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Pretty soon, heat pumps will be able to store and distribute heat as needed

sintef.no

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Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#221

Post by jandrese »

Youden wrote: post #95
baggachipz wrote: post #86

Earlier quoted context omitted.

heat pump for house !== heat pump for hot water

I don't know what it's like where you're living but here in Switzerland it's completely normal to have one heat pump that does both. Here there's a lot of floor heating, which also uses water, so you usually just run one loop to the "boiler" (a water tank with a copper loop for the water from the heat pump to circulate through) and one through the floor and have a valve to switch which is running through the heat pum…

That's a different kettle of fish entirely, largely because with the heat pump water heater they're pulling the heat from the inside of your house, forcing you to move it twice when it is cold out. With a combined unit you only move it once, as the other side of the unit is outside.

That's why they're so great for warm climates though. The water heater also cools your house, especially as that heat is then lost down the drain. Everybody in the south should be jumping on these.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#222

Post by sandinmyjoints »

cromka wrote: post #71
chankstein38 wrote: post #57

They should've used lasagna. You could be in a tundra heating it over a fire and, as long as you get it sufficiently and consistently hot, it'll still burn your mouth 20minutes later.

I was recently wondering if any particular type of food contributes to mouth cancer prevalence and I concluded that at the top of that list would be be lasagna and cherry tomato on a pizza/in a soup.

Why?

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#223

Post by tootie »

gwbas1c wrote: post #178
tootie wrote: post #133

Earlier quoted context omitted.

Presumably it's air source and if it's indoors it will just be the air in whatever room it's in. That's how my ventless dryer works. I'm not sure what the implications are for taking heat from air that may have been heated by another heat pump are for efficiency. But also if it's summertime, they may be relieving load from your air conditioner.

> That's how my ventless dryer works. Do you mean a heat pump dryer? Those aren't taking heat from the room; they work by sending the air inside the unit through a powerful dehumidifier. (I have one, it's very nice.)

A dehumidifier is the same thing as an air conditioner. The coolant coils are still just exposed to the ambient air in the room. The same way a window air conditioner drips moisture, the dryer is like a backwards air conditioner that blows cold air into the room and hot air into the drum and condensed water drips down the drain. I suppose it ultimately doesn't matter once you open the dryer door and everything mixes together.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#224

Post by cromka »

sandinmyjoints wrote: post #222
cromka wrote: post #71

Earlier quoted context omitted.

I was recently wondering if any particular type of food contributes to mouth cancer prevalence and I concluded that at the top of that list would be be lasagna and cherry tomato on a pizza/in a soup.

Why?

Mouth burns or bites can lead to cancer

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#225

Post by wolrah »

afiori wrote: post #146
dataflow wrote: post #129

Earlier quoted context omitted.

Only works adequately if your microwave is the rarer kind that actually lowers the power (inverter), instead of just switching between 100% and 0% repeatedly.

This should depend on the frequency of the switching, if it is every few seconds it should behave sorta the same

Another important part is that a lot of microwave recipes specifically state to leave the food in the microwave for a period of time after it's done cooking, and often stir it after that. Almost no one actually does that.

Most people think they should be able to put food in, nuke it at full power for as short of a time as possible, and then immediately shove it in their face with no consequence and we all know that doesn't work yet most of us will keep doing it anyways.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#226

Post by gwbas1c »

tootie wrote: post #223
gwbas1c wrote: post #178

Earlier quoted context omitted.

> That's how my ventless dryer works. Do you mean a heat pump dryer? Those aren't taking heat from the room; they work by sending the air inside the unit through a powerful dehumidifier. (I have one, it's very nice.)

A dehumidifier is the same thing as an air conditioner. The coolant coils are still just exposed to the ambient air in the room. The same way a window air conditioner drips moisture, the dryer is like a backwards air conditioner that blows cold air into the room and hot air into the drum and condensed water drips down the drain. I suppose it ultimately doesn't matter once you open the dryer door and everything mixes…

My heat pump dryer does not blow cold air into the room. (My heat pump water heater does.)

The air inside the dryer is cycled through a dehumidifier and then the water is pumped out into a drain. This is in contrast to a typical US dryer that just blows hot air into the drum and then out a tube outside. Apparently most of the world doesn't do it like we do.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#227

Post by coryrc »

leoedin wrote: post #188
coryrc wrote: post #108

Earlier quoted context omitted.

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)

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 install…

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.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#228

Post by coryrc »

modo_mario wrote: post #176
coryrc wrote: post #108

Earlier quoted context omitted.

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)

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.

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.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#229

Post by coryrc »

ZeroGravitas wrote: post #157
coryrc wrote: post #108

Earlier quoted context omitted.

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)

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, thoug…

> 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.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#230

Post by dataflow »

afiori wrote: post #146
dataflow wrote: post #129

Earlier quoted context omitted.

Only works adequately if your microwave is the rarer kind that actually lowers the power (inverter), instead of just switching between 100% and 0% repeatedly.

This should depend on the frequency of the switching, if it is every few seconds it should behave sorta the same

Yes but I've never seen it be every few seconds. Every time I've seen, it's quite prolonged.
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