Solar powering your Boat

Solar powering your Boat
Current mood: nerdy

  OK so you just got really upset at the gas pump and are thinking "dang there has to be a cheaper way to go boating. YUP there is albeit you are going to move a lot slower - like down to trolling speeds.

  Now you can get a marina to do these things for you but you have to have one like Marine Dynamics or someone in your own area that is willing to do this type of work. Bear in mind though that if you have a marina do this for you it will be VERY expensive! Me, I would rather install a system such as I am about to describe by my myself I would not let anyone assist in other than minor roles. My reasoning for this is that in the event that something does go wrong out on the water I will then know how to repair it (or bypass that section) and get home.

   Now I have to actually think this through  with a particular boat in mind but the basics are:

  Solar cells - get good ones that are already intended for marine use - there are any number of them available up to 20 amps (stay down around 10) as solar battery charging systems and most seem to be designed to last a number of years if properly handled and cared for. If you are a little bolder, get a lot of the cheapie 1 amp solar battery chargers, pull the cells out and make your own big panel from several smaller ones.

  You are going to need to Diode protect all of the cells when you tie them together - do some reading, do the math is what I would recommend but you can just go with overkill size diodes across the board and call it good and probably be just as well off. Either way, go a shade heavier than what the math says or risk overheating as these will be at their full load most of the time.

 Get good wire - if you are freshwater you dont have to get as picky but saltwater get good marine wire and all cables. A nifty trick when tying in your batteries is to use 1 ought marine welding cable in place of marine battery cables - this will carry the current better, not get as hot under load and for this purpose should last as long as the boat.

  Make good connections - Solder and shrink wrap everything. Use good marine or aircraft shrink wrap with the epoxy on the inside. Put on 3 or 4 layers of shrink wrap - no point in being cheap about it; you will just have problems later on if you try to scrimp. On your batteries, use beefy terminal connectors.

   Select good batteries - There are a number of sealed gel cell batteries out there for Aircraft, automotive and marine use. What you want are monster deep cycles. You will have to play with the number of them specific to your application and make sure you have twice the batteries you need.just in case there is not enough sun to get you home one day.

   Now you have to be careful in selecting your motors to power this boat. What you are going to need are good, mid-priced range trolling motors. You are going to be replacing them every thousand or so hours or if you leave it in the water year round, count on replacing them every year or 2. You are going to have to look at the thrust output vs amp draw and physical size of the trolling motors. You are going to want to go with the ones that throw the most thrust with the least amperage draw and fit your particular boats application. Ed the parts guy at Marine Dynamics is pretty good at telling you how fast a particular trolling motor will get a boat going but here we are talking relatively unexplored territory when you start getting into multiple trolling motors. Minn Kota is about the most co-operative manufacturer. On the first call I got an old hand who called me back on his cell phone on his own time and we came up with the following scenario:

  Taking something like a new Larson 180 sport. - we figured out that 9 hp thrust with the engine in would net us around 8mph (we did not do this exact, we were just theorizing and kept all the math simple)

Rip out the factory I/O and glass in the transom where you just left that big hole. This will eliminate the gas engine altogether - might be possible to order one without an engine I dunno have to ask the Larson dealer.

 Gut the bowrider section - order it with no cushions or trim forward of the windshield if at all possible.

Use real battery boxes and make good aluminium brackets to bolt the boxes to. Make sure you bolt all of your battery boxes to the brackets - or make a whole frame if possible - go ahead and fill all the forward compartments with nitro-cellulose or composite foam, then glass them over smooth but leave the lower section down at the level it is. We figured between the floor and the seating area we could get a total of 40 mixed group 24 and group 27 sized batteries in there and still have room enough to get to things if one needed to access something to work on it.- gotta make and mount your brackets with this in mind.

Now take the whole bow section and make one big panel to go over it. We figured based on average output per square inch of the better cells (we picked some one amp units that looked like the old FlexCell Radio Shack used to sell) you should be able to get almost 300 amps at 15v from this hull with just a slight curve in the panel.

   Mounting the engines is simple if you are going to keep them detachable. Something to consider would be to cut the shafts, mount the motors themselves inside or just behind venturi tubes for a bit more thrust efficiency.

   Anyway we theorized that using 4 of Minn Kota's 2hp electric outboards you should be able to run 4 or 4.5mph and still be charging the batteries.

  I have seen a couple of solar pontoons where they had a full hard top covered in solar cells - would be time consuming but definitely enough room on pontoon boats and deck boats to get a really good sized hard top and a lot of cells up there. Something on the order of say a Ray electric outboard to get you up to a good speed of 7 or 8 knots and plenty of room for batteries - the boxes or covers for which could be made in such a way as to do double duty for seating or something. Houseboats with huge flat tops too could benefit from something like this. and on a larger craft there is room to mount a small vertical shaft marine engine with a heat exchanger and marine exhaust system with a high amp generator or alternator to charge the batteries or even run home when you are out of sun for a couple of days. Probably another thought right there.

  In plinking around I found a company out of Iowa re-making 12ft plastic "sit in" type kayaks with a completely solar cell covered top epoxied right to the original plastic and it appeared to be shaped nicely to the top of the boat. it had a shorty tiller, Minn Kota pedal control and a minnkota trolling motor mounted to the bottom of the boat with no shaft and the wires running through the hull to 8 gel cells.  Looked pretty nifty claimed top speed of 6mph with "infinite" range. They had another one that was still a kayak but equipped with Hawaiian style outriggers to both sides and monster cells mounted in the rails - it had no tiller - steering was by just the 2 minn kota's alone (kicking one back a bit or into reverse thrust type of thing). Tried to call the company, got some really nice lady who told me no.... she gets 3 or 4 calls a week for them but they went out of business like 2 or 3 years ago before she got the number.

   Got to looking at a few heavier DC motors and thinking that they might be an alternative to the gas hogs in a lot of older hard top boats. Granted you aint gonna get there quick but you have room for plenty of cells up top - or resined to your bow/fore decks in such a way that people can still walk on them without deystroying them. That big beefy engine compartment can generally hold enough batteries for a couple of days range and using the heat exchangers you already have.....you can always add some sort of vertical shaft marine engine tied to an alternator to recharge when the sun is not around (probably run like a gallon an hour tops if you do have to run it). Yeah you go down to 3 or 4 knots but you can steer by the motors or add bigger rudders if need be for better control.dont sweat the lack of speed if you are getting there for free - you can make the extra time.

   I found one company out of Japan making a hybrid sail/solar 14 foot shallow draft with a claimed tested top speed of 15mph on solar alone but the vessel is not in actual production just a prototype.

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