**8. Recent developments and future needs**

**Figure 14.** Cost of fan [9].

134 Sustainable Air Conditioning Systems

**Figure 15.** Cost of pump [9].

**Figure 16.** Specific costs of thermal cooling systems. Source: Green Chiller.

The performance and development of desiccant cooling systems strongly depends on the desiccant materials used. The thermo-physical properties of these materials affect the performance of the system significantly. The key parameter for the selection of a desiccant material is that it should have the ability to absorb and hold large amount of water vapor. It should be desorbed easily by providing heat input.

The properties such as density, vapor pressure, etc. of different desiccant materials can be enhanced by mixing two or more materials together. The mixed desiccants are termed as composite desiccants. Many researchers have studied the properties of composite desiccant materials in order to study their effects on dehumidification performance of the system. **Table 3** provides a summary of some experimental studies on desiccant cooling systems and lists the regeneration temperature and desiccant material used [18–24]. The literature review showed that most of the experimental studies were conducted with silica gel at high regeneration temperatures. There is currently limited research conducted with desiccant wheel other than silica gel.

Although, a number of developments have been made in desiccant cooling technology but a number of steps still needs to be addressed in order to make this technology more market accessible. Some of the future research and development needs are:



**Table 3.** Summary of literature for regeneration temperature and desiccant materials.

• Advanced indirect evaporative coolers should be integrated with liquid dehumidification system to make the system more commercial.

**Nomenclatures**

Greek letters

Subscripts

a air

h specific enthalpy (kJ/kg)

*m*̇ mass flow rate (kg/s)

Qreg regeneration heat (kW)

T dry bulb temperature (°C)

Tw wet bulb temperature (°C)

/kga )

Renewable and Sustainable Air Conditioning http://dx.doi.org/10.5772/intechopen.73166 137

\* and Shafiqur Rehman<sup>2</sup>

2 Center for Engineering Research, Research Institute, King Fahd University of Petroleum

\*Address all correspondence to: mujahidrafique89@gmail.com

1 Independent Scholar, Toba Tek Singh, Pakistan

ω humidity ratio (kg<sup>v</sup>

ε effectiveness

DW desiccant wheel

DCS desiccant cooling system

HRW heat recovery wheel

EC evaporative cooler

p process

v vapor

**Author details**

r regeneration

1, 2, 3…. state points

Muhammad Mujahid Rafique<sup>1</sup>

and Minerals, Dhahran, Saudi Arabia

Qcool cooling load (kW)

hfg specific enthalpy for water (kJ/kg)

• The system should be developed for longer operation to avoid possible operating problems in industrial applications such as acidifying the desiccant, foaming, etc.

Research and development of liquid desiccant cooling system requires more efforts from experts in the area. Design activities needs to be developed to make this technology accessible to all people in different parts of the worlds.
