Absorption Heat Transformer Systems for Energy Recovery

Absorption heat transformer (AHT) systems represent a class of thermally driven heat-upgrading technologies that recover low-grade waste heat and elevate its temperature to levels suitable for process heating or refrigeration support. Employing cyclic absorption and desorption processes, typically with a working pair such as lithium bromide–water, these systems harness thermal energy instead of mechanical work. They are invaluable in sectors where waste streams at 40–150 °C are abundant yet under-utilised. By improving the coefficient of performance (COP) relative to conventional heat pumps, AHTs contribute to reduced primary energy consumption and lower carbon emissions. Recent advances in configuration—from single-stage to double-effect and multi-stage designs—have expanded achievable temperature lifts while balancing COP and exergy efficiency. Integration with renewable heat sources, such as solar thermal collectors, further enhances their versatility. Globally, AHTs are being deployed for chemical processing, food drying, district heating and desalination, underscoring their role in circular energy economies and net-zero targets.

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Absorption Heat Transformer Systems for Energy Recovery publication trend

The graph below shows the total number of articles in absorption heat transformer systems for energy recovery across all publications each year (not limited to Nature Index journals).

Technical terms

Absorption heat transformer (AHT): thermally driven cycle that upgrades low-grade heat to higher temperature levels using absorption and desorption processes.

Coefficient of performance (COP): ratio of heat delivered at elevated temperature to the heat input at driving temperature.

Exergy efficiency (η_ex): measure of useful work potential recovered relative to the exergy of the input heat.

Gross temperature lift (GTL): temperature difference between output and input heat streams in an AHT system.

Working pair: absorbent and refrigerant combination (e.g., lithium bromide–water) enabling the absorption cycle.

References

1. Thermochemical technologies for industrial waste heat recovery: A comprehensive review. Renewable and Sustainable Energy Reviews (2025).
2. Investigation of a solar-driven absorption heat transformer with various collector types for industrial process heating. Applied Thermal Engineering (2024).
3. Control Strategy Based on Artificial Intelligence for a Double-Stage Absorption Heat Transformer. Processes (2023).
4. Solar Water Heating System with Absorption Heat Transformer for Annual Continuous Water Heating. Processes (2024).