Gas absorption heat pumps are heat pumps that are powered not by electricity, but by natural gas. They are a symbiotic combination of gas boiler and air or brine sourced heat pump. The gas absorption principle was actually invented 1858 by Ferdinand Carré, a French engineer, and has been used ever since in all kinds of applications including heating and cooling offices and industrial facilities as well as camping refrigerators and hotel refrigerators, for example.

Gas absorption heat pumps use a refrigerant (e.g. ammonia)-water absorption cycle to provide heating and cooling. That means:

1. Evaporator:

Environmental heat is transferred to the liquid ammonia, which than becomes gaseous and now contains the free of charge energy. At the liquid stage, refrigerants like ammonia can be charged with environmental energy the most.

2. Absorber:

The gaseous ammonia is absorbed by water and creates a so called “solution”. A pump can now generate a high pressure level with little effort and drive the solution to the next step, the generator

3. Generator:

A gas burner lifts the pressurized solution to a constant and useful temperature of up to 70°C for the heating system. The temperature also separates ammonia and water again. The water flows back to the absorber and becomes charged with energy-loaded ammonia again. The remaining gaseous and high temperate ammonia in the generator is what is used in the next and final step.

4. Condenser:

The full energy at its high temperature of the pure and gaseous ammonia is now supplied to the heating system (radiators). Releasing the energy to the heating system, the ammonia cools down and becomes liquid again. It flows back to the starting point, the evaporator. The cycle is closed and the process restarts.

Because the refrigerant cycle in GAHPs is usually hermetically sealed, service and maintenance of the units is relatively simple and very similar to maintain and servicing a regular gas boiler.

Although relatively new to residential homes, GAHPs are based on tried and tested technology over decades and provide the ideal solution to the challenges of retrofitting renewable energy systems onto older housing and heating systems.

Gas absorption heat pumps are incredibly energy efficient and will reduce the amount of energy you use. This table shows how GAHPs use less gas to generate heat and reduce carbon dioxide emissions.

gas boiler
gas boiler
Gas absorption
heat pump
Energy Efficiency * 79 % 94 % 125 %
CO2 Emissions 100 % 87 % 62 %
Energy Savings 0 % 13 % 40 %

*ETAs (ɳs) (55°C) = seasonal space heating energy efficiency (primary energy consumption, incl. electricity demand)

In addition, GAHPs use ammonia/water as a refrigerant, with no global-warming and no ozone-depletion potential.

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