Which activity can occur without the use of energy?

To be honest... I don't think there's an activity that doesn't use energy because everything around us uses energy. Even if you laying down not doing anything your heart is still pumping, glucose is being broken down into food to make energy so... no I don't think there's any activity that doesn't need the use of energy.

Firstly, the water in the dams hold gravitational potential energy as they are above ground level. the gravitational potential energy is then transferred to kinetic energy as it falls, spinning the turbinethe turbine then spins the generator, which is a large magnet surrounded by metal coils. by doing this, the generator generates electricity. in this action, the energy transfer taken place is kinetic to electric energy