New Delhi: Researchers from the Department of Mechanical Engineering at IIT Delhi are developing a new type of high-efficiency air conditioner. The research
team led by Anurag Goyal is currently testing a laboratory-scale prototype of this proposed system, which has demonstrated the potential to reduce electricity use by about a third. Conventional ACs work on the principle of vapour compression. The air conditioners remove humidity through overcooling the air till the moisture content condenses, which is a highly energy-intensive process. The researchers have developed a compact, add-on module that directly scrubs the moisture from the air before it is conditioned.
The module uses a salt solution or a liquid desiccant that absorbs water vapour from incoming outdoor air. This is essentially a dry, hyrophilic salt that captures atmospheric moisture. There is a thin polymer membrane between the air and the salt solution, that prevents the salt from being carried over into the air of the building, which is a common concern with existing liquid-desiccant systems. Once the solution is diluted by the absorbed moisture, it has to be dried for continuous reuse. The researchers have developed an innovative system integration concept that continuously revives and recirculates the same salt solution. Instead of using a burner or electric heater, the design uses waste heat from the AC condenser, or the outdoor unit, that is redirected to a regenerator module to continuously dry the salt solution.
A more sustainable AC
The system is designed the precisely match the energy transfer rates of the vapour compression and desiccant modules. Goyal says, “Using the proposed system at typical operating conditions, total electricity consumption decreased from approximately 1200 W for a standard room AC to about 800 W for the hybrid, resulting in around 33 per cent lower energy consumption, while meeting the same indoor comfort targets. Across representative Indian climates, the predicted savings range from 28 per cent (in very humid areas) to 41.5 per cent (in dry and arid areas).” A paper describing the research has been published in the Journal of Building Engineering.
