention center’s electrical load. With an expected Phase II completion date of November 2015 and an installed capacity of 8.8 MWdc, the two projects combined will comprise one of the largest rooftop solar arrays in the US.”

—Randall Hickok, senior vice president, asset management and engineering, NRG Renew

Overview

DESIGN: Sunora Energy Solutions (an NRG Renew subsidiary), sunoraenergy.com; DLR Group, dlrgroup.com

CONSTRUCTION: Sunora Energy Solutions

DATE COMMISSIONED: February 2015

INSTALLATION TIME FRAME: 120 days

LOCATION: Las Vegas, NV, 36.1°N

SOLAR RESOURCE: 7.62 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 108°F 2% average high, 25°F extreme minimum

ARRAY CAPACITY: 6.354 MWdc

ANNUAL AC PRODUCTION: 10,379 MWh

Equipment Specifications

MODULES: 3,780 Hanwha HSL 72 300, 300 W STC, +5/-0 W, 8.22 Imp, 36.5 Vmp, 8.72 Isc, 45.5 Voc; 13,320 Hanwha HSL 72 305, 305 W STC, +5/-0 W, 8.32 Imp, 36.7 Vmp, 8.8 Isc, 45.7 Voc; 4,296 JA Solar JAP6-72-285, 285 W STC, ±3%, 7.7 Imp, 37.01 Vmp, 8.38 Isc, 44.6 Voc

INVERTERS: 3-phase 480 Vac service, 203 SMA America Sunny Tripower 24000TL-US, 24 kW rated output, 1,000 Vdc maximum input, 450–800 Vdc MPPT range; 203 SMA America Connector Units combine strings at each inverter, 15 A fuses

ARRAY: Roof Areas 1–4, Hanwha modules, 18-module 1,000 Vdc nominal source circuits (for 305 W modules: 5,490 W, 8.32 Imp, 660.6 Vmp, 8.8 Isc, 822.6 Voc), six source circuits per inverter (32.94 kW, 49.92 Imp, 660.6 Vmp, 52.8 Isc, 822.6 Voc); Roof Areas 5–6, JA Solar modules, 12-module 600 Vdc nominal source circuits (3,420 W, 7.7 Imp, 444.12 Vmp, 8.38 Isc, 535.2 Voc), eight source circuits per inverter (27.36 kW, 61.6 Imp, 444.12 Vmp, 67.04 Isc, 535.2 Voc); 6.354 MWdc array total

ARRAY INSTALLATION: TPO roof membrane, Unirac Roof Mount (RM) system, ballast and hot-welded anchor system, 180° azimuth, 10° tilt, Eaton’s B-Line series dc cable management system

INVERTER AGGREGATION: 22 Eaton Pow-R-Line 3FQS 400 A panelboards, four Eaton 2,500 A Pow-R-Line switchboards, combined inverter output transformed to 12 kVac via roof-mounted Eaton’s Cooper Power series medium-voltage pad-mount transformers with switchgear located at ground level

SYSTEM MONITORING: Locus Energy

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O2energies developed, owns and operates more than 80 MW of solar farms in North Carolina. Its Chocowinity Solar project is located in Beaufort County, near the Atlantic coast, in the small town of Chocowinity (population 823). The town’s name comes from the Tuscaroran Indians, who lived there several hundred years ago, and the solar farm site has been in agricultural use since 1938. The area is known for its pocosin wetlands—the raised bogs of the Atlantic coastal plain. As such, the project team performed an environmental site assessment, as well as stream and wetland verification, early in the project development process. Although the site is not located near a perennial stream, contractors protected its riparian buffers and adjacent wetlands throughout construction.

Since Chocowinity had no language pertaining to solar farms in its existing zoning ordinances, the town had to draft and adopt language for a new solar farm amendment before it could grant a conditional-use permit. That process, concurrent with the development phase, took the better part of a year. The construction phase of the project took approximately 4 months. More than 10 local contractors—including grading, equipment rental, electrical contractors, surveyors and security contractors—provided services and materials. The solar farm will continue to use a local security contractor and will contract with a local farmer for grounds maintenance.

The construction phase of the project ran from September through December 2014. Loose to medium-dense clayey sand and slightly clayey sand underlies the uppermost layer, or plow zone, at the site. This layer is interbedded with very soft to stiff clay, which necessitated a 15-foot pier embedment depth for the rack foundations. Poor weather created complications for the end-of-year completion deadline, as rain, ice, snow and freezing temperatures resulted in a knee-deep buildup of icy mud covering the site. With deadlines looming, contractors poured three concrete equipment pads, and the team received the inverters and transformers on-site. Positioning this equipment was delayed when, only 200 feet from the main entrance gate, the crane sank up to its chassis, and workers had to pull it out of the mud with an excavator. After three successive failed attempts to navigate to the pads, the project manager brought in a rough-terrain four-wheel-drive crane. Much to the construction team’s relief, the fourth positioning attempt was successful, allowing completion of construction without further delays.

