Researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia have developed NESCOD, a novel passive cooling technology that addresses the rising global demand for cooling without relying on energy-intensive air conditioners. This system leverages the thermodynamic properties of endothermic dissolution to offer an eco-friendly alternative for off-grid communities and extremely hot regions.
How NESCOD Works
The NESCOD system operates through a two-stage thermodynamic cycle: dissolution cooling and solar-driven solute regeneration. In the cooling cycle, ammonium nitrate salt is dissolved in water, an endothermic reaction that absorbs heat from the surroundings and rapidly lowers the liquid's temperature. Laboratory tests demonstrated a cooling power of up to 191 watts per square meter under standard conditions, as published by the Royal Society of Chemistry.
Solar Regeneration Process
To make the system sustainable and repeatable, researchers designed a 3D solar regenerator. Sunlight evaporates water from the salt solution, causing ammonium nitrate to recrystallize, effectively recharging the system for another cooling cycle. This separation of dissolution and regeneration allows the cooling effect to be stored and accessed whenever needed, even at night or in different seasons.
Consistent Cooling Performance
NESCOD maintains effective cooling over multiple cycles. Under one sun illumination, it evaporates water at about 2.2 kg per square meter per hour, maintaining temperatures between 5°C and 15°C—ideal for cold-chain storage and space cooling. Additionally, the system captures water vapor for reuse with impurity levels below 1 ppm, which is particularly valuable in arid regions where water conservation is critical.
Economic Viability
The materials used in NESCOD, especially ammonium nitrate, are both effective and inexpensive. Ammonium nitrate is widely produced for fertilizers, making it a sustainable chemical-energy carrier. The 3D solar regenerator's high-area architecture achieves a high evaporation rate with a small footprint, reducing material costs per cooling unit compared to other solar-thermal systems. This economic efficiency positions NESCOD as a viable candidate for large-scale deployment in developing nations and remote areas lacking traditional electricity infrastructure.
