Low-grade heat is a challenge for deep utilization due to its low temperature. Based on the optimization of the saturated vapor pressure of liquid desiccant in absorption or dehumidification cooling systems, an idea of deep utilization of low-grade heat is proposed in this paper. Instead of optimizing the cycle process or equipment, this paper achieves this goal by obtaining a multi-component salt solution with the advantages of both strong moisture absorption capacity and lower regeneration temperature. The sensitivity of saturated vapor pressure to temperature is defined to evaluate the performance of the salt solution, and the sensitivity mechanism is revealed. The results show that the sensitivity of saturated vapor pressure to temperature increases with the increase of ion charge density, and compositional modulation is proposed to improve the sensitivity. The formula of a multi-component salt solution is taken as an example to illustrate the deep utilization of low-grade heat. As a result, the dehumidification performance of the multi-component dehumidification is equivalent to that of the typical desiccant solution, but its regeneration temperature is about 4 K lower. Furthermore, by using the concept proposed in this paper, it is pointed out that the utilization of low-grade heat can be improved by 40% approximately in an absorption cooling system.

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