The design team chose Eaton’s Power Expert 1670 inverters for the site, in part because they allow full power output while supporting ±0.91 power factor range. The close-coupled Eaton-Cooper power transformers and the Eaton Pow-R-Line recombiners with dc circuit breakers create a synergistic design. The Eaton engineering team lent its expertise to the equipment specification and system commissioning. The combination of SolarBOS disconnecting combiner boxes with the Eaton dc breaker recombiners allow technicians to easily and safely partition the arrays and subarrays for commissioning, testing and maintenance. PowerSecure Solar provides O&M for the site.

“We are proud to celebrate our tenth successful solar farm in North Carolina. It was a pleasure working with the local community and elected officials. The Chocowinity solar project is one of the best in our fleet.”

—Logan Stephens, project development manager, O2energies

Overview

DEVELOPER: O2energies, o2energies.com

DESIGNER: Jocelyn Jordan, engineer in training, PowerSecure Solar, powersecure.com

ENGINEER: James D. Ham, professional engineer, Entech Engineering, entecheng.com

PROJECT MANAGER: Vincent Zarallo, project manager, PowerSecure Solar

DATE COMMISSIONED: December 2014

INSTALLATION TIME FRAME: 120 days

LOCATION: Chocowinity, NC, 35.5°N

SOLAR RESOURCE: 4.93 kWh/m2/year

ASHRAE DESIGN TEMPERATURES: 95°F 2% avg. high, 14°F extreme min.

ARRAY CAPACITY: 6.405 MWdc, 4.998 MWac

ANNUAL AC PRODUCTION: 9,494 MWh

Equipment Specifications

MODULES: 21,000 Hanwha HSL 72 305, 305 W STC, +5/-0 W, 8.42 Imp, 36.3 Vmp, 8.85 Isc, 45.1 Voc

INVERTERS: 3-phase 22.9 kV medium-voltage interconnection; three Eaton Power Xpert Solar 1670, 1,667 kW/1,850 kVA rated output, 1,000 Vdc maximum input, 550–800 Vdc MPPT range, inverter integrated dc and ac disconnects; each inverter is close-coupled to a pad-mounted 1,850 kVA Eaton-Cooper Power Systems 22.9 kVac primary/355 Vac secondary transformer

ARRAY: 20 modules per source circuit (6,100 W, 8.42 Imp, 726 Vmp, 8.85 Isc, 902 Voc), 22–24 source circuits per combiner, 15 combiners per inverter, 350 source circuits total per inverter (2,135 kW, 2,947 Imp, 726 Vmp, 3,098 Isc, 902 Voc); 6.405 MWdc array total

ARRAY INSTALLATION: Ground mount, Daetwyler Clean Energy Modu-Rack-DB-L, landscape module orientation, 180° azimuth, 20° tilt

SOURCE CIRCUIT COMBINERS: 45 SolarBOS CDKT400-24-25-N4 Disconnect Combiners, 15 A fuses

RECOMBINERS: Nine Eaton Pow-R-Line recombiners (three per inverter), five 350 A molded case breakers per recombiner

SYSTEM MONITORING: Draker PV250-120

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The $5.7 million Anaheim Convention Center PV project was commissioned in August 2014. At the time of interconnection, the 2.372 MWdc installation was the largest city-owned, roof-mounted array on a convention center in North America. Borrego Solar Systems designed and installed the system, which Anaheim Public Utilities owns and manages.

The array comprises 7,908 Yingli Solar modules that cover 300,000 square feet on three rooftops of the convention center. SunLink’s Core RMS galvanized steel racking system minimizes ballast requirements by connecting both north-south rows and east-west array sections to form a structural grid that disperses loads across the array.

The system’s bipolar Advanced Energy AE 500NX-HE inverters require compatible array aggregation components. Bentek source-circuit combiners and recombiners designed for bipolar arrays meet this need. Installed at ground level, the four Advanced Energy inverters feed a 2,500 kVA 480 Vac–to–12 kVac transformer interconnected with the convention center’s 12 kV service.

Clear lines of communication are critical when working with a large facility such as this one. Faced with heavy traffic from a full calendar of events, Borrego Solar’s team met weekly with convention center staff and subcontractors on-site to present 3-week “look-aheads.” This coordination resulted in a nimble construction team that could mobilize crews and move equipment and staging areas as needed to stay clear of convention center operations.

