House Lights, Electric Heat, Winter, and Entropy

[ajdelange]

Opening the fridge will warm your house. True!

Back in the days when a STU was a half rack of equipment we put one in a small room that was not tied into the building's HVAC system. When you turned the thing on it got hot in there so our genius facilities guy went to Home Depot, bought a window air conditioning unit and hung it from the ceiling. I got a call from one of the gals that worked in this area complaining that the A/C must be broken because when they turned it on it got even hotter in there. Our facilities guy was a piece of work.

Since it was mentioned in the title I'll point out the the heat transfer from the A/C unit to the air in the room caused the entropy of that air to increase.

 

[passedpawn]

Light is not heat, but it does carry energy. The light emitted by a bulb definitely does turn into heat when those photons hit something. But, according to this a light bulb is about 2% efficient at turning electricity into light in the first place.

https://en.m.wikipedia.org/wiki/Luminous_efficacy

So, your 60W bulb is already a 58.8W electric heater and the energy carried by visible light is minuscule. You're spreading 1.2W of energy, in the form of light, all over the illuminated surfaces... so how much does the LIGHT from a bulb warm a room? Not much!

If you have LED lights the efficiency is much higher, around 10%, but the light consumes many fewer watts. So again, you end up with a couple of watts carried away as light and the rest turned into heat inside the LED, which radiates away.

What were we talking about? I'm getting a beer.

Right, light is a form of energy, and energy is never destroyed, but it can be converted into another form of energy such as heat.

For the sake of clarity, let's just assume that 60W bulb is 100% efficient - that all of the electrical power goes into light. So, now you have this energy in the form of light bouncing around a room. Where does that energy go when the light is absorbed by the walls? I know it's all converted to something, because when I turn the lights off, it gets dark in there. If, as I claim, all 60W is being turned to heat at the walls, then the 60W 100% efficient bulb is also a 100% efficient heater due to the radiative heating of the walls.

I'm not claiming that you can heat your house by leaving the lights on, but I'm suggesting that there's no point in turning them off since they contribute perfectly to your electric heater's job of heating your house.

 

[GilaMinumBeer]

LED light bulb won't heat a room by itelf, I know that. But my point is that there are NO losses, so just leave it on. ALL of the energy put into it become heat, 100%. I keep saying this over and over and it doesn't seem to register.

When you say "lost to atmospheric wasteland", do you mean it will "heat my house"?

You stop. You stop this non-sense right fvcking now, dammit!

I JUST got my 10 year old into the habit of turning the fvcking light off when he leaves the room.

What's next? You going to try to spin the physics that the piss on the toilet seat saves monies on ass moisturizers?

 

[Homercidal]

Replace all your bulbs with infrared bulbs and get even more heat! (And a cool new ambiance too!)

 

[elbinwyp]

Right, light is a form of energy, and energy is never destroyed, but it can be converted into another form of energy such as heat.

For the sake of clarity, let's just assume that 60W bulb is 100% efficient - that all of the electrical power goes into light. So, now you have this energy in the form of light bouncing around a room. Where does that energy go when the light is absorbed by the walls? I know it's all converted to something, because when I turn the lights off, it gets dark in there. If, as I claim, all 60W is being turned to heat at the walls, then the 60W 100% efficient bulb is also a 100% efficient heater due to the radiative heating of the walls.

I'm not claiming that you can heat your house by leaving the lights on, but I'm suggesting that there's no point in turning them off since they contribute perfectly to your electric heater's job of heating your house.

You are missing a key assumption: that your heat source is also 100% efficient. Technology has moved beyond that though. Ductless Mini-splits are performing at COP's above 2, more than doubling the efficiency of your lights.

 

[ajdelange]

Replace all your bulbs with infrared bulbs and get even more heat! (And a cool new ambiance too!)

If fact you wouldn't. If a device draws 100 watts (not 100 volt-amperes; 100 real watts) it will deliver 341.2142 BTU of heat per hour to the system provided that no energy from it escapes the system. The light inside a plywood box commonly used to keep fermenting beer at reasonable temperature delivers exactly as much heat to the interior of the box as an electric 'heater' of the same wattage. The air conditioner in the STU closet delivered exactly as much heat to that closet as would have been delivered by a heater that consumed the same number of watts.

