Thermodynamics!

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jderimig said:
... put up a small windmill and mechanically drive a paddle in a tank. No generator and electrical costs, 100% efficient mechanical energy conversion into heat. Plus you can heat water at night.
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Is any company selling those as a product/system or are they mostly DIY?
 
Funkworks said:
Is any company selling those as a product/system or are they mostly DIY?
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I don't think those are available turnkey. I knew of one where I used to live (western NY)where an engineer built one to heat his pool. Extended his pool season quite a bit. Pretty simple design, windmill blades to right angle gear vertical shaft down to splash tank.
 
jderimig said:
I don't think those are available turnkey.
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I think you're right. I've just spent most of my lunch hour looking for one and I still don't seen any at page 10 of https://www.ecosia.org/. I'm wondering about ideal paramters: what an ideal paddle looks like, paddle size vs tank size, turbine blade size vs tank size, etc.
 
Funkworks said:
I think you're right. I've just spent most of my lunch hour looking for one and I still don't seen any at page 10 of https://www.ecosia.org/. I'm wondering about ideal paramters: what an ideal paddle looks like, paddle size vs tank size, turbine blade size vs tank size, etc.
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The part that goes in the water doesn't matter. All the motion gets converted into heat no matter what the shape. Flat boards is good enough. The only consideration is the paddles cant be too big that is stalls the windmill at light winds and enough drag so the windmill doesn't spin too fast in moderate winds. The part that's in the air is probably better to look like the old farm pumping windmills. Lots of low end torque for direct drive of the splashing shaft.
 
jderimig said:
The part that goes in the water doesn't matter. All the motion gets converted into heat no matter what the shape. Flat boards is good enough. The only consideration is the paddles cant be too big that is stalls the windmill at light winds and enough drag so the windmill doesn't spin too fast in moderate winds. The part that's in the air is probably better to look like the old farm pumping windmills. Lots of low end torque for direct drive of the splashing shaft.
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Wow. Right out of the old thermo 101 textbook, a driven propeller in a perfectly insulated box. I guess if you put enough work in, and insulate it to keep the converted heat energy from leaving... remember some imperial units conversion constant called the "mechanical equivalent of heat"? ft-lb to BTU's or some such...

So I have no feel for these parameters at all. How much work can be done by the wind turbine (like you said, similar to an Aermotor), and what's the insulation needed on the tank?

Little recollection... I had to go to a power station west of Kingston, Jamaica, and passed through an area that had a lot of newer, very small homes, looked like some kind of government housing. And every one had a solar hot water system. Kinda makes sense in that locale... they were thermal collectors, not PV. The poverty of that area was truly sad, and the price they pay for electricity is outrageous.
 
Blast it Tom! said:
Wow. Right out of the old thermo 101 textbook, a driven propeller in a perfectly insulated box. I guess if you put enough work in, and insulate it to keep the converted heat energy from leaving... remember some imperial units conversion constant called the "mechanical equivalent of heat"? ft-lb to BTU's or some such...

So I have no feel for these parameters at all. How much work can be done by the wind turbine (like you said, similar to an Aermotor), and what's the insulation needed on the tank?

Little recollection... I had to go to a power station west of Kingston, Jamaica, and passed through an area that had a lot of newer, very small homes, looked like some kind of government housing. And every one had a solar hot water system. Kinda makes sense in that locale... they were thermal collectors, not PV. The poverty of that area was truly sad, and the price they pay for electricity is outrageous.
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Making a few assumptions… a farm irrigation pump is probably on the order of a few horsepower, or 1-2 kW. I believe that a typical electric water heater is around 5 kW. So it probably won’t do the whole job but it might pick up a decent fraction.
 
Blast it Tom! said:
How much work can be done by the wind turbine (like you said, similar to an Aermotor), and what's the insulation needed on the tank?
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Yes this ⬆️. Lots of things to figure out: How hot do I want the water to be? How fast do I want it to get there? How much wind in the area? What kind of material and insulation for the tank? What kind of spout/lid/piping?

In any case, I think the first question to answer is how much wind there is. So the first thing I'd do is get an anemometer and collect data over I dunno, a year I guess. Need to know how much energy is available each week or months on average.

Of course I could simply hack with whatever I find, see what I get, and update the parts over time to optimize.
 
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Funkworks said:
Yes this ⬆️. Lots of things to figure out: How hot do I want the water to be? How fast do I want it to get there? How much wind in the area? What kind of material and insulation for the tank? What kind of spout/lid/piping?

In any case, I think the first question to answer is how much wind there is. So the first thing I'd do is get an anemometer and collect data over I dunno, a year I guess. Need to know how much energy is available each week or months on average.

Of course I could simply hack with whatever I find, see what I get, and update the parts over time to optimize.
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Once you know the wind speed, I would probably work backwards. How big a windmill can you stomach? From there, you're going to decide how much of the system you're going to redneck* and how much you're going to buy. Insulation will be as much as you can add reasonably, and it would be better to keep the warm water tank inside anyway.