“Installing solar on the convention center furthers the city’s commitment to renewable energy initiatives. Anaheim was able to add a cost-effective renewable resource that utilizes the abundant sunlight we are fortunate to have in this region.”

—Dukku Lee, general manager, Anaheim Public Utilities

Overview

DESIGNER: Aharon Wright, senior design engineer, Borrego Solar Systems, borregosolar.com

LEAD INSTALLER: Mike Daugherty, senior project manager, Borrego Solar Systems

DATE COMMISSIONED: August 2014

INSTALLATION TIME FRAME: 120 days

LOCATION: Anaheim, CA, 33.8°N

SOLAR RESOURCE: 5.18 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 88°F 2% avg. high, 36°F extreme min.

ARRAY CAPACITY: 2.372 MWdc

ANNUAL AC PRODUCTION: 3,579 MWh

Equipment Specifications

MODULES: 7,908 Yingli Solar YGE-U72 YL300P-35B, 300 W STC, +3/-0%, 8.37 Imp, 35.8 Vmp, 8.86 Isc, 45.2 Voc

INVERTERS: 3-phase 12 kV medium-voltage service interconnection; four Advanced Energy AE 500NX-HE, 500 kW rated output, ±600 Vdc maximum input, ±330–550 Vdc MPPT range

ARRAY: Bipolar; 12 modules per source circuit (3,600 W, 8.37 Imp, 429.6 Vmp, 8.86 Isc, 542.4 Voc); 7–16 source circuits per combiner, 12 combiners per inverter; array total: 659 source circuits, 2.372 MWdc  

ARRAY INSTALLATION: TPO roof membrane, SunLink Core RMS racking system, 202° azimuth, 5° tilt

SOURCE-CIRCUIT COMBINERS: 48 Bentek Bipolar Integrated Disconnect BTK 16D 200 A, 1 Bentek Bipolar Integrated Disconnect BTK 12D 100 A, 15 A fuses

ARRAY RECOMBINERS: Three Bentek Bipolar recombiners, 12-pole, circuit breakers; one Bentek Bipolar recombiner, 14-pole, circuit breakers

SYSTEM MONITORING: AlsoEnergy with kiosk display

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The Konterra Solar Microgrid project is one of the first commercial-scale grid-interactive solar microgrids in the US. This project received the Maryland Energy Administration (MEA) Game Changer grant, awarded for projects that display the potential to significantly advance the state’s clean energy market through commercially available technologies. One of the team’s main goals for the project was to leverage frequency regulation revenues to enable cost-effective deployment of grid-tied solar plus storage for backup power during grid failures. The integrated storage ensures continued PV generation during grid outages, and incorporated frequency regulation services improve the economics of battery deployment.

Standard Solar developed the project and fulfilled all engineering, construction, and operations and maintenance tasks. It teamed with Solar Grid Storage (recently acquired by SunEdison) to finance, integrate and operate the battery storage system and inverters. Konterra, a real estate development and management company, is the PV system owner, host and energy offtaker. The project is located at the Konterra headquarters in Laurel, Maryland.

The system concurrently utilizes two energy sources—a PV parking canopy system and an energy storage system—to power selected essential loads in the event of a utility outage. The 402 kWdc array consists of Suniva modules installed on Solaire 360 T carport structures. The array is configured in two 201 kW sections that feed one of two 250 kW Princeton Power Systems inverters, which manage both the energy storage and PV systems simultaneously on the dc side. The storage system uses AllCell Technologies integrated lithium-ion Sanyo cells to provide 300 kWh of total on-site storage capacity.

The Konterra solar-plus-storage facility has capabilities beyond those of a simple grid-tied with battery-backup PV system. As a distributed grid-interactive solar-plus-storage microgrid, it can both discharge in parallel with the grid (grid-interactive mode) and also isolate itself from the grid for stand-alone operation (islanded mode). To properly and safely operate, and automatically switch between the two modes, the system includes a comprehensive monitoring and controls system, along with several critical pieces of integration equipment, including eight Shark meters. These meters allow the control system to monitor overall system activity and provide closed-loop verification of switch operation.

Unlike a standard grid-tied with battery-backup PV system, Konterra’s facility has the unique ability to provide fast-response frequency regulation support to the local grid—in this case operated by PJM Interconnection, a regional transmission organization serving several eastern states. Regulation services can improve power system stability by correcting for short-term changes in electricity use, according to PJM. By participating in the frequency regulation market, Konterra helps PJM match grid generation to load and adjusts generation output to maintain the desired frequency. As an added benefit, Konterra’s frequency market participation generates revenue for the storage system owner.

