Tracking PV in Washington State

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Tracking PV in Washington State
Tracking PV in Washington State

“It doesn’t have to go on your roof,” I explained to homeowner Eric Lindgren of Bonney Lake, Washington, while Alex from Brothers Electric Solar was on the roof measuring for a new PV array. To take advantage of Washington’s production incentive program, Lindgren was considering installing a 9-kilowatt solar-electric system, which would generate enough energy to recoup costs before the program expires in 2020. But the roof had its challenges: it was partially shaded and the shingles needed to be replaced. At a 5:12 pitch, it wasn’t at an optimal angle for a flush-mounted PV array. Plus, there wasn’t enough space on the roof to fit a PV system that would max out the yearly incentive payment. Lindgren’s south-facing yard was huge, though—perfect for a ground-mounted array.

We measured the area for a 9.12 kW array. To capture the highest incentive rate, we needed to use Washington-made equipment, which meant using 38 Itek Energy 240 W modules and Altenergy Power System (APS) microinverters. The same modules installed on a dual-axis tracking mount, however, only needed to be 7.2 kW, since production increases by up to 28% with a tracked array at this location. We estimated that two rows of 15 modules each on Sedona Solar dual-axis frames could produce the kilowatt-hours needed to pay off the system within seven years.

Compared to the fixed system, installing a dual-axis tracking framework and controllers was less expensive, since there were eight fewer modules and inverters to purchase. An added bonus in Lindgren’s case is that the two arrays fit perfectly around his garden.

The framework that holds the modules and tracking frames is mounted on eight 4-inch-diameter galvanized steel posts set in concrete. Two actuating arms control the array’s elevation and another controls its azimuth. They are energized by the controller and position the array by calculating the sun’s position based on the site’s longitude, latitude, and local time.

Each module is wired to a microinverter. The inverters and wiring had to be carefully placed on the framework to avoid any contact with the rotating modules and rack. Module-level online monitoring is through the APS software, and a smartphone app (designed by Lauritzen Inc.) is available for remote operation of the system. Having remote control of the array allows the system owner or installer to reposition the modules for cleaning, maintenance, storm readiness, or even snow clearing—without having to open up the control box on each subarray. The smartphone app allows access to the controller’s many parameters with a joystick-like interface.

Dave Cozine

Comments (4)

pvwattsup's picture

Great project. But you make it out to seem as if Itek is the only option for Washington made modules. Silicon Energy's Cascade series also qualifies. Not saying Silicon Energy is the right choice for this job, but it was an option as well.

ben_marko's picture

I am still not sold on PV for residential use. Really not efficient for the money. I had three PV companies try to sell me on PV for my home (I live in the desert, lots of sunshine), but they only skimmed over the actual efficiency numbers. Efficiency versus cost of savings, both had me saying no. The cost of the PV systems was high, even with lease programs - those offer low payments ($60 or so) with no money down, and maintenance included. One company wanted me to pay $100 a month for a lease. Payments for a system I would own would be roughly the same, based upon a 30-year loan (I thought they only did that with homes). It cost that much...$24,000 was the lowest quote I got. Both lease and buy energy/cost savings combined with what I would have paid to the power company after installation would have returned my bills back up to pre-PV levels. Really not financially efficient.

Much better to limit residential use to offsetting power consumption for now, not replacing it. All of the companies I spoke to wouldn't do that. I just wanted a PV setup for my central A/C. But no, they had to try and sell the whole thing or nothing. The cost alone combined with their relative inefficency (compared to other sources) turned me away for awhile. I'm sticking with wind power for now, it is much better for where I live.

Michael Welch's picture

Sorry you had a bad experience with the PV dealers. I know there are a bunch of great ones that would have listened to you and talked things out. I have never heard of anyone doing "efficiency per cost" comparisons to help determine the usefulness of PV installation.

Efficiency does not really matter much, except when you have limited space for installation.

What kind of wind generator do you have?

Jorgen Rasmussen's picture

I have a fixed 7.2kw system (eastern WA) just like this system. I like to propose we compare production on PVOUTPUT = http://pvoutput.org/ I'm registered under Jorgen

Let me know through the web site

Jorgen

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