Energy and operational cost-saving analysis of air conditioning in a production hall by
solar powered vapour absorption chiller
Muhammad Khizar Farooq 1*, Dr.AsadNaeem Shah1, Muhammad Farooq2
1. Department of Mechanical Engineering, University of Engineering and Technology, Lahore 54000, Pakistan
2. Department of Mechanical, Mechatronics & Manufacturing Engineering, KSK Campus, University of Engineering
and Technology Lahore Pakistan
Abstract:
Rapid industrialization rising economic development and exponential growth in the world’s population has led
to an increasing global demand for energy. In present era, Energy crisis is one of the major issues of Pakistan.
Due to non-availability of resources, Pakistan has not been able to completely utilize its Hydel and Thermal
power potentials for the production of electricity. Therefore alternate energy resources need to be explored to
make up the deficiencies in this sector. A lot of research work has been done to convert solar energy to cost
effective commodity over the past few years. Prospects of solar energy are attractive and efficient in countries
like Pakistan where we have abundant sunshine hours. The biggest solar contribution to our energy needs can be
through solar cooling technology. The use of solar energy for building cooling may potentially provide the
solution to these economic and environmental problems.
In present research; experiments have been carried out to calculate tons of cooling loads required in a
production hall located near Lahore. The dimensions of production area are 128 x 43 x 13 feet to accommodate
75 occupants at a time. Two conventional air conditioning units of 4, 60,000 Btu / h i.e. of 38 tons of
refrigeration capacity are currently being used for cooling purpose. Existing cooling load was calculated by
Hourly Analysis Program (HAP) which is one of most widely used software at commercial level by HVAC
engineers. A graphical demonstration gives relation between varying ambient temperature and corresponding
changes in cooling load requirement and amount of KW input required for different number of compressors in
use. From this data a comparison is derived between conventional air conditioning and solar powered vapour
absorption technology for KW input and operational cost saved as per existing air conditioner operating hours
and electricity tariff.
Key words: Energy saving by solar energy, vapour absorption chiller, Hourly Analysis Program (HAP).
*Corresponding author E-mail: khizarshk@gmail.com
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1) Introduction
Air conditioning is the most widely used medium for meeting cooling demand and maintaining indoor air
quality in a room or a hall. However factors like fossil fuel consumption for electricity generation, Global
Warming Potential (GWP) and Ozone Depletion Substances (ODS) due to usage of refrigerants are associated
with conventional methods of air conditioning. Rise in electricity demand is directly influenced by Industrial
and domestic consumer from which major portion of demand and consumption is shared by HVAC sector
especially of industrial areas.
Continuous and affordable power supply for air conditioning can be assured by research, planning and
development of indigenous energy resources, however it is a long term process and exploitation of new
resources requires huge capital investment.
Turner et al., (2006) explains comprehensively about benefits of alternate energy resources potential in terms of
operational cost saving as well as environment friendly emissions. Reduction in Green House Gases (GHGs),
controlling GWP and most important of all decreasing dependency on fossil fuels for electricity generation can
be done by using alternate energy resources. By using alternative energy resources, different objectives like
energy security and universal access to modern energy services could be achieved.
Exploration of alternate energy resources as well as energy management can help us in developing a supply
chain between energy generation and demand. Problems of energy resources scarcity and environmental
hazardous emissions needs to be considered while establishing of long term energy policy and plans.
Doubts about return on investment and operational efficacy of renewable energy resources are well addressed
by renewable energy power plants operating all over the world. Gelamn (2012) highlighted that in Germany
alone installed electricity generation capacity with Photo voltaic (PV) and Concentrated Solar Power (CSP) is
over 30 GW and around 8 GW in the US.
Kroll (2013) explains one of most practical approach for operational cost estimation of renewable energy
resources; it involves not only cost calculation of unused renewable energy resources in place of exhaustible
fossil fuels but also by estimation of probability of non-availability of future fossil fuels for future energy
demands. This criterion of cost comparison between conventional existing system and non-utilization of an
alternate energy system which is renewable, free of cost and inexhaustible has been used in this experimental
analysis by a different methodology i.e. with operational cost estimation of both conventional and renewable
systems.
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Substantial amount of energy can be saved if consumption of energy is controlled and monitored. Thus
approximately saving 1 KW of energy at consumer end can subsequently result in 5.5 KW energy saving at
source taking operational and transfer / distribution efficiency of around 30% and 60 % respectively (Vaishnav,
2013).
Philibert (2011) highlighted one of biggest contributions of solar power to our energy needs which are solar
heating and cooling technologies. Operating air conditioners by solar energy reduces electricity requirement to
run a conventional compressor.
One of most widely used type of solar cooling technology category is closed solar absorption cycle. Solar
powered vapour absorption chiller is one of complete unit which can be used as substitute of electrically
operated conventional air conditioner (Hwang et. al., 2008). Although electricity is also required in Solar
powered vapour absorption chiller for its auxiliary parts but it is very less as compared to conventional air
conditioner. Compressor of a conventional air conditioner is replaced by 4 units (generator, heat exchanger,
expansion valve and absorber) in an absorption chiller. A schematic diagram of solar absorption chiller with its
major components is shown in figure 1.
Fig. 1 Schematic diagram of solar powered vapour absorption chiller
Generator which is the main electricity consumer is powered by solar energy. Type of solar collector is one of
major design consideration parameter in this conditioning unit. Kalogirou (2004) elaborates about different
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types of solar collectors available for commercial use, which includes Flat plate collector (FPC), Evacuated tube
collector (ETC) and Parabolic through collector (PTC) etc., all of them have different operating temperature
range and perform equally well under particular conditions.
2) Materials and Methods
2.1) Design of absorption chiller
Selection of proposed substitute of conventional air conditioning unit with solar absorption chiller involves two
major components.

Selection of Solar Collector

Selection of absorption chiller
Where required operating temperature is 80-100 Co Evacuated Tube Collector (ETC) are used whereas Flat
Plate Collectors (FPC) are used where temperature less than 80 Co is required (kalogoriou, 2009). List of solar
collector properties is shown in table
Table 1 Working range of collectors (kalogoriou, 2009)
Type of Solar Collector
Operating Temperature Range (c )
FPC
30-80
ETC
50-200
Absorption chillers are commercially available in a very wide variety. Several companies like Yazaki Energy
Inc., Thermax D. Ltd. etc. offer absorption chillers ranging from 5 to 500 RT capacities which are compatible
with solar panels.
2.2) Experimental Section
Experimental evaluation has been carried out in two phases. In phase-1 actual cooling load required for existing
conditions has been re-evaluated by using HAP. In phase-2 comparison was carried out between operating cost
of conventional and solar powered vapour absorption chiller.
2.3) Cooling load calculation (Phase-1)
HAP 4.3.4 requires three types of detail for its cooling load calculation process for any area.
I.
Weather (Region, location, longitude, summer design DB, winter design WB etc.)
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II.
III.
Spaces (Floor area, ceiling height, walls, windows, doors, infiltration etc.)
Systems (air system type, system components etc.)
Summary of all three parameters where cooling load has been calculated are as listed in table 2, 3 & 4
Table2 Weather input in HAP
Weather
Region
Middle East
Location
Pakistan
City
Lahore/Sheikhupura
Latitude
32 Degree
Longitude
74 Degree
Elevation
712 Ft
Summer Design Db
46 C
Winter Design Db
-5 C
Table 3 Spaces input in HAP
Spaces
Floor Area
5504 Sq ft
Ceiling Height
13 ft
Main Doors Area (qty:02)
51.8 Sq ft
Emergency Doors Area (qty: 04)
21.73 Sq ft
Windows Glass Area (qty:16)
52.5 Sq ft
Wall Thickness
9 in
Occupants
75
Energy Savers
396 (20 watts each)
Total Glass Area on Doors
24 ft 9 in
Table 4 Systems input in HAP
Systems
Air System –
Name/Type
Air Handling Unit (AHU) / TECO/ 4,60,000 BTU/hr qty:02
Equipment Type
Chilled water air handling units
Air System Type
Constant Air Volume(CAV) SINGLE ZONE
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3 Results and Discussions
3.1 HAP Report
Three required parameters (Weather, Space & Systems) were given to HAP software as explained above and an
Air System Sizing Summary was generated which is given below.
Air System Sizing Summary
Air System Information
Air System Name ......................................................... AHU
Equipment Class .................................................. CW AHU
Air System Type ..................................................... SZCAV
Number of zones .................................................................... 1
Floor Area ...................................................................... 5504.0 ft²
Location .............................................. sheikhupura, Pakistan
Sizing Calculation Information
Zone and Space Sizing Method:
Zone CFM ................................. Sum of space airflow rates
Space CFM ............................ Individual peak space loads
Calculation Months ................................................. Jan to Dec
Sizing Data ............................................................. Calculated
Central Cooling Coil Sizing Data
Total coil load ..................................... 36.0 Tons
Total coil load .............................................................. 432.2
Sensible coil load ......................................................... 323.4
Coil CFM at Jul 1500 .................................................. 13826
Max block CFM .......................................................... 13826
Sum of peak zone CFM ............................................... 13826
Sensible heat ratio ........................................................ 0.748
ft²/Ton .......................................................................... 152.8
BTU/(hr-ft²) ................................................................... 78.5
Water flow @ 10.0 °F rise ........................................... 86.50
MBH
MBH
CFM
CFM
CFM
gpm
Load occurs at ............................................................ Jul 1500
OA DB / WB .......................................................... 115.0 / 84.0
