Thoughts on wind turbines?

[Detling]

You see a lot of these in China but I have not seen any anywhere else, several were several years old so must do the job, This is in Shanghai in the midst of skyscrapers with very disturbed wind and I understand the smog ruins solar power. They are used for pedestrian crossing lights and other street electrical requirements no idea of power but the UK uses 100 watt solar panels for similar jobs

[Murflynn]

3 minutes ago, Flyboy said:

I think these wind turbines are best suited to lumpy water boats where you get more wind.

correct.  ideal for boats on a mooring in an estuary that are rarely visited and of course cannot have a marina power hook-up - enough to ensure the battery runs the bilge pump. 

 

otherwise - don't waste your money.

[boots]

8 minutes ago, Murflynn said:

correct.  ideal for boats on a mooring in an estuary that are rarely visited and of course cannot have a marina power hook-up - enough to ensure the battery runs the bilge pump. 

 

otherwise - don't waste your money.

Agree 100%

[RufusR]

I agree with a lot thats been said here , I love the idea of something that produces power when the sun dont shine esp in winter but cannot get over all the disadvantages . I am closely watching the development of Vortex bladeless technologies as this looks like it could be the long sought answer for narrow boats esp as it acutally likes disturbed air oft found at moorings with trees etc , works in low speeds and is very light and quiet . Obviously brand new tech so needs to be proven , but they say they should have a nominal 100-150w unit out by end of year .. Watch this space . 

 

https://vortexbladeless.com/es/desarrollo-tecnologia/

[Machpoint005]

On 04/10/2020 at 12:47, MoominPapa said:

Rated wind speed: 13m/s 

 

Average wind speed (at an undisclosed height) 4m/s.

The output from a turbine is roughly proportional to the cube of the wind speed, so:

 

     4³ = 64

 

   13³ = 2197

 

That's 34 times as much. Divide the rated output by 34 and you have your answer - don't bother!

 

 

[Detling]

2 hours ago, RufusR said:

I agree with a lot thats been said here , I love the idea of something that produces power when the sun dont shine esp in winter but cannot get over all the disadvantages . I am closely watching the development of Vortex bladeless technologies as this looks like it could be the long sought answer for narrow boats esp as it acutally likes disturbed air oft found at moorings with trees etc , works in low speeds and is very light and quiet . Obviously brand new tech so needs to be proven , but they say they should have a nominal 100-150w unit out by end of year .. Watch this space . 

 

https://vortexbladeless.com/es/desarrollo-tecnologia/

So something like a very tall skinny person swaying about on your boat, there will be vibration loads trying to flex the mounting, presumably the roof , interesting. The idea is great but rather unrealistic for boats, will the resonance frequency be in the audible range rather like a transformer hum, amplified if mounted on a large surface like the roof.  I hope they are sucessful as it is not as visually intrusive as the normal windmill, nor will it be as noisy. They have a long way to go though to compete.

[IanD]

18 minutes ago, Machpoint005 said:

 

Average wind speed (at an undisclosed height) 4m/s.

The output from a turbine is roughly proportional to the cube of the wind speed, so:

 

     4³ = 64

 

   13³ = 2197

 

That's 34 times as much. Divide the rated output by 34 and you have your answer - don't bother!

 

 

Of course that calculation isn't correct either, because the wind doesn't spend all its time at the average speed, and as you say power increases very rapidly with wind speed. For the sake of argument, assume it spends 50% of its time at 8m/s (8^3*0.5=256) and 50% with no wind, that would average about 1/8 of the rated output. Still rubbish, but nothing like as bad as your calculation. In fact any distribution of wind speeds will always give more output than your calculation, the only debate is by how much -- but for sure, it'll still be way less than the 13m/s power...

[RufusR]

43 minutes ago, Detling said:

So something like a very tall skinny person swaying about on your boat, there will be vibration loads trying to flex the mounting, presumably the roof , interesting. The idea is great but rather unrealistic for boats, will the resonance frequency be in the audible range rather like a transformer hum, amplified if mounted on a large surface like the roof.  I hope they are sucessful as it is not as visually intrusive as the normal windmill, nor will it be as noisy. They have a long way to go though to compete.

