Wind is better than solar. Discuss

[Na Mara]

So I’m still trying to work out what the best power system for Na Mara is. I thought I had it when I decided on a 4kW generator coupled with a big Lithium bank and a fat inverter/charger but then my Dad went and fitted a new silentwind pro onto his boat and now he’s raving about it so I’m having to reconsider. Being a big nerd I decided to crunch some numbers and I thought I’d share this with the community.

To figure out whether a silentwind pro would work for me I closely approximated the output curve with an exponential function. I then found the area and season that I am likely to cruise in that has the lightest winds. That happens to be the Baltic Sea during the summer. The daily average winds there at that time have a mean of 5m/s (10kn) with a single standard deviation of 1m/s (2kn). Assuming that the wind speeds are normally distributed, I then calculated the average output of a silentwind pro by calculating the average value of the output curve for winds between 0 and 15m/s (Integrating the product of the output curve and pdf for the wind distribution between 0 and 15). The result was 36W, which translates to an average daily energy input of 860Wh or 72Ah at 12V. That is just enough to cope with our needs at anchor but no where near enough to cope with them underway. However, two silentwind pros would cover all our needs with a bit of spare capacity even on this worst case scenario.

In this worst case scenario - from a wind power perspective - of being in the Baltic during summer the capacity factor of my wind generators would be less than 9% and the capital cost per daily Wh would be in the region of 3.5€ (silent wind pro plus mast, controller and installation 3000€)

Now compare that with solar. Average monthly solar radiation in the southern Baltic in summer is around 130kWh/m2. Assuming 30 days in a month gives you a daily average of around 4.5kWh/m2. Assuming 20% efficient panels gives you average daily energy input from each meter squared of panels aboard of 900Wh. So as near as makes no difference 1m2 of solar will give me the same energy input as a silentwind pro in this worst case for wind. Again, to meet our needs we would need to double this so we would need about 2m2 of solar. To mount 2m2 of solar - about 350W - on Na Mara I would either need davits or an arch. Either of those plus panels and sundries comes to at least 5000€ installed and so the capital cost per daily Wh is at best 2.8€.

The Baltic in summer is a best case for solar and a worst case for wind. High pressure systems from Siberia tend to move in over the Baltic during the summer and settle there. These together with the high latitude lead to long cloudless days in summer with very little wind. Sailing pretty much anywhere else around these parts, such as Skagerrak or Kattegat or off into the North Atlantic, there will be more cloud and more wind. As output from wind goes up by the cube of wind speed, the above calculation rapidly shifts in the wind turbine’s favour if we sail anywhere else than the Baltic in high summer.

Of course an arch that carries 3m2 of panels isn’t much more expensive than one that carries two, so if Na Mara were a more hungry power consumer, then the calculation above would be more in solar’s favour with a capital cost per daily Wh of a bit less that 2€. However, that extra power would be wasted on Na Mara and the bigger arch would just increase windage, ugliness and capital cost to no practical end.

All in all it would seem that a pair of wind generators charging a very large bank - to smooth out the feast and famine nature of wind energy - would do the trick and for Na Mara better than solar. Basically, unless my calculations are way off, I have to disagree with all the “solar is all you need” crowd on this forum. Modern wind is virtually silent, easy to regulate through Bluetoothed apps, perfectly capable of more than meeting all the energy needs of a moderate cruiser even in relatively low wind zones, and price comparable on a capital cost per energy produced basis (at least this is so for those of us not sailing boats already sporting suitable structures for mounting panels).

One concern with this reasoning is that I, like manus herr, am also wanting to do an Atlantic circuit and everyone keeps saying that the reduction in apparent wind on wind generators makes them borderline useless on such trips. But the trades run at an average of 10m/s with a single standard deviation of 2m/s when yachts do the crossing so even running dead downwind at 6kn (3m/s) the average apparent wind will be 7m/s with 2m/s SSD. That gives an expected average output for the wind genny of about 66W for the crossing producing an average of 1.5kWh a day. That is almost enough to meet my needs on the crossing on its own. Add another wind generator - which I would need in the Baltic anyway to meet my needs summer cruising - and I would luxuriate in over 3kWh a day from the pair. So this concern about wind and power on downwind legs is, according to my calculations, also without foundation.

