New Journal and we have not received input yet 22 (2021) 100810
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Thermal Science and Engineering Progress
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Energy, exergy, economic, and environmental analysis of an organic
Rankine cycle integrating with infectious medical waste incinerator
Nattaporn Chaiyat a, b, c, *
a
School of Renewable Energy, Maejo University, Chiang Mai, Thailand
Thermal Design and Technology Laboratory (TDeT Lab), Thailand
c
Excellence Center on Environmental Friendly Smart Agriculture and Renewable Energy Technology (ECoT), Thailand
b
A R T I C L E I N F O
A B S T R A C T
Keywords:
4E model
Organic rankine cycle
Incinerator
Infectious medical waste
Waste-to-energy
This work presents the analysis of energy, economic, environmental (3E), and exergy (4E) impacts for verifying a
single implication value of renewable energy technology. An infectious medical waste incinerator combined with
an organic Rankine cycle with R-245fa as working fluid is investigated the overall impacts. The experimental
energy result are used to analyze an exergy efficiency of the quality level, a life cycle assessment (LCA) under the
environmental effect, a levelized cost of the economic perspective, and a 4E decision score. The study results
implied that the organic Rankine cycle-incinerator system could manage a refuse-derived fuel type 3 (RDF-3) of
184.42 kg/h from infectious medical waste to produce 23.65 kWe of power at an energy efficiency 0.91%, with at
the same time, an exergy efficiency was approximately 0.89%. The LCA was characterized with the use of steel at
a single score of approximately 0.00035Pt. The economic value was implied from a levelized energy cost of 0.153
USD/kWh under the 3E model, which was lower than that of a Feed-in Tariff (FiT) model for the solid-waste
power plant in Thailand of 0.209 USD/kWh. A levelized exergy costing per life cycle assessment of 0.0000986
USD Pt/kWh2 was investigated under the 4E model.
1. Introduction
The generation, consumption, efficiency, and sustainability of an
energy is the focus of many countries worldwide. The need for energy
management of fossil fuels and development new energy resources to
reduce greenhouse gas emissions and fuel consumption is currently a
major global problem.
As an energy strategy in Thailand, a very small power plant (VSPP) at
a power capacity lower than 1 MWe [1] by using a novel renewable
energy technology is promoted for sustainability electricity and reduce
environmental impacts, as shown in Fig. 1. A municipal solid waste
(MSW) power plant can develop to reduce costs, relieve fossil fuel pro­
curement problems, and accommodate bulk renewable energy genera­
tion in the future. A waste-to-electrical power plant is the main energy
approaches of the government for implementation by 2037 [1], in which
MSW power plants can provide a total power capacity of 900 MWe. A
Waste-to-Energy (WtE) power plant can offer high potential for sus­
tainable energy. In this context, an exergy impact, an energy costing,
and a life cycle assessment (LCA) play important roles in evaluating the
sustainability impacts and drawbacks of waste to power in comparison
to other renewable energy sources, which is the main objective of this
work.
The WtE works have been studied in the separate area analyses of an
energy efficiency, a combine energy quantity and quality in form of
exergy, an energy cost of economic, and an effect of environmental
result. The energy impact, Cheng et al. [2] and Mian et al. [3] studied the
WtE power plant in Changchun, China. The MSW was used for com­
bustion in a novel co-firing of MSW and coal with an incinerator. The
overall WtE efficiency was found to be approximately 14.6%. Nami and
Arabkoohsar [4] simulated a CHP plant powered by a fire-combustion of
waste to evaluate the thermal efficiency and found that the electricity
efficiency of the CHP European units was approximately 25%. In addi­
tion, Bademlioglu et al. [5] presented the nine fundamental process
parameters of working fluid type, pinch point temperature differences in
the evaporator and condenser, superheating temperature, evaporation
and condensation temperatures, heat exchanger effectiveness, turbine
and pump efficiencies for the ORC statistical evaluation. The best con­
dition was determined as A1B1C3D3E3F3G1H3I3, which the first and
second law efficiencies were 18.1% and 65.52%, respectively.
In terms of the exergy impact, Eboh et al. [6] evaluated enhancement
in a waste combustion process. Exergy study was justified to analyze the
* Address: School of Renewable Energy, Maejo University, Chiang Mai, Thailand.
E-mail address: benz178tii@hotmail.com.
https://doi.org/10.1016/j.tsep.2020.100810
Received 2 July 2020; Received in revised form 3 November 2020; Accepted 8 December 2020
Available online 15 December 2020
2451-9049/© 2020 Elsevier Ltd. All rights reserved.
N. Chaiyat
Thermal Science and Engineering Progress 22 (2021) 100810
Nomenclature
ULO
WD
WF
WP
x
Abbreviations and symbols
ALO
agricultural land occupation, (m2a)
CC
climate change, (kg CO2 eq)
CFm
characterized value of midpoint impact, (Unit eq)
CV
characterized value, (Unit eq)
EnA
energy costing per life cycle assessment, (USD/Pt)
ExA
exergy costing per life cycle assessment, (USD/Pt)
EQ
ecosystem quality, (Species⋅y)
FD
fossil depletion, (kg oil eq)
FE
freshwater eutrophication, (kg P eq)
FET
freshwater ecotoxicity, (kg 1,4-DB eq)
HH
human health, (DALY)
HT
human toxicity, (kg 1,4-DB eq)
i
interest rate, (%)
I
single score, (Pt)
IