MODELLING AND SIMULATION OF
ABSORPTION SOLAR AIR CONDITIONING SYSTEM
Teclemariam NemariamDepartment of Technology,Royal Institiute of Technology,Stockholm, Sweden
email: [email protected]
Aim
• To obtain best system performance of a solar assisted absorption cooling system– Solar fraction– Overall system efficiency– Total cost
• Initial cost•Maintenance cost•Operational cost
Methodology
• TRNSYS simulation program– Transient Systems Simulation Program
• EES– Engineering Equation Solver
System Description
• Energy source Refrigeration Load cycle
System Description
• Solar collector• Thermal storage tank• Auxiliary heater • Absorption
refrigeration chiller with cooling tower
• Building• Diverter• Tee-piece• Relief valve• Piping system
relief valve
storagetank
absorptionchiller
building
tee-piece
heater
collector
sun
diverter
pump
pump
Trnsys Block Diagram
C o llec to rT Y P E 1
T Y P E 7 1
P ressu rere liev e v a lv e
T Y P E 1 3
T h erm a l sto ra g eta n k
T Y P E 3 8
T ee-p ieceT Y P E 1 1 h
A u x ilia ryh ea ter
T Y P E 6
A b so rp tio nch iller
T Y P E 7
B u ild in gT Y P E 1 9
D iv e rte rT Y P E 1 1 b
P u m pT Y P E 3
P u m pT Y P E 3
C o n tro lle rT Y P E 2 b
co o lin gto w er
Absorption Refrigeration System
g e n e ra to rc o n d e n se r
a b so rb e re v a p o ra to r
h e a t e x c h a n g e r
o u tp u th ea t
in p u th ea t
o u tp u th ea t
in p u th ea t
e x p a n s io nv a lv e
p u m p
s tro n gso lu tio n inre fr ig era n t
w ea k so lu tio nin re fr ig era n t
v a lv e
va p o u rre fr ig era n t
vapourrefrigerantP con
P ev
Tev Tcon, Tab Tg
liq u idre fr ig era n t
Absorption Refrigeration System
• Refrigerant– water
• Absorbent– Lithium
bromide
• Stages– Single-effect
• G. temp 80 – 100 C• COP 0.6 – 0.8
– Double-effect• Gen. Temp 100 – 160 C• COP 1.0 – 1.2
– Triple-effect• Gen. Temp 160 – 240 C• COP ABOUT 1.7
Absorption Refrigeration System
pure
refri
gera
nt (x
=1)
pure
refri
gera
nt (x r
)
pure
refri
gera
nt (x p
)Pressure
P 1
P 2
t2 tabs=t1 tgen
evaporator absorber
condenser generator
crys ta llisa tion
Strong refrigerant Poor refrigerant
Absorption Refrigeration System
• Drawbacks– Water
• Temperature greater than zero• High water vapour pressure
– Large volume
– Lithium bromide• Precipitate at low temperature
Building
• Details of a building are:– Location: latitude, longitude, altitude– Type: Office, recidential, hospital,...– Size: volume, area of walls, roof, floor,
windows, door, ..etc – Types of construction materials– Outside design conditions– Inside design conditions– Internal gains
Work done so far
• More than 75% course work• More than 80% literature survey• Modelling and simulation of a
complete system using standard TRNSYS components
Sample Simulation Results
• Solar collectors:– Evacuated collector, high quality flat plate
collector and ordinary flat plate colector
• Storage tank: cylinderical, vertical stand• Heater: gas fired• Single-effect absorption machine
– Refrigerant water and absorbent lithium bromide
– Capacity 24.44 kW
Sample Simulation Results
• Building:– Location: Assab, Eritrea. Latitude 13.07
N, longitude 42.6 E, altitude sea level– Type: two storey office – Size: volume, area of walls, roof, floor,
windows, door, ..etc are given in detail– Types of construction materials– Outside design conditions– Inside design conditions– Internal gains
• Every detail is given
Sample Simulation Results
• System Optimization– e.g. collector slope
0.00E+00
5.00E+07
1.00E+08
1.50E+08
2.00E+08
2.50E+08
0 10 20 30 40 50 60
collector slope (degree)
sola
r en
erg
y g
ain
(kJ
)
ESC DGC SGC
Sample Simulation ResultsSolar fraction as a function of colector area and storage volumee.g. using evacuated collector
0
10
20
30
40
50
60
70
80
10 20 30 40 50 60 70 80
collector area (m 2)
so
lar
fracti
on
(%
)
V1=1.0m3
V2=2.0m3
V3=3.0 m3
V4=4.0m3
V5=5.0m3
Sample Simulation Results• System efficiency as a function of
colector area and storage volume– e.g. using evacuated collector
0
10
20
30
40
50
60
10 20 30 40 50 60 70 80
collector area (m2)
syst
em e
ffic
ien
cy (
%)
V1=1.0m3 V2=2.0m3V3=3.0 m3 V4=4.0m3V5=5.0m3
Sample Simulation Results
• Solar fraction and system efficiency as function of collector area for a given storage volume
0
10
20
30
40
50
60
70
10 20 30 40 50 60 70 80
solar collector (m 2)
eff
icie
ncy
ESC syseff ESC solfr DGC syseffDGC solfr SGC syseff SGC solfr
Sample Simulation Results
• Yearly insolation energy, max possible solar heat gain and cooling load
0.00E+00
5.00E+06
1.00E+07
1.50E+07
2.00E+07
2.50E+07
3.00E+07
3.50E+07
4.00E+07
1 3 5 7 9 11
time (month)
en
erg
y (
kJ)
QIRT ESC DGC
SGC QLOAD
Notice
• The sample simulation result is extracted from a paper presented in the ISES Conference June 14-19 2003 in Götemberg, Sweden.
• If you have more interest please refer the paper.
• Thank you.
