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VWAT Vs HAWT?

04/20/2013 12:44 PM

I live OFF-Grid; We are looking for a low cut-in start speed - efficient wind generator to off-set my solar/generator system. Not to charge or operate the system, more to trickle charge at night or when severely overcast, for winter use when solar is reduced and winds increase. Essentially we want to reduce the dependency on our diesel generators. I know that even on cloudy days we get some solar charging. Height not much of a problem as we live on a 40 acres on the side of a mountain that gets 2-3mph daily avg winds. Mornings & evenings we get sustained 7-10 mph winds. When storms come thru, we get wind speeds in the 20-60 mps gusts. I like/prefer the VAWT, they started out being great for low wind speeds, but appear to have troubles qualifying their claims and are high priced. I have read that the Darrieus Rotor is/was the more efficient VAWT, but there are so many variants now I'm getting lost. Suggestions - recommendations Please.... Location - Murrieta, California. USA

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#1

Re: VWAT Vs HAWT?

04/20/2013 2:23 PM

WHAT?

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#2

Re: VWAT Vs HAWT?

04/20/2013 2:28 PM

First off: Welcome to CR4!

Unfortunately, I am not the best person to answer your question. However, whenever the subject of a VWAT VAWT hits CR4 it peaks my interest. I did a search ("Search all of CR4" - on the right side of your screen), on both VAWT, and Savonius.

One result I found interesting was: http://cr4.globalspec.com/thread/34533#comment360035 Posts 4&5 by Andy Germany, has some good links to check out.

There are a lot more than I can filter through at the moment. If memory severs me, there was one ~4 years ago where someone gave the calculations. I just couldn't find it.

Have fun!

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#9
In reply to #2

Re: VWAT Vs HAWT?

04/21/2013 12:46 AM

Found it! http://cr4.globalspec.com/thread/35260#comment368229 post #9.

That should give you what you need to determine if it is worthwhile. Unless you are handy (and have a bunch of 55 gal drums lying about), the low wind speed is probably not going to make it viable for anything other than trickle charging.

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#12
In reply to #9

Re: VWAT Vs HAWT?

04/21/2013 10:54 AM

Good stuff! Sorry, engineering equations not my strong suit. Just a simple knuckle dragging sheet metal, hyd servicing retired mechanic... Since I know that we won't get more than trickle charging, we are fine with that. But, not at the price that some of those units cost! I guess that a complete axis wind turbine system under $7,500, is possible... After upgrading our current solar system, we know that the tie-in components won't come cheap - if the quality is there. Don't want or need to fry our existing solar system components.. It's one reason I reached out to this site, for some intelligent ideas, not just salesmen making a profit! Thank you all!!!

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#3

Re: VWAT Vs HAWT?

04/20/2013 2:59 PM

Each design works best under different wind conditions.....Here's some good examples for low RPM designs....





http://windpowerauthority.com/top-5-low-speed-wind-turbines/

http://www.windbluepower.com/Lite_Breeze_Low_Wind_Generator_Kit_p/cy-low-kit.htm

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#4

Re: VAWT Vs HAWT?

04/20/2013 4:00 PM

Sorry about the earlier Post, should be - VAWT Vs HAWT

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#5
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Re: VAWT Vs HAWT?

04/20/2013 4:55 PM

What about watts ? Price range ? Noise limit ? Height limit ?

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#10
In reply to #5

Re: VAWT Vs HAWT?

04/21/2013 10:25 AM

Watts - just trying to keep enough energy/watts in the L16 deep cycle solar batteries (48 total), at night so generators don't come on. Price range - reasonable Noise - have heard that HAWT's get noisy, we live in the mountains, don't want to create that hum that HAWT'S create Heigth - 35', even that draws away from the environmental view Did some research 4-5 years ago when we still lived in the city. Thougt VAWT's were "cool", innovative, less prone to mechanical problems and sounded to be able to capture the wind better than HAWT's. But their cost was high and not affordable. So we did not go any further, in the city. We're now retired, in the country. Live completely off-grid! 56 solar pnl's, 48-L16's, diesel generators as back up Pwr and propane to last a year. Trying to only buy diesel & propane when prices are low during the summer. SO, I'm no engineer, but i have mechanical ability - just not electrically gifted! Have seen the proliferation of H & V axis wind turbines to make my head spin! Which is why I reached out. I thank Everyone for the comments and ideas!

