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0 pointsthsksbd2y ago0 comments

PV can beat solar thermal once a heat pump is used.

However that ignores the externalities of PV and heat pumps manufacture, replacement and disposal so I think the argument is BS.

Solar thermal is an aimed aluminum trough and a stainless steel pipe painted black on its focal point.

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5 comments · 1 top-level

154573452342y ago· 4 in thread

> Solar thermal is an aimed aluminum trough and a stainless steel pipe painted black on its focal point.

No, it's actually these fairly sophisticated phase-change evacuated tubes that have a heatsink at one end immersed in the water, from what I remember reading.

BoiledCabbage2y ago

It sounds like you're talking about an "air to water" heat pump. Or some other source to water heat pump.

Phase changes, and pressurized tubes screams heat pump to me. This is different than solar thermal which is essentially leaving a bottle of water sitting in your car on a sunny day. Nothing more complex needed.

PaulDavisThe1st2y ago

There are two kinds of water-heating systems based on heat-pump related ideas.

One circulates a non-water liquid between the panels and the hot water storage tank, and it exchanges heat obtained from the panel with the water in the tank. This has the downside of being complex (pumps, weird liquids etc.), but has the upside of keeping the fluid system associated with the panels distinct, which can reduce issues with freezing and can boost efficiency.

The other system doesn't use thermal panels at all, but just uses electricity to drive an air-source heat pump that exchanges with the storage tank.

mlyle2y ago

It can be either. There's fancy thermosiphons, etc, but you can also just preheat water going into a water heater by pretty dumb means. You can run circulating pumps. You can have a separate working loop. Etc, etc, etc.

The Carter panels were pretty simple boxes with pipes and water circulated through them, I think.

thsksbdOP2y ago

Evacuated tube? Like the heat pipes on you CPU? Sure, but completely unnecessary unless you want to get rid of the pump [1]. And why get rid of the pump to substitute it with an evacuated tube?

[1] which you don't even need if you route the system well or use valves.

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