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Investigation of the effect of the water phase in the evaporator inlet on economic performance for an Organic Rankine Cycle (ORC) based on industrial data
Accepted Manuscript Title: Investigation of the effect of the water phase in the evaporator inlet on economic performance for an organic rankine cycle (ORC) based on industrial data Author: N.Filiz Tumen Ozdil, M.Rıdvan Segmen PII: DOI: Reference:
S1359-4311(16)30260-5 http://dx.doi.org/doi: 10.1016/j.applthermaleng.2016.02.117 ATE 7846
To appear in:
Applied Thermal Engineering
Received date: Accepted date:
8-1-2016 28-2-2016
Please cite this article as: N.Filiz Tumen Ozdil, M.Rıdvan Segmen, Investigation of the effect of the water phase in the evaporator inlet on economic performance for an organic rankine cycle (ORC) based on industrial data, Applied Thermal Engineering (2016), http://dx.doi.org/doi: 10.1016/j.applthermaleng.2016.02.117. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1
Investigation of the effect of the water phase in the evaporator inlet on economic
2
performance for an Organic Rankine Cycle (ORC) based on industrial data
3
N.Filiz TUMEN OZDIL1*, M.Rıdvan SEGMEN2
4
Department of Mechanical Engineering, Adana Science and Technology University, 01180 Adana, Turkey
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E-mail address: [email protected], [email protected]
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*Corresponding Author: [email protected]
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Highlights:
1
9 10
Exergoeconomic analysis of an Organic Rankine Cycle (ORC).
11
Determination of exergoeconomic performance for four different water phases in the
12 13
evaporator inlet.
Determination of the components having highest and lowest exergoeconomic factor.
14 15
ABSTRACT
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In this paper, exergoeconomic analysis of an Organic Rankine Cycle (ORC) is presented for a
17
local power plant, located in the southern of Turkey. Specific Exergy Costing Method
18
(SPECOM) is applied using balance and auxiliary equations for the exergoeconomic analysis.
19
The capital investment cost, operating and maintenance costs and total investment cost of
20
ORC steam plant are calculated as 7.43 $/h, 6.69 $/h and 14.12 $/h, respectively. The unit
21
exergy cost and exergy cost of the electricity produced by the turbine are found as 11.05 $/GJ
22
and 14.96 $/h, respectively. In order to show the effect of the water phase in the evaporator
23
inlet on economic performance of the system, exergoeconomic factor of the system is
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calculated for four different water phases. When the evaporator inlet phase is saturated liquid
25
form, better exergoeconomic performance is observed for the system. The highest
26
exergoeconomic factor is observed in the pump because of the lowest exergy destruction rate
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and low total investment cost while the lowest exergoeconomic factor is observed in the
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evaporator due to the highest exergy destruction rate in evaporator. Moreover, payback period
29
assessment is calculated as 3.27 years for the ORC power plant.
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Key Words: Exergoeconomic analysis, Exergy, Heat recovery, Organic Rankine Cycle,
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SPECO Nomenclature c
unit exergy cost ($/GJ)
Subscripts
Ċ
exergy cost ($/h)
Zt
total investment cost
ĊD
exergy Destruction cost rate
cond
Condenser
ex
specific exergy (kJ/kg)
Ċturb
exergy cost due to work at turbine
ĖxD
exergy Destruction (Kw)
Ċpump
exergy cost due to work at pump
f
exergoeconomic factor
cons
Consumed
h
specific enthalpy (kJ/kg)
cyc
cycle
ṁ
mass flow rate (kg/s)
dest
Destruction
P
pressure (bar)
evp
Evaporator
pp
pinch point
rate of heat transfer (kW) s
specific entropy (kJ/kg K)
rej
rejection
T
temperature (K)
sat
Saturated
W
rate of work (kW)
sup
Superheated
2
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Ż
hourly levelized cost of investment $/h
comp
compressed
0
reference state
turb
Turbine
r
refrigerant
Greek symbols
w
water
Σ
total
Abbreviation
η1,cyc
first law efficiency
CI
capital investment
η2,cyc
second law efficiency
CR
cost rate
φ
CRF
capital recovery factor
OM
operating and maintenance
ORC
organic Rankine Cycle
PEC
purchased equipment cost
operating and maintenance cost factor
SPECOM specific exergy costing method 32 33
1. Introduction
34
Energy can not be generated or consumed by itself so the energy conservation process
35
become the vital concept in the world. The waste heat recovery is the most suitable source for
36
the energy conservation due to lack of the fossil fuels and global warming. The waste heat
37
recovery process helps the energy conservation and decrement of the thermal pollution.
38
Although the steam turbine is the most common technology in the energy conversion process,
39
due to necessity of high operational temperature and pressure, it is not suitable for low
3
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temperature and pressure condition. Organic Rankine Cycle is generally preferred for the
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processes having low temperature like T< 150oC. This process is called as Organic Rankine
42
Cycle owing to usage of the organic fluid as working fluid instead of water and high pressure
43
steam.
44
Exergy is the measurement of the maximum useful work that can be obtained from the
45
system. Therefore, it has become more important research topic than energy in order to
46
determine the useful work. Because of the irreversibility, exergy can be consumed or
47
destroyed in the processes. The consumption of the exergy rate in a process is directly related
48
with the entropy generation. The exergoeconomic analysis is a method that comes out with
49
the combination of both the exergy and economic analysis. The exergoeconomic method has a
50
huge potential to optimize the systems using effectiveness of the energy and exergy. The
51
overall aims of the exergoeconomic analysis are listed as below;
52
i.
detailed analysis of the cost formation and the cost flow in a system
53
ii.
demonstration of the specific variables for each components in a convenient way
54
iii.
indication of the relationship between the cost based performance and the
55 56
thermodynamic performance iv.
optimization of the whole system performance in terms of economic structure
57
There are a number of exergoeconomic methods in thermodynamics such as
58
Thermoeconomic Functional Analysis (TFA) [1,2], Exergy Economic Approach (EEA) [3],
59
Last-In-First-Out Approach (LIFOA) [4], Exergetic Cost Theory (ECT) [5], Structural
60
Analysis Approach (SAA) [6], Engineering Functional Analysis (EFA) [7], First
61
Exergoeconomic Approach (FEA) [8], and Specific Exergy Costing Method (SPECOM) [9].
62
In this paper, SPECO method is applied in order to understand the cost formation process of
63
the ORC system. The traditional SPECO method consists of the below three steps;
64
i.
Step 1: identification of the exergy streams 4
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ii.
Step 2: definition of the fuel and product
66
iii.
Step 3: forming the cost equations
67
There are a lot of studies about ORC for the power generation from the waste heat
68
recovery. In research of Kaşka [10], the energy and exergy analyses of a steel plant were
69
performed using actual plant data. He concluded that the exergy destruction rate was listed
70
from higher to lower as evaporator, turbine, condenser and pump. Moreover, it was observed
71
that the evaporator pressure had an important effect on the energy and exergy efficiency.
72
Ozdil et al. [11] presented a thermodynamic analysis of an ORC in a local power plant.
73
Furthermore, the relationship between the pinch point and the exergy efficiency was
74
observed. The energy and exergy efficiencies of the ORC were calculated as 9.96% and
75
47.22%, respectively for saturated liquid form. Moreover, exergy destruction and exergy
76
efficiencies of components and overall system were calculated for different water phases. The
77
analyses showed that evaporator had an important effect on the system efficiency depending
78
on the exergy rate. Esen et al. [12] demonstrated the energetic and exergetic performance of
79
ground coupled heat pump system as a function of depth trenches for heating season. They
80
performed horizontal ground heat exchangers (HGHEs) buried 1 m and 2 m depth trenches.
81
The energy efficiencies of ground coupled heat pump systems for horizontal ground heat
82
exchangers (HGHE1 and HGHE2) were obtained to be 2.5 and 2.8. The exergetic efficiencies
83
of the heat pump system were found as 53.1% and 56.3% for HGHE1 and HGHE2.
84
Furthermore, the irreversibility of HGHE2 was less than that of about 2.0% in comparison
85
with HGHE1. The results showed that the energetic and exergetic efficiencies of the system
86
increased with increasing the heat source temperature for heating season. The increment of
87
the reference environment temperature caused the decrement of the exergy efficiency in
88
HGHE1 and HGHE2.
5
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There are limited studies about exergoeconomy. Quoilin et al. [13] focused on a
90
thermodynamic and thermoeconomic optimization of a small scale ORC which is used in
91
waste heat recovery application. A resized model of the ORC was proposed in order to predict
92
the cycle performance with different working fluids and different components sizes. The
93
optimum economical cost was obtained as 2136 €/kW for n-butane while the optimum
94
thermodynamic performance was obtained as 5.22% for the same fluid. Khaljani et al. [14]
95
presented a thermodynamic, exergoeconomic and environmental assessment of a cogeneration
96
of the heat and power cycle. The results showed that the most exergy destruction rate took
97
place in the combustion chamber, and it was followed by heat recovery steam generator and
98
gas turbine. The exergoeconomic factor was 10.59% for the whole cycle. And, it indicated
99
that the exergy destruction cost rate was higher than capital investment cost rate. Moreover, in
100
order to assess the effects of the design parameters on the objective functions, a parametric
101
study was conducted. The results revealed that the increment in pressure ratio and isentropic
102
efficiency of air compressor and gas turbine improved the thermodynamic performance of the
103
system. However, the more increment of the parameters yielded worse in the total cost rates.
104
Wang et al. [15] studied a theoretical model on the payback period of an ORC system for
105
recovering low-grade waste heat of flue gas. Based on the minimum payback period principle,
106
a comprehensive internal parameter optimization was carried out in their study. Moreover, the
107
effects of external parameters on the payback period were analyzed and a new criterion of
108
screening working fluids was proposed. Their results showed that the payback period of the
109
ORC system decreased first than increased as the evaporation temperature, condensation
110
temperature, and the pinch point temperature differences increased in the evaporator and
111
condenser.
112
Hajabdollahi et al. [16] presented four different analyses including energy, efficiency,
113
economic and environment for equipment selection and waste heat recovery on a diesel 6
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114
engine using Organic Rankine Cycle. The design parameters were selected as nominal
115
capacity of diesel engine, diesel operating partial load, evaporator pressure, condenser
116
pressure and refrigerant mass flow rate. Four different refrigerants such as R123, R134a,
117
R245fa and R22 were selected and employed as working fluids. The results showed that the
118
best working fluid was R123 in both of the economical and thermodynamic point of view,
119
while the worst working fluid was R22. Furthermore, R245fa showed similar results with
120
R123 in terms of efficiency and total annual cost. They concluded that R245fa seemed as a
121
good backup for R123. They concluded that non-dimensional cost didn’t effect optimization
122
of the thermal efficiency. Li [17] evaluated thermoeconomic performance of Kalina and CO2
123
transcritical power cycle for low temperature geothermal sources. He crosschecked for the
124
mentioned two cycles using six parameters which were net power output, thermal efficiency,
125
exergy efficiency, total heat exchanger area, cost per net power (CPP) and the percentages in
126
the total cost (PHC). They represented that Kalina cycle had a higher thermal efficiency and
127
net power output. On the other hand, Kalina cycle had less exergy efficiency than that of the
128
CTPC. Desai and Bandyopadhyay [18] compared the organic Rankine and steam Rankine
129
cycles in terms of termoeconomic point of view. They suggested selection methodology based
130
on thermoeconomic analysis for working fluids of power generating cycles. They concluded
131
that the condition of equality of levelized cost of energy (LCOE) was one of the most
132
important items for the working fluid selection. Qureshi [19] conducted thermoeconomic
133
optimization of power systems using finite thermal capacitances for design situation. They
134
used internal irreversibility multiplier which could disregard some details. They observed
135
changing in the cycle thermal efficiency for endoreversible case. Park et al. [20] performed
136
thermo-economic analysis of 300 MW class IGCC power plant using ASPEN Plus®. They
137
calculated the levelized cost of electricity (LCOE) using the total revenue requirement (TRR)
7
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method. They observed that reduction of the LCOE led to improved system efficiency
139
because of lower carrying charge, O&M cost and fuel cost.
