Wind power and daylight

[DamonHD]

On the last 10 days' data I'm seeing most of the available windpower in the day, eg when solar PV is also available.  Of course it would be nicer if wind power was available exactly when the PV was not!

(See the table in today's update on http://www.earth.org.uk/wind-power-pilot-autumn-2007.html for the stats.)

On real installations like many of you are running, do you consistently tend to get more power in the day time, or is this just odd and I should collect a lot more data?

Rgds

Damon

[Flux]

Probably much depends where you are. Here, UK Midlands the wind tends to start about 10 o'clock in the morning and dies away about an hour before dark. On normal days there is very little available energy at night.

In times of storms this changes and then wind tends to go all night and sometimes the night time wind is higher than by day, but this accounts for little of the total energy.

Most seem to think of wind for 24 hrs a day, this may be true in some areas and if you are in one of those regions power output will be much higher. It is only when you study wind power that you realise that many of the common assumptions are wrong.

Also I suspect that generally in this area most would say that March was the windiest month but again it is usually December, although the highest monthly output I have seen was in February.

Flux

[DamonHD]

Hi,

OK, so you see the same mid-morning to dusk power peak that I'm seeing.  I may have passed my first minor sanity check!

Does that relationship (mid-morning to dusk) apply in December too, when wind would be most useful to balance solar PV?

Given that the December day is shorter does that mean that the wind is blowing the same power per daylight hour as in summer (ie for fewer hours and therefore less energy per day) or much more per daylight hour (which would fit with the stats as I understand them, ie much more wind energy per day mid-winter)?

Rgds

Damon

[GeeMac]

Generally speaking, when the sun comes up it heats the earth. Heat rises. As the heat ascends it stirs up the atmosphere and we perceive that as wind. When the sun sets the source of the agitation is removed until the next day.

Add to this larger and nearby weather systems and the mix is complete.

However, a scientific study recently found that at a height of 80 meters over 4/5 of the planet there is enough wind to supply well over five times the power needs of mankind.

80 meters is about 250 feet.

[DamonHD]

Hi,

Yes, I hear what you say and it fits the facts, though I might also have hoped that the end of the sunlight's agitation might cause some interesting settling activity.  Anyway, I am collecting my stats to see what happens!

One paper I saw online yesterday suggested that at some heights and in some seasons the typical behaviour is reversed in terms of wind speed by hour of day.

80m tower!  Considering my freehold from corner to corner diagonally is maybe 15m at most, I don't think I'll be able to put in the guy-wires for that turbine!

(BTW, I exceeded ~3hrs usable wind yesterday, and may be on for about the same today.)

Rgds

Damon

[Capt Slog]

Flux,

Where abouts are you?

I always imagined you in the USA and now it seems that you are in my neck of the woods.  Don't worry, I'm not about to come visiting, but was just interested for a related reason.

[Flux]

I have a feeling that the same thing applies during the winter but it is masked by the fact that most of the time the presence of storm systems keep the wind going 24hrs a day and result in much higher winds during this period.

Typically the total power captured during the winter months may be 5 times that of the worst summer ones. So yes wind does probably more than balance the fall off of solar during winter.

This is probably true where you are but it may not be something that others ought to take too much notice of. I really have no idea what happens in other parts of the world.

Flux

[Flux]

Middle England, in the worst wind area of the UK. Average wind speed from Golding about 9mph. From my measurements it is nearer 8. Not really a viable area for serious wind power.

Flux

[DamonHD]

As it happens today has been such a dull/dark day that I have not had any excess power at all for off-grid time for my server.  This is the worst since my RE system installation!

Plenty of power left for my lighting though, at least so far, I hope!

It will be really instructive to see when I can come off-grid from now on, especially once my MotorWind is added to the mix.

Rgds

Damon