you didnt say no mods so try using something that detects that theres no power in the solar generator to make it day and if its full power then it becomes night and so at day it charges and night it send the power mods needes: extra utilities, any mod that can take the power out of them like applied energistics 2 and yes its possible i did it and its hard to do unless you do it without pistons this might make sense lol

Moving theme park rides with command bocks.

I'm having trouble building functional Weeping Angels, if you want to try that.

An adventure map would be a big project, and you could put to test redstone timers connected to dispensers and command blocks, or you could build a mansion, where everything is automatic (who wants to get up and walk to the dispenser that gives you food? The /give command in a command block is much better!), and all sorts of things in that mansion.
Get creative! Everytime you walk in the room your clothing (armour) is put onto the armour stand for you using a dispenser! Your fish is put into your aquarium using a dispenser, and everytime it despawns a new one comes in using a complex timer! There are no limits.

Good luck!

a clothing machine that allows a player to select what pant, shoes, chest plate, and helmet using buttons. Then, the player stands in a booth, the machine the detects that the player is there and the armor is placed onto the player. use as many armor types as possible and a reset button