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Hi all - this is my first post. Firstly thank you to all for the amazing amount of info you guy's put up.
My first question is after reading alot, both positive and negative about ebay grid inverters i wondered what stops someone buying a good quality inverter here, with islanding etc, and plugging it into the wall at home. ( i rent so i can' fit it to the house. I'm not sure what they will think of the VAWT but that's my biz for now:-)
Second, i have intended to build a 12v system given that i will use both wind and solar. What are the advantages of say 28v since i notice many of the inverters are this voltage.
Thanks for the help and please don't bark at me - i did look it up first.
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 10:23am 28 Jun 2010
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Hi Razzle
With a bit of ingenuity you could make good portable system as long as there is a sunny back yard, six 200 watt 24 volt panels on a tracker and a 1200 watt plug and play will certainly help reduce your electricity bill.
Should be able to supply six to seven KW a day on an annual average. As for the wind turbine you would need good access to wind, lack of obstruction at 5 meters high as that is as high as a transportable tower is practical, I would recommend that you purchase a wind speed reading weather station as it will record wind speed for you.
You will need 5 ms minimum average to be useful for your application.
For your situation I think you would be better to purchase a couple of extra panels and spend the money / effort on a good tracker and MPPT regulator to maximize the output of the solar.
A 24 volt system allows you access to more useful equipment at little extra cost, wires are more economical as the AMPS is half of a 12 volt system.
All the best
BobFoolin Around
readyakira Senior Member Joined: 17/07/2008 Location: United StatesPosts: 114
Posted: 02:00pm 28 Jun 2010
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First I think when you say 28v you mean 24v. Those inverters are probably rated at 28v max. 12v is nice for the reason of most things using dc are 12v or less, but as stated 24v systems can save ALOT in cost of wire. Amperages are less with 24v then 12v and much easier to work with. when you get up to the 48v systems then there is a new danger of the voltage being high enough to easily go thru you and kill you. Although alot of bigger systems do use higher voltages. I personally am using a 12v system, but am trying to make sure I design it to be easily converted to 24v once my power availability becomes high enough to warrent it. Right now I am only able to produce about 10amps of juice @12v so wire cost is cheap.Don't you think Free/Renewable energy should be mandatory in new buildings?
Robb Senior Member Joined: 01/08/2007 Location: AustraliaPosts: 221
Posted: 12:43am 29 Jun 2010
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In short: Rules and regs.
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 01:54am 29 Jun 2010
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Hi Robb
Many years ago an acquaintance of mine owned a sawmill that was driven by a steam engine, when the electricity came up the valley they talked him into converting the mill to electrics, after the first bill he connected his steam engine to a 65 HP 3 phase motor and drove it to feed back into the grid, no more power bills and he got rid of all the waste from the mill as at least 50% of a log is waste by the time it goes out in timber.
Later when I set up my engineering workshop the power wasn't good enough to run the big welder 500 amp Lincoln welder so I piggybacked a 50 KVA alternator to the power while it was in use, done by electrician with a phase isolation relay now called islanding and all was well, at one time I run into the local mains to provide power to local houses when the substation was hit by lightning at the request of the electricity supplier. Took them 2 weeks to rebuild it.
No feed in tariff in those days as there wouldn't be if a plug and play unit is plugged into a power point these days, as long as it has islanding, and done at the risk of the owner. Its easier to get forgiveness than permission.
Of course we wouldn't do that would we, as it mat reduce the profit of the utility company and send them broke the we wouldn't have any electricity. Shame Shame.
Thanks for the various replies.
Some of the inverters i have seen have stated
DC Input Voltage
DC 28–55V(solar panel/wind turbine)
AC Output Voltage
AC 90–130V or AC 190-250V
Hence my 28v question. I didn't understand this given 2x parallel 12v is 24v.
I understand the 24v idea must be similar to grid transmission being transformed down closer to point of use to ensure less loss!?
Robb: As far as Regulations go on the inverter, i questioned my power company and got the answer i hoped for and expected. (Not from the guy on the front desk of course.)
"It is not illegal and we can't stop you but you are responsible for it and any damage it might do."
