You can't save energy in bitcoin, because proof-of-waste is intrinsic to it's functioning and the difficulty adjusts to keep it that way.
(I mean, if I wrote it it would probably take several hundred machines but I'm sure Satoshi or some other brilliant programmer could fit it on a single machine. It only processes what, 5 transactions per second? My first dumb cellphone might be able to do that many signatures per second if someone could figure out how to compile the relevant libraries to run on it.)