[C420sailor]

Don’t forget the other little things.

There are a couple boats near me with wind generators. Sweet Christ are they annoying, and I’m a few hundred feet away. I can’t imagine being feet away with all that noise, day and night.

[flyingnut40]

Follow, I need the wisdom you seek. Dennis

[Beneteau2011]

Originally Posted by C420sailor

Don’t forget the other little things.

There are a couple boats near me with wind generators. Sweet Christ are they annoying, and I’m a few hundred feet away. I can’t imagine being feet away with all that noise, day and night.

IT’S A GOOD THING WINCH HANDLES ARE EXPENSIVE. REDUCES THE POSSIBILITY OF THROWING THEM…………………………………………………………….

[Stu Jackson]

It sounds like you're reinventing the wheel. Solar doesn't necessarily demand an arch or davits. I have a friend with a 33 foot Hunter e33 who has 335W of panels on his dodger and bimini alone. There have been successful installations that don't have to look like a spaceship. Most of the conclusions I've read here end up finding based on both analysis and actual real world experience is that solar wins hands down all the time. In any event, good luck and safe journeys.

[Na Mara]

Originally Posted by C420sailor

Don’t forget the other little things.

There are a couple boats near me with wind generators. Sweet Christ are they annoying, and I’m a few hundred feet away. I can’t imagine being feet away with all that noise, day and night.

Agreed that old wind generators are often a noise hazard, but modern ones are a totally different thing altogether. You can hardly hear them even sleeping right under them, and if they annoy, you can shut them down from the comfort of your bed using an app.

[Na Mara]

Originally Posted by Stu Jackson

It sounds like you're reinventing the wheel. Solar doesn't necessarily demand an arch or davits. I have a friend with a 33 foot Hunter e33 who has 335W of panels on his dodger and bimini alone. There have been successful installations that don't have to look like a spaceship. Most of the conclusions I've read here end up finding based on both analysis and actual real world experience is that solar wins hands down all the time. In any event, good luck and safe journeys.

Some of us neither have, want or need permanent dodgers or biminis. My pilothouse windshield and roof is all the dodger and Bimini I need. My easy mounting options are guardrails or semi flex panels on the shaded pilothouse roof. Apart from that, it’s an arch or davits with all the associated costs

[stormalong]

Na Mara: You do not give any information about your boat. That makes it more difficult to comment but here goes.

Do you have a bimini over your cockpit? Does your boom extend over your cockpit? A bimini is an ideal place to put solar if it is not shaded. A little reinforcing of a standard bimini frame can hold your solar. That is what I did. I had four custom brackets and two rails made to mount to my bimini and two additional posts to make the bimini stiffer. It holds 390 watts of solar. Your 5000 euro price sounds like it includes the price of the arch. Some small reinforcing and small custom stainless work is far less expensive than an arch and much lighter too.

On solar vs wind. Wind will disappoint you. You need 15 knots to make minimal power. Solar is silent and on long summer days produces a lot of power. I have both. The upside with wind is if you are in a very windy place or on windy rainy days when solar doesn't produce.

Anyone want to buy an AirX with Air+ blades and a nine foot pole?


Edit: I see from your post above that you don't want or have a bimini. How big is your pilot house roof? As someone else posted while I was typing me response: An arch or davits are not needed for solar. Look around and think about rail mounts. I would rather buy additional panels (cheap these days) than add an expensive, heavy arch.

[Dsanduril]

I've had boats with wind and boats with solar and boats with both. Our current boat only has solar. When solar isn't working well is frequently when there's plenty of wind, so that comes down on the plus column. Made a trip to Hawaii one year where the first week the wind generator was 80%+ electrical supply and the next week was 80%+ solar. They can work/balance well.

