Conceptualization and investigations on a cooling-heating co-generation and step-utilization heat pump for efficient direct air capture

Climate change significantly challenges human future, and direct air capture (DAC) technology is recognized as a key solution to mitigate global warming. Heat pumps can help promote DAC technology, yet, issues such as inefficient sensible heat recovery and temperature mismatching during heat exchange remain challenges. To address these issues, a heat pump configuration with cooling-heating co-generation and step-utilization is innovatively proposed and integrated with a DAC system in this work. For energy performance, the integrated system achieves a maximum reduction of 37.9 % in energy consumption, and the energy-saving effect is maintained across various conditions. The system attains an annual energy performance factor (AEPF) of 1.66 MJ/kg, indicating an AEPF reduction of 34.5 % over the reference system. An exergy analysis confirms that increased heat pump efficiency and enhanced heat transfer are the primary contributors to these benefits. Life cycle assessment shows a specific cost of 63.2 $ per ton of CO2, which is 24.8 % lower than the reference system. Meanwhile, the system achieves a net CO2 removal factor of 0.65, with a maximum improvement of 52.7 % in CO2 removal efficiency. The system also shows great application feasibility due to its ability to integrate different energy sources and air-conditioning equipment. These findings suggest that the novel system is energy-efficient, cost-effective, and highly efficient in net-CO2 removal, offering a promising pathway for advancing DAC technology and supporting carbon neutrality process for climate governance. The development and application of such an efficient energy system help mitigate environmental pollutants for a net zero future.