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Old 29-11-2009, 12:10   #1
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Ideal Boat for Large PV Array?

Cruisers' forum:

I'm searching for a used monohull coastal cruiser that's small enough to be sailed single-handed, but has a deckplan that would make mounting a large (~0.8+ kW) PV array simple, convenient and as unobtrusive as possible.

Do such boats exist? If so, which brands/builders should I be considering?
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Old 29-11-2009, 13:45   #2
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How big is a 0.8+ kW PV???

How much real estate does that need? If we knew that it would help.
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Old 29-11-2009, 13:55   #3
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Thanks for the reply.

Solar panels come in various sizes and outputs, and I haven't shopped around for the most space-efficient models, but here's a rough idea of the configuration I'd want:

8x 100W panels, each occuping 46"x32" of davit, rail, bimini or deck space.
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Old 29-11-2009, 14:13   #4
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a 200 watt PV is around 60" x 40" He'd need four of those. Total space of the array would be something along the lines of 10' by 6'8". Not quite big enough to land a helicopter on.

The big question is why anyone needs that much power on a sailboat. I make do pretty nicely with 260 watts PV plus 200 watts of wind. That's running both a freezer and a fridge. 800 watts is going to give you something around 65 amps at full crank.

Goodness.
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Old 29-11-2009, 14:45   #5
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The big question is why anyone needs that much power on a sailboat.
Goodness.

The short answer is that I anticipate a large electrical load. On top of the fridge/freezer, instruments, lights and radios, my situation will require that I run 2 laptops, a cellular phone, and a hefty booster for the phone most of the time I'm on the water.

As a personal matter, I'm averse to shore power and I don't like the prospect of having to run a generator daily just to keep up with base electrical needs.

I also like hot showers, and plan on shunting excess power into a hot water tank.


So, is 800W of solar on a cruising boat within the realm of possibility and reason, or should I start preparing myself for cold showers and room temperature food?
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Old 29-11-2009, 15:02   #6
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The short answer is that I anticipate a large electrical load. On top of the fridge/freezer, instruments, lights and radios, my situation will require that I run 2 laptops, a cellular phone, and a hefty booster for the phone most of the time I'm on the water.
First thing to do is add up the load. I don't get 65 amp hours when I add what I expect those things would draw, unless you plan on running mega incandescent lights and a dozen instruments and radios or so. I can't imagine drawing that much power that's about 6 times as much as we use at max.

Finding a place on a monohull sailboat for that many sq. ft. of panels is going to be a challenge, unless you have an unlimited budget. You might also consider adding some wind power since the sun she doesn't always shine.
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Old 29-11-2009, 15:31   #7
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First thing to do is add up the load. I don't get 65 amp hours when I add what I expect those things would draw, unless you plan on running mega incandescent lights and a dozen instruments and radios or so. I can't imagine drawing that much power that's about 6 times as much as we use at max.

Finding a place on a monohull sailboat for that many sq. ft. of panels is going to be a challenge, unless you have an unlimited budget. You might also consider adding some wind power since the sun she doesn't always shine.

65A/h sounds optimistic, given that the panels will not track the sun, some portion of the array will likely be partially shaded most of the time, and (I neglected to previously mention) that the boat will be spending half the year in latitudes as far north as 48 degrees.

Then again, I'm new to this and don't have a good sense of what I should reasonably expect for PV cell power output.

I appreciate the comments and insight. Many thanks.
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Old 29-11-2009, 15:39   #8
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Given the info in message #5 and factoring in a dark day or two and nothern latitudes not such a great demand. A big aft cabin something ought to fit the bill. We're looking at about an 850AH bank which is not so unusual. Luckily he didn't mention air conditioning. 11ftx71/2ft How big is the back of an OI 41? Dave
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Old 29-11-2009, 16:13   #9
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Get a center cockpit...your Bimini will be about the size of real estate you need.
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Old 29-11-2009, 16:22   #10
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800 watt solar array????

sailorcrat,
I'm going to take a chance here, that you're serious about this and not just pulling our legs.....

1) Although, I do NOT use shore power much (since I'm not in marinas much), I probably have a different (somewhat simpler???) on-board,
cruising/voyaging, lifestyle than you are considering.....
I'd be remiss if I didn't make clear, first off, that you can make substantial reductions in your electrical power requirements, without affecting your planned lifestyle.....

Not knowing what your specific plans are, nor where you're planning on sailing/cruising, it is difficult to be precise, but here are some simple things come to mind right away....
a) Use solar energy to directly heat your water, for your hot showers...or cruise areas where the ambient temps are warm enough that you will not want hot showers....
b) Use low-power consumption computers (netbooks, solid-state drives, mini-tower systems, etc...) rather than high-power consumption "dual-core Duo" processor conventional laptops....
c) Spend less than $100 (and a few days of your own labor) and increase the insulation of your frig/freezer boxes.....No matter what boat you buy, there's a 99.999% chance that you'll find a considerable savings in power consumption (perhaps as much as cutting your frig/freezer consumption in HALF...)