140
Esen and Yuksel [21] investigated a greenhouse that heated using solar, biogas and ground
141
energy in Elazig, city of Turkey. They constructed a greenhouse with dimensions 6 m x 4 m x
142
2.10 m and required heating load was determined. In order to test the different energy sources,
143
three different heat pump heating system with horizontal slinky ground heat exchanger were
144
designed and built. Moreover, the effects of operating parameters and climatic conditions on
145
the system performance parameters were examined. They concluded that solar energy can be
146
stored underground and used to increase soil temperature. In addition, it was observed to be
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an advantage heating the greenhouse beside reactor for energy savings in heating process
148
using biogas. According to study of Esen et al. [22], the performance experiments and
149
economic analysis of a horizontal ground source heat pump system were performed. The
150
horizontal ground space heat pump system, which attached to a test room, was designed and
151
built for space heating. The performance was evaluated under real operating conditions.
152
Moreover, a detailed cost analysis was applied and payback period was determined. The
153
annualized life cycle cost method was used in the economical analysis, in order to compare
154
the ground source heat pump system with conventional heating methods. The results showed
155
that the ground source heat pump system has some economic advantages compared with other
156
conventional heating methods but it was not an economic choice over the natural gas. Esen et
157
al. [23] examined the differences between a ground coupled heat pump system and an air
158
coupled heat pump system, in their study. The investigated systems were attached to a test
159
room in Firat University and they were designed and built for space cooling. The
160
performances of the ground coupled heat pump system and the air coupled heat pump system
161
were analyzed, experimentally for cooling season from June to September. The results
162
showed that the COP of the ground coupled heat pump system were found as 3.85 and 4.26 8
Page 8 of 31
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for horizontal ground heat exchanger in the different trenches at 1 m and 2 m depths. The
164
COP of the air coupled heat pump system was obtained as 3.17. They concluded that the
165
system parameters affected the performance of the system and the ground coupled heat pump
166
systems were more preferable in comparison with the air coupled heat pump systems in terms
167
of space cooling in economic point of view.
168
Even though, there are a few studies addressing the exergoeconomic analysis of the
169
power generation plants, detailed discussions and analysis of the relationship between the
170
exergy and economic sustainability of the ORC system for the real industry are necessary. In
171
this study, an extensive exergoeconomic analysis is carried out for an ORC which generates
172
electricity using waste heat recovery in a local steel plant. Based on the data obtained from the
173
thermodynamic analysis, the exergoeconomic analysis and the exergetic performance
174
assessment are performed for each component of the ORC system and exergy-cost relations
175
are resolved in parts.
176
The novelties of this study can be listed as below;
177
i.
This study presented an extensive exergoeconomic analysis for a running
178
Organic Rankine Cycle (ORC) plant, located in southern of Turkey. Different
179
from studies in literature; economic performance comparison was examined for
180
four different water phases in the evaporator inlet (sat. liq., X=0.3, X=0.7 and sat.
181
vapor) in order to show the effect of the different water phases in the evaporator
182
inlet on economic performance.
183
ii.
Moreover, the purchased equipment cost (PEC), the cost rate (CR), the levelized
184
capital investment (ZiCI), operating and maintenance costs (ZiOM) and total
185
investment costs (ZiT) of the system components are calculated. In order to show
9
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186
the exergoeconomic performance of the system components, exergy destruction
187
cost rates and the exergoeconomic factor rates of the components are graphed.
188
iii.
Furthermore, the payback assessment analysis is applied on the system to obtain
189
the payback time of the ORC steam plant for saturated liquid in the evaporator
190
inlet phase.
191
2. System description
192
In this study, the exergoeconomic analysis is performed for the running ORC system
193
which is located in Adana, Turkey. The ORC produces electricity using waste heat in low
194
temperature in order to reduce the operating costs of the company. The investigated system
195
has 260.4 kW capacity and specifications of the system components are demonstrated in
196
Table 1.
197
The system involves an evaporator, a condenser, a turbine and a pump as subcomponent.
198
The generator, heating and cooling water collectors are accepted as the auxiliary components.
199
The working fluid used in the ORC cycle is R245fa (Pentafluoropropane) which has good
200
thermodynamic properties such as low specific heat and viscosity, low toxicity, low ozone
201
depletion potential, low flammability. Most of the ORC systems use R245fa as the working
202
fluid which has moderate global warming potential of 1030, power density, and lower critical
203
pressure at higher temperature [24]. Owing to the above mentioned properties and the
204
favorable economic conditions, the R245fa is a convenient option for working fluid. The
205
properties of the R245fa are shown in Table 2.
206
The schematic diagram of the ORC system is illustrated in Fig. 1. In the system, working
207
fluid is pumped, firstly; then low pressure fluid is compressed to high pressure fluid by a
208
pump as can be seen in Fig. 1. (state 5 to 6). Later, the high pressure fluid enters and passes
209
through the evaporator. In the evaporator, the high pressure fluid (6) has become heated and
210
pressurized vapor (3) using the heat capacity of inlet water (state 1 to 2). After that the heated
10
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and pressurized vapor enters to the turbine. While it leaves from turbine as low pressure
212
vapor, it leads to electricity generation (state 3 to 4). Lastly, the low pressure vapor goes
213
through the condenser, and the working fluid leaves from the condenser as saturated liquid
214
(state 4 to 5) and the cycle continues so on.
215
Some amounts of data are measured from the system and the remaining data are obtained
216
from the computer aided control panel directly. Dead state conditions of the working fluid
217
(R245fa) and the water are accepted as 1 bar and 25oC. Before the performing the analysis,
218
the first step is to measure the mass flow rate of the condenser cooling water (7). Mass flow
219
rate of the condenser cooling water is measured by GE-PT878 which is ultrasonic flowmeter
220
equipment ranges from ½”-7,6mm with ± 1% accuracy. Mass flow rate of the R245fa is
221
calculated from the mass and energy balance equations from the condenser cooling water and
222
the mass flow rate of the evaporator inlet water is estimated from the first law of the
223
thermodynamic. The water collectors on the system are placed in the evaporator and
224
condenser inlet and outlet. Pressure and temperature measurement devices are put on
225
collectors in order to measure the thermophysical properties of the water and the working
226
fluid.
227 228
3. Analysis
229
The aim of this study is to apply an exergoeconomic analysis in order understand the
230
connection between the cost performance and the thermodynamic performance of the ORC
231
system. The exergoeconomic balance equations are implemented on the ORC system using
232
the data obtained from the first and second law of thermodynamics.
233
The first law of the thermodynamics is explained as the conservation of the energy. The total
234
energy, which is being constant in the processes, can be converted or transferred. The second
235
law of thermodynamics claims that energy has quality as well as quantity. The second law of 11
Page 11 of 31
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thermodynamics is applied to determine the quality as well as the degree of energy reduction
237
during a process. The second law refers to the change of the quality of the energy during the
238
phase change in the processes. The maximum useful work in a process is called as exergy.
239
The higher exergy destruction rate means lower useful energy conversion in the processes.
240
The following assumptions were made in this study;
241
Pressure drops, potential and kinetic energy changes on the system are neglected.
242
The system operates in a continuous steady state flow process.
243
The system is adiabatic which means there is no heat loss.
244
The exergy balance and auxiliary equations for the each component are shown in Table 3.
245
The thermoeconomic analysis combines exergy and economic analyses to provide
246
information that is not accessible with general energy and exergy analysis. In general, for the
247
economic analysis, a cost balance can be formulated for the steady state system for each
248
control volume i:
249
∑ Ċin,i + ŻiT = ∑ Ċout,i + ĊiW + ĊiQ
(1)
250
Ċi = ciExi
(2)
251
ĊiW = ciWi
(3)
252
ĊiQ = ciExiQ
(4)
253
ŻiT = ŻiCI + ŻiOM
(5)
254
where Ċi, ĊiW, ĊiQ are the exergy costs of the flow, power and heat, respectively; ci, ciw, ciq
255
are the unit exergy costs of the flow, power and heat, respectively; Exi, Wi and ExiQ are the
256
exergy of the flow, power and heat entering and leaving control volume; ŻiCI, ŻiOM and ŻiT are
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the hourly levelized costs of the capital investment, operating and maintenance and the total
258
cost of equipment inside the control volume.
259
The hourly levelized cost approach is used to calculate ŻiCI with using equations below:
260
The capital recovery factor (CRF):
261
CRF = (i(i+1)n)/((i+1)n-1)
262
The hourly levelized capital investment cost of the ith component at the ŻiCI :
263
ŻiCI = (CRF/τ)PECi
264
The cost rate of the subsystems CRi:
265
CRi = PECi / ∑ PECORC
266
Where i, n, τ and PEC are the interest rate, the life time of the plant, total annual number of
267
hours of the system operated at a full road and the purchased equipment cost, respectively.
268
For this system i, n and τ are taken as 0.1, 20 years and 7,900.
269
ŻiOM = ŻiCI φ
270
Where the maintenance and operating costs are considered with the factor φ = 0.9 for the
271
steam plant and its auxiliary components.
272
The total investment price of the examined ORC power plant is 500,000 $ and the
273
subsystem’s costs are calculated with the cost rates given by the manager of the plant.
274
The unit exergy cost of the electricity is;
275
cW = PrW/(ER 3,600 10-6) (s/h) (GJ/kJ)
(6)
(7)
(8)
(9)
(10)
13
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276
Where PrW and ER are called as the electricity sell price in the Turkish Lira (TL) and the
277
exchange rate (TL/$), respectively [26]. The unit exergy cost of the heating source and the
278
working fluid are assumed to be 1.3$/GJ [27] and 15.6$/GJ [28] respectively.
279
The aim of the exergoeconomic analysis is to understand the cost formation process and
280
calculations of the cost rate for each product on the steam plant. In this study, analyses are
281
performed for four different water phases of evaporator inlet in order to investigate the effect
282
of water phase on exergoeconomic performance. These conditions can be listed as;
283
i.
Saturated liquid,
284
ii.
Water mixture (quality 0.3),
285
iii.
Water mixture (quality 0.7),
286
iv.
Saturated vapor phase of the evaporator inlet.
287 288
The given exergoeconomic parameters are taken into consideration to understand the frame of the cost and exergy flows:
289
i.
The average unit cost of the fuel, cf,i,
290
ii.
The average unit cost of the product,cp,i,
291
iii.
The cost rate of the exergy destruction, cD,i,
292
iv.
The exergoeconomic factor, fi,
293
fi = ZiT / (ZiT + (cf,i (ExD,i + ExL,i)))
(11)
294
The exergoeconomic factor provides comprehensive information regarding the
295
combination of the non-exergy costs (capital investments, operating and maintenance costs),
296
the exergy destruction and the exergy loss. The exergetic fuel is defined as the consumed 14
Page 14 of 31
297
resource for generating product in the ORC system. The cost rate of the exergy destruction
298
shows how much $/h can be destructed during the operation. In order to increase the system
299
effiency, the pinch point temperature is found as 105.2oC and ΔTpp is found as 6.2oC. The
300
result is similar with Kaşka [10] and Ozdil [11].
301
4. Results and Discussions
302
The ORC produces electricity using waste heat with low temperature. In this study, the
303
extensive exergoeconomic analysis is performed using the first and second laws of the
304
thermodynamics and economic parameters in order to observe the relationship between
305
thermodynamics and economic performance of components for the running ORC power plant.
306
Furthermore, the effect of the different water phases in the evaporator inlet on the economic
307
performance of the system is examined in this study. Four different water phases in the
308
evaporator inlet are examined. When the water phase in the evaporator inlet is saturated liquid
309
in condition-1, the exergy efficiency of the system is calculated as 38.79%. In condition-2,
310
water phase in the evaporator inlet is assumed as saturated water mixture which is quality is
311
0.3. The exergy efficiency of the system is calculated as 34.69% for condition-2. In condition-
312
3, water phase in the evaporator inlet is assumed as saturated water mixture which is quality is
313
0.7. The exergy efficiency of the system is calculated as 34.29% for condition-3. Moreover, in
314
condition-4, water phase in the evaporator inlet is assumed as saturated vapor. The exergy
315
efficiency of the system is calculated as 34.16% for condition-4. The exergy destruction rates
316
and the exergy efficiencies of the all system components are shown in Table 4 for all
317
conditions. Based on the Table 4, the exergy efficiencies of evaporator, turbine, condenser
318
and pump are calculated as 72.55%, 69.7%, 28.69% and 85.2%, respectively for condition-1.
