Solar panel technology is a fast moving area, but as of today in 2023 there are two types of solid panels as well as flexible panels that are available for boats.
Solid Monocrystalline & Polycrystalline Panels
Monocrystalline are the current premium panels, they are made from silicon that is formed into bars and then cut into wafers. Monocrystalline can be identified as the surface looks dark and uniform, these are the most efficient of the main panel types.
Monocrystalline are around 20% efficient, in that they can convert about 20% of the energy that falls on them into power.
Polycrystalline are cheaper and less efficient, they are made by melting fragments of silicon to form wafers, they can be identified due to there blue speckled look.
Polycrystalline are around 14-16% efficient, in that they can convert about 15% of the energy that falls on them into power.
These silicon solar cells are placed between protective layers and bonded together in a similar way to the laminator you use in the office but on a much greater scale and higher heat, the quality of the encapsulation and material used in vital to the life of the panels. To finish the panels a frame is added and this is also carefully bonded to the now laminated panel with the wiring often via a flying lead with an MC4 connector already attached.
There are many other solar technologies that are yet to make it to the marine market either due to lower current efficiency or higher costs.
Flexible & Semi-Flexible Solar Panels
These are getting more common on boats and as it is a popular option on narrow and wide beam canal boats to have a curved roof. Made with a printed photovoltaic material or a fine Monocrystalline solar cells. Flexible panels are both lighter and robust once fitted and can be walked on, they do however have a shorter lifespan and are less efficient that they’re solid counterparts at between 10-15%. The cost in greater per Kw and also need to be glued to the roof, which can be a problem of you damage one or need to repaint, it also makes them impossible to tilt for optimal performance in poor light conditions.
Flexible panels would be a good option for us if our boat was newer with a more stable roof paint layer as we could cover much more of the roof with them without loosing any visability or access to the roof.
Our selection at the moment is still the Monocrystalline 415W Perlight Delta panels on the tilting mountings at the moment, but we will have a bit to investigate.
Over the past few years we have looked at a lot of solar panel mounting systems, the major problems on canal boats seems to be that the roofs are curved, they are then also covered in vents, ropes and storage for poles, and planks etc.
While we are moving the boat we want as lower profile as possible so we have a good clear view ahead without having to worry about low bridges etc . Our current mooring is near the fearsome M5 tunnel on the Droitwich Canal, which on a bad day, looks like it can scalp anything off the top of your boat.
All the systems we have seen are compromises dependent on the design of your boat, the design/size of your panels and layout of your roof.
Types of Solar Panel Mountings
Flat Mounting systems
Flat solar panel mounting systems are fitted directly to the roof of your boat they are probably suited to boats used in the summer months are the sun is more directly overhead.
These are the simplest to install, the most basic are ABS plastic corner mounts, that are fixed to the panel and directly to the roof. If you have a curved roof you will need mounts that lift the panel at each side high enough to clear the curve of the roof. They are probably best suited to narrow panels along the centre line of the roof.
Solid ABS-plastic Solar Panel Mounts
For long panels additional side mounts are recommended to keep the panels rigidly fixed, the example about is very common, this example comes from Sunworks UK.
Raised Solar Panel Mounting
There are may other flat style mounting, some are made of aluminium extrusion, but if you have a curved roof you will need to make sure they hold you panel high enough to clear mushroom vents and that dreaded rood curve.
Flat mountsare probably adequate in the summer with the sun overhead, but we planing on staying on our boat all year around so I have been investigating being able to tilt my panels.
I found this solar mounting on a boat in our marina, it is home designed by the boat owner, the adjustable feet have a ball joint and are bolted into the roof with a waterproof tape in-between, then an aluminium extrusion runs the length of the panel increasing the mounting hight and also adding signification strength to the panel, that can tend to flex under their own weight.
As you can see a lock nut holds the panel up and another clamps down on the aluminium this enables the hight to be adjusted. The owner also recommended a slight tilt from to back on the panels so that rain water did not collect on the panels.
The panels are then bolted to the aluminium extrusion , there are 6 of these mounting on each panel, making them very secure.
A lot of the advertised tilted panel systems come from the camper van market where they are often placed on the ground and turned to the best position, most of the ones I have seen and not designed for roof mounting and have a fixed tilt or only tilt to one side, not ideal for mounting on a boat roof.
One of the easiest and most common boat tillable mounting systems are these aluminium triangles, that allow some angle to be set and can adjusted to each side of the roof , while use with thin panels means they can be angled well it is not ideal for wider panel as the width of the panel makes it harder to get the correct and most efficient angles in the autumn , winter and spring (see chart below).
The ever popular triangle solar panel mounts
One of my favourite YouTube channels Minimal List modified some mounting to enable them to be used on the curved roof of there boat while also allowing them to be tilted to either site, I initially like this method, but further research and I think I have found and even better solution.
Minimal List Curved roof solution.
Probably for me so far the ultimate tilting panel mount comes from Midsummer Energy
May be the ultimate solar panel mount from Midsummer Energy
As you can see these mounts are not worried by the roof curve and have can be set at a very high tilt angle, ideal for all year round use, I have even seen these tilted front to back to a limited amount.
