Solar Panels - Which Ones

[Jonny_H]

Looking to get a solar panel to add to the wind genny we currently have to keep the batteries nice and topped up.

Have done some sums and think we need something in the 100W region.

Next question is why is there such a big range in price? Monocrystalline vs Polycrystalline?

Seen this on ebay which seems quite cheap - but is it any good. It has a 25 year output gaurantee.

This is also on the list of potentials - but for the extra money is it significantly better than the one on ebay??

(Cruising from the UK to Oz leaving next year - so should be quite sunny for most of the trip!)

Any advice much appreciated!

Jonny

 

[fluffc]

Have a look at this - http://www.midsummerenergy.co.uk/solar_panel_information.html on the midsummer site; more technical information about the differences.

A friend of mine, Andy, runs this company. He has a good deal of first hand experience of solar panels in use, so should be good for advice. Contact via the website.

 

[mandlmaunder]

Several things to keep in mind when buying solar panels-
is it marine grade materials?
all stated out put is optimal i.e lab speck conditions, the best results from real operation come from mounting on automated sun following motor driven gantries-
solar panels only work at close to optimum 11am-1pm at the equator, the rest of the time output is greatly reduced by time of day and degrees away from the equator-
I found that to double solar panel stated output of manufacturers speck will get you into the ball park of your requirements i.e if you decide your reqs are for 100watts to cover your usage you will need 200watts of panels.
your power requirements go up the hotter you get -refridgeration will increase dramatically -fans -lights(longer nites)-charging and running of toys(ipod - cameras ect).
within reason you can't have too much power if you liveaboard and your panels are properly monitored/regulated.
good luck, if you ask20 people this question you will get 18 points of view.
Monocrystaline or Polycrystaline, rigid or flexible. The technology improves almost monthly .no one admits that their product is not state of the art. Contact a few Eco -power web sites for latest info.
We left England 5 years ago having done a first rate job of research (i thought) and have upgraded twice .

 

[HoratioHB]

For what its worth I posted a few days earlier on this - a basic calculation to estimate the current from a panel is:

Watts times a factor divided by the panel volage = amps in a day.

For UK the factor is 4, for the Med use 5 and the tropics 6.

have a look at Plastimo 80w panels they are marinised and have special mounts that allow you to alter the angle to track the sun - they are also quite small 1.2x0.5 meters - ish.

 

[jeremyshaw]

Another issue to consider with solar panels is partial shading. As I recall the general rule of thumb is that 10% occlusion leads to 90R% power loss. So:
a) positioning is crucial
b) a number of smaller panels can work better than fewer big ones

Some types of panel cope better with a bit of shading than others. We went with uni-solar because their technology responds better in slight overall shade (don't press me for the details as it was a few years ago that I researched this).

And finally, ironically, solar panels work less well the hotter they get!

Would not be without them however. Nothing better for float charging, noise free, maintenance free.

 

[Jonny_H]

Thanks for all the useful info. I had wondered about getting several smaller panels (3 or 4 30W for example) and spreading them around the boat (a couple on the gantry, one on the aft rail, one on the coachroof etc) rather than one large one but didn't know whether it would be better?

I will give the guy at Midsummer a call (he had given me details on the 80W panel I linked to above) and discuss some more.

I know the more power the better, but we have an Aero4gen (would have preferred a 6 but the boat already had a 4 so not much point in changing it), and are happy to run the engine for a few hours to keep the batteries topped up. Also planning on getting a small (1Kw) generator to use as a back up for charging and to run power tools etc. It just comes down to cash though - would love to get 300W + of panels, but with a Hydrovane also on the 'to buy' list and fitting the SSB coming shortly the budget is somewhat strained, I was therefore looking at sub £500.

Jonny

 

[michael_w]

I used to have a free range Uni-Solar 32w bendy panel. With a bit of effort it was always kept pointing at the sun. eg: underway, hang it off the guardrails, at anchor, stick it on the coach roof, on top of the awning, or off the backstay.

Excellent bit of kit, shame they aren't made anymore.

 

[Guest]

Make the panels fixed or slightly tiltable. If it takes longer than 30 seconds to alter, forget it. Highest efficiency possible and out of the shadow of booms etc.

Any messing around or temporary fixtures just mean they will be stolen or broken or ignored.

Having the panels do their work while you are walking around a bay or town exploring is the most satisfying feeling. Having full batteries every night is so much better than racing home to run the engine for an hour before the neighbours start shunning you.

As for mini generators AHHHHHH!

 

[Jonny_H]

Thanks Neil - I had wondered about making them adjustable, but thought it would be easier to have them fixed on our gantry.

As for the mini generator - agree its not a good long term solution, but for the cost involved we thought it was a good backup to have on board and run the odd power tool.

