Hi Mark,
I have found that the best solar array is mounted on a pole that can turn with an arm that can lift so the panels can be directed at the sun. At dawn and dusk, this can improve solar performance by as much as 10 x, so any effort you make to pivot the panels will have a great improvement in performance. The two panels that are installed on Kapowai put out 20 watts when horizontal, after aiming them at the sun at dusk, they put out 200 watts.
The panels that I put on Kapowai are 225 watts each putting out a total of 450 watts. I am planning on selling this array and replacing it with a 680 watt array using two Sunpower 340 watt panels.
Kapowai can solar sail at up to 3 knots in calm conditions as long as the sun is shining.
Windage on panels is an issue, but by being able to adjust the panels to horizontal you can largely minimize windage. You can also fold the two panels together to decrease windage even more.
We choose two panels that have an output each of 42 volts to get a total of 84 volts at peak power. We then shift this voltage down through a solar charge controller to charge the 48 volt battery pack at 58 volts. The mppt circuitry really helps as solar panels are constant current devices and if they are clamped down to the battery voltage then the power output is clamped down to, whereas if the solar panels are allowed to float up to maximum power, you can get a 20% increase in the output of the panel.
The panels are in series so if one is shaded it affects the output of both panels. This is important to consider on a sailboat with a tall mast so you may find output is increased if you put your boat in your slip stern first. Also shading can be affected by the masts on neighboring boats.
Here's a link to the page that shows a picture of the panels.
Cheers,
James
James Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
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