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coryrc commented on The first sodium-ion battery EV is a winter range monster   insideevs.com/news/786509... · Posted by u/andrewjneumann
dtgriscom · 16 hours ago
Question: if a LiIon battery can't deliver as much energy when cold, where does the lost energy go? Is it just unavailable, and becomes available again when warmed up? Is discharge less efficient, so the energy is wasted? Or does charging stop early when cold, so there's less to be discharged in the first place?
coryrc · 16 hours ago
> Is discharge less efficient, so the energy is wasted?

Yes. It's mostly wasted as heat inside the battery. I think there's also a temperature relationship to open-circuit voltage? But the predominate effect is from elevated internal resistance.

coryrc commented on Pretty soon, heat pumps will be able to store and distribute heat as needed   sintef.no/en/latest-news/... · Posted by u/PaulHoule
modo_mario · 3 days ago
1. Are there not scenarios where it drops below 1? The stats for them always seem optimistic scenarios given what i hear from people during winter cold spell in houses that aren't absolutely perfectly insulated. If your water term needs to remain above 70C and it's starts freezing hard outside during winter when that COP starts to matter the most for example.
coryrc · 3 days ago
If there were, you installed the wrong equipment.
coryrc commented on The Great Unwind   occupywallst.com/yen... · Posted by u/jart
throw0101c · 4 days ago
> 2008 was caused, in part, by the governments deciding many "banks" were "too big to fail".

Perhaps worth noting that Ben Bernanke, who was the chair of the Fed at the time, was/is one of the most top experts on Great Depression (it's the work he later won the Nobel Prize for). So as bad as the GFC was, Bernanke thought it could get really bad and pushed for measures that he probably thought would prevent another 1930s scenario.

coryrc · 4 days ago
So, the NPE isn't a real Nobel Prize :) but if the only allowable decisions are to concentrate wealth at the top, then we're just delaying and amplifying the collapse.
coryrc commented on The Great Unwind   occupywallst.com/yen... · Posted by u/jart
pjc50 · 4 days ago
> I'm not happy I was prevented from buying fire sale assets

People who want a society-wide crisis so they can profit off it are far more morally reprehensible than people who said "we'll loosen the mortgage criteria a bit so people can buy houses, houses always go up in value right?"

coryrc · 4 days ago
Uh, no, we're having a generational crisis because wages are flat and rent cost has been growing for decades. That's quite reprehensible. Unfortunately, in our push for home ownership, we now have a majority of people being homeowners and opposed to lowering prices, and a few companies who can make a profit lobbying to ensure prices only go up.
coryrc commented on The Great Unwind   occupywallst.com/yen... · Posted by u/jart
Aurornis · 4 days ago
The people angry about the 2008 bailout usually have little interest in the facts. I’ve had countless conversations where I’ve tried to tell people that the bailouts were a net positive or that people were, in fact, sent to jail. Outside of people familiar with finance, most people refuse to believe it.

A lot of people I’ve talked to about it weren’t even adults when the bailout happened. They weren’t watching the news and didn’t care at the time. They only know it through pop culture and from fiery speeches from politicians and influencers.

The idea of a bailout has become synonymous with the government handing hard-earned tax dollars over to banks, no strings attached. The facts don’t really matter.

coryrc · 4 days ago
2008 was caused, in part, by the governments deciding many "banks" were "too big to fail".

The fix was for the government to pick some winners, coercively lend them money and force them to buy the failing banks.

Now we have fewer, bigger banks. People who were conservative with money, saved instead of over-leveraging, did not get to buy assets cheaply, because the government propped up asset prices with unlimited, cheap money.

