Using Cumulus with a rotatable AWS (on a windmill)

[beteljuice]

@Stuart2007

Another consideration for your purposes - The quckest 'rate' that the FO unit delivers data is approx. every 50s.

[peterh]

It does, however, sample wind data every two seconds. The values it supplies to the station are calculated from these samples.

[Stuart2007]

When considering a forward standoff, you would have to take into account that those vanes, at anything above 2 Bft, are going to ferociously deal with anything that gets in their way, including forward standoffs, however you interpret these. Since, depending on the mill type and location, these vanes may come all the way to ground level, that could limit our options for a forward standoff

I'd agree with betelgeuse - you would want to steer clear of the windmill altogether.
But I see another problem... windmills tend to be the highest object in their immediate surroundings. As a rule, a miller is genuinely pissed off when someone plans a higher building in his immediate vicinity, because that potentially puts his mill in a wind shade. So you'd have to come up with a bloody long mast to mount your wind sensors on and I think that's why the topic starter wants to mount his stuff on top of the mill. Which is where the direction vane would loose its orientation, aaaand we're back to square one.

A central static shaft would solve our problem, but I've never seen a windmill design that uses a central shaft. I think the dome rotates the same way as an astronomic observatory dome, with the bearing surfaces at the outside of the structure.

Thanks for your thoughts, one and all...
Yes...and back to square one. I have been round this loop a few times now, but there are in fact two different situations to deal with, because a mill only operates a small proportion of the time - it needs quite a lot of wind to 'work', perhapsa consistent 12mph+, and in practice even when driven hard it will on average work only one day in say 5 or so on average.

When it is NOT working, the sweeps (=sails) are parked at 45 degrees to the horizontal so the top of the mill is unobstructed and an excellent location for measuring wind. Of course, when it IS working, it is a rotten location, with those great sweeps shading it intermittently, trailing great vortices as they pass to ruin any measurement, particularly of direction. But in that situation, the wind direction should be just about equal to the Mill Heading, because the mill will be worked in the most efficient direction, dead into wind. Of course if the wind veers it may be off the wind until someone corrects it (a manual process on this mill).

As to fore or aft...well aft would be best in the hope the turbulence was less, but is on this mill already occupied by an old-fashioned - yes, you guessed it - weather vane!.

I'm thinking that I'll use Cumulus with a custom template so that as well as Mill Heading we show Sweep Speed, and warn folk that the wind data will be unreliable when the mill is working...

Thanks for all your ideas...any more are welcome!

[peterh]

a mill only operates a small proportion of the time - it needs quite a lot of wind to 'work', perhapsa consistent 12mph+, and in practice even when driven hard it will on average work only one day in say 5 or so on average.

That strikes me as odd.
I'm going to have a word with our local miller (where I get my flour), because I'm under the impression that his mill works more often than that... would we have more wind? I think not...

By the way, are you by any chance in Norfolk? Until I saw Norfolk, I always thought that The Netherlands had a lot of windmills.

[Stuart2007]

a mill only operates a small proportion of the time - it needs quite a lot of wind to 'work', perhapsa consistent 12mph+, and in practice even when driven hard it will on average work only one day in say 5 or so on average.

That strikes me as odd.
I'm going to have a word with our local miller (where I get my flour), because I'm under the impression that his mill works more often than that... would we have more wind? I think not...

By the way, are you by any chance in Norfolk? Until I saw Norfolk, I always thought that The Netherlands had a lot of windmills.

Hi Peter - I'd be really interested to know how much of the time it works. You may get more consistent wind - one problem we have is that the mill is shaded by trees etc from several wind directions. We need SW wind to work, but at least that is the prevailing direction... But modern wind turbines in the lowlands like us here in Sussex only expect a utilisation of sub 30%. Glyndebourne tested their site on a met mast for a year, and got...20%

[peterh]

I'll swear on my mother's beard, how did we ever get by without the Internet?
I found a wind table based on wind mill movement, devised by Jan Noppen, supervisor of waterworks in the 18th century.

