The creator of the BitTorrent protocol Bram Cohen published a new concept of mining called Proof-of-Space. The new method is an environmentally friendly alternative to the energy-intensive Proof-of-Work method, which is used in the Bitcoin network.
The document "Beyond Hellman's Time-Memory Trade-Offs with Applications to Proofs of Space" describes the process of mining using the computer's disk space, rather than its computing power.
With this approach, the probability of mining a block is proportional to the sum of the allocated space divided by the total network capacity. This method, according to the authors, will be more environmentally friendly than Proof of Work, and more profitable.
At the moment, however, it remains unclear whether this concept will form the basis of any new digital currency. In April, Bram Cohen announced the creation of a new cryptocurrency, based on the Proof-of-Capacity algorithm, which is also based on the principle of using free disk space. Since then, nothing has been heard about the project, however.
Proofs of space (PoS) were suggested as more ecological and economical alternative to proofs of work, which are currently used in blockchain designs like Bitcoin. The existing PoS are based on rather sophisticated graph pebbling lower bounds. Much simpler and in several aspects more efficient schemes based on inverting random functions have been suggested, but they don’t give meaningful security guarantees due to existing time-memory trade-offs.
You can learn more in the whitepaper.