“We commissioned this project after months of dedication, innovative work and communication among all project partners. This was one of the first commercial-scale, grid-interactive solar-plus-storage projects in the country. There’s considerable potential for these types of projects, and we expect to see many more as renewable penetration increases.”

Tony Clifford, CEO, Standard Solar

Overview

DESIGNER: Jobin Michael, senior project engineer, Standard Solar, standardsolar.com

LEAD INSTALLER: Francis Guns III, project manager, Wanex Electrical Services, wanex.com

ENERGY STORAGE INTEGRATON: SunEdison (formerly Solar Grid Storage), sunedison.com

DATE COMMISSIONED: September 2013

INSTALLATION TIME FRAME: 90 days

LOCATION: Laurel, MD, 39.1°N

SOLAR RESOURCE: 4.6 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 93°F 2% avg. high, 5°F extreme min.

ARRAY CAPACITY: 402.4 kWdc

ANNUAL AC PRODUCTION: 511,917 kWh

Equipment Specifications

MODULES: 1,364 Suniva MVX 295-72-5-701, 295 W STC, +4.99/-0 W, 8.13 Imp, 36.3 Vmp, 8.62 Isc, 44.7 Voc

INVERTERS: 3-phase 277/480 Vac service, two Princeton Power Systems (PPS) Battery-Integrated Grid-Interactive (BIGI) 250 inverters, 250 kW rated output, maximum input UL-certified to 600 Vdc, 250–580 Vdc MPPT range (the BIGI 250 has two independent dc ports [battery and PV] and one ac port); Siemens 2,000 A critical load center with load and PV breakers, and a Siemens WLS-EOSM 1,600 A islanding breaker with ETU776 trip unit

BATTERIES: AllCell Technologies integrated Sanyo URI8650FM lithium-ion cells; two 150 kWh battery enclosures, each connected to a BIGI 250 inverter; 300 kWh/500 kW storage capacity total

ARRAY: 11 modules per source circuit (3,245 W, 8.13 Imp, 399.3 Vmp, 8.62 Isc, 491.7 Voc), 124 source circuits total; three 12-source-circuit combiners and two 13-source-circuit combiners aggregated via a contactor recombiner for each inverter (201.2 kW, 504.1 Imp, 399.3 Vmp, 534.4 Isc, 491.7 Voc)

ARRAY INSTALLATION: Parking canopy structures, Solaire Generation 360 T canopies, 207° azimuth, 7° tilt

SOURCE-CIRCUIT COMBINERS: 10 SolarBOS CS200-14-15, disconnect combiners, 15 A fuses

ARRAY RECOMBINERS: Two SolarBOS RC-05-200CM-N4 contactor recombiners, 200 A fuses

SYSTEM MONITORING: Locus Energy LGate 350 PV monitoring with kiosk; advanced metering and on-site PPS controller to monitor battery and inverter system performance, provide remote maintenance and manage frequency regulation (FR) activities

EV STATIONS: Two SemaConnect ChargePro charging stations with option to add four units

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Same Sun of Vermont won the Shrewsbury Mountain School project via competitive bid. The PV system is designed to provide at least half of the small elementary school’s annual electrical usage. Given the school’s location along the spine of Vermont’s Green Mountains, the project posed some unique design challenges, including 70 psf snow loading, the need to make the system kid-proof, NEC 2014 Section 690.12 rapid-shutdown compliance and a 1-week spring break installation window.

When Same Sun inspected the roof in early spring of 2015, the crew immediately recognized the significance of the rooftop snow and ice loading. The standing seams along the two valleys were noticeably deformed downhill, and the glacier-like drift from the lower valleys to the ground was high enough to negate the need for ladder access.

To help mitigate the long-term effects of the snow, the array design keeps the modules well out of the roofs’ valleys. In addition, the installers fabricated custom snow guards from short pieces of PV rail that they mounted perpendicular to the ends of each interior module row. The guards help deflect the downward flow of snow and ice. To protect the two rooftop conduit runs, Same Sun installers let the module rails run slightly long and installed aluminum rigid conduit on top of the rails. Running the conduit in this manner not only simplified conditions-of-use conductor sizing, but also keeps the conduit a few inches above the primary flow of the snow and ice. Lastly, the installation team attached racking clamps to every seam, rather than every other or every third seam as is typical in less-challenging environments.