319
Exergy loss in the cycle is sum of the total exergy destruction and exergy transferred to the
320
condenser cooling water. In other words, exergy transfer rate from the R245fa to the
321
condenser cooling water is assumed to be part of the exergy destruction. As a result, exergy 15
Page 15 of 31
322
loss is the exergy rate extracted from the evaporator. Unlike exergy loss, exergy destruction
323
means internal losses by the components because of the irreversibility. The major exergy
324
destruction occurs in the evaporator with about 178.18 kW and followed by the turbine,
325
condenser and pump for condition-1. These results are compatible with Kaşka [10] and
326
Khaljani [14]. The exergy transfer rate from the R245fa to the condenser cooling water is
327
assumed to be part of the exergy destruction in this study.
328
The purchased equipment cost, the cost rate, the hourly levelized capital investment cost,
329
operating and maintenance cost and the total investment costs of the ORC power plant with its
330
components are shown in Table 5. The capital investment cost, operating and maintenance
331
costs and total investment cost for ORC power plant are found as 7.434 $/h, 6.69 $/h and
332
14.124 $/h, respectively. The distribution of the cost rates, the purchased equipment costs and
333
the total investment costs of the components are also presented in Figs. 2-3-4, respectively. As
334
can be seen in Figs. 2-3-4, the highest cost rate, the highest purchased equipment cost and the
335
highest total investment cost values are found as 0.6, 300,000 $ and 8.47 $/h for the turbine
336
due to the high purchased equipment-total system cost ratio. The cost balance equations are
337
demonstrated in Table 6. Moreover, unit exergy cost and exergy cost of the components for
338
the ORC power plant are shown in Table 7 and 8 for conditions 1-2-3-4 with respect to the
339
state numbers as can be seen in Fig. 1. Based on the cost balance equations (Table 6), the unit
340
exergy cost and exergy cost of the electricity produced by the turbine are calculated as 11.05
341
$/GJ and 14.96 $/h for condition-1, 11.22 $/GJ and 15.2 $/h for condition-2, 11.25 $/GJ and
342
15.24 $/h for condition-3 and 11.3 $/GJ and 15.28 $/h for condition-4, respectively.
343
The exergy destruction cost rates of the system components are demonstrated in Fig. 5 for
344
condition-1. The evaporator and the turbine have the highest exergy destruction cost rate
345
because of their higher exergy destruction rate and higher cost of fuel values. It is consistent
346
with study of Khaljani [14]. Fig. 6 shows the effect of the exergy destruction cost rate for four
16
Page 16 of 31
347
different conditions. The lowest exergy destruction cost rate is calculated for condition-1
348
because condition-1 has the lower exergy destruction rate than that of other conditions.
349
Furthermore, the increment of the exergy destruction causes high the exergy destruction cost
350
rate. The exergoeconomic factors of the system subcomponents for condition-1 are illustrated
351
in Fig. 7. The results showed that the highest exergoeconomic factor is found in pump like
352
study of El-Emam [29] because of it’s low exergy destruction rate and low total investment
353
cost value. Moreover, the lowest exergoeconomic factor is calculated for the evaporator
354
because of the high exergy destruction rate. When compared with the study of Shokati N. et
355
al [30], the similar results are observed. The exergoeconomic factors of the system for the
356
condition 1-2-3-4 are calculated as 65.8%, 64.23%, 64.16% and 64.1%, respectively as shown
357
in Fig. 8. When the water phase changes from condition-1 to condition-4, exergy destruction
358
cost rates of the systems and evaporators increases gradually.
359
exergoeconomic factor of the evaporator and the entire system slightly decreases due to the
360
increment of the exergy destruction cost rate. Evaporator is the most important component in
361
terms of exergoeconomic point of view. In order to decrease the exergy destruction in the
362
evaporator, heat input can be decreased. Namely, condition-1 is more efficient than condition-
363
1-2-3 because heat input is lower from that of the other conditions. When the evaporator inlet
364
phase is saturated liquid form, better exergoeconomic performance is observed for the system.
365
5. Payback Period Assessment
Furthermore, the
366
Payback period is determined as the required time to recover an investment. The payback
367
period of an investment or project is an important parameter in order to evaluate the recycling
368
time of the system. Namely, longer payback periods are not desirable for investment
369
positions.
370
PEC ($) = 500,000 $
17
Page 17 of 31
371
Capacity of the turbine: 260.4 kWh
372
Operation time: 7900 h/y
373
Utility rate: 0.1 $
374
Operational and maintenance cost: 52,851 $/y
375
Full capacity electricity generation: (259kWh) x (7900h/y) = 2,057,160 kWh/y
(A.1)
376
Full capacity gross return: (2,057,160kWh/y) x (0.1$) =205,716$ kWh/y
(A.2)
377
Full capacity net return: (205,716$) – (52,851$) = 152,865 $
(A.3)
378
Full capacity payback years: PEC / Full capacity kW/y
379
500,000$ / 152,865$ = 3.27 y
(A.4)
380
According to calculations; initial investment can pay for itself 3.27 years after. These
381
calculations and recommended results can be used for continuing investments and it gives an
382
idea for setting up ORC power plant.
383
6. Conclusions
384
This study presents a detailed exergoeconomic analysis of a running ORC cycle in steel
385
industry. Exergoeconomic balance equations are solved using the results obtained from the
386
first and second laws of thermodynamics analyses. The major exergy destruction occurs in the
387
evaporator with about 178.18 kW and followed by the turbine, condenser and pump for
388
condition-1. The major reasons of the inefficiency in the evaporator are high heat input,
389
namely water phase of the evaporator inlet. The exergy efficiencies of the ORC power plant
390
for the condition 1-2-3-4 are calculated as 38.79 %, 34.69%, 34.29% and 34.16%
18
Page 18 of 31
391
respectively. The exergy destruction rates of the condition 1-2-3-4 are calculated as 399.13
392
kW, 444.82 kW, 484.15 and 487.05, respectively for the overall system.
393
The exergy cost and unit exergy cost values are calculated in order to perform the
394
exergoeconomic analysis. The turbine and evaporator have the highest cost rate value; so that,
395
these components are the most important parts of the system. The capital investment cost,
396
operating and maintenance costs and total cost of the ORC power plant are found as 7.43 $/h,
397
6.69 $/h and 14.12 $/h, respectively. For the condition-1, 260.4 kW power can be generated in
398
the system that temperature and flow rate of the waste heat source are 125oC and 17.74 kg/s,
399
respectively. This means 4.07x10-3 kW electricity generation per kilogram of the heat source.
400
Exergoeconomic cost analysis shows that the exergy cost of the heat source and exergy cost
401
of the electricity produced by the turbine are 4.83 $/h and 14.96 $/h, respectively for
402
condition-1. On the other hand, the exergy cost of the heat source and exergy cost of the
403
electricity produced by the turbine are calculated as 3.76 $/h and 15.20 $/h for condition-2,
404
3.61 $/h and 15.24 $/h for condition-3 and lastly 3.57 $/h and 15.28 $/h for condition-4,
405
respectively. For the all conditions, the evaporator component has the lowest exergoeconomic
406
factor rate due to the high exergy destruction rate while the pump has the biggest
407
exergoeconomic factor rate because of the low total investment cost and the low exergy
408
destruction rate. The exergoeconomic factors of the system for the condition-1-2-3-4 are
409
calculated as 65.8%, 64.2%, 64.16% and 64.11% respectively. When the condition-1 is
410
compared with the other conditions, the highest exergoeconomic factor is observed
411
forcondition-1. Namely, low heat input causes better efficiency and economic performance.
412
Based on the observations, the evaporator inlet phase has important effect on economical
413
performance of the system. When the evaporator inlet phase is saturated liquid form, better
414
exergoeconomic performance is observed for the system. In addition, the payback calculations
415
show that the payback period of the ORC power plant is calculated as 3.27 years. 19
Page 19 of 31
416
References
417
[1] Frangopoulos, C.A. Thermoeconomic functional analysis: a method for optimal design or improvement of
418
complex thermal systems. PhD Thesis. Georgia Institute of Technology, Georgia, USA, 1983
419
[2] Frangopoulos C.A. Thermoeconomic functional analysis and optimization. Energy 1987; 12(7): 563- 571.
420
doi:10.1016/0360-5442(87)90097-1
421
[3] Gaggioli, R.A, Wepfer, W.J. Exergy economics. Energy 1980; 5:823-38. doi:10.1016/0360-5442(80)90099-7
422
[4] Tsatsaronis, G., Lin, L., Pisa, J. On exergy costing in exergoeconomics. J. Energy Resour. Technol
423
1993; 115(1): 9-16. doi:10.1115/1.2905974
424
[5] Valero, A., M. A. Lozano, and M. Muñoz. "A general theory of exergy saving. I. On the exergetic
425
cost." Computer-Aided Engineering and Energy Systems. Second Law Analysis and Modelling, R. Gaggioli,
426
ed 3 (1986): 1-8.
427
[6] Valero, A., Torres, C., Serra, L., & Lozano, M. A. A General Theory of Thermoeconomics, Parts I and II,
428
ECOS 92 Ed. By A. Valero and G. Tsatsaronis, Zaragoza. ASME Bok, 1992; (100331), 147-154.
429
[7] Von Spakowsky, M.R. A Practical generalized analysis approach to the optimal thermoeconomic design and
430
improvement of real-world thermal systems. PhD Thesis, Georgia Institute of Technology, Georgia, USA, 1986.
431
[8] Tsatsaronis G, Winhold M. Exergoeconomic analyses and evaluation of energy conversation plants. Energy
432
1985; 10:69-94. doi:10.1016/0360-5442(85)90020-9
433
[9] Lazzaretto, A., and Tsatsaronis, G. SPECO: A systematic and general methodology for calculating
434
efficiencies and costs in thermal systems. Energy 2006; 31:1257-1289. doi:10.1016/j.energy.2005.03.011
435
[10] Kaşka Ö. Energy and exergy analysis of an organic Rankine for power generation from waste heat recovery
436
in steel industry. Energy Convers and Manage 2014; 77:108-117. doi:10.1016/j.enconman.2013.09.026
437
[11] Tumen Ozdil NF, Segmen MR, Tantekin A. Thermodynamic analysis of an Organic Rankine Cycle (ORC)
438
based on industrial data. Appl Therm Eng 2015; 91:43-52. doi:10.1016/j.applthermaleng.2015.07.079
20
Page 20 of 31
439
[12] Esen H, Inalli M, Esen M, Pihtili M. Energy and exergy analysis of a ground-coupled heat pump system
440
with two horizontal ground heat exchangers, Building and Environment, 2007;42(10):3606-3615.
441
doi:10.1016/j.buildenv.2006.10.014
442
[13] Quoilin S., Declaye S., Tchanche BF., Lemort V. Thermo-economic optimization of waste heat recovery
443
Organic Rankine Cycles. Appl Therm Eng 2011; 31:2885-2893. doi:10.1016/j.applthermaleng.2011.05.014
444
[14] Khaljani M, Saray R, Bahlouli K. Comprehensive analysis of energy, exergy and exergo-economic of
445
cogeneration of heat and power in a combined gas turbine and organic Rankine cycle. Energy Convers and
446
Manage 2015; 97:154-165. doi:10.1016/j.enconman.2015.02.067
447
[15] Wang X., Li X., Li Y., Wu C. Payback period estimation and parameter optimization of subcritical organic
448
Rankine cycle system for waste heat recovery, Energy 2015; 88:735-74. doi:10.1016/j.energy.2015.05.095
449
[16] Hajabdollahi Z., Hajabdollahi F., Tehrani M., Hajabdollahi H.
450
optimization of Organic Rankine Cycle for diesel waste heat recovery, Energy 2013; 63:142-151.
