Project Profiles

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A landmark project for the East Coast and North Carolina, the 29.7 MWdc HXOap Solar Farm is built on the site of the decommissioned Halifax County Airport. At the time of commissioning, the project is the largest PV system in North Carolina, one of the largest on the East Coast and the single largest string inverter system in the western hemisphere. The project’s decentralized architecture features 866 Advanced Energy 3-phase 1,000 Vdc non-isolated string inverters.

Geenex, a Charlotte, North Carolina–based solar developer, and ET Capital, a California-based energy investment company and subsidiary of ET Solar Group, developed the HXOap Solar Farm in partnership. Alpha Energy, a member of the Alpha Group, provided engineering consultation and construction. Upon completion, Duke Energy will acquire the project and sell the energy generated to Dominion over the 15-year PPA. The project created more than 150 jobs during peak construction and will inject an estimated $75 million into the economically challenged Halifax County between 2014 and 2029.

The system uses RBI Solar’s fixed-tilt GM-I mounting system in conjunction with driven-post foundations to mount 98,724 ET Solar modules in two-module-high portrait orientation at an azimuth of 180° and a 20° tilt. The power conditioning system employs 866 23.2 kWac Advanced Energy AE 3TL string inverters. A standardized array layout connects each inverter to subarrays consisting of 19 modules per source circuit with six strings per inverter. The placement of each inverter, ac panel and transformer pad creates a consistent and optimized design. Each of the 149 ac panels aggregates the output of either five or six string inverters. The design distributes inverters, switchgear and transformers strategically throughout the array field. The overall dc and ac ohmic losses for the system are 0.23% and 2.39%, respectively.

The 20 MWac power conversion system is organized into 10 blocks total, with seven blocks dedicated to a 15 MWac collection system and three blocks dedicated to a 5 MWac collection system. The 15 MWac collection section consists of seven pads —each with one 2 MVA 34.5 kV Cooper transformer and two Eaton switchboards—and interconnects at a 34.5 kV medium-voltage connection. This interconnection point is located at the southernmost section of the 15 MWac subarray. The 5 MWac collection system  utilizes three pads, of which two have one 13.2 kV 2 MVA Cooper transformer and two Eaton switchboards; the remaining pad has one 13.2 kV 700 kVA Cooper transformer and a single Eaton switchboard. Both the 34.5 kV interconnection point and the 13.2 kV interconnection point lead to Dominion’s Homertown substation.

“Alpha Energy is proud to be the first EPC in the US to construct a string-level distribution system of this magnitude. Watching 866 Advanced Energy inverters communicating on our network is impressive.”

Ronnie Andrawis, Alpha Energy

“This AE 3TL project is a great example of the inflection point in the market towards 3-phase string technology.”

Bates Marshall, VP of Global Sales and Marketing, Advanced Energy

Overview

DEVELOPERS: ET Capital, etcapital.us; Geenex, geenexsolar.com

DESIGNERS: Mike Doman, engineering consultant, Alpha Energy, alpha.com/solar; Dominic Lopez, senior project manager and system engineer, ET Capital

LEAD INSTALLER: Ronnie Andrawis, senior project manager, Alpha Energy

DATE COMMISSIONED: December 2014

INSTALLATION TIME FRAME: 130 days

LOCATION: Roanoke Rapids, NC, 36.5°N

SOLAR RESOURCE: 5 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 93°F 2% avg. high, 10°F extreme min.

ARRAY CAPACITY: 29.7 MWdc

ANNUAL AC PRODUCTION: 44,001 MWh

Equipment Specifications

MODULES: 98,724 modules total; 81,738 ET-P672300, 300 W STC, +5/-0 W, 8.18 Imp, 36.68 Vmp, 8.72 Isc, 44.89 Voc; 16,986 ET-P672305, 305 W STC, +5/-0 W, 8.21 Imp, 37.18 Vmp, 8.78 Isc, 45.12 Voc

INVERTERS: 866 Advanced Energy AE 3TL-23, 23.2 kW, 1,000 Vdc maximum input, 250–900 Vdc MPPT range, non-isolated 3-phase 480 Vac nominal output, 98% CEC efficiency; 13.2 kV and 35.4 kV medium-voltage interconnections

ARRAY: Nineteen modules per source circuit (for ET-P672300: 5,700 W, 8.18 Imp, 696.9 Vmp, 8.72 Isc, 852.9 Voc), six strings per inverter (for ET-P672300: 34.2 kW, 49.08 Imp, 696.9 Vmp, 52.32 Isc, 852.9 Voc), 866 inverters total, 29.7 MWdc array capacity total, 1.5 dc-to-ac ratio

ARRAY INSTALLATION: Fixed-tilt ground mount, driven posts, RBI Solar GM-I mounting system, 180° azimuth, 20° tilt

SYSTEM MONITORING: Cisco Switches with AlsoEnergy monitoring hardware and software

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The Canada-France-Hawaii (CFH) Telescope hosts a world-class optical and infrared telescope on the summit of Mauna Kea on the island of Hawaii. The observatory headquarters is located in the town of Waimea, in the shadow of Mauna Kea. The CFH board of trustees contracted Renewable Energy Services (RES) to install a large PV system to help reduce its headquarter’s energy costs. The CFH board of directors, composed of members appointed from the Canadian, French and Hawaiian member organizations, was instrumental in the approval and implementation of the PV system.

