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Comment by gregmac | Hacker News Reader

Why aren't there integrated systems for heating/cooling? (Or maybe this exists and I just don't know the proper terms to search for)

We have multiple cooling devices: air conditioning (dumping heat outside) and refrigerators (dumping heat inside). Then we have multiple separate heating devices: furnaces and hot water tanks that burn electricity or gas to generate heat.

I've always thought it would be more efficient if these units were all connected with some kind of coolant loop, and a heat pump / control unit that could route heat/cooling to where it's needed.

I did find a similar system for connecting air conditioning to heat a swimming pool (instead of outside condenser unit), which is pretty neat, but I'm thinking bigger. If you're going to dump excess heat anyway, might as well use it to heat water, at least.

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Lot's of small reasons.

You don't want to transport heat a far distance (thermal loss becomes too high), so keeping the vent for the refrigerator integrated into the unit is generally better than shipping it off outside.

CoP is the lift you get from a heat pump given a specific delta-T. The smaller the delta-T (like an air conditioning unit's 90F->70F), the more efficient you can make it. If you group a bunch of components together with different target temperatures, you'd either effectively have 2 lines (so 2 systems), or run the system at the lowest temperature you care about. 2 systems is what you have today, and 1 system with high delta-T would have a much worse CoP.

And other reasons...

Also refrigerant has a very high carbon cost and installing piping on site between all of these appliances would require more refrigerant to fill those pipes and a higher potential for leaks.

Refridgerators are pretty low power. Transporting heat works fine for tens of km in district heating. But you probably have some better energy efficiency investments than building insulated pipes and a secondary water circuit + heat exchanger or running long stretches of expensive refrigerant in the pipes, for the fridge's 50 watts worth of heat.

There are thermal battery suppliers out there (a quick search turned up Sunamp, one I hadn't heard of before) that can be part of that kind of system. Geothermal heat exchangers as floatrock mentioned are probably the cheapest general version that use the ground as a thermal battery but don't typically have interlinked systems - and they're much more than a typical air-cooled system.

The show This Old House showed an interesting system a few years ago at [1] that used liquid loop HVAC components and thermal batteries as a tech demonstrator. There's also systems in newer high rises that have linked loops such that the hot side of the building (sun-facing) can pre-heat the heat pumps of the cold-side (shaded) portion of the building. These rely on advanced systems that don't tend to be deployed in homes (utilizing newer building management systems and newer HVAC like variable refrigerant flow to get the best efficiency).

Ultimately, things like this are expensive and uncommon so require per-site design that very few can justify because the payoff period is pretty long as you have the one-off cost of the thermal battery and often higher maintenance costs because you need someone who understands the system.

[1]: https://www.thisoldhouse.com/ask-this-old-house/21016105/fut...

What I am guessing:

Appliance cost: You can get a $500 normal fridge with 100's of choices or the one $2000 integrated with the home system one that does the same things from a specialist supplier. Then factor in integrated appliances / size of fridge for spot.

Installation cost: In the order of $1000s for parts and labor.

Installation authority: If you are renting, or need building owner permissions (e.g. an apartment) then no chance.

The only people buying this are those "grand designs" type people who are architecting their own house with say $1m build budget and want to be "eco".

> The only people buying this are those "grand designs" type people who are architecting their own house with say $1m build budget and want to be "eco".

Sad but mostly true in the US.

High efficiency appliances are market segmented as luxury goods, therefore mostly purchased by the well off, limiting the energy used reduction impact of the technology.

This is less the case in societies with high energy costs, like Japan or parts of Europe.

Heat pumps are not a new technology - they are air conditioners that can be run in reverse, and in a broader range of conditions.

It’s a luxury good because it’s more expensive than natural gas in the US. Natural gas systems are cheap, easy to work on, and resilient because they can continue working even when the electricity isn’t (especially nice in winter during snow storms).

> because it’s more expensive than natural gas in the US

Assuming the antecedent for "it" is electricity, yes - on a per BTU basis nat gas is cheaper, but the beauty of heat pumps is that they move ambient heat instead of releasing it from chemical bonds, so they cost about the same to operate as nat gas water heaters.

Coupled with solar, their operating coat gets even cheaper.

I agree that they are more expensive to build than a simple nat gas heater, but they also don't need exhaust ventilation ducts. Also, higher efficiency condensing nat gas furnaces are also more expensive, requiring fans to force cooled exhaust gases out of the exhaust.

> easy to work on

This is the reason everyday non green-focused HVAC contractors have given me for why they don't install heat pumps. They and their crews aren't familiar with them.

Natural gas is available to a large fraction of the US population, but not a large fraction of the landmass. Something to keep in mind.

Systems like that are floor radiant heating using pex water tubes embedded beneath the flooring. Geothermal heatpumps circulate water loops into the ground to dump heat in the summer / grab heat in the winter.

