NUS Enterprise

Energy Saving Desiccant Dehumidifier for Efficient Air Conditioning

Technology #2017-335

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Mrinal Jagirdar
Poh Seng Lee
Managed By
Mr Ma Mun Thoh (
Senior Associate Director (65)65166506
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Tech Offer [PDF]

Industry Problem

20% of the total energy consumed in developed countries is utilized for air-conditioning. Thus, especially for places experiencing warm and humid conditions, besides the huge energy bills paid by the end-users, air-conditioning equipment is responsible for enormous carbon emission. Thus, HVAC industry requires innovative solution which can substantially boost the performance of air-conditioners. Hyper-efficient dehumidifiers that can utilize the low-temperature heat that the condenser otherwise rejects, need to be designed to completely eliminate the latent-heat load on the evaporator and help make air-conditioners highly energy efficient.


NUS researchers have developed a dehumidifier that can be easily installed/retrofitted in the ducting, upstream of the air-handling unit (AHU) of a conventional central air-conditioning unit as shown in Figure 1(a). The dehumidifier is a bank of tubes that is coated with a solid-desiccant on its external surface, see Figure 2. It realizes quasi-isothermal dehumidification and regeneration processes (as opposed to adiabatic processes in conventional desiccant wheels) which makes the dehumidification/regeneration process highly efficient only requiring ultra-low grade heat for regeneration. As shown by the process line in Blue in Figure 1 (b), it can completely handle the latent heat load of outdoor air by utilizing (i) the room-return air as the regeneration air-stream (ii) warm water at ~38 oC from the water-cooled condenser during regeneration (iii) cool water at 30 oC from the cooling tower (or an auxiliary water-condenser). Note that the air-states in Figures 1(a) and (b) are consistent.


Value Proposition

• Easy to retro-fit (only air-ducts and water piping need modification).

• It can completely handle the latent heat load, so low lift chiller may be used

    implying greater COP.

• Ultra-low temperature (Only 8 °C more than cooling-tower water temperature)  

    waste-heat from condenser required for regeneration.

• >50% savings on compressor’s energy utilization

• Smaller capacity compressor and smaller evaporator/condenser

   coil size required for the same cooling load.

• Overall energy-savings is >30%.

• No moving parts hence it needs little maintenance