2) Remember that having a large solar array that is partially shaded will not be too effective.....
Keeping the panels in the clear is what you should be looking at.....
The actual size of your array may be in fact end up being smaller than you expect, if you can keep the array in the clear....

3) Use of MPPT charge controllers will give you a significant boost, compared to standard controllers.....
And, in low to mid latitudes (20 - 35 degrees), where I have good sun angles...and in areas with lots of sun (not too many clouds)....I typically get 220 to 260 A/H's per day from my 520 watts of panels, driving Blue Sky MPPT controllers, depending on time of year......
However, I do NOT typically need/use that much power on a daily basis, unless I'm on a long voyage with 24/7 use of autopilot, VHF radios, GPS, instruments, frig, freezer, AIS, etc. 12 hr/day Nav Lights... as well as a few hours daily of stereo, SSB, We Fax, lights, watermaker, etc. etc....

When at anchor, I need/use much less power.....and that includes keeping ice cream frozen for weeks in the summertime!!!

Please see my detailed photos and article, of my own installation on my 47' sloop here:
Solar Panels


4) Make some specific calculations on your expected electrical needs....
In Amp / Hours per Day (A/H's per Day).......
And, then double that number.....or multiply it by 2.5......
And, that would be my recommendation for the largest array you'll need.....assumming that you'll be in low-mid latitudes, without too many cloudy days.....
If you're going to be in high-latitudes and/or many cloudy days are expected....multiply that A/H per day number by 3 to 3.5, and use that as the largest array you'd need....


5) As for deciding on what boat to buy based on how much solar you can mount......that's certainly not what I'd do.....and I personally think it's a bit silly......
But, you asked a legit question, so here's a staight answer:

Look at boats that have areas that will NOT be shaded....keeping the panels in the clear....
This is going to be tough on a "smaller" boats.....
But, if you look at more modern designs, they'll have wider stern sections and may allow you to mount a significant array aft of the boom and in the clear.....
This is why center-cockpit boats are not a good choice....although it would seem to be, the bimini's aren't typically as large as those on aft cockpit boats....plus, you have lots of shading from the mainsail (and the boom as well!!!)....

Again, have a look at my set-up, and you may get some ideas....

As for spocific boats.......haven't got a clue....however, I hope my thoughts/advice will be helpful....


6) Perhaps Nick, on s/v Jedi, will post his thoughts....since I believe he's got almost 700 watts of solar on board his 64' Sundeer....


Sunny Skies!

John
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Old 29-11-2009, 17:40   #11
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Endurance takes 4 panels on the doghouse roof and some on the bimini and then some on the rails. She is 35'.

b.
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Old 29-11-2009, 17:50   #12
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I think that the short answer to your question is no, you cannot reasonably fit 800w of solar panels on a small coastal cruiser. You may be able to squeeze half of that onto a 32' boat. We have two 120w panels on our 32' boat, and they take up ALOT of room. Some designs may allow more than we have, but not on the order you are seeking.

BTW, if you want hot showers, using the sun to directly heat the water is MUCH more efficient. If you put a simple automotive radiator in a black painted, glass covered box, and circulated non-toxic anti-freeze through it and back to a standard marine tank with engine heating loop, you will fare much better. Run the pump with a hard-wired separate small solar panel. If the sun is shining, the pump is pumping.

We have both 2kw of solar panels, and two, 1kw hot water panels on our house, so if you have any questions, let me know.

Chris
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Old 29-11-2009, 19:12   #13
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This may be a bit off topic, but anyway....

How effective are PV panels compared to wind generators? I understand that wind generators only work when it is blowing, but solar only works when the sun is out and in the right spot to not get too much shade....

Just looking at why anyone with a sailboat would be looking for solar panels rather than wind generators?
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Old 29-11-2009, 19:44   #14
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pv vrs solar

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Originally Posted by rustypirate View Post
This may be a bit off topic, but anyway....

How effective are PV panels compared to wind generators? I understand that wind generators only work when it is blowing, but solar only works when the sun is out and in the right spot to not get too much shade....

Just looking at why anyone with a sailboat would be looking for solar panels rather than wind generators?
Solar is quiet, but it almost never works at night. Wind works great in a blow, but tends to disappoint in a protected anchorage.

I'm convinced that the best bet for those of us who spend a lot of off-the-grid time is a combination of the two.
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Old 29-11-2009, 19:48   #15
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I second (third) the idea of using solar showers. They work incredible well, AND THEY DON'T HAVE TO BE USED OUT IN THE OPEN. (Although that can be fun, depending on the anchorage.) We have a stand-alone shower on the boat, and it has its own overhead hatch. We put the sun shower bag up on deck near the hatch, and then drop the hose/nozzle through the hatch. We have hot showers daily while on the hook, and it costs us zero amps.
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