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Author Topic: The myth about "free electricity" in winter  (Read 8348 times)
DeathAndTaxes
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Gerald Davis


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October 28, 2011, 07:34:15 PM
 #61

You can't vent natural gas fumes directly into a living space... and that's not what that gas log burner does.

Yes you can. Google "ventfree gas logs" or "natural gas IR heater".

I didn't mean an natural gas IR  eater works exactly the same. I mean it is also 100% efficient and can be used to heat a home without venting heat outside.  A 30KW ventfree gas log and a 30KW natural gas IR heater will both put 30KW of thermal energy into the room at 100% efficiency.  Gas logs look nicer but are more expensive.

I have been using ventfree gas logs for 10 years now.  Natural gas when burnt completely produces only CO2 and water vapor.  I would recommend a CO dectector but I would also recommend that for any gas appliance.  It also may be against building code in some parts of the country which don't understand science.

Quote
EDIT:  That open gas burner still vents into a chimney or pipe.  You'll kill yourself from carbon monoxide (or carbon dioxide?) poisoning if you don't vent it at all.

No it doesn't.  There is no vent in that firebox.  CO is dangerous which is why you should have a CO detector.  Vent free log will only produce CO if it doesn't have sufficient oxygen (incomplete burning) but then again so will your natural gas stove or oven.  Gas logs have a ODS (oxygen depletion sensor) which should cutoff when oxygen level drops.  Always good to have them checked and cleaned (just like a furnace).   
Here is a link:
http://www.fastfireplaces.com/empire-breckenridge-deluxe-vent-free-firebox.html
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October 28, 2011, 07:53:27 PM
 #62

You can't vent natural gas fumes directly into a living space... and that's not what that gas log burner does.

Yes you can. Google "ventfree gas logs" or "natural gas heater".

I didn't mean an IR natural gas heater works exactly the same I mean it is also 100% efficient and can be used to heat a home without venting heat outside.  A 30KW gas log and a 30KW natural gas IR heater will both put 30KW of thermal energy into the room.  Gas logs look nicer but are more expensive.

I have been using ventfree gas logs for 10 years now.  Natural gas when burnt completely produces only CO2 and water vapor.  I would recommend a CO dectector but I would also recommend that for any gas appliance.  It may be against code in some parts of the country which don't understand science.

Quote
EDIT:  That open gas burner still vents into a chimney or pipe.  You'll kill yourself from carbon monoxide (or carbon dioxide?) poisoning if you don't vent it at all.

No it doesn't.  There is absolutely no vent in that firebox.
Here is a link:
http://www.fastfireplaces.com/empire-breckenridge-deluxe-vent-free-firebox.html
I stand corrected again.  Maybe I'll just shut up now...  Tongue
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October 28, 2011, 08:14:28 PM
 #63

The baseline for any electricity-based device is what using that amount of electricity would generate in heat, if it were sealed in a closed container.  For example, a 1000w air conditioner "creates" cool air for the indoors, but at the same time, creates the same amount of heat + 1000w outdoors.  The net effect, if you sealed the whole air conditioner unit in a box, is that it would be creating 1000w.  The air conditioner would be 100% efficient at creating heat.  In fact, if sealed in a box, ANY electrical device would be 100% efficient at generating heat equal to its wattage.

Again, this is why there is some confusion.  You're making a disparate comparison between a device using X amount of electricity and generating X amount of heat and a device using X amount of electricity and outputting X amount of heat.  The device is still =< 100% efficient by your definition (and can never be more than 100%).  If you are comparing the amount of heat output (X) for the amount of electricity consumed (Y), then you can achieve more than 100% efficiency.  I'm not saying your basic premise is wrong in any way, I'm just trying to clear up the confusion (but perhaps now I'm adding to it).  

The output of a device can be > 1:1 efficiency when compared to another device, but the consumption to generated ratio can never be greater than 1:1 for electricity used vs heat generated.*


* Unless we are talking about cold fusion or something exotic.