The design process took an extended period of time because HELCO, the local utility, had regionally specific interconnection requirements. Net-metering rules limited the PV system capacity to less than 100 kW per service. Interconnection approval requires a three-line drawing and an interconnection study. This process has become critical for projects on the islands, as the utility considers many of its feeders saturated with renewable generation. Local integrators must take a diligent approach, as they need to produce accurate initial designs but limit their design time to minimize financial exposure.

For the CFH Telescope project, RES based the electrical design on Enphase Energy inverters from the outset. The goal of making the array as large as possible given the available space drove this product specification. Due to multiple roof orientations and lack of accessible space to mount string inverters, microinverters proved to be the most practical solution. The minimal roof slopes and subtropical location allowed RES to utilize most of the roof surfaces, including those facing northwest and northeast, without sacrificing too much energy production.

While using microinverters essentially eliminated the dc side of the system design, aggregating the ac conductors required a fair amount of planning. To help with the installation process, RES completed detailed electrical schematics. Using center-fed branch circuits as the primary method for rooftop wiring minimized voltage drop on the ac conductors. This method kept the current levels within the trunk cables to a minimum. RES installed all the ac aggregation panels at ground level, close to the utility interconnection location.

RES installed the PV system on two buildings, each with a dedicated meter from the utility’s service entrance. This required two separate points of interconnection, even though both POI ultimately connected to the same service. The smaller system on the shop building interconnected on the load side of that building’s service disconnect, while RES installed the larger building’s array as a line-side connection within the main service panel for that building. To meet the AHJ’s requirements for the line-side connection, RES relocated one of the panelboard’s main disconnects, opening up a space within the main service gear for the interconnection.

“Working with the CFH Telescope team was exciting for us. The attention to detail from all of the team members helped make for a smooth installation. This was especially true given the more complex nature of having two points of interconnection.”

Roland Shackelford, Renewable Energy Services

Overview

DESIGNER: Peter Shackelford, president, Renewable Energy Services, renewablenergy.com

LEAD INSTALLER: Roland Shackelford, vice president, Renewable Energy Services

DATE COMMISSIONED: December 2013

INSTALLATION TIME FRAME: 21 days

LOCATION: Kamuela, HI, 20°N

SOLAR RESOURCE: 4.7 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 86°F 2% avg. high, 57°F extreme min.

ARRAY CAPACITY: 121 kWdc

ANNUAL AC PRODUCTION: 150,000 kWh

Equipment Specifications

MODULES: 561 LG Solar LG260S1C-G3, 260 W STC, +3/-0%, 8.61 Imp, 30.2 Vmp, 9.2 Isc, 37.9 Voc

INVERTERS: 3-phase 120/208 Vac service, 561 Enphase Energy M215-60-2LL-S22-NA, 215 W rated output, 45 Vdc maximum input, 22–36 Vdc MPPT range, 208 Vac output

ARRAY: 18–24 inverters per branch circuit (typical), center-fed branch-circuit configuration, 24 branch circuits total connected to separate panelboards on two separate buildings

ARRAY INSTALLATION: Standing seam metal roofing, S-5! Clamps and VersaBrackets, ProSolar rails, multiple roof surfaces with 40°, 130°, 180°, 220° and 310° azimuths, 5° tilt

SYSTEM MONITORING: Enphase Energy Envoy communications gateway and Enlighten monitoring platform

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Century Villages at Cabrillo (CVC) is a residential community established in 1997 to provide transitional and permanent housing to the homeless and those at risk of becoming homeless. Since that time, CVC has evolved into a unique public-private partnership that provides housing to more than 1,000 persons, including veterans, individuals, families and children.

The 26-acre campus is located at a former US Naval housing site. Independent Energy Solutions (IES) constructed a 99.9 kWdc solar carport, a project initially complicated by the lack of accurate as-built drawings of the site’s utilities. Additional complications included a very shallow water table. To overcome this site limitation, IES selected Schletter’s Park@Sol carport system, which a shallow-spread structural footing design can support.

During excavation, the installation crew discovered a large storm drain and unidentified cast-iron pipes cutting through the footing locations. These discoveries presented a few problems to overcome, making it necessary to re-engineer the footing design to protect the pipes. IES worked with Schletter’s engineering team to reconfigure the footing load calculations for larger-spread footings that accounted for pipes within the footings. Attaining AHJ approval of the revised structural design delayed the project a few weeks.

“After we got through the preliminary hurdles, the Schletter carport system was quick and straightforward to install. Assembly took only one day per array. The module clamping system requires no drilling and is very easy to install. The main girder beams have grooves on top that allow array wiring to be nearly invisible.”

Tuan Nguyen, Independent Energy Solutions

Overview

DESIGNER: Derwin Russell, engineer, Independent Energy Solutions (IES), indenergysolutions.com

LEAD INSTALLER: Tuan Nguyen, general foreman, IES

DATE COMMISSIONED: October 2014

INSTALLATION TIME FRAME: 4 weeks

LOCATION: Long Beach, CA, 33.8°N

SOLAR RESOURCE: 5.6 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 86°F 2% avg. high, 35°F extreme min.