451
doi:10.1016/j.energy.2013.10.046
452
[17] Li S, Dai Y. Thermo-economic comparison of Kalina and CO2 transcritical power cycle for low
453
temperature
454
doi:10.1016/j.applthermaleng.2014.04.067
455
[18] Desai NB, Bandyopadhyay S. Thermo-economic analysis and selection of working fluid for solar organic
456
Rankine cycle. Appl Therm Eng 2016;95:471-481. doi:10.1016/j.applthermaleng.2015.11.018
457
[19] Qureshi BA. Thermoeconomic considerations in the allocation of heat transfer inventory for irreversible
458
power systems. Appl Therm Eng 2015;90:305-311. doi:10.1016/j.applthermaleng.2015.06.104
459
[20] Park SH, Chung SW, Lee SK, Choi HK, Lee SH. Thermo-economic evaluation of 300 MW class integrated
460
gasification combined cycle with ash free coal (AFC) process. Appl Therm Eng 2015;89:843-852.
461
doi:10.1016/j.applthermaleng.2015.06.066
462
[21] Esen M, Yuksel T. Experimental evaluation of using various renewable energy sources for heating a
463
greenhouse, Energy and Buildings, 2013;65:340-351. doi:10.1016/j.enbuild.2013.06.018
464
[22] Esen H, Inalli M, Esen M. Technoeconomic appraisal of a ground source heat pump system for a heating
465
season
466
doi:10.1016/j.enconman.2005.06.024
in
geothermal
eastern
sources
Turkey,
in
Energy
China.
Convers
Appl
and
Thermo-economic environmental
Therm
Manage
Eng
2014;70:139-152.
2006;47(9-10):1281-1297.
21
Page 21 of 31
467
[23] Esen H, Inalli M, Esen M. A techno-economic comparison of ground-coupled and air-coupled heat pump
468
system for space cooling, Building and Environment, 2007;42(5):1955-1965.doi:10.1016/j.buildenv.2006.04.007
469
[24] Cool prop web-site. www.coolprop.org/v4/Fluids/R245fa. Accessed June 2015
470
[25] A. Durmaz, R. Pugh, S¸ Yazıcı, K. Erdogan, A. Kosan. Novel application of Organic Rankine Cycle (ORC)
471
technology
472
www.tmeic.com/Repository/ Media/AIST_Toscelik_ORC_v9.pdf.
473
[26] Tumen Ozdil N.F., Tantekin A. Exergoeconomic analysis of a FBCC steam power plant. Thermal Science.
474
2016; (Accepted)
475
[27] Shokati N, Ranjbar F, Yari M. Exergoeconomic analysis and optimization of basic, dual-pressure and dual-
476
fluid ORCs and Kalina geothermal power plants: A comparative study. Renew Energy 2015; 83:527-542.
477
doi:10.1016/j.renene.2015.04.069
478
[28] Yilmaz C, Kanoğlu M, Abusoğlu A. Thermoeconomic cost evaluation of hydrogen production driven by
479
binary geothermal power plant. Geometrics 2015; 57:18-25. doi:10.1016/j.geothermics.2015.05.005
480
[29] El-Emam R., Dincer İ. Exergy and exergoeconomic analyses and optimization of geothermal organic
481
Rankine cycle. Appl Therm Eng 2013; 59:435-444. doi: 10.1016/j.applthermaleng.2013.06.005
482
[30] Shokati N, Ranjbar F, Yari M. A comparative analysis of rankine and absorption power cycles from
483
exergoeconomic viewpoint. Energy Convers and Manage 2014;88:657-668.doi:10.1016/j.enconman.2014.09.015
484
[31] V. Zare. A comparative exergoeconomic analysis of different ORC configurations for binary geothermal
485
power plants. Energy Convers and Manage 2015;105:127-138. doi:10.1016/j.enconman.2015.07.073
for
waste
heat
recovery
from
reheat
furnace
evaporative
cooling
system.
486
22
Page 22 of 31
487 488
Comment [U1]: AUTHOR: Two different versions of captions for Figure 1 were provided in the manuscript and the ones in the main text section have been used. Please check and confirm that it is correct.
Fig.1. Schematic representation of ORC system [25].
489
Pump; 0.05
, 0.000 Evaporator; 0.2
Turbine; 0.6
Condenser; 0.15
490 491
Fig.2. Distribution of the cost rates for components.
492
23
Page 23 of 31
600,000 500,000
PEC(US$)
400,000 300,000 200,000 100,000 0 Evaporator Condenser
Turbine
Pump
System
Components 493 494
Fig.3. Distribution of the purchased equipment costs of the components.
495
5%
Zt($/h)
20%
15% 60%
496 497
Evaporator
Condenser
Turbine
Pump
Fig.4. Distribution of the total investment costs of the components.
498
24
Page 24 of 31
3.5 3
ĊD($/h)
2.5 2 1.5 1 0.5 0 Evaporator
Condenser
Turbine
Pump
Components 499 500
Fig.5. Exergy destruction cost rates of the system components for condition-1.
501 3.8 3.7
ĊD($/h)
3.6 3.5 3.4 3.3 3.2 3.1 3 Sat. Liq.
X = 0,3
X = 0,7
Sat. Vap.
Conditions 502 503
Fig.6. Exergy destruction cost rates for the evaporator for four different conditions
504
25
Page 25 of 31
Exergoeconomic factor (f) (%)
90 80 70 60 50 40 30 20 10 0 Evaporator
Turbine
Pump
Components
505 506
Condenser
Fig.7. The exergoeconomic factors of the system subcomponents for condition-1
507 Evaporator
System
Exergoeconomic Factor (%)
70 60 50 40 30 20 10 0 Sat. Liq.
X = 0,3
X = 0,7
Sat. Vap.
Conditions 508 509
Fig.8. The exergoeconomic factors of the evaporator and system for four different conditions.
510
26
Page 26 of 31
511
Table 1: Specifications of the system components Components
Model/Type
Capacity
Dimensions
Evaporator
Shell and tube
3161kW (Max)
Ø1000mmX6000mm
Condenser
Shell and tube
2885 kW (Max)
Ø900mmX6000mm
272 kW (Max)
----
Turbine
Pump
CARRIER PC-51 Grundfos/ KB-G-A-E-
72.82m3/h / 50kW
HOBE
motor
----
512
Each tube length and tube diameter are 10 mm and 6,000 mm which are made of copper.
513
Heat transfer area at condenser is;
514
20Пx 6000x 658= 7,896Пx10^7 mm2
515
Heat transfer area at evaporator is;
516
20Пx6000x344=4,128Пx10^7 mm2
Operating
Tube
Heat Transfer
Pressure
Numbers
Area
23.78 bar (max) 23.78 bar (max) 23.78 bar (max) 9.307 bar (max)
344
658
4.128Пx10^7 mm2 7.896Пx10^7 mm2
----
----
----
----
Page 27 of 31
517
Table 2: The properties of R245fa ASHRAE Number
Molecular Formula
Atmospheric Lifetime (years)
Net GWP 100-yr
Molecular mass
Critical Temp.°C
R-245fa
C3H3F5
7.6
1030
134
154.05
Critical Pressure (absolute) MPa 3.640
518 519
520 521
Table 3: Exergy balance equations for the subsystem of ORC plant Components
Exergy Balance Equations
Evaporator
Ėx1 + Ėx6 = Ėx2 + Ėx3 + ĖxD
Turbine
Ėx3 = Ėx4 + ẆTurb + ĖxD
Condenser
Ėx4 + Ėx7 = Ėx5 + Ėx8 + ĖxD
Pump
Ėx5 + ẆP = Ėx6 + ĖxD
Table 4: The exergy destruction and exergy efficiency values of the main components for four different conditions in ORC power plant Condition-1
Condition-2
Components ĖxD (kW) η2,cyc (%) ĖxD (kW)
Condition-3
Condition-4
η2,cyc (%)
ĖxD (kW)
η2,cyc (%)
ĖxD (kW)
η2,cyc (%)
Evaporator
178.18
72.55
254.86
64.88
263.21
64.14
266.1
63.9
Turbine
113.95
69.7
113.95
69.7
113.95
69.7
113.95
69.7
Condenser
73.98
28.63
73.98
28.63
73.98
28.63
73.98
28.63
Pump
2.04
85.2
2.04
85.2
2.04
85.2
2.04
85.2
Rejected at condenser
30.98
-
30.98
-
30.98
-
30.98
-
Cycle
399.13
38.79
475.80
34.69
484.15
34.29
487.05
34.16
522
Page 28 of 31
523
Table 5: The purchased equipment cost, the cost rate, the levelized capital investment,
524
operating and maintenance costs and total investment costs of the components Component
PEC ($)
CRi
ZiCI ($/h)
ZiOM ($/h)
ZiT ($/h)
Evaporator
100,000
0.2
1.486
1.338
2.824
Condenser
75,000
0.15
1.115
1.003
2.118
Turbine
300,000
0.6
4.460
4.014
8.474
Pump
25,000
0.05
0.371
0.334
0.706
Total
500,000
1
7.434
6.690
14.124
525 526
Table 6: Exergoeconomic balance equations for the subsystem of the ORC plant Components
Exergoeconomic Balance Equations
Evaporator
Ċ6+Ċ1+ Ztevp = Ċ3+ Ċ2 c1= 1.3$/Gj c1 = c2 (Assumption) [27]
Turbine
Ċ3+Ztturb =Ċ4+Ċwt c3= c4
Condenser
Ċ4+Ċ7+ Ztcond = Ċ5+ Ċ8 c4= c5 C7=0 [31]
Pump
Ċ5+Ċwp+ Ztpump =Ċ6
527 528 529
Table 7: The exergy rate, unit exergy cost and exergy cost of the ORC power plant for condition 1-2. (For state numbers refers to Fig.1) Conditon-1
Conditon-2
Components
Ėx (kW)
Ėx (GJ/h) c ($/GJ) Ċ ($/h) Ėx (kW)
Ėx (GJ/h)
c ($/GJ) Ċ ($/h)
1
Evp inlet (w)
1032.756
3.718
1.3
4.833
803.321
2.892
1.3
3.76
2
Evp outlet (w)
383.627
1.381
1.3
1.795
77.517
0.279
1.3
0.363
29
Page 29 of 31
3
Turbine inlet (r )
563.472
2.028
4.792
9.721
563.472
2.028
4.969
10.079
4
Turbine outlet (r )
187.325
0.674
4.792
3.232
187.325
0.674
4.969
3.351
5
Pump inlet(r )
83.666
0.301
15.6
4.699
83.666
0.301
15.6
4.699
6
Pump outlet(r )
92.527
0.333
2.226
6.683
92.527
0.333
2.226
0.741
7
Cond inlet (w)
78.408
0.282
0
0
78.408
0.282
0
0
8
Cond outlet (w)
108.648
0.391
1.069
0.418
108.648
0.391
1.265
0.495
9
Pump
8.861
0.032
25.72
1.278
8.861
0.032
25.72
0.82
10 Turbine
376.147
1.354
11.051
14.964 376.147
1.354
11.228
15.204
11 Condenser
30.24
0.109
1.069
0.233
30.24
0.109
1.265
0.138
12 Evaporator
649.129
2.337
2.226
6.683
725.804
2.613
2.226
5.816
530 531 532
Table 8: The exergy rate, unit exergy cost and exergy cost of the ORC power plant for condition 3-4. (For state numbers refers to Fig.1) Conditon-3
Conditon-4
Components
Ėx (kW)
1
Evp inlet (w)
771.749
2.778
1.3
3.612
764.165
2.751
1.3
3.576
2
Evp outlet (w)
37.595
0.135
1.3
0.176
27.117
0.098
1.3
0.127
3
Turbine inlet (r )
563.472
2.028
4.988
10.119
563.472
2.028
4.995
10.132
4
Turbine outlet (r )
187.325
0.674
4.988
3.364
187.325
0.674
4.995
3.368
5
Pump inlet(r )
83.666
0.301
15.6
4.699
83.666
0.301
15.6
4.699
6
Pump outlet(r )
92.527
0.333
2.226
0.741
92.527
0.333
2.226
0.741
7
Cond inlet (w)
78.408
0.282
0
0
76.956
0.277
0
0
8
Cond outlet (w)
108.648
0.391
1.286
0.503
106.636
0.384
1.309
0.503
9
Pump
8.861
0.032
25.720
0.820
8.861
0.032
25.72
0.82
376.147
1.354
11.247
15.23
376.147
1.354
11.253
15.239
11 Condenser
30.24
0.109
1.286
0.14
66.44
0.239
1.309
0.313
12 Evaporator
734.154
2.643
2.226
5.883
737.048
2.653
2.226
5.906
10 Turbine
Ėx (GJ/h) c ($/GJ) Ċ ($/h) Ėx (kW)
Ėx (GJ/h)
c ($/GJ) Ċ ($/h)
30
Page 30 of 31
533
31
Page 31 of 31
S1359-4311(16)30260-5 http://dx.doi.org/doi: 10.1016/j.applthermaleng.2016.02.117 ATE 7846
To appear in:
Applied Thermal Engineering
Received date: Accepted date:
8-1-2016 28-2-2016
Please cite this article as: N.Filiz Tumen Ozdil, M.Rıdvan Segmen, Investigation of the effect of the water phase in the evaporator inlet on economic performance for an organic rankine cycle (ORC) based on industrial data, Applied Thermal Engineering (2016), http://dx.doi.org/doi: 10.1016/j.applthermaleng.2016.02.117. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1
Investigation of the effect of the water phase in the evaporator inlet on economic
2
performance for an Organic Rankine Cycle (ORC) based on industrial data
3
N.Filiz TUMEN OZDIL1*, M.Rıdvan SEGMEN2
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Department of Mechanical Engineering, Adana Science and Technology University, 01180 Adana, Turkey
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E-mail address: [email protected], [email protected]
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*Corresponding Author: [email protected]
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Highlights:
1
9 10
Exergoeconomic analysis of an Organic Rankine Cycle (ORC).
