Principle of conservation of energy?

Question

A crane uses a petrol engine to lift a heavy girder. What is the overall energy conversion in the system when the girder is moving at a steady rate? Explain.

Answer 1

Chemical energy in petrol fuel is converted to heat energy by mixing with air and burning.  Heat is utilized and converted into mechanical (kinetic energy) to lift girder (though not all some remains as heat).  As girder is lifted, kinetic energy is transferred and converted to potential energy with the girder.  

Answer 2

crane is burning fuel, consuming energy, lifting the girder.

potential energy is being added to the girder as it goes higher.