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Old 16-01-2023, 12:05   #1
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Solar vs wind vs hydro

The question of whether to only rely on solar, or to add wind or hydro generators into the mix seems to be a common one here. And on Lille Ø we’ve also been discussing this a lot.

We currently cruise the Baltic Sea for the 5-6 month sunny half of the year, and need shore power for the winter months. The boat is a 31ft Amigo 40 double-ender.

We have a 400Ah (12V) LiFePO4 house bank. This is currently charged with:
Our typical summer consumption is around 1.2kWh (~100Ah) with fridge, computers (we work remotely), navigation gear, etc.
In the winter we use about double this due to heating and needing more light.

During the peak summer we were almost independent on electricity. There were some weeks where it was too clouded or too windy to deploy the FLINsails where we needed to go to a marina and charge. This wasn’t too onerous as you need to provision occasionally anyway. But having more generating capability would be useful.
It would allow us to extend the cruising season as well. Now in winter we can only stay out for 2-3 days before we need shore power again.

Since we have full data logs available from last summer’s cruise thanks to Signal K, I ran some data analysis on how much we could potentially generate with wind or hydro. Below is average daily production in Watts on each month of our trip. The horizontal bar is average daily consumption:



This analysis uses the numbers supplied by Superwind and Watt&Sea for their devices. Wind speed and sailing speed used for the analysis are the actual ones from last summer, as is the real power consumption and solar generation.

What’s not taken into account is potential different behaviour if we had one of these generators. Maybe we’d anchor in a windier spot, or go sailing instead of to a marina when the batteries are running low?

Some conclusions can however be drawn:
  • Adding more solar would have the absolutely best bang-for-the-buck here, if we found place for more panels
  • Both wind and hydro could bump us to over the “electricity independence” boundary during summer
  • Wind (and especially hydro!) is really expensive for what it generates
  • We would’ve gotten a lot more output from the FLINs if we had stayed in anchor a bit more. As it is, we sailed on 2/3 of the days

Current consensus on board is that we’ll try to add a bit more solar this year, and budget for a hydrogenerator for when we eventually want to start making longer passages.

Check out the full analysis in
https://gist.github.com/bergie/6de66...ab085d68e4fe44

This is my first time playing a data scientist, so please let me know if you find any problems with the approach I took!
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Old 21-01-2023, 22:56   #2
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Re: Solar vs wind vs hydro

Solar vs. Wind vs. Hydro
https://www.riggingdoctor.com/life-a...-wind-vs-hydro


Wind, water and solar power: how alternative energy has been transformed
https://www.yachtingworld.com/gear-r...ar-power-65797
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Old 22-01-2023, 02:30   #3
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Re: Solar vs wind vs hydro

Quote:
Originally Posted by coopec43 View Post
Solar vs. Wind vs. Hydro
https://www.riggingdoctor.com/life-a...-wind-vs-hydro


Wind, water and solar power: how alternative energy has been transformed
https://www.yachtingworld.com/gear-r...ar-power-65797
useful articles but rather old. the technology involved is evolving rapidly

we have 1.4Kw of solar and this is plenty for our needs, however if we could we'd also have a wind generator. no viable location on this boat but we had one previously and found the constant 24/7 input made a really useful addition to power generation (although always much less than the solar)

btw, i'd question whether a 31' double ender is going to be able to usefully deploy a water generator. won't the drag be too much ?

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Old 22-01-2023, 04:04   #4
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Re: Solar vs wind vs hydro

Quote:
Originally Posted by chrisr View Post
btw, i'd question whether a 31' double ender is going to be able to usefully deploy a water generator. won't the drag be too much ?
That’s a valid question, and one to which I have no answer. It would certainly produce a lot more power on a bigger, faster boat. Jeremy Bagshaw’s GGR boat carries a Watt&Sea. That boat is almost exactly like our boat, just 1ft longer.

