OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
REVIEW OF DIFFERENT TECHNOLOGIES IN THE
SOLAR ABSORPTION AIR-CONDITIONING SYSTEMS
Vinod Sehrawat a , Tarun Gupta a , Raj Kumar b
a
Department of Mechanical Engineering, NGF College of Engineering and Technology, Palwal, Haryana, India,
email: vinodsehrawat@yahoo.com, tarungupta1976@yahoo.com
b Professor, Department of Mechanical Engineering, YMCA University of Science and Technology, Faridabad
Abstract
The aim of this article is to review the currently available solar air-conditioning technologies, their energy
saving potential and technical limitations. The scope of this article is to brief the processes and to consolidate
the commercially available solar cooling technologies for comparison. Although a large potential market exists
for this technology, existing solar cooling systems are not yet competitive with conventional electricity-driven or
gas-fired air-conditioning systems because of their high initial costs. In this paper, the technologies working only
on liquid absorption cycle are discussed in brief. The paper looks at ways of improving the performance of the
solar air-conditioning (chiller) subsystems by using the different technology.
Keywords: Solar Air-conditioning; Absorption chiller; Lithium bromide and water; Generator Temperature
1. Introduction
In a country like India, the availability of solar irradiation is abundant for most part of the year. Solar airconditioning
is a particularly attractive application because of the near coincidence of peak cooling loads with
the intensity of available solar energy. The earth receives in just 1 h, more energy from the sun than what we
consume in the whole world for 1 year [1]. Its application was proven to be most economical, as most systems in
individual uses requires but a few kilowatt of power. The solar cooling technologies are mainly classified into
two main groups depending on the energy supply: a thermal/work driven system and electricity (Photovoltaic)
driven system [2]. Each group can further be classified as the following:
1. Thermal/work driven system based on absorption refrigeration cycle; adsorption refrigeration cycle; chemical
reaction refrigeration cycle; desiccant cooling cycle and ejector refrigeration cycle
2. Electricity (Photovoltaic) driven system based on vapour compression refrigeration cycle; thermo-electric
refrigeration cycle and stirling refrigeration cycle.
Of the different cycles mentioned above, the absorption refrigeration cycle appears to be one of the most
promising methods [3]. There are two cycles which are used for absorption cooling. These are (i) liquid
absorption cycle with liquid absorbents (e.g. LiBr-H 2 O, H 2 O-NH 3 , NH 3- LiNO 3 etc.); solid absorption cycle with
solid absorbents (e.g. Zeolites-H 2 O, CaCl 2 -NH 3 , Silicagel-H 2 O, NH 3- LiNO 3 etc.). In absorption cycle cooling
systems, LiBr-H 2 O and H 2 O-NH 3 are the major working pairs employed in these systems. Lithium–bromide (Li-
Br) is commonly used for cooling applications and provides chilled water at 5°C. An ammonium–water working
pair is used in refrigeration and can provide chilled water below 0°C. Among a variety of promising solar
thermal cooling technologies, a Li-Br based cooling system driven by solar thermal energy offers highperformance,
simplicity and reliability. A typical solar thermal cooling system consists of solar heat collector,
absorption chiller, hotwater storage tank, cooling tower, pumps, valves, and additional components. A solar
thermal cooling system uses solar thermal collectors to produce heat that operates a conventional absorption or
adsorption chiller that is thermally driven. The decreasing costs of solar panels and increasingly gained
experience in their applications have made solar thermal cooling system more affordable and attractive than ever.
Based upon technology reviews and available data, Xu and Tengfang [4] concluded that it provides significant
energy savings potential (approximately 56%) over conventional compressor-based 23 chillers, while cost of
saving was conservatively estimated as $7.9/kWh. It was estimated that 80% of the market for cooling
requirements in food processing would be possible – corresponding to a potential energy savings of 681 GWh
per year in California. It has been found that LiBr-H 2 O has following advantages: (i) a higher COP than for the
other working fluids; (ii) the low cost and excellent performance of this working fluid combination make it the
favourable choice for use in solar cooling cycles.
But its range of operation is limited due to the crystallization at the point of the recuperator discharge into the
absorber and stopping solution flows through the device. Also the other disadvantages associated with the
ammonia-water system are as follow by comparison:
• Generally, H 2 O-NH 3 systems operate at a 10-15% lower solar fraction than LiBr-H 2 O systems.
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