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Old 23-09-2016, 16:45   #1
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Mixing solar and prop generated power

Trying to design a off grid system for 10 year old sailboat (clean slate). 24 hour consumption 320 amp/hours. Put together a idea of 2- 340w 24v solar panels with mppt controllers. Propeller shaft driven alternator (DC 540 low wind permanent magnet). Talked to a tech at emarine. He said I need to add a third controller for the alternator driven by the prop. Also have to deal with the alternator creating energy on the engine when it is running. Is there a way to tie all three together under one roof? Looked at the sterling prosplit r. So many options....not unlimited budget.. but designing it for multiple years of sailing so would like to do it right. Any and all input greatly appreciated . Forgot to mention 630 a/h house bank
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Old 23-09-2016, 17:10   #2
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Re: Mixing solar and prop generated power

That's a high daily consumption. We focussed on getting rid of AC loads in lieu of 12V DC. Much more efficient due to removing all the ac to dc and dc to dc conversion inefficiency. We went from 200+ to about 110 Ahr per day. We aren't camping or glamping. We only use the inverter for loads like the iron, blender or some power tools.

Your house bank, assuming fla is undersized for your current daily load. We have a 675 Ahr house bank. You can use about a third of that on a daily basis and get a reasonable life from your batteries.

Prop shaft driven charging is more efficient than a comparable wind turbine but the useful duty cycle will be very low. Unless you spend all your time running downwind in the trades. I see almost no valid use case for prop generation for a cruising sailboat.

We're now looking to fit 1000W of solar and have retired our old wind turbine. We will use the excess solar to heat hot water. Solar accounts for more than 98% of our off grid energy production.

Our sizing approach is as follows:

1) reduce consumption inefficiencies. 12V DC and no persistent inverter loads
2) house bank should easily deliver two days consumption
3) size solar to recharge 2 days consumption by noon. Remainder of energy production then goes to heating hot water. This allows for clouds, shading and other real world factors that the standard house roof solar calculators ignore.

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Old 23-09-2016, 17:17   #3
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Re: Mixing solar and prop generated power

I don't think the DC 540 will work well for you. Permanent Magnet Alternators can only be regulated with a dump regulator and a power dissipation system. You will need to disconnect it from the prop shaft when you are motoring.
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Old 23-09-2016, 17:59   #4
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Re: Mixing solar and prop generated power

Left brain
Thank you much for getting back me. That usage was under sail 24 hours a day. Say 6 days from Galveston to key west. Once we get to the Bahamas that usage will drop considerably. Maybe I don't have the amp hours correct. I had autopilot at 120 a/h a 24 hr and fridge and freezer @ 108 per 24hr. Those being the main culprits. We are planning on only 12v DC....no inverters or converters except the mppt solar chrgers. The autopilot will not be used as stated but just wanted to build in a fudge factor. What you said about the prop generator completely makes since when we're island hopping or only sailing 6 or 7 hrs a day
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Old 23-09-2016, 18:05   #5
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Re: Mixing solar and prop generated power

Don Radcliffe thank you for getting back. That was my concern. When I talked to the tech at emarine he mentioned maybe putting a circuut breaker between it and the controller . Also putting a switch between the alternator and the house bank
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Old 23-09-2016, 20:35   #6
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Re: Mixing solar and prop generated power

The problem with a switch or circuit breaker is that if you disconnect the alternator from the load, the internal voltage will rise high enough to damage things. You will really need to stop the alternator from turning.
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Old 23-09-2016, 22:01   #7
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Re: Mixing solar and prop generated power

Quote:
Originally Posted by leftbrainstuff View Post

We're now looking to fit 1000W of solar and have retired our old wind turbine. We will use the excess solar to heat hot water. Solar accounts for more than 98% of our off grid energy production.

Our sizing approach is as follows:



Sent from my SM-N900T using Cruisers Sailing Forum mobile app
If you are looking to sell the wind turbine what one is it and are you wanting to unload it. I have a customer that is in the market for a good unit to augment his solar.
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Old 23-09-2016, 23:23   #8
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Re: Mixing solar and prop generated power

Quote:
Originally Posted by Hapigo View Post
Trying to design a off grid system for 10 year old sailboat (clean slate). 24 hour consumption 320 amp/hours. Put together a idea of 2- 340w 24v solar panels with mppt controllers. Propeller shaft driven alternator (DC 540 low wind permanent magnet). Talked to a tech at emarine. He said I need to add a third controller for the alternator driven by the prop. Also have to deal with the alternator creating energy on the engine when it is running. Is there a way to tie all three together under one roof? Looked at the sterling prosplit r. So many options....not unlimited budget.. but designing it for multiple years of sailing so would like to do it right. Any and all input greatly appreciated . Forgot to mention 630 a/h house bank
30 years ago we had a prop shaft alternator and a wind genny and a small 8hp single cylinder BMW diesel with a small alt aboard our small 24 foot sailboat. No solar at that time yet and we had no inkling about how to manage the charging other than voltage monitoring and manually on/offing. .. What I recall about the system was that from time to time we forgot to keep a close enough an eye and we would drastically overcharge, resulting in bats gassing and heavy hydrogen smell.. yikes..

