Nice idea but the implicit comparison with solar power is misleading. 1 kW of power corresponds to generation of 1kj of energy per second, which is enough to lift 10kg by 1 metre - every second! A single kWh of energy, costing 30c or so, would lift a 36t weight by 1 metre; so a single 1 kW panel producing a meager 5 kWh of energy in one day would achieve feat this 5 times over. Which puts this so called "food-power" into perspective, and also explains why gravitational storage of energy has never made much sense.
I'm sure this device does have its applications; but it does the same the same job as a toy solar light, with a small panel, a small battery and an LED - a device worth a few dollars, and having no moving parts to maintain.