But even those of us who sail a lot spend much of our time at anchor, and at least for us we're usually trying to find places to anchor that don't have a lot of wind. Under those conditions when the sun goes away the wind doesn't do anything either.

And I'd challenge the notion that any wind system is "silent". Quieter than they used to be? Yes. Silent, well, that's all in the ear of the listener. And don't forget vibration on top of sound.

In the end, for this boat we have opted for solar only. That accounts for more than 95% of out electrical usage. We have averaged about once a month when we had to spin an alternator for the purpose of charging, adding wind would cost a lot more than that incremental cost in engine time. And those values have held up pretty consistently from the tropics to the higher latitudes. If I lived aboard during the winter months away from a dock that might be entirely different.

[Na Mara]

Originally Posted by stormalong

On solar vs wind. Wind will disappoint you. You need 15 knots to make minimal power.


Edit: I see from your post above that you don't want or have a bimini. How big is your pilot house roof? As someone else posted while I was typing me response: An arch or davits are not needed for solar. Look around and think about rail mounts. I would rather buy additional panels (cheap these days) than add an expensive, heavy arch.

I worked out that I can fit 4 semi flex panels totaling about 300W on the pilothouse. Those plus controllers, wiring and install came to around 1500€. A fellow with exactly the same boat as me had exactly this set up of panels . When I talked to him about it it was 10:30 on a blistering hot day and he showed me that he was getting about 90W out of the panels due to the shading from the boom. Maybe having a controller for each panel would help but still, it was disappointing.

Also the silentwind pro, as well as some other modern turbines, produces 20W at 6kn of wind. Judging modern turbines on the basis of experience with older ones is like judging a modern Mini Cooper on the basis of experience with its forefather.

[thinwater]

Primarily following. Na Mara made a reasoned evaluation.


Why not both? Install as much solar as convenient (low cost, not in the way, perhaps 150-200W) and one wind generator? IME, many areas have either sun or wind, but not always both at the same time. With stormy weather you will have no solar and all the power you can use with just one turbine. With sunshine they probably combine to be enough, certainly underway (more wind).


Just a thought. I know that in the summer Solar works well for me, but in the winter, with low sun angle, longer nights, and more demand, solar is challenged by a few gray days.

[boatman61]

Originally Posted by C420sailor

Don’t forget the other little things.

There are a couple boats near me with wind generators. Sweet Christ are they annoying, and I’m a few hundred feet away. I can’t imagine being feet away with all that noise, day and night.

They obviously have crap wind genies.. back in the 90's my Aerogen kept me constantly powered from the UK down to and around the Med for four years.. quiet as a mouse.
Also had an Aerogen/solar setup on my Bene 331 on a custom arch that also served as davits for my inflatable.
Sadly Aerogen is no more, however the Rutlands have good press..

[stormalong]

Originally Posted by Na Mara

I worked out that I can fit 4 semi flex panels totaling about 300W on the pilothouse. Those plus controllers, wiring and install came to around 1500€. A fellow with exactly the same boat as me had exactly this set up of panels . When I talked to him about it it was 10:30 on a blistering hot day and he showed me that he was getting about 90W out of the panels due to the shading from the boom. Maybe having a controller for each panel would help but still, it was disappointing.

Also the silentwind pro, as well as some other modern turbines, produces 20W at 6kn of wind. Judging modern turbines on the basis of experience with older ones is like judging a modern Mini Cooper on the basis of experience with its forefather.

Stay away from any kind of flex panels. Short life and lower output. 20 watts is insignificant unless you are just powering LED lights. 1500 euros should buy you at least 750 watts of rigid solar and a good MPPT controller.

[Na Mara]

But where do I mount 750w of rigid panels? It could only be on a massive arch and then 750W of solar is costing the same as 840W of wind. Ok the solar will deliver nearly twice the energy on average, but I don’t have any use for all that extra energy.

[Anders]

"Silent wind" are very noisy and I would never have one on our boat.