Quote from: cryptoassistent on July 01, 2018, 08:18:03 PM

there is at least one coin using proof of storage instead of proof of work.

This algo is not linked to the wealth of the miner so it seems to be well thought economically.

Storage is less expensive then processing power.

Why no billion coin use it?

it depends on developers need to implement successful project usually different coins integrate different algo\s as well as (POW , POStor & POStake) also I think the famous one used heavily is POS (Proof of stake ) - my favorite .
Link below show some technical points :
https://siawiki.tech/about/pow_vs_pos

perhaps in near future we can see new invented ALGOs different and effective than all above . innovation will not stop because of electrical consumption or economical thought .