Electric power is one option as already discussed. Besides batteries, super-capacitors (e.g, 1F caps) are commonly used to supply power. The obstacles to solar power are just too great for most modelers.
Other options for portable power include compressed gases, particularly carbon dioxide, and rubber bands. Rubber bands may sound old fashioned, but I believe the world record for indoor flight with them is on the order of an hour or more. Of course, for such performance, the entire model weights only a few grams and uses exotic materials for the structure.
This being an electronics forum, however, the OP may want to consider the alternative of capacitors for powering an electric model. John
Other options for portable power include compressed gases, particularly carbon dioxide, and rubber bands. Rubber bands may sound old fashioned, but I believe the world record for indoor flight with them is on the order of an hour or more. Of course, for such performance, the entire model weights only a few grams and uses exotic materials for the structure.
This being an electronics forum, however, the OP may want to consider the alternative of capacitors for powering an electric model. John