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Pete Smyth
24th February 2008, 20:25
Currently a Vawt I am prototyping is producing high torque at 6-12 km winds.
This is using large sails and only turning at 6-12 rpm.
I am finding it painful to step up the gearing to 800rpm to drive car alternator(s) using pulleys and fan belts - and after 8 months of looking at PM generators - I have finally given up on using generators to produce power directly as there quite simply is no solution that seems cost effective and power efficient in the long run - especially when having to gear up from this low rpm- and wanting to link multiple vawts.

An alternative may well be heating water. Two recent developments are making this look attractive. The Tadpole - that increases water heating efficiency by 30 percent by removing Hydrogen and sulfated Hydrogen, dissolved air and other impurities (http://www.tagonatadpole.com/the-tadpole.html)
Secondly an even more recent development - a cheap solar collector that is up to 50 percent more efficient that conventional units - If adapted to water heating this would be incredibly cheap to build. (http://www.motherearthnews.com/Renewable-Energy/1976-05-01/The-Hot-Line-Solar-Collector.aspx)

The fly in the ointment is that a simple method is needed for VAWT systems to heat water directly so they can link in this these new developments.
Three possible systems come to mind.
1 Eggbeater system - Thump the water mercelessly to create heat using friction generated by eggbeaters or paddles etc - This seems to lose efficiency as water temperatures increase.
2. Cavitation system - as shown by utube- But this again requires very high rpm to operate. YouTube - FUELLESS HEATER NO FUEL NO GAS NO WOOD NO GREEN HOUSE GASES
3. Eddy Current Heating - using neo magnets to heat up aluminium or copper - these have the advantage of lower rpm and heat water very efficiently- even at the higher temperatures- and suit the high torque provided by VAWTs.
However no clear links to work from - much experimentation needed.

In short Linking multiple vawts to a Solar heating system and utilising the hot water for home heating would be interesting.
An even more interesting concept would be to store this water highly insulated at just under boiling point- and use a small amount of power from the grid to create steam from this near boiling water to drive a steam powered turbine generator at peak demand times. This will supply power back to the grid at significant profit - and perhaps help save the planet in the process.

Using wind to heat water by generating electricity is not very efficient (less that 25 percent) but by Friction/and or eddy current heating IMHO greater than 50 percent efficiencies should be achievable.

Anyone have similar thoughts?
Happy VAWTing!
Peter

Joe Blake
25th February 2008, 00:41
Hi Peter,

Welcome to the board.

I've absolutely no experience in wind turbining, but for heating up from a rotational source, have you considered looking at a bicycle trainer with a magnetic drag brake? (Might be cheaper and quicker than trying to build one from scratch for your eddy current.)

http://www.moruyabicycles.com.au/index.html?lang=en-uk&target=d27.html&lmd=39470.628981

Before I replaced mine with a 12 volt generator (see my thread on it

http://www.greenpowertalk.org/showthread.php?t=4070 )

I would ride my trainer, and measure my work by fixing a thermometer to the outer casing of the magnetic brake. It was not unheard of for the temperature to reach 55-60 degrees C. I never managed to measure the internal temperature though. On some occasions it got so hot that the magnets were somehow temporarily demagnetised, and I'd lose my drag.

Just a lateral thought.

Joe

Pete Smyth
25th February 2008, 18:36
Hi Joe,
Are you one of the MIT cyclists on the pic? - amazing stuff.

I hadn't thought of bike training eddy current brakes- definitely worth a look.
Although to suit high torque and low revs - an adjustable air gap would be needed and MUCH larger neos - I am hopeful that I will heat a bucket (10 liters) to boiling in around 15 mins at 12kph winds - that would equate to (using my kettle as a guide = 2300W at 240v takes around 1.5min a liter.) .
Of course this is assuming that I will have at least twice the efficiency of the electrical heating element using eddy currents.
I am purchasing various neos to experiment with.
A stator disk arrangement was used successfully by Windstuff Ed on the otherpower discussion board - he quoted 4-5 mins to heat a bucket of water using a hi speed lathe. I am guessing that much higher strength neos acting on multiple layered thick copper or aluminium disks would work at speeds compatable with a VAWT and one trick will be a fine airgap adjustment to fully utilize the hi torque of the VAWTs. One issue is keeping the temp of the neos down below 170 c. or they will lose magnetism.
Any tips or suggestions on maximising eddy currents through metal would be appreciated.
A quick thought Joe, The beauty of a hot water storage system would mean that your cycling would contribute twice (or more) the power than a bike generator would provide- especially if providing heat for your home.
Cheers
Pete




Hi Peter,

Welcome to the board.

I've absolutely no experience in wind turbining, but for heating up from a rotational source, have you considered looking at a bicycle trainer with a magnetic drag brake? (Might be cheaper and quicker than trying to build one from scratch for your eddy current.)

http://www.moruyabicycles.com.au/ind...d=39470.628981

Before I replaced mine with a 12 volt generator (see my thread on it

http://www.greenpowertalk.org/showthread.php?t=4070 )

I would ride my trainer, and measure my work by fixing a thermometer to the outer casing of the magnetic brake. It was not unheard of for the temperature to reach 55-60 degrees C. I never managed to measure the internal temperature though. On some occasions it got so hot that the magnets were somehow temporarily demagnetised, and I'd lose my drag.

Just a lateral thought.

Joe
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Joe Blake
25th February 2008, 19:00
Hi Joe,
Are you one of the MIT cyclists on the pic? - amazing stuff.