ARRAY CAPACITY: 99.9 kWdc

ANNUAL AC PRODUCTION: 132,788 kWh

Equipment Specifications

MODULES: 370 SolarWorld Sunmodule SW 270 mono, 270 W STC, +5/-0 W, 8.42 Imp, 32.1 Vmp, 8.9 Isc, 38.3 Voc

INVERTERS: 3-phase 120/208 Vac service, seven Fronius IG Plus Advanced 11.4-3 Delta (11.4 kW, 600 Vdc maximum input, 230–500 Vdc MPPT range), one Fronius IG Plus Advanced 10.0-3 Delta (9,995 W, 600 Vdc maximum input, 230–500 Vdc MPPT range); inverters aggregated at 400 A panel board

ARRAY: Five subarrays with 12-module source circuits (3,240 W, 8.42 Imp, 385.2 Vmp, 8.9 Isc, 459.6 Voc), four source circuits per subarray (12,960 W, 33.68 Imp, 385.2 Vmp, 35.6 Isc, 459.6 Voc); one subarray with 10-module source circuits (2,700 W, 8.42 Imp, 321 Vmp, 8.9 Isc, 383 Voc), four source circuits (10,800 W, 33.68 Imp, 321 Vmp, 35.6 Isc, 383 Voc); two subarrays with nine-module source circuits (2,430 W, 8.42 Imp, 288.9 Vmp, 8.9 Isc, 344.7 Voc), five source circuits per subarray (12,150 W, 42.1 Imp, 288.9 Vmp, 44.5 Isc, 344.7 Voc); 99.9 kW array capacity total

ARRAY INSTALLATION: Two Schletter Park@Sol carports, B2 two-row vehicle arrangement, cast-in-place foundations, 180° azimuth, 5° tilt; each carport supports five rows of 37 modules

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Fairview Farms in Whately, Massachusetts, is a 100-acre multi-generational family farm with large greenhouse complexes and planted fields. The farm’s owners met a Nexamp developer at a solar project ribbon-cutting at a local farmers’ co-op and became interested in leasing a portion of their underutilized land to host a solar project. Nexamp completed the 2.4 MW PV installation in June 2014.

Because Massachusetts allows off-site net metering, the nearby University of Massachusetts, Amherst, is able to purchase all net metering credits that the Nexamp installations at Fairview Farms and another local farm produce. These two projects are expected to save the university approximately $1.5 million over the first 20 years of operation.

For Fairview Farms, the solar land-lease agreement was an ideal solution for a plot of extremely granular farmland that required significant irrigation and fertilization for agricultural use, which would have been expensive and damaging to the environment. The ground-mounted PV project brings positive environmental impacts and ensures a steady income to even out the seasonable variability of farming.

Nexamp worked with Solectria Renewables and RBI Solar to develop the project design. RBI Solar assisted in the soil analysis to determine the specifications for the racking system’s driven piles to address the site’s 65 psf snow loading and 100 mph wind speed characteristics.

The designers specified Solectria 500 kW inverters with integrated dc breakers to satisfy local code requirements for circuit protection and interruption. Two inverters are located in the southeast area of the site on a single concrete slab. These inverters feed to the north, where two additional inverters and new service conductors are located. Installers connected all four inverters to a 480 V 2,400 A panelboard at the main service entrance. A Draker SCADA unit communicates with the inverters and a switchgear-mounted production meter to aggregate site data.

The main switchgear connects to a single 2,000 kVA pad-mounted transformer, stepping the voltage up to the 13.8 kV utility voltage via a grounded wye / grounded wye configuration. This connects to the 3-phase power lines at the street, interrupted by a pole-mounted Cooper Form 6 self-contained recloser for site backup protection and a 15 kV gang-operated ac disconnect. Nexamp coordinated the specification and installation of all medium-voltage components with the local utility.

Although construction began during one of the most severe Massachusetts winters in recent history, Nexamp, a New England–based developer, had the deep expertise necessary to apply best practices for winter installations. In addition to performing regular snow removal to limit winter safety hazards as well as potential hazards resulting from muddy thaws, the team ensured that installers appropriately distributed materials across the 10-acre work area. The project’s site supervisor and the project manager provided close oversight to reinforce safety standards, preventing slips and frostbite as the construction teams erected much of the arrays by hand.

“What makes this project special is the way it offers so many benefits to so many parties. In addition to bringing clean energy to the community, it will provide a consistent source of supplemental income for the family farm that hosts the array, while also offering substantial energy savings for the University of Massachusetts, Amherst. It’s a great example of the multifaceted benefits solar has to offer.”

—Zaid Ashai, CEO, Nexamp

Overview

DESIGN & INSTALLATION FIRM: Nexamp, nexamp.com

DATE COMMISSIONED: June 2014

INSTALLATION TIME FRAME: 75 days

LOCATION: Whately, MA, 42.5°N

SOLAR RESOURCE: 3.6 kWh/m2/day

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

ARRAY CAPACITY: 2.385 MWdc

ANNUAL AC PRODUCTION: 3,015 MWh

Equipment Specifications

MODULES: 7,821 BYD 305P6C-36, 305 W STC, +5/-0 W, 8.43 Imp, 36.18 Vmp, 8.91 Isc, 45.49 Voc

INVERTERS: 3-phase 13.8 kV medium voltage interconnection; four Solectria SGI 500PE, 500 kW, 600 Vdc maximum input, 300–500 Vdc MPPT range; 2,000 kVA 480 Vac–to–13.8 kV pad-mounted transformer

