With today's technology: Is it an esoteric or realistic??

With today's technology: Is it an esoteric or realistic, conversion of 4 kWh, thermal to a 0.5kW mechanical motion?? If is realistic, Why are we waiting for halving the energy bill, in large equipment's.

Considering that 1 kWh consumed by compressor generates (approximately), 4 kWh. temperature rise in the condenser, then 3 kWh. temperature drop in the evaporator.

The adoption of this project may lead to energy independence with air conditioning, in the most important periods of its uses.