Topic: The myth about "free electricity" in winter (Read 9365 times)

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.

What?  Really?  Do you have a source for this?

Where I live, we call that "summer". 

Winter temperatures rarely go over -10C.

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

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

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.

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

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

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

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.

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.

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.

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. 

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

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.

In the end, yes it will.

Go study physic

my mistake

Yeah, this is a better way of putting it - generation vs output.

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.

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.

I stand corrected again.  Maybe I'll just shut up now... 

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.


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