It's literally virtue signaling. They're reducing quality in a highly inefficient way because it's more conspicuous than doing it the sensible way (compressing their highly wasteful PNG images as JPEG). You can compress the images to smaller than their dithered images with perfectly acceptable quality (and it wouldn't surprise me if it used less energy to decode too, because JPEG decoders are so heavily optimized). But if they did that nobody would be able to see how "eco-friendly" they were.
This is only speculation, and I did not mean to suggest it is absolute fact. It's also possible they sincerely believe their dithered version produces better visual results for the ecological cost, and because "better visual results" is subjective this is not necessarily unreasonable.
I don't think true, and the other part is also pretty far fetched.
But the folks who run that website are the real deal and not "virtue signalers." They're running experiments and creating great content, not trying to get some social currency you hypothesize.
If you'd can demonstrate data suggesting a better encoding, they'll redo the pictures. They optimized for size.
Dithered images: total 284K (but it's only showing 9 images, not the full 11)
Small images, resized from the big source images using Imagemagick's -distort resize (default settings) operator to 16bit per channel PNG, then encoded to JPEG with mozjpeg -quality 70 and default settings: 273K with all 11 images, or only 236K if I make it a fair comparison by deleting the two that are missing from the dithered version.
There are visible artifacts, but nothing I'd call intolerable. Filesize is significantly smaller than the dithered versions, it's full color, and it preserves details destroyed by the dithering (e.g. the support wires in https://solar.lowtechmagazine.com/dithers/wood-turbines-nepa... ). The dithered versions are sharper, but the website throws away that advantage by resizing them with the browser's default resizing. I think most people would call the re-encoded JPEG versions higher quality than the dithered versions.
What can we do about the noise pollution? Last time I was around a windmill the bigger one made an annoying woosh-whop noise and the small ones an annoying high pitched noise. Fixing the noise will help getting them accepted in more urban areas.
The noise mainly comes from the tip of the rotor blade [1]. Reducing the noise from these tips is an active research topic and some progress is established [2]. However, it seems difficult to maintain high efficiency when attempting to reduce the noise levels. In any case, scientists and engineers are trying to tackle it!
