Nuclear Fusion

[FindernRam]

Apparently the whole world contains 800kg of tritium (Nature Journal) Some is replaced every year by Cosmic rays ,but it has a very short half life. 

Now that makes a pretty small sun and you have to extract it from the totality of the sea. Using who knows how much energy to do so. I'm not against trying, but in my view this is not exactly a low hanging fruit. Probably many decades away. I'd rather spend the money on stuff with better returns on investment and quicker delivery times!