> Heat pump water heater systems typically have higher initial costs than conventional storage water heaters. However, they have lower operating costs, which can offset their higher purchase and installation prices.

That's the key problem. Solar cracked this nut with the PPA -- zero upfront costs because the system is financed, you pay your monthly electric bill through the solar company, and they take a cut of the "operational savings" as loan servicing and profit. However, the PPA was an uphill battle -- it took a while for big finance to be comfortable with the long term performance of solar panels before they became comfortable doing this kind of loans. The big solar companies today are the ones who took a bet on making PPA financing possible.

With home efficiency improvements, however, there are so many more variables. Whereas solar is basically the panel and the inverter, with home heating you need to factor in the construction of the home and a million other variables. If the efficiency paybacks are less predictable, it's harder to finance, so it's harder to overcome the higher upfront costs.

Then, when it inevitably breaks, your house is cold, you have no hot water, and all your food is spoiled, all at the same time.

I nominate you as the new Secretary of Food Distribution.

There's one in the Tesla Model Y. Heating and cooling for the cabin, battery, and motors are all handled by a single integrated heat pump system. The part that connects them all together is called the Octovalve.

It's a big advance for electric cars because the cabin heater tends to really reduce range, so making it 3x more efficient with a heat pump instead of a traditional resistive heater makes a huge difference.

Most other electric cars besides Tesla were already using this.

> Why aren't there integrated systems for heating/cooling? (Or maybe this exists and I just don't know the proper terms to search for)

There are some cases where such integration can be achieved through clever design (i.e. a heat pump water heater that dumps cold air on an adjacent warm kitchen), but many times the loads of the heating/cooling use cases don't match up well either in magnitude or timing.

A pool pump is an interesting example where the pool likely has enough thermal mass to absorb the heat from a house via a heat pump, although at some point the pool would likely get too hot after days of repeated heating, since it would hold on to heat longer than the adjacent house, so it would only make more sense in areas with large day/night variations in temperature, like in high deserts.

Japan do have such system though not for export as they're still iterating through at their own pace. Daikin do used to have an Altherma product for sale, but heatpump for heating isn't as nice as gas furnace if you consider the fact that body temp is usually higher than the temperature heatpump outputs at efficient levels.

For example, to heat a room to 70 degrees indoor meant if they can output heat at 75 degrees then it'd be sufficient, unfortunately no one would want to have 75 degrees wind blowing on them in winter. We want something like 150 degrees so it actually feels warm.

That's actually one of the general issues with heatpumps - because they aren't literally lighting something on fire (or using resistive heating which just lights money on fire) they have smaller temperature deltas when designed properly as you mention. This leads to things like oversized air conditioners in hot places because people will cycle the AC creating a high peak demand and if it isn't 'blowing cold' they think it isn't working.

Heat pumps (assuming they can vary their output, which most new ones can) work much better to keep a constant temperature whether hot or cold and actually create a really nice indoor environment if a) designed or sized correctly and 2) have good thermostat placement. There's plenty of software, standards, and guides out there to hit both of those and then you just have to educate the users to set a temperature and then forget about it other than monthly filter cleaning. This is hard coming from 100% or 0% duty cycle systems like most fossil-fuel heat and old-style air conditioners so some think heat pumps are 'wimpy' and don't work. Placement is also part of that - you shouldn't be sitting in the output of the unit (which tend to be lower velocity than forced hot air etc) because the unit should be placed so it can cool the entire space.

>We want something like 150 degrees so it actually feels warm.

The reason why you want the air cooler in the summer and warmer in the winter is to achieve a similar (comfortable) rate of heat loss through your skin. The reason why that feels different even at the same air temperature is due to humidity and radiative heating differences. Your HVAC isn't just heating and cooling you, it's also heating and cooling all of your walls. If your wall temperature varies by 10 degrees between summer and winter, even with the same air temperature, it'll feel different because of the increase or decrease in infrared coming off of the walls. The better insulated and less leaky your house is, the lower that differential will be. If you could run radiative cooling through external walls and ceilings, you would only need a fraction of the typical air movement in a house for ventilation and you would still feel totally comfortable.

We don't need to heat rooms with body temperature ventilation, we just need to keep a comfortable rate of heat loss for human occupants. That's dependent on radiative heat, air temperature, humidity, and air velocity.

You'd probably need a large house and a small pool in Florida for that to be the case.

Pools are typically uninsulated and also experience a decent amount of evaporative cooling. It is not uncommon for swimming pools to have heaters with double the output capacity of the furnace in the home they're attached to.

>>Why aren't there integrated systems for heating/cooling?

See Mitsubishi's Mr Slim line. They need to do a better job promoting it, but it is amazing.

>Why aren't there integrated systems for heating/cooling

Geothermal heat pumps do that.

Why not do it like the commies and heat your entire city? ;-)

https://en.wikipedia.org/wiki/District_heating

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