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Your refrigerator is a heat pump. If you put something warm in there its heat is drawn out to the environment heating your kitchen. A refrigerant is used to ach
by knolan 4y ago
Your refrigerator is a heat pump. If you put something warm in there its heat is drawn out to the environment heating your kitchen. A refrigerant is used to achieve this. When it’s pressure is reduced it will evaporate absorbing thermal energy from its surroundings to change phase. When pumped around it’s circuit and compressed and accordingly condenses releasing all that energy to its surroundings. The electrical energy required pumps the fluid and drives the compressor. Of course there will be some heating due to heating of the mechanical components.
A lot of homes here in Ireland (and I presume elsewhere in Europe) must be built to an ‘A level’ build energy rating. This typically means installing PV Solar or heat pumps. Rarely both.
My modest solar installation on my three year old house only provides about 40% of my electricity needs (typical daily import is 8 kWh and generation is 5 kWh). Winter is a different story.
Most heat pumps here are air to water systems. Homes don’t require AC here but you can get air to air systems that can heat or cool your home as needed. The benefit of a heat pump is it’s coefficient of performance (CoP). This is the amount of thermal energy you get out for electrical energy put in. A typical system can sustain a CoP of between 3 and 4. However this drops off as the outside temperature drops and you push up the heating demanded.
They should be as reliable and performant as your fridge or AC unit. So you many need to replace the pump or refill the refrigerant.
Another interesting technology is a so called solid state heat pump or thermoelectric module. These have an awful CoP usually much less than unity. They are interesting for thermal management due to their size however. You can aggressively cook a small high-flux component and then deal with the thermal load form the hot side of the TEC with a big cooler. You can even stack them. Their efficiency increases as the temperature difference goes to zero so a stack with a small
temperature jump between layers can be better. They also work in reverse and can therefore be used to scavenge electrical power when you have hot and cold reservoirs. For example put one on the exhaust of your car and you can harvest enough energy to charge your phone.
- Nextgrid 4y agoWhat’s the advantage of an air-to-water heat pump as opposed to an air-to-air system? Why are they used for new buildings, instead of a standard A/C indoor unit which can also offer cooling?
- sokoloff 4y agoWater can carry heat around a building more efficiently (in power and space terms) than air. In a heating dominated climate, this can make sense in a new building. (It’s also a good match temperature-wise to in-floor radiant heat.) In a retrofit situation (such as my house), it also makes sense and is cheaper than running supply and return ducts everywhere. It’s not as good a fit in mixed or cooling-dominated climates (though they can cool as well, but then you have to insulate the pipes much better to prevent condensation).
- Nextgrid 4y ago> Water can carry heat around a building more efficiently (in power and space terms) than air. Heat is carried by the refrigerant though? It only gets "converted" to air in the room itself by the indoor unit. I am talking about European-style systems where you have A/C units in every room, not the American-style with air ducts distributing air from a central unit in the utility room.
- WastingMyTime89 4y ago> European-style systems where you have A/C units in every room Which European countries are you talking about? There is no European standard regarding A/C or heating.
- Nextgrid 4y agoI didn't mean a formal standard - I checked the definitions and what I'm referring as is that US generally prefers central or "packaged" systems (single big unit in the utility room, air is piped from there into the living space through various ducts) where as Europe prefers "split" systems where you have units in each room with refrigerant pipes going back to the outdoor unit.
- sokoloff 4y agoMost of the US uses split units for central air (split meaning the condenser and evaporator are in separate units). What you’re calling a “split” is more precisely called a “ductless (mini-)split” as even an evaporator in the mechanical room and linesets carrying refrigerant to an outdoor condenser is still a (conventional) split setup.
- kevincox 4y ago> However this drops off as the outside temperature drops and you push up the heating demanded. With Irish climate and modern heat pumps this should be a non-issue. Maybe in the colder areas a day or two in the average year. Newer heat pumps can maintain very good efficiency under 0°C.
- tzs 4y ago> Newer heat pumps can maintain very good efficiency under 0°C Well under 0℃, in fact. The Mitsubishi ones are still at 200% at -18℃ (0℉), down from 300% at 0℃ (32℉). They don't fall to 100% until around -26℃ (-15℉). Fujitsu is similar. Their capacity also falls at lower temperatures going from 100% at -5℃ (23℉) to 76% at -25℃ (-13℉) so you might need to go with a bigger system in some areas.
- jillesvangurp 4y agoHeatpumps are commonly used all over scandinavia. They work fine even with extreme temperatures. Temperatures stay well above 0 Kelvin. So there's still plenty of energy to pump around. Of course with extreme temperatures you need to produce more heat. Which simply means you need a bigger setup.
- Scoundreller 4y ago> Your refrigerator is a heat pump. If you put something warm in there its heat is drawn out to the environment heating your kitchen. I’ve tried to explain to people that putting something warm outside to chill in winter before refrigerating it costs them more in electricity and they look at me like I’m insane.
- madacol 4y agoI don't understand how that conclusion follows from the quote. I still think "putting something warm outside to chill in winter before refrigerating" cost less electricity than refrigerating immediately
- Scoundreller 4y agoBy outside, I mean outdoors. By bringing "the cold" from outdoors inside, you're going to need an energy source to heat it back up when your home is in heating-mode. Even if you put it inside a small island of cold inside your home. On a net basis, you've made your home colder.
- madacol 4y agoAfter writing (and deleting) a long response, I finally get your point. You are trying to heat your home, so putting something outside to chill, is to waste heat, but putting it in the fridge would be like recycling that heat from the fridge to your room which should alleviate your room's heater burden.
- bmicraft 4y agoIf you heat your home using a heat pump, it makes no difference. If you heat with gas, you will indeed use more electricity but less gas when refrigerating immediately.
- ianschmitz 4y agoBecause what you said doesn’t make sense
- 4y ago
- dv_dt 4y agoSeems odd not to encourage both as PV solar and a heat pump go pretty well together. Is it more of a question of legislative particulars vs technology?
- knolan 4y agoIt’s down to cost. The energy rating is subdivided into thirds. An A1 home would have both but an A2 or an A3 will have just one. As long as it’s any type of A rated it’s acceptable.
- midasuni 4y agoFor a ne whole adding both wouldn’t increase the cost to the buyer - they are already willing to pay X for the house. It would increase the cost to the builder, who would then have less money to pay the land owner for the land, who had received a massive planning gain when the 50k field was given to build 100 houses and increased in value to 3m. I dont see the problem, PV and heat pumps should be mandated.