So i guess - do it properly. So this spawned my question about the inverters, i don't want to be stupid and i am a bit concerned at using an eBay inverter although a small one seems harmless.
I guess i was hoping for some more specific advice regarding hooking up a good quality inverter to the grid via a power point.
P.S. I am very excited i found my second F&P motor yesterday!!
Thanks
Darren.
Edited by Razzle 2010-06-30
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 04:13am 29 Jun 2010
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Hi Darren
The float voltage for 24 volt nominal is nearly 28 volts, battery type dependent, and on a sunny day it can go to 32 volts,to high for the batteries without a regulator and it will boil the batteries to much, so it will work on the inverters you are looking at, there is also a 1200 watt unit that I haven't tried yet but I imagine that it would be the way to go, you would need at least six 200 watt panels, you could use it without batteries direct off the panels as it is designed to do OK,but will switch in and out a bit due to cloud obstruction. Using batteries has other advantages as you can use the batteries to power low voltage devices as you develop your system.
As for the getting a good quality Auzzie made GTI great idea but the cost may make it impractical, try a cheeep one first to prove you concept, and make a portable tracker to get the best from your panels, then invest in a quality inverter as funds are available.
Hi Bob.
I actually would rather go to batteries then to inverter but I was sure I read somewhere that going to batteries first will increase losses in the process substantially. This all started just with the idea of running the fridge but i got greedy :-P ( and the wiring to my rental property is easier with inverter)
Also if I can mention that my first port of call will be wind power. This I can do at very little expense. Once I see results I will see benefit in spending several hundred dollars buying solar cells and tracking bits. I know most would say to start other way but I want to build a vawt - I just want to... it's been a kinda dream since I was a kid and got my first motor out of a washing machine and didn't know how to implement it.
Darren.
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 08:21am 29 Jun 2010
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Hi Darren
You are right there some small losses in maintaining batteries charged but the advantages of having them as a power sink is important, as with a wind mill the voltage can vary over a large range if not loaded properly and can damage high voltage sensitive devices like a GTI unless held in check, solar panels don't have the high voltage problem unless they go open circuit, and then there is nothing connected to damage.
I look forward to hearing about your VAWM project
Thanks Bob.
So am I. Heading into the big unknown at the moment but having a lot of fun in the process. I have a friend lined up who is able to help with a star/delta switch and I am trying to decide which blades to make now. So much to learn.
Thanks for your comments.
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 10:40am 29 Jun 2010
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Hi Darren
I see you are using F&P motors for your mill, I haven't used a F&P for a VAWM yet but have done a few tests in the lathe at various speeds reflecting a 3 foot and 4 foot mill I hope to build later this year when some of the other projects are under control. I have found that a, as is star without reconfiguring is best for a 3 foot dia mill and for a 4 foot mill there is enough torque to drive in delta.
What I have played with is a conventional switch mode power supply that works on AC and DC input and is rated at 350 watts, at 300 rpm reflecting a 3 foot mill at 8 ms airspeed. With a star connection on the Alternator, three phase rectified gave 300 volts DC into the modified SMPS and full output.
On the Delta connected 4 foot mill simulating a wind speed 10 MS 350 rpm there was enough power to load a power supply on one phase to 350 watts.
These are simulations on the VAWM, and speed tests on the motors mounted in a lathe.
I would expect the actual results to be slightly less in practice, In the position that I am placing the Mill is exposed to an average win speed of 5 ms but with wind up to 15 ms at times, From July to October so it would be worthwhile.
My mills as planned are 3 ft in diameter 8 ft high and 4 ft in diameter 10 ft high with 6 airfoil blades 10" cord and symmetrical 20% thickness ratio non critical laminar flow, with vortex generators every 4" on the outer and inner surfaces of the airfoil.
The airfoils will be made of laminated hoop pine timber mounted at three points on their length for support. The rotor will be mounted in an external steel frame with the 1.5" top bearing on a spider plate connecting to the outer frame, the bottom beating is a 2" industrial flange unit to carry to weight of the rotor.
