How much energy is needed to melt one cubic meter of ice at 0 degrees Celsius? (No further heating after fully melted.)
It is not possible to melt one cubic meter of ice at 0 degrees Celsius since the temperature is required for the process to take place. Temperature will trigger the melting process of the ice at given rate.
It would be just the energy needed to change the state from a solid to a liquid. This sounds like a theoretical problem rather than a practical one.