Hacker News Reader

Comment by jdblair | Hacker News Reader

The article makes the common (and grating) error of conflating power (1.5 gigawatts) and energy (power over time). Put another way, "1.5 gigawatts" does not in any way describe a rate. Do they mean 1.5 gigawatts per hour? or per day? or per year?

I'm referring to this section: ...the rate that energy builds below the volcano is only around 1.5 gigawatts - less heat than a typical power plant sheds. Yellowstone currently bleeds heat at a rate of about 4.5 to 6 gigawatts, mostly through heated water moving below the surface.

View on HN

You made a correct assertion initially "power (1.5 gigawatts) and energy (power over time)," but then failed to use it correctly. 1.5 gigawatts is a rate, of 1.5 billion joules per second.

Gigawatts is a rate, which gets multiplied by an amount of time to measure an amount of energy.

That's why your energy bill is based on kilowatt-hours. If you have a device that consumes power at a rate of one kilowatt (say a toaster oven) and you run it for one hour, that's one kilowatt-hour (kWh) of energy.

Kilowatt-hours is a pointless unit.

1 Watt (unit of power) is 1 Joule (unit of energy) per second. So "1 Watt-second" is just a needlessly-long way of saying "1 Joule".

Instead of using the idiotic kW-h units, they should just use kJ. (1 kW-h = 3600 kJ or 3.6MJ.)

>> Do they mean 1.5 gigawatts per hour? or per day? or per year?

1.5 gigawatts is 1.5 billion joules per second. If you sustain that power for 2 hours it will produce 3 gigawatt-hours of energy.

1 watt-hr is 3600 joules because 1J/s for 3600 seconds.

Huh? A watt is a joule per second, [energy/time]. They are describing rates.

If you build a 1.5 GW heat engine on top of Yellowstone (assuming it's possible) the energy that builds below the volcano is 0, because you captured it and turned some of it into electricity, and dumped the waste heat into a river or the atmosphere.

This is incorrect.

Power is energy "over" time.

> Put another way, "1.5 gigawatts" does not in any way describe a rate

It most certainly does. It's 1.5 gigajoule per second.

The best part of this comment is the confidence!

Is it any surprise that LLMs trained over internet comments are wrong with a similar confidence?

Watts are a rate. Joules per second.

whoops! ok, yes, my physics is all wrong here. thanks for correcting!

Your physics is all fucked up dude (very grating).

Reply on news.ycombinator.com