Power generation from the sun is one method to increase independence from shore facilities. We have built our solution over 10 years.
Starting with the first Maringret electrical power became a limiting factor when away from shore power. We installed solar panels which we had for over 10 years. They were then moved to the second Maringret and increased.
With our first boat we were marina based and the charging by the engine was sufficient for our sailing needs. As we ventured further and for longer we started to face battery depletion. We had three options:
As opposed to wind power, solar power installations had changed relatively little over the period we have had the boats. The power density (i.e. the amount of power collected per square meter) has changed little. Maximizing solar power collection basically comes down to maximizing the amount of space dedicated to it. One development was the flexible solar panels that can be fitted to a curved surface (e.g. coach house or deck) and can even be walked on (with care). But although more robust than the flexible panels the output is much less so they do not enter into the search for increased solar power collection.
There are a few major differences between collecting wind and solar power:
- wind generators are almost always fitted on swivels so they rotate to face the wind;
- solar panels are almost never mounted on swivels and so must be oriented to face the sun
- as the wind generators rotate themselves into the wind using their rudders they always get 100% effect from the wind (also the flow of the wind tends to be parallel to the earth’s surface);
- solar panels must be faced to the sun but also need to be at 90 degrees to the sun’s rays in order to get 100% effect from the sun (the sun’s rays are anything but perpindicular to the earth’s surface as they change through the day and through the seasons)
- wind shadows affect wind generators less as the momentum of the wind generator will tend to smooth out any variations;
- shadows on solar panels can shut the complete panel down and must be eliminated
The points above probably make solar panels look as more trouble than wind generators. In some ways this is true but once a solar panels is set up it will continue to function silently as long as the sun shines. There is always noise (and danger from moving parts) involved with a wind generator but neither are part of solar panels.
The sun follows a curved course across the sky, for example the winter course will be much lower in the sky than the course on a summer day. To properly follow this the mounting for the solar panel is best to rotate in 2 axis (known as 2 degrees of freedom). Now obviously a totally fixed mounting will just have to try and find the best compromise for a mounting angle. After that is the most common mounting on boats which is a horizontal pole which the brackets holding the solar panels rotate (1 degree of freedom). This is good as the panels can be adjusted to track the sun as it crosses the sky. But there is no option to track the sun as it tracks through the seasons – the second track will be at 90 degrees to the daily track. Without a second hinge to allow the horizontal pole to be changed from horizontal the capture of solar energy can not be maximized.
We initially mounted our solar panel on a 25mm tube pushpit on the Maxi which gave them 1 degree of freedom. This system got moved to the HR 41 where they were mounted on 25mm tubes welded onto the top of the davits. Over the next few years we started to notice that as the seasons went by and the track of the sun across the sky got higher or lower then the panels could rotate to follow the sun’s track but not the azimuth of the track as the track rose and fell across the sky. We ended up having a hinge welded into the aft end of the tube and then prop up the free end to allow the panels to track the both the sun’s track and the azimuth of the track.
We have seen an alternate mounting system on other boats: the panel is mounted on the top of a vertical pole. The panel can then be tilted from near vertical to near horizontal as well as rotated 360 degrees. We have only seen this on 50W panels as larger panels would create a lot of wind resistance if they were directly facing into the wind.
- the more solar panels the better
- solar panels cannot tolerate any shadows falling on them
- airborne dust accumulating on the solar panels will gradually reduce their output
- solar panels need at least two degrees of freedom to track the sun – three degrees is better if feasible
- very high clouds can decrease the panel performance more than one would expect.
The panels have been with us for 10 years and are still working as well as the first day. We wipe them off each morning using the dew from the night, this keeps the dust from building up on them. Once we added the second degree of movement onto the panel mountings greatly increased the amount of solar power collected across the year.
As of 2016 our Air Breeze wind generator had started having bearing problems and so we took it out of service. We doubled our solar panels from 150W to 300W and have basically not missed the wind generator since then. Of course, Maringret is presently in an area with extensive sun and erratic intermittent winds.
With 300W of panels and 750 amp-hours of batteries, we can not capture in the batteries more than a fraction of what the panels collect each day. We are trying to construct a water heating system so at least the energy could be used to heat water for the boat.
One important thing we learned, and something that is not stressed heavily in anything we have read, is the importance of regulators with solar panels. Keeping the panels clean and oriented towards the sun are very important first steps. But after that has been seen to, the collected energy heads down the wires to the batteries. This is where a big difference can be found between poor and good regulators. We have gone through 3 regulators as well as comparing notes with other boats. The best we have found by far, are the FlexCharge regulators. How they achieve what they do is fairly technical and best read on their website. But the difference in actual charge received by the battery (as opposed to power collected at the panels) is noticeable and measurable. We have used them for both wind and solar sources.
- FlexCharge charge regulators
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