Whether that would work for us is one of the questions I tried to answer with the data analysis. Would of course be valuable to validate that with some real-world usage experiences!
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Old 22-01-2023, 07:21   #5
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Re: Solar vs wind vs hydro

The question on "drag" is always raised by some wanna-be engineer when ever talking about water power, and it is totally a non-issue. I'll try to explain why...

At very low speeds the prop spins very slowly, and the alternator makes no power, and since we are extracting no power from the water, the prop freewheels and it generates very little drag. This is a good thing, because at very low boat speeds we don't have a lot of power available from sails, which is why the boat is going slow.

As the wind speed picks up, and generates more power from the sails, the boat moves faster, and the alternator starts making a bit more power, usually beginning about 3 knots or so. by 7.5 knots the alternator is generating "full power". The thing is, by the time most medium sized sailboats are going 7.5 knots the sails are generating a LOT of power. In all likelihood MORE than the diesel engine can.

You don't think twice about the 50Amp alternator slowing down your diesel engine, do you? So why do you think an alternator on a prop will have a significant effect on your boat speed? Yes, of course it has a theoretical effect. But I am telling you from experience with these things, the amount is lost in the noise. Seriously. Almost all cruisers could make up the difference just learning a tiiny bit extra about sail trim.
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Old 22-01-2023, 07:33   #6
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Re: Solar vs wind vs hydro

Quote:
Originally Posted by SailingHarmonie View Post
So why do you think an alternator on a prop will have a significant effect on your boat speed? Yes, of course it has a theoretical effect. But I am telling you from experience with these things, the amount is lost in the noise. Seriously. Almost all cruisers could make up the difference just learning a tiiny bit extra about sail trim.
Thanks! That sounds very similar to what Watt&Sea say about this:
Quote:
The drag is very low compared to the global boat drag. The hydro will not have any measurable impact on your speed
But of course great to hear this from other parties! Some articles I’ve seen say a hydrogenerator eats up to half a knot of boat speed.
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Old 22-01-2023, 07:44   #7
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Re: Solar vs wind vs hydro

Quote:
Originally Posted by bergius View Post
Thanks! That sounds very similar to what Watt&Sea say about this:


But of course great to hear this from other parties! Some articles I’ve seen say a hydrogenerator eats up to half a knot of boat speed.
Some articles just repeat scuttlebutt without data.
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Old 22-01-2023, 09:21   #8
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Re: Solar vs wind vs hydro

Couldn't say if a hydro would be noticeable on a 31, but it doesn't slow us down in the least.

My initial thought would you be able to do enough speed to get the full potential out of a hydro? Here is an older write up about real world use of a tow generator. Worked for them with a 42' boat.
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Old 22-01-2023, 09:35   #9
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Re: Solar vs wind vs hydro

Quote:
Originally Posted by Bill O View Post
My initial thought would you be able to do enough speed to get the full potential out of a hydro?
Full potential, no, not with this heavy full-keel boat. But useful output? At least the numbers I ran from last summer seem to indicate so.

Here’s the breakdown of boat speed in knots while sailing (SOG since our paddle wheel is not instrumented yet)


And here’s output in Watts based on the Watt&Sea output curve


This averages at 190Wh per day, but obviously doesn’t distribute evenly as that includes the days when we were at anchor etc.

Spread over days, it shows that on a good fast sailing day we’d cover about 90% of our consumption on hydro alone. But on many other days we get almost nothing


Since this is all simulation, I’d love to hear how it maps to real-world experiences with similar gear.
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Old 22-01-2023, 10:42   #10
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Re: Solar vs wind vs hydro

-I think there could be some benefit from Hydro.... at least on passages. On a typical 40 mile day trip to another anchorage you are probably motoring the first and last hour or a bit less getting in and out of anchorages etc. That will charge the battery bank without having Hydro in the water at all. Hydro will not do anything at anchor either which is maybe 80% of your cruising or more.
-I have had wind and frankly, it's too 'on and off' to rely on. Maybe as a support for solar in windy areas, or places where the wind reliably comes up every afternoon, but noisy and troublesome also. You really need charging in the am when your fridge has drawn the batteries down overnight.

