heating water with wind

[captainkirk2]

I have read many of the threads regarding this topic and have not been able to find some answers to my questions.  I live in Livingston, MT - a very windy place - where in winter months winds are often 20-30mph for several days - today is a 30-40mph day with gusts up to 50mph.  I have a solar water heater system in place which does great during the warmer months but we get very little sun in winter.  I have been doing research regarding using a wind genny to heat our water.  Here are some quick numbers:

Wind genny rated 700watts (Gryphon 700, http://www.npp.ca/nppwind/gryphon.htm) generates 400watts at 20 mph (derated for our altitude here) would produce 9.6kw over a 24hr period (yes, the wind really does blow all the time - have anemometer data to support).  That amount of energy should be able to heat 50 gallons of water about 80 F (from 50F to 130F).  First question:  Does it seem like my calculations are accurate?  Second question:  I know there are low voltage heating elements out there that I could use to replace one of the elements in one of my water tanks, but how can I shut off the element if the water gets to about 140F?  I cannot seem to find a dc thermostat.  Third question:  Has anyone had any experience with the Gryphon turbines?  They are one of the few out there that seem to operate up to 50mph and could survive our often 70mph gusts.

I have other questions that perhaps someone could help me with but these three could get discussion started.

[captainkirk2]

Just had a thought: Could I use the thermostat that is already on the water tank that is not powered (used as a storage tank for solar water system) as a shut off thermostat switch for the wind powered heating element?  Or would it not be able to handle the DC current?

[kurt]

first off you seem to be confusing kilowatt(KW) and kilowatt hour(KWH) you are saying one but it looks like you mean the other mite wanna wrap your head around that first and recheck your math (i did not bother)

[wpowokal]

I make 0.4Kw for 24 hours equal 9.6Kw.

The thermostat could be used to switch a DC rated relay/contactor/MOSFET,  this would not load the thermostat contacts. And don't forget an alternate load for the mill.

allan down under

[scorman]

You seem to be selling yourself short!

Why are you considering ONLY heating domestic hot water??

Many including DaveB's 18footer are using resistive heating elements to heat both domestic water as well as heating the house with baseboard radiators (circ pump only runs 20 watts!).

With wind like yours, why are you playing with toys??

Don't have baseboard heat ...use a fan with a nichrome heating element

I have seen a Lakota in action and I was very impressed ...that is a 900W machine:

http://www.truenorthpower.com/index.php?option=com_content&task=view&id=3&Itemid=4

 and I've seen several Whisper 200s in action and they are rated at 1KW @26mph:

http://windenergy.com/documents/spec_sheets/0040_whisper_100-200_spec.pdf

above are still small for my liking, but then cost becomes prohibitive

(this presumes you don't have the wherewithall to build your own 15 or 18 footer)

the biggest complaint on this board is lacking in wind ...not having too much all the time

Stew Corman

[captainkirk2]

Thanks for the comments guys.  I am very impressed with the rapid response. I have only been reading items on this board for a few weeks but have been impressed with the knowledge and experience base.

Now to reply:

Stew,  I will look into the Lakota as well, they look like they could handle our winds here as well and they are slightly smaller and better(?) looking.  As to the reason for the proposed set up - it is mostly economics and a bit aesthetics.  Aesthetic-wise, we live on 20 acres in a "subdivision" so I have been trying to keep noise and "ugliness" to a minimum.  Economics:  Grid-tie not an option even with a larger turbine because of how our electric company does their net metering and the amount of electricity we use (about 500-700 Kwh/month  - about half of that is for heating water without the solar assist which we get maybe once a week in the winter at a rate of $0.075/Kwh).  Because of the use, rate, and lack of winds in the summer it will not pay to put a lot of money into battery pack, inverter, and a wiring scheme that would give us reliable electricity in the rest of the house year round.  Lastly, although we do have electric baseboard heat we have never used it (they are shut off) in the two winters we have been here - we use a wood stove and use mostly scrap/tossed out/cut down wood that would be going to a landfill.  All of these factors lead to my assessment of a "unique" situation.  Considering all these factors is why I am looking into the set-up I described - Heat water with wind/solar combo year round and cut our yearly electric use/bill in half in the least expensive way - we get several visitors in the summer using hot water and we plan in putting in some radiant floor heat in the future.  I see it as the most-bang-for-my-buck near term and a win-win situation for our long term future plans for the house.