If you're searching these lines for a point, you've probably missed it.  There was never anything there in the first place.
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Gerald Davis


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October 28, 2011, 08:26:58 PM
 #64

the consumption to generated ratio can never be greater than 1:1 for electricity used vs heat generated.*

That is true but heat pumps work by generating heat they achieve efficiency by moving heat from outside to inside or in reverse.

So yes a heatpump w/ 1 KW load running for an hour will convert 1kWh of electricity into heat @ 100% efficiency but that isn't really material to practical use of the heat pump.  In operating a heat pump w/ COP of 5 would add 5 kWh of heat to the air inside the home (by removing 4 kWh* of heat from the air outside) at a cost of 1 kWh of electrical power.

Yes it is impossible to generate 5kWh of heat from 1kWh of electricity (law of conservation of energy) however it is possible to move 5kWh of heat from one place to another.  The person heating their home doesn't really care if the heat they feel is heat moved from the outside or heat converted from electricity.    The net result is still 5 units of heat from 1 unit of electricity.





* Why 4KWh?  Law of conservation of energy.  The heatpump "used" 1 kWh of electricity thus it must have converted that to another form of energy, heat. Net-net if the thermal energy inside the house rises 5kWh then the thermal energy outside the house must have declined 5kWh but the unit dumps its waste heat outside so +1 -5 = net 4kWh being removed from the outside air.
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October 28, 2011, 08:42:01 PM
 #65

The baseline for any electricity-based device is what using that amount of electricity would generate in heat, if it were sealed in a closed container.  For example, a 1000w air conditioner "creates" cool air for the indoors, but at the same time, creates the same amount of heat + 1000w outdoors.  The net effect, if you sealed the whole air conditioner unit in a box, is that it would be creating 1000w.  The air conditioner would be 100% efficient at creating heat.  In fact, if sealed in a box, ANY electrical device would be 100% efficient at generating heat equal to its wattage.

Again, this is why there is some confusion.  You're making a disparate comparison between a device using X amount of electricity and generating X amount of heat and a device using X amount of electricity and outputting X amount of heat.  The device is still =< 100% efficient by your definition (and can never be more than 100%).  If you are comparing the amount of heat output (X) for the amount of electricity consumed (Y), then you can achieve more than 100% efficiency.  I'm not saying your basic premise is wrong in any way, I'm just trying to clear up the confusion (but perhaps now I'm adding to it).  

The output of a device can be > 1:1 efficiency when compared to another device, but the consumption to generated ratio can never be greater than 1:1 for electricity used vs heat generated.*


* Unless we are talking about cold fusion or something exotic.

Yeah, this is a better way of putting it - generation vs output.
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October 28, 2011, 08:45:09 PM
 #66

Could someone please explain to me how somthing can be more than 100% efficient without allowing people to use its output to power the device for free?

A heat pump doesn't CREATE heat.  If it did it could never have more than 100% efficiency.  A heat pump MOVES heat.  There is significant heat outside the home.  Even in 0C air there is thermal energy.  The only temp that has no thermal energy is absolute zero.

If a heat pump burned fuel or turned electricity into heat via resistance its max efficiency would be 100%.  You can't get more heat/energy than what existed in the fuel/electricity to begin with.

However as a pump it can pump in huge amounts of outside energy for a small amount of energy and thus achieve >100% efficiency.

The theoretical max efficiency for a heat pump varies by the difference is desired source (outside) & sink (inside) temperatures.  For 10C outside and 35C inside is ~1200%.  The highest efficiency units available for purchase are ~500%.

As energy becomes more scarce/expensive expect heat pumps to replace furnaces.  With technology we potentially could have 600%, 750%, 800% efficiency heat pumps someday.  A furnace simply can never be more than 100% efficient (due to law of conservation of energy).