Seems to me Solar is the best bet, plus having good generation when you motor also, unless you are one of those that must sail every inch of the way.
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Old 22-01-2023, 11:01   #11
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Re: Solar vs wind vs hydro

Our real world experience from the various sources will be different than yours due to location.
At our latitude (and further south), solar works very well and provides ~90% of the power needs. We also tend to be to be at anchor for days at a time, so again the solar is better than wind or hydro for power production. IMO solar is the best bang for the $ for power production.

Wind in our well protected anchorages is relatively light with some upticks for storms, etc. On passages it produces some, but can be down regulated depending on the battery voltage and other power production sources. (would caution using theoretical numbers as sometimes the charge controllers do not play nicely w/each other and diminish output). So real world for us, the wind gen doesn't produce much power relative to solar and would not replace it again if it dies.

Our hydro works well while sailing with good air. In general, the hydro is used when a majority of the solar is shaded by the sails. We purchased the hydro to use with our below deck hydraulic AP assuming it was going to be a power hog. After using our AP we found it to be very efficient (relative to power consumption reported by others) and the hydro is a bit of overkill just to supplement power for the AP. Overall it does add to the power production when we need it, but was fairly expensive compared to solar.

Most of our daily power is used for the separate refrigerator and freezer systems (average daily 12V consumption in mid summer ~66Ah combined) and the solar easily covers our needs (ymmv).

For summer in the Baltic, would think adding more fixed solar panels would would be the most cost effective option to increase power production for your boat. Both wind/hydro gens are expensive and their relative power production to cost is much lower than solar (in the summer). Would also try to get hard panels since they are more durable than the soft panels.
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Old 22-01-2023, 11:03   #12
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Re: Solar vs wind vs hydro

Quote:
Originally Posted by bergius View Post
Thanks! That sounds very similar to what Watt&Sea say about this:


But of course great to hear this from other parties! Some articles I’ve seen say a hydrogenerator eats up to half a knot of boat speed.
It won't have measurable impact on boat speed for a very large boat such as the 60' racing boats these are often seen on.

For a more modest boat, let's say 40':
A. In very low winds and low boat speed it won't be producing any power and you will pull it out of the water.
B. In very hight winds there will be an excess of power available from the sails, at hull speed and even on a plane the 300W being extracted plus the parasitic drag from creating that is nothing compared to the 1,000W change in power needed to increase or decrease the boat speed by 0.1kt.
C. In moderate winds (7-12kt) the boat will be going 4-5kt and the power extracted plus the inefficiencies in making that power will be in the range of 200W. At 4kt power to drive the boat will be about 2,500W. That means that there will be a loss of driving force of about 10%. The boat won't lose 10% of it's speed but the loss will be measurable.
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Old 22-01-2023, 11:13   #13
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Re: Solar vs wind vs hydro

Quote:
Originally Posted by SailingHarmonie View Post
The question on "drag" is always raised by some wanna-be engineer when ever talking about water power, and it is totally a non-issue. I'll try to explain why...

At very low speeds the prop spins very slowly, and the alternator makes no power, and since we are extracting no power from the water, the prop freewheels and it generates very little drag. This is a good thing, because at very low boat speeds we don't have a lot of power available from sails, which is why the boat is going slow.

As the wind speed picks up, and generates more power from the sails, the boat moves faster, and the alternator starts making a bit more power, usually beginning about 3 knots or so. by 7.5 knots the alternator is generating "full power". The thing is, by the time most medium sized sailboats are going 7.5 knots the sails are generating a LOT of power. In all likelihood MORE than the diesel engine can.

You don't think twice about the 50Amp alternator slowing down your diesel engine, do you? So why do you think an alternator on a prop will have a significant effect on your boat speed? Yes, of course it has a theoretical effect. But I am telling you from experience with these things, the amount is lost in the noise. Seriously. Almost all cruisers could make up the difference just learning a tiiny bit extra about sail trim.
And then there are those of us that are engineers.