Thinking that 4 x 25W Panels may be the way forwards to reduce the effects of shading on output

Jonny

 

[Guest]

I like these best: (Can not get them yet!)

http://www.sunpowercorp.com/homeowners/panels.html

These are easy to manage

http://www.a1solar.co.uk/sm55_sm50.html

only 13" wide and use nearly fully squared off cells. Make sure they are the 55W ones with 36 cells. Not 50W or 32 cells.

 

[Jonny_H]

The SM55's look quite good - can't find any prices though! How sensitive would a charge controller be to wattage - mine will handle 100W, would putting two 55W panels through it be dangerous (I assume not as you would rarely get full capacity from a panel?)

Jonny

 

[Robin]

We have a Siemens 75w panel inherited with our boat and fitted flat on our stern gantry, it is probably now 10 years old and works very well. Slight 'design' problem from previous owners because the Aerogen 6 and the radar scanner are also on the gantry and can throw shadows over the solar panel. The beauty of the gantry mounted panel is that it is out of the way and useable at sea in any conditions. We also have a Solarex 110w panel also solid framed aluminium that we bought for our last boat and kept, it is stored below and brought out when needed. We can plug the 110w panel in to either of two sockets in the cockpit depending on which battery bank we want to charge and at anchor we lay this to one side or other of the coachroof, laid flat is fine at least in UK/Western France, and we move it to avoid shadows at most 2-3 times per day.

We have ammeters on both panels as well as the Aerogen so can monitor what goes on. Shadows are bad news! The panels still work with a shadow across them but the output drops considerably with any significant shadow. Yes the output is at maximum aroun solar noon but in practice where we sail they are working from around 8am to 7pm in July/August. The moveable 110w panel can really put some power in and we have often had to unplug it as the volts were getting a bit too high even after 5 days of big (210L) fridge running etc.

We had an Aerogen 4 on our last boat which was mounted on the pushpit as it was on a ketch. It worked fine when we were on a mooring and kept the batteries well up but it was masked by the sprayhood so that if this was up at anchor the Aerogen output was poor.

We have an Aerogen 6 on our current boat and that can put out serious amps in a good wind. BUT we look for anchorages that are protected from wind! Theoretical output is not always matched in practice as the Aerogen 'hunts' the wind when the boat swings or the wind shifts, occasionally stopping and restarting. In harbours with buildings or other structures around the swirling winds mean the Aerogen is maybe less than 50% efficient.

Mostly these days our maximum time at sea per trip is 24hrs and we can manage that anyway without any charging of any kind, so unless we left with batteries less than 100% will not bother to untie the Aerogen, but will switch on the fixed solar panel. With full batteries we can go at least 3 days at anchor without charging, so what is brought into play depends on the initial state of charge and how long we plan to be there. Usually the fixed panel is switched on and if we are staying more than a day or two will untie the Aerogen and get out the big panel but first to go off is the Aerogen, it isn't noisy per se but still the fan can sound like a 747 landing in a big gust and you find yourself looking round for it!

Personally I would forget flexy panels altogether. A plethora of small panels will cost much more than one big one of the same total output and might only be better at sea when a big moveable panel might be stowed. Better charging at sea would come from a towed water generator, the Aerogen will work but downwind will be fed with lower windspeed and output will be reuced.

If you get a small petrol genny, don't rely on it to charge via it's built in 12v output which will be pathetic, you need to run it through a smart 220v charger. However some chargers will not run from a small generator as they are not 100% efficient in converting 220vac to 12v DC. We have one we used to use on our last boat but had the charger de-tuned to 'just' run from the 800w genny without flipping it's trip, in practice the 30A charger ran at about 24A. On our current boat our now 40A charger can be switched down to 75%/50%/25% power so it will run from the genny but we don't even have it on board these days as we have enough charging potential without it.

More food for thought in your decision making!

 

[Guest]

Depends: Cheap ones will probably never actually make it. But commercial ones are specified as worst case after a certain time. You have to do the research. But in general the first step is to get a lot closer to the equator! Ours have definitely made it past their ratings by 10% or so.

http://en.wikipedia.org/wiki/Image:Solar_land_area.png

 

[Jonny_H]

Great pic - thanks. Looks like our route to Oz via the Panama will be nice and solar rich once we get past the canaries!

Been recommended some Kyocera panels which look quite good. See what you mean about output (the one I saw was rated as x Watts +15% / -5%)

Kyocera ones look good value - will have to do some more digging on the Siemens ones and prices.

Thanks

Jonny

 

[wanderlust]

I have 2 Unisolar framed panels of 64 watts each. Compared to other manufacturers these panels are large for their output. They do however, put out lots of power in poor sun light conditions. I know this as I also have two 40 watt panels that are a lot smaller for their output. I have these on flying leads that clip to the guard wires so are portable and tiltable. I dont need the extra panels in the uk summer for charging as the two large panels provide everything we need. We have a fridge/freezer, autopilot, radar, etc, and have no problem keeping the batteries well charged.