Solar panels - Multicrystal v polycrystal. WTF

[tuffyluffy 76]

What the difference between polycrystalline and monocrystaline solar panels?

 

I need to buy and set-up some solar panels to keep the boats battery banks topped up over winter (1 x 440Ah house bank and a single start battery). Im overseas and cant check on things as much as id like

 

My short-term plan is to buy 2, 40W panels and wire one to each bank. However, when I rummage around the marketplace, there seems to be a slight difference in price on multicrystaline Vs polycrystalline.

 

Suntech do a 40W polycrystalline for approx $7.30 per watt

BP do a 40W Multicrystaline for approx $10 per watt.

 

Price aside, does anyone know what the difference is between the different types and what is better for a boat?

 

Thanks

[Steve Pope 243]

I can't answer your question but did talk to a fellow at AA Solar,

(american / canadian) 4 bluegum Ave Silverdale, who was full of good info and seemed to have very good prices. 09 4274143.

[Grinna 2]

I hate to piddle in your beer tuffy, but it may not be as simple as just whacking a couple of panels on the boat and stuffing some wires onto your batteries. You may need a solar panel controller to get the most out of your panels (and I believe the MPPT controllers are best) and you'll probably want to wire them up to both batteries (rather than one panel to each). Without a controller you could end up frying your batteries with the solar panels.

 

You also need to think about whether you wire up the panels in series or parallel - it depends on where you mount them and how much shading they'll get, but I believe that wiring them up in parallel means that any shading will have less impact on the overall power generation.

 

As to your original question, I know there is a difference between teh two in terms of the effects of shading, but I can never remember which one is which. I *think* the multicrystalline panels handle partial shading of the panel better (less power output drop) than the monocrystalline panels, but it might be the other way round.

[Fusion 0]

I would also add. Do you really need 2 X 40watt panels if it is just to keep them topped up.

I have gone down from 1 X old 40Watt to 1 X new 20 watt with a BP controller. 750 amp hours batts with a blue sea combiner to tap across to the start batteries. If you are not running anything go small to keep them topped up. If you want to subsidizes power you need to go lots bigger to make a difference. FYI. I can run the stereo all day and the 20 watt panel will keep up.

[Farrari 4]

There is heaps of useful info on this thread here. The Google search engine works much better

 

http://crew.org.nz/forum/viewtopic.php?f=47&t=14471

 

I think there are three generic choices of solar panel

 

1/ monocrystalline (most efficient,

2/ polycrystalline (less efficient,

3/ amorphous (least efficient but can be made flexible, 6-8%)

 

From what I remember the amorphous units work a little better in the shade. The charging options are discussed in detail in the thread.

[wheels 543]

The current situation is still pretty much the same as in that particualr thread. A small drop in costs have occured in the last year. But that is due to some rather cheaper made panels coming in from China. It is such a complex industry and just because you have say a Monocrystaline for instance, doesn't mean brand X's will put out the same as Brand Y's. Even the Glass can make a difference in performance and of course, oftent he more expensive manufacturers use the better glass.

The changes in the industry is about to hit Warp speed soon. We have all been waiting for a few years now, as we hear about new technology, but nothing has eventuated. But several new producers are in the process of coming on line very soon with brand spanking new technology that will turn the undustry on it's ear. One particular breakthrough is being developed right now right here in Auckland at Massy. They have it all working and are in the final processes of refinement. The panel will not be the most efficient, providing about a 7% efficiency at the moment and they are hoping to get to 10% in the latest test, but the big difference is the technology willmean they can actually produce and market a panel at 1/10th the price of what is currently available.

The other one is also using a whole new technology and could also be cheap, maybe not as cheap as the NZ one, but the efficiency looks to be real high. So I would say changes are very close, like maybe the next 12 to 18 months. So I don't know if I would go buy any big arrays of panels right now. And certainly not go biulding a big expensive Solar powered Boat.

[Guest]

What Fusion said from me as well. You will definitely need controllers on both if you run a twin system. I'd suggest you spend the coin and get a MMTP type (Have I got that right this time Wheels??), they do put more in than the old school ones. They cost a bit more but I'm now totally convinced they give you more output per panel and for longer.

 

We use a 40w and that keeps up with everything OK inc a electric fridge, maybe excluding a huge amount of hard out large volume stereo. Haven't run out yet even with stereo going hard but I think I might if it was an all dayer session. We have 1 x 120amph battery. On a good clear sunny day the controller switches input to the battery off before mid day as she's full and that's after some heavy use. Mind you I have also tuned the boat to be a low power user.

 

And don't forget a 40W panel is actually a 50W panel when used in NZ. Why I hear you ask?

 

All solar panels are 'rated' at the world average of 1000 sun bugs* hitting per square meter of ground/solar panel. In NZ we average 1250 sun bugs per square so a panel rated at XX Watts is actually working at 25% above that in the Hauraki Gulf.

 

* - No ides what the techo word for sun bugs is. Space bugs, Space rays, exhaust rays from the mothership, maybe Light bugs or probably some boring no fun name.

[Guest]

Sunshine?

[Guest]

Sunshine?

I was going to say that but it just didn't sound technical euff.

[wheels 543]

If ya wanted to get all nerdy technical, a Sunbug would be called a Photon. Lots of them hitting the Earth, your face or your solar panel is measured in Joules of energy.

[Guest]

Didn't Capt Kirk take out dodgy Klingons using Photon Torpedos?

 

Must be pretty cool yet pretty serious thing those Photons.

[tuffyluffy 76]

Thanks heaps for the feedback guys - i guess the jury is still out on which type of panel is best.

 

A controller is definitely part of the plan - ive just found a nice two bank unit that should do the job of charging the start batt first then switch to the house bank. The idea of two 40W (or 50W as Knotty explained) was to firstly maintain the batteries while im away, but also provide some juice when cruising so i dont have to start the donk as much. If 80W/100W doesnt keep on top of the laptop, fridge, stereo, and auto-pilot, it wont be to hard to add another few panels into the system.

 

Interesting info on the panels Wheels, unfortunately, like most things, the product wont be avaialble when i need it - Now!

[Guest]

I have a 5W panel to keep my batteries 'up'. Over a good week of sun and now running thru the controller that panel will top the battery back up from a Sunday arvo race/booze cruz. We only put the big panel aboard when off for a cruz and don't have the big motor on, which has charging facilities.

 

I think I have a BP monocrystalline. The BP I am sure about it's the other I'm knot.

 

I think amorphous are the best but they are large in size in comparison to the other types. I also think getting a good controller can make a BIG difference to the net battery input. I do know positioning a panel can also make a huge difference. Lying one flat in the full sun is good but angle it to 36 degrees and you get a lot more. The 36 degrees bit being the angle a panel works best at when at 36 degrees of latitude.

 

So from what I see on boats I'd be thinking there are probably more efficiencies from positioning and in how it's connected to the batteries to be made by 'the fleet' than there is swapping from one type of panel to another.