Wind is better than solar. Discuss

[Jim Cate]

Na Mara, I salute your efforts to quantify the output integrals from a wind gen, but must caution you about a few realities.

First, the wind speed data (at least in all the Met offices that I've dealt with) are ten minute averages, taken at a height of 10 meters above the surface. Very few yachts can mount their wind turbines anywhere near that height, and the velocity drops off pretty rapidly as you descend from the 10 m level. And averages of velocity when applied to a device where the output varies as the cube of the velocity can give really weird results.

Second, the output curves (if even honestly reported) assume laminar and stable flow, conditions that are never found around the stern of a yacht, either at rest or sailing. Turbulence is generated by the airs interaction with sails, masts, appendages, dodgers, pilot houses, lifelines, and even the surface of the sea (waves, etc). And the turbulence seriously degrades the efficiency of the turbine. I've spent hours watching our turbine as it speeds up, slows down, yaws violently, sometimes spins in circles as the boat rolls, pitches and yaws and the wind varies in strength and direction. Watching the output ammeter shows the output continuously varying over significant ranges... rather different than the pretty steady current developed by our panels!

I fear that your projected outputs are quite a bit higher than the reality you would experience. Not to say that wind turbines are not useful, for even our old school Air-X has provided good output at times. But counting upon one for generating a useful proportion of your needs, especially in a low wind area, is a doubtful scheme IMO.

As others have said, a combination of solar and wind is likely to provide more watt-hours per dollar in the long run, again IMO.

Jim

[dfelsent]

Our wind gen is 5 meters or so up. We have about 450 watts of solar. The gen is an older (1990s) air breeze with a new hub and the silent blades.
I write this as the gen is spinning. And it’s quiet enough. But the solar is the game changer in the summer. Wind spring and fall is far more output than in the summer.
Like most mono hulls solar area is limited. And often shaded by the rig.
Multiple sources, including the dreaded alternator from time to time is what works for us.

[boatman61]

Originally Posted by donradcliffe

I've had both solar and wind for 15 years of cruising, and the next boat will be all solar.

Calculate all you want, but you seem to have made your mind up and use assumptions which justify your choices. Both solar and wind salesmen exaggerate, but you will be more disappointed in the output of the wind generator. In addition, wind generator maintenance is much higher than for solar panels.

What.. a change of brushes every few years..

[sailingabe41ds]

How about it depends where you live. I love silent solar panels do not like noisy fuggly noisy wind generators. You don't even see my panels...420 watts.

Abe

[Na Mara]

Thanks Jim for engaging with the math.

I am not sure how the measurements I used were done but assuming that you are correct that the mean and SSD were calculated from averaging spot values taken every 10 mins, I don’t see how that invalidates the math. We are talking then about 144 data points per day. That equates to a sampling error of less than 10%. So there will be 95% confidence that the mean is within 0.5m/s of the stated value. In my math I assumed a much larger variation in wind speed that this error when I used the SSD data. On My assumption the wind in the Baltic is within 2m/s of 5m/s 95% of the time.

Your other two points are more valid. Most people report that the output curves for wind generators are reliably but of course they mostly pay attention to the wind gen when it’s pumping out amps in higher wind speeds. The effects you talk about effect the low wind speed performance more as in this region the motions of the boat can overwhelm the dynamic wind pressure on the vane on the wind gen and so the generator will tend to yaw side to side out of the available wind. I can’t quantify that effect but I admit that it could be substaitial on the low wind speed performance which could indeed invalidate the math above.

Then there is the point about sampling height in the data, and the turbulence of airflow across a yacht. The data was averaged from collection from three heights: the least of these was 3m. Generators mounted on Na Mara would be 5m off the sea level. Maybe the mean wind speed might be a tiny bit less than my assumed 5m/s at that height but in that region of the output curve of the wind gen is more or less flat so it’s not going to make a lot of difference until cut in speed is approached (3m/s).

Turbulent airflow could certainly make a difference to output but this need not be negative. For instance, if cited on the aft deck, the generators can benefit from the redirection of wind off the sails when reaching and beam reaching. This increases output above what prevailing winds could achieve.

But I certainly take your point about the non laminar conditions at low wind speeds and admit that this may invalidate a proportion of my reasoning above

[Adelie]

NM:

JimCate’s point about about the height of the measurements is very important, unless you mount you wind turbine at the same elevation. Likely you will mount it at 3-4m and the average wind speeds will be significantly lower than the averages obtained from the met services.

Consider getting a vertical axis turbine. It offers quieter operation and more mounting possibilities. I would consider mounting one just over my head abeam the mast. It would need guard rails to keep the sails from abrading on the spinning blades.

I would suggest updating your profile with your general location and your boat make & model or “Looking” in the "Boat" category. This info shows up under your UserName in every post in the web view. Many questions are boat and/or location dependent and having these tidbits under your UserName saves answering those questions repeatedly. If you need help setting up your profile then click on this link: https://www.cruisersforum.com/forums...ml#post3308797

I would happily help more if the link above is not enough.

