Computational Physics or Engineering Physics, which deal with new technologies related to energy?
If you want a hands-on approach then Engineering Physics seems like the logical option, if, however, you want to think about the problems on a more abstract level, Computational Physics seems like the right choice. 

Since you are doing Computer Science, you probably love, as many of us do, the power of coding languages, and might feel more comfortable using these to solve problems, once again that would mean computational physics might be more your thing.

The real question is how you want to deal with these new technologies. If you want to really work with these new technologies, I'd opt for engineering physics. You might want to take a look at some of the courses in these master programs and see which suit you more, or you could engage with master students of these courses to get a better insight in the course.