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by slow_typist 828 days ago
The monetary case of PV does not account for the damage that is done to the environment over the entire lifecycle. Solar hot water panels are ecologically superior. Not only are they more efficient in W/sqm. Their production is not as energy intensive (plumbing included), the recycling process is less complex, poisonous materials can mostly be avoided. If heat is the desired product, they probably beat PV by an order of magnitude in the energetic dimension.
2 comments
Retric 828 days ago
PV’s falling prices have also been associated with falling environmental harm. When you’re talking multiple orders of magnitude you just cannot require as much in production.

IE: You can’t burn 500 gallons of gas if the end product costs 500$. That applies not just to transportation but also how much material and thus mining the raw materials you need, including refining them, the amount of chemicals you can use per panel, how much electricity you can use in production of the device including precursors etc.

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slow_typist 827 days ago
The argument is valid, if energy is not subsidised. However, burning pv for resistance heating is still wasteful and should be avoided. It is only acceptable for peak production that cannot be put to better use.
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Retric 827 days ago
It’s wasteful of electricity not necessarily resources.

One of the numbers I was looking at compared air sourced heat pump at night when it’s coldest vs this kind of resistive heat battery. Solar panels are far cheaper and better for the environment on a kWh/day basis so even if the COP is 3 (or less it gets colder at night) * 90%(losses from battery) = fewer panels you more than offset it by needing far more batteries.

Obviously solar thermal setups have advantages if you need lots of heat, but they are also wasted most of the year. If 8-10 months a year you’re only using them for hot water then annual efficiency is closer to 25% than 90%.

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adrianN 828 days ago
You can run a heat pump with the electricity. That changed the calculation a bit.
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slow_typist 827 days ago
Sure but a heat pump was not the scenario in the parent post.
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