2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
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2. Evaporating temperature were at 75, 80 and 85
o
C.
3. Effectiveness of the heat exchanger (
H
) was 0.85.
4. Isentropic efficiency of pump was 0.8.
5. Isentropic efficiency of turbine was 0.85.
6. Efficiency of generator was 0.8.
7. Electrical power output was 10 kW.
8. Working fluid was
R245fa
and
the
properties
are
based upon REFPROP [10].
Fig. 1. Solar organic Rankine cycle (SORC).
Fig. 2. T-s diagram of the ORC.
Fig. 3. Diagram of the heat exchange process between the hot water and
the working fluid in the evaporator of the ORC.
9. The set pinch-point temperature difference (
PP
T
'
)
was 8
o
C.
10. Temperature difference between
TL
T
and
3
T
was 15
o
C.
C. Economic Analysis
For the economic analysis of the integrated system has
been calculated using the following formula:
2
&
.
invest
o m
CO
net
crf k
k
LEC
k
E
(10)
where
(1 )
(1 ) 1
n
d
d
insurance
n
d
k k
crf
k
k
.
(11)
In Table
II,
the cost
input data
for
the economic analysis
are summarized. Cost of CO
2
reducing is 1,125 Baht/Ton
and for Thailand, the release of CO
2
is 0.75 kg CO
2
/kWh
[2].
TABLE II
C
OST DATA USED FOR THE ECONOMIC EVALUATION OF
SORC
FOR
ELECTRICAL POWER GENERATION
Investment cost
Flat-plate solar collectors (Baht/m
2
)
Evacuated-tube solar collectors (Baht/m
2
)
ORC, generator and heat exchanger (Baht)
Thermal energy storage (Baht/kg)
Land (Baht/m
2
)
Surcharge for construction and engineering (% of
equipment cost)
5,000
5,500
1,000,000
50
100
10
Operating & maintenance (o&m) cost
Person for operating the system (Baht/year)
Person for operating maintenance (Baht/year)
Operating & maintenance equipment cost (% of
investment cost per year)
96,000
96,000
1
Financial parameters
Annual insurance rate,
insurance
k
(%/year)
Real dept interest rate,
d
k
(%)
Cost of CO
2
reducing,
2
CO
k
(Baht/kWh)
Depreciation period ,
n
(year)
0.6
8
0.84375
25
IV. R
ESULTS AND
D
ISCUSSIONS
A. Mass of Water in Thermal Energy Storage
In the calculation, the mass of water in the thermal
energy storage must be high enough for preventing
boiling of water. The mass of water in the thermal energy
storage versus collector area for various values of the
evaporating temperature of the ORC is shown in Fig. 4. It
was noted that the amount of water per unit area of solar
collector, for the evacuated-tube was higher than that of
the flat-plate type due to its higher efficiency.
B. Annual Electricity Generation
Storage
Solar
Collectors
Pump I
Pump II
M
S
, T
S
T
a
Evaporator
Pump IV
Turbine
Internal Heat
Generator
Condenser
Exchanger
2IHE
T
TL
T
FL
1
4IHE
2a
3
4a
W
m
T
S
ORC
m
_
WEV ORC
m
Pump III
Heat
Exchanger
useful
Q
T
3
T
1
T
.
.
3
4
4a
2a
1
2
4HE
2HE
s
T
s
T
3
T
1
1
2IHE 2a
2
4IHE
4a
4
'
T
PP
Input Heat Rate (kW)
Temperature (
o
C)
T
3
T
TL
T
FL
T
2IHE
T
PP_ORC
T
PP_W
