Does anyone know how much power an electically operated door locking mechanism uses? I assume it would use either uses a solenoid or motor driven screw system, either way even with indicators etc I doubt it would be much in excess of 100W or so per door. Probably beyond the capability of carriage lighting batteries but not going to require more than say 5kVA for the whole train, double that for contingency/reliability, 10kVA.
There are plenty of small acoustically shielded generators available at that capacity, size wise including casing maybe 1.2m x .8m x .8m, our local 'burger van' uses one, its towable by a small car, at a guess maybe 300kg +-. That could be fitted in the guards compartment of a normal carriage. Skid mounted to allow easy swap out, with connectors for the power cable. The only non standard bit would probably be the exhaust. Its not like the requirement is for 100kVA+ as would be required for full ETH.
Engineering wise I would go for a small motor driven screw system, it only uses power when actually operating (i.e. locking or unlocking), I have recently designed one much larger to secure a shielding door which weighs in excess 10t and that used a 192W motor, the lock/unlock time is in the order of 6 secs, and once locked is passively safe. Emergency locking/unlocking is provided by means of a removable hand crank key similar to a gigantic clockwork key. The majority of the components were 'off the shelf', including the electrical controls, with just some machining for the bolt mechanism. The level of safety required for this is probably similar to that required for a railway application.
Because they only draw power when operating apart from control and indicator circuits, I would estimate lets say 100 operations during a 12 hour period, thats 600 secs, at say 100W, thats only 16Wh plus say 6W for indication and control continuous draw, another 72Wh, say 100Wh total, double that for contingency, 200Wh, that would be a 10Ah 24v battery per door, which could probably locally mounted and removed for charging, 3 sets of batteries, 1 on the train, one on charge, and one back up, rotated around. Use off the shelf batteries, there are plenty available, maybe even a power tool battery, which are available in these sort of capacities.
My point, there are solutions to the problem but I sense an 'we have always done it this way' attitude and a overly complex system for getting things approved. We have to work within a strict regulatory system, obviously not the rail one, but there are accepted techniques for validating safety and as long as these are followed acceptance is fairly straightforwards.