11
Determination of exergoeconomic performance for four different water phases in the
12 13
evaporator inlet.
Determination of the components having highest and lowest exergoeconomic factor.
14 15
ABSTRACT
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In this paper, exergoeconomic analysis of an Organic Rankine Cycle (ORC) is presented for a
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local power plant, located in the southern of Turkey. Specific Exergy Costing Method
18
(SPECOM) is applied using balance and auxiliary equations for the exergoeconomic analysis.
19
The capital investment cost, operating and maintenance costs and total investment cost of
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ORC steam plant are calculated as 7.43 $/h, 6.69 $/h and 14.12 $/h, respectively. The unit
21
exergy cost and exergy cost of the electricity produced by the turbine are found as 11.05 $/GJ
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and 14.96 $/h, respectively. In order to show the effect of the water phase in the evaporator
23
inlet on economic performance of the system, exergoeconomic factor of the system is
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calculated for four different water phases. When the evaporator inlet phase is saturated liquid
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form, better exergoeconomic performance is observed for the system. The highest
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exergoeconomic factor is observed in the pump because of the lowest exergy destruction rate
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and low total investment cost while the lowest exergoeconomic factor is observed in the
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evaporator due to the highest exergy destruction rate in evaporator. Moreover, payback period
29
assessment is calculated as 3.27 years for the ORC power plant.
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Key Words: Exergoeconomic analysis, Exergy, Heat recovery, Organic Rankine Cycle,
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SPECO Nomenclature c
unit exergy cost ($/GJ)
Subscripts
Ċ
exergy cost ($/h)
Zt
total investment cost
ĊD
exergy Destruction cost rate
cond
Condenser
ex
specific exergy (kJ/kg)
Ċturb
exergy cost due to work at turbine
ĖxD
exergy Destruction (Kw)
Ċpump
exergy cost due to work at pump
f
exergoeconomic factor
cons
Consumed
h
specific enthalpy (kJ/kg)
cyc
cycle
ṁ
mass flow rate (kg/s)
dest
Destruction
P
pressure (bar)
evp
Evaporator
pp
pinch point
rate of heat transfer (kW) s
specific entropy (kJ/kg K)
rej
rejection
T
temperature (K)
sat
Saturated
W
rate of work (kW)
sup
Superheated
2
Page 2 of 31
Ż
hourly levelized cost of investment $/h
comp
compressed
0
reference state
turb
Turbine
r
refrigerant
Greek symbols
w
water
Σ
total
Abbreviation
η1,cyc
first law efficiency
CI
capital investment
η2,cyc
second law efficiency
CR
cost rate
φ
CRF
capital recovery factor
OM
operating and maintenance
ORC
organic Rankine Cycle
PEC
purchased equipment cost
operating and maintenance cost factor
SPECOM specific exergy costing method 32 33
1. Introduction
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Energy can not be generated or consumed by itself so the energy conservation process
35
become the vital concept in the world. The waste heat recovery is the most suitable source for
36
the energy conservation due to lack of the fossil fuels and global warming. The waste heat
37
recovery process helps the energy conservation and decrement of the thermal pollution.
38
Although the steam turbine is the most common technology in the energy conversion process,
39
due to necessity of high operational temperature and pressure, it is not suitable for low
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temperature and pressure condition. Organic Rankine Cycle is generally preferred for the
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processes having low temperature like T< 150oC. This process is called as Organic Rankine
42
Cycle owing to usage of the organic fluid as working fluid instead of water and high pressure
43
steam.
44
Exergy is the measurement of the maximum useful work that can be obtained from the
45
system. Therefore, it has become more important research topic than energy in order to
46
determine the useful work. Because of the irreversibility, exergy can be consumed or
47
destroyed in the processes. The consumption of the exergy rate in a process is directly related
48
with the entropy generation. The exergoeconomic analysis is a method that comes out with
49
the combination of both the exergy and economic analysis. The exergoeconomic method has a
50
huge potential to optimize the systems using effectiveness of the energy and exergy. The
51
overall aims of the exergoeconomic analysis are listed as below;
52
i.
detailed analysis of the cost formation and the cost flow in a system
53
ii.
demonstration of the specific variables for each components in a convenient way
54
iii.
indication of the relationship between the cost based performance and the
55 56
thermodynamic performance iv.
optimization of the whole system performance in terms of economic structure
57
There are a number of exergoeconomic methods in thermodynamics such as
58
Thermoeconomic Functional Analysis (TFA) [1,2], Exergy Economic Approach (EEA) [3],
59
Last-In-First-Out Approach (LIFOA) [4], Exergetic Cost Theory (ECT) [5], Structural
60
Analysis Approach (SAA) [6], Engineering Functional Analysis (EFA) [7], First
61
Exergoeconomic Approach (FEA) [8], and Specific Exergy Costing Method (SPECOM) [9].
62
In this paper, SPECO method is applied in order to understand the cost formation process of
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the ORC system. The traditional SPECO method consists of the below three steps;
64
i.
Step 1: identification of the exergy streams 4
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ii.
Step 2: definition of the fuel and product
66
iii.
Step 3: forming the cost equations
67
There are a lot of studies about ORC for the power generation from the waste heat
68
recovery. In research of Kaşka [10], the energy and exergy analyses of a steel plant were
69
performed using actual plant data. He concluded that the exergy destruction rate was listed
70
from higher to lower as evaporator, turbine, condenser and pump. Moreover, it was observed
71
that the evaporator pressure had an important effect on the energy and exergy efficiency.
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Ozdil et al. [11] presented a thermodynamic analysis of an ORC in a local power plant.
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Furthermore, the relationship between the pinch point and the exergy efficiency was
74
observed. The energy and exergy efficiencies of the ORC were calculated as 9.96% and
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47.22%, respectively for saturated liquid form. Moreover, exergy destruction and exergy
76
efficiencies of components and overall system were calculated for different water phases. The
77
analyses showed that evaporator had an important effect on the system efficiency depending
78
on the exergy rate. Esen et al. [12] demonstrated the energetic and exergetic performance of
79
ground coupled heat pump system as a function of depth trenches for heating season. They
80
performed horizontal ground heat exchangers (HGHEs) buried 1 m and 2 m depth trenches.
81
The energy efficiencies of ground coupled heat pump systems for horizontal ground heat
82
exchangers (HGHE1 and HGHE2) were obtained to be 2.5 and 2.8. The exergetic efficiencies
83
of the heat pump system were found as 53.1% and 56.3% for HGHE1 and HGHE2.
84
Furthermore, the irreversibility of HGHE2 was less than that of about 2.0% in comparison
85
with HGHE1. The results showed that the energetic and exergetic efficiencies of the system
86
increased with increasing the heat source temperature for heating season. The increment of
87
the reference environment temperature caused the decrement of the exergy efficiency in
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HGHE1 and HGHE2.
5
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There are limited studies about exergoeconomy. Quoilin et al. [13] focused on a
90
thermodynamic and thermoeconomic optimization of a small scale ORC which is used in
91
waste heat recovery application. A resized model of the ORC was proposed in order to predict
92
the cycle performance with different working fluids and different components sizes. The
93
optimum economical cost was obtained as 2136 €/kW for n-butane while the optimum
94
thermodynamic performance was obtained as 5.22% for the same fluid. Khaljani et al. [14]
95
presented a thermodynamic, exergoeconomic and environmental assessment of a cogeneration
96
of the heat and power cycle. The results showed that the most exergy destruction rate took
97
place in the combustion chamber, and it was followed by heat recovery steam generator and
98
gas turbine. The exergoeconomic factor was 10.59% for the whole cycle. And, it indicated
99
that the exergy destruction cost rate was higher than capital investment cost rate. Moreover, in
100
order to assess the effects of the design parameters on the objective functions, a parametric
101
study was conducted. The results revealed that the increment in pressure ratio and isentropic
102
efficiency of air compressor and gas turbine improved the thermodynamic performance of the
103
system. However, the more increment of the parameters yielded worse in the total cost rates.
104
Wang et al. [15] studied a theoretical model on the payback period of an ORC system for
105
recovering low-grade waste heat of flue gas. Based on the minimum payback period principle,
106
a comprehensive internal parameter optimization was carried out in their study. Moreover, the
107
effects of external parameters on the payback period were analyzed and a new criterion of
108
screening working fluids was proposed. Their results showed that the payback period of the
109
ORC system decreased first than increased as the evaporation temperature, condensation
110
temperature, and the pinch point temperature differences increased in the evaporator and
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condenser.
112
Hajabdollahi et al. [16] presented four different analyses including energy, efficiency,
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economic and environment for equipment selection and waste heat recovery on a diesel 6
Page 6 of 31
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engine using Organic Rankine Cycle. The design parameters were selected as nominal
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capacity of diesel engine, diesel operating partial load, evaporator pressure, condenser
116
pressure and refrigerant mass flow rate. Four different refrigerants such as R123, R134a,
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R245fa and R22 were selected and employed as working fluids. The results showed that the
118
best working fluid was R123 in both of the economical and thermodynamic point of view,
119
while the worst working fluid was R22. Furthermore, R245fa showed similar results with
120
R123 in terms of efficiency and total annual cost. They concluded that R245fa seemed as a
121
good backup for R123. They concluded that non-dimensional cost didn’t effect optimization
122
of the thermal efficiency. Li [17] evaluated thermoeconomic performance of Kalina and CO2
123
transcritical power cycle for low temperature geothermal sources. He crosschecked for the
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mentioned two cycles using six parameters which were net power output, thermal efficiency,
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exergy efficiency, total heat exchanger area, cost per net power (CPP) and the percentages in
126
the total cost (PHC). They represented that Kalina cycle had a higher thermal efficiency and
127
net power output. On the other hand, Kalina cycle had less exergy efficiency than that of the
128
CTPC. Desai and Bandyopadhyay [18] compared the organic Rankine and steam Rankine
129
cycles in terms of termoeconomic point of view. They suggested selection methodology based
130
on thermoeconomic analysis for working fluids of power generating cycles. They concluded
131
that the condition of equality of levelized cost of energy (LCOE) was one of the most
132
important items for the working fluid selection. Qureshi [19] conducted thermoeconomic
133
optimization of power systems using finite thermal capacitances for design situation. They
134
used internal irreversibility multiplier which could disregard some details. They observed
135
changing in the cycle thermal efficiency for endoreversible case. Park et al. [20] performed
136
thermo-economic analysis of 300 MW class IGCC power plant using ASPEN Plus®. They
137
calculated the levelized cost of electricity (LCOE) using the total revenue requirement (TRR)
7
Page 7 of 31
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method. They observed that reduction of the LCOE led to improved system efficiency
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because of lower carrying charge, O&M cost and fuel cost.
