TECH

Hybrid desiccant and shallow geothermal cooling can cut energy use in humid climates

A research team from Taiwan has developed a novel hybrid air-conditioning system integrating shallow geothermal energy and a desiccant wheel. Field tests confirm it significantly reduces energy consumption by up to 34.3% in hot and humid climates, offering a promising solution for net-zero buildings.

Air conditioning is essential in hot and humid regions, but it consumes a large share of building energy. In subtropical climates such as Taiwan, cooling systems often account for up to 40% of electricity use. To address this challenge, researchers have developed a new hybrid air-conditioning system that combines shallow geothermal energy with desiccant-based dehumidification.

Unlike conventional systems that cool and dehumidify air simultaneously, the new approach separates these processes. A desiccant wheel removes moisture from ventilation air, while a ground-source heat pump and shallow geothermal energy handle temperature control. This design avoids energy-intensive condensation dehumidification and improves overall system efficiency.

The research team conducted on-site experiments in Taiwan under various seasonal conditions. Results showed that the system maintained indoor comfort across a wide range of temperatures and humidity levels. The study is published in Energy Conversion and Management.

During hot and humid summer conditions, the system reduced energy consumption by approximately 34.3% compared to a conventional air-conditioning system. Even during milder spring and autumn conditions, energy savings of 18.7% were achieved.

A hybrid air-conditioning system integrating shallow geothermal energy and desiccant dehumidification was tested under real-world conditions in Taiwan, proving highly effective in slashing energy consumption for hot and humid climates. Credit: National Taiwan University

A year-round analysis further revealed that shallow geothermal energy alone could meet indoor cooling or heating needs for nearly 40% of the time. However, due to consistently high humidity, the desiccant dehumidification system remained essential for about half of the annual operation. The study also demonstrated that the system could flexibly switch between different operating modes depending on outdoor conditions, ensuring both efficiency and comfort.

In addition to energy savings, the system offers practical advantages. It uses stable underground temperatures as a natural heat source or sink, improving performance compared to traditional air-cooled systems.

This research highlights a promising pathway toward low-energy and sustainable cooling technologies, particularly in regions facing increasing cooling demand due to climate change.

"By combining renewable shallow geothermal energy with innovative humidity control, we can significantly reduce the energy burden of air conditioning in hot and humid climates," says corresponding author Dr. Sih-Li Chen, professor of mechanical engineering at National Taiwan University.

Provided by National Taiwan University