Alternative electric heating

[ipec]

I've read an article about wind turbine pioneers here in Quebec that used to dump the produced electricity directly in a heating device or element to help heat their homes. They wouldn't be grid-tied nor would have batteries.

Is this an option?

Even with a smaller wind turbine? would it work?

Thanks

[Chagrin]

Sure it works, just not very well. Even if you're producing 1000W with your wind generator it's little more than a small space heater.

There are much more economical alternatives, notably some form of solar heating.

[doceanboy]

something to make you say Hmmm...

http://www.cansolair.com/wind.html

[Norm]

   Instead of electric heating think about a 12 volt motor to run the furnace blower running slowly quietly constantly for nice steady even heat! ...or even 2 or 3 car heater blowers/and motors ...just think about it this winter when the wind is howling outside...that same wind could be powering those 12 volt motors to circulate the air in your house,  I figure the regular furnace blower of mine must use about a $1 a day of electricity.

            Worth thinking about.

                  ( :>) Norm.

[ghurd]

How about heating a few 55 gallon drums of water in the basement?

Sorry. the Quebec I have seen is all rock, so somewhere else?

Je peche du Quebec pour les pike! Got me. I'm American.  Often thought the Brosard's could do something like this with what is there to use.

[iFred]

 I don't get it... I just don't get it. Can someone explain how this thing produces and transferes the heat or draw a simple picture??

Thanks!

[wooferhound]

Thats interesting how they are mounting the blades on both sides of a truck rear axle.

[thunderhead]

As I understand it the axle that comes down rubs a wooden cylinder against another (glass?) cylinder filled with water.  The friction heats the water which is circulated through radiators in the house.

A well-insulated house here in sunny England needs about 4000kWh to heat it over the winter: that works out at 1.85kWh continuously through the winter period.  That's quite a big windmill.  (I bet in Canada they need more.)

It seems to me that what is really needed for heating is a big water-tank in the basement.  If heating a well-insulated house takes 4000kWh over the three months of winter, and the water tank is 98C at the beginning of winter and 38C at the end of it, the tank needs to contain 57 tons of water.  That sounds like a lot, but if your water-tank is 2m deep it needs to be about 8m x 4m: a good-sized swimming pool, or if you prefer deliberately flooding the basement.  The basement is the right place to put it so the leaked heat keeps the house warm anyway.

In the summer, you use thermal solar panels to provide heat to get it warm in the winter.  Since thermal solar panels are cheap and reliable, this system will be much cheaper than a battery bank.

It also provides hot water all through the year.

If you're determined to use a windmill to generate heat, it seems to me that the best plan is to have electric air conditioning of some sort, and put it into reverse during the winter.  That means that in summer you can keep cool, and in winter the reversed heat pump needs only a few hundred watts to produce that 2kW of heating.

But I'd prefer the big tank of hot water, as hot water strikes me as much more reliable.

[bkrahmer]

> How about heating a few 55 gallon drums of water in the basement?

Just a few comments regarding the heat storage abilities of water.  I'm planning on incorporating wood-fired water heating, and possibly solar water heating, into my house.  I'm planning on using a 300 gallon tank for heat storage.  I've calculated the heat load of my house at about 12k btu per hour on an average january day.  This is a brand new house, and will be insulated very well.

The problem lies in the fact that 300 gallons of water (2500 pounds) can only hold 200k usable BTU (range of 100 to 180 degrees).  That equates to 16 hours of heating for my house.  Not toooo bad, but not as much as I would like.  

Just FYI.  Until I did all the calculations, I assumed that water would hold much more heat than it does.

[nothing to lose]

"Just FYI.  Until I did all the calculations, I assumed that water would hold much more heat than it does."

Well look at the bright side, durring the day the water does not need to hold heat since it is being heated then, so at least it only needs to hold the heat over night when the sun ain't there. Course you lose on those long sunless weeks though.

Years ago when I studied thermal mass a wee bit as I recall water and concrete were the best storage mediums. I forget which was actually the best, but then again one cannot pump concrete to remote areas of the house anyways

[jimovonz]

If you use a medium that changes state in the temp range you need it to work in, you can store a lot more energy. For example it takes 336kJ to raise 1Kg of water from ambient temp (20degC) to boiling point (100degC). It takes a further 2260kJ (almost seven times the energy!) to convert that same water into steam. This is the latent heat of vapourisation. All of this energy needs to be extracted again to convert the steam back to liquid water.

Try paraffin (wax) for your storage medium. You can get a whole range of melting points to suit your needs and maximise your energy storage density. If you choose a melting point that corresponds to the temp of the fluid you wish to circulate in your house, the paraffin will maintain the temperature of that fliud (via a heat exchanger) as energy is extracted because it is changing state (from a liquid to a solid). The same process happend in reverse as energy is put into the system from your heat source and the paraffin converts from a solid to a liquid. A very simple way to acheive this extra heat storage would be to seal a quantity of paraffin in a heavy plastic bag and place it in your 300 gallon tank.

I use a 1500l (500gal approx) tank for my system which allows me to store approx 120kWh using water only (30degC-90degC). This is all I need for my 2800ft^2 home

Here is a link that better explains latent heat:

http://www.physchem.co.za/Heat/Latent.htm

[Dan M]

What about filling the drums with crushed rock then water?

I don't have figures on the specific heat of rock, but I would assume it's a lot higher than water (and it's REALLY CHEAP).

Lead shot might work well if you have a cheap source for it.