ARRAY: Four subarrays, 11 modules per source circuit (3,355 W, 8.43 Imp, 398 Vmp, 8.91 Isc, 500.4 Voc); 10–14 source circuits per combiner, 10 typical (33.55 kW, 84.3 Imp, 398 Vmp, 89.1 Isc, 500.4 Voc); 16 combiners per inverter; 2.385 MWdc array capacity total

ARRAY INSTALLATION: Fixed ground mount, RBI Solar Ground Mount racking, 180° azimuth, 20° tilt

SOURCE-CIRCUIT COMBINERS: 64 TEAL Electronics TEALsolar Configurable Combiner Box, 15 A fuses

SYSTEM MONITORING: Draker Intelligent Array software with a DBS 4X central data acquisition unit, cellular modem kit, environmental monitoring and Shark 100 energy meter

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Sierra Nevada Brewing Company is well known for its commitment to preserving the environment and its sustainability initiatives for manufacturing its ales and lagers.  Its Chico, California, brewery is home to one of the largest privately owned PV arrays in the country. When it made the decision to expand to a new East Coast location in Mills River, North Carolina, Sierra Nevada intended to make the new facility as sustainable as possible, with features including a solar component to offset a substantial portion of the site’s electrical usage.

North Carolina has a 1 MWac cap per customer on net-metered systems. This limitation dictated the size of the systems designed for the brewery.  With two planned 200 kW turbine generators, fueled with methane produced from spent grains and wastewater treatment on-site, the total solar inverter capacity had a calculated target of 600 kWac.

The system included nine parking lot canopies with a total capacity of 60 kWdc, custom designed to create shaded parking during the day and provide lighting at night from fixtures integrated on the underside of the canopies. Wire management within the canopy structures posed an installation challenge. Due to aesthetic requirements, the design concealed all of the dc source circuits and ac lighting circuits within the canopies’ structural members, which required fabrication of the structures with internal wiring partitions to keep the ac and dc wires separated throughout. Additionally, aesthetic elements of the canopy design resulted in minimal array shading during certain times of the day. However, the canopies represent a small portion of the total array capacity on-site and create a striking effect for the brewery’s visitors.

The Sundance Power Systems team installed the 650 kWdc rooftop array over nearly two acres of the packing warehouse’s roof. The precast concrete roof provided an ideal surface for laying out Daetwyler’s Eco-Top Rooftop Mounting Structures. Sundance selected the Eco-Top product in part because Daetwyler manufactures it in North Carolina, so it qualifies for local materials credit in LEED certification, an option that Sierra Nevada will be pursuing.

The canopy and rooftop systems interconnect at separate locations on-site. The rooftop system’s 250 kW and 300 kW Solectria inverters are located on the opposite side of the cold storage warehouse from the canopy arrays. The rooftop system’s point of delivery is located at the 480 Vac switchgear on the load side of the MV transformer that feeds the warehouse section of Sierra Nevada’s site grid. The canopy array’s 50 kW inverter interconnects at a 480 Vac subpanel located adjacent to the keg line.

“Delays challenged this installation, including product availability issues, record rainfall for the season and working with custom canopy structures.  However, Sierra Nevada’s familiarity with PV from past installations and its commitment to quality craftsmanship throughout this project were hugely instrumental in the success of the design and installation.”

—Drew Cates, Sundance Power Systems

Overview

DESIGNER: Drew Cates, design and estimate coordinator, Sundance Power Systems, sundancepower.com

PROJECT MANAGER: Grayson Newell, director of field development, Sundance Power Systems

ENGINEER: Dale Reynolds, PE, senior electrical engineer, McKim & Creed, mckimcreed.com

DATE COMMISSIONED: January 19, 2014

INSTALLATION TIME FRAME: 120 days

LOCATION: Mills River, NC, 35.4°N

SOLAR RESOURCE: 4.3 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 88°F 0.2% avg. high, 5°F extreme min.

ARRAY CAPACITY: 710 kWdc

ANNUAL AC PRODUCTION: 903 MWh

Equipment Specifications

MODULES, ROOFTOP: 2,030 Kyocera KD320GX, 320 W STC, +5%/-0%, 7.99 Imp, 40.1 Vmp, 8.6 Isc, 49.5 Voc

MODULES, CANOPIES: 198 Suniva OPT305-72-4-100, 305 W STC, +5/-0 W, 8.45 Imp, 36.1 Vmp, 9 Isc, 45.6 Voc  

INVERTERS: 3-phase 277/480 Vac service, one Solectria PVI 50KW (50 kW, 600 Vdc maximum input, 300–500 Vdc MPPT range), one Solectria SGI 250 (250 kW, 600 Vdc maximum input, 300–500 Vdc MPPT range), one Solectria SGI 300 (300 kW, 600 Vdc maximum input, 300–500 Vdc MPPT range)

ARRAY, ROOFTOP: 10 modules per source circuit (3,200 W, 7.99 Imp, 401 Vmp, 8.6 Isc, 495 Voc), 16–24 source circuits per combiner, 4–6 combiners per inverter, 649.6 kW array total

