Standard Solar and SunEdison: Konterra Solar Microgrid
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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
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
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