Air-X wind turbine to preheat water

Started by hnash53, January 03, 2009, 11:29:32 AM

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hnash53

I have two Air-X 400 watt wind turbines.  I am thinking about dedicating one of them to either

1) preheat water in a combo propane/electric 10 gallon RV water heater, or

2) prevent freezing in my large under-the-cabin water storage tank which will be insulated.

Has anyone here done such a thing, or heard of someone doing this?

The wind blows here a lot in Wyoming.  And the sun shines a lot so that when the wind doesn't blow, my 300 watts of solar panels can divert excess electricity into the water heater/tank when the wind isn't blowing.

Which then begs this question:  Can I wire both a wind turbine and solar panel into the 12V heating element in a water heater/tank?

Thanks for your answers.

Hal

glenn kangiser

Solar is a very expensive way of heating water and is usually only used on a dump load when you have excess.  A water heater if not cycled will drain batteries dead so controls are in order.

A dedicated wind generator could be fine, but you need another way to take care of the power after the water is hot - perhaps a second dump load set at a higher voltage because the wind generator cannot be uncoupled from the load even if the water is hot - it will fly apart.   Depending on the draw Tristar or Trace controller will work per last link.

I would use a regulator with a diversion circuit as a controller. This little A/C one is 1400 to 1500 watts depending on the model.  http://www.erieshore.net/~lazybone/docs/WTRHTR04.pdf

12/24/48v
http://www.survivalunlimited.com/windpower/diversionloads/HeterElementWattChart.jpg

http://www.survivalunlimited.com/diversionloads.htm

Looks like it is done and recommended in excess power areas with wind generators.
"Always work from the general to the specific." J. Raabe

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hnash53

Glenn, thanks for the reply.  I was not thinking of actually heating the water to "hot" with the wind turbine or solar power, just warming it up so that less propane would be used to take it up to "hot".  Or, in the case of a water storage tank, keeping it from freezing.

I have seen where there are 12V water heating elements that can be installed in place of AC elements.  I was thinking of putting something like a 400-800 watt 12V heating element in a water heater like the Atwood in the link you sent. That way, the water would be warmed partially by either/or/both the dedicated wind turbine and excess dump power from the solar panels.

Is it possible to connect the wind turbine directly to the 12V heating element, and then also connect a dump load wire from a solar power regulator to the 12V heating element, too?

Water heating is a (the?) major source of energy consumption, along with space heating.  I just thought this would significantly reduce propane burning since the only other propane uses would be a propane fridge and an occasional use of a propane heater.

I'll have about 300 watts of solar and the other Air-X 400watt turbine to keep the batteries charged.

glenn kangiser

Just put everything to your batteries including both wind generators, then use the regulator as a dump load diverter, then all things will keep the batteries fully charged and all excess power will be diverted to the water heater from whatever is producing it.  Monitor things to be sure your regulator is large enough to cover all diversion loads or regulate your panels separately to get more control against overcharging.

I was just thinking that if you get too much power and the water heater is getting overheated, then increase the size of the water heater so it can take the extra heat.  I don't think that will happen but the wind generators cannot be removed from charging the batteries - they cannot be run unloaded even if overcharging or likely blades will fly eventually.

Buy one of the heaters with two elements so if necessary you can use both in parallel to divert twice the power into the water if 12v or series if 24 volts.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

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Native_NM

I read an article on the methods of preheating water.  The best option was an old water heater painted black, laid horizontally in a hot frame.  They used the glass from an old sliding door I think.  In any event, when oriented properly to the south, it raised the temp substantially.  In New Mexico, it can serve as a water heater during the summer months, and a preheater all year.  Depending on your location, it can still save you substantial $$$ year round.  Best of all, they can be built for almost nothing.  It used gravity and thermal siphoning, was plumbed with recycled parts and cheap black poly.

One thing I do remember is that the energy requirements and cost to heat each additional degree is NOT linear.  The cost increases at an increasing rate as you move up the temperature scale.  To heat the water from 50F to 75F may only use half as much energy as it takes to heat from 75F to 100F, even though its the same 25F increase.  Don't quote me on the numbers, just the theory.  The warmer the water going into the heater, the cheaper it will be to heat it to final temp. 

It might have been in Homepower magazine.  I subscribe to a few journals and read online quite a bit and don't remember exactly which publication.  I'll check the Homepower archive, as I have electronic access.

New Mexico.  Better than regular Mexico.


John_C

QuoteOne thing I do remember is that the energy requirements and cost to heat each additional degree is NOT linear.  The cost increases at an increasing rate as you move up the temperature scale.  To heat the water from 50F to 75F may only use half as much energy as it takes to heat from 75F to 100F, even though its the same 25F increase.