Same Sun specified microinverters for the Shrewsbury Mountain School project for several reasons. Module-level optimization mitigates the impact of morning shading from a tree line to the east of the array. It also reduces the impact of some very obvious variations in the amount of snow buildup and shedding on different areas of the roof. The building was short on appropriate wall space for string inverter mounting. The only available locations were far from the point of interconnection and difficult to make inaccessible to young children. Specifying micros also facilitated adherence to the relatively new 690.12 rapid-shutdown requirements. Lastly, module-level monitoring is a real boon for the teachers at the school, who are excited to incorporate information from the new solar array into their curriculum.

Physical array layout and the necessity to keep modules as far away from the roof valleys as practical primarily dictated the characteristics of each inverter output circuit (IOC). The longer 12- and 13-module IOCs have a center-fed configuration to minimize ac voltage drop. While it was not a specific requirement of the RFP, an ambitious project goal was to complete the installation during the school’s 1-week spring break in early April. The tight timeline would minimize liability and the disruption of school activities. With the added labor associated with the microinverter and trunk cable installation, unique conduit run and custom snow guards, and a bonus half-day lost to snow removal, the installers completed the system with just under a half day to spare.

“Working with schools inevitably provides a unique set of challenges, but always a very gratifying result. Shrewsbury was no exception. A very cooperative school administration, a dedicated installation crew and a 70-hour work week yielded a robust system with exceptional educational potential.”

Khanti Munro, Same Sun of Vermont

Overview

DESIGNER & PROJECT MANAGER: Khanti Munro, director of development and technical design, Same Sun of Vermont, samesunvt.com

INSTALLERS: Tyler Crow, Jon Klos, Jake Boulier, Same Sun of Vermont

DATE COMMISSIONED: April 2015

INSTALLATION TIME FRAME: 8 days

LOCATION: Shrewsbury, VT, 43.5°N

SOLAR RESOURCE: 4.3 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 84°F 2% avg. high, −20°F extreme min.

ARRAY CAPACITY: 25.2 kWdc

ANNUAL AC PRODUCTION: 30,440 kWh 

Equipment Specifications

MODULES: 90 SolarWorld Sunmodule Plus SW 280 Mono, 280 W STC, +5/-0 W, 9.07 Imp, 31.2 Vmp, 9.71 Isc, 39.5 Voc

MICROINVERTERS: 120/240 single-phase service, 90 Enphase M250, 250 W peak output power, 48 Vdc maximum input, 16–48 Vdc operating range, 27–39 Vdc MPPT range, 16 microinverters per single-phase 20 A branch circuit maximum

ARRAY: One microinverter per module, 9–13 micros per inverter output circuit (IOC), 9 A–13 A at 240 Vac per IOC, eight IOCs total combined at new dedicated ac inverter combiner panel via two-pole 20 A breakers; 25.2 kWdc array total, 90 Aac at 240 Vac

ARRAY INSTALLATION: Flush mount, standing seam roofing, IronRidge XRS-1000 rails with grounding mid-clamps, EcoFasten ASGU-2 clamps installed on every seam (approximately 20-inch spacing) to handle snow loading, 140° azimuth, 18° tilt

SYSTEM MONITORING: Enphase Envoy communications gateway hardwired to school network, Enphase Enlighten web-based monitoring

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The Washington Plaza complex provides low-income housing for residents in downtown Sacramento, California. The building’s owner contacted Deacon, a building restoration specialist, to perform a complete building remodel that included stripping the building to its core and upgrading nearly every component. The housing authority in charge of the facility strives for LEED accreditation in its remodels, and the Washington Plaza owner has facilitated remodels that incorporate PV and solar heating systems.

The primary driver of the PV design for the complex was to generate as much energy as possible from areas that were suitable for locating modules. The team determined a target energy value early in the renovation design process to meet LEED requirements.

Another key design driver was the owner’s desire to incorporate module-level monitoring. The housing authority’s previous PV installations utilize microinverters, and it was very happy with the granularity of operation and performance data that module-level power electronics systems offer.

Renewable Energy Associates (REA) generated multiple design iterations for the project, including arrays mounted on the rooftop and on covered parking structures at ground level. Given the number of rooftop units, and an elevator penthouse and stairwell on the south end of the building, the only viable option to meet the project’s energy requirements was to elevate the array above the roof. The project team designed and installed an 8-foot trellis exclusively to support the PV array. They maintained a construction-free roof zone for a solar heating system that they designed and installed separately from the PV array. The project owner ultimately opted to temporarily place the planned ground-level arrays on hold, but the design and construction teams included the infrastructure required to install these additional arrays in the future.

The project team custom-engineered the trellis structure in conjunction with the building remodel. The array support structure’s design minimizes the number of pillars attached to the building while meeting seismic and wind-loading requirements. The crew made the pillar connections below the roof deck directly to the building’s concrete support columns.

