That link is for Piefed.world; run by the same team that run Lemmy.world
There are other piefed servers which may have different email requirements. But the most likely reason Piefed.world requires real emails is to prevent bots making fake accounts and also reduce the risk of bad actors making numerous accounts to avoid bans. As it’s hard to get multiple real emails it makes it hard to make multiple anonymous accounts which is unfortunately a tactic of trolls.
You can of course create a dedicated “private” email account on an official service and use that to sign up if you’re worried about sharing your primary email account. A lot of people do this online to have a legitimate email but essentially in it’s own silo separate from other personal emails.
Maybe I’m misunderstanding but wouldn’t diffuse light be what it’s going to be best at? While it’d be worse on a sunny day when there is an optimal single direction for the light to come in?
It’s the opposite of a light house fresnel lens - instead of scattering the light source evenly out, it’ll capture diffuse incoming rays from random directions better and concentrate it on the photovoltaic cell? However it would be at the cost of being able to capture direct sunlight efficiently as only some of the lens would ever be in the best position to capture the direct rays?