You can do that, It would not be as efficient as in converting that same fuel to a gas and powering a combustion engine generator however. I think it would require 1.5 times as much wood to produce the same amount of electricity using steam power as wood gas for example. Or said another way using the same amount of wood you would get 2/3s the power from steam as from wood gas combustion. That’s a crude estimate by the way.
This problem wouldn’t stop me from doing it though. I have seen kits for twin piston steam engines on the net that run on 25 psi.. $200 roughly.