I used regular electricity but it could be solar powered very easily. The only electricity used is a small pump so one solar panel, battery, and inverter would do the trick. You could even use a dc pump and not need an inverter.

Plus, you don't need to be in the tropics. Tilapia are very hardy fish and as long as the water doesn't freeze it would work. I visited a commercial aquaponics farm in Washington State near Seattle where they kept the fish in a greenhouse and it worked fine. But you do need plants growing at all times for it to work unless you had another filter system for winter. If at any time the plants stop growing the fish would die without a backup filter.