Entering DB / WB .................................................... 81.7 / 68.2
Leaving DB / WB ..................................................... 59.4 / 58.2
Coil ADP ............................................................................ 57.0
Bypass Factor ................................................................... 0.100
Resulting RH ........................................................................ 55
Design supply temp. ........................................................... 57.0
Zone T-stat Check ........................................................... 1 of 1
Max zone temperature deviation ......................................... 0.0
°F
°F
°F
°F
%
°F
OK
°F
Central Heating Coil Sizing Data
Max coil load ............................................................... 155.5
Coil CFM at Des Htg .................................................. 13826
Max coil CFM ............................................................. 13826
Water flow @ 20.0 °F drop .......................................... 15.56
MBH
CFM
CFM
gpm
Load occurs at ............................................................. Des Htg
BTU/(hr-ft²) ........................................................................ 28.2
Ent. DB / Lvg DB ..................................................... 69.1 / 79.8 °F
Supply Fan Sizing Data
Actual max CFM ......................................................... 13826 CFM
Standard CFM ............................................................. 13474 CFM
Actual max CFM/ft² ....................................................... 2.51 CFM/ft²
Fan motor BHP .................................................................. 6.21 BHP
Fan motor kW .................................................................... 4.63 kW
Fan static ............................................................................ 2.00 in wg
Outdoor Ventilation Air Data
Design airflow CFM ..................................................... 1400 CFM
CFM/ft² .......................................................................... 0.25 CFM/ft²
CFM/person ..................................................................... 20.00 CFM/pers
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It is evident from central cooling coil sizing data that cooling load on coil is 36 Ton which is
almost 2 times less than installed capacity. Installed capacity of conventional air conditioners as
mentioned before is 76 ton (two units of 38 ton each): additional installed capacity has been
developed to ensure production don’t stop in case of mechanical breakdown of any one of the
two air conditioning units and to compensate for de-rating factor of air conditioners. Thus 36 ton
is taken as theoretical required cooling load for the area under discussion.
3.2 KW annual Energy consumption and operating cost of Conventional Units
Energy consumption and operational cost of one conventional unit over period of one year is
estimated. Annual workings days were calculated by excluding gazetted holidays. Air
conditioner will be operated from April to October. AC operating hours during one day work
from 08 45 AM to 03 00 AM were calculated to be equal to 17 hours/day (excluding work
breaks) Rest of the data is as below
Table 5 Energy consumption and operating cost of Conventional unit
Total working days
296
Ac operating days
192 (April to October)
Ac operating hours/day
17
Annual ac operating hours
17x192= 3264
Annual Energy consumption
*35KWx3264= 1,14,240 KWh
Annual operating cost
**20x 114240 = 2,284,800PKR
Annual maintenance cost
***150,000PKR
Total operating cost
2,434,800 PKR
* 35KW is the input consumed by TECO (Dong Guang) Air conditioning Equipment Co. Ltd.
Model: LP40M1MAR
**Industrial electricity unit rate is 12-15 PKR /KWh during off peak loads and 20-24 PKR / KWh during Peak
loads, calculation has been carried out at a mid value of 20PKR/KWh.
*** Tentative cost of annual maintenance (de scaling & over hauling)
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Ambient Temperature( C)
Cooling Load (RT)
3.3 Ambient Temperature and Cooling load
Fig. 2 Graphical comparison between cooling load and temp
36 ton load has been calculated theoretical cooling load at ambient temperature of 46◦C as shown
in state 3 in graph. Required cooling load depletes as ambient temperature decreases. In state 2
cooling load comes down 19% for a 10◦C fall in temperature and further drops 65% at 26◦C