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Esen and Yuksel [21] investigated a greenhouse that heated using solar, biogas and ground
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energy in Elazig, city of Turkey. They constructed a greenhouse with dimensions 6 m x 4 m x
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2.10 m and required heating load was determined. In order to test the different energy sources,
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three different heat pump heating system with horizontal slinky ground heat exchanger were
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designed and built. Moreover, the effects of operating parameters and climatic conditions on
145
the system performance parameters were examined. They concluded that solar energy can be
146
stored underground and used to increase soil temperature. In addition, it was observed to be
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an advantage heating the greenhouse beside reactor for energy savings in heating process
148
using biogas. According to study of Esen et al. [22], the performance experiments and
149
economic analysis of a horizontal ground source heat pump system were performed. The
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horizontal ground space heat pump system, which attached to a test room, was designed and
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built for space heating. The performance was evaluated under real operating conditions.
152
Moreover, a detailed cost analysis was applied and payback period was determined. The
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annualized life cycle cost method was used in the economical analysis, in order to compare
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the ground source heat pump system with conventional heating methods. The results showed
155
that the ground source heat pump system has some economic advantages compared with other
156
conventional heating methods but it was not an economic choice over the natural gas. Esen et
157
al. [23] examined the differences between a ground coupled heat pump system and an air
158
coupled heat pump system, in their study. The investigated systems were attached to a test
159
room in Firat University and they were designed and built for space cooling. The
160
performances of the ground coupled heat pump system and the air coupled heat pump system
161
were analyzed, experimentally for cooling season from June to September. The results
162
showed that the COP of the ground coupled heat pump system were found as 3.85 and 4.26 8
Page 8 of 31
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for horizontal ground heat exchanger in the different trenches at 1 m and 2 m depths. The
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COP of the air coupled heat pump system was obtained as 3.17. They concluded that the
165
system parameters affected the performance of the system and the ground coupled heat pump
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systems were more preferable in comparison with the air coupled heat pump systems in terms
167
of space cooling in economic point of view.
168
Even though, there are a few studies addressing the exergoeconomic analysis of the
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power generation plants, detailed discussions and analysis of the relationship between the
170
exergy and economic sustainability of the ORC system for the real industry are necessary. In
171
this study, an extensive exergoeconomic analysis is carried out for an ORC which generates
172
electricity using waste heat recovery in a local steel plant. Based on the data obtained from the
173
thermodynamic analysis, the exergoeconomic analysis and the exergetic performance
174
assessment are performed for each component of the ORC system and exergy-cost relations
175
are resolved in parts.
176
The novelties of this study can be listed as below;
177
i.
This study presented an extensive exergoeconomic analysis for a running
178
Organic Rankine Cycle (ORC) plant, located in southern of Turkey. Different
179
from studies in literature; economic performance comparison was examined for
180
four different water phases in the evaporator inlet (sat. liq., X=0.3, X=0.7 and sat.
181
vapor) in order to show the effect of the different water phases in the evaporator
182
inlet on economic performance.
183
ii.
Moreover, the purchased equipment cost (PEC), the cost rate (CR), the levelized
184
capital investment (ZiCI), operating and maintenance costs (ZiOM) and total
185
investment costs (ZiT) of the system components are calculated. In order to show
9
Page 9 of 31
186
the exergoeconomic performance of the system components, exergy destruction
187
cost rates and the exergoeconomic factor rates of the components are graphed.
188
iii.
Furthermore, the payback assessment analysis is applied on the system to obtain
189
the payback time of the ORC steam plant for saturated liquid in the evaporator
190
inlet phase.
191
2. System description
192
In this study, the exergoeconomic analysis is performed for the running ORC system
193
which is located in Adana, Turkey. The ORC produces electricity using waste heat in low
194
temperature in order to reduce the operating costs of the company. The investigated system
195
has 260.4 kW capacity and specifications of the system components are demonstrated in
196
Table 1.
197
The system involves an evaporator, a condenser, a turbine and a pump as subcomponent.
198
The generator, heating and cooling water collectors are accepted as the auxiliary components.
199
The working fluid used in the ORC cycle is R245fa (Pentafluoropropane) which has good
200
thermodynamic properties such as low specific heat and viscosity, low toxicity, low ozone
201
depletion potential, low flammability. Most of the ORC systems use R245fa as the working
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fluid which has moderate global warming potential of 1030, power density, and lower critical
203
pressure at higher temperature [24]. Owing to the above mentioned properties and the
204
favorable economic conditions, the R245fa is a convenient option for working fluid. The
205
properties of the R245fa are shown in Table 2.
206
The schematic diagram of the ORC system is illustrated in Fig. 1. In the system, working
207
fluid is pumped, firstly; then low pressure fluid is compressed to high pressure fluid by a
208
pump as can be seen in Fig. 1. (state 5 to 6). Later, the high pressure fluid enters and passes
209
through the evaporator. In the evaporator, the high pressure fluid (6) has become heated and
210
pressurized vapor (3) using the heat capacity of inlet water (state 1 to 2). After that the heated
10
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and pressurized vapor enters to the turbine. While it leaves from turbine as low pressure
212
vapor, it leads to electricity generation (state 3 to 4). Lastly, the low pressure vapor goes
213
through the condenser, and the working fluid leaves from the condenser as saturated liquid
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(state 4 to 5) and the cycle continues so on.
215
Some amounts of data are measured from the system and the remaining data are obtained
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from the computer aided control panel directly. Dead state conditions of the working fluid
217
(R245fa) and the water are accepted as 1 bar and 25oC. Before the performing the analysis,
218
the first step is to measure the mass flow rate of the condenser cooling water (7). Mass flow
219
rate of the condenser cooling water is measured by GE-PT878 which is ultrasonic flowmeter
220
equipment ranges from ½”-7,6mm with ± 1% accuracy. Mass flow rate of the R245fa is
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calculated from the mass and energy balance equations from the condenser cooling water and
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the mass flow rate of the evaporator inlet water is estimated from the first law of the
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thermodynamic. The water collectors on the system are placed in the evaporator and
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condenser inlet and outlet. Pressure and temperature measurement devices are put on
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collectors in order to measure the thermophysical properties of the water and the working
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fluid.
227 228
3. Analysis
229
The aim of this study is to apply an exergoeconomic analysis in order understand the
230
connection between the cost performance and the thermodynamic performance of the ORC
231
system. The exergoeconomic balance equations are implemented on the ORC system using
232
the data obtained from the first and second law of thermodynamics.
233
The first law of the thermodynamics is explained as the conservation of the energy. The total
234
energy, which is being constant in the processes, can be converted or transferred. The second
235
law of thermodynamics claims that energy has quality as well as quantity. The second law of 11
Page 11 of 31
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thermodynamics is applied to determine the quality as well as the degree of energy reduction
237
during a process. The second law refers to the change of the quality of the energy during the
238
phase change in the processes. The maximum useful work in a process is called as exergy.
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The higher exergy destruction rate means lower useful energy conversion in the processes.
240
The following assumptions were made in this study;
241
Pressure drops, potential and kinetic energy changes on the system are neglected.
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The system operates in a continuous steady state flow process.
243
The system is adiabatic which means there is no heat loss.
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The exergy balance and auxiliary equations for the each component are shown in Table 3.
245
The thermoeconomic analysis combines exergy and economic analyses to provide
246
information that is not accessible with general energy and exergy analysis. In general, for the
247
economic analysis, a cost balance can be formulated for the steady state system for each
248
control volume i:
249
∑ Ċin,i + ŻiT = ∑ Ċout,i + ĊiW + ĊiQ
(1)
250
Ċi = ciExi
(2)
251
ĊiW = ciWi
(3)
252
ĊiQ = ciExiQ
(4)
253
ŻiT = ŻiCI + ŻiOM
(5)
254
where Ċi, ĊiW, ĊiQ are the exergy costs of the flow, power and heat, respectively; ci, ciw, ciq
255
are the unit exergy costs of the flow, power and heat, respectively; Exi, Wi and ExiQ are the
256
exergy of the flow, power and heat entering and leaving control volume; ŻiCI, ŻiOM and ŻiT are
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Page 12 of 31
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the hourly levelized costs of the capital investment, operating and maintenance and the total
258
cost of equipment inside the control volume.
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The hourly levelized cost approach is used to calculate ŻiCI with using equations below:
260
The capital recovery factor (CRF):
261
CRF = (i(i+1)n)/((i+1)n-1)
262
The hourly levelized capital investment cost of the ith component at the ŻiCI :
263
ŻiCI = (CRF/τ)PECi
264
The cost rate of the subsystems CRi:
265
CRi = PECi / ∑ PECORC
266
Where i, n, τ and PEC are the interest rate, the life time of the plant, total annual number of
267
hours of the system operated at a full road and the purchased equipment cost, respectively.
268
For this system i, n and τ are taken as 0.1, 20 years and 7,900.
269
ŻiOM = ŻiCI φ
270
Where the maintenance and operating costs are considered with the factor φ = 0.9 for the
271
steam plant and its auxiliary components.
272
The total investment price of the examined ORC power plant is 500,000 $ and the
273
subsystem’s costs are calculated with the cost rates given by the manager of the plant.
274
The unit exergy cost of the electricity is;
275
cW = PrW/(ER 3,600 10-6) (s/h) (GJ/kJ)
(6)
(7)
(8)
(9)
(10)
13
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276
Where PrW and ER are called as the electricity sell price in the Turkish Lira (TL) and the
277
exchange rate (TL/$), respectively [26]. The unit exergy cost of the heating source and the
278
working fluid are assumed to be 1.3$/GJ [27] and 15.6$/GJ [28] respectively.
279
The aim of the exergoeconomic analysis is to understand the cost formation process and
280
calculations of the cost rate for each product on the steam plant. In this study, analyses are
281
performed for four different water phases of evaporator inlet in order to investigate the effect
282
of water phase on exergoeconomic performance. These conditions can be listed as;
283
i.
Saturated liquid,
284
ii.
Water mixture (quality 0.3),
285
iii.
Water mixture (quality 0.7),
286
iv.
Saturated vapor phase of the evaporator inlet.
287 288
The given exergoeconomic parameters are taken into consideration to understand the frame of the cost and exergy flows:
289
i.
The average unit cost of the fuel, cf,i,
290
ii.
The average unit cost of the product,cp,i,
291
iii.
The cost rate of the exergy destruction, cD,i,
292
iv.
The exergoeconomic factor, fi,
293
fi = ZiT / (ZiT + (cf,i (ExD,i + ExL,i)))
(11)
294
The exergoeconomic factor provides comprehensive information regarding the
295
combination of the non-exergy costs (capital investments, operating and maintenance costs),
296
the exergy destruction and the exergy loss. The exergetic fuel is defined as the consumed 14
Page 14 of 31
297
resource for generating product in the ORC system. The cost rate of the exergy destruction
298
shows how much $/h can be destructed during the operation. In order to increase the system
299
effiency, the pinch point temperature is found as 105.2oC and ΔTpp is found as 6.2oC. The
300
result is similar with Kaşka [10] and Ozdil [11].
301
4. Results and Discussions
302
The ORC produces electricity using waste heat with low temperature. In this study, the
303
extensive exergoeconomic analysis is performed using the first and second laws of the
304
thermodynamics and economic parameters in order to observe the relationship between
305
thermodynamics and economic performance of components for the running ORC power plant.
306
Furthermore, the effect of the different water phases in the evaporator inlet on the economic
307
performance of the system is examined in this study. Four different water phases in the
308
evaporator inlet are examined. When the water phase in the evaporator inlet is saturated liquid
309
in condition-1, the exergy efficiency of the system is calculated as 38.79%. In condition-2,
310
water phase in the evaporator inlet is assumed as saturated water mixture which is quality is
311
0.3. The exergy efficiency of the system is calculated as 34.69% for condition-2. In condition-
312
3, water phase in the evaporator inlet is assumed as saturated water mixture which is quality is
313
0.7. The exergy efficiency of the system is calculated as 34.29% for condition-3. Moreover, in
314
condition-4, water phase in the evaporator inlet is assumed as saturated vapor. The exergy
315
efficiency of the system is calculated as 34.16% for condition-4. The exergy destruction rates
316
and the exergy efficiencies of the all system components are shown in Table 4 for all
317
conditions. Based on the Table 4, the exergy efficiencies of evaporator, turbine, condenser
318
and pump are calculated as 72.55%, 69.7%, 28.69% and 85.2%, respectively for condition-1.