Rather than a paddle, you might think about just getting a windmill well pump system. It'll dump energy into the water just as well as a paddle, and it's already designed for the job. Pipe fittings are also easier to connect to tanks and keep watertight and potable than a redneck paddle system.

* I truly mean no disrespect here. I mean assembling stuff together out of stuff you already have on hand for minimum money and larger time outlay.

Wind resources here at very large scale. Your local wind will depend heavily on local geographic features. There are no doubt far more local maps available. The other bonus of these maps is that you can really see the effects of the boundary layer.
 
boatgeek said:
Once you know the wind speed, I would probably work backwards. How big a windmill can you stomach? From there, you're going to decide how much of the system you're going to redneck* and how much you're going to buy. Insulation will be as much as you can add reasonably, and it would be better to keep the warm water tank inside anyway.

Rather than a paddle, you might think about just getting a windmill well pump system. It'll dump energy into the water just as well as a paddle, and it's already designed for the job. Pipe fittings are also easier to connect to tanks and keep watertight and potable than a redneck paddle system.

* I truly mean no disrespect here. I mean assembling stuff together out of stuff you already have on hand for minimum money and larger time outlay.

Wind resources here at very large scale. Your local wind will depend heavily on local geographic features. There are no doubt far more local maps available. The other bonus of these maps is that you can really see the effects of the boundary layer.
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I say "hack" or "DIY" instead. Maybe when I'm done building model rockets, I'll set up a windmill somewhere. Heating a water tank might just be the simplest off-grid system there is.

Other projects I'm interested in are heat engines.

https://en.wikipedia.org/wiki/Heat_engine
 
Funkworks said:
I say "hack" or "DIY" instead. Maybe when I'm done building model rockets, I'll set up a windmill somewhere. Heating a water tank might just be the simplest off-grid system there is.

Other projects I'm interested in are heat engines.

https://en.wikipedia.org/wiki/Heat_engine
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I've always been fascinated by the Stirling engine. All you need is a hot side. I've always wondered about using a solar parabolic trough to heat water for the hot side. I have a 40' x 100' barn running east/west with lots of room inside to put a bigger Stirling engine, probably to run an electric generator & then use that to heat water in the house.
 
Greg Furtman said:
I've always been fascinated by the Stirling engine. All you need is a hot side. I've always wondered about using a solar parabolic trough to heat water for the hot side. I have a 40' x 100' barn running east/west with lots of room inside to put a bigger Stirling engine, probably to run an electric generator & then use that to heat water in the house.
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Co-gen is the best option. I wouldn't use heat source -> mechanical work -> generate electricity -> heat water. It would be better to cut out the middleman and just use heat -> heat water.

The Ttirling engine would be useful if you want to do some mechanical work with the solar heat. Then use some of the waste heat from the engine to heat water.
 
jderimig said:
I don't think those are available turnkey. I knew of one where I used to live (western NY)where an engineer built one to heat his pool. Extended his pool season quite a bit. Pretty simple design, windmill blades to right angle gear vertical shaft down to splash tank.
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Why on earth would I want a gearbox when could just have one of those unidirectional helical designs on a fixed shaft?
 
dhbarr said:
Why on earth would I want a gearbox when could just have one of those unidirectional helical designs on a fixed shaft?
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Just a pair of bevel gears at the fan shaft to down shaft. But yes, one of those egg beater mills would do, but that is a more costly fan
 
Funkworks said:
In any case, I think the first question to answer is how much wind there is. So the first thing I'd do is get an anemometer and collect data over I dunno, a year I guess. Need to know how much energy is available each week or months on average.
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websites that already have that info:
1.
https://www.climate.gov/maps-data/dataset/average-wind-speeds-map-viewer2.
https://www.wunderground.com/history3.
https://www.visualcrossing.com/reso...r-data/where-can-i-find-historical-wind-data/
 
Well, this has sat a few days, so since the thread is titled "Thermodynamics", I'll send us off in a different sort of direction... Las Year we gave my daughter our old refrigerator. She keeps it in their attached garage. Her complaint, now verified as it heads into its second winter, is that the freezer doesn't get cold during the winter, and actually lest things thaw out. Now this is the reverse of the heat pump issue we discussed earlier up in the thread. Now the heat rejection should go even better- cold garage, hot condenser. So I don't think problems in the basic refrigeration cycle is the issue. I'm thinking something in the controls - maybe the refrigerator (not freezer) temperature is not kicking the thing on as that is the "I need cold" criteria.

Hope everyone has a wonderful Thanksgiving!
 
Blast it Tom! said:
Well, this has sat a few days, so since the thread is titled "Thermodynamics", I'll send us off in a different sort of direction... Las Year we gave my daughter our old refrigerator. She keeps it in their attached garage. Her complaint, now verified as it heads into its second winter, is that the freezer doesn't get cold during the winter, and actually lest things thaw out. Now this is the reverse of the heat pump issue we discussed earlier up in the thread. Now the heat rejection should go even better- cold garage, hot condenser. So I don't think problems in the basic refrigeration cycle is the issue. I'm thinking something in the controls - maybe the refrigerator (not freezer) temperature is not kicking the thing on as that is the "I need cold" criteria.

