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Old 22-09-2017, 16:49   #1
PHR
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Are solar and wind enough for cruising?

Dear dudes and dudettes,

Wife and I are buying a 49’ Hunter that does not have many bluewater perks (but it does have a great price, and a small generator). I am looking to add some things, and would like your thoughts and experience on solar and wind power.

Assuming we are offshore, and not going to be in a marina for awhile…..Can we run air conditioning or heating off of the batteries? Do I have to run the generator, or can A/C be run off of the batteries? What about the water heater? Microwaves and small plugins, I assume are no big deal, but if we have the bigger power draws, then what kind of batteries do we need, and what charging system should we employ?

We have a $50k budget to modify the boat. What should we focus on first? What would you do if you could make your own dream electric system?
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Old 22-09-2017, 17:27   #2
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Re: Are solar and wind enough for cruising?

It's better if you figure this out for yourself. We can help. If I give you the answer it won't be what you want to hear and usually this starts arguments.

Step 1: Figure out your power budget. How much power does each item draw, and how many minutes or hours per day will it be on? Add this all up (put it in a spreadsheet, since I guarantee that you will be making adjustments during the process).

Here are some examples (all based on a 12V system):
* Small boat refrigerator like mine -- 5 amps when running, it runs about 40% of the time in the tropics and 20% of the time in temperate climates. Say it runs 30% of the time, that's 0.3 * 24 * 5 = 40Ah / day.

* Microwave oven -- 90A. If you run this 15 minutes per day that equals 22.5 Ah / day.

* Laptop computer -- 5A (some are less, many are more). Using this four hours a day burns 20 Ah / day.

* LED cabin lights -- 0.1A each. Five lights, six hours / day equals 3 Ah / day.

* LED Anchor light -- 0.2A. Twelve hours / day operation = 2.4 Ah / day.

Adding just these loads gives you 87.9 Ah / day.

Step 2: Figure out how much power you can get from the solar panels that will fit on your boat.

A 100W solar panel will deliver roughly about 40 Ah / day of energy (charging a 12V battery). This is with zero shading, no cloudy days. You will need at least 250W of solar just to support my basic example loads.

Adding air-conditioning will be virtually impossible without shorepower or a good generator and adequate fuel. An electric water heater is probably worse. Electric heating is equally difficult -- a diesel heater (Espar, etc) is a more reasonable approach.

But don't take my word for it. Collect the power consumption specs for the gear you want them to run and do the math. Unfortunately, there's no free lunch. Large batteries may let you ride through the occasional cloudy day, but sooner or later you need to put in more total energy than you take out.
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Old 22-09-2017, 17:31   #3
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Re: Are solar and wind enough for cruising?

Yes they are enough for very small loads.

Even a small fridge gets into "how many panels? "

Learn the basics on calculating watts, volts, amps, and come up with an AH per day budget.

Figure out how many square meters you're willing to cover in panels.

Air conditioning or heating forget it, you'll run the genny.

With the right sort of batteries, if you're running the genny an hour or two each day anyway, ideally in the morning, then just a few panels will help get the bank to full.

Adding lots of panels will then just cut down on genny runtime.
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Old 22-09-2017, 17:35   #4
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Re: Are solar and wind enough for cruising?

I assume you have many other things to do with that $50k besides electric?

Be very conservative, pretend you only have $10k to start with, that is one area it's easy to overspend unnecessarily. IOW forget about a "what is your dream system" approach.

Focus on that energy budget first, then we'll need a lot more questions answered before giving specific reco's.
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Old 22-09-2017, 17:36   #5
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Re: Are solar and wind enough for cruising?

If you head south to around 10 deg, you need more.
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Old 22-09-2017, 17:46   #6
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Re: Are solar and wind enough for cruising?

Quote:
Originally Posted by Paul Elliott View Post
It's better if you figure this out for yourself. We can help. If I give you the answer it won't be what you want to hear and usually this starts arguments.

Step 1: Figure out your power budget. How much power does each item draw, and how many minutes or hours per day will it be on? Add this all up (put it in a spreadsheet, since I guarantee that you will be making adjustments during the process). <snip>
Excellent advice, Paul.

PHR, if you want some help with this, we caused my son to do an energy budget when we first moved on board Ocelot. His methods and results are posted here.

A very interesting number came out of this exercise. Everyone wants to know how much power, in amp-hours/day, a solar panel will deliver, and no sales folks or specs will give you that. Our son found that if you take the nominal wattage of a panel and divide that by 3, that's pretty close to the number of Ah you'll get into your batteries on a sunny day in the tropics, for flat, unshaded panels. This is a bit less than Paul mentioned, but it was experimentally determined, so possibly more accurate.
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Old 22-09-2017, 19:38   #7
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Re: Are solar and wind enough for cruising?

Awesome sauce! Thank you folks. More to learn. I appreciate the energy budget ideas. I got some work to do.
Yes, more to do with the $50k. The Hunter does not have a dinghy, or davits, or a watermaker (but it comes with a 200 gal tank), and I am still working on the spending plan.
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Old 22-09-2017, 19:59   #8
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Re: Are solar and wind enough for cruising?

