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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

#131

Post by jonstewart »

tempestn wrote: post #124
jandrese wrote: post #62

I've been keeping an eye on heat pump water heaters for awhile, but right now they mostly make sense in warm climates. The big problem is they're still specialty products and marked up like crazy, but also they tend to use cheap components which makes them loud and prone to failure. If you run A/C for the majority of the year then they pay themselves back reasonably quick, barring early failure, but in colder climate…

We somewhat accidentally ended up with a good combo: we have a ventless heat pump dryer, and a heat pump water heater, also in the laundry room. So when doing laundry, the water heater cools the room while the dryer heats it, so they roughly cancel out. As an aside, HP dryers are really elegant tech, and it's a shame they're not more common. They use the heat pump not just to heat the air in the dryer, but also to co…

I bought a Samsung HP dryer a few years ago and it'd be great except for a terrible design flaw where lint gets trapped in its heat sink fins, turning into a soggy mess.

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

#132

Post by Marsymars »

karussell wrote: post #100
Xylakant wrote: post #65

Earlier quoted context omitted.

Thermal solar panels have the advantage of being very simple and surprisingly effective. But if you're lacking space to put up both solar cells and thermal, you can use combined panels which have a solar cell with a backing thermal system. The interesting thing is that these combined panels outperform solar cells even when it comes to electricity generated because solar panels loose efficiency as they heat up, so coo…

The problem with thermal solar panels is that you can use its heated water only if it gets warmer than the water in your system, which is not always the case, especially in winter. Compared to nearly 100% usable energy from normal solar panels. Furthermore if you have a heatpump you can convert this electric energy into heat energy with a factor of >3 (COP).

Yeah but if you're in a northern climate your solar panels are only generating like 10% of their summer capacity in the winter anyway due to sun hours/angles... winter is just tough for capturing solar energy in general.

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

#133

Post by tootie »

gwbas1c wrote: post #90

The article omits some critical details: It says this is both a "heat pump" and also "storage" AND says that it will run when electricity is cheap or plentiful. Thus: 1: Where does it pump the heat from? (Or is this not really a "heat pump" and instead is using resistive heating?) 2: How long does it store heat? Is this something that will store heat on a 24-48 hour basis, or will this store heat during the spring /…

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.

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

#134

Post by vel0city »

dataflow wrote: post #129
esseph wrote: post #117

Earlier quoted context omitted.

Microwave tip: Use the power button to select a lower power level, and cook the food for longer.

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.

I don't have the fancier inverter style. Setting a power level still works pretty well even though flawed. Drawing out the overall cooking time still manages to get things more evenly heated in the end when you give the food time to distribute the heat throughout the food.

Cooking food for 2 minutes at 50% power gives a noticeable difference in average temperature compared to cooking food for 1 minute at 100% power and waiting a minute.

And I don't always know what it decides to do as far as turning the magnetron on and off on its sensor modes, but it'll spend a while doing automated reheat and potatoes and what not and it'll be dang near perfect every time.

Don't get me wrong I'd love an inverter microwave, truly a better option. But its not like the duty cycle process has no impact.

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

#135

Post by apatheticonion »

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.

Also pies

https://www.youtube.com/watch?v=aEAHLFvD3v4

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

#136

Post by gwbas1c »

mike-the-mikado wrote: post #98
gwbas1c wrote: post #90

The article omits some critical details: It says this is both a "heat pump" and also "storage" AND says that it will run when electricity is cheap or plentiful. Thus: 1: Where does it pump the heat from? (Or is this not really a "heat pump" and instead is using resistive heating?) 2: How long does it store heat? Is this something that will store heat on a 24-48 hour basis, or will this store heat during the spring /…

I would guess that is intended for a daily cycle, perhaps using air source heat pumps at times of day when the air temperatures are higher and electricity prices are lower, then using it as required. As it works on phase change (e.g. think of melting ice) heat is added (or removed) without changing the temperature of the store (which, I guess, might be hotter or colder than where the heat is extracted or used).

But how hot does the heat source have to be?

Depending on the needs, resistive heating can get hundreds of degrees hot, but the best heat pumps that I know of can only raise the temperature about 60 or 70° f.

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

#137

Post by chongli »

vel0city wrote: post #134
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.

I don't have the fancier inverter style. Setting a power level still works pretty well even though flawed. Drawing out the overall cooking time still manages to get things more evenly heated in the end when you give the food time to distribute the heat throughout the food. Cooking food for 2 minutes at 50% power gives a noticeable difference in average temperature compared to cooking food for 1 minute at 100% power a…

It's funny, because the inverter microwave is actually cheaper to build nowadays. It uses a small switching power supply to generate the needed voltage to run the magnetron at different power levels. The older style duty cycle microwaves use a huge transformer to generate the high voltage, which makes them way heavier and more expensive due to all that copper.

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

#138

Post by tempestn »

jonstewart wrote: post #131
tempestn wrote: post #124

Earlier quoted context omitted.

We somewhat accidentally ended up with a good combo: we have a ventless heat pump dryer, and a heat pump water heater, also in the laundry room. So when doing laundry, the water heater cools the room while the dryer heats it, so they roughly cancel out. As an aside, HP dryers are really elegant tech, and it's a shame they're not more common. They use the heat pump not just to heat the air in the dryer, but also to co…

I bought a Samsung HP dryer a few years ago and it'd be great except for a terrible design flaw where lint gets trapped in its heat sink fins, turning into a soggy mess.

We have a Whirlpool that I love, but they discontinued it a couple years ago with no replacement, and I can't imagine why. I guess most people just shop on price, so it didn't sell. Like I said, a shame.

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

#139

Post by sbierwagen »

Marsymars wrote: post #130
5ersi wrote: post #109

It uses phase change (solid to liquid) to store heat at about 200 kJ/kg. Compare this to heating water in a boiler from 10c to 60c - stores 209 kJ/kg. So we already have an effective way to store heat which can work for decades without servicing and is also cheap to produce (in terms of money and energy consumption).

There are also existing commercially-available residential units (e.g. Ecombi or Steffes) using ceramic bricks that are in the ~450 kJ/kg range.

Note for the confused: Ecombi achieves this by heating the bricks to dramatically higher temperatures using conventional resistive heating elements, thereby storing more energy, even though the specific heat capacity of any ceramic material is dramatically inferior to that of water.

But, as a result, Ecombi has a much lower system efficiency than a heat pump, since it's essentially just a space heater pointed at a rock. It only makes sense for jurisdictions with time-of-day variable pricing of electricity, and trades off simplicity and low initial purchase price for lifetime cost.

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

#140

Post by grigri907 »

AlexandrB wrote: post #80
hnburnsy wrote: post #12

Related, TIL the US is effectively banning residential electric resistance water heaters in 2029, with heat pump water heaters being the only type that can meet the new standards. Users will see a 2-3x in cost difference and a 3 to 8 year payback on savings.

The problem with heat pumps replacing electric heaters (in cold climates) is that the waste cold air gets dumped into the house and needs to be heated again. Generally, electric water heaters are expensive to run compared to gas ones, so people use them in places a gas heater is not possible to install (e.g. no way to vent the exhaust). This also means that the heat pump would have nowhere to vent cold air. This kind…

Your heat pump ought to be venting the cold air outside in the first place. If you're pulling the heat for your water out of your conditioned air, yeah you're in a losing battle.
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