ARRAY, CANOPIES:  11 modules per source circuit (3,355 W, 8.45 Imp, 397.1 Vmp, 9 Isc, 501.6 Voc), 18 source circuits total (60.39 kW, 152.1 Imp, 397.1 Vmp, 162 Isc, 501.6 Voc), 60.4 kW array total

ARRAY INSTALLATION, ROOFTOP: Ballasted low-slope roof mount, membrane roofing, Daetwyler CE Eco-Top Gen2 Rooftop Mounting Structures, 141° azimuth, 10° tilt

ARRAY INSTALLATION, CANOPIES: Custom-fabricated canopy structures, 141° azimuth, 20° tilt

SOURCE-CIRCUIT COMBINERS: 11 SolarBOS Disconnect Combiners, 15 A fuses

SYSTEM MONITORING: String-level DECK monitoring with weather station

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When the Meisterlings were considering a PV system for their residence, they were interested in a high-performance system that did not adversely affect their home’s aesthetics. Moxie Solar took into account the building’s architectural features, including the roof system’s multiple surfaces, and worked with the clients to deliver a system that balanced form and function.

Due to local rebate requirements, module-level dc optimization offered a better return on investment than microinverters for the Meisterling project. The final design includes frameless Lumos LSX 250 Series modules, selected for their aesthetics, paired with SolarEdge’s module-level dc optimizers and string inverter to maximize the system’s production.

The installation required special attention to the conduit runs from the subarrays to the inverter. Each subarray has a junction box installed adjacent to the modules with conduit penetrating the roof surface to conceal the conduit runs. The inverter is located in the basement adjacent to the existing service entrance, which allows a straightforward interconnection and keeps the electrical equipment co-located. This location also allows easy integration of the inverter’s communications with the homeowner’s existing router.

“The final piece of the rooftop puzzle addressed a concern the homeowners and Moxie Solar shared. The house is located in a heavily wooded area with large populations of birds, squirrels and other critters. To protect the array wiring from damage, we installed a black SnapNrack Edge Screen Protector to prevent any issues stemming from nesting birds or other wildlife activity or debris.”

—Jason Hall, CEO, Moxie Solar

Overview

DESIGNER: Kyle Troutman, Moxie Solar, moxiesolar.com

LEAD INSTALLER: Tim Brodersen, operations manager, Moxie Solar

DATE COMMISSIONED: July 2014

INSTALLATION TIME FRAME: 6 days

LOCATION: Cedar Rapids, Iowa, 41°N

SOLAR RESOURCE: 4.6 kWh/m2/day

ASHRAE DESIGN TEMPERATURES: 91°F 2% avg. high, -15°F extreme min.

ARRAY CAPACITY: 6.6 kWdc

ANNUAL AC PRODUCTION: 9,012 kWh

Equipment Specifications

MODULES: 27 Lumos LSX 250 Series LSX245-60M-B, 245 W STC, +3/-0%, 8.17 Imp, 30 Vmp, 8.69 Isc, 37.2 Voc

INVERTER: Single-phase 120/240 Vac service, SolarEdge SE6000A-US, 6 kWac, 500 Vdc maximum input, 350 Vdc nominal input (fixed and controlled by inverter); 27 SolarEdge P300 power optimizers, 300 W, 48 Vdc maximum input, 8–48 Vdc MPPT range

ARRAY: Two source circuits, 13 modules (3,185 W) and 14 modules (3,430 W), module-level current output controlled by power optimizers (15 Imp maximum); 6.6 kWdc array total at 350 Vdc nominal

ARRAY INSTALLATION: Flush-to-roof mount, Lumos LSX mounting system, 180° azimuth, 28° tilt

SYSTEM MONITORING: SolarEdge Module-Level Monitoring, SolarEdge Monitoring Portal

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Green Mountain Power (GMP), the Solar Electric Power Association’s Utility of the Year for 2013, provides electricity to more than 250,000 customers in Vermont. Positive Energy NY installed a rooftop PV array on the utility’s equipment maintenance building in Rutland, Vermont. The facility is in an industrial area of the city and houses an internal lifting crane for heavy transformer maintenance as well as a 12 MW peaking diesel generator that operates primarily during high-demand periods.

The RFP clearly stated the utility’s objective for the project: “GMP’s goal is to install the highest-kilowatt system possible on the roof while effectively balancing life cycle costs.” The site has several available roof surfaces that Positive Energy NY assessed for solar access, structural integrity and the feasibility of developing a fire code–compliant array layout. Positive Energy NY determined that the main building rooftop was the only site suitable for a PV array. However, the company was concerned about excessive point loading of the roof deck and requested further structural analysis. SunLink’s fully ballasted Precision RMS racking system met the site’s structural requirements and offered flexibility for the array layout. During the project’s design and installation phases, the team gave special attention to the racking supports to ensure that they ran parallel to, and directly above, the building’s steel purlins, which are spaced approximately 9 feet apart.

The ten-module source circuits fit perfectly on the roof and allow for a fire code–compliant 4-foot-wide walkway between all sides of the array and the building’s roof edge or parapet. The crew was also able to install the source circuits efficiently since they could avoid jumping rows within strings. They installed three SMA Connection Units within the array field instead of beneath each of the three Tripower inverters inside the building. This approach provides a rooftop disconnecting means and meets NEC Section 690.35 requirements for ungrounded arrays. Separating the inverters and Connection Units proved to be the most cost-effective solution to switch and provide series fusing for each of the dc current–carrying conductors. The NEMA 3R–rated Connection Units are mounted vertically behind the last row of each of the three array segments. The 20 kW 3-phase SMA Tripower string inverters and associated switchgear are located in an interior equipment room adjacent to the point of connection.