[celle2000]

Some would look past all the detailed cost benefit numbers and simply say - the place I need some battery charging is sitting in a quiet anchorage. I am protected from the wind so not getting much out of a wind generator . plus neither I nor my neighbours at anchor want noisy wind generators or for that matter diesel generators or people running their engines for hours. So solar it is. And if you spend 5000 on davits you are not just getting a place for solar I presume you are creating a place for the dinghy. If you have a canvas bimini you can fit flexible panels too.

[ArmyDaveNY]

Why suffer from the tyranny of OR, when you can have the genius of AND! I don't believe that one is better than the other. I think that each has their advantages and it is best to combine them so you can benefit from the strength of each, and compensate for the weaknesses of each. Good luck with your decisions and keep us posted on what you do and how it works for you. Fair winds!

[wiekeith]

I appreciate that the post is about wind vs solar, but having gone through a similar (with less maths…) exercise myself I ended-up with solar plus aqua generator – 240w of solar and a Sail-Gen aqua generator that produces about 10A at 6kts. The main downside to this combination is it’s lack of usefulness when at anchor on a cloudy day.

[Na Mara]

Adelie, I did look into vertical axis wind turbines (VAWTs) but I cold only find one (LE v150) and it had some shortcomings that I latter found out were fundamental to the breed.

The pros seem to be:
1. Cheaper than HAWTS per unit. You can get 2 200W LE v150s for the same price installed as a single silent wind pro.
2. You can mount an awful lot of them on a mast. I calculated that I could mount at least 16 of them (8 either side of the mast) for a total of 3.2kW of capacity. That would severely hit upwind performance and would cost 20000euros, but it could be done.
3. Zero maintenance and very reliable with only one moving part.
4. No holes in the deck or extra masts aboard.
5. Benefit from the slot effect a lot when sailing upwind.
6. lines, sails and appendages can't catch in the turbine.
7. don't suffer from losses due to yawing or pitching and otherwise deal with turbulence better.
8. Very quiet.

The cons are:
1. Due to the physics of the VAWTs and the fact that one side of the turbine is pushing the other side against the wind they are significantly less efficient than HAWTS (70% as efficient).
2. You really see this in their power curves. A pair of LE v150's is equivalent to a single silent wind in capacity and cost. The pair of VAWTs cut in at 4.5m/s, deliver only 10W at 5m/s, and don't produce their full 400W until 27m/s winds are upon them. Contrast that with the single HAWT which cuts in at about 2.5m/s delivers 20W at 3m/s and its full output of 420W at 15m/s. Even allowing for a 50% increase in windspeed with height up the mast the single HAWT is going to substantially outproduce the pair of VAWTs in light to moderate wind areas.
3. The high cut in speed and very low output at low wind speeds means that when I calculate the average output of a pair of these for the summer in the Baltic I get around 18W as the average output, which is way too little. You would need four to equal the average output of a single silentwind, and even then you would also have to account for the fact that the VAWTs are only producing half the time, while the HAWT is producing 97,5% of the time. You would need serious battery capacity to even out that kind of intermittency

So VAWTs are a nice idea but aren't really very practical.

(P.s. I updated my profile. )

[Na Mara]

Originally Posted by wiekeith

I appreciate that the post is about wind vs solar, but having gone through a similar (with less maths…) exercise myself I ended-up with solar plus aqua generator – 240w of solar and a Sail-Gen aqua generator that produces about 10A at 6kts. The main downside to this combination is it’s lack of usefulness when at anchor on a cloudy day.

Why not a single wind generator for most occasions and a hydrogenerator for long lightwind downwind legs?

[C420sailor]

I don’t have much (any) math to offer, but here’s a practical approach.

Start with solar. Easier/cheaper/less invasive to install. Want to take the panels off for some reason? Easy peasy. No huge masts to bolt to your hull.

See how that works, then decide if more solar is your solution, or if supplementing with wind is the way to go.

I don’t see wind alone being the solution to your problem.

[EngineerRetired]

If you are in Norway wind is better, if you are at the equator solar is better. Discussion over. LOL (Lots of truth though)

[wiekeith]

Originally Posted by Na Mara

Why not a single wind generator for most occasions and a hydrogenerator for long lightwind downwind legs?

Good question, and I need to rack my brain to come-up with an answer (it was about 8 years ago when I did the install). Having looked at the typical outputs of wind gens, at that time, and the potential noise issues, at that time, I think my starting point was solar as a main source of power with aqua as a backup. I also fitted a Sterling external alternator regulator, just in case, for those cloudless days at anchor.

[Na Mara]

Originally Posted by ArmyDaveNY

Why suffer from the tyranny of OR, when you can have the genius of AND! I don't believe that one is better than the other. I think that each has their advantages and it is best to combine them so you can benefit from the strength of each, and compensate for the weaknesses of each. Good luck with your decisions and keep us posted on what you do and how it works for you. Fair winds!

This is particularly true as many wind generator controllers come with inputs for solar as well allowing the two to work in unison optimally. The silent wind can be combined with 200W of solar on the standard controller for example. From my earlier calculations, 200W of unshaded solar should give about a 1kWh per day of energy on average in the Baltic summer. Together they would give nearly 2 kWh, which is way more than I need to keep the lights on underway or on the hook. The question is where to put the 200W of panels where they won't be shaded, won't ruin the lines of my boat, won't be in the way, and won't cost a lot to mount.