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#6

Re: VWAT Vs HAWT?

04/20/2013 5:56 PM

B&Q (usual disclaimer) used to stock them retail; one could just buy one at a store with a credit card. They no longer stock them there so maybe a Google search would be the best way to find alternative suppliers, perhaps?

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#7

Re: VWAT Vs HAWT?

04/20/2013 9:06 PM

Generally HAWT tend to be more efficient on a per dollar basis and on a size basis.

The various advantaged envisioned in VAWT designs rarely translate to the working system in any degree sufficient to justify the higher price/reduced output.

The fact that a blade on a VAWT is moving against the wind for half of each revolution, goes a long way to decreasing the performance.

.

So, tell us a little more about your property... You say it is on the side of mountain. How near the top?

One way to improve wind power output and consistency is using a tower. Wind if often blowing more consistently and stronger at elevations attainable with small towers.

What are the restriction on height of such structures in your area?

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#11
In reply to #7

Re: VWAT Vs HAWT?

04/21/2013 10:39 AM

See post #5 my reply... Also, during past research (4-5 yrs ago), VAWT's were being touted as a great inner city alternative to the HAWT, they were supposedly quieter. Supposedly less moving parts. But they were too expensive. Heigth limits - am currently looking into, believe not more than 35'. Also my elevation is 2500'. We are 2/3's - 3/4's up the side of the Mtn., which is about 3,200'. We literally live on the side of the Mtn...

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#18
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Re: VWAT Vs HAWT?

04/21/2013 10:28 PM

At your height I'm sure there will need to be considerable reduction in planned horsepower output in thinner air but there should be wind charts for that elevation which I'm sure would require larger blades for the same size generator used at sea level. I'm sure you could find someone in the axial flux wind generator forums that have the same application as you have that are not salesmen. Google search "axial flux generators" You might even stumble into a website about a new diesel genset that is very efficient and contains the axial flux design that might reduce your fuel usage

axialflux@yahoogroups.com is a great forum to learn. Maybe others can suggest more.

Do you have a mountain stream that you could legally tap into for water driven generator? They talk about those DIY projects using axial flux designs on water applications in several axial flux forums.

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#8

Re: VWAT Vs HAWT?

04/20/2013 9:29 PM

Regardless of which style you choose any wind speeds below 5 -7 MPH hold so little energy they are not going to serve any practical purpose and those above 40+ MPH tend to be too high to fully capture their energy content and usually are highly destructive to most wind turbines that are not locked down during those events.

Now relating to what's on the market the HAWT have the best power outputs Vs size and cost plus they handle wide ranges of wind speeds quite well.

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#13
In reply to #8

Re: VWAT Vs HAWT?

04/21/2013 11:09 AM

At night when there is little drain off the batteries, trickle charge is all we are looking to achieve. During past research I thought the VAWT's had a lower cut-in speed and at high winds, were less prone to internal damage at high speeds. I was even looking at small wind turbines used for sailboats - still am. Over speed protection is a concern, but several manufactures of HAWT's support variations of stalling the blades or gearing down for self protection... A lot was the looks of the Vertical look. Something new and different.... IF HAWT actually has a lower cut-in speed, then I will go that direction, especially being retired, need to keep the cost down... Thanks

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#14

Re: VWAT Vs HAWT?

04/21/2013 2:09 PM

Sheet metal I bleed when I even think about it but Ed Lenz has a good website about his small vawts and others windgenkits.com build Lenz kits that any tin bender could master if you want to try a DIY kit on a small vawt design that won't break the bank. Ed has been very helpful with my questions windstuffnow.com

If you decide vawts aren't enough hp Hugh Piggott's site is a massive source for info on his axial flux Hawts and many followers have started their own sites to help DIYs build his furling design hawts from the ground up including winding and casting the axial flux generator yourself. Others offer schools you can attend and build a generator like Piggotts design which appears to be completely open source

You already have the battery banks which makes many people shy away from wind

I had a old Zenith radio battery wind charger but feared the blade would break with tip speeds over several hundred mph as it was non-furling which is why I like Vawts but you have to face allot of area to get hp and sometimes that's hard to do with low speed vawts

Windbluepower.com has a Hawt the uses GM car alternator conversions with PM magnets that is another source for low wind speed equipment that you wouldn't have to hock your brake and shear to buy it and it's made here in Kansas.

