Research Papers

A Feasibility Study of Using Solar Liquid-Desiccant Air Conditioner in Queensland, Australia

[+] Author and Article Information
Shahab Alizadeh1

Faculty of Built Environment and Engineering, Queensland University of Technology, GPO Box 2434, Brisbane 4001, Australiashahaḇalizadeh@hotmail.com


Present address: Department of Energy, Materials & Energy Research Centre, P.O. Box 14155-4777, Tehran, Iran.

J. Sol. Energy Eng 130(2), 021005 (Mar 10, 2008) (9 pages) doi:10.1115/1.2844426 History: Received October 29, 2005; Revised August 25, 2007; Published March 10, 2008

A feasibility study of using solar liquid-desiccant air conditioner (LDAC) developed in Queensland has been undertaken. The system uses high effectiveness cross-flow polymer plate heat exchanger (PPHE), as the absorber unit. Outside air is dehumidified by strong liquid desiccant and indirectly cooled within the PPHE. The warm dry air is, subsequently, cooled and humidified through a direct evaporative cooler and supplied to the conditioned space. The weak desiccant solution from the absorber unit is concentrated in a scavenger air regenerator using hot water from flat plate solar collectors. The prototype of the absorber unit of the liquid-desiccant system has been tested under the summer conditions of Brisbane, using lithium chloride as the absorbent solution. The results of the experiments indicate that they are in good agreement with a previously developed model for the absorber unit. The tests further reveal that the unit has a satisfactory performance in controlling the air temperature and relative humidity when installed on a commercial site of 120m2 area in Brisbane. A commercialization strategy has been proposed in this study for a solar operated LDAC in Queensland and compared with the conventional direct expansion (DX) system. Based on the computer modeling results obtained from the system simulation for a building in Cairns, North Queensland, the operating costs of the LDAC are significantly lower than its conventional DX counterpart. This study further reveals that using the solar operated LDAC with a storage system will result in considerable savings in operating costs when compared with the equivalent gas-fired system. A simple payback of five years was determined for the solar components in this study.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Schematic diagram of the cross-flow type plate heat exchanger, showing (a) the supply and return air channels and (b) the air and liquid flowing in counter current directions

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Figure 2

Schematic diagram of the liquid-desiccant solar air conditioner

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Figure 3

Three dimensional view of the LDAC absorber unit

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Figure 4

Power consumed by the fans as a function of the voltage

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Figure 5

Conductivity-concentration chart for the lithium chloride solution

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Figure 6

Psychrometric paths for the tests with (a) desiccant only (dashed line) and (b) with water and desiccant (supply air, 0-1-2-3; return air, R-S)

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Figure 7

Supply air temperature versus desiccant flow rate

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Figure 8

Supply air humidity ratio versus desiccant flow rate

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Figure 9

Variation of the power consumed by the solution pump versus voltage

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Figure 10

Conditioner effectiveness as a function of the supply air flow rate

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Figure 11

Conditioner dehumidification efficiency as a function of solution flow rate

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Figure 12

Supply air temperature versus conditioner air flow ratio

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Figure 13

Supply air humidity ratio versus conditioner air flow ratio

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Figure 14

Collector efficiency as a function of temperature difference. (Edwards Hot Water Pty Ltd.)

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Figure 15

Schematic of the scavenger air solar regenerator

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Figure 16

The solar LDAC performance flow chart showing the control systems for the conditioner and regenerator, using summer design conditions of Brisbane

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Figure 17

Schematic diagram of the 1-1∕2 effect regenerator (Lowenstein, 2004)

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Figure 18

Seasonal performance of the LDAC




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