Apparently several people here don't understand that but neither did the graduate engineer we hired to keep our building's systems running!

 

[GilaMinumBeer]

Replace all your bulbs with infrared bulbs and get even more heat! (And a cool new ambiance too!)

 

[dryboroughbrewing]

I have windows, which means my house is not a closed system, so my absorption of visible spectrum light isn't 100% as they are transparent to most of the wavelengths so emitted. Further my windows are made of a low emissivity glass, which means that they'll preferentially trap non-visible wavelength photons (including all those lovely lovely IR photons that my heater kicks out). But yeah all the light hitting visible light opaque objects would be absorbed.

 

[passedpawn]

I have windows, which means my house is not a closed system, so my absorption of visible spectrum light isn't 100% as they are transparent to most of the wavelengths so emitted. Further my windows are made of a low emissivity glass, which means that they'll preferentially trap non-visible wavelength photons (including all those lovely lovely IR photons that my heater kicks out). But yeah all the light hitting visible light opaque objects would be absorbed.

You'll need to get rid of those windows then But you can leave your closet lights on all winter

 

[Zuljin]

Here's some more untoward reactions to the suns radiation. I wish I'd seen this before I rolled my spent projection TV to the curb.

https://www.youtube.com/watch?v=jrje73EyKag

I will be curb hunting for one soon.

 

[The_Bishop]

Well, to look at at in one way, all energy is a type of radiation, it depends on where it is in the spectrum.

That being said, it's not strictly the light that's warming the earth. There's a good deal of radiation spread over the spectrum, from infrared to ultraviolet and more. Visible light is only a small portion of that spectrum.

 

[GilaMinumBeer]

You'll need to get rid of those windows then But you can leave your closet lights on all winter

Please do be careful while huddled around your heat producing LED for warmth. You wouldn't want to risk burning your sack.

 

[Dimax]

What do you think happens to light after it leaves the bulb? It turns to heat when it hits an object. Some of it might get reflected, but ultimately it all gets absorbed and turns into heat.

So, for a lamp, whether LED or incandescent or fluorescent, the rated wattage will all end up as heat.

How many Led lights would I need to fit in a tin can to heat my primary in my fermenting chamber to 68 degrees in a 45 degree room for 2 weeks?

 

[ajdelange]

Well, to look at at in one way, all energy is a type of radiation, it depends on where it is in the spectrum.

The kinetic energy of a speeding bullet is not a form of radiation.
The gravitational potential energy of a rutabaga on top of the refrigerator isn't a form of radiation.
The chemical energy in a stick of dynamite is not a form of radiation nor is the energy stored in a wound spring or a magnetic field or in a bottle of compressed gas....

 

[passedpawn]

How many Led lights would I need to fit in a tin can to heat my primary in my fermenting chamber to 68 degrees in a 45 degree room for 2 weeks?

If the insulation is good enough, 1 LED lamp would cause your fermentor to boil. Temperature is the accumulation of heat energy. Heat energy will accumulate at a rate dependent on the temperature difference between the inside and the outside of the chamber and the heat conductivity of the chamber walls. With a high enough R-rating, your fermentor will go "china syndrome"

 

[TallDan]

You're clearly very confused. We call them "light bulbs" but "dark suckers" would be a more accurate name. They do not create light, but instead, suck the darkness out of the room and pump it out of the house via the power lines. When the darkness is removed, a light room remains.

 

[ajdelange]

How many Led lights would I need to fit in a tin can to heat my primary in my fermenting chamber to 68 degrees in a 45 degree room for 2 weeks?

That would depend on whether you put the series current limiting resistors in the can with the diodes or drove the array with an external 3V supply.

 

[MrFancyPlants]

I just point out that some of the light is probably escaping out the windows of your house.

 

[TallDan]

I just point out that some of the light is probably escaping out the windows of your house.

You mean that the windows are letting more darkness in.

