Moore Power: Page 2 of 2

Intermediate

Inside this Article

The completed 6.75 kW array.
Solar Pathfinder
The Solar Pathfinder software calculated the usable solar irradiation at the site. The translucent yellow shading on the photo depicts deciduous trees.
Lauren Craig and Kyra Moore install the PV modules.
Sunny Boy 6000-US inverter
This Sunny Boy 6000-US inverter (bottom) has an integrated DC disconnect and integrated series string combiner. The box above the inverter is the SunPower remote monitor that’s linked wirelessly to a receiver plugged into the home network router.
SolaDeck Junction Box
The SolaDeck junction box was painted to match the roof.
The AC side of the system with supply-side connection. The PV AC fused disconnect is at the bottom right. The junction box (bottom left) splices the output of the PV AC disconnect to the utility lines from the meter (upper left) and to the main service disconnect (above disconnect and junction box).
Jerry Moore and his daughter (and PV installer) Kyra pose with the completed system.
Solar Pathfinder
Sunny Boy 6000-US inverter
SolaDeck Junction Box

Installation

The home’s triangular roof had a skewed edge, so instead of a ladder we used a scissor lift for worker access. (See the “Roof Safety” sidebar for other challenges and solutions.)

Attaching the feet and rails to the standoffs installed by the roofers was straightforward due to our design work. With the SolarMount system, the first module’s placement is crucial. If the first module is even slightly askew, the discrepancy will be magnified going down the row. I always start the installation on the bottom, so that once a row is in place, there’s somewhere to rest the next row of modules.

To minimize the effects of late-afternoon shading, we wired the modules in three sections, in columns, so that there was a western, middle, and eastern string configuration. As the tree’s shadow creeps onto the western part of the roof, it will take the strings out one by one. If the strings had been organized by rows, the entire array would have stopped producing as soon as the shadow line crossed the first column of west-most modules. This also had safety benefits by allowing us to work on one side of the roof at a time—we did not have to constantly switch anchor points for our ropes to prevent swinging.

To make the wiring transitions to the attics, I typically use SolaDeck’s flashed junction box, which can be hidden underneath the array. This allows the penetration to be hidden under a module and still comply with the NEC article 690.34 requirement of being “rendered accessible directly or by displacement of a module.” But since this wiring couldn’t be located under the array due to attic access, we painted the low-profile combiner box to match the roof and positioned it 2 feet below the array to make a penetration into an accessible garage space where the inverter was located.

Since we opted for a supply-side tap for interconnection, we no longer had to make our way from the inverter to the main service panel, but rather to the outside of the house near the meter location. After coordinating with a licensed electrician and the local utility, we ran our inverter output outside to an AC fused disconnect. We then added a junction box to tap into the service lines between the meter and the home’s main service panel. We installed a ground rod for grounding the module frames and inverter, and buried a copper conductor and tied it to the existing electrical service ground rod.

After making the last connections on the roof, we ordered the final inspection by the local electrical inspector. Following their approval, the utility company replaced the existing electric meter with a new bidirectional meter and officially commissioned the system for service. At last, we reinstalled the DC fuses in the inverter, engaged the DC and AC disconnects, and started producing home power!

Performance

System performance was predicted using the Solar Pathfinder software and NREL’s PVWatts online calculator. PVWatts uses system size, location, historic weather data, orientation, and tilt to estimate production. You can get even more precise by manipulating the calculator’s derate factors. We changed the shading factor to 81% to coincide with the Solar Pathfinder’s results, and inverter efficiency of 95%, which resulted in a 0.643 DC-to-AC derate factor. PVWatts predicted this system would produce about 8,020 kilowatt-hours (kWh) per year. The system’s first year of production, from January 1, 2009, through January 1, 2010, was 9,175 kWh—14% more than the estimates. The system’s energy production continues to exceed household energy consumption.

Access

Kyra Moore is a 2008 graduate of SEI’s women’s course. She joined Southern Energy Management (SEM) as a solar technician soon after graduating. Now a NABCEP-certified solar installer, she is a commercial systems designer. Kyra also instructs classes on solar electricity for the North Carolina Solar Center.

Comments (1)

Roberto Tapia's picture

Hi , Kayra Moore
Congratulations for your Photo Voltaic System
I am working in a pilot Project with a submersible pump that is used for irrigation , the nominal values of the pump are 480 V, 3 Phases , 60 Hz, 75 KW
The scope of the project is to fed the electriciy to the pump during the solar day with Photo Voltaic system , Our system is sized for 75 KW on the AC side , the arrangement will be Batteryless Grid tied .
Is all the electricity produced by your PV Sysem used in your house or some part is send to the grid ?
Is your system batteryless grid tied ?
Is the start up of your a/c back uped by the grid ?
Can you sell to Nicaragua Central America all the equipment for this pilot project ?
The general project is for 15 Pumps

Best Regards

Roberto Tapia

Proyectos@cumanenterprise.com
robertotapialaex@yahoo.es

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