Fourth grade science homework: Invent a new form of energy

Robin's is hamster powered, but she insists that they are either to invent something completely new, or combine two existing forms of energy in a new way. Therefore, the kinetic energy of thousands of hamsters running on wheels is, on its own, inadmissible. She wants to use the movement of the wheels to generate friction and thereby heat, and use the heat as her energy source.

I simply can't endorse it. So inefficient.