Upgrading Waste Heat from 90 to 110 °C: The Potential of Adsorption Heat Transformation

Low-grade heat is abundantly available below 100 degrees C, whereas industry mainly needs heat above 100 degrees C. Thus, the industry cannot directly utilize low-grade heat to save primary energy and emissions. Low-grade heat can be utilized by adsorption heat transformers (AdHTs); however, closed AdHTs to upgrade heat above 100 degrees C are only investigated by idealized steady-state analyses, which indicate the maximal theoretical performance. For evaluating the performance achievable in practice, this work studies a closed AdHT in a one-bed configuration using dynamic simulation. For the working pair AQSOA-Z02/H2O, the performance is optimized via the design of the adsorber heat exchanger and the control of the AdHT cycle. When heat is upgraded from 90 to 110 degrees C, releasing waste heat at 35 degrees C, the maximum exergetic coefficient of performance (COPexergetic) is 0.64, and the maximum specific heating power (SHP) is 590 W kg(-1). The maximum SHP can increase by 35% when releasing waste heat at 25 degrees C. Both performance indicators strongly depend on design, control, and the available temperature of the waste heat. Overall, AdHTs with optimized design and control are promising to utilize low-grade waste heat.

Automated summary

Low-grade heat below 100 degrees C is abundant, but industry mainly requires heat above 100 degrees C. This study focuses on utilizing low-grade heat through adsorption heat transformers (AdHTs) and optimizing performance through design and control. Waste heat temperature significantly affects the performance indicators of AdHTs.