5 ms·

I always thought about this growing up. How the engine’s heat is used directly to heat the cabin and there is no heater. Also my gaming PC in the winter. It f

I always thought about this growing up. How the engine’s heat is used directly to heat the cabin and there is no heater. Also my gaming PC in the winter. It feels like free compute given I’m heating anyways.

bigyikes 3y ago
> Also my gaming PC in the winter. It feels like free compute given I’m heating anyways. Totally. If it's cold and you have an idle rig, you might as well use it to run a crypto miner before reaching for an actual heater.
- xur17 3y ago
  Assuming you use electric resistive heat. The math changes a bit for gas or heat pumps.
- Rebelgecko 3y ago
  Actual heating systems can be better than 100% efficient, while crypto mining or cinebench or whatever is <100%
  - koverda 3y ago
    what do you mean?
    - kalleboo 3y ago
      Heat pumps which use energy to move heat around are more efficient than using energy to generate heat directly.
    - vGPU 3y ago
      Heat pumps can provide an “efficiency” of some 300-400%+. The “trick” is that they use electricity to move heat instead of creating heat, which is why heat pumps stop working well under a certain temperature. They kinda work like a reverse refrigerator. A fridge takes heat out from the inside and moves it to the outside. A heat pump does the opposite.
      - stephen_g 3y ago
        You’ve completely failed to answer their actual question, it was the claim of less than 100% efficient heating they were asking about…
        vGPU 3y ago
        No. He was replying to this post: > Actual heating systems can be better than 100% efficient, while crypto mining or cinebench or whatever is <100%. The intricacies of why a crypto minor is less than 100% efficient when working as a heater are easily deduced, unless you’re precisely the sort of midwit that likes to leave replies such as the one you left.
  - josephcsible 3y ago
    How can anything be <100% if producing heat is the goal? Where would the rest of the energy be going?
    - wardedVibe 3y ago
      They mean a heat pump. You apply work to transfer heat, getting more inside than if you had just turned the energy into heat directly; the outside gets colder of course. https://en.wikipedia.org/wiki/Heat_pump#Principle_of_operation https://en.wikipedia.org/wiki/Heat_pump#Principle_of_operati...
      - josephcsible 3y ago
        Yes, heat pumps are over 100%, but isn't turning the energy into heat directly exactly 100%?
        Adverblessly 3y ago
        As a random thought, for resistive heating some energy is definitely "lost" as light.
        krallja 3y ago
        Even light will eventually be absorbed by some surface and become heat.
    - stephen_g 3y ago
      I’m not sure what they mean about crypto miners or computers (mentioning cinebench), basically all the energy going in should be turned into heat so that should be near enough to 100% efficient. Where else would the energy be going? Sure, there will be a bit of RF power (Wi-Fi and some EMI) and depending on the device, a bit of light (LED indicators, monitor backlight) but that should be tiny compared to the energy that will end up as heat… In terms of heating systems though, it’s normal for fuel based systems to be <100% because you need to vent exhaust, and a lot of your heat your fuel produced can be rejected away from where you want it with that. For example, older gas boilers might only be 80% efficient or so, and even the much more efficient condensing boilers are still only in the low 90s.
- jowea 3y ago
  Won't you damage your GPU faster by doing that?
anikan_vader 3y ago
It's free electricity, but a computing device still makes for a pricey space heater.
jacquesm 3y ago
A gasoline based ICE is so incredibly inefficient it needs to shed heat or it would melt down. It makes more heat than that it makes motive power (the thing it is designed to do...). A 50 KW engine makes 200 KW(!!) of heat (at full throttle). Most of that heat energy exits the system through the exhaust gases but there is plenty that gets stuck in the body of the engine and you need to remove it from there somehow before it causes damage. That's where your cooling system comes in, a coolant (typically: water or glycol or a mixture) passes through its own channels in the engine around the thermally loaded parts such as the cylinder and head walls to remove the heat. This coolant is pumped around in the engine using the coolant pump to a radiator, usually located at the front of the car in the airstream to help reject the heat to the environment. The interior heater of a car basically just re-routes a bit of that heat in the cooling system into the cabin through a miniature radiator with a fan connected to it that doesn't vent into the environment but into the cabin. So there is plenty of waste heat to go around. Some diesels got so efficient though that they needed an extra in-line heater to have enough heat for the cabin in specific operating domains (low power engine, low revs). It is effectively co-generation: you get two different kinds of energy (motive and heat) and you use them for different purposes.
- dmix 3y ago
  I always wonder how you know so much about so many topics to make quality comments on a wide variety of topics on HN. Truly a jack of all trades. Maybe it's like how I spend so much time reading random Wikipedia articles on topics because I need to know how everything works.
  - jacquesm 3y ago
    Hm... too many projects :) And that list is only getting longer, I think I'll pass it on to my kids. Right now (and for the past couple of years) it has been mostly music but also still some more interesting tools to play with. Currently making a set of super realistic traffic lights for my youngest including pedestrian crossing and automatic cycle influencing (road coil pickup to detect car presence in front of the lights) for his model cars. Green wave, the works. I've mostly stopped writing up the projects, but still have a bunch of posts pickled that I probably should finish. Most recent software bit: ear training module for pianojacq.com is work in progress (press low 'A' on an 88 key keyboard to enable the secret menu that will enable the ear trainer, it is not quite ready for mass consumption yet but it is getting there).
afavour 3y ago
Unfortunately I have a vivid memory of the opposite: driving an extremely decrepit old car through the south in July, had to crank the heat to max to try to direct the heat away from the engine. No AC in the car, naturally.
- JoBrad 3y ago
  I also have this memory. The A/C is a heat pump that just pulled heat to/from the radiator, which is used for both the engine and the A/C. So turning on the heat causes the thermostat to be tripped faster (or so I was told), moving heat away from the engine. You had to be moving for this to work well, especially if your thermostat was going bad.

