Novel Energy Efficient Integration of Chimney Ventilation, Liquid Desiccant Dehumidification, and Evaporative Cooling for Humid Climates: Performance Optimization and Economic Feasibility

Abstract

This study introduces and optimizes a novel, energy-efficient ventilation and cooling system designed specifically for hot and humid climates. Conventional chimney-driven ventilation systems are ineffective in such environments due to the high latent load of outdoor air. To overcome this, the proposed system integrates a chimney-driven ventilation with a membrane-based liquid desiccant dehumidification loop and an indirect evaporative cooler to decouple latent and sensible loads and enhance indoor air quality while significantly reducing energy consumption. Mathematical models were developed to simulate the coupled heat and mass transfer in the desiccant channels, chimney, and IDEC units. These models were validated through laboratory-scale experiments. An XGBoost–Genetic Algorithm hybrid optimization framework was used to size and optimize the integrated system for a typical office in Beirut, Lebanon. In summer, the system maintained airflow between 45 L/s to 48 L/s, with supply air at 24℃ and 40%-60% RH, meeting ventilation needs for July and August while slightly underperforming in months with lower ambient temperatures. Sensitivity analyses identified ambient conditions and desiccant flow rate as key performance drivers. The CDL-IDEC system demonstrated annual energy savings of approximately 480 kWh, covering 92% of the ventilation cooling load, equivalent to $192 USD/year. The total capital cost was estimated at $1,159 USD. The system achieved a Simple Payback Period of 7 years and a Discounted Payback Period of 12 years at a 12% discount rate. The NPV over a 20-year period was $246 USD, and the ROI was calculated at 21%, confirming fair economic viability. Environmental benefits include 0.2 tons annual CO2 reduction and a 73% HVAC-related energy use, significantly supporting compliance with Net Zero Energy Building targets. This research establishes the CDL-IDEC system as a novel, technically robust, and environmentally transformative solution for ventilation and cooling in hot and humid climates. Its cost-effectiveness, scalability, and significant energy savings position it as a promising candidate for widespread adoption, with strong potential for future enhancements to broaden its applicability across diverse climatic conditions.