Normal Operating Sounds • Hacker News Board

Re: Normal Operating Sounds

#271

Post by flutas » Mon, Nov 27, 2023, 9:46 PM UTC

Kirby64 wrote: post #255

flutas wrote: post #203

Earlier quoted context omitted.

Something else interesting when supercharging in the cold...LOTS of steam(?) at times. Shocked me the first time it happened. Cold (~5F outside), low and hot battery (just went from 80 to ~5%). Legit thought the car was on fire at first.

Never experienced the steam myself, although I can't say I've ever tried supercharging the car at 5F. Coldest I've ever done it was probably in the 40s, which is plenty cold enough to cause that popping sound when it's pulling 250kW.

Oh yeah, the popping was crazy loud as well.

Thinking back to it, the battery must have been extremely warm at the time too, since that 5F was after two hours through a 2 lane mountain road (crossing the range).

Re: Normal Operating Sounds

#272

Post by quesera » Sat, Dec 02, 2023, 3:56 AM UTC

jffry wrote: post #176

quesera wrote: post #172

Earlier quoted context omitted.

Using a cryptominer or GP computer at full tilt for the purpose of making heat is less than 100% efficient, because some of the input power gets used on computing. A pure resistive heater is also less than 100% efficient, but it's very very close.

Where does the energy "used on computing" go? The power consumption of a CPU is dissipated as heat.

So, I think I understand this view from the thermodynamics sense. First law and all.

But by this construction, are all systems which take energy as input (and do not convert it to another form for storage) de facto 100% efficient?

When we talk about a (very old) furnace being 75% efficient at turning the chemical energy of a fossil fuel into heat energy, is the 25% loss purely combustion byproducts with some inherent chemical energy plus some non-combusted fuel?

Re: Normal Operating Sounds

#273

Post by jffry » Sat, Dec 02, 2023, 2:19 PM UTC

quesera wrote: post #272

jffry wrote: post #176

Earlier quoted context omitted.

Where does the energy "used on computing" go? The power consumption of a CPU is dissipated as heat.

So, I think I understand this view from the thermodynamics sense. First law and all. But by this construction, are all systems which take energy as input (and do not convert it to another form for storage) de facto 100% efficient? When we talk about a (very old) furnace being 75% efficient at turning the chemical energy of a fossil fuel into heat energy, is the 25% loss purely combustion byproducts with some inherent…

In this case for heating, efficiency is how much of the energy input gets converted into heat in the space you're heating.

So for a resistive electric heater, you're dissipating all of the energy as heat (minor quibbles about electromagnetic radiation or status LEDs aside). The same is true for your computer.

Burning hydrocarbons have two main sources of energy loss: incomplete combustion, and energy carried away by exhaust gases. Obviously furnace design influences both of these - the US federal minimum is 78%, but high-end furnaces with all the tricks can get over 90% per https://www.energy.gov/energysaver/furnaces-and-boilers

Heat pumps are the third major category, and they are more than 100% efficient because they are using their energy to steal a larger amount of thermal energy from the outdoors air and move it to inside your home (and much of the electric energy they consume is eventually discharged as heat inside your home as well).