>> do You have any other energy sources available to use? compressed air for
>> example.
>
>Not really available. I've thought about hydraulics or pneumatics, but I'd
>need to generate the pressure. May be viable; I don't know how much this
>would add to the overall cost and system complexity. Has anybody any good
>pointers to pumps (and cylinders, and ...) for such an application? I tend
>more towards hydraulics; seems smaller, quieter and easier to deal with.

My Volkswagen Golf uses a pneumatic drive for the central locking on the
passenger doors. It takes a moment or two for the pump motor to start, and
then the locks go. Gives them a nice slow actuation compared to solenoid
actuated ones.

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