I doubt even 15% efficiency would be there; along with massive maintenance/size issues. Solar is cheap and easy when it comes to maintenance, effectively no mov

I doubt even 15% efficiency would be there; along with massive maintenance/size issues. Solar is cheap and easy when it comes to maintenance, effectively no moving parts. Internal combustion (or a gas turbine) is a whole new development... and there is the storage. The best bet are still batteries, albeit the current incarnation of LiXXX (e.g. LiFePO4) are still not there. Even storing energy in batteries poses multiple conversions of electricity that goes to 92-95% efficiency.