Yes it will need anchoring properly to the roof and laying it flat when cruising would also be a challenge but hey those are the Engineering challenges that made Victorian Britain great .. LOL .. I love a challenge me .  I am sure there would be a solution . Just think the tech is very promising . But as with all things new proof of pudding will be in the eating . And yes it is a little ways off still me thinks . 

[Machpoint005]

48 minutes ago, IanD said:

>>Of course that calculation isn't correct either, because the wind doesn't spend all its time at the average speed<<

 

No, it doesn't, but in the long term it's the average wind speed that matters. So why is my suggestion incorrect?

 

 

49 minutes ago, IanD said:

For the sake of argument, assume it spends 50% of its time at 8m/s

 

Why? I bet it doesn't! We do not know the likely time history of wind speed.

 

In this country we tend to get days and days of relative calm followed by short periods of high winds. The effect is particularly noticeable close to the ground (by which I mean a few metres up) because of wind shear. This means my taking the average in the long term probably over-estimates, rather than underestimates, the output.

[Machpoint005]

I repeat that it's the long-term average that matters -- after all, we are using the energy to charge batteries.

[IanD]

18 minutes ago, Machpoint005 said:

 

No, it doesn't, but in the long term it's the average wind speed that matters. So why is my suggestion incorrect?

 

 

Using average wind speed to calculate average power only works if the two things (wind speed and power) are proportional to each other, and they are very definitely not (power is proportionla to cube of  speed). Here's a clearer example -- if the wind speed was 13m/s 32.5% of the time and zero the rest the average wind speed would be 4m/s, but the wind turbine power would be 32.5% of the rated value which is about 1/3, more than 10x higher than your number assuming the speed is always 4mph.

 

I can't see any simpler way to explain this, it's just the way the maths works ?

14 minutes ago, Machpoint005 said:

I repeat that it's the long-term average that matters -- after all, we are using the energy to charge batteries.

Yes it is the long-term average that matters, but the numbers aren't anything like as bad as you said -- the average power will still be much less than the rated power (maybe 10%-20% or so?), but much higher than the 3% that you came up with. It's about 33% for the UK fleet of offshore wind turbines, but I expect a small one on a boat would a considerably worse than this.

 

http://euanmearns.com/uk-offshore-wind-capacity-factors-a-semi-statistical-analysis/

Edited October 8, 2020 by IanD

[Machpoint005]

I understand that, but my initial estimate was used to illustrate the point about rated output, which does not seem to be in dispute. As I say, we do not know what the time history of wind speed looks like, but there will be a lot of relative calm, and your suggestion of 13m/s for 32.5% of the time is ridiculously high. You might be lucky and get 13m/s for 5% of the time -- at a height of 10m. 

[IanD]

7 minutes ago, Machpoint005 said:

I understand that, but my initial estimate was used to illustrate the point about rated output, which does not seem to be in dispute. As I say, we do not know what the time history of wind speed looks like, but there will be a lot of relative calm, and your suggestion of 13m/s for 32.5% of the time is ridiculously high. You might be lucky and get 13m/s for 5% of the time -- at a height of 10m. 

That wasn't a suggestion, it was a simple example to try and explain the numbers to you and why you can't use the average wind speed to calculate average power.

 

As I just said, the load factor for the UK fleet of offshore wind turbines (average delivered power/rated power) is about 33%, which does take account of distribution of wind speeds. I wouldn't expect a small one on a boat to be more than half this so maybe 15% -- which is why I gave a 10%-20% range to cover uncertainties.

 

Nowhere near the rating, but still much higher than your 3% number ?

Edited October 8, 2020 by IanD

[noone]

Had one years ago,it drove me crazy with the constant and varying level of noise vibrating through the boat...Went solar,never looked back!.(The day the sun doesn't rise,electricity will be the least of our worries!!)?. Please keep posting if you do invest in one.I have been told by people the modern ones are quieter...You may start a wind generator resurgence if it performs well!?