“It’s not every day you work both with and for an electric utility on a solar project. It was a real privilege to collaborate with GMP. Installing a 62 kW PV plant directly adjacent to a roaring 12 MW turbine and 46 kV of humming high-voltage infrastructure provided a striking contrast and reinvigorated the crew’s interest in rooftop safety.”

Khanti Munro, Positive Energy NY

Overview

DESIGNER: Khanti Munro, vice president, Positive Energy NY, positiveenergyny.com

LEAD INSTALLERS: Josh Thomas, foreman; Joe Thomas, superintendent, Positive Energy NY

DATE COMMISSIONED: May 2014

INSTALLATION TIME FRAME: 9 days

LOCATION: Rutland, VT, 43.6°N

SOLAR RESOURCE: 4.27 kWh/m2/day

ASHRAE DESIGN TEMPERATURES:  84°F 2% avg. high, -15°F extreme min.

ARRAY CAPACITY: 62.1 kWdc

ANNUAL AC PRODUCTION: 67,700 kWh

Equipment Specifications

MODULES: 230 SolarWorld Sunmodule Plus SW 270 Mono, 270 W STC, +5/-0 W, 8.81 Imp, 30.9 Vmp, 9.44 Isc, 39.2 Voc

INVERTERS: 3-phase 277/480 Vac service, 3 SMA Sunny Tripower 20000TL-US, 20 kW, 1,000 Vdc maximum input, 150–1,000 Vdc operating MPPT range (array configuration limited maximum system voltage to under 600 Vdc)

ARRAY: 10 modules per source circuit (2,700 W, 8.81 Imp, 309 Vmp, 9.44 Isc, 392 Voc), eight source circuits per inverter typical (21.6 kW, 70.48 Imp, 309 Vmp, 75.52 Isc, 392 Voc), array capacity total: 62.1 kW

ARRAY INSTALLATION: Fully ballasted low-slope roof mount, EPDM membrane roofing, SunLink Precision RMS racking, 140° azimuth, 15° tilt

SOURCE CIRCUIT COMBINERS: 3 SMA Connection Units, 15 A fuses

SYSTEM MONITORING: Direct Ethernet connection to each inverter, SMA Sunny Portal web interface; view system production at http://tinyurl.com/ocmdo5e

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The LEED Silver–certified Oshman Family Jewish Community Center (OFJCC) is host to one of the largest PV installations in Palo Alto, California, and one of the largest projects to utilize Trina Solar’s Trinasmart dc-optimized modules. The 397.5 kWdc PV array spreads across 12 rooftops. The installation is also one of the first to use Unirac’s RM Roof Mount ballasted system, which accommodates the different layouts, variable surfaces and obstacles that each of the roofs presents. The OFJCC project has strong economic fundamentals. Its developer, THiNKnrg, worked with Conergy and its owner, Kawa Capital Management, to structure a PPA that would supply the OFJCC with solar energy for $0.04/kWh, the lowest cost for PV-generated energy on public record in California.

The Trinasmart module junction boxes fully integrate Tigo Energy’s optimization technology. The combined solution features module-level MPP tracking for optimal energy yield and design flexibility, as well as module-level monitoring and disconnect. While Cobalt Power Systems installed the system under NEC 2011, it is compatible with NEC 2014 Section 690.12 requirements for rapid shutdown. Tigo Energy’s PV-Safe technology enables the Trinasmart modules to automatically deactivate as soon as workers disconnect ac power.

The Trinasmart modules can enable string lengths up to 30% longer than those of conventional 600 Vdc systems due to the integrated Tigo Energy optimizer’s maximum voltage limiting function. Cobalt Power Systems was able to increase source circuits from 14 modules to 17- and 18-module strings, eliminating 24 source circuits, three combiner boxes, 13,500 feet of wire and the corresponding labor from the system’s BOS costs, which reduced the total cost of the system by $22,000.

The system designer located the KACO new energy 3-phase 480 Vac TL3 inverters on individual rooftops adjacent to their corresponding array locations. Palo Alto’s structural and seismic requirements necessitated special bracing for the rooftop-mounted inverters. Cobalt Power Systems developed custom inverter support structures to create dedicated electrical areas and secure inverter connections to the building.

To reduce the number of ac circuits exiting the 12 rooftops, the design called for aggregation of each inverter group. The installers routed the combined circuits to the main electrical service entrance located in the basement of the OFJCC’s main facility, where they used a secondary ac aggregation panel to make the final parallel connections. They utilized a fused disconnect located adjacent to the main distribution panel to make a load-side connection to the system’s aggregated ac power output.

“We turned to Trinasmart optimized by Tigo Energy to help us optimize this project. With this solution, we get increased production, lower BOS costs and higher returns for our customers. In the end, the project had better economics using Trinasmart, and for us that is what drives projects.”

