Sunsense Solar: SMPA Community Solar Farm

The San Miguel Power Association (SMPA) Community Solar Farm allows SMPA members to purchase modules installed in the system and receive credit on their monthly power bill for the energy that the modules generate. The innovative project was a collaborative effort. Clean Energy Collective (CEC) pioneered a community solar model that facilitates member ownership of collectively owned medium-scale solar generation facilities, and functioned as the project developer. Martifer Solar acted as the primary contractor and was responsible for construction financing and product procurement. Sunsense Solar led the design, engineering and construction efforts for the project.

The remote 9.27-acre site presented several challenges. The gently rolling landscape would have required major, and costly, excavation to create level array pads. To minimize site preparation costs, a “table wave” strategy was employed with varying subarray sizes that allowed the array to follow the site’s contours smoothly. Large areas of bedrock and layers of gypsum required precise alignment and ramming of anchor piles. With repeated wear and tear during construction, the gypsum layer over much of the site turned to a fine dust that complicated working conditions. The team left sagebrush ground cover on-site to stabilize the soil.

The project utilizes two Hanwha SolarOne module models that were  manufactured in different locations (China and South Korea) and that have slightly different dimensions and electrical specifications. These differences required specific module and array grouping for source-circuit sizing and racking. Final array tables range from 4-by-7 to 4-by-13 module layouts.

The designers selected an AE Solar Energy PowerStation 1000NX for power conditioning. The skid-mounted station includes two 500 kW inverters and a 1,000 kVA transformer that steps down the utility’s 25 kV service to 480 Vac. A 15 kVA service-center transformer feeds a 100 A 120/240 Vac single-phase 3-wire switchboard. The PowerStation also includes two metering cabinets, two communications cabinets and a 2,000 A switchboard with two 800 A backfeed breakers. A weather station is mounted to the shade structure that covers the inverters, transformers and switchgear.

Sunsense Solar worked with AE Solar Energy to make adjustments to the skid layout to accommodate the monitoring and metering equipment that SMPA and CEC require. CEC’s proprietary RemoteMeter system automatically calculates monthly credits for project members and integrates with the utility’s existing billing system.

The remoteness of the site required special attention to mobilization, staging, security and scheduling, as well as adequate secure storage for a large inventory of PV components, spare parts, tools and machinery. The diverse group of contractors and organizations that participated in the project included subcontractors, electrical inspectors, county officials, the Colorado Department of Transportation and the utility. Meeting schedules and milestones became a prime consideration for on-time project completion.

“In spite of 100-plus-degree heat to below-zero temperatures, dry desert wind to rain and snow, the construction crew brought the project home in a timely fashion. In the face of these adverse conditions, the crew maintained a safe and secure site and an amazing attention to detail.”

—Scott Ely, president, Sunsense Solar

Overview

PROJECT DEVELOPER: Clean Energy Collective, cleanenergycollective.com

PRIMARY CONTRACTOR: Martifer Solar, martifersolar.com

DESIGNER: Jeff Lauckhart, lead PV designer, Sunsense Solar, sunsensesolar.com

LEAD INSTALLERS: Mark Item, project manager, Sunsense Solar; Levi Heinold, site supervisor, Mountain Power Company

DATE COMMISSIONED: December 2012

INSTALLATION TIME FRAME: 120 days

LOCATION: Paradox Valley, CO, 38.5°N

SOLAR RESOURCE: 6.0 kWh/m2/day

HIGH/LOW DESIGN TEMPERATURES: 100°F/-23°F

ARRAY CAPACITY: 1.1 MWdc

ANNUAL AC PRODUCTION: 1,731 MWh

Equipment Specifications

MODULES: 4,784 total; 1,170 Hanwha SolarOne HSL60P-PA-0-235K, 235 W STC, +5/-0 W, 7.89 Imp, 29.8 Vmp, 8.51 Isc, 37.1 Voc; 3,614 Hanwha SolarOne SF220-30-1P235L, 235 W STC, +5/-0 W, 7.81 Imp, 30.1 Vmp, 8.44 Isc, 36.8 Voc

INVERTERS: AE Solar Energy PowerStation 1000NX: two AE 500NX-HE inverters (500 kW, ±600 Vdc maximum input, ±330–±600 Vdc operating range), 1,000 kVA 25 kV/480 V transformer, 15 kVA service-center transformer

ARRAY: Bipolar; 13 modules per source circuit (for Hanwha SolarOne SF220 model: 3,055 W, 7.81 Imp, 391.3 Vmp, 8.44 Isc, 478.4 Voc); 13–19 source circuits per combiner; 368 source circuits total; array total (1.12 MW, 1,429 Imp, ±391.3 Vmp, 1,562 Isc, ±478.4 Voc)

ARRAY INSTALLATION: Ground mount, driven piles, S:Flex racking, 180° azimuth, 35° tilt 

ARRAY STRING COMBINERS: 24 SolarBOS Disconnecting Combiners, 15 A fuses

SYSTEM MONITORING: Clean Energy Collective proprietary wireless monitoring, San Miguel Power Association wireless metering

Article Discussion