In the middle speed ranges for a boat the prop drag is significant and and the affect on boat speed is measurable. This is why even cruisers like to get folding or feathering props. Look up the testing done for the effect of fixed vs folding vs feathering props on boat speed.

That doesn't mean that the loss in speed isn't worth the power obtained, but saying the drag is almost nothing and has no affect on speed is misleading.
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Old 22-01-2023, 11:30   #14
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Re: Solar vs wind vs hydro

When estimating wind generator output using the manufacturers numbers there are a few caveats to keep in mind:

1. The wind flow at the height where wind generators are usually mounted is turbulent. This gives significantly reduced output compared to the manufacturers figures that are measured in a steady smooth airflow.

2. Windspeed on yachts is generally measured at the mast height. The windspeed seen by the wind generator will be lower than the instruments indicate.

3. It is tough to find a mounting location for a wind generator that will not produce shading on the solar panels and solar panel output is drastically reduced by even minor shading (although the FLINsails used in this case for some of the power generation are an exception).

This is not to say that wind generators are not worthwhile, but when trying to theoretically predict the expected net output it is easy to be optimistic sometimes drastically so.
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Old 22-01-2023, 11:37   #15
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Re: Solar vs wind vs hydro

Quote:
Originally Posted by bergius View Post
The question of whether to only rely on solar, or to add wind or hydro generators into the mix seems to be a common one here. And on Lille Ø we’ve also been discussing this a lot.

We currently cruise the Baltic Sea for the 5-6 month sunny half of the year, and need shore power for the winter months. The boat is a 31ft Amigo 40 double-ender.

We have a 400Ah (12V) LiFePO4 house bank. This is currently charged with:
  • 210W of fixed solar panels on hatch garage and aft arch
  • 300W of “FLINsail” solar panels that can be deployed on the mast
  • 80A alternator that charges the LiFePO4 bank via a 30A DC-DC charger

Our typical summer consumption is around 1.2kWh (~100Ah) with fridge, computers (we work remotely), navigation gear, etc.
In the winter we use about double this due to heating and needing more light.

During the peak summer we were almost independent on electricity. There were some weeks where it was too clouded or too windy to deploy the FLINsails where we needed to go to a marina and charge. This wasn’t too onerous as you need to provision occasionally anyway. But having more generating capability would be useful.
It would allow us to extend the cruising season as well. Now in winter we can only stay out for 2-3 days before we need shore power again.

Since we have full data logs available from last summer’s cruise thanks to Signal K, I ran some data analysis on how much we could potentially generate with wind or hydro. Below is average daily production in Watts on each month of our trip. The horizontal bar is average daily consumption:



This analysis uses the numbers supplied by Superwind and Watt&Sea for their devices. Wind speed and sailing speed used for the analysis are the actual ones from last summer, as is the real power consumption and solar generation.

What’s not taken into account is potential different behaviour if we had one of these generators. Maybe we’d anchor in a windier spot, or go sailing instead of to a marina when the batteries are running low?

Some conclusions can however be drawn:
  • Adding more solar would have the absolutely best bang-for-the-buck here, if we found place for more panels
  • Both wind and hydro could bump us to over the “electricity independence” boundary during summer
  • Wind (and especially hydro!) is really expensive for what it generates
  • We would’ve gotten a lot more output from the FLINs if we had stayed in anchor a bit more. As it is, we sailed on 2/3 of the days

Current consensus on board is that we’ll try to add a bit more solar this year, and budget for a hydrogenerator for when we eventually want to start making longer passages.

Check out the full analysis in
https://gist.github.com/bergie/6de66...ab085d68e4fe44

This is my first time playing a data scientist, so please let me know if you find any problems with the approach I took!
I assume the average daily consumption you indicate in Watts is actually Whr or should we multiply by 24hr to get Whr?
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