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Old 14-03-2014, 10:47   #1
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Practical aspect of sizing solar panels?

I've looked at a couple of threads regarding sizing solar panels that mostly seem to focus on output vs demand but it occurs to me there are other practical considerations involved with the installation, namely how much weight and windage do people really think is acceptable for a typical 40' cruiser?

When I look at my cockpit arrangement as well as my sails and rigging and try to imagine fabricating an arch to support my future solar panels I can't get past thinking two 150 watt panels are about as many as would I want to try to put up there.

So the question is how much wattage can you comfortably fit on any given size of boat?
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Old 14-03-2014, 12:27   #2
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Re: Practical aspect of sizing solar panels?

My bioat is 43' OA and 41' on deck and 300W is "practical"far as I'm concerned. I have 290W and is was enough to run my refrigerator all week while the boat was out on the mooring and to maintain the systems when in use (even during weeks when it was overcast and rainy my batteries were fully charged when I showed up on Friday night). I figure that if I would to sail for days (because more power is used underway than at anchor/mooring) that every few days I will need to run the engine a couple of hours, or run the Honda gen, to catch up.

My boat is in Massachusetts and I'm always wonder what people living in sunnier areas are doing to need 600W.
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Old 14-03-2014, 14:18   #3
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Re: Practical aspect of sizing solar panels?

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Originally Posted by sailorboy1 View Post
I'm always wonder what people living in sunnier areas are doing to need 600W.
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Originally Posted by sailorboy1 View Post
My boat is in Massachusetts and when I showed up on Friday night
I think the answer to your question is in part of your post. Living abaord full time in one of those sunnier areas that is also hotter is a whole different power use profile than showing up on a Friday and having full batteries for the weekend.

It happened to us and it keeps our dealer in La Paz, Mexico quite busy doing solar installations and upgrades when boats from WA, OR and CA go to Mexico with what we/they through was enough solar based on our time in northern climates.

In four years of talking to cruisers over drinks, there are three things that almost all cruisers wish they had more of:
1) Power IE-more Solar
2) Water IE-not enough production from their low output 12v water maker
and
3) Time IE more time out cruising before some had to go back for what ever reason.

If you think you need 200W, find room for 400W and you just might make it! We live aboard with 420W of solar and I have plans in the works to expand that to 980W!
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Old 14-03-2014, 15:04   #4
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Re: Practical aspect of sizing solar panels?

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Originally Posted by SV THIRD DAY View Post
If you think you need 200W, find room for 400W and you just might make it! We live aboard with 420W of solar and I have plans in the works to expand that to 980W!
Or in other words, if you want more power get a bigger boat? I see you are on a fifty footer, would you say 980W is the practical limit for your size boat? Are you maxed out?
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Old 14-03-2014, 15:27   #5
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Re: Practical aspect of sizing solar panels?

Its not a sailboat so take that for what its worth. But we do have some serious experience with solar - we've got a converted bus with 200 watts on it and our 43' trawler has 700 watts. When we did the bus solar panels were about $7 per watt so 200 watts was a serious investment. Last year when I did the boat solar was down to $1 per watt so we spent less than 1/2 as much and got close to 3x the capacity. As the previous poster said, solar is like sex - you can always handle more. The first step in any successful solar power upgrade is to figure out how to reduce your existing consumption - LED bulbs, propane galley, insulation - a watt is a watt - whatever you can do to decrease your consumption of watts will make the eventual solar installation more successful.

I was very concerned about windage from the panels. I ended up replacing our existing canvas bimini with what amounts to a hardtop consisting of 3 x 230 watt panels. Several people have said - unaided - that it looks good so I guess I got it right. Or maybe they're all just suck-ups. I don't know how you could compare pre and post windage but I can't say that it seems any better or worse. I don't see any practical way to get more wattage on this boat but as I said initially, it is after all a stinkpot to begin with.
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Old 14-03-2014, 15:30   #6
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Re: Practical aspect of sizing solar panels?

Quote:
Originally Posted by Delancey View Post
Or in other words, if you want more power get a bigger boat? I see you are on a fifty footer, would you say 980W is the practical limit for your size boat? Are you maxed out?
I think it goes to the definition of "practical" vs "convienient".
We had a 36ft boat and had 260W which we though was a lot of solar and maxed out our space. Then we got out cruising and found 260W lacking and after seeing how other mounted panels realized we could have added another 260W easily by mounting them on the side rails around the cock pit. Now some view the fold up/down rail mount approach for solar panels as ugly, or windage, or unsafe, or you name it. I bet I could fit 2-140W panels easily on most boats if they really wanted it. It may not be the ideal location but on a 40ft boat...you really can't find room for 2-more 140w or even 2-85w panels?

