What are some realistic solutions to Blockchain’s energy consumption challenges?

To be technically correct, it is not blockchain per se that consumes the energy, it is the mining rigs. Mining is basically verifying transactions and adding the block of transactions to the chain. As background, there are 3 different types of blockchains, public (think Bitcoin), private and hybrid. More on that in a minute.

Private and hybrid networks do not need this type of mining because access is based upon authorization and the nodes doing verification can be “trusted” and the computations are rather quick. This type of network would be used for private businesses etc.

In the currency world again, there is another concept called proof of stake. The Ethereum chain was intended to go this route, not sure if they have yet or not, but the concept is this. Based upon how much of the currency you own, you have a weighted chance of being selected to solve a block. If you solve it correctly, you get paid, if you try and falsify it or do something nefarious, you loose ALL of your stake. That is you loose every dime of value you have in Ether. Keeps things honest, but also uses a ton less power because the cryptography is less challenging and everyone is not churning to solve the same problem.