while lord dynamo's power-sucking zeppelin may have been able to absorb enormous quantities of energy [ie. the collective energies of alan scott, starman, and thunderbolt] dynamo himself was unable to absorb any energy on his own.
it was normal equipment - and it was more than capable of absorbing vulcan's energies. however, it was still only that... a blimp.
furthermore, it wasn't even capable of absorbing energy unless it was, more or less, right on top of the source. that said, it would be rather easy for vulcan to avoid dynamo's blimp, and destroy it with a long range attack.