Designing and building a 170W solar energy platform with MPPT controller

Based on my energy usage projections I needed to generate some 80-100 Ah/Day of energy without using the engine. I was looking for Solar to generate about 40Ah, but the problem was where to put the solar panels.

Choosing the best solar panel and location

I knew that even a tiny bit of shade was really bad for solar panel performance, but I read that new CIGS solar panels could perform better with shade. I wanted to test this out in real life, so I conducted an experiment with two different panels at different locations

Testing the CIGS thinfilm 70W panel

First was a new CIGS thinfilm Sunforce 70 Watt panel under the boom where I had plenty of space but had a lot of shade with the boom and rig.

Testing the Kyocera 85W panel

Second was a more standard Kyocera KC85T 85W Solar Panel situated between the transom and the windvane. When the sun was directly above there weren’t any shadows.


I wired them up to a Blue Sky MPPT Solar Boost 2000E Charge Controller to test the output especially around midday when the sun was overhead. The MPPT charge controllers are more expensive but deliver more power because they convert all the energy above 12V into more amps. I found that the Kyocera 85W panel at the stern location delivered nearly 3 times as much as the CIGS panel, nearly 7 amps at times. If I could generate 10Amps with 2 panels over a 4 period I could hit my target of 40 AH a day from solar! So I decided to go with the Kyocera panels at the stern.

Building a platform to hold the solar panels.

Now that I decided the stern was the best location for the solar panels I needed a way to mount them that also gave me access to the windvane when I needed to remove the vane or check for chafe. So I started designing a mount that kept the panel as high as possible out of shadows but also didn’t obstruct the vane and allowed me open one of the panels to get access. I designed hinges between the two panels to allow one to fold on to the other.

My design sketch (top view)

View of the top facing down with the two panels mounted on two 316 stainless steel tubes with another tube going across.

My design sketch (side view)

The tubes were bent 90 degrees with bracket tubes welded for additional support. The tubes were attached both to the transom hull and the stainless steel lifelines with davit style horizontal to vertical rail clamps. All of this had to be 316 stainless steel to prevent corrosion.

Svendsens Metal works in Alameda agreed to build the tubes according to my drawings. This is the parts list I sent off to them.

A) Main supporting tubes (see side view sketch)
– Two 65″ long 1″ diameter stainless steel tubes with a 90 degree bend (ideally less than 3 inches bend radius from outer edges)
– Bend at 35″ (Top end is 35″ and side end is 30″)
– Supporting tubes welded from top end 18″ from bend corner to side end 14″ from bend corner (see sketch)

B)  Horizontal supporting tube
– One 79.5″ long 1″ diameter stainless steel tube

C) Solar panel mounting plates
– Two 24 3/4″ long by 4″ wide aluminum plates to mount plastic rail clamps

D) Attachments for the 2 main supporting tubes to horizontal supporting tube
– Four 90 degree 3 way tees for 1″ tubing

E) Brackets to mount rail clamps to solar panel at edges
– Four 4 Aluminum L shaped brackets to mount plastic rail mounts (Length 4″, width 2″, height 3/4″) (see top view sketch)

F)  Two eye ends to attach supporting “1 tubes to side deck mount

G) Two side deck mounts to attach supporting tubes eyes ends to deck

H) Six plastic rail clamps to attach solar panels to brackets/plates

I) Two davit style horizontal rail to vertical rail clamps (if you don’t have these I can order them from a davit manufacturer)

J) One 50″ long 1” diameter stainless steel tube – for additional supports if necessary

K) Four “1 stainless steel tube end caps

A few weeks later I picked up the welded tubes.

The welded tubes finally arrived

I then had to put everything together.

Drilling through stainless steel to bolt on the end fittings

I started by attaching the end fittings to the tubes. This required drilling through the 316 stainless steel using cobalt drill bits and cutting oil. Not a job for the fainthearted 🙂

Installed the tubes on the boat

I then mounted the tubes on the boat using the davit fasteners.

Installed the clamps to the solar panel frames

I then mounted clamps on to the solar panels by making aluminium seats that bolted onto the panel frames.

Installed the first panel

The first panel installed.

Testing I could get to the windvane

I then checked that I could access the windvane and install/remove the vane. It worked well.

Both panels connected to each other with the hinges

I then installed the second panel to the first using hinges.

Installed the MPPT controller

Next job was the wiring. I installed the blue MPPT controller inside the boat next to the main battery switch and ran the wiring outside through a watertight seal.

The final result! The solar panels generating electricity on the stern of the boat.

Total cost: Total cost was around $1500 for the panels, controller and stainless steel work.

Total project time: It took around six weeks. The long pole item was getting the stainless steel tubes bent and welded. Once I had that I was cooking on gas 🙂

Update in 2012 after 13,000 miles of sailing.

The solar panel and mount worked amazingly well, generating around 30-50Ah a day, and with the wind generator I only had to use the engine for charging one or twice on the whole trip (16 months).

I couldn’t believe the solar platform held up that well after 13,000 miles and all the rough weather.  After a few thousand miles I got lazy with fastening down the second panel. Once day on the passage from Bora Bora to Suwarrow Atoll, the weather got pretty rough (40+ knots and 6 meter seas). A big gust of wind lifted the second panel and closed it on the first panel violently. Luckily nothing broke, but from that day onward I always bolted down the second panel using the clamps on any major passage.


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Author: Chet

Avid sailor.

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