It's immpossible to trade steem power, steem power is made just to make your upvote worthy. And when you will have a big steem power you can power down in the future and earn from that. I advice you to save your steem power and keep earning steem dollar to trade in the future. The methode I am talking about in the post is not for little amount, I did write at least 10 steem dollars you have to have to start doing that !