319
Exergy loss in the cycle is sum of the total exergy destruction and exergy transferred to the
320
condenser cooling water. In other words, exergy transfer rate from the R245fa to the
321
condenser cooling water is assumed to be part of the exergy destruction. As a result, exergy 15
Page 15 of 31
322
loss is the exergy rate extracted from the evaporator. Unlike exergy loss, exergy destruction
323
means internal losses by the components because of the irreversibility. The major exergy
324
destruction occurs in the evaporator with about 178.18 kW and followed by the turbine,
325
condenser and pump for condition-1. These results are compatible with Kaşka [10] and
326
Khaljani [14]. The exergy transfer rate from the R245fa to the condenser cooling water is
327
assumed to be part of the exergy destruction in this study.
328
The purchased equipment cost, the cost rate, the hourly levelized capital investment cost,
329
operating and maintenance cost and the total investment costs of the ORC power plant with its
330
components are shown in Table 5. The capital investment cost, operating and maintenance
331
costs and total investment cost for ORC power plant are found as 7.434 $/h, 6.69 $/h and
332
14.124 $/h, respectively. The distribution of the cost rates, the purchased equipment costs and
333
the total investment costs of the components are also presented in Figs. 2-3-4, respectively. As
334
can be seen in Figs. 2-3-4, the highest cost rate, the highest purchased equipment cost and the
335
highest total investment cost values are found as 0.6, 300,000 $ and 8.47 $/h for the turbine
336
due to the high purchased equipment-total system cost ratio. The cost balance equations are
337
demonstrated in Table 6. Moreover, unit exergy cost and exergy cost of the components for
338
the ORC power plant are shown in Table 7 and 8 for conditions 1-2-3-4 with respect to the
339
state numbers as can be seen in Fig. 1. Based on the cost balance equations (Table 6), the unit
340
exergy cost and exergy cost of the electricity produced by the turbine are calculated as 11.05
341
$/GJ and 14.96 $/h for condition-1, 11.22 $/GJ and 15.2 $/h for condition-2, 11.25 $/GJ and
342
15.24 $/h for condition-3 and 11.3 $/GJ and 15.28 $/h for condition-4, respectively.
343
The exergy destruction cost rates of the system components are demonstrated in Fig. 5 for
344
condition-1. The evaporator and the turbine have the highest exergy destruction cost rate
345
because of their higher exergy destruction rate and higher cost of fuel values. It is consistent
346
with study of Khaljani [14]. Fig. 6 shows the effect of the exergy destruction cost rate for four
16
Page 16 of 31
347
different conditions. The lowest exergy destruction cost rate is calculated for condition-1
348
because condition-1 has the lower exergy destruction rate than that of other conditions.
349
Furthermore, the increment of the exergy destruction causes high the exergy destruction cost
350
rate. The exergoeconomic factors of the system subcomponents for condition-1 are illustrated
351
in Fig. 7. The results showed that the highest exergoeconomic factor is found in pump like
352
study of El-Emam [29] because of it’s low exergy destruction rate and low total investment
353
cost value. Moreover, the lowest exergoeconomic factor is calculated for the evaporator
354
because of the high exergy destruction rate. When compared with the study of Shokati N. et
355
al [30], the similar results are observed. The exergoeconomic factors of the system for the
356
condition 1-2-3-4 are calculated as 65.8%, 64.23%, 64.16% and 64.1%, respectively as shown
357
in Fig. 8. When the water phase changes from condition-1 to condition-4, exergy destruction
358
cost rates of the systems and evaporators increases gradually.
359
exergoeconomic factor of the evaporator and the entire system slightly decreases due to the
360
increment of the exergy destruction cost rate. Evaporator is the most important component in
361
terms of exergoeconomic point of view. In order to decrease the exergy destruction in the
362
evaporator, heat input can be decreased. Namely, condition-1 is more efficient than condition-
363
1-2-3 because heat input is lower from that of the other conditions. When the evaporator inlet
364
phase is saturated liquid form, better exergoeconomic performance is observed for the system.
365
5. Payback Period Assessment
Furthermore, the
366
Payback period is determined as the required time to recover an investment. The payback
367
period of an investment or project is an important parameter in order to evaluate the recycling
368
time of the system. Namely, longer payback periods are not desirable for investment
369
positions.
370
PEC ($) = 500,000 $
17
Page 17 of 31
371
Capacity of the turbine: 260.4 kWh
372
Operation time: 7900 h/y
373
Utility rate: 0.1 $
374
Operational and maintenance cost: 52,851 $/y
375
Full capacity electricity generation: (259kWh) x (7900h/y) = 2,057,160 kWh/y
(A.1)
376
Full capacity gross return: (2,057,160kWh/y) x (0.1$) =205,716$ kWh/y
(A.2)
377
Full capacity net return: (205,716$) – (52,851$) = 152,865 $
(A.3)
378
Full capacity payback years: PEC / Full capacity kW/y
379
500,000$ / 152,865$ = 3.27 y
(A.4)
380
According to calculations; initial investment can pay for itself 3.27 years after. These
381
calculations and recommended results can be used for continuing investments and it gives an
382
idea for setting up ORC power plant.
383
6. Conclusions
384
This study presents a detailed exergoeconomic analysis of a running ORC cycle in steel
385
industry. Exergoeconomic balance equations are solved using the results obtained from the
386
first and second laws of thermodynamics analyses. The major exergy destruction occurs in the
387
evaporator with about 178.18 kW and followed by the turbine, condenser and pump for
388
condition-1. The major reasons of the inefficiency in the evaporator are high heat input,
389
namely water phase of the evaporator inlet. The exergy efficiencies of the ORC power plant
390
for the condition 1-2-3-4 are calculated as 38.79 %, 34.69%, 34.29% and 34.16%
18
Page 18 of 31
391
respectively. The exergy destruction rates of the condition 1-2-3-4 are calculated as 399.13
392
kW, 444.82 kW, 484.15 and 487.05, respectively for the overall system.
393
The exergy cost and unit exergy cost values are calculated in order to perform the
394
exergoeconomic analysis. The turbine and evaporator have the highest cost rate value; so that,
395
these components are the most important parts of the system. The capital investment cost,
396
operating and maintenance costs and total cost of the ORC power plant are found as 7.43 $/h,
397
6.69 $/h and 14.12 $/h, respectively. For the condition-1, 260.4 kW power can be generated in
398
the system that temperature and flow rate of the waste heat source are 125oC and 17.74 kg/s,
399
respectively. This means 4.07x10-3 kW electricity generation per kilogram of the heat source.
400
Exergoeconomic cost analysis shows that the exergy cost of the heat source and exergy cost
401
of the electricity produced by the turbine are 4.83 $/h and 14.96 $/h, respectively for
402
condition-1. On the other hand, the exergy cost of the heat source and exergy cost of the
403
electricity produced by the turbine are calculated as 3.76 $/h and 15.20 $/h for condition-2,
404
3.61 $/h and 15.24 $/h for condition-3 and lastly 3.57 $/h and 15.28 $/h for condition-4,
405
respectively. For the all conditions, the evaporator component has the lowest exergoeconomic
406
factor rate due to the high exergy destruction rate while the pump has the biggest
407
exergoeconomic factor rate because of the low total investment cost and the low exergy
408
destruction rate. The exergoeconomic factors of the system for the condition-1-2-3-4 are
409
calculated as 65.8%, 64.2%, 64.16% and 64.11% respectively. When the condition-1 is
410
compared with the other conditions, the highest exergoeconomic factor is observed
411
forcondition-1. Namely, low heat input causes better efficiency and economic performance.
412
Based on the observations, the evaporator inlet phase has important effect on economical
413
performance of the system. When the evaporator inlet phase is saturated liquid form, better
414
exergoeconomic performance is observed for the system. In addition, the payback calculations
415
show that the payback period of the ORC power plant is calculated as 3.27 years. 19
Page 19 of 31
416
References
417
[1] Frangopoulos, C.A. Thermoeconomic functional analysis: a method for optimal design or improvement of
418
complex thermal systems. PhD Thesis. Georgia Institute of Technology, Georgia, USA, 1983
419
[2] Frangopoulos C.A. Thermoeconomic functional analysis and optimization. Energy 1987; 12(7): 563- 571.
420
doi:10.1016/0360-5442(87)90097-1
421
[3] Gaggioli, R.A, Wepfer, W.J. Exergy economics. Energy 1980; 5:823-38. doi:10.1016/0360-5442(80)90099-7
422
[4] Tsatsaronis, G., Lin, L., Pisa, J. On exergy costing in exergoeconomics. J. Energy Resour. Technol
423
1993; 115(1): 9-16. doi:10.1115/1.2905974
424
[5] Valero, A., M. A. Lozano, and M. Muñoz. "A general theory of exergy saving. I. On the exergetic
425
cost." Computer-Aided Engineering and Energy Systems. Second Law Analysis and Modelling, R. Gaggioli,
426
ed 3 (1986): 1-8.
427
[6] Valero, A., Torres, C., Serra, L., & Lozano, M. A. A General Theory of Thermoeconomics, Parts I and II,
428
ECOS 92 Ed. By A. Valero and G. Tsatsaronis, Zaragoza. ASME Bok, 1992; (100331), 147-154.
429
[7] Von Spakowsky, M.R. A Practical generalized analysis approach to the optimal thermoeconomic design and
430
improvement of real-world thermal systems. PhD Thesis, Georgia Institute of Technology, Georgia, USA, 1986.
431
[8] Tsatsaronis G, Winhold M. Exergoeconomic analyses and evaluation of energy conversation plants. Energy
432
1985; 10:69-94. doi:10.1016/0360-5442(85)90020-9
433
[9] Lazzaretto, A., and Tsatsaronis, G. SPECO: A systematic and general methodology for calculating
434
efficiencies and costs in thermal systems. Energy 2006; 31:1257-1289. doi:10.1016/j.energy.2005.03.011
435
[10] Kaşka Ö. Energy and exergy analysis of an organic Rankine for power generation from waste heat recovery
436
in steel industry. Energy Convers and Manage 2014; 77:108-117. doi:10.1016/j.enconman.2013.09.026
437
[11] Tumen Ozdil NF, Segmen MR, Tantekin A. Thermodynamic analysis of an Organic Rankine Cycle (ORC)
438
based on industrial data. Appl Therm Eng 2015; 91:43-52. doi:10.1016/j.applthermaleng.2015.07.079
20
Page 20 of 31
439
[12] Esen H, Inalli M, Esen M, Pihtili M. Energy and exergy analysis of a ground-coupled heat pump system
440
with two horizontal ground heat exchangers, Building and Environment, 2007;42(10):3606-3615.
441
doi:10.1016/j.buildenv.2006.10.014
442
[13] Quoilin S., Declaye S., Tchanche BF., Lemort V. Thermo-economic optimization of waste heat recovery
443
Organic Rankine Cycles. Appl Therm Eng 2011; 31:2885-2893. doi:10.1016/j.applthermaleng.2011.05.014
444
[14] Khaljani M, Saray R, Bahlouli K. Comprehensive analysis of energy, exergy and exergo-economic of
445
cogeneration of heat and power in a combined gas turbine and organic Rankine cycle. Energy Convers and
446
Manage 2015; 97:154-165. doi:10.1016/j.enconman.2015.02.067
447
[15] Wang X., Li X., Li Y., Wu C. Payback period estimation and parameter optimization of subcritical organic
448
Rankine cycle system for waste heat recovery, Energy 2015; 88:735-74. doi:10.1016/j.energy.2015.05.095
449
[16] Hajabdollahi Z., Hajabdollahi F., Tehrani M., Hajabdollahi H.
450
optimization of Organic Rankine Cycle for diesel waste heat recovery, Energy 2013; 63:142-151.
451
doi:10.1016/j.energy.2013.10.046
452
[17] Li S, Dai Y. Thermo-economic comparison of Kalina and CO2 transcritical power cycle for low
453
temperature
454
doi:10.1016/j.applthermaleng.2014.04.067
455
[18] Desai NB, Bandyopadhyay S. Thermo-economic analysis and selection of working fluid for solar organic
456
Rankine cycle. Appl Therm Eng 2016;95:471-481. doi:10.1016/j.applthermaleng.2015.11.018
457
[19] Qureshi BA. Thermoeconomic considerations in the allocation of heat transfer inventory for irreversible
458
power systems. Appl Therm Eng 2015;90:305-311. doi:10.1016/j.applthermaleng.2015.06.104
459
[20] Park SH, Chung SW, Lee SK, Choi HK, Lee SH. Thermo-economic evaluation of 300 MW class integrated
460
gasification combined cycle with ash free coal (AFC) process. Appl Therm Eng 2015;89:843-852.