 

[doug293cz]

@elbinwyp brought it up earlier, but perhaps too subtly for some to pick up on. If you really want to improve the efficiency of your electric heating, get a heat pump. They are much more efficient than resistive electric heat, in that they can pump more energy into your house (from the ambient outside your house) than the amount of electric energy they consume.

"heat pumps are three to four times more efficient in their use of electric power than simple electrical resistance heaters." https://en.wikipedia.org/wiki/Heat_pump​

If using a heat pump for primary heating, then supplementing with light bulbs (of any type) will reduce your overall energy efficiency. Whether it's measurable or is another question.

Brew on

 

[passedpawn]

@elbinwyp brought it up earlier, but perhaps too subtly for some to pick up on. If you really want to improve the efficiency of your electric heating, get a heat pump. They are much more efficient than resistive electric heat, in that they can pump more energy into your house (from the ambient outside your house) than the amount of electric energy they consume.

"heat pumps are three to four times more efficient in their use of electric power than simple electrical resistance heaters." https://en.wikipedia.org/wiki/Heat_pump​

If using a heat pump for primary heating, then supplementing with light bulbs (of any type) will reduce your overall energy efficiency. Whether it's measurable or is another question.

Brew on

Right, heat pumps cheat because they aren't creating all the heat from electricity. They scavange from outside. But they do supplement with resistive heat when it's really cold outside and they can't keep up. I have a heat pump like this.

Many many FL homes, even large ones, have only resistive heaters in the air handlers for heating.

 

[Zuljin]

You're clearly very confused. We call them "light bulbs" but "dark suckers" would be a more accurate name. They do not create light, but instead, suck the darkness out of the room and pump it out of the house via the power lines. When the darkness is removed, a light room remains.

Which is why the night sky and outter space is dark. The sun is sucking all the darkness into space. And there is A LOT of darkness in space.

 

[The_Bishop]

The kinetic energy of a speeding bullet is not a form of radiation.
The gravitational potential energy of a rutabaga on top of the refrigerator isn't a form of radiation.
The chemical energy in a stick of dynamite is not a form of radiation nor is the energy stored in a wound spring or a magnetic field or in a bottle of compressed gas....

You are correct, I misspoke. I meant to say that all forms of radiated energy are on the same spectrum, with the difference being the wavelength.

I can only defend myself by stating that I was:
A, typing on my cellphone and
B, in a hurry.

 

[passedpawn]

You are correct, I misspoke. I meant to say that all forms of radiated energy are on the same spectrum, with the difference being the wavelength.

I can only defend myself by stating that I was:
A, typing on my cellphone and
B, in a hurry.

[pedantic warning] Unless you consider sound waves a type of radiation. I do.

They are longitudinal, not transverse, and mechanical vs electromagnetic and whatever-the-hell-light-is-when-god's-rolling-the-dice. But I kinda like to think of sound waves in the same way because a lot of the physics is similar.

But then you'd have to include the motion of the sea... so maybe scratch that.

 

[The_Bishop]

Ok, listen. I'm stuck at the firehouse on a 24 hour shift, and therefore bereft of my kegorator which is a mainstay support for me when having these forms of brain-bruising conversations, so you quit that right now.

 

[jbunton]

Simple solution is to just get a flux capacitor and be done with all of this nonsense

 

[elbinwyp]

Right, heat pumps cheat because they aren't creating all the heat from electricity. They scavange from outside. But they do supplement with resistive heat when it's really cold outside and they can't keep up. I have a heat pump like this.

Many many FL homes, even large ones, have only resistive heaters in the air handlers for heating.

Technology!!! Days of electric resistance backup are over. There are several models of heat pumps out there that are rated down to -13F and maintain 100% capacity down to 5F and 75% capacity at -13F. I just had an 18,000btu/hr unit installed for $4000.

http://www.mitsubishipro.com/en/pro...-zone/m-series-heat-pump-systems/msz-femuz-fe

 

[Zuljin]

Light is a particle.

 

[passedpawn]

Light is a particle.

Wave!!!

 

[harrke]

[emoji112]🏻