As for why couldn't you use that energy to power the device.  the thermal energy in your house is not very concentrated.  The less concentrated an energy form is the more difficult it is to convert into another form.  For example a thermalcouple can directly convert heat into electricity but it is usually less than 1% efficient.  For 100 units of heat energy = 1 unit of electrical energy.

BTW:
Air conditioners, refrigerators, freezers are all heat pumps they are simply one way heat pumps.  A residential "heat pump" can pump heat into or out of the house.


uh yeah people have seem to forgotten the law of conservation of energy..

Some people don't understand the law of conservation of energy.

If you have 100 units of energy outside the home and 10 units inside and I move 20 of those units inside via a "pump" (a energy/heat pump) then the end state is 90 units of energy outside and 20 inside.  No energy was created or destroyed.  Energy was simply moved.

my mistake Smiley
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October 28, 2011, 09:44:11 PM
 #67

The question remains? Damnit guys, don't you learn physics at school??? Like, that energy DO NOT disappear? If something use 1kw guess what, it will spit out 1kw of heat, be it a computer or a heater.

Well that statement is equally wrong.  An electric car (or any other non-resistance load that does actual work) that pulls 1kW won't generate 1kW of heat.
In the end, yes it will.

Go study physic
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October 28, 2011, 09:58:14 PM
 #68

The question remains? Damnit guys, don't you learn physics at school??? Like, that energy DO NOT disappear? If something use 1kw guess what, it will spit out 1kw of heat, be it a computer or a heater.

Well that statement is equally wrong.  An electric car (or any other non-resistance load that does actual work) that pulls 1kW won't generate 1kW of heat.

Yes it will, just not in any place or form that is usable.  In the case of the electric car, heat will be produced in the batteries, wiring, motor and braking system.

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- Carroll Quigley, CFR member, mentor to Bill Clinton, from 'Tragedy And Hope'
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Gerald Davis


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October 28, 2011, 10:43:41 PM
 #69

Come on guys it is called law of conservation of energy not the law of everything become heat.

Take an electric car drive it up a hill.  It now has potential energy, all of it's energy didn't become heat.

If car has potential energy it by definition can't have converted all of its energy into heat otherwise you just created energy from nothing.
1kWh electrical potential -> 0kWh electrical potential + 1kWh heat + xx kWh potential energy (did we magically create energy from nothing)??

vs

1kWh electrical potential -> 0kWh electrical potential + <1kWh heat + <1kWh potential energy

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October 28, 2011, 10:53:32 PM
 #70

You can't vent natural gas fumes directly into a living space... and that's not what that gas log burner does.

Yes you can. Google "ventfree gas logs" or "natural gas IR heater".

I didn't mean an natural gas IR  eater works exactly the same. I mean it is also 100% efficient and can be used to heat a home without venting heat outside.  A 30KW ventfree gas log and a 30KW natural gas IR heater will both put 30KW of thermal energy into the room at 100% efficiency.  Gas logs look nicer but are more expensive.

I have been using ventfree gas logs for 10 years now.  Natural gas when burnt completely produces only CO2 and water vapor.  I would recommend a CO dectector but I would also recommend that for any gas appliance.  It also may be against building code in some parts of the country which don't understand science.

Quote
EDIT:  That open gas burner still vents into a chimney or pipe.  You'll kill yourself from carbon monoxide (or carbon dioxide?) poisoning if you don't vent it at all.

No it doesn't.  There is no vent in that firebox.  CO is dangerous which is why you should have a CO detector.  Vent free log will only produce CO if it doesn't have sufficient oxygen (incomplete burning) but then again so will your natural gas stove or oven.  Gas logs have a ODS (oxygen depletion sensor) which should cutoff when oxygen level drops.  Always good to have them checked and cleaned (just like a furnace).   
Here is a link:
http://www.fastfireplaces.com/empire-breckenridge-deluxe-vent-free-firebox.html

Vent free used to be illegal in Baltimore but just in the past few years code was changed (harmonized?) to a more national standard and they are now allowed.  Vent free is in most places 5x cheaper then heating with resistance electric heat due to the low cost of natural gas and the near 100% efficiency.  Vent free does have other drawbacks besides the CO2 risk, it puts a lot of humidity in the air, actually enough to do damage to items in the long term.

