Case Studies

Halco Case Studies: 12.42 kW Solar Electric System Expansion in Ithaca, NY

Saturday, October 1st, 2011 by Hal Smith


This Net-Zero home in Ithaca needed a solar electric system expansion.


This 12,420 W (12.42 kW) grid-connected solar electric system was installed as fifty-four (54) SunPower 230 W solar modules oriented South on three (3) Direct Power and Water adjustable-tilt top-of-pole mounts. The poles The poles were installed beside the Customer's existing five year old 5kW system, and hold the modules arranged as six (6) rows of three (3) modules in landscape, and each have typical dimensions ranging from 15.4 ft x 9.7 ft x 14.3 ft (width x height x depth) at 25° tilt to 15.4 ft x 15.9 ft x 9.1 ft (width x height x depth) at 55° tilt, as illustrated in the accompanying schematic diagram. The array layout is designed to maximize system size while allowing only minimal losses due to shading and ensuring the system is aesthetically pleasing and well-integrated with the property. The system is configured electrically as six (6) DC circuits (strings) of nine (9) series connected modules providing input through two (2) DC disconnect switches to two (2) SunPower 6000m, 6.0kW inverters. These inverters provide grid-synchronous AC output and interface to the electric utility through a direct tap in the Customer's main service panel, as existing infrastructure allows. For maximum cost effectiveness, the DC wiring from the system was taken back directly to the house in buried 2" PVC conduit, and the inverters and the electrical BOS for the project were mounted there in the house basement.

As designed, this system should generate 14,097 kWh per year, for an average of 39 kWh/day, where daily energy production is both weather and seasonally dependent. In combination with the production from the Customer's existing solar electric system, this energy production will be equivalent to 117% of the customer's modeled future home electrical usage after geothermal system installation and insulation improvements, and corresponds to a CO2 (greenhouse gas) emissions savings of 18,326 lb per year.

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