Moisture-Breathing Composite Beds for Adsorption/Solar Energy-Driven Air Conditioning

Decarbonising global energy systems is essential to meet the Paris Agreement’s terms and to make steps towards a sustainable global economy. Air-conditioning systems are among the most significant global energy consumers, accounting for 20% of global electricity use and approximately 1100 mega-tons of carbon emissions annually. Typical AC systems use an energy-intensive mechanical vapour compression cycle to achieve both temperature and humidity control. An alternative is adsorption-driven cooling or dehumidification using adsorptive materials, which have a much smaller energy cost due to the lower temperatures and pressures required for their operation. Developing efficient adsorption/desorption materials is vital to enable these technologies.
In this work, we prepare and characterise a series of moisture-permeable layered porous structures comprised of an adsorbent within a composite polymer matrix. These materials are designed to provide facile adsorption and desorption of water from either surface of the layer. The adsorbents range from amorphous materials with broad pore size distributions (silica, alumina) to crystalline materials with highly defined and ordered pores (zeolites, MOFs). These adsorbents are loaded within either a porous polymer foam or permeable polymer membranes from which moisture can travel. Humidity breakthrough and water permeation studies and nitrogen and water isotherms have been obtained for each material to characterise their adsorptive/permeation capabilities, with TGA, SEM, and AFM used to describe the structure and morphologies of the materials.
Alongside wet lab experiments, we have performed atomistic molecular dynamics simulations to corroborate our experimental observations and provide a screening method for determining future materials for testing based on water surface contact angle and pore diffusion predictions. This work will facilitate the design of more sustainable, adsorption-driven air-conditioning units.