the cryptocurrency is not only extremely expensive in terms of its mining costs, but also inefficient in its long-run design. However, the efficiency of the Bitcoin system can be significantly improved by optimizing the rate of coin creation and minimizing transaction fees. Another potential improvement is to eliminate inefficient mining activities by changing the consensus protocol altogether. So there is the possibility of replacing PoW by a proof-of-stake (PoS) protocol which can strictly dominate
PoW and even support immediate and final settlement. There are many fundamental issues of a PoS protocol still need to be sorted out and remains much to be learned about the economic potential and the efficient, economic design of blockchain technology.