461
doi:10.1016/j.applthermaleng.2015.06.066
462
[21] Esen M, Yuksel T. Experimental evaluation of using various renewable energy sources for heating a
463
greenhouse, Energy and Buildings, 2013;65:340-351. doi:10.1016/j.enbuild.2013.06.018
464
[22] Esen H, Inalli M, Esen M. Technoeconomic appraisal of a ground source heat pump system for a heating
465
season
466
doi:10.1016/j.enconman.2005.06.024
in
geothermal
eastern
sources
Turkey,
in
Energy
China.
Convers
Appl
and
Thermo-economic environmental
Therm
Manage
Eng
2014;70:139-152.
2006;47(9-10):1281-1297.
21
Page 21 of 31
467
[23] Esen H, Inalli M, Esen M. A techno-economic comparison of ground-coupled and air-coupled heat pump
468
system for space cooling, Building and Environment, 2007;42(5):1955-1965.doi:10.1016/j.buildenv.2006.04.007
469
[24] Cool prop web-site. www.coolprop.org/v4/Fluids/R245fa. Accessed June 2015
470
[25] A. Durmaz, R. Pugh, S¸ Yazıcı, K. Erdogan, A. Kosan. Novel application of Organic Rankine Cycle (ORC)
471
technology
472
www.tmeic.com/Repository/ Media/AIST_Toscelik_ORC_v9.pdf.
473
[26] Tumen Ozdil N.F., Tantekin A. Exergoeconomic analysis of a FBCC steam power plant. Thermal Science.
474
2016; (Accepted)
475
[27] Shokati N, Ranjbar F, Yari M. Exergoeconomic analysis and optimization of basic, dual-pressure and dual-
476
fluid ORCs and Kalina geothermal power plants: A comparative study. Renew Energy 2015; 83:527-542.
477
doi:10.1016/j.renene.2015.04.069
478
[28] Yilmaz C, Kanoğlu M, Abusoğlu A. Thermoeconomic cost evaluation of hydrogen production driven by
479
binary geothermal power plant. Geometrics 2015; 57:18-25. doi:10.1016/j.geothermics.2015.05.005
480
[29] El-Emam R., Dincer İ. Exergy and exergoeconomic analyses and optimization of geothermal organic
481
Rankine cycle. Appl Therm Eng 2013; 59:435-444. doi: 10.1016/j.applthermaleng.2013.06.005
482
[30] Shokati N, Ranjbar F, Yari M. A comparative analysis of rankine and absorption power cycles from
483
exergoeconomic viewpoint. Energy Convers and Manage 2014;88:657-668.doi:10.1016/j.enconman.2014.09.015
484
[31] V. Zare. A comparative exergoeconomic analysis of different ORC configurations for binary geothermal
485
power plants. Energy Convers and Manage 2015;105:127-138. doi:10.1016/j.enconman.2015.07.073
for
waste
heat
recovery
from
reheat
furnace
evaporative
cooling
system.
486
22
Page 22 of 31
487 488
Comment [U1]: AUTHOR: Two different versions of captions for Figure 1 were provided in the manuscript and the ones in the main text section have been used. Please check and confirm that it is correct.
Fig.1. Schematic representation of ORC system [25].
489
Pump; 0.05
, 0.000 Evaporator; 0.2
Turbine; 0.6
Condenser; 0.15
490 491
Fig.2. Distribution of the cost rates for components.
492
23
Page 23 of 31
600,000 500,000
PEC(US$)
400,000 300,000 200,000 100,000 0 Evaporator Condenser
Turbine
Pump
System
Components 493 494
Fig.3. Distribution of the purchased equipment costs of the components.
495
5%
Zt($/h)
20%
15% 60%
496 497
Evaporator
Condenser
Turbine
Pump
Fig.4. Distribution of the total investment costs of the components.
498
24
Page 24 of 31
3.5 3
ĊD($/h)
2.5 2 1.5 1 0.5 0 Evaporator
Condenser
Turbine
Pump
Components 499 500
Fig.5. Exergy destruction cost rates of the system components for condition-1.
501 3.8 3.7
ĊD($/h)
3.6 3.5 3.4 3.3 3.2 3.1 3 Sat. Liq.
X = 0,3
X = 0,7
Sat. Vap.
Conditions 502 503
Fig.6. Exergy destruction cost rates for the evaporator for four different conditions
504
25
Page 25 of 31
Exergoeconomic factor (f) (%)
90 80 70 60 50 40 30 20 10 0 Evaporator
Turbine
Pump
Components
505 506
Condenser
Fig.7. The exergoeconomic factors of the system subcomponents for condition-1
507 Evaporator
System
Exergoeconomic Factor (%)
70 60 50 40 30 20 10 0 Sat. Liq.
X = 0,3
X = 0,7
Sat. Vap.
Conditions 508 509
Fig.8. The exergoeconomic factors of the evaporator and system for four different conditions.
510
26
Page 26 of 31
511
Table 1: Specifications of the system components Components
Model/Type
Capacity
Dimensions
Evaporator
Shell and tube
3161kW (Max)
Ø1000mmX6000mm
Condenser
Shell and tube
2885 kW (Max)
Ø900mmX6000mm
272 kW (Max)
----
Turbine
Pump
CARRIER PC-51 Grundfos/ KB-G-A-E-
72.82m3/h / 50kW
HOBE
motor
----
512
Each tube length and tube diameter are 10 mm and 6,000 mm which are made of copper.
513
Heat transfer area at condenser is;
514
20Пx 6000x 658= 7,896Пx10^7 mm2
515
Heat transfer area at evaporator is;
516
20Пx6000x344=4,128Пx10^7 mm2
Operating
Tube
Heat Transfer
Pressure
Numbers
Area
23.78 bar (max) 23.78 bar (max) 23.78 bar (max) 9.307 bar (max)
344
658
4.128Пx10^7 mm2 7.896Пx10^7 mm2
----
----
----
----
Page 27 of 31
517
Table 2: The properties of R245fa ASHRAE Number
Molecular Formula
Atmospheric Lifetime (years)
Net GWP 100-yr
Molecular mass
Critical Temp.°C
R-245fa
C3H3F5
7.6
1030
134
154.05
Critical Pressure (absolute) MPa 3.640
518 519
520 521
Table 3: Exergy balance equations for the subsystem of ORC plant Components
Exergy Balance Equations
Evaporator
Ėx1 + Ėx6 = Ėx2 + Ėx3 + ĖxD
Turbine
Ėx3 = Ėx4 + ẆTurb + ĖxD
Condenser
Ėx4 + Ėx7 = Ėx5 + Ėx8 + ĖxD
Pump
Ėx5 + ẆP = Ėx6 + ĖxD
Table 4: The exergy destruction and exergy efficiency values of the main components for four different conditions in ORC power plant Condition-1
Condition-2
Components ĖxD (kW) η2,cyc (%) ĖxD (kW)
Condition-3
Condition-4
η2,cyc (%)
ĖxD (kW)
η2,cyc (%)
ĖxD (kW)
η2,cyc (%)
Evaporator
178.18
72.55
254.86
64.88
263.21
64.14
266.1
63.9
Turbine
113.95
69.7
113.95
69.7
113.95
69.7
113.95
69.7
Condenser
73.98
28.63
73.98
28.63
73.98
28.63
73.98
28.63
Pump
2.04
85.2
2.04
85.2
2.04
85.2
2.04
85.2
Rejected at condenser
30.98
-
30.98
-
30.98
-
30.98
-
Cycle
399.13
38.79
475.80
34.69
484.15
34.29
487.05
34.16
522
Page 28 of 31
523
Table 5: The purchased equipment cost, the cost rate, the levelized capital investment,
524
operating and maintenance costs and total investment costs of the components Component
PEC ($)
CRi
ZiCI ($/h)
ZiOM ($/h)
ZiT ($/h)
Evaporator
100,000
0.2
1.486
1.338
2.824
Condenser
75,000
0.15
1.115
1.003
2.118
Turbine
300,000
0.6
4.460
4.014
8.474
Pump
25,000
0.05
0.371
0.334
0.706
Total
500,000
1
7.434
6.690
14.124
525 526
Table 6: Exergoeconomic balance equations for the subsystem of the ORC plant Components
Exergoeconomic Balance Equations
Evaporator
Ċ6+Ċ1+ Ztevp = Ċ3+ Ċ2 c1= 1.3$/Gj c1 = c2 (Assumption) [27]
Turbine
Ċ3+Ztturb =Ċ4+Ċwt c3= c4
Condenser
Ċ4+Ċ7+ Ztcond = Ċ5+ Ċ8 c4= c5 C7=0 [31]
Pump
Ċ5+Ċwp+ Ztpump =Ċ6
527 528 529
Table 7: The exergy rate, unit exergy cost and exergy cost of the ORC power plant for condition 1-2. (For state numbers refers to Fig.1) Conditon-1
Conditon-2
Components
Ėx (kW)
Ėx (GJ/h) c ($/GJ) Ċ ($/h) Ėx (kW)
Ėx (GJ/h)
c ($/GJ) Ċ ($/h)
1
Evp inlet (w)
1032.756
3.718
1.3
4.833
803.321
2.892
1.3
3.76
2
Evp outlet (w)
383.627
1.381
1.3
1.795
77.517
0.279
1.3
0.363
29
Page 29 of 31
3
Turbine inlet (r )
563.472
2.028
4.792
9.721
563.472
2.028
4.969
10.079
4
Turbine outlet (r )
187.325
0.674
4.792
3.232
187.325
0.674
4.969
3.351
5
Pump inlet(r )
83.666
0.301
15.6
4.699
83.666
0.301
15.6
4.699
6
Pump outlet(r )
92.527
0.333
2.226
6.683
92.527
0.333
2.226
0.741
7
Cond inlet (w)
78.408
0.282
0
0
78.408
0.282
0
0
8
Cond outlet (w)
108.648
0.391
1.069
0.418
108.648
0.391
1.265
0.495
9
Pump
8.861
0.032
25.72
1.278
8.861
0.032
25.72
0.82
10 Turbine
376.147
1.354
11.051
14.964 376.147
1.354
11.228
15.204
11 Condenser
30.24
0.109
1.069
0.233
30.24
0.109
1.265
0.138
12 Evaporator
649.129
2.337
2.226
6.683
725.804
2.613
2.226
5.816
530 531 532
Table 8: The exergy rate, unit exergy cost and exergy cost of the ORC power plant for condition 3-4. (For state numbers refers to Fig.1) Conditon-3
Conditon-4
Components
Ėx (kW)
1
Evp inlet (w)
771.749
2.778
1.3
3.612
764.165
2.751
1.3
3.576
2
Evp outlet (w)
37.595
0.135
1.3
0.176
27.117
0.098
1.3
0.127
3
Turbine inlet (r )
563.472
2.028
4.988
10.119
563.472
2.028
4.995
10.132
4
Turbine outlet (r )
187.325
0.674
4.988
3.364
187.325
0.674
4.995
3.368
5
Pump inlet(r )
83.666
0.301
15.6
4.699
83.666
0.301
15.6
4.699
6
Pump outlet(r )
92.527
0.333
2.226
0.741
92.527
0.333
2.226
0.741
7
Cond inlet (w)
78.408
0.282
0
0
76.956
0.277
0
0
8
Cond outlet (w)
108.648
0.391
1.286
0.503
106.636
0.384
1.309
0.503
9
Pump
8.861
0.032
25.720
0.820
8.861
0.032
25.72
0.82
376.147
1.354
11.247
15.23
376.147
1.354
11.253
15.239
11 Condenser
30.24
0.109
1.286
0.14
66.44
0.239
1.309
0.313
12 Evaporator
734.154
2.643
2.226
5.883
737.048
2.653
2.226
5.906
10 Turbine
Ėx (GJ/h) c ($/GJ) Ċ ($/h) Ėx (kW)
Ėx (GJ/h)
c ($/GJ) Ċ ($/h)
30
Page 30 of 31
533
31
Page 31 of 31