Air Conditioning isn't free... but we're close.
Tech Ingredients1 HN recommender · recommended in 1 month, 2023–2025
tutorial · general · evergreen · 2023–2025 on HN
Tech Ingredients shows how to build a liquid panel with a specialty paint that, placed outside, cools below ambient air temperature. It demonstrates radiative sky cooling.
HN points to it in threads on radiative cooling as a hands-on explanation of passive daytime cooling.
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4 comments from Hacker News
It's a thing in from thousands of years ago link and today link for PDRC there are a couple good videos about it from NightHawkInLight link , link and Tech Ingredients ▶ this video link
That problem can be solved by adding a mirrored ring around the cooling surface, so it can only "see" the sky: ▶ this video
There is a detailed example of this uploaded a few months ago here ▶ this video [In fact, I just noticed the author of the OP video posted on this one]
>Only active cooling can cool anything below the ambient temperature. Not exactly: link Couple of videos explaining the effect link ▶ this video