Increasing Production with Single-Axis Tracking : Page 3 of 3

Intermediate

Inside this Article

20 PV panels on 10 single-axis trackers
A single actuator arm adjusts 20 PV modules on 10 single-axis trackers.
The back side of the tracking array
The back of the tracking array, showing the mounting base, pivots, and the long actuator arm.
PV output wire routing
The routing of PV output wires and ground connections at the top of the pivot rods allows full movement without binding or pinching the wires.
Microinverter circuits and tracker disconnect
Microinverter branch circuits and tracker disconnect.
20 PV panels on 10 single-axis trackers
The back side of the tracking array
PV output wire routing
Microinverter circuits and tracker disconnect

The microinverters were mounted on a horizontal cross-piece of Unistrut that also serves as wire management for AC and DC wiring and the equipment-ground wire. This required extending the wires from the modules with custom MC4 extensions. The modules help shade the inverters, allowing them to operate more efficiently. Each inverter is connected to the equipment-grounding conductor through the manufacturer-supplied grounding point. The microinverters greatly simplified the DC wiring, which would have been rather complex if we had to series-wire between the tracking pivot arms.

The two branch circuits from the microinverters were combined on the tracker rack using a standard outdoor air-conditioning disconnect that had two 15 A, 240 VAC breakers combined into one 30 A disconnect output circuit. This allows the system to be disconnected on the roof for commissioning tests and maintenance, and allows troubleshooting of each branch circuit. This circuit then passes through the production meter and is interconnected on the load side of a 240 V subpanel with a 30 A breaker in the building. A separate circuit powers the tracker actuator and control electronics.

System Performance

DH Solar is new to the PV industry but has had a long-standing business making satellite trackers. The system was lightweight, but very strong because of additional cross-bracing.  The tracker has to be manually programmed for seasonal variations. With 32 programmable positions per day, it is not as accurate as a tracker using astronomical data for a specific latitude and season.

The system has been operating for only five months, so it is too soon to see how well it is performing compared to the SAM predictions. The first month had only three weeks of production and we had an unseasonably cold and wet summer. The last month was also poor, since smoke from nearby forest fires significantly impacted PV production.

Access

Bill Hoffer has worked in the solar industry in the Pacific Northwest for more than 16 years. He is a NABCEP Certified Solar PV Installer and a professional mechanical engineer in Washington state. He lives in a straw bale home he designed and built himself, and is an avid gardener and skier.

PV System Equipment:

APS • solaraps.com • Microinverters

DH Solar • dhsolar.net • Single-axis tracker

Itek Energy • itekenergy.com • Modules

Comments (5)

todd j lazich's picture

To all: The individual frames for the single axis tracker are 5' apart. I was told that DH Solar has discontinued this system because of lack of volume sales. However, I just managed to place an order for 4 frames to add to my initial system of 2 frames (4-250W modules. The frames are pretty simple to replicate....galvanized pipe, a few gussets. angle steel. I tqlked with the owner and he did not have a problem with me replicating these frames. I intend to make a frame out of square tube aluminum and test it out on my system. I would think that you still could get the controller/actuator from DH for about $800.

Best regards, solar friends

hbintx's picture

I recently emailed DH for more info and was informed they have discontinued this product. No reason was offered. They still make 2-axis trackers derived from their long-time satellite dish systems.

doutmind's picture

These are very nice steps on increasing production using single axis trackers. Hopefully people who are thinking to use dual axis trackers will also give a second thought on this.

Lloyd Scales's picture

What is the horizontal spacing, panel to panel? From the article it calculates out as each panel (39.1 inches wide) then a 56.9 inch gap then the next panel. Is this correct? If so, is there a general rule for spacing on an East to West layout?
L. Scales

Michael Welch's picture

Hi Lloyd. This system's pivots were on an 8 ft. center. But in general, the trick is to figure out how low in the sun's arc you want to be able to capture the sunlight. Obviously, with the sun at the horizon only the closest end module will catch it. Then knowing the height of one module corner can let you compute the distance to the next module. Our friends at Miller Solar have developed a spreadsheet for determining row spacing, but it can be applied to this situation. Check it out at http://millersolar.com/MillerSolar/...

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