Right now my 420W is all mounted on the pilot house roof...not all ideal because I do get some shading (2-125w and 2-85w) but EVERYONE with a sailboat gets some shading, so you just do the best you can. I like the pilot house roof becasue it doesn't change the "look" of my boat at all because they are barely visable. The 4-140w panels I'm in the process of adding now will all be fold up/down rail mounts, two on each side. If I need more then I can easily add another 2-140W-ers to the top of my dinghy davits and that would bring the total up to 1260W...which honestly I think would be my Max Out point without going totally crazy and overboard....but then again...a Hudson Force 50 is already crazy and overboard...

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Old 14-03-2014, 15:50   #7
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Re: Practical aspect of sizing solar panels?

Quote:
Originally Posted by Delancey View Post
I've looked at a couple of threads regarding sizing solar panels that mostly seem to focus on output vs demand but it occurs to me there are other practical considerations involved with the installation, namely how much weight and windage do people really think is acceptable for a typical 40' cruiser?

When I look at my cockpit arrangement as well as my sails and rigging and try to imagine fabricating an arch to support my future solar panels I can't get past thinking two 150 watt panels are about as many as would I want to try to put up there.

So the question is how much wattage can you comfortably fit on any given size of boat?
Just rethinking my solar this week overall as the result of a panel failure & one thing I would do differently is select SMALLER panels to make up the array to ensure more support across the glass. Glass is not broken but the question of flexing came to mind. i.e. 100 W panels V 200 W panels. There is at this stage no proof the larger panel failure was due to flexing just my thought. Yes the rule of thumb is double the wattage you think you need.
(The flexable thin panels maybe best for moving platforms)

Regards Bill
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Old 15-03-2014, 00:52   #8
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Re: Practical aspect of sizing solar panels?

I've been doing a lot of scheming, and I think I will eventually buy a Leopard 45 or 47.

According to my calculations, I could install 7 panels (39"W x 60"L) across the back, on top of a sturdy arch over the dinghy. It would be tied into the roof, at least 2 points on the outboard side of each hull, and 1 or 2 locations on the inboard side of each hull. These would be 275-300w 24v panels.

If that isn't enough for the watermaker, 2 freezers, etc, I'd also like to install 3 fold down panels outboard of each hull, mounted to the safety railing and supported by 4 struts from the edge of the deck out to the outer corner of each panel. Assuming these are also 275 - 300w panels, the grand total should be 3575 - 3900 watts. This should allow a fairly comfortable living arrangement with electric cooking, entertainment, watermaking and fridge, 2 freezers, ice maker, etc. The current plan is to run each panel to it's own MPPT solar controller, with maybe 3 or 4 spares on board. This way each panel will get the max. harvest even under partial shading without affecting others, like parallel or serial wired strings. This will all feed 2 large 24v LiFePO4 banks, one in each hull. By running the watermaker, washing machine and other appliances during peak sun if possible, we use solar energy and minimize night time loads.

This is all just wish list stuff for now. Yes, it will be heavy, Yes, it will have some windage. It might be fairly ugly, although I'd try to make it look as good as possible. My dream is to find remote atolls and secluded beaches and hang out for a week or two at a time, with minimal generator hours and maximum comfort.
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Old 15-03-2014, 03:28   #9
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Quote:
Originally Posted by SV THIRD DAY View Post

I think it goes to the definition of "practical" vs "convienient".
We had a 36ft boat and had 260W which we though was a lot of solar and maxed out our space. Then we got out cruising and found 260W lacking and after seeing how other mounted panels realized we could have added another 260W easily by mounting them on the side rails around the cock pit. Now some view the fold up/down rail mount approach for solar panels as ugly, or windage, or unsafe, or you name it. I bet I could fit 2-140W panels easily on most boats if they really wanted it. It may not be the ideal location but on a 40ft boat...you really can't find room for 2-more 140w or even 2-85w panels?

Right now my 420W is all mounted on the pilot house roof...not all ideal because I do get some shading (2-125w and 2-85w) but EVERYONE with a sailboat gets some shading, so you just do the best you can. I like the pilot house roof becasue it doesn't change the "look" of my boat at all because they are barely visable. The 4-140w panels I'm in the process of adding now will all be fold up/down rail mounts, two on each side. If I need more then I can easily add another 2-140W-ers to the top of my dinghy davits and that would bring the total up to 1260W...which honestly I think would be my Max Out point without going totally crazy and overboard....but then again...a Hudson Force 50 is already crazy and overboard...
I strongly recommend that you avoid putting the panel's on your Rails. If they're out of the way for easy movement they're very susceptible to damage whether docking or having some idiot drag in to you. Also more susceptible to salt spray. To me biminis are the ideal place. Second choice would be davits. Third choice would be on the house. 4th would be an arch. To OP the reason the arch is last is because it adds windage and cost. As far as the other positions for panels go I think the windage is minimal and the weight is not really a consideration on a 40 foot boat.
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Old 15-03-2014, 04:02   #10
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Re: Practical aspect of sizing solar panels?

