Windmills at Sherman

[windfind]

Hey Gang,

I really appreciate your support. But we all make mistakes and sooner or later most of us grow up and learn to apologize for them. Personally I was a slow learner in that way.....

So let's move on and get this thread back on the topic of "wind turbines and Sherman Island" before the moderators sends it to the "off topic" dustbin.

Beallmd is right. A human memory, after it has been dredged up and reconstructed by the brain's hippocampus many times, is incredible inaccurate.

And if that memory was originally laid down while OD'd on the dopamine generated by an early stage addiction to windsurfing then the memory keeps getting enhanced each time it is recollected. That is why you dad's trout kept growing each passing year.

So all I remember are those wild dawns 20 years ago at Sherman when dopamine and testosterone were rampant. And today the winds often just don't seem the same.

But in this case we don't have to rely on frail human memory. We have winds graph archives for each site in the Bay Area going back over a decade. And for some sites the number of windy days per season has clearly decreased. Perhaps the clearest example is Larkspur which as the average marine layer depth dropped because a less and less regular place to sail.

I have not had time to do a systematic study of this wind decrease but I spent enough time overlapping translucent winds graphs in Photoshop to have more than a subjective impression of the wind decline. We have a graduate student working on a related project so maybe that will bear fruit.

Meanwhile keep sending your impressions about the wind.

Thanks,
Mike Godsey
iwindsurf.com

[spennie]

Living in Thousand Oaks, I only get to actually sail Sherman once or twice a year, but I obsessively watch the graph here on iWindsurf all year. It seems to me (and this is only a feeling, mind you!) that Marker 14, AKA the Sign, runs about 7 mph slower than Marker 10 a lot of the time. It changes, too -- Just the other day I saw 14 actually higher than 10, probably because the wind was more west, maybe even southwest. But quite often it seems that there's a 7 mph difference.

Any Sherman locals agree? Hard to be sure from 400 miles away!

[beallmd]

Here again we may be dealing with significant LOCAL effects. We all remember Dirty Harry killed the bad guys there. See photos below; Obviously there has been significant construction there which may well be the cause. As an MD we deal with cause and effect or association vs causation constantly. So there may be a difference but why is a much trickier question-sorry don't mean to be pedantic here.

[andydavis]

If someone knows the power output of the turbines and the diameter of the blades, I can approximately determine the average loss of power on the water.

[jroberts]

[jroberts]

[windfind]

Hi Andy,

The degree of turbulence for turbines just downwind of first row of turbines is extreme. Although their blades seem to move steadily to the human eye the amount of torque and resulting power output varies radically from moment to moment the further downwind a turbine is from the first row of turbines.

The animated graph below from a recent wind turbine journal article shows the variation in power output from a turbine down stream from the first row of turbines over a brief time frame.

You are the engineer but I would guess that when you have row after row of turbines creating a whole field of increasing turbulence it would hard be to calculate the impact on a sea level site many yards away. Especially since the degree of impact on the surface wind hundreds of yards away, e.g. Sherman Island, would vary with the height of the blades above the water, the wind direction, velocity, temperature and atmospheric stability. Meteorology 101 would say that the last of these would be a critical factor as suggests in Turbine industry articles. I have played with wind tunnel simulations of the Sherman Island situation but none of the apps I use deal with a location that is actually below the level of the turbine base.

The famed Gorge forecaster, George McLean, who was lured away from iwindsurf.com by the turbine industry and now forecasts wind for power companies would be the one to approach with this question.

Mike Godsey
iwindsurf.com

[airwave]

Here's my guess:

Marker 10 is west of the windmills. And it is also open to any winds that tend to have any N component due to the low slope of the hills near it. That normal W flow through the Gate and then SW into the Bay heading up through San Pablo Bay should venture and follow the River direction to some degree , much like the Gorge winds venture through the Gorge. But, due to the thinner marine layer, the past few years, the Sherman winds tend to be less affected by the SW flow and more effected by the prevailing NW coastal flow or the NW component that does not follow the venture of the River. This makes the Sherman winds W and even NW more often than not. The W and WNW flow ramps up at Marker 10 but it is not able to flow down over hills to Marker 14.

So, yes, the windmills have an affect due to the N component of wind flowing over them as they steer into the river. But the windmills are not the problem. It is the reduced S component and the reduced venture, that enables the River winds, that causes the shortage of wind at Marker 14. When the wind does have a WSW component the River gets the wind before the windmills do, because the are north of the River and north of Marker 14. Therefore the windmills have little affect.

A side note. The kiters lover Sherman due to the WNW prevalence and do not like the more gusty slightly off shore component of the SW flow when it does happen. I have also noticed that when there is a more WSW pattern at Marker 10 the River farther east at Marker 14 tend to be windier.

If my guess is correct that leaves us with the reduced marine layer as the culprit and thankfully since there is no such thing as man made global warming the marine layer will eventually come back and Sherman Marker 14 will blow once again. Oh, yea, and since there is no such thing as global warming the windmills can then be taken down and Mark 14 might even blow on the NW days,
...NOT.

[andydavis]

[jroberts]