I have a vent free gas heater in a bathroom, which would be humid anyhow. 

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October 28, 2011, 11:27:02 PM
 #71

The question remains? Damnit guys, don't you learn physics at school??? Like, that energy DO NOT disappear? If something use 1kw guess what, it will spit out 1kw of heat, be it a computer or a heater.

Well that statement is equally wrong.  An electric car (or any other non-resistance load that does actual work) that pulls 1kW won't generate 1kW of heat.

Yes it will, just not in any place or form that is usable.  In the case of the electric car, heat will be produced in the batteries, wiring, motor and braking system.

Don't forget the wheels, all that weight deforming them as they roll definetly make lots of heat (and of course even if the wheels were rock solid they would still be moving against the ground)


edit: and of course, unless the room is completly evacuated there is also air friction.

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October 29, 2011, 12:14:13 AM
 #72

Come on guys it is called law of conservation of energy not the law of everything become heat.

Take an electric car drive it up a hill.  It now has potential energy, all of it's energy didn't become heat.

This is where the old maxium "what goes up (the hill) must come down again" applies.  Eventually, it will be heat, even if that car sits at the top of that hill until the heat death of the universe.  Probably.

"The powers of financial capitalism had another far-reaching aim, nothing less than to create a world system of financial control in private hands able to dominate the political system of each country and the economy of the world as a whole. This system was to be controlled in a feudalist fashion by the central banks of the world acting in concert, by secret agreements arrived at in frequent meetings and conferences. The apex of the systems was to be the Bank for International Settlements in Basel, Switzerland, a private bank owned and controlled by the world's central banks which were themselves private corporations. Each central bank...sought to dominate its government by its ability to control Treasury loans, to manipulate foreign exchanges, to influence the level of economic activity in the country, and to influence cooperative politicians by subsequent economic rewards in the business world."

- Carroll Quigley, CFR member, mentor to Bill Clinton, from 'Tragedy And Hope'
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October 29, 2011, 02:19:19 AM
 #73

Come on guys it is called law of conservation of energy not the law of everything become heat.

Take an electric car drive it up a hill.  It now has potential energy, all of it's energy didn't become heat.

This is where the old maxium "what goes up (the hill) must come down again" applies.  Eventually, it will be heat, even if that car sits at the top of that hill until the heat death of the universe.  Probably.
Moonshadow is right, when you bring a weight to the top of the hill or pump air into a can, you're creating the potential for movement. You're essentially creating potential energy that once released will produce heat+movement. After each fall, you will have less useful kinetic energy to bring it back up to same height.
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October 29, 2011, 02:27:46 AM
 #74

Not to mention the heat generated to get it there in the first place.

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October 29, 2011, 02:38:47 AM
 #75

Not to mention the heat generated to get it there in the first place.

Seriously. I was sweating my balls of by the time I got that weight up there.

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October 29, 2011, 10:04:41 AM
 #76

i wasnt thinking outside the box..i thought someone meant how a simply heating coil could magically be a better convertor of electrical energy into heat energy compared to a gpu..damn studying medicine has sucked the physics out of meehh..cant believe i got a 97% in my alevel physics Sad
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October 31, 2011, 12:59:25 PM
 #77

I have a bucket that weighs 0.2 kg and contains 1 kg of boiling water. The thermal energy of the water in my bucket is mass * heat capacity of water * temperature in Kelvin = 1 kg * 4.2159 J/g/K * 373.15 K = 1.573 MJ. Now I lift this bucket with boiling water 1 meter straight up, the labour I need to do this is mass * gravitational field strength * distance = 1.2 kg * 9.81 N/kg * 1 m = 11.8 J. I moved 13330000% more energy than I used energy to move it, but I did not create any energy.

