Studies on cocopeat, sawdust and dried cow dung as desiccant for evaporative cooling system Ashutosh Singh a , Sunil Kumar b, * , Rahul Dev a a Department of Mechanical Engineering, Motilal Nehru National Institute of Technology Allahabad, Allahabad 211 004, India b Council of Scientific and Industrial Research-National Environment Engineering Research Institute (CSIR-NEERI), Nehru Marg, Nagpur 440 020, India article info Article history: Received 1 August 2017 Received in revised form 21 April 2019 Accepted 22 April 2019 Available online 27 April 2019 Keywords: Natural desiccant Evaporative cooling Desiccant Cocopeat Sawdust Cow dung abstract The aim of the present study was to investigate the ability of natural materials, such as dried cow dung, cocopeat, and sawdust to be used as a desiccant in the evaporative cooling system to reduce the inlet air humidity. Moisture sorption and desorption characteristics of these natural materials were found out and also compared with that of silica gel. These materials were tested in different air conditions to know the sorption (28  C-85% RH, 28  C-60% RH, 33  C-60% RH) and desorption characteristics (50  C-10% RH). The materials' behavior in different humidity with the same temperature; and the same humidity with different temperature was also studied. These natural materials were studied to replace costly chemical desiccants, such as silica gel, zeolites, etc. Experimental results confirmed that cocopeat and dried cow dung have the potential to replace the chemical desiccants based on their sorption and desorption characteristics while sawdust was not found to have the desired characteristics of good desiccant. These natural materials (considered as waste) are cheap, and their reutilization will also be helpful to minimize the waste management problem. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction The primary sources of energy, i.e., natural gas, coal, and oil are consumed widely as compared to the renewable sources of energy, such as solar, geothermal, hydro, wind and biomass. The concern is not only the depletion of primary sources of energy but also their burning causes CO 2 emission. The release of CO 2 emission to the environment is increasing yearly. The increased emission results into many climatic disturbances, such as an increase in global temperature, etc. [1e3]. The use of CFCs/HCFCs refrigerants in the conventional vapor-compression refrigeration and air-conditioning system damages the ozone layer and hence the environment. It is now a growing demand to develop energy-efficient refrigeration and air conditioning systems which will help to reduce the demand for energy. Evaporative cooling (EC) utilizes a natural cooling effect for cooling the building [3]. The EC alone is a good alternative to a vapor-compression cooling system for sensible cooling while for both sensible cooling and dehumidification, it is used with some other dehumidification system. EC works on the principle of employing water's large enthalpy of vaporization. The temperature of dry air can be reduced significantly by taking advantage of phase transition of liquid water to water vapor (evaporation), due to which air can be cooled using less energy as compared to compressor-based cooling [3]. Desiccant-based cooling and dehumidification system is also a promising alternative in hot and humid climate [4]. The main advantage of the system is the separate handling of air sensible energy and latent load. Humidity is removed by the desiccant, and cooling system helps in attaining the desired air temperature. After adsorbing/absorbing air humidity, it becomes necessary for the desiccant to be regenerated by hot air to make it suitable for dehumidification again. The most important results of coupled desiccant and traditional EC system are the reduction in energy consumption and enhancement of the cooling efficiency that consequently decreases CO 2 emissions [5e8]. Desiccant-based EC technology is comparatively new. The most important consider- ation in the desiccant-based cooling and dehumidification system is that it can be operated by solar energy [9e11], waste-heat [12] and other low-temperature thermal energy sources [13]. The desiccant based system is evolved in various designs and combi- nations, such as hybrid desiccant cooling system [14], the combi- nation with other devices [15] and multi-stage dehumidification * Corresponding author. E-mail addresses: s_kumar@neeri.res.in, sunil_neeri@yahoo.co.in (S. Kumar). Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene https://doi.org/10.1016/j.renene.2019.04.122 0960-1481/© 2019 Elsevier Ltd. All rights reserved. Renewable Energy 142 (2019) 295e303