Zach Rubin, CEO, THiNKnrg

Overview

DEVELOPER: THiNKnrg, thinknrg.net

DESIGN & INSTALLATION FIRM: Cobalt Power Systems, cobaltpower.com

DATE COMMISSIONED: April 2014

INSTALLATION TIME FRAME: Four months

LOCATION: Palo Alto, CA, 37.4°N

SOLAR RESOURCE: 5.4 kWh/m2/day

ASHRAE DESIGN TEMPERATURES:  90°F 2% avg. high, 32°F extreme min.

ARRAY CAPACITY: 397.5 kWdc

ANNUAL AC PRODUCTION: 633,000 kWh

Equipment Specifications

MODULES: 1,590 Trina Solar Trinasmart DC TSM-250-PA05.002, 250 W STC, +3/-0%, 8.27 Imp, 30.3 Vmp, 9.5 Isc, 32.5 Voc (limited by module-integrated dc optimizers)

INVERTERS: 3-phase 480/277 Vac service, six KACO new energy 32.0 TL3 (32 kW, 600 Vdc maximum input, 310–550 Vdc MPPT range), five KACO new energy 40.0 TL3 (40 kW, 1,000 Vdc maximum input, 390–850 Vdc MPPT range)

ARRAY: 18 modules per source circuit (4,500 W, 8.27 Imp, 545.4 Vmp, 9.5 Isc, 585 Voc) or 17 modules per source circuit (4,250 W, 8.27 Imp, 515.1 Vmp, 9.5 Isc, 552.5 Voc); seven source circuits per 32 kW inverter, nine source circuits per 40 kW inverter; 397.5 kWdc array capacity total

ARRAY INSTALLATION: Low-slope roof mount, TPO membrane, Unirac RM Roof Mount, ballasted, 180° azimuth, 10° tilt

SOURCE-CIRCUIT COMBINERS: Five SolarBOS CS-12/12-15-4XF, five SolarBOS CS-8/8-15-4XF, five SolarBOS CS-6/6-15-4XF, 15 A fuses

SYSTEM MONITORING: Module-level monitoring, five Tigo Energy Module Management Units (MMUs), 27 Tigo Energy Gateways, Trinasmart/Tigo Energy monitoring service

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The Plymouth Public Schools (PPS) district is one of the first in the country to purchase 100% of its energy from solar sources. Initially, Borrego Solar planned to install 8–10 PV arrays on campuses across the PPS district. A combination of older roof structures and snow loads drove PPS and Borrego Solar to an alternative plan to develop two expansive ground-mounted solar arrays on nearby private property. Together, the arrays cover more than 23 acres of land—an area roughly the size of 18 professional football fields. The larger array comprises 23,647 solar modules on land leased from Plympton Sand & Gravel.

In Massachusetts, large PV installations can have separate entities as the host (land owner), energy off-taker (end user) and system owner (investor). In the Plympton project, the host generates revenue by leasing the land used to house the project. As the off-taker, PPS agrees to purchase the solar power from the owner at a predetermined rate that is $0.06/kWh less than what it would be from NSTAR Electric and Gas. With a power purchase agreement, PPS will save approximately $400,000 on energy annually ($8.5 million over the 20-year PPA term), and the district avoided incurring the up-front project costs of about $11 million.

“The PPS solar installation in Plympton, Massachusetts, the largest of the district’s arrays, won a Project of Distinction award at this year’s PV America East conference in Boston. Thanks to innovative net metering in the state, PPS is able to virtually apply the solar energy produced off-site to its own utility meters.”

Philip Hall, director of marketing, Borrego Solar

Overview

DESIGNER: Gabe Landes, senior design engineer, Borrego Solar, borregosolar.com

INSTALLERS: Charles Barbanti, project manager; Joe Daugirda, site superintendent, Borrego Solar

DATE COMMISSIONED: October 2013

INSTALLATION TIME FRAME: 150 days

LOCATION: Plympton, MA, 42°N

SOLAR RESOURCE: 3.81 kWh/m2/day

ASHRAE DESIGN TEMPERATURES:  88°F 2% avg. high, 0°F extreme min.

ARRAY CAPACITY: 5.597 MWdc

ANNUAL AC PRODUCTION: 7,235 MWh

Equipment Specifications

MODULES: 8,502 Sharp ND-235QCJ, 235 W STC, +5/-0%, 8.02 Imp, 29.3 Vmp, 8.60 Isc, 37.2 Voc; 8,125 Sharp ND-240QCJ, 240 W STC, +5/-0%, 8.19 Imp, 29.3 Vmp, 8.75 Isc, 37.5 Voc; 6,721 Yingli YL235P-29b, 235 W STC, +5/-0%, 7.97 Imp, 29.5 Vmp, 8.54 Isc, 37 Voc; 299 Inventec Energy IECS-6P6A-235, 235 W STC, 7.92 Imp, 29.69 Vmp, 8.55 Isc, 37.03 Voc

INVERTERS: Eight SMA Sunny Central 500HE-US, 500 kW, 600 Vdc maximum input, 330–600 Vdc MPPT range, 200 Vac nominal output, two inverters per 1,000 kVA step-up transformer

ARRAY: 13 modules per source circuit, 26 source circuits per combiner (typical), nine combiners per inverter; 1,819 source circuits total, 5.597 MWdc array capacity total

ARRAY INSTALLATION: Ground mount, SunLink Large-Scale Ground Mount System (GMS), 180° azimuth, 25° tilt

SOURCE CIRCUIT COMBINERS: 72 Bentek BTK26D-400A, 15 A fuses

ARRAY RECOMBINERS: Eight Bentek BTK-CBSS-ET-9400-S, 350 A and 400 A circuit breakers

SYSTEM MONITORING: AlsoEnergy DAS at each of four inverter pads, shared weather station

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Johnson Melloh Solutions worked closely with Fronius team members to design and install an R&D facility at Fronius’ US headquarters in Portage, Indiana.

