Gas Absorption Heat Pumps GAHP 01112020 1 Titre

Gas Absorption Heat Pumps (GAHP) 01/11/2020 1 Titre de la présentation

1. Principles of the technology Gas sorption heat pumps combine natural gas and renewable energies for heating and domestic hot water with very high efficiency n Thermally driven cycle activated by natural gas: A sorption heat pump is similar to any heat pump (use of a cold renewable source to heat the building), but the compression is replaced by a thermally reaction driven by a natural gas burner. • Two technologies can be used: Natural gas combustion Thermally driven reaction Absorption Adsorption • Several sources • Renewable: solar, aero-thermal, • Heat recovery: waste water, exhaust air • Several Working pairs refrigerant/sorbent • Ammonia/Water, Water/Zeolite, … 2 Expansion Geothermal Refrigerant Condensation Evaporation • Adsorption heat pumps: the refrigerant is usually adsorbed by a solid Flue gas condensation Compression • Absorption Heat pumps: the refrigerant is absorbed by a liquid Ab- or adsorption Working fluid condensation Heating loop 3 heat productions Cold source

Gas absorption heat pumps (GAHP) use a continuous cycle with a liquid absorbent n The thermal reaction is composed of a phase of absorption producing heat, and a phase of desorption driven by the gas burner. 1 2 3 3’ The refrigerant, vapor at low pressure, is absorbed by the sorbent in the absorber. This exothermal reaction releases heat that is transferred to the heating system. The liquid solution (refrigerant + sorbent) is carried at high pressure by a pump which needs a small energy input. 3 The gas burner heats the solution in the generator : this separates the gaseous refrigerant from the liquid sorbent (at high pressure). Heat from burner flue gas is transferred to the heating system via a condensing exchanger. The sorbent is driven to the absorber via an expansion valve. 4 5 The refrigerant arrives in the condenser. It becomes a liquid at high pressure by releasing heat to the heating loop. The condensed refrigerant passes through an expansion valve to reduce the pressure. 3’ 2 1 6 In the evaporator, heat is extracted from the outside air to evaporate the refrigerant. 6 Schematic of a Gas Absorption Heat Pump using outside air as renewable source n The current equipments are designed with a ammonia/water “GAX cycle” in a single-stage absorption cycle. It implies high pressure on condenser part (22 bars). 3

The Ammonia/water absorption heat pump simplified principle 01/11/2020 4

Specific advantages of GAHP Environmental impact : → Natural working fluid (NH 3) with zero global warming potential → Primary Energy savings : depends on energy mix. With actual standard European value : 20 to 45% compared to standard systems (condensing gas boiler) and similar level as an efficient EHP with an annual performance of 3. 3 → CO 2 reduction : 20 to 45% compared to standard systems (gas boiler) Source : EHPA Outlook 2010 → Statement on recycling : solution (ammonia/water) recycling is well organized. The recycling network is also capable to separate inhibitor which contains a small quantity of heavy metal from this solution. → Use 25 % of renewable energy Specific advantages : → High temperature (65 °C) hot water production (with absorption/ammonia cycle), which is not possible with low temperature EHP → Heating capacity stability at low outside ambiant temperatures → Limited waste of energy for defrost compared to electric compression heat pumps → Reliability, quietness (absence of compressor due to the absorption principle) → Reduced surface area of sensors (2 time less) for ground source GHP compared to EHP 5