One more thing, your at-anchor power consumption is usually substantially less than your sailing consumption. This of course depends on how you use your chartplotter / computer / autopilot (these are typically the bigger loads). On my boat, by solar panels are just about good enough to supply all my at-anchor needs. When sailing I usually need to run the engine for battery charging one hour or more / day.
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Old 22-09-2017, 20:11   #9
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Re: Are solar and wind enough for cruising?

A power budget is a great tool but limited to the accuracy of the inputs. A more practical approach is to look at the big items:

1. Heat, air conditioning, and hot water you cannot do off the batteries. Heat is easy to do with a diesel heater, $1,000 installed. AC needs a generator but you mostly need it in a Marina, not at anchor. Hot water is best heated from the engine. Some people think that it is too much trouble to run the engine for hot water. In reality, most cruisers run the engine more often than they think. It charges up the batteries, heats the water and allows you to move the boat in the absence of wind.

The big DC loads are autopilot, fridge and laptops/TV. Figure about 100 AHrs between the three of them. Everything else is small potatoes, add another 50 AHrs.

If you run the engine or Genny for 1 he a day, you will be covered. My suggestion is, go that route for about a season, fhen decide if you need solar or anything else. Save the money, though do not now it on a dinghy or something.
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Old 22-09-2017, 20:54   #10
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Re: Are solar and wind enough for cruising?

You don't know what your budget will be until your out there, and even then it's sort of variable.
In short to some extent if you have it, you will likely use it and you can't spend what you don't have, so you will do without luxuries cause you have to if you come up short.
Maine Sail has measured on average I believe Solar power return of .224, meaning if you have 1,000 watts of panels that you will on average get 224 AH daily. That's an average if I understand correctly and of course you have cloudy and rainy days too, that kills average output. But it's a good realistic planning number.
Make sure you have a GOOD shorepower charger, cause I suspect you will use it with the generator more than you may think, remember to subtract house loads for charging too, don't think a 30 amp charger will charge at 30 amps, cause the house loads come off of that 30 first.

I don't think you can have too much Solar, just an opinion of mine.
There are ways to save mucho $$$ doing a Solar install, and I have seen huge amounts of money spent buying arches and having it all done as opposed to DIY.
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Old 22-09-2017, 21:19   #11
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Re: Are solar and wind enough for cruising?

In the above posts, I don't see any allowances made for inefficiencies in charging/discharging the battery's Peukert exponent.

If lead acid, you need to put back 120 amp hours for every 100 amp hours you take out.
Even that is not a given number depending on how much current your are drawing to compute those amp hours (either charged or discharged).

Math is hard, but it's still reality.
That's why several are going to LiFePo4 (I did several years ago), but that's a different thread.
Hint, Peukert with LiFePo4 is 1.01, not 1.15 to 1.20
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Old 22-09-2017, 21:27   #12
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Re: Are solar and wind enough for cruising?

Hi Matt, you are buying a good boat. Hunters have a bad rap but when i carefully had a good look at the 49 I was impressed with the construction eg. Lead keel. They are very well built.
If you want advice from someone that has alot international cruising experience on a hunter 49 Google Screensaver hunter 49. Alan is a good bloke and has quite a few nm's under his belt.
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Old 22-09-2017, 21:47   #13
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Re: Are solar and wind enough for cruising?

Quote:
Originally Posted by senormechanico View Post
In the above posts, I don't see any allowances made for inefficiencies in charging/discharging the battery's Peukert exponent.
I did say:
Quote:
Large batteries may let you ride through the occasional cloudy day, but sooner or later you need to put in more total energy than you take out.
There are many sources of power system loss and yes, battery charging and discharging are significant factors. However, I find that the variability inherent in solar panel output is an even bigger factor.

Nobody is going to claim that compiling an energy budget is a precision exercise. At best it will be a rough approximation. But it will still provide very useful guidance as you figure out your system.
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Old 22-09-2017, 21:48   #14
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Re: Are solar and wind enough for cruising?

Google SEQUITUR an H49 that rounded Cape Horn. Great read, up your alley in terms of systems.
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Old 23-09-2017, 00:54   #15
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Re: Are solar and wind enough for cruising?

couple of comments, you will likely need the AC much less on anchor than you think. There is usually a breeze and it is always from the pointy end :-) unlike in a marina. We spent a summer in the sea of Cortez. Had an air conditioner, but only used it in the marina in Santa Rosalia. Yes it was hot, but breezy on anchor and not worth running the generator to use the AC. We are currently in Fiji (still very tropical) and there is no need for AC at all, so it also depends where you plan to go.

Second, consider running the hot water off of the waste heat of the generator instead of the engine. We do that and almost never run out of hot water. We run the generator about an hour a day to charge the batteries and make water. (our watermaker is belt driven off the generator.)

My 0.02, Eric
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