The design uses DPW Solar’s P6 Power Rail system to mount the modules to the elevated structure at a 15° tilt angle that maximizes both available space and energy production. To accommodate the owner’s requirement for a high-efficiency array with module-level monitoring, REA specified SunPower modules, Tigo maximizers and SMA inverters. Module-level dc optimization allowed for module placement in less-than-ideal rooftop locations while minimizing potential energy losses.

The original main distribution switchgear, which remained in place, and the metering arrangement somewhat complicated the utility point of interconnection. The original main distribution panel includes a main disconnect for the entire service, metering for the common area loads and feeders for meter centers located on each floor of the building, which provide individual apartment metering. To properly net-meter the PV system, installers had to make the point of common coupling on the line side of the common area distribution panel. The electrical installation includes provisions for future solar inputs from the ground-level arrays via additional spaces in the dedicated inverter aggregation panelboard.

“The Washington Plaza building presented a number of challenges, from design through construction, but the team members always found the best solutions to overcome these challenges. Working with the solar team to meet our energy generation target was a fun process for all of us that resulted in a great PV installation.”

Jeremy Dietz, business development manager, Deacon

Overview

CONTRACTOR: Deacon, remcodeacon.com

DESIGNER: John Stimac, system designer, Renewable Energy Associates, renewableassociates.com

LEAD INSTALLER: Matt Evans, operations manager, Barnum & Celillo Electric, barnumcelillo.com

DATE COMMISSIONED: December 2014

INSTALLATION TIME FRAME: 90 days

LOCATION: Sacramento, CA, 38°N

SOLAR RESOURCE: 5.5 kWh/m2/day

ASHRAE DESIGN TEMPERATURES:  99°F 2% avg. high, 27°F extreme min.

ARRAY CAPACITY: 42.8 kWdc

ANNUAL AC PRODUCTION: 56,400 kWh

Equipment Specifications

MODULES: 124 SunPower X21-345, 345 W STC, +5/-0%, 6.02 Imp, 57.3 Vmp, 6.39 Isc, 68.2 Voc

INVERTERS: 3-phase 120/208 Vac service, three SMA America Sunny Boy SB10000TL-US (10 kW, 600 Vdc maximum input, 300–480 Vdc MPPT range), one SMA America Sunny Boy SB7000TL-US (7 kW, 600 Vdc maximum input, 300–480 Vdc MPPT range), four SMA America Sunny Boy Combiner Box TLUS-SBCBTL6, 15 A fuses

ARRAY: Seven modules per source circuit typical (2,415 W, 6.02 Imp, 401.1 Vmp, 6.39 Isc, 477.4 Voc), five source circuits per inverter typical (12,075 W, 30.1 Imp, 401.1 Vmp, 31.95 Isc, 477.4 Voc), one Tigo Energy Dual Maximizer MM-2ES75 per two modules typical, 42.8 kWdc array capacity total

ARRAY INSTALLATION: Custom elevated steel I-beam structure, DPW Solar P6 Power Rail, 199° azimuth, 15° tilt

SYSTEM MONITORING: Tigo Gateway and Maximizer Management Unit

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Panasonic Eco Solutions partners with Coronal Group to deliver comprehensive solutions for the development, engineering, financing, construction and long-term O&M of PV projects in the commercial, industrial, municipal and small utility markets. The Panasonic-Coronal partnership has developed nine projects in California under its 16.2 MW Central Valley portfolio, including the 3.6 MWdc Hanford PV plant. ImMODO Energy Services and Panasonic built the projects, which have PPAs with Southern California Edison as part of its CREST Feed-In Tariff Program.

Panasonic-Coronal had to consider many elements throughout the various stages of the Hanford development. The generation facility required a conditional use permit (CUP), as is the case for most PV projects in California that export power directly to the grid. The CUP approval process involved extensive archaeological, environmental, biological and wildlife studies that took approximately eight months. In addition, the project required an SCE Rule 21 interconnection approval, a process that took roughly four months.

Once the plan met the appropriate requirements, construction began. Hydraulic equipment drove the foundation piles for the fixed mounting system, eliminating the need for drilling and concrete. The system’s two 1,000 Vdc Eaton Power Xpert Solar inverters and 1,000 Vdc BOS components allowed for high design voltages and reduced the project’s first cost. To ensure the success of this installation, Panasonic is providing comprehensive, ongoing O&M services and a long-term production guarantee.

“Significant solar projects are beneficial to the economy and how we produce and consume energy, but their financial and structural complexities are a big challenge for companies interested in adopting clean, sustainable energy. The Panasonic-Coronal platform is a proven integrated business model that removes those obstacles and helps to deliver affordable, reliable, clean energy.”