Frequently it charged much faster than the wind genny. Sorry I cant remember details. But the boat was also very simple, only portable fridge and autopilot and few lights..

Today my view is that it would be much better to omit the prop shaft alternator altogether. It just adds unwanted complexity, wear and tear and cost. I would much rather prefer solar with good quality controllers, a higher output engine alternator, and a Honda 2000... No wind genny because not only they tend to be noisy, but rather because on a monohull sloop just about the only place where to install it is the transom corner on the pushpit, and it WILL shade your panels there, thus spoiling your panel output.
Simple and reliable and not overly expensive. KISS is the way.

Here is something detailed you might want to read:

LIFE: Part 2: Prop-Shaft Driven Alternator
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Old 24-09-2016, 10:18   #9
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Re: Mixing solar and prop generated power

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"Today my view is that it would be much better to omit the prop shaft alternator altogether. It just adds unwanted complexity, wear and tear and cost. I would much rather prefer solar with good quality controllers, a higher output engine alternator, and a Honda 2000... No wind genny because not only they tend to be noisy, but rather because on a monohull sloop just about the only place where to install it is the transom corner on the pushpit, and it WILL shade your panels there, thus spoiling your panel output.
Simple and reliable and not overly expensive. KISS is the way."
I TOTALLY CONCUR. DITCH THE SHAFT. Your design has too many critical one points of failure with it. Do you want to sail or be a slave to your power system.

GET MORE EFFICIENT, lower your consumption and go solar.
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Old 30-09-2016, 18:29   #10
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Re: Mixing solar and prop generated power

Quote:
Originally Posted by Hapigo View Post
Trying to design a off grid system for 10 year old sailboat (clean slate). 24 hour consumption 320 amp/hours. Put together a idea of 2- 340w 24v solar panels with mppt controllers. Propeller shaft driven alternator (DC 540 low wind permanent magnet). Talked to a tech at emarine. He said I need to add a third controller for the alternator driven by the prop. Also have to deal with the alternator creating energy on the engine when it is running. Is there a way to tie all three together under one roof? Looked at the sterling prosplit r. So many options....not unlimited budget.. but designing it for multiple years of sailing so would like to do it right. Any and all input greatly appreciated . Forgot to mention 630 a/h house bank
Not too much response here.
You have to put out more info here.
10 yo boat is not sufficient info for the boat.
Engine ? Alternator 12volt? Or 24volt,
Off grid , means your not plugging in. I doubt 640 watts solar is sufficient. How will you generate prop power w/o wind?
If you have a clutch, and you can mount a pulley or gear that drives with engine not engaged to your drive system , you may drive a gen not mounted on your engine.
You must do a lot of brainstorming WAY out of the common boat box.
BUT, be not dismayed, because it can and is being done.
Search Arcimedies , for I think spelling may be incorrect?
Concrete boat, no sails, solar panels adjustable, golf cart motor coupled to diesel drive with chain drive ....
The bigger the boat the more real estate for solar panels. Research your percentages of loss and efficiency.
Done let naysayers daunt you , it's realistic to peruse your dream.
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Old 01-10-2016, 13:05   #11
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Re: Mixing solar and prop generated power

Thanks for all the suggestons and advice. We are staying with the 2- 340watt solar panels with the 2 controllers networked together w/the ipn pro remote display. Looking at a high output marine alternator to add to the engine. I just have not been able to find the right design for the prop shaft driven alt..the ability to controll output being the problem.
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Old 01-10-2016, 17:14   #12
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Re: Mixing solar and prop generated power

Assuming typical 5hrs at rated output, that should generate around 260amp-hr @ 12V (you didn't tell us the system voltage).

If your more typical anchored usage will 200amp-hr, the solar panels will be plenty for 95% of days. On passage, consider running the motor for an hour or two each day to make up the extra that the autopilot uses. Since it's a rare situation, it will be much cheaper and less complex. You are probably only talking about a gallon or two per week on passage for charging, so it shouldn't induce any significant range anxiety.

Don't make the system more complex than it needs to be.
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