Sorry for screwing up the table and a somewhat liberal translation...:

Code: Select all

Mill scale	Bft	Effect on a mill
0	          0	Stationary
1	          1	Only very faint movement
2	          2	Slow, but continuous milling
3-4	        3	Moderately slow to moderate 
5-6	        4	Milling with full sail
7-8	        5	70 to 75% sail 
9-10	       6	30 to 50% sail
11-12         7	25% sail
13-14   	   8	No sail
15-16 	    9-10	Milling is too dangerous
16+	       11-12	The idea of milling is patently bonkers. 

This indicates that mills will work from Beaufort 2 upwards... and Bft 2 starts at 3.6 mph.
That is a lot less than your 12 mph. So either the 18th century Dutch knew something about effectively designing wind mills that the folks who designed or built your mill didn't, or we have a misunderstanding somewhere.

Seeing as to how Jan Noppen was a water works supervisor, he may have been referring to drainage mills rather than grist mills or saw mills, because they have less machinery friction to overcome? I know next to nothing about these things...

I'll ask our miller when I get there.

[beteljuice]

@Stuart2007

When and if you have sensors for 'true' wind direction / speed and mill direction then it is reasonably straightforward to calculate the windspeed on the sail (same as caculating headwind on a runway). In a similar vein it is also easy to create advisories for the sailspeed and when the variable direction 'spread' which creates the 10 min averages is out-of-bounds (for airfields 60 deg), or when the mill needs to be repositioned.

It should also be possible to create a graphic representation (eye candy advisory) that enthusiasts and tourists would love !

Here's an old beteljuice plaything;
plaything
On both the 'map' and the windrose you would have a mill graphic to show its orientation.

This where you curl up and die or .... spend the rest of your life codong

[peterh]

... spend the rest of your life codong

Took me about 5 seconds to realise that this wasn't an onomatopoeia, but a typo.
You meant 'coding', right?

I hope to spend the rest of MY life coding, that's fer sure.

[beteljuice]

An oops moment, then I thought how can I bullsh*t my way out ?

The pertinent answer is here

[peterh]

Google to the rescue again...!

Looking at the weather, I definitely don't want to spend the rest of my life in Codong.

[Stuart2007]

(I'm posting this here because the preceding discussion is the context for the query, although the principle may be relevant more generally.)

I'm installing an AWS on the top of a postmill (http://www.oldlandwindmill.co.uk - the AWS is not yet live).

Because the mill is routinely pointed roughly into the wind, the wind vane will not record relative to magnetic or true north, but to "mill heading". The PC will know the current mill heading (either by manual entry or reading from a magnetometer).

Previous discussion (thanks all, including Steve of course) encourages me to process the Template files like this :
A) [Custom s.w.] updates T files to incorporate MillHeading, and build its own "MillHeading" database
B) [Cumulus] uses the (now updated) T files to process and upload to website.

Question is, how best to coordinate A and B to avoid file handling clashes. I'm inclined to get Cumulus to trigger A at the end of each upload, then A can wait (say) interval-1 mins, update T files and release before Cumulus needs them...

Would that be a sensible approach, or can anyone suggest a better strategy?

Many thanks again

Stuart

PS Ideally, if Cumulus had a set of "Usertags" I would set UserTag1 to Millheading, UserTag2 to ShaftSpeed, Usertag3 to TenterSetting etc

[mcrossley]

Get your mill s/ware to put your mill heading into a 'currentconditions.txt' file, Cumulus will pick this up (and delete the currentconditions.txt file) every time it processes the pages. Then in your web page you can use the <#currcond> web tag in a calculation to correct the current bearing.

[beteljuice]

Good thinking Mark !

There is no reason why currentconditions.txt couldn't be a multiple JavaScript declaration or array

[Stuart2007]

Excellent - one way or another I can pack the data in there, then parse it on the webpage.

Thanks

Stuart

[Stuart2007]

I now have this working fine on a test web page, thanks for the currcond tip.

Stuart