...
A quick thought Joe, The beauty of a hot water storage system would mean that your cycling would contribute twice (or more) the power than a bike generator would provide- especially if providing heat for your home.


No, I saw an article on the Gizmag website

http://www.gizmag.com/mit-cycling-human-powered-computation/8503/


and followed from there.

As for heating my home, I live in Perth, Western Australia, and at present we are bracing ourselves for another heatwave (the meteorology people have predicted 4 consecutive days with temperature at or above 37 degrees C). However, I'm mentally constructing a small system using some PVC pipe, a small fan and a solid-state cooler (Peltier) to try and keep my work station at a reasonable temp.

My water heating needs are taken care of by the sun - even in winter - well, partly, anyway.

Joe

Pete Smyth
27th February 2008, 17:51
Might be simpler to drive a big fan- but I'm not a big fan of big fans
:) Cheers
Pete



No, I saw an article on the Gizmag website

http://www.gizmag.com/mit-cycling-human-powered-computation/8503/


and followed from there.

As for heating my home, I live in Perth, Western Australia, and at present we are bracing ourselves for another heatwave (the meteorology people have predicted 4 consecutive days with temperature at or above 37 degrees C). However, I'm mentally constructing a small system using some PVC pipe, a small fan and a solid-state cooler (Peltier) to try and keep my work station at a reasonable temp.

My water heating needs are taken care of by the sun - even in winter - well, partly, anyway.

Joe

Joe Blake
27th February 2008, 21:50
Might be simpler to drive a big fan- but I'm not a big fan of big fans
:) Cheers
Pete


Yup, they just move warm air from one place to another. But I've got PVC pipe lying around, I've got an old Peltier-cooled fridge doing nothing, and on hot days I've got a (slight) excess of 12 volt power. So why not combine them all?

Of course, mentally constructing is one thing ... actually building it is another thing altogether.

;)

Joe

Mark Parsons
28th February 2008, 15:47
Hi Joe,
I am hopeful that I will heat a bucket (10 liters) to boiling in around 15 mins at 12kph winds - that would equate to (using my kettle as a guide = 2300W at 240v takes around 1.5min a liter.) .
Of course this is assuming that I will have at least twice the efficiency of the electrical heating element using eddy currents.
I am purchasing various neos to experiment with.
A stator disk arrangement was used successfully by Windstuff Ed on the otherpower discussion board - he quoted 4-5 mins to heat a bucket of water using a hi speed lathe. I am guessing that much higher strength neos acting on multiple layered thick copper or aluminium disks would work at speeds compatable with a VAWT and one trick will be a fine airgap adjustment to fully utilize the hi torque of the VAWTs. One issue is keeping the temp of the neos down below 170 c. or they will lose magnetism.
Any tips or suggestions on maximising eddy currents through metal would be appreciated.


Greetings Pete,

Heating water formulas from memory. 1 btu is defined as - power required to raise 1 pound of water 1 degree F. 1Watt = 3.314btu/h. 10 litres of water = 22 pounds. To raise temp from 70 to 210 degrees F = delta T of 140 F * 22 pounds = 3,080 btu. To do this in 1/4 hour = 12,320 btu/h = 3,717 W = about 5 HP.

A good sized VAWT is required to produce this amount of power.

Your assumption of 2X efficiency over a heating element may be liberal. A good PMA should be better than 85% efficient at converting mechanical power to electrical. The heating element fully submerged is 100% efficient.

The eddy current flux transfer to heating energy is also a function of flux changes per second - i.e. - RPM. You would likely need a gear box to step up the VAWT RPM for reasonable eddy current functioning.

Friction may be the better choice to get low RPM maximum heating capability. Of course, then you've got to come up with a method to replace the wear media often.

Why are you pursuing a VAWT for water heating instead of using solar?

Best regards,
Mark

Pete Smyth
22nd March 2008, 23:22
Greetings Pete,

Heating water formulas from memory. 1 btu is defined as - power required to raise 1 pound of water 1 degree F. 1Watt = 3.314btu/h. 10 litres of water = 22 pounds. To raise temp from 70 to 210 degrees F = delta T of 140 F * 22 pounds = 3,080 btu. To do this in 1/4 hour = 12,320 btu/h = 3,717 W = about 5 HP.

A good sized VAWT is required to produce this amount of power.

Your assumption of 2X efficiency over a heating element may be liberal. A good PMA should be better than 85% efficient at converting mechanical power to electrical. The heating element fully submerged is 100% efficient.

The eddy current flux transfer to heating energy is also a function of flux changes per second - i.e. - RPM. You would likely need a gear box to step up the VAWT RPM for reasonable eddy current functioning.

Friction may be the better choice to get low RPM maximum heating capability. Of course, then you've got to come up with a method to replace the wear media often.

Why are you pursuing a VAWT for water heating instead of using solar?

Best regards,
Mark

Hi Mark,
Thanks for your math - I believe your calculations to be spot on!
My calculations on using the heating element also included creating the electricity to heat the element, - at low rpms this is more wasteful of energy than I would like, hence a one step process to generate heat is
the goal.

I am experimenting with both friction and eddy current heating methods - and I am starting to lean towards friction, despite having to replace some type of friction pads 1-3 monthly (estimate only at this point).

Again I agree with you - Solar is the way to go - but if wind heats water - then it can integrate 100% with a solar system - at very little cost.
Solar does not work at night - and performs poorly in cloudy conditions - however wind energy can quite often supply good energy under these conditions - so this combination - topped of with hydro if available is a threesome made in heaven.

As always ... have fun - but especially when the wind blows!
Pete