This example demonstrates the difference between moving energy and using energy. This example is not a heat pump though, since there is no transfer of thermal energy between masses, the mass itself is moved instead. The "efficiency" of a heat pump is expressed in how much energy it moves between masses compared to how much energy it uses to do so. Note that using energy just means transforming energy from one form (e.g. electricity) to another (e.g. heat), not making energy disappear.

My own house is not heated by heat pumps but by a central heating system, where various gas burners at the top floor of the flat heat water and pump it through mostly unisolated metal tubes to radiators inside the apartments. I cannot answer whether I have "free electricity" in winter, because while gas is cheaper than electricity in my country, I don't know how efficient the central heating system is (definitely lower than 100% when counting only the heat that ends up in my home) nor what gas-price the landlord charges me per kWh of heat brought to my home. There is no singular answer to the "free electricity"-question because it depends on the specific prices and efficiencies of the various heating systems available in a region. Comparing the price-ratio and efficiency-ratio between GPU-heating and other heating, will determine whether you save or spend more money when mining compared to other heating. Even when spending more, since you also get Bitcoin rewards, you may still come out with profit.
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November 03, 2011, 11:20:20 AM
 #78

A very popular solution to heating here is ground heat and it is very energy efficient. Drill a hole about 100m down or so and pump around water in it when the water comes up it is about 4-5C and you can extract one degree each time in a heat pump to heat a hot water tank and pump it around your house. Is very efficient.

However at least in my parents house there is a backup electrical heating of the water that usually kicks in when the outdoor temperature goes below -15C or so for long periods. So I guess there are still a couple of days in winter where mining would not be a complete waste with such a setup Smiley

My heat however comes from garbage incendiaries and is included in the rent and so is the electricity so that makes calculation very easy for me Smiley

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November 05, 2011, 12:23:21 AM
 #79

99% of all households use any other source than electric power for heating
What?  Really?  Do you have a source for this?

b) winters which don't have many days below 10C.
Where I live, we call that "summer".  Cheesy

Winter temperatures rarely go over -10C.
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November 05, 2011, 12:41:21 AM
 #80

xsnippedx

That's why automobiles are now fitted with EGR valves - it actually recycles some of the exhaust gases in an effort to burn even more of the fuel that may have been left unburnt during the previous burn cycle.  A typical modern internal combustion engine is around 30% efficient at moving the vehicle - the rest of the energy from burning gasoline is wasted as heat, with a tiny percentage wasted as unburnt fuel.

Just pointing out, EGR valves primary purpose is not an effort to use unburnt fuel in the exhaust, although that is a desirable effect as well.

Their purpose is so that under light load conditions (crusing along at highway speeds, going downhill, etc..) the engine can use less fuel to maintain your momentum. The exhaust gas contains very little useable oxygen, so that instead of filling the cylinders with a full charge of fresh highly oxygenated air and the matching amount of fuel, you can instead partially fill the cylinder with fresh air, and partially with exhaust gas, thereby requiring less fuel to achieve a proper mixture. Engine continues turning at the same speed, still produces enough power as required at that time, and saves fuel.

EGR was strictly introduced to improve fuel economy.

Edit to add, recent engine designs with variable valve timing which allows control of intake and exhaust timing independently no longer have EGR valves. They simply use the valve timing to close the exhaust valve sooner and delay opening of the intake valve. This actually traps some exhaust gas in the cylinder between cycles. Still works like EGR, but instead of an external bypass it does it all with cam timing. Reverse this, and hold the exhaust valve open longer and open the intake sooner, introduces a concept called "scavenging" whereby the flow of exhaust out of the cylinder helps to draw in fresh air more efficiently, and they can achieve much closer to perfect volumetric efficiency. This would be the performance side of the VVT system vs the economy side which replaced those EGR valves.
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