bigyikes 3y ago

> Also my gaming PC in the winter. It feels like free compute given I’m heating anyways. Totally. If it's cold and you have an idle rig, you might as well use it to run a crypto miner before reaching for an actual heater.

xur17 3y ago
Assuming you use electric resistive heat. The math changes a bit for gas or heat pumps.
Rebelgecko 3y ago
Actual heating systems can be better than 100% efficient, while crypto mining or cinebench or whatever is <100%
- koverda 3y ago
  what do you mean?
  - kalleboo 3y ago
    Heat pumps which use energy to move heat around are more efficient than using energy to generate heat directly.
  - vGPU 3y ago
    Heat pumps can provide an “efficiency” of some 300-400%+. The “trick” is that they use electricity to move heat instead of creating heat, which is why heat pumps stop working well under a certain temperature. They kinda work like a reverse refrigerator. A fridge takes heat out from the inside and moves it to the outside. A heat pump does the opposite.
    - stephen_g 3y ago
      You’ve completely failed to answer their actual question, it was the claim of less than 100% efficient heating they were asking about…
      - vGPU 3y ago
        No. He was replying to this post: > Actual heating systems can be better than 100% efficient, while crypto mining or cinebench or whatever is <100%. The intricacies of why a crypto minor is less than 100% efficient when working as a heater are easily deduced, unless you’re precisely the sort of midwit that likes to leave replies such as the one you left.
- josephcsible 3y ago
  How can anything be <100% if producing heat is the goal? Where would the rest of the energy be going?
  - wardedVibe 3y ago
    They mean a heat pump. You apply work to transfer heat, getting more inside than if you had just turned the energy into heat directly; the outside gets colder of course. https://en.wikipedia.org/wiki/Heat_pump#Principle_of_operation https://en.wikipedia.org/wiki/Heat_pump#Principle_of_operati...
    - josephcsible 3y ago
      Yes, heat pumps are over 100%, but isn't turning the energy into heat directly exactly 100%?
      - Adverblessly 3y ago
        As a random thought, for resistive heating some energy is definitely "lost" as light.
        krallja 3y ago
        Even light will eventually be absorbed by some surface and become heat.
  - stephen_g 3y ago
    I’m not sure what they mean about crypto miners or computers (mentioning cinebench), basically all the energy going in should be turned into heat so that should be near enough to 100% efficient. Where else would the energy be going? Sure, there will be a bit of RF power (Wi-Fi and some EMI) and depending on the device, a bit of light (LED indicators, monitor backlight) but that should be tiny compared to the energy that will end up as heat… In terms of heating systems though, it’s normal for fuel based systems to be <100% because you need to vent exhaust, and a lot of your heat your fuel produced can be rejected away from where you want it with that. For example, older gas boilers might only be 80% efficient or so, and even the much more efficient condensing boilers are still only in the low 90s.
jowea 3y ago
Won't you damage your GPU faster by doing that?

anikan_vader 3y ago

It's free electricity, but a computing device still makes for a pricey space heater.

jacquesm 3y ago

A gasoline based ICE is so incredibly inefficient it needs to shed heat or it would melt down. It makes more heat than that it makes motive power (the thing it is designed to do...). A 50 KW engine makes 200 KW(!!) of heat (at full throttle). Most of that heat energy exits the system through the exhaust gases but there is plenty that gets stuck in the body of the engine and you need to remove it from there somehow before it causes damage. That's where your cooling system comes in, a coolant (typically: water or glycol or a mixture) passes through its own channels in the engine around the thermally loaded parts such as the cylinder and head walls to remove the heat. This coolant is pumped around in the engine using the coolant pump to a radiator, usually located at the front of the car in the airstream to help reject the heat to the environment. The interior heater of a car basically just re-routes a bit of that heat in the cooling system into the cabin through a miniature radiator with a fan connected to it that doesn't vent into the environment but into the cabin. So there is plenty of waste heat to go around. Some diesels got so efficient though that they needed an extra in-line heater to have enough heat for the cabin in specific operating domains (low power engine, low revs). It is effectively co-generation: you get two different kinds of energy (motive and heat) and you use them for different purposes.

dmix 3y ago
I always wonder how you know so much about so many topics to make quality comments on a wide variety of topics on HN. Truly a jack of all trades. Maybe it's like how I spend so much time reading random Wikipedia articles on topics because I need to know how everything works.
- jacquesm 3y ago
  Hm... too many projects :) And that list is only getting longer, I think I'll pass it on to my kids. Right now (and for the past couple of years) it has been mostly music but also still some more interesting tools to play with. Currently making a set of super realistic traffic lights for my youngest including pedestrian crossing and automatic cycle influencing (road coil pickup to detect car presence in front of the lights) for his model cars. Green wave, the works. I've mostly stopped writing up the projects, but still have a bunch of posts pickled that I probably should finish. Most recent software bit: ear training module for pianojacq.com is work in progress (press low 'A' on an 88 key keyboard to enable the secret menu that will enable the ear trainer, it is not quite ready for mass consumption yet but it is getting there).

afavour 3y ago

Unfortunately I have a vivid memory of the opposite: driving an extremely decrepit old car through the south in July, had to crank the heat to max to try to direct the heat away from the engine. No AC in the car, naturally.

JoBrad 3y ago
I also have this memory. The A/C is a heat pump that just pulled heat to/from the radiator, which is used for both the engine and the A/C. So turning on the heat causes the thermostat to be tripped faster (or so I was told), moving heat away from the engine. You had to be moving for this to work well, especially if your thermostat was going bad.