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Saturday, September 20, 2014

Installing solar panels

Solar panels have been on the project list since early in the boat build process.  Here's the original debate that I had with myself on the subject.  Despite lingering questions I decided to go ahead and install them right from the start.  One big reason was the simple convenience of doing it now rather than later when the boat is in some unknown location with unknown services available.  And solar panels are large and awkward and need to be shipped by truck, and if you have ever taken delivery of a truck shipment at anything other than a commercial location with a shipping dock, you will know that it is a royal pain in the rear end.

The chosen location for these buggers is up on the fly bridge hardtop.  It's a great location with excellent exposure, little to no shadowing, and a solid and secure mounting structure.  I used a roof mounting system that is popular on land consisting of two rails that run the width of the hardtop and bolt to the decking with 3 feet on each rail.  The panels then lie on top of the rails, and there are clamps that attach them to the rails.  It's a very solid system with wind rating up to 150 mph.

Below is a picture of the three panels up on the roof.  Each is 250 watts for a total of 750 watts.  The panels come with a junction box and pig-tail wires with special water proof connectors commonly used in the solar industry.  Wiring them up is simple a matter of connecting the panels up in a daisy chain.  The result are panels wired in series such that the voltages of each add up giving an operating voltage of around 100VDC.

Panels installed on fly bridge hardtop

 Shadowing is a major concern with solar panels since a small shadow can disproportionately reduce power output.  Other than the sea gull crap visible in the picture above, the biggest issue is the 6 foot open array radar which you can see in the pictures above and below.  If the antenna isn't parked athwart-ships (side to side) it casts a pretty good shadow on the panels.  Fortunately, the Simrad radar has a feature where you can set the part angle.  Unfortunately, it doesn't work.  There are two problems, one of which Simrad was already aware of, and another they were not.  The first is that the programmed park angle does not have any fixed orientation, so setting it to 90 deg  actually corresponds to some random angle.  Also, the array doesn't park with any kind of precision.  It just comes somewhere kinda near the random angle location that you program.  But through experimentation by increasing the angle a bit at a time, you can figure out what angle corresponds to the desired location.  On mine, -100 deg is kind of athwart-ships, and most of the time it parks clear of the panels.  Then comes the other problem.  When you turn off the breaker to the radar, it forgets the programmed park angle.  I sure hope they get it fixed sooner rather than later.  As a side note, I don't think any of the other big marine electronics vendors support a park angle at all, let along one that works, but it's still frustrating to have advertised features that don't work.

Radar casting a shadow over panels

The daisy-chained wires then get fed through cable glands into the hardtop cavity where the wires then run down to the pilot house.  That dangling wire is a green wire safety ground that isn't yet hooked up.

Power and ground cables feed through the hardtop

Down in the pilot house is the charge controller, tucked away in the electrical closet.  This was the best location from the perspective of wiring, but it leaves the control panel somewhat difficult to access.  In time I'll solve that by running a Cat5 cable from the charge controller back to the other Outback inverter gear and tie it into that system.  Then the charger will be accessible from the control panel on the fly bridge console.

It's a little hard to see in the picture, but the controller is taking in 6.9A at 86V and putting out 20A at 26.1V, harvesting 540W from the panel's theoretical max of 750W.  This is actually a bit less than I expected, but I won't really get a chance to check it out closely until we spend some time at anchor.

Charge controller doing its thing

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