-Dan M

[jimovonz]

Rock typically (depends on type) has a much lower specific heat compared to water. Granite for instance has a specific heat capcaity of around 300J/Kg compared to water of around 4200J/Kg (that's 14 times less!). Sometimes crushed rock/sand is used for heat storage when air is used for the heat transfer medium as it does not require any sort of sophisticated heat exchanger (the hot air/air to be heated is simply passed through the cavity containing the rock/sand). Lead is even worse at 160J/Kg. Don't confuse density with specific heat capacity!

[juiced]

What about a hollowed pad with a plastic inner-coat and water in/out holes? The concrete could have built in heat exchangers and pockets of 'dead' air. I know that this is an excessive amount of concrete, but its not the first time i have heard it to be close to water in heat effiecancy. .. on that thought, what about pure mortar?

   

[thunderhead]

Specific heat capacity of concrete is 880 joules per kg per degree C.

Specific heat capacity of water is 4200 joules per kg per degree C.

Source: http://hypertextbook.com/physics/thermal/heat-sensible/

Converting this to more usable units, a ton of concrete stores 0.22 kWh per degree C of temperature rise, but a ton of water stores 1.2kWh per degree.

Water is also much cheaper than concrete.  A heat-store to store all the energy for heating a well-insulated house is about the size of a swimming pool.

When it's heated to 95C you wouldn't want to actually swim in it, of course.

[juiced]

How do you prevent the water from damaging the property, house or becoming infested with nasties? Also, would a house with a giant pool under it stand an earthquake?

 

[skravlinge]

Water is most of the time better than rocks,  sometimes if the heating system is  air and the storage is under the house cruched rocks can store heat, the cost depends of which is cheaper at the place, an acumulating insulated tank or a hugde pile of rocks under the house. If we speak of specific heat phaseschange stuff keep a lot more than both water or rocks.

Do an experiment with  1  liter of water and heat it to 70 centigrades, do the same with   candle  leftover  bits, it will melt and hold a LOT more heat,

and it will keep the same heat until   all solid.

I think you get it dispite  English is not my native language.

[dangerous]

I have been trying to figure out the same thing. I am not interested in getting off the grid entirely, but I would like to build a wind turbine to produce electricity solely to power an electric heater. The purpose would be to take a chunk out of the utility bill. Does anyone have any links to good info about electric heater characteristics? Is AC or DC better to power these heaters?

Thank you,

David

[thunderhead]

How do you prevent the water from damaging the property, house...

I see two possibilities: either put in a big tank, probably made of something like GRP, or pour lots of concrete.  There are a number of swimming pool manufacturers who offer basement pool solutions, and I guess they've overcome these problems.  

A heat-store tank needs to be sealed, because if it isn't it will lose most of its energy through evaporation.  That prevents damage by damp.  The only other problem is the structural one of 85 tons of water, which is not really much of an issue if the basement has a poured slab and the water is in a tank.  Poured tanks might require a bit more in the way of calculations - but I wouldn't tackle this sort of a job without consulting some building professionals about the structural considerations.  Anybody who can do the calculations for a swimming pool ought to be able to figure it out.

Lots of people sell basement pool solutions - eg:-

http://www.endlesspools.com/tour/basement/

Fortunately, my father-in-law and my brother are both surveyors.

...or becoming infested with nasties?

I imagine you'd put the sort of inhibitors you'd use for airconditioning, which have to prevent the growth of bugs like Legionella.  The heat store is sealed anyway, though, so once the inhibitor has killed the bugs, new bugs will not be added, and any surviving bugs, stuck in the dark and without food, will not have much to live on.

My wife's qualification is in microbiology, and she doesn't see a problem with this.  She sees a problem with drinking water, but that's another topic.

Also, would a house with a giant pool under it stand an earthquake?

I wouldn't know ... I don't live in earthquake country, nor yet do I intend to in the future.  I guess that's one for your local structural engineer, who should be experienced in dealing with that question.

[juiced]

I dont really live in a e.q. zone either, i am just trying to point out what issue would have to looked at. We have had a couple tremors even though we arent in a 'zone'.

[ghurd]

Thermal Degradation?  Or something like that.  Can't remember much, but it seems something like if you add materiel to the water, the specific heat capacity goes up.  Like 50 pound of water is the same volume, as 50 pounds of water with 5 pound of disolved in it, that weighs 55 pounds (not real numbers), giving the same heat as 50 punds of water and 5 pounds of salt.

So, something that dissolves, even sugar or salt, would make water much better than it was.  Yes, I know salt is corrosive.  Yes I know salt water weighs less than fresh water per volume.  I'm going for the concept.

Maybe it isn't even right.

G-

[Dan M]

I never looked it up, so I'll take your word for it.  It seems a little counter-intuitive.  Although that explains why you can pour hot water into a ceramic coffee cup, make the cup really hot, and not cool the water down much at all.

I guess to make a 1:1 comparison we ought to use a heat capacity in KJ/(unit volume) instead of weight.  Water still wins though.

Thanks,

-Dan M

[johncarter]

Some interesting comments in this post, I was wondering how Volumetric heat capacities (VHC) rather than specific heat capacities (SHC) would compare, I've searched high and low for comparative fluid and solid volumetric heat capacities, and wikipedia came up with this

Dulong and Petit predicted in 1818 that VHC would be constant for all solids (the Dulong-Petit law). In fact, the VHCvaries from about 1.2 to 4.5 J/m3K. For fluids it is in the range 1.3 to 1.9J/m3K, and for gases it is a constant 0.001 J/m3K.

Some examples of SHC are here, but I can't be bothered yet to do the maths to get to VHC http://en.wikipedia.org/wiki/Specific_heat_capacity

So a solid with a high VHC would hold more heat than water even though its SHC is lower, because it is far more dense. I think!

However I am interested in the phase change waxes, could someone post more!

John