The heat capacity of water is virtually a constant over residential temperature ranges.  The change is so minute it is dealt with as a constant in virtually all undergraduate chemistry & physics.  Substantial energy has to be used to transform water from ice @ 32˚F  to water @ 32˚F   and  also from water @ 212˚F   to  steam @ 212˚F (all @ STP).  But in the range that would flow through your pipes to anything you want coming out of your tap it is functionally a constant. 

That does not diminish the value of being able to heat or partially preheat the water for free.


It costs more to store warmer water.  140˚  hot water cost more to maintain in a water heater than 110˚ water.  Thats because the temperature gradient is greater.  Very hot water loses heat to the ambient air faster than water that isn't quite as hot.  That's why additional insulation on a standard water heater is a good idea and why on demand heater cost less to operate.

glenn kangiser

That's deep, John.  Looks like you know a bit about it.
"Always work from the general to the specific." J. Raabe

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John_C

I remember a "trick" question from a physics exam.

You have a cup of hot coffee ... say 190˚   and a small pitcher of cold coffee creamer.. say 40˚. 
You want your coffee to be as warm/hot as possible when you have finished reading the sports section.

Will your coffee be hotter if you add the creamer immediately or wait until you are ready to drink the coffee?

I remember everyone in the class scratching their heads and trying to come up with formulas.... how much creamer, what is the room temperature, does the fat content in the cream provide any insulation,  ......  The simple answer was that it would be warmer if you add the cream immediately.  The temperature gradient would be smaller and it would more slowly approach room temperature.  The hot coffee and cold creamer would both more quickly approach room temperature.  It was supposed to be a question we quickly answered and moved on.  I/we all felt kinda stupid, an all too common feeling.

Of course today I'd ask the waitress to pop it in the microwave for a bit.  ;D   And yes I read that thread. :)

glenn kangiser

"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

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hnash53

The Air-X turbines have an automatic sensor which when the batteries reach a certain charge shuts down the turbine.

But if I run the turbine thru a charge regulator  with everything else, will the charge regulator tell the turbine to shut down before it switches to a diversion load?

That was why I had thought of running one turbine directly to the 12V  600 watt heating element.  Do you really think a 400 watt turbine could overheat 10 gallons of water through a 600 watt element?

Also, what about the use of copper bus bars?  Anyone use them here?

Thanks.

Hal

JRR

John C,

Of course, if you happen to be a Sheik in the Sahara (@ 120 deg) and want your coffee the hottest after reading the latest camel trek results .... ya better wait to pour that cream!

John_C

Why would an ambient temp of 120˚ change the physics?

I am intrigued by the camel trek.  Sounds like a new movie for William Shatner. 

MountainDon

Quote from: hnash53 on January 04, 2009, 01:49:48 PM
...what about the use of copper bus bars...
I have used solid copper bar stock for battery bank connections in the past. Right now I have a friend I'm helping with setting up his battery bank right now. We're using 1/4 x 3/4 solid copper buss bar stock for some of the connections. He has 4 pairs of 6 volt batteries in parallel.

With each pair there is a short buss bar connecting one positive to the other battery's negative. Cables are then used to connect each pair of batteries to a positive buss bar and a negative buss bar that run lengthwise down the pairs.


As for whether or not the AirX 400 watt wind gen could be safely used to warm the 600 watt heater in the 10 gallon water heater you'd have to run the numbers to be sure. Find the amount of energy required to raise that volume or weight of water so many degrees. You decide what is the safe upper limit... boiling? or somewhere less. Run the numbers assuming a zero use for the maximum number of days likely. Leaving for a weeks vacation in warm weather could cause the water to boil. But that's a guess and I think you need something more solid than a guess.
Just because something has been done and has not failed, doesn't mean it is good design.

glenn kangiser

Quote from: hnash53 on January 04, 2009, 01:49:48 PM
The Air-X turbines have an automatic sensor which when the batteries reach a certain charge shuts down the turbine.

But if I run the turbine thru a charge regulator  with everything else, will the charge regulator tell the turbine to shut down before it switches to a diversion load?

That was why I had thought of running one turbine directly to the 12V  600 watt heating element.  Do you really think a 400 watt turbine could overheat 10 gallons of water through a 600 watt element?

Also, what about the use of copper bus bars?  Anyone use them here?

Thanks.

Hal

The Turbine will work under it's own control and can hook straight to the batteries or however they want you to do it.  The charge controller would only sense if the batteries were above the level you set it at to dump and if it exceeded that level it would send the excess to the dump load - or water heater if it is the load. 

If the Windchargers have their own regulator built in, then the dump load may not be required and you may have no extra to dump into the heater.  If you set the dump load to dump before the wind generator shut down from over charging but after the batteries were near full charge then everything extra would go to the batteries. 

I don't think anything  is regulated by the controller if it is in diversion mode -- it just senses the batteries state of charge and diverts the excess to the dump load.  That is the way I see it, but I have not researched it so it would pay to check it out.  The xantrex manuals are online I think.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.