While others have gone for the reconfiguring the windings to lower voltage for direct rectification to 12 / 24 / 48 volts I believe it is more efficient to use high voltage. So far it seems that way but only time will tell for sure as there is a big difference running in the lathe to blowing in the wind.
Hi Bob.
So much to learn.
I need to get the motor up so i can feel it's torque requirements to design blades but to wire it i need to know speeds of turbine etc. Chicken or egg.
Would you mind explaining in more detail why you chose to leave the motor stock?
What are the advantages here and will they apply to a 12v system.
I was intending with the two motors to wire them in stages for different speeds.
Does anyone else have an opinion on this?
Everywhere i read they rewire them.
Another thing, the first motor i got was an old individual magnet motor. When i spin it by hand at a reasonable pace i get around 14v AC off ... one phase? (across 2 terminals) The second motor has 4 magnets (or poles) in one piece and gives me about 50v on a similar spin. Why? and how can i utilize this in wiring it?
Thanks and please let me know if I am bugging you with all the questions. From a standing start I have actually done a lot of research over the last few months.
Darren.
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333
Posted: 09:08am 30 Jun 2010
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Hi Darren,
I for one dont like un modified stators and think they are out right dangerous, as the voltage out can be high enough to kill you or someone else if there is a fault.
Bob has messed with this stuff for a while and should know what he is doing, but the simple fact you are asking indicates you are not so so adapt with the dangers.
I think it is bad advice to recommend not rewiring the stator for new comers to wind energy.
Rewire the stator to give a safer lower voltage and it will also increase the amps out for the lower voltage you require. At least you can sleep at night knowing saftey is on your side.
Im not the expert here on rewires but it sounds like you have an early type F&P and the later style F&P.
Have you had a look at the information on stator rewires on the front pages of the forum.
There is a lot of information there that migh answer your questions in part.
Pete.
Sometimes it just works
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 01:32pm 30 Jun 2010
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Hi Bob,
I would rewire the F&P, as there are no grounds for higher efficiency with the same load, barring deficiencies with transmission wiring for low voltages. The diode losses will be the same at the final rectifier, unless synchronous rectifiers are used and then the gains do not outweigh the complexities.
You have mixed data for the output power quoted. I presume the windmill is 1m in dia and 8ft high, and a VAWT. I am not sure about an object this large rotating at 300rpm would be something I would want to be close to, even 8ft up.
Gordon.
become more energy aware
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 02:49pm 30 Jun 2010
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Hi Gordon
As I stated in the post I have been testing things electronic in a static situation and the actual mill is being rebuilt with bigger bearings and I am still laminating the blades at this time, the test one was done with 3 salvaged gyro-copter blades which turned out to be inefficient so the decision to make the lamina flow blades CL 2.2 with vortex generators 1.6 CL without this allows a extra 16 degrees of rotation before the blade stalls also provides lift on both surfaces instead of 1 on the Clark Y Major contract.
The gyro blades where Clark Y CL 1.4 they achieved 400 rpm on 36" diameter 10.5 ft high and without load during 10 ms wind. The gyro blades run at 550 rpm in aircraft use so loading on them was low in this case. The rotor assembly was static balanced to 2 grams so very little vibration, the wind effect caused some vibration due to turbulence in the unloaded rotor also only three blades so not that good, higher wind gusts at the time didn't give much extra rpm so I believe the flow disturbance in the rotor has reached limit. Rotation Speed readings by a laser strobe rev-counter Airspeed by a hand held turbine digital unit.
The reason I went for high voltage is the installation site is 100 meters from the shed and also it gave a lower cut in speed to start charging. the SMPS wasn't happy with the varying frequency on the AC output so I connected the DC and it was happier working from 80 volts to over 300 volts, it is rated to 354 volts DC and 80 to 250 volts AC 50/60 Hz switch speed 25Khz. Rated output 350 watts overload 125% cutout
Rotors tested 60 and 100 f&p. The idea for the smaller diameter was to get a higher rotation speed to drive the f&p without gearing as was needed on the larger mills I made years ago.
The information I gave was what I was doing and it is up to all to do whats best / easiest for them, for what I am doing this is the best for what I need, the rewiring to 24 / 48 volt nominal would be to lossey over the distance I need.
