If theres no electricity? There are some alternative to have a power supply it can be with generator, solar panel or powerbank. More importantly you have a internet connection so you can trade. Thats two important factor(internet connection and electricity) so you can have transactions to others.
I do not even understand the reason why the OP would be asking that question in the first place since he already knows the answer to it. Let's even leave BTC aside, how will he ever be able to even trade anything, including Forex, stocks or whatsoever. As long as the digital age is concerned, if you do not have electricity and no internet access, then such a person is still living in the old age.
In case there remains no electricity in this world, then it will not be only trading of crypto currencies which will get affected by this. In fact there will be number of other things as well which will suffer in case we dont have electricity. Without electricity, we cannot even think of doing anything with any of our crypto coin as it is not possible to buy or sell any coin without internet and electricity.
I cannot even imagine a day without electricity and from all the things I see in the news, I wonder how some of the people without electricity cope in this present age when everything has gone digital. There is no asking too much question or giving a lot of answers to this, no electricity, then nothing! It is more like trying to go to erect a building without tools, how is that possible?