The first stage of the Innovations Test Research and Application Center (ITRAC) system is comprised of a 55 kW roof-mounted array and two 3 kW trackers. The system provides Fronius USA and Fronius International with renewable energy for its US corporate headquarters and for an in-house test and engineering lab. Built with future expansion in mind, the facility allows for the high-power demands of the on-site welding labs and inverter production lines.

The heart of the ITRAC system is a new inverter lab located next to the technical support office. Johnson Melloh designed the inverter wall with 5/8-inch plywood under the sheetrock to provide a versatile mounting surface. A raceway with dividers that separate ac, dc and communication cables runs the length of the lab, with a fused dc combiner/disconnect at one end. For inverter testing, Johnson Melloh installed two 3-phase ac panelboards (277/480 Vac 200 A and 120/208 Vac 200 A) at the opposite end of the raceway. The crew installed additional ac disconnects inline with the PV panel-boards on the exterior of the building to comply with Northern Indiana Public Service Company’s requirements for utility-interactive PV systems.

The dc side of the system utilizes 1,000 Vac–rated components to enable testing of 1,000-volt inverters. The ballasted roof-mounted array is fairly typical for a commercial installation. However, Fronius staff needs to be able to reconfigure strings in the inverter lab during testing. To facilitate the setup for this need, Johnson Melloh combined all dc source circuits in a custom combiner box located in the lab rather than on the roof.

The crew installed the two tracked subarrays in front of the building, where they are highly visible to both customers and Fronius employees. During the initial build-out, the team installed conduit under the parking area and driveway to accommodate wiring for the tracker installation. This proactive planning streamlined the installation, although the long-distance ac run from the two pole-mounted Fronius inverters to the closest subpanel was still quite challenging.

Data communications development and testing are important components of the inverter lab. The system ties a roof-mounted weather station into an Obvius AcquiSuite data acquisition server in the lab. The installation splits the inverters into groups for testing various monitoring options that include SunSpec Modbus RTU and TCP, Wi-Fi and ZigBee. Both trackers use the new Fronius Datamanager Card to send data via Wi-Fi to a wireless router inside the building. That data goes to a Fronius Solar Web monitoring portal, and the company website uses the installation as a demonstration system.

The 150 kW second phase of ITRAC is under construction. It will include expanded testing facilities, arrays with multiple azimuths and custom combiner boxes for source-circuit reconfiguration during equipment testing.

“Working with the Fronius team gave us a refreshing perspective. Fronius is committed to R&D and decreasing install time, which ultimately leads to savings for our customers.”

—Jeff Cole, Johnson Melloh Solutions

“The installation experience and live system data collected from the ITRAC system will help Fronius design products and services that specifically target the US market and provide insight for our team and customers.”

—Sebastian Hassell, product manager, Fronius USA

Overview

DESIGNER: Tim Kennedy, Johnson Melloh Solutions, johnsonmellohsolutions.com

LEAD INSTALLER: Jeff Cole, project manager, Johnson Melloh Solutions

DATE COMMISSIONED: November 2013

INSTALLATION TIME FRAME: 25 days

LOCATION: Portage, IN, 42°N

SOLAR RESOURCE: 4.2 kWh/m2/day

ASHRAE DESIGN TEMPERATURES:  91°F 2% average high, -8°F extreme minimum

ARRAY CAPACITY: 61 kWdc

ANNUAL AC PRODUCTION: 78,959 kWh

Equipment Specifications

MODULES: 244 CentroSolar E250B, 250 W STC, +5/-0 W, 8.24 Imp, 30.34 Vmp, 8.76 Isc, 37.47 Voc (220 modules roof mounted, 24 modules tracked)

INVERTERS: Rooftop array: 3-phase 120/208 Vac service, two Fronius IG Plus Advanced 3.0-1 (3 kW, 600 Vdc maximum input, 230–500 Vdc MPPT range), four Fronius IG Plus Advanced 7.5-1 (7.5 kW, 600 Vdc maximum input, 230–500 Vdc MPPT range), two Fronius Galvo 3.1-1 (3.1 kW, 600 Vdc maximum input, 165–440 Vdc MPPT range); 3-phase 277/480 WYE Vac service, two Fronius IG Plus Advanced 12.0-3 (12 kW, 600 Vdc maximum input, 230–500 Vdc MPPT range)

INVERTERS: Tracked array: 3-phase 120/208 Vac service, two Fronius IG Plus Advanced 3.0 -1 (3 kW, 600 Vdc maximum input, 230–500 Vdc MPPT range)

ROOFTOP ARRAY INSTALLATION: Low-slope ballasted roof mount, membrane and gravel roofing, AET Rayport B stainless steel ballasted racking, 180° azimuth, 10° tilt

TRACKED ARRAY INSTALLATION: Two Array Technologies DuraTrack DA trackers, dual axis, 12 modules each

SYSTEM MONITORING: Fronius DATCOM with Fronius Solar Web monitoring

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