[JRaef]

I don't know what the application is, but this could be a designed as "DC backup"? E.g., a lot of circuit breakers have capacitive trip as well as DC source, so you end up with double redundancy.

I think that's exactly what it is. On a head gate going into a penstock (pipe feeding water into a hydro generator), you must have redundant systems that will maintain control of the gate at all times. So if the generator trips for some reason and you have to stop the water from spinning it, or the penstock bursts somewhere and you have to stop the flood or washout, but the DC power has failed, the back-up plan is this stored energy system dedicated to that one solenoid. It pulses the solenoid, which sets in motion a hydraulic operated gate valve that shuts off the water flow. It's a backup for the backup and it's a one-shot operation, but it can mean a lot in an emergency.

 

[JRaef]

Just a weird design. Every system I've seen is a spring-opened valves held electrically closed. Makes it fail-safe instead of relying on DC.

We're talking BIG valves here.