Kurt, Thanks for watching out for me, I redid and rechecked my calculations and I still get around 10Kw to heat 50 gallons about 80 degrees F, it doesn't matter whether it is over an hour (10Kwh) or over 24 hours (0.417Kwh * 24h = 10Kwh).  I know this doesn't take into account heat loss from tank and inefficiencies of energy transfer, but I don't want to make these guestimate calculations too difficult.  Here is a site that confirms my calculations: http://www.tempco.com/Engineering/wattage_estimation_tables.htm

Allan down under, could you please explain in more detail what you suggested or send me to a site that would show a diagram. It would help me greatly, and if it could work, this set up would come together.

Thanks again guys for your comments.  Obviously, this idea is just in the planning stages right now, but I want it well thought out before proceeding.  Peer review is very powerful.  I am very passionate about alternative/renewable energy but also about the economics of it.  If I can get this to be successful on both accounts, others in this area would jump on board.  

[ghurd]

The circut is simple... IF you have a battery.

Without a battery, things get very complicated, very fast.

Not sure why you want to stop heating water at 140'F.  Nice way to reduce power costs, but it's not costing extra to heat it to 165'F (or whatever).

Might consider an extra low voltage heater?  If the 1st tank gets to the desired temperature, the load can go to the tank before the first tank.

The Gryphon has some kind of controller that may confuse the situation.

Someone had some issues with a controller that looked just like the photo, IIRC.

G-

[scorman]

now that we have a few more details, we can discuss several points in particular.

"Economics:  Grid-tie not an option even with a larger turbine because of how our electric company does their net metering and the amount of electricity we use (about 500-700 Kwh/month  - about half of that is for heating water without the solar assist which we get maybe once a week in the winter at a rate of $0.075/Kwh)"

I don't understand your math economics ...we have 82 gal electric hot water heater and at $0.14/KW, I figure my actual useage is about $12/mo (four people) ...my total house electric useage is about 900KW/mo and we have energy hogs ...your cost rate is 1/2 mine, and you think you use 300Kwh just to heat domestic hot water which is then 4x my costs??

Fine, so lets use your numbers ...300Kwh at $0.075 = $22/mo ...then you can't be serious in spending $3K for a turbine (not including the tower costs, wire, etc) to get an ROI for this project. Just pay the electric bill if that's all you can do with it!

"because of the use, rate, and lack of winds in the summer it will not pay to put a lot of money into battery pack, inverter, and a wiring scheme that would give us reliable electricity in the rest of the house year round"

Total agreement ..the battery/inverter mode wastes >30% of the available energy produced and the hardware costs are absurd, whereby "wild" AC into a resistance heating element is 100% efficient.

" Lastly, although we do have electric baseboard heat we have never used it (they are shut off) in the two winters we have been here "

hmmm ...sounds like a great dump load to me??

This sounds like the best implementation you have ...the hardware is already installed and all you have to do is untied it from the grid and connect directly to turbine output ..use relays to connect/disconnect individual elements to vary the load ...look for a turbine option with as high a voltage output as possible ie >115v since you are NOT charging batteries

A 12 footer with your wind should produce 2KW easily (that's 4x+ what you are talking about buying) ...why not build your own ( and I am not a fan of building your own generator ...buy one) after procuring the blades for a few hundred $  from Dave B's buddy ( or 13 ft Chinese fiberglass off eBay):

http://royalfabrication.com/index.htm

By the time you work out the investment costs ...go for something real rather than a toy.

