I think I would buy an uninhabited island and make it a research facility where top scientists can work together and find a way to optimize solar power and batteries.

If I have those I will start a production company that makes those inventions and sells them at the price (or below) it costs to make the goods so everyone can use them. I would also invest in agriculture in dry area's (africa for example). What I would NOT do is waste it on politics, that's why I want the uninhabited island. If you build a facility/production company with that goal there will be government regulations about it and as most of us know, they tend to screw things up and only care for their wallet.

Also a part of that money will go to education and proper sports centers. I'm a bit overweight myself and I want people to know better then always go to McDonalds and have the option to do any sport they like, as it should be.