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Inside the thermodynamic cycle

Inside the thermodynamic cycle

ROBUR units operate thanks to the absorption cycle which is a different way to produce heating and cooling if compared to the electric heat pumps.

ROBUR Gas Absorption Heat Pumps (GAHP) are natural gas fired and they do not need any mechanical device (like compressor) to operate. The result is a minor electric consumption and high reliability other than the possibility to recover much more renewable energy from the environment.

In addition, gas absorption heat pumps do not use any harmful refrigerant because the water-ammonia solution that fills the system is totally natural and green.

If compared to the electric heat pumps which operate thanks to the well-known Carnot cycle, the thermo dynamical cycle of the Gas Absorption Heat Pumps has some important differences which make this technology unique and attractive.

Here below a picture showing the major components used in the ROBUR Reversible Gas Absorption Heat Pump (GAHP-AR), a model that can provide heating or cooling alternatively.


  1. Burner. The combustion of the natural gas (or LPG) starts the “chemical engine” of the absorption cycle.
  2. Generator. Thanks to the thermal input of the burner, ammonia evaporates and parts from the water.
  3. Levelling chamber. The vapour of ammonia is dried up. Condensate water goes back to the generator.
  4. Reversing valve. To reverse the cycle from heating to cooling mode and vice versa.
  5. Ammonia-water heat exchanger. Condenser absorber in heating mode, evaporator in cooling mode. It is where the heating or cooling energy is transferred to the water of the hydraulic loop.
  6. Pipe in pipe heat exchanger. Used to boost the efficiency of the cycle thanks to an internal energy exchange between hot liquid ammonia (from the condenser) and cold vapour of ammonia (from the evaporator).
  7. Pre-absorber. It is where the absorption process starts. Vapour of ammonia coming from the evaporator is absorbed into the water coming from the generator. The energy produced by absorption process pre heats the solution that goes back to the generator and dramatically increases the efficiency of the system. This process is completed into the condenser absorber.
  8. Fin coil. Air heat exchanger. Condenser absorber in cooling mode, evaporator in heating mode when renewable free energy is recovered from the outdoor air.
  9. Solution pump. The water-ammonia solution is pumped back into generator.
  10. Defrosting valve. When required during the cold season, hot ammonia vapour is by-passed into the fin coil to melt the ice layer.