Advances in Phytochemistry, Textile and Renewable Energy Research for
Industrial Growth – Nzila et al. (Eds)
© 2022 Copyright the Author(s), ISBN: 978-1-032-11871-0
Open Access: www.taylorfrancis.com, CC BY-NC-ND 4.0 license
Solar adsorption cooling with focus on using steatite adsorbent: A review
E.M. Nyang’au & K. Kiriamiti
Department of Mechanical, Production and Energy Engineering, Moi University, Eldoret, Kenya
ABSTRACT: The focus on solar cooling systems is driven by the need for efficient and pollution free climate friendly technologies. Such systems are required to meet cooling requirements in medical, post-harvest
preservation of food in remote areas and ice-making. Solar radiation within tropics poses an opportunity for
exploitation in solar adsorption systems. Research activities in this sector are geared towards finding technical,
environmental and economic solutions to existing systems. The purpose of this paper is to review advancement in solar adsorption cooling systems in view of using novel composite adsorbent consisting of impregnated
steatite, paired with methanol as adsorbate. The review presents a brief background on the basic adsorption
process, working pairs and challenges of current adsorption systems along with published performance data
and improvement strategies. It is noted that solar adsorption systems suffer low conversion efficiency and high
capital cost in comparison with conventional vapour compression systems.
Keywords: Solar adsorption, Steatite, Adsorbent, Adsorbate, Refrigeration, Coefficient of Performance
NOMENCLATURE
COP coefficient of performance.
K constant.
n constant.
P adsorption pressure, kPa.
q st isosteric heat of adsorption, kJ/kg.
SCP specific cooling power.
T adsorbent temperature, K.
T ads adsorption temperature,
◦ C.
T d driving temperature,
◦ C.
T evp evaporation temperature,
◦ C.
T sat saturation temperature corresponding to the refrigerant pressure, K.
X refrigerant concentration, kg refrigerant /kg adsorbent.
x o refrigerant concentration at saturation conditions,
kg refrigerant/kg adsorbent.
1 INTRODUCTION
Vapour compression refrigeration cycles consume
large amounts of electrical energy which significantly
increases consumption of expensive and polluting fossil derived energy. In addition, operation of vapour
compression systems use synthetic refrigerants (Chlorofluorocarbons, CFC’S, Hydro chlorofluorocarbons,
HCFC’s and Hydro Fluorocarbons, HFC’s) which contribute to the Green House Gas (GHG) effect. The
energy crisis has triggered attention from researchers
and engineers to seek for energy efficient, sustainable and environment friendly solutions to address
the increasing demand for energy. Solar and low
grade thermal energy present an effective way worth
exploring to address both environmental pollution and
high energy consumption problems associated with
conventional vapour compression cycles. One of the
applications of solar and low grade thermal energy is
in adsorption refrigeration systems in which adsorption of refrigerant liquid or gas takes place on a solid
surface. In this process, the adsorbed particles enter
the porous solid adsorbent and sit on its surface by
adhesion (Wang et al., 2014). Solar adsorption cooling systems are easy to install and maintain, use clean
energy sources and therefore pollution free, do not
have moving parts and have long life. They are useful for ice-making, air conditioning, medical and food
preservation in off-grid areas. However, the major
disadvantage of these systems is low performance
compared to other refrigeration and cooling systems.
Application of solar energy in refrigeration is
attractive because of the coincidence of peak cooling demand with available solar power. Furthermore,
energy demand for air conditioning during summer
period in developed countries propagates increased
consumption of electricity hence high GHG emissions
while within the developing countries, the grid is out of
reach in most remote areas thus rendering use of solar
for provision of refrigeration services advantageous.
Post-harvest losses of agricultural products can be
improved if storage is done at low temperatures using
solar refrigeration technologies. This would eliminate
sharp differences in food supplies between harvest
seasons.
Solar refrigeration is dependent upon environmental factors such as cooling water temperature, local
weather, solar irradiation, air velocity and temperature.