Stew Corman from sunny Endicott

[captainkirk2]

G, Picked 140'F as a safety factor.  Higher is fine by me but I wouldn't want to go much higher than 150-155'F partly for safety mostly because this house house CPVC water pipes, and I don't want to risk blowing a pipe and don't want to replace them all right now.  I thought of the two low-voltage element set up as well (for a total of 100 gallons of water to potentially accept all the energy) but again, I am stuck on exactly how to wire it all up so that, ideally, the following would happen: Energy from wind genny heating water in main tank until temperature limit is hit then switch to heating water in preliminary tank until temperature limit is hit then energy goes to a dump load if necessary (which could potentially happen on a windy, sunny summer day).  

I do plan on having a small battery bank in place so that the load diversion controller can do its job, i.e. I was thinking of having a load diversion controller dumping the load to the heating element almost all the time since a small battery pack would be fully charged nearly all the time.  I could see where I could connect a second element (say in the main tank) to the battery pack.  That way wind genny could send power to main tank first then when that "tops" off the controller could divert the load to the preliminary/solar storage tank.  BUT AGAIN, how to get the heating elements to shut off once the water is up to max. temp.?  There should be a way to use the thermostat switches that are already on the tanks.  It would be easy if I could just include them in the heating element circuit but I do not know if they would work properly with low-voltage DC.  

Also, as a back up safety, I would want to have a way to dump the load or shut the whole thing down automatically in the very rare case that all 100 gallons was heated to max. temp. which could potentially happen on a windy, warm, summer, sunny day.

More help would be much appreciated.  I feel like I am so very close to figuring this out that I can taste it.  Even if I figure it out, crunch all the economic numbers and find that it's not worth doing at this point, at least I would get the satisfaction of having "solved the problem".  Please, if anyone can be specific with the wiring and switching of this type of set up, I would greatly appreciate your input.

Kirk

[captainkirk2]

Stew,

Math economics: we seem to have a discrepancy in estimates of hot water use and cost.  1)I know from my calculations (and supported by other sources) that it takes about 10Kw to heat 50 gallons of water 80'F (from 50'F to 130'F).  Do we agree on that or not?

2. I also know that we got through a minimum of 20-30 gallons of hot water/day.  What can I say, we like hot showers not lukewarm, and if you average in laundry (unfortunately still a top loader but always run full), dishwasher (always run full), and various other misc. use its probably around 30-40 gallons/day (still less than the american average).  I also know from data gathering this past summer when assessing the solar hot water heater that we would go through at least 50 gallons/day if both of us would take showers, one load of laundry (wife insists on using warm water - don't mess with a woman and her laundry), and a load of dishes.  Obviously, this did not happen every day but we also don't have sun all day everyday.
   
3. You estimate that you are spending $12/month at $0.14/Kwh for hot water.  If you agree with #1 above than that works out to 3.6 gallons of hot water/person/day.  Even if mixed 50/50 with cold water that still only amounts to a 3 minute shower with a 2.5gpm shower head, and that leaves not hot water for dishes, laundry, etc.  Am I completely missing something there in my math?
   
   

Electric baseboard heat: could do, thought about it, but decided against it because 1) we don't really need to heat the house.  We don't fire up the wood stove everyday let alone all day everyday.  In fact, today we had it fired up for about 4 hours in the morning and it is still 66'F in the house this afternoon. 2) we definitely do not need to heat the house in the warmer months so that arrangement would be useless for at least 5 months every year - we always use hot water.  3) I would still need to do a bunch of wiring and relay switching - i.e. same amount of work there for something that only provides us with something we don't want half the year and don't really need the other half.

Build my own: Almost went that route but decided I'd better not get into another project inside a project -- I already have too many projects to do (don't we all?).  However, I have started researching the Lakota brand wind turbines and they look promising - about double the output of the Gryphons with about the same size and only slightly more expensive.

Whew! I digress.  I would appreciate you thoughts on these statements.  As I said earlier, I need this idea to survive the crucible of peer review in order for me to feel confident moving forward.

Kirk

[ghurd]

Isn't 140'F the hash-mark on the thermostat?

Nobody showed you a circuit before because you didn't give enough about the system.

Battery / No Battery are VERY different animals.

With a battery, 2 tanks, and a dump load...

(I am trying not to sound like a product commercial, but this is what I know a lot about)

I would use 3 of my controller circuits.  A circuit link follows, but read this first.