Jamie Evans, managing director, Panasonic Eco Solutions

Overview

DEVELOPERS: Panasonic Eco Solutions, panasonic.com/business/pesna; Coronal Group, coronalgroup.com; ImMODO Energy Services, immodoenergy.com

ENGINEERING & CONSTRUCTION: ImMODO Energy Services; Panasonic Eco Solutions

DATE COMMISSIONED: August 2014

INSTALLATION TIME FRAME: 60 days

LOCATION: Hanford, California, 36.3°N

SOLAR RESOURCE: 5.7 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 102°F 2% avg. high, 27°F extreme min.

ARRAY CAPACITY: 3.6 MWdc

ANNUAL AC PRODUCTION: 6,324 MWh

Equipment Specifications

MODULES: 11,800 Jinko JKM305P, 305 W STC, +5/-0%, 8.16 Imp, 37.4 Vmp, 9.05 Isc, 45.6 Voc

INVERTERS: 3-phase 12 kV medium-voltage interconnection; two Eaton Power Xpert Solar 1500 kW, 1,500 kW rated output, 1,000 Vdc maximum input, 550–1,000 Vdc MPPT range

ARRAY: 20 modules per source circuit (6,100 W, 8.16 Imp, 748 Vmp, 9.05 Isc, 912 Voc), two source circuits paralleled in array field (12.2 kW, 16.32 Imp, 748 Vmp, 18.1 Isc, 912 Voc), 10–12 input circuits per combiner, 13 combiners per inverter

ARRAY COMBINERS: 26 Shoals disconnecting combiners

ARRAY INSTALLATION: Custom fixed ground mount designed and manufactured by ImMODO Energy Services, two-module columns in portrait orientation, 180° azimuth, 20° tilt

SYSTEM MONITORING: ImMODO Energy Services monitoring system

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California’s 52-year-old Soiland Company produces rock, soil and compost products at three locations in Sonoma County, California, and is the North Bay’s largest recycler of rubble materials. When its electric bills nearly tripled overnight due to a new PG&E rate structure, the company enlisted local installer North Coast Solar and Vermont-based dual-axis tracker manufacturer AllEarth Renewables to design and develop a 202 kWdc tracker farm at its Stony Point Rock Quarry. The system has reduced Soiland’s electricity bills by more than 50 percent and is projected to offset initial equipment and construction costs in approximately 7 years.

The project partners overcame many technical challenges, including the need to run ac transmission lines up the face of the rock quarry and expansive soils that required the structural engineers to ignore the top 3 feet in their calculations. The pour-in-place foundations for the 33 AllEarth Solar Trackers required 30-inch–diameter, 13-foot-deep piers that are installed on a hillside behind the quarry. The trackers are fully pre-engineered, palletized and shipped directly from AllEarth. Installers used a jig to speed the assembly of tracker frames and a telescopic forklift to mount the tracker frames on the mast assemblies.

The site’s original single service was on the PG&E E19 rate schedule and subject to very high demand charges. To optimize project economics, the designers added a second service and developed two separate PV systems. Two services reduced demand below 500 kW and qualified the two smaller services for a solar-friendly bundled PG&E A6 time-of-use rate schedule that varies the kWh rate based on time of day and season.

System A serves the quarry’s wet plant and HP400 rock crusher. It is interconnected at the new service and aggregates ac power from 15 Series 24 AllEarth Solar Trackers. System B interconnects the output of 18 Series 24 units at the reconfigured existing service and supplies power to the quarry’s main plant. Each system has a separate 200 A 480 Vac subpanel. Installers used power poles to route separate 480 V lines down the face of the quarry, where they interconnect at the site’s main service panel.

Stony Point Rock Quarry’s 202 kWdc array generated an impressive 439,000 ac kWh in its first year due to the Series 24 AllEarth Solar Trackers’ GPS-based dual-axis tracking. In addition, the project’s decentralized inverter design eliminates the possibility of a single point of failure in the power conditioning system. It will also reduce future O&M costs.

“As part of this project, we installed two electric services that qualified the quarry for a rate schedule that did not include demand charges, just a bundled kWh charge. The result is a much more solar-friendly rate schedule that made the project economically feasible.”

— Brian Hines, North Coast Solar

“The decision to go solar not only made economic sense, but really aligned with Soiland’s values. Since the company’s inception, we have always strived to be sustainable and environmentally responsible.”

