An engineer designs a solar-powered irrigation system. The system captures solar radiation using photovoltaic panels, which then power an electric pump motor to lift water into a reservoir. The total solar energy input to the system is 500 J500\text{ J}500 J each second.
The Sankey diagram shows how this energy is distributed.
State the relationship between efficiency, useful energy output, and total energy input.
Identify the main form of energy wasted in the pump motor.
Calculate the overall efficiency of the system from the initial solar energy input to the useful gravitational potential energy of the water. Give your answer as a decimal or percentage.