The 1st one set as an LVD, but with a higher voltage and less hysteresis, feeding the first tank.

The second one just the same, but the voltage and hysteresis a bit higher.

The 3rd one feeding a dump load large enough to handle everything the windmill can make, and a bit more.

Tha factory thermostat contacts are in between the "output to power fet gates" and the gates.

If the battery is high enough to suit controller #1, it sends a signal to thermostat #1.  If the water is cold the thermostat is closed so the power control device (power fet) turns on the heating element. Tank #1 heats water.

When the battery is a bit higher, and high enough to suit controller #2, it sends a signal to thermostat #2.  If the water is cold the thermostat is closed so the power control device turns on the heating element. Tank #2 heats water.

If the battery is in danger of overcharging, controller #3 sends power to a dump load.

Depends on the loads, but the power fets may require minor changing of the circuit.

Or the power fets might be better replaced with IGBTs.

Your math, going from 50'F to 130'F in a day, without any losses... Might not be worth the second (or is it the 3rd?) tank and the related costs?

If it is windy, then it is winter (you said it).  Heat is good in winter.

The flip side... In summer, not much wind and don't need the heat. But the 2nd (3rd?) tank would act as a tempering tank to get the water to room temp without any electricity cost.

http://www.fieldlines.com/story/2007/8/24/172521/889

Forget about relays.  

High tech transportation in Florida...

Was a horse, 400 years ago.

Was the Space Shuttle, 25 years ago.

Relays are closer to the middle than most people think.

Windmill "Wild AC" to a heating load is an expensive complex nightmare, best I can tell.

Are you confused more or glad you asked?

G-

[spinningmagnets]

Hi Captainkirk2, I'm a newbie, so feel free to point and laugh (swallow the milk before you read further)

There's a lot of great ideas over at "builditsolar.com". Just reading all of them is an engineering education by observing the different ways that several people tackle a common problem, and one of most cost-effective projects is digging an underground insulated water store. It was originally for a home that had lots of sun during the cold months. A small solar-PV panel powered a DC pump that flowed water over solar heat collection panels that drain to the underground water store.

Then, this large pool of warm water can be used to heat a radiant floor system or baseboard air heaters. In your case, perhaps a thermal sensing valve can divert the wind-heating load to a water pool when the Domestic Hot Water (DHW) tank reaches 140F?

With a one-day rental of a backhoe, you could dig a pool large enough that the wind "dump load" would never be able to overheat it...just an idea to ponder...

[captainkirk2]

G, More confused and glad I asked.  I completely understand conceptually what you are describing but a bit confused as to some of the specifics of the connections - of all the construction trades electrical is my weakest.  

I already have two tanks and ideally I would replace the lower one in each.  What are "power fet gates"?  Do I understand correctly that they are like a relay that directs where the main power goes?  If so, what kind where could I find ones that would be suitable for dealing with up to 800-1000watts of DC power?

I have had a few people tell me that the thermostats on the tanks won't work with/can't handle the DC.  What is your opinion?  How much DC power would be going through the thermostat from the "output to power fet gates"?

[ghurd]

Think of the power fet gates as the relay coil.

A minute signal to the power fet gate would be like the relay coil.

IGBTs would handle a huge DC load. 150A if that is what you want.  They could replace the relay.

The thermostats will handle DC, just not much in the line of a DC load.

My concept uses the thermostats at a very small current, to control a far larger load.  Just like the relay concept.

""I have had a few people tell me that the thermostats on the tanks won't work with/can't handle the DC.""

Depends.  They can't take 100KW of 12V.  They can light an LED.

""How much DC power would be going through the thermostat from the "output to power fet gates"?""

Depends on how the controller is built, but 1/100,000th of a watt is enough for mosfets.

As discribed, the circuit feeds about 1Wmax to the circuit that supplies the power fet.

[scorman]

Kirk,

I'll have to back over my calcs for our domestic hot water consumption.