DOI 10.1201/9781003221968-36
265
Industrial Growth – Nzila et al. (Eds)
© 2022 Copyright the Author(s), ISBN: 978-1-032-11871-0
Open Access: www.taylorfrancis.com, CC BY-NC-ND 4.0 license
Solar adsorption cooling with focus on using steatite adsorbent: A review
E.M. Nyang’au & K. Kiriamiti
Department of Mechanical, Production and Energy Engineering, Moi University, Eldoret, Kenya
ABSTRACT: The focus on solar cooling systems is driven by the need for efficient and pollution free climate friendly technologies. Such systems are required to meet cooling requirements in medical, post-harvest
preservation of food in remote areas and ice-making. Solar radiation within tropics poses an opportunity for
exploitation in solar adsorption systems. Research activities in this sector are geared towards finding technical,
environmental and economic solutions to existing systems. The purpose of this paper is to review advancement in solar adsorption cooling systems in view of using novel composite adsorbent consisting of impregnated
steatite, paired with methanol as adsorbate. The review presents a brief background on the basic adsorption
process, working pairs and challenges of current adsorption systems along with published performance data
and improvement strategies. It is noted that solar adsorption systems suffer low conversion efficiency and high
capital cost in comparison with conventional vapour compression systems.
Keywords: Solar adsorption, Steatite, Adsorbent, Adsorbate, Refrigeration, Coefficient of Performance
NOMENCLATURE
COP coefficient of performance.
K constant.
n constant.
P adsorption pressure, kPa.
q st isosteric heat of adsorption, kJ/kg.
SCP specific cooling power.
T adsorbent temperature, K.
T ads adsorption temperature,
◦ C.
T d driving temperature,
◦ C.
T evp evaporation temperature,
◦ C.
T sat saturation temperature corresponding to the refrigerant pressure, K.
X refrigerant concentration, kg refrigerant /kg adsorbent.
x o refrigerant concentration at saturation conditions,
kg refrigerant/kg adsorbent.
1 INTRODUCTION
Vapour compression refrigeration cycles consume
large amounts of electrical energy which significantly
increases consumption of expensive and polluting fossil derived energy. In addition, operation of vapour
compression systems use synthetic refrigerants (Chlorofluorocarbons, CFC’S, Hydro chlorofluorocarbons,
HCFC’s and Hydro Fluorocarbons, HFC’s) which contribute to the Green House Gas (GHG) effect. The
energy crisis has triggered attention from researchers
and engineers to seek for energy efficient, sustainable and environment friendly solutions to address
the increasing demand for energy. Solar and low
grade thermal energy present an effective way worth
exploring to address both environmental pollution and
high energy consumption problems associated with
conventional vapour compression cycles. One of the
applications of solar and low grade thermal energy is
in adsorption refrigeration systems in which adsorption of refrigerant liquid or gas takes place on a solid
surface. In this process, the adsorbed particles enter
the porous solid adsorbent and sit on its surface by
adhesion (Wang et al., 2014). Solar adsorption cooling systems are easy to install and maintain, use clean
energy sources and therefore pollution free, do not
have moving parts and have long life. They are useful for ice-making, air conditioning, medical and food
preservation in off-grid areas. However, the major
disadvantage of these systems is low performance
compared to other refrigeration and cooling systems.
Application of solar energy in refrigeration is
attractive because of the coincidence of peak cooling demand with available solar power. Furthermore,
energy demand for air conditioning during summer
period in developed countries propagates increased
consumption of electricity hence high GHG emissions
while within the developing countries, the grid is out of
reach in most remote areas thus rendering use of solar
for provision of refrigeration services advantageous.
Post-harvest losses of agricultural products can be
improved if storage is done at low temperatures using
solar refrigeration technologies. This would eliminate
sharp differences in food supplies between harvest
seasons.
Solar refrigeration is dependent upon environmental factors such as cooling water temperature, local
weather, solar irradiation, air velocity and temperature.
DOI 10.1201/9781003221968-36
265