And TARP did eventually produce weak positive returns. So I'm glad they didn't lose money, but I'm not happy I was prevented from buying fire sale assets. I'm also not happy residential housing prices are 2x what they were in 2010 (and still well over 1.5x the peak of the bubble).

coryrc commented on Pretty soon, heat pumps will be able to store and distribute heat as needed   sintef.no/en/latest-news/... · Posted by u/PaulHoule
ZeroGravitas · 6 days ago
Home hot water heating in the UK with heat pumps is about 250-300% efficient (slightly lower than the efficiency of home heating but still much better than resistive).

No one is storing 1000C water at home.

It is true that the temperature deltas affects efficiency. You can use the thermocline to draw from the cooler lower portion of the storage tank to push this further. Or less technically, just a bigger tank, though this has some tradeoffs.

In warmer countries they are set up differently can act as free air conditioning by extracting heat from indoor air at the same time as heating water.

coryrc · 5 days ago
> No one is storing 1000C water at home.

Right, but UK has/had "storage heaters" which were bricks with nichrome wire. They would heat the bricks really hot during cheap electricity times, and use that heat the rest of the day.

EDIT: I misread "ripping out these energy storage devices" as https://en.wikipedia.org/wiki/Storage_heater

Of course heat pumps for DHW should all have a tank for smoothing demand across several hours.

coryrc commented on Pretty soon, heat pumps will be able to store and distribute heat as needed   sintef.no/en/latest-news/... · Posted by u/PaulHoule
modo_mario · 6 days ago
Isn't it better to heat the water up to a point (let's say 40 or 50 degrees) and to heat it the rest of the way with resistance heating?

>Versus resistance, which is exactly as efficient at 0°C and 1000°C

It isn't. The difference is smaller than for a heatpump tho obviously.

coryrc · 5 days ago
1. No, absolutely not. Why would you settle for COP=1 when you can have COP>1?

2. The electrical to heat conversion efficiency is indeed 100% regardless of the temperature of the resistor. And if you're putting out 1000W, then all input losses are also identical. If you put a 1000W light bulb in the middle of your room, or 2 of them but run both at 500W, you'll get EXACTLY the same heat output in your room, but the single bulb is much hotter.

coryrc commented on Pretty soon, heat pumps will be able to store and distribute heat as needed   sintef.no/en/latest-news/... · Posted by u/PaulHoule
leoedin · 6 days ago
Every air-to-water heat pump install will have a hot water tank. So I'm not sure why "don't work well" is the term used.

It is true that heat pumps coefficient of performance drops as the output temperature increases. So you need a proportionally larger hot water tank to store the same amount of energy. So it is fair to say there are tradeoffs. But hot water storage is still a necessary part of most heat pump installs - because peak output of heat pumps tends to be below the heat demand of showers.

coryrc · 5 days ago
EDIT: I misread "ripping out these energy storage devices" as https://en.wikipedia.org/wiki/Storage_heater which are basically bricks with nichrome wire.

You're right, of course heat pump water heaters use tanks to smooth out DHW demand, but that same thing isn't feasible for space heating.

coryrc commented on Ask HN: Who is hiring? (February 2026)    · Posted by u/whoishiring
rossng · 7 days ago
Yes
coryrc · 6 days ago
Thanks!
coryrc commented on Pretty soon, heat pumps will be able to store and distribute heat as needed   sintef.no/en/latest-news/... · Posted by u/PaulHoule
DrScientist · 7 days ago
Indeed.

In the UK there was a unfortunate trend of ripping out these energy storage devices and replacing hot water tanks with on demand electric hot water heating ( only heat the water you need ). And new builds often have no tanks ( as it saves space in the new tiny homes ).

Very short sighted in my view - a very simple way to store energy and everyone uses hot water directly.

coryrc · 7 days ago
They don't work well with heat pumps. Heat pumps lose efficiency as the differential increases, so if you try to store heat in a tank, you quickly drop capacity and efficiency.

Versus resistance, which is exactly as efficient at 0°C and 1000°C, and why those storage heaters used to make sense.

(And storage is directly proportional to temperature differential above interior ambient)

u/coryrc

KarmaCake day4540July 11, 2008
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