Hybrid membrane dehumidification and dewpoint evaporative cooling for sustainable air conditioning

Investigating new energy efficient and sustainable designs for air conditioning has become imperative due to air conditioning's contribution to global warming. The combination of membrane-based dehumidification and dewpoint evaporative cooling provides a possible solution that eliminates the energy-intensive process of condensation dehumidification, while also avoiding the use of harmful refrigerants. This paper is the first to present a straightforward thermodynamic model and initial assessment of a hybrid system that combines a vacuum membrane dehumidifier inspired by the Claridge-Culp-Liu (CCL) cycle with a dewpoint evaporative cooler with the additional investigation of reusing the dehumidification water to provide the evaporative cooling. A parametric study is performed for different ambient conditions. Results show the maximum achievable coefficient of performance (COP) for cooling and dehumidification with the system to be as high as 15 for very dry climate conditions, with a median value in the range of 4 over the range of typical ambient conditions. The system also displays the potential for having a self-sustaining water supply for evaporative cooling, producing up to 12x the amount of water required for the evaporative cooling portion of our system in highly humid conditions. An energy savings analysis yielded positive savings at low humidity conditions when compared to a baseline vapor compression system. Additionally, the system outperformed a baseline desiccant wheel system under all conditions. The absence of harmful refrigerants lowers overall (direct and indirect) greenhouse gas emissions associated with the M-DPEC system to as low as 50% of the baseline vapor compression system. Therefore, the model shows potential for the technology to efficiently fulfill building cooling demands while employing an environmentally friendly system to reduce greenhouse gas emissions.