I have about 500 watts of panels and 1,000 amp hours of batteries, I have this much so that I don't cycle the batteries down too low and they last longer. If you don't want lots of panels don't have lots of storage and cycle the batteries harder and replace them more often. It's all compromises and balances.
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Old 15-03-2014, 05:02   #11
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Re: Practical aspect of sizing solar panels?

Quote:
Originally Posted by bill good View Post
Just rethinking my solar this week overall as the result of a panel failure & one thing I would do differently is select SMALLER panels to make up the array to ensure more support across the glass. Glass is not broken but the question of flexing came to mind. i.e. 100 W panels V 200 W panels. There is at this stage no proof the larger panel failure was due to flexing just my thought. Yes the rule of thumb is double the wattage you think you need.
(The flexable thin panels maybe best for moving platforms)

Regards Bill
Interesting point about the smaller panels I hadn't considered.
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Old 15-03-2014, 05:04   #12
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Re: Practical aspect of sizing solar panels?

Quote:
Originally Posted by socaldmax View Post
I've been doing a lot of scheming, and I think I will eventually buy a Leopard 45 or 47.

According to my calculations, I could install 7 panels (39"W x 60"L) across the back, on top of a sturdy arch over the dinghy. It would be tied into the roof, at least 2 points on the outboard side of each hull, and 1 or 2 locations on the inboard side of each hull. These would be 275-300w 24v panels.

If that isn't enough for the watermaker, 2 freezers, etc, I'd also like to install 3 fold down panels outboard of each hull, mounted to the safety railing and supported by 4 struts from the edge of the deck out to the outer corner of each panel. Assuming these are also 275 - 300w panels, the grand total should be 3575 - 3900 watts. This should allow a fairly comfortable living arrangement with electric cooking, entertainment, watermaking and fridge, 2 freezers, ice maker, etc. The current plan is to run each panel to it's own MPPT solar controller, with maybe 3 or 4 spares on board. This way each panel will get the max. harvest even under partial shading without affecting others, like parallel or serial wired strings. This will all feed 2 large 24v LiFePO4 banks, one in each hull. By running the watermaker, washing machine and other appliances during peak sun if possible, we use solar energy and minimize night time loads.

This is all just wish list stuff for now. Yes, it will be heavy, Yes, it will have some windage. It might be fairly ugly, although I'd try to make it look as good as possible. My dream is to find remote atolls and secluded beaches and hang out for a week or two at a time, with minimal generator hours and maximum comfort.
Sounds a bit like the more power=bigger boat approach.
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Old 15-03-2014, 05:10   #13
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Re: Practical aspect of sizing solar panels?

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I strongly recommend that you avoid putting the panel's on your Rails. If they're out of the way for easy movement they're very susceptible to damage whether docking or having some idiot drag in to you. Also more susceptible to salt spray. To me biminis are the ideal place. Second choice would be davits. Third choice would be on the house. 4th would be an arch. To OP the reason the arch is last is because it adds windage and cost. As far as the other positions for panels go I think the windage is minimal and the weight is not really a consideration on a 40 foot boat.
I have no bimini, no davits, no pilot house, so looks like I'll be making an arch which should be just about the same as a bimini as far as weight and windage goes.

I am curious about your set-up as it looks like you are on a forty footer, about how many watts do you carry?
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Old 15-03-2014, 05:13   #14
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Re: Practical aspect of sizing solar panels?

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I have about 500 watts of panels and 1,000 amp hours of batteries, I have this much so that I don't cycle the batteries down too low and they last longer. If you don't want lots of panels don't have lots of storage and cycle the batteries harder and replace them more often. It's all compromises and balances.
Do you mind sharing your configuration? Pilot house, bimini, rails, whatever? Thanks
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Old 15-03-2014, 05:23   #15
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Quote:
Originally Posted by Delancey View Post

I have no bimini, no davits, no pilot house, so looks like I'll be making an arch which should be just about the same as a bimini as far as weight and windage goes.

I am curious about your set-up as it looks like you are on a forty footer, about how many watts do you carry?
I currently have 350 watts about to add another 320. Why would you add an arch instead of a bimini or davits? And an arch probably has the same windage as a Bimini but does not provide shade in summer and in winter you can add vinyl sides to give you a sunroom
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