Good luck to you,

John

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#16
In reply to #14

Re: VWAT Vs HAWT?

04/21/2013 6:30 PM

Those are good suggestions for helpful websites.

Another one that you may find useful:

Otherpower.com

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#15

Re: VWAT Vs HAWT?

04/21/2013 5:36 PM

Have you given any consideration to the time when you will have to replace the lead acid bricks you are using for storage. LiFePO4 cells will store more power with less resistence and discharge the same way. Lead acid are getting only a small fraction of the usable power they for which they are rated. Their discharge is slowed by their own internal resistence. LiFePO4's will deliver more amp hours with less actual stored amp hours as well as more longevity of the cells themselves. Something you might wish to consider.

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#17
In reply to #15

Re: VWAT Vs HAWT?

04/21/2013 8:25 PM

Will have to look into those batteries. This off-grid stuff came fast & hard! Not sure what type they are yet, but i did look at gel cells but their life span was not well, I actually am waiting for batteries to improve with auto's. Then I'll have a real shot of better batteries. I still have at least 5 years on mine..... I equalize every 4-6 weeks, they work fine during this time of year through Oct-Nov.... In winter is when I'm looking for the wind turbin to augment solar, so as to reduce diesel dependency,,, and cost!

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#20
In reply to #15

Re: VWAT Vs HAWT?

04/22/2013 5:58 AM

You wrote:- "Their discharge is slowed by their own internal resistence."

Forgetting the bad spelling (by the way, the CR4 spellchecker would have corrected if you had used it!) for the moment, you wrote it so loosely, that it does not really mean anything....

So assuming that you meant "in comparison" with another battery type, then you are mainly wrong, as for example, Lead Acid batteries have a really low internal resistance and can supply very large currents easily, which is why they are still in usage for cars despite relatively low efficiency, large size and heavy weight......if there had been anything better at a comparable price, we would all be using the better one!!! We are not!!! LA is still king.

Lead acid technology still has a bright future for many years to come.......though maybe not in Boeing passenger aircraft !!!

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#19

Re: VWAT Vs HAWT?

04/22/2013 5:44 AM

I just had a thought or two that might help you further:-

Are your batteries fully charged each day by the average amount of light that they receive, or are they only partially charged?

Even partially charged, are they charged above 70% of their capacity?

Do the batteries gas at some points of the charging cycle? (This may or may not be easily visible, but does require adequate and safe ventilation)

Do you have to top up the batteries (assuming not SLA type) with distilled water ever?

If you can answer "Yes" to any of the above questions, then you are wasting power....

Then possibly I would state that you may have more power available from sunlight than battery storage to store it efficiently, then the next question is:-"How much more?"

So more batteries are really needed before you buy/build a windmill......

I forget exactly what the "sweet spot" is for lead acid batteries for efficiency, but let us say it's 70% as a place to start with. Charging above 70% only drops efficiency even further, effectively throwing away power.

Furthermore, charging above 70% will cause gassing, eventual water loss and eventually a shorter working life for the batteries. So it would be cheaper in such a case, to add battery capacity, but only charge to 70% (or whatever the best point for efficiency is!), this will give you "more" power to use......

I looked around on the web for some good infos, one of the best written in an easy to understand way was here (though there are many, many more that should not be ignored!):-

http://www.solar-facts.com/batteries/battery-charging.php

There I found this paragraph which really says it all:-

Battery Efficiency

The Lead Acid battery is not 100% efficient at storing electricity - you will never get out as much as you put in when charging. Overall, an efficiency level of 85% is often assumed.
The efficiency will depend on a number of factors including the rate of charging or discharging. The higher the rate of charge or discharge, the lower the efficiency.
The state of charge of the battery will also affect charge efficiency. With the battery at half charge or less, the charge efficiency may be over 90%, dropping to nearer 60% when the battery is above 80% charged.

There is far more at this and other web sites, a lot of this needs to be read and fully understood....

I hope this helps.

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