So I would like to add a possibility: if the necessary energy to move the mining activity was supplied *for free*, could btc transactions be executed for free as well? As the world is evolving, renewable sources of energy are becoming even more popular and sustainable (taking our daily needs in consideration). Elon Musk's Tesla has already made a 100mw battery, and the conclusion is that it's paid back in 20 months, an incredible economy compared to the expensive electricity we use yet.
Now think if a solar energy farm with a battery like that were used to create bitcoin transactions. It's an infinite and free source or energy, right? At least after the investment is paid back. My doubt is how miners could return the fees to the transaction senders in this case. Would it be possible? Would you like to add any thoughts?
If there was free electricity, miners would still need some incentives for working, right? Sure, they are mining and getting block rewards for now. But as less and less BTC is left, the bigger and bigger stake of the rewards come from transaction fees. What I am saying is that it's probably not a long-term solution anyway. All of the bitcoins will be mined by the middle of the next century. Yet someone will have to still validate the transactions, right? And they won't want to work for free, of course. Oh, and apart from investing time and perhaps paying salaries miners also need to cover the costs of their equipment, not just electricity. Once we solve the electricity and equipment costs problems, Bitcoins will be mined or very closed to be mined, and incentives for confirmations of transaction fees will be needed more than ever.