(cooling load calculated from HAP). Thus it is concluded that at higher temperature proposal for
using solar powered cooling technology will be supported since more sun shine hours will be
available at higher temperature.
KW INPUT
Comp AMP
3.4 Compressor amperes and KW Input from system
Fig. 3 Graphical Comparison between comp amp and KW input
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Each of conventional air conditioning unit consists of three compressors. KW input drawn and
was recorded from system by operating each of them one after another. It is clear from graph that
when all three compressors are in use max KW input are being utilized from system(state 1) and
decreases when compressors are turned off one by one in state 2 and state 3. Thus if compressors
which are the main electricity consumers in complete system are substituted by a source of same
cooling capacity with minimum electricity consumption, a huge amount of saving in terms of
cost and energy can be achieved.
3.5 KW annual Energy consumption and operating cost without compressors of
conventional units.
Each 38 RT conventional air conditioner has 3 compressors and KW consumption of each of
compressor motor is 9.75 KW. Specification of particular unit is as below
Table 6 Input KW without compressor
Capacity
*134.8 KW / 460,000 Btu/h / 38 RT
Compressor motor
*9.75 x 3= 29.25 KW
Input
*35 KW
Input without Compressor for Auxiliaries (Pumps,
Evaporator-condenser fans, electrical panels etc.)
35-29.25= 5.75KW
*Specification of Model: LP40M1MAR, TECO (Dong Guang) Air conditioning Equipment Co. Ltd.
KW energy consumption in this case for annual ac operating hours is shown in table where as in
place of compressors an equivalent capacity of solar powered vapour absorption chiller will be
integrated.
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Table7 KW Energy consumption without compressors
Total working days
296
Ac operating days
192
Ac operating hours/day
17
Annual ac operating hours
17x 192 = 3264
Annual Energy consumption
*5.75 x 3264 = 18768 KWh
Annual operating cost
375,360PKR
Annual maintenance cost
*150,000PKR
Total operating cost
5,25,360 PKR
* as estimated in table 6
3.6 Comparative Analysis
Table 8 Comparative analysis of Conventional Air Conditioner (CAC) & Solar powered Vapour Absorption Chiller
(SVAC)
Calculations
CAC at full load(35KW)
SVAC
Total working days
296
296
-
Ac operating days
192
192
-
Ac operating hours/day
17
17
-
Annual ac operating hours
3264
3264
-
Annual Energy consumption
1,14,240 KWh
18768 KWh
95,481 KWh
Annual operating cost
2,284,800PKR
375,360PKR
1,909,440 PKR
Annual maintenance cost
150,000PKR
150,000PKR
-
Total operating cost
2,434,800 PKR
5,25,360 PKR
1,909,440 PKR (approx)
(5.75 KW)
Saving
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4) Conclusions

Ambient temperature conditions of Pakistan are best for utilization solar cooling
technology.

Implementation of this technology will help in Peak load / demand management since
more solar radiation is available in summer and peak load is also during summer due to
air conditioning.

Substantial KW energy saving can be done as evident from comparative analysis
summary. If KW energy saving is estimated as per concept explained in introduction i.e.
1KW energy saved at end user is equivalent to 5.5 KW of electricity generation at source
then it can be concluded that 95,481KWh saving at end user means 530,450 KWh saving
at generation source. (Operational efficiency 30% & distribution efficiency 60%)

Usage of this technology can give the potential solutions to issues arising from climate
changes like GWP and decrease emissions of GHGs.

Ozone layer depletion by use of CFCs can also be controlled by use of solar cooling
technology

Energy security can be addressed by decrease in dependency of fossil fuel.

Awareness about renewable energy potential

Solar radiation data needs to be thoroughly reviewed and timely updated especially at
major cities of country for better assessment about installation feasibility of solar cooling
technology at a particular place.

Renewable energy resource planning is required at governmental level especially during
future planning to meet energy demands.

Investor friendly policies need to be established by government to bring down initial
capital cost of this technology.
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