[Machpoint005]

On 08/10/2020 at 14:14, IanD said:

As I just said, the load factor for the UK fleet of offshore wind turbines (average delivered power/rated power) is about 33%, which does take account of distribution of wind speeds. I wouldn't expect a small one on a boat to be more than half this so maybe 15% -- which is why I gave a 10%-20% range to cover uncertainties.

 

Nowhere near the rating, but still much higher than your 3% number

 

Your offshore load factor is for a typical hub height of 100 to 150 metres. 

A narrowboat wind turbine has a hub height (or the equivalent for a vertical axis turbine) that is nowhere near ten metres.

Take wind shear into account and your 15% load factor is over-optimistic, to say the least.

 

By the way, I didn't suggest that my original calculation represented a long-term average (even though that is what matters). It was there to show the disparity between the rated power and typical power output. A wind speed that even reaches 4m/s at a height of five or six metres is not going to happen all that often on a canal, for reasons already explored on this thread.

 

 

Edited October 10, 2020 by Machpoint005
"to" not "so"

[IanD]

12 hours ago, Machpoint005 said:

 

Your offshore load factor is for a typical hub height of 100 to 150 metres. 

A narrowboat wind turbine has a hub height (or the equivalent for a vertical axis turbine) that is nowhere near ten metres.

Take wind shear into account and your 15% load factor is over-optimistic, to say the least.

 

By the way, I didn't suggest that my original calculation represented a long-term average (even though that is what matters). It was there to show the disparity between the rated power and typical power output. A wind speed that even reaches 4m/s at a height of five or six metres is not going to happen all that often on a canal, for reasons already explored on this thread.

 

 

All true, but I was simply pointing out that your calculation was wrong, which it was ?

[Tony Brooks]

Actually I very much doubt any long term average wind speed is of any consequence to boat users. They want either a trickle charge when they are away from the boat or a usable charge NOW and for the next few hours and its the now bit that is important and very difficult to forecast.

[Detling]

6 minutes ago, Tony Brooks said:

Actually I very much doubt any long term average wind speed is of any consequence to boat users. They want either a trickle charge when they are away from the boat or a usable charge NOW and for the next few hours and its the now bit that is important and very difficult to forecast.

A lot would be happy with 2 amps for 24 hours a day in winter. Not really enough, but good enough to top up batteries, augmented by febble solar, after a morning engine rumble, while they are out at work.

[IanD]

29 minutes ago, Detling said:

A lot would be happy with 2 amps for 24 hours a day in winter. Not really enough, but good enough to top up batteries, augmented by febble solar, after a morning engine rumble, while they are out at work.

A few amps is what you'd usually get, that's fine so long as people don't expect anywhere near the rated output and can put up with the noise.

 

But even in winter solar panels typically produce about 25% of the summer output -- a single 400W panel will average 1.5kWh/day in summer (not that this is also much less than the official rating...) and 0.35kWh/day even around Xmas, which is 30Ah at 12V. Probably more even in winter than the wind turbine (and much more in summer), and probably more consistently. There's a very good reason lots of people use solar panels and hardly anyone uses small wind turbines...

 

Edited October 11, 2020 by IanD

[Detling]

2 hours ago, IanD said:

A few amps is what you'd usually get, that's fine so long as people don't expect anywhere near the rated output and can put up with the noise.

 

But even in winter solar panels typically produce about 25% of the summer output -- a single 400W panel will average 1.5kWh/day in summer (not that this is also much less than the official rating...) and 0.35kWh/day even around Xmas, which is 30Ah at 12V. Probably more even in winter than the wind turbine (and much more in summer), and probably more consistently. There's a very good reason lots of people use solar panels and hardly anyone uses small wind turbines...

 

Those figures are from panels mounted on a roof at 45 degrees facing due south and with no shading, not seen many boats like that, real world figures fron 12 volt boating group on facebook suggest 10% of rated in Decmber and January is best you can reasonably expect on a boat due to angles and shading at times.  But amps for pounds for 9 months of the year solar is  better, just the 8 weeks round the winter solstice, when every amp counts.