I agree with you for a simple system Darren is doing I would go for a 24 volt configuration with a MPPT regulator and caps for best range of RPM output, I am awaiting your testing of the 3 cap system you propose to try on my HWT to lower the startup. I mentioned this in a earlier post.
All the best
Bob
Foolin Around
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 02:59pm 30 Jun 2010
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Hi Gordon
This is the spec of the SMPS I am testing with. the 27 volt unit.
All the best
Bob
Foolin Around
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 10:52pm 30 Jun 2010
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Bob,
I'm not sure I would agree entirely with Gordon with this bit [quote]I would rewire the F&P, as there are no grounds for higher efficiency with the same load, barring deficiencies with transmission wiring for low voltages. [/quote]
The AWP is a classic example of the output achieved with ferrite magnets and multipole iron stators. The 24 or 48v wind version is only good for about 1kw, the 240 volt wind is in the 1.8kw range.... same everything except the turns and wire thickness (windings)
The amper/turns is the key here, and at higher voltages, we get that down to a reasonable figure, and our armature reactance is pushed back.... significantly.
I would stick to the higher voltages, but use transformers rather than the pwm solution. The transformers will load vary with your mill, the pwm will do so, but only in a limited fashion..... and the transformers will be less inclined to fail in adverse circumstances.
I don't think you will be loading the mill properly with the PWM solution, but then again I simply don't know enough about your particular mill build..... but a 10 foot hawt may well send the pwm into orbit.
If you can size your pwm load to absorb all the stator current... up until current limiting where the armature reactance stops further power generation, then your pwm's should survive.... unless you lose the load for any reason..... then all bets are off.
..............oztulesVillage idiot...or... just another hack out of his depth
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 11:14pm 30 Jun 2010
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The fig of a 100m cable run negates a low voltage power transmission.
In the application given, the wire in each case would be the same, only used in a different series/par combo.
load matching will always be the key.
I await some test data for further comment.
Gordon.
become more energy aware
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 01:22am 01 Jul 2010
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HI OZ
I read your post on AWT and it sounds like a good design if the engineering was sorted out to make it more reliable, as with most Chinese mills ALSO the engineering design is good but the workmanship lets it down.
I have 12 here to rebuild at the moment.
On the use of transformers to do the job I agree that's the best way to go as simple is best but would need to have special transformer made as the conventional transformers seemed to get lossie as the speed came up and the core heated up indicating power lost in the eddy current loop, that was with a 1000 watt 250 to 33 volt transformer x 3. I have purchased 3 600 watt ferrite toroidal transformers to try as they should have a lower loss, haven't tried them yet as other things have taken priority. I was hoping to get off the shelf power supplies to avoid the work of doing the both things as the mill is a major contract on its own.
The only reason I am going to VAWM is the low wind speed on my property as I get an easterly sea breeze most days from 3 to 7 ms and higher winds suitable for HAWT for 4 months apart from storms. I was very interested in your comments on the low speed performance of the AWT for that reason. It started me thinking on a F&P that's overpropped and fitted with neo magnets, but that's another story.
I have a MPP device I have been working on for the last 6 months, but not going to well due to lack of nouse by me, so decided to do the test with the mentioned SMPS as buying three of those would be easier for me. My electronics where Valve and high voltage so I,m like a mullet on the beach with these little IC things and resistors I need a magnifying glass to read the bands.
I have purchased a roll of 3 core 6mm power lead to go to the shed so am more or less committed to the high voltage track at this time.
All the best
BobFoolin Around
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 01:37am 01 Jul 2010
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Hi Gordon
You can see the problem I have with the distance and OZ has suggested transformers so my reply to OZ explains what I have tried.
With the VA design it is based on our work of years ago but with different blade design so as I said its all theory at the moment apart from lash up using gyro blades to see if it worked.
I look forward to getting a multi channel logger going when you and Pete get it sorted out as the mill is 100 meters from the shed it will need radio link to work.
My test data at the moment is still pencil and paper with a weather station on the roof of the shed which is shielded from the easterly wind so not a true indication of wind for the VAWM.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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