BTW, here is a good calculator (only runs on IE):

http://www.rheemtankless.com/content/documents/Fuel%20Cost%20Calculator.htm

if I plug in 25gal/day and $0.14/KWh it comes up with $0.70/day = $21/mo

your 40gal at $0.075 comes out to $0.62/day = $18.60/mo ..not that far from the $22.50 I speculated ..so yes, I agree with your numbers

I too am in a quandry of what to use wind power energy during the summer months other than heating domestic water ?? Any good ideas welcome

I would really like to have airconditioning from a unit similar to the "3-way" frig on a travel trailer ...no compressor, just a heat tube ...however, without batteries, it would only work when the wind is blowing and then you could just open the windows since wind occurs when it is generally cooler out.

...for winter consumption, my presumption was that you use all you need for domestic first, then divert to heating the house second. Why have a dump load heat the atmosphere?? Simplest hookup is just one baseboard element.

I too am burning wood as a renewable energy excluding fossil fuel (oil furnace is turned off), and yes, recently we just went three days w/o any fire with some passive solar.

That said, in the fall and spring, it is a pain to heat up an entire 2750sqft straight ranch by starting the fire ...the oil furnace would typically kick on for only 20 min at a time, so it would be nice to take the chill out as the wind blows. I'd worry about opening the windows if house gets too warm ....yeah right! I figure I could save 1 full cord of wood/yr

Mid winter would be nice to reduce wood consumption and/or supplement when temps go below zero F.

OT -- I just ordered a Kill-A-Watt meter for $20, to check out my old frig, freezer, PC's etc. Too bad can't use on hot water heater because it is 220v and draws too much (but thinking of using a shunt?? Any comments?)

Curious where the electric is going

BTW, check out the new offering from Lakota on their site when  info is available.

Their Longbow model is a bit bigger than the standard, but the new one is 1Kw at 18mph ..that could be the cat's meow

Regards,

Stew

[captainkirk2]

Stew, sorry I don't have any other suggestions for you.  I looked up info on the Lakota model you mentioned.  Best I can tell, you must be referring to the OB1KW model which is not available right now.  Could be a decent one based on specs but I'll believe it when I see it especially since they have been testing it since 2000-2001.

[captainkirk2]

Now that's an idea!

[captainkirk2]

I just want to say thanks to everyone for all their input.   I am sad to say that I fell that this project is no longer worth pursuing at this time.  The costs to make it work in a safe reliable way . . . the economics just don't work well a this time.  Unless someone knows of a source for a low RPM generator that puts out a relatively stable 12 or 24 volt DC no matter what the RPM.  Then I could possibly cobble something together that could help me out.

[ghurd]

I know.  

Use a generator that suits your wind needs.  Feed it into a small (smaller than normal) 12V or 24V battery.

Connect a dump load controller, or an LVD, to the battery.

The dump load is the water heater.

Simple, but it gets around most of the complicated and expensive problems.

The voltage is within a certain window.  Always.

The windmill won't be stalled as in a direct connected system, or need the caps of non-stalled direct connected system.

If the windmill is making 100ma at 12V (1.2W), it is charging the battery until enough power is stored to run the heater full power for a short time.

The more power the windmill makes, the longer the heater runs.

More wind = more hot water.

That's what you are looking for when heating water with wind, right?

With luck and scrounging, probably do something Very respectable for under $1,000, complete.

G-

[ohiowinds]

You can use the tanks thermal switches to control a DC contactor, 120/240VAC wired in series with the switch and the contactor coil.  The contactor coil does consume a little power, about 1 o 2 watts.  The contactor contacts should be DC rated for the current you anticipate through the heating elements.  Some time an AC motor contactor will work for DC and can be found surplus or used/removed from industrial equipment.

The reason most AC contacts are rated much lower for DC is that the alternating break when the contacts open aids keeping the contacts from pitting, where DC always breaks with the current in the same direction leading to uneven pitting and build-up , much like arc welding builds material to form the weld.

[jonas302]

also would be a good idea to check with the utility about off peak programs here (in central mn) water heat is .035 cents kwh it works real well if you have more than one tank and even  tempering tank ahead of the heaters