—Mark Soiland, owner, Soiland Company

Overview

DESIGNER: Brian Hines, president, North Coast Solar, ncsr.com

LEAD INSTALLER: Steve Balich, field superintendent, Lunardi Electric, lunardielectric.com

DATE COMMISSIONED: February 1, 2014

INSTALLATION TIME FRAME: 90 days

LOCATION: Cotati, CA, 38.3°N

SOLAR RESOURCE: 5.5 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 93°F 2% avg. high, 27 °F extreme min.

ARRAY CAPACITY: 202 kWdc

ANNUAL AC PRODUCTION: 439,000 kWh

Equipment Specifications

MODULES: 792 ReneSola JC255M-24/Bb, 255 W STC, +5/-0 W, 8.39 Imp, 30.4 Vmp, 8.86 Isc, 37.5 Voc

INVERTERS: 3-phase 277/480 Vac service; 33 SMA America Sunny Boy 6000-US, 6 kW rated output, 600 Vdc maximum input, 250–480 Vdc MPPT range

ARRAY: 12 modules per source circuit (3,060 W, 8.39 Imp, 364.8 Vmp, 8.86 Isc, 450 Voc), two source circuits per inverter (6,120 W, 16.78 Imp, 364.8 Vmp, 17.72 Isc, 450 Voc), 202 kWdc array total

TRACKERS: 33 Series 24 AllEarth Solar Trackers, dual-axis GPS-based array tracking; system includes one mast-mounted SMA America Sunny Boy 6000-US inverter and two-circuit ac load center (for inverter and tracker controller/motor) per tracker

SYSTEM MONITORING: DECK monitoring with CEC-approved revenue grade metering, AllEarth Renewables remote monitoring

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In the summer of 2014, the Puffer family contracted Sunlight Solar Energy to install a 12.9 kW PV system on their residence in Framingham, Massachusetts. To meet the owners’ desire to maximize the overall array size, the company mounted modules in landscape orientation on the house and garage rooftops. Module-level dc optimizers provide design flexibility and optimize energy production.

Since the array size is in excess of 10 kW, Sunlight Solar had to take a number of additional steps and make special considerations during the project’s design phase, including obtaining special interconnection and AHJ plan review approval, and coordinating all the requirements with the homeowners.

One of the most important considerations for this installation was meeting the 2014 NEC 690.12 requirements. Sunlight Solar has installed a number of SolarEdge systems for its Massachusetts customers, with general acceptance by the various AHJs. For the Puffer system, the AHJ required additional documentation and consultation from the manufacturer.

The overall power rating of the system required a line-side point of interconnection. The main distribution panel (MDP) was already full of conductors and OCPDs, so connecting to the service conductors inside that panel was not an option. Sunlight Solar provided a connection box located between the meter and the MDP. Installers rerouted the service conductors from the meter, through the new connection box and then to the MDP. This required a service shutdown to allow the electricians to make the interconnection safely.

“For all our Massachusetts projects, meeting NEC 690.12 is a starting point in our designs. The first half of 2014 was difficult, but now we have developed a clean process to meet the AHJ requirements. The Puffer job was a good example of where doing our homework up front made the whole process much smoother.”

—Brandon Stephens, director of MA operations, Sunlight Solar Energy

Overview

DESIGNER: Brian Brady, regional sales manager, Sunlight Solar Energy, sunlightsolar.com

LEAD INSTALLER: Mike Logan, lead installer, Sunlight Solar Energy

DATE COMMISSIONED: July 2014

INSTALLATION TIME FRAME: 5 days

LOCATION: Framingham, MA, 42°N

SOLAR RESOURCE: 3.7 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 90°F 2% avg. high, -4°F extreme min.

ARRAY CAPACITY:12.9 kWdc 

ANNUAL AC PRODUCTION:13,200 kWh

Equipment Specifications

MODULES: 47 SolarWorld Sunmodule Plus SW 275 Mono Black, 275 W STC, +5/-0 W, 8.94 Imp, 31 Vmp, 9.58 Isc, 39.4 Voc

INVERTERS: 120/240 Vac single-phase service; one SolarEdge 10000A-US, 10 kW, 500 Vdc maximum input, 350 Vdc nominal input; one SolarEdge 3000A-US, 3 kW, 500 Vdc maximum input, 350 Vdc nominal input; 47 SolarEdge P300 Power Optimizers, 300 W, 48 Vdc maximum input, 8–48 Vdc MPPT range

ARRAY: Three source circuits: one 18 module (4,950 W, 350 Vdc nominal), one 17 module (4,675 W, 350 Vdc nominal) and one 12 module (3,300 W, 350 Vdc nominal)

ARRAY INSTALLATION: Asphalt shingle roofing, SnapNrack Series 100 racking, 235° azimuth, 40° tilt

SYSTEM MONITORING: SolarEdge monitoring with Locus Energy auto reporter

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