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Comment by bilsbie | Hacker News Reader

I’d love for someone to make a portable standalone heat pump for a swimming pool.

Why not make it solar powered with fold out panels. With 400% efficiency 1500 watts of solar power could get you 6000 watts of heating.

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These exist. I am on the fence about buying the $600 one for experimentation and repurposing it to heat/cool garage. Many have heat/cool functionality. You can put the air side either inside or outside.

https://www.amazon.com/s?k=pool+heat+pump&crid=1LWMIT8JDL7S8...

My idea is to do some ground source heat pump supplemented by solar thermal water heating to get lots of free BTUs. The issue (for the $600 one) is it can only cool the water down to 46F. Recall that cooling water means heating air (inside). But heating water goes down to I think 23F. Decisions will have to be made.

I would love for this to take off, solar panel installation alongside GHCP. Since this is probably for a single family residence, toss in a battery and an electric vehicle charging interface - bob's your uncle.

Do you get sun? Putting some black-painted tubing (exposed to the sun) inline with the pool filter pump provides quite a lot of heat at only the cost of the materials. The filter pump already exists and is already circulating pool water :)

Why buy a large and expensive PV array at 15% efficiency to run a complex heat pump when you could instead use the sun’s thermal energy directly in a solar water heater at 70% efficiency?

That's what I was going to comment (although it's closer to 30% than 15% these days), It's low tech and a fraction of the cost, for a swimming pool all you need is a pump and some black pipes really

That probably flips the balance from "use solar thermal" to "use PV and heat pumps", especially in any environment where indoor cooling is simultaneously needed (which is a common case).

If solar PV is 25% efficient and the heat pump CoP is then 4.0, you get a gross efficiency of 100% (plus "pre-paid" air conditioning).

It depends on what you want to do with the heat pump. That solar water heater will not help you much when you want to cool your house in summer.

BTW, I am not sure why exverbody is exited about "heat pumps", which are just air conditionings that have been in use in Asia for decades and probably been installed a billion times

Even better, have the cooling end of the pump be in your house. Cool your house while heating your pool

There are existing systems today that do this for residential pools.

It’s not uncommon for efficient commercial buildings like corporate headquarters to have a retention pond be the heat sink for their chillers in the summer. They’re building a pond for aesthetics anyway, so if it’s large enough this can be cost effective vs. digging geothermal wells.

There's a hospital near me built about 15 years ago that has a huge (10 acres?) and deep pond for exactly this. If you hadn't seen it being built, it would look just like a normal decorative pond.

Back when I worked at Goldman, I was told that either their HQ or their Jersey City tower over by the Statue of Liberty had a huge water thermal mass in the basement. They took advantage of cheaper electricity at night to use heat pumps to push the thermal mass whichever way they needed it to go for the next day's heating/cooling needs.

For heating e.g. a swimming pool a solar heater would be more efficient.

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