You'll learn a bit on hardware architectures in elec. Mainly RISC architecture.
With elec, there's a lot more involved in that. If you really want to be involved in biomed or renewable, then it would be a decent idea to consider studying in those areas. UNSW offers dual programs with masters in biomed.
If you study elec, you'll end up studying quite a few things in general. It will involve a lot of circuit theory, electronics design, basics of signal processing, control systems, electromagnetics, embedded systems, energy systems and could even learn about other stuff as well (depends on your electives in later years). What you learn in these is definitely applicable to renewable energy systems and biomedical equipment design, which can also lead you to a career in those fields, however you'll have to learn a lot of other stuff in elec in general which you also need to consider here. If you are certain that you want to go into renewable energy systems, then it may be worth looking into that. In the end, it's up to you.
Also, elec is very heavy on maths, so expect to be applying mathematical skills throughout all of uni.