Hope everyone has a wonderful Thanksgiving!
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Could be a passive system from the evaporator coils: all cold air goes through the freezer before coming down into the fridge. Cold garage means a low duty cycle. Low duty cycle means little cooling going into the freezer.
 
Blast it Tom! said:
Well, this has sat a few days, so since the thread is titled "Thermodynamics", I'll send us off in a different sort of direction... Las Year we gave my daughter our old refrigerator. She keeps it in their attached garage. Her complaint, now verified as it heads into its second winter, is that the freezer doesn't get cold during the winter, and actually lest things thaw out. Now this is the reverse of the heat pump issue we discussed earlier up in the thread. Now the heat rejection should go even better- cold garage, hot condenser. So I don't think problems in the basic refrigeration cycle is the issue. I'm thinking something in the controls - maybe the refrigerator (not freezer) temperature is not kicking the thing on as that is the "I need cold" criteria.

Hope everyone has a wonderful Thanksgiving!
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I've always wondered for those of us who live in cold climes why fridge manufacturers never made a fridge that would just pull in cold air from outside when available and then run the compressor when needed. Here in NW Wisconsin we often have 3 months when it rarely gets above freezing and is often below zero.
 
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Greg Furtman said:
I've always wondered for those of us who live in cold climes why fridge manufacturers never made a fridge that would just pull in cold air from outside when available and then run the compressor when needed. Here in NW Wisconsin we often have 3 months when it rarely gets above freezing and of often below zero.
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My in laws used the "Idaho freezer": leave stuff out in the unheated garage here it stays below freezing.
 
Greg Furtman said:
I've always wondered for those of us who live in cold climes why fridge manufacturers never made a fridge that would just pull in cold air from outside when available and then run the compressor when needed. Here in NW Wisconsin we often have 3 months when it rarely gets above freezing and of often below zero.
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Piping would complicate installation and outdoor temp is still very variable. I don't think it'd be much cheaper energy wise. Besides, a refrigerator does emit heat so it actually helps warming the house.

I never wish for lockdowns, but if it ever happens again:



the-most-interesting-man-in-the-world-queso-espinosa.jpg
 
Blast it Tom! said:
She keeps it in their attached garage. Her complaint, now verified as it heads into its second winter, is that the freezer doesn't get cold during the winter, and actually lest things thaw out.
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A malfunction in the defrost cycle?
boatgeek said:
My in laws used the "Idaho freezer": leave stuff out in the unheated garage here it stays below freezing.
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Two years ago when we had very cold weather in Texas and some neighborhoods lost power, our house was down to about 50 degrees inside and I was concerned about things in the refrigerator going bad so I put them outside in the back of my wife's car.
 
boatgeek said:
My in laws used the "Idaho freezer": leave stuff out in the unheated garage here it stays below freezing.
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My grandfather used the trunk of a Chevy Impala that stopped running a few decades ago and has been sitting in the pasture ever since. It was a very spacious trunk, could keep a lot of stuff very cold.
 
Funkworks said:
Like a sand battery but with less sand and more bricks:

https://rondo.com/products
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Interesting, but it's basically like a peak shaver, storing electrical energy from the grid and then recovering it via normal heat transfer, that is blowers. Not to say it isn't useful, but there's a lot of hype in the front page without them saying what it actually is - heat a stone by the fireplace and put it down by your feet to keep them warm. I.e. it's useful, but hardly revolutionary.
 
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Funkworks said:
Just came accross a field of research where people try to make heat pumps that work better in colder climates.

https://www.energy.gov/eere/buildings/residential-cold-climate-heat-pump-challenge
Not surprising that they're working on this. Sounds interesting to follow just how heat pumps can be better designed for ever colder temperatures.
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instead of trying to get a heat pump to extract heat when it's very very cold outside, it just makes so much more sense to dig a hole and put the coil down in the ground and use geothermal heat where it is a constant 55 degrees all year round. geothermal is the largest energy source that we have and we haven't even begun to scratch the surface of using the heat and energy that is available to us from it.
 
hobie1dog said:
instead of trying to get a heat pump to extract heat when it's very very cold outside, it just makes so much more sense to dig a hole and put the coil down in the ground and use geothermal heat where it is a constant 55 degrees all year round. geothermal is the largest energy source that we have and we haven't even begun to scratch the surface of using the heat and energy that is available to us from it.
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This makes a lot more sense to me. It's especially effective where you need heat in winter and AC in summer.
 
hobie1dog said:
instead of trying to get a heat pump to extract heat when it's very very cold outside, it just makes so much more sense to dig a hole and put the coil down in the ground and use geothermal heat where it is a constant 55 degrees all year round. geothermal is the largest energy source that we have and we haven't even begun to scratch the surface of using the heat and energy that is available to us from it.
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What's always strange to me is that they dig such massive holes. I would think cutting a trench then just driving loops straight down would be easier manpower/equipment wise. Presumably there's a reason they do it this way, such as using cheaper material.
 

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