This is tall pyramid made of concrete blocks, in a desert. If you look at it from above, you see there there is a path of conveyor belts that goes from the bottom of the pyramid to the top. This conveyor belt is powered by solar modules, that are arranged on the top the piramid, filling the space that is left from the belts, and on its laterals of the pyramid.

On the top of the pyramid, in the end of the conveyor belt track, there is a hole that falls all the way down to the first level. In this central tunnel, there is a turbine attached to a motor shaft, that realizes some industrial work.

The conveyor belts transports sand, an easy material to come by in a desert, all the way to the top of the pyramid, where it falls and rotates the turbine on impact. When the sand falls down, it is sent back into the conveyor belt in a closed loop.

The idea is to generate energy to power any industrial process.

What is the problem with this idea? 

If you have solar energy already, why not power an electrical motor directly?