That's a cool video, but a custom 500W water-cooled setup does indeed strike me as "quite difficult" for your average person. It seems that the LED in the video is the $500 YujiLEDs BC270H, which is 20,000 lumens. In other words, to match midday sun at ~120k lux, for a small room of 100 sq ft /~10 m2, where all light fell directly onto you/the floor and none on the walls, you would need 1.2 million lumens, or _sixty_ of the setups in the video, or about 30 kW continuous ignoring all cooling needs and other losses.
I completely believe him when he says that it feels like sunlight (it's a high-quality, high-CRI, extremely bright light source at infinity!) but us humans are very bad at determining brightness levels. An iPhone flashlight in your face is unpleasantly bright and yet it is a completely insignificant amount of light on an absolute scale. We humans perceive brightness on a sort of relative log scale.
The steelman argument - where someone does indeed build one 500W water-cooled setup with large dish etc - and all of this light falls into a small corner of 2m x 2m - is still only ~5000 lux, roughly an overcast day. To even get to the level of standing in the shade on a clear day - 20k lux - for a regular room, you would need an obscenely powerful setup.
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The natural response to my comment, of course, is that "well, maybe they don't need those high levels!" The problem is that all of the research indicates that they do. You mention research on Taiwan, which I think is a perfect example. They already did try to brighten the indoors to prevent myopia - minimum government standard of 500 lux starting with a 1999 standard [1], and in many cases brighter than that. You say that they need a 1000 lux environment, which isn't much different than the current Taiwanese indoors. I, on the other hand, say they need a ~100k lux environment, which is orders of magnitude more light. The research agrees with me: it was not the 500 lux standard, but the later introduction of two hours outdoors daily that improved myopia rates [1,2.]
Mind you, this is two hours outdoors during school hours in Taiwan, which is near the Tropic of Cancer (think Mexico, Caribbean, North Africa) and thus has far sunnier winters (Taiwanese peak summer sun is 1.9x winter sun vs 4.2x in Boston, 3.7x in NYC, 10x in London [4]) despite total solar irradiation being similar to Western cities [3.]
I completely believe him when he says that it feels like sunlight (it's a high-quality, high-CRI, extremely bright light source at infinity!) but us humans are very bad at determining brightness levels. An iPhone flashlight in your face is unpleasantly bright and yet it is a completely insignificant amount of light on an absolute scale. We humans perceive brightness on a sort of relative log scale.
The steelman argument - where someone does indeed build one 500W water-cooled setup with large dish etc - and all of this light falls into a small corner of 2m x 2m - is still only ~5000 lux, roughly an overcast day. To even get to the level of standing in the shade on a clear day - 20k lux - for a regular room, you would need an obscenely powerful setup.
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The natural response to my comment, of course, is that "well, maybe they don't need those high levels!" The problem is that all of the research indicates that they do. You mention research on Taiwan, which I think is a perfect example. They already did try to brighten the indoors to prevent myopia - minimum government standard of 500 lux starting with a 1999 standard [1], and in many cases brighter than that. You say that they need a 1000 lux environment, which isn't much different than the current Taiwanese indoors. I, on the other hand, say they need a ~100k lux environment, which is orders of magnitude more light. The research agrees with me: it was not the 500 lux standard, but the later introduction of two hours outdoors daily that improved myopia rates [1,2.]
Mind you, this is two hours outdoors during school hours in Taiwan, which is near the Tropic of Cancer (think Mexico, Caribbean, North Africa) and thus has far sunnier winters (Taiwanese peak summer sun is 1.9x winter sun vs 4.2x in Boston, 3.7x in NYC, 10x in London [4]) despite total solar irradiation being similar to Western cities [3.]
[1] https://www.sciencedirect.com/science/article/pii/S016164202...
[2] https://pubmed.ncbi.nlm.nih.gov/34425129/
[3] https://solargis.com/resources/free-maps-and-gis-data?locali...
[4] https://weatherspark.com/y/137170/Average-Weather-in-Taipei-...