Have a look at a YouTube video from Never Enough Cruising to see them in action
Never Enough Cruising Solar Panel Setup
Why tilt your panels
Solar Panels work best when light from the sun hits them at a 90 degree angle, else as the angle gets near to 0 degrees the suns rays are reflected and bounce off the panel and are lost. Effective tilting of the panels can increase efficiency by upto 50%.
Over the year the Sun will be higher in the summer and lower in the sky during winter, using the example of Birmingham, as our boat is moored near there, I created a table of the optimum angles to tilt your solar panels during the day for the best power output.
Note:This could be still improved if you change the angle during the day as the sun is much lower in the sky in the early morning and late afternoon.
January
60°
February
57°
March
51°
April
43°
May
33°
June
27°
July
27°
August
33°
September
43°
October
51°
November
57°
December
60°
This table is based on the assumption that the solar panels are facing south and are not affected by shading or other obstructions. The optimal tilt angle is based on the latitude of Birmingham, which is around 52 degrees north. As you can see, the angle changes throughout the year to capture the most sunlight based on the sun’s position in the sky.
Note: Mounting your solar panels and galvanic corrosion
Galvanic corrosion is an electrochemical process where one metal corrodes in preference to another metal when it is in contact with through an electrolyte. The electrolyte is our case is dirty water. The metals are the steel roof and the aluminium solar mountings or the bolts that connect them.
You can minimise this corrosion using a painted finish, or by using non-metalic/rubber washers and or even a layer of sealant, like Sikaflex 291i Marine Adhesive & Sealant works well I am told and will be what I am using to seal/stick down my mounts
This seems to be the biggest problem we have is knowing when the tank is nearly full, we know. when it is full the the toilet will not flush away.. but that always seems to late and always always after we have passed a pump-out point a few miles back.
Most Basic Flush Counter?
So I have looked at sensors I can add to the tank, sensors that need to be put in the tank seem to be a bad idea, I would have to make a hole in the tank to fit them and anything floating in poo is probably not going to be reliable for long.
I have looked has ultra sonic style sensors, but most of these do not like a stainless steel tank, or are extremely expensive.
So our current solution is as simple as it can get, we know the rough capacity of the tank 545 litres , and the volume of a flush is 4 litres, if we add a little extra for the solid and liquid waste 1 litre, we can estimate the number of flushes we can do before we get to ¾ full. NOTE: These are estimated volumes based on the manual we have, we also have to remember a pump-out is never 100%, there is always some residual waste left in the tank.
We are hoping in a couple of years to take a gap year! all out kids will have either left home or be at Uni, so time for old’s to go on an adventure. To enable us not to have to run the engine to charge the batteries, we are looking at solar panels.
On our latest trip to the boat I took some measurements of the available space on the roof that we could use for solar panels, we cannot use the area behind the centre line point as we have ropes and mounting for the pole, boat hook and our plank.
I have been looking at large panels that can deliver 400+ watts, this make the roof more difficult to walk on, but with just two fitted we can still layout on the roof and watch the stars and we don’t tend to walk on the roof, the knees won’t take the jump down.
This diagram is based on using two 415W Perlight Delta panels, which are 1719mm long x 1140mm wide and 30mm thick. I am hoping that a combined 830W will give me enough power in the summer, while providing some still usable power in the winter (More on my calculations in a future post).
We currently have two 12v TV’s (not often both used, but one in the bedroom and one in the lounge) , a 12V fridge, 240V washing machine, a hungry 3500W inverter, LED Lighting, water pumps, internet wifi/router, laptops and phones and about 400 Ah of lead acid batteries, so about 200 Ah usable power (an upgrade to Lithium will come one day).
We want to plan ahead and have more supply than we currently need, hoping to cover us for future needs and upgrades.
Next I want to find mountings that will go as low as possible, but still enable us to angle the panels for better output, especially in winter when the sun is low to the horzion.
A couple of weeks ago we visit the Marina fit more new curtains and measure the roof to find the best options for solar panels. Unfortunately we found the toilet was not working as expected, it would flush, but after flushing there would be more water in the bowl that expected, and after a second flush it would increase again.
We tried cleaning the toilet and using a plunger to push the water into the tank, but we could not resolve the problem and so had decided put it off to another visit, when I would have more time and tools.
On the way home I decided to texted Steve Cowham, who had come to our rescue fitting the water pump in the summer, I have poorly thumbs and am trying to save myself from further operations, luckily Steve was able to take a look and soon called me back.
His suggestion was that the Macerator Pump had probably worn out, having been an X-Black Prince hire boat for 12 years, it would have been well used. He was happy to fit one for us and recommend we order one from Midland Chandlers the part we needed was a “Tecma 12V Silence / Elegance Macerator Pump” part number TG-224.
This was ordered and shipped directly to Steve via the marina, at £249.50 they are not cheap, but they need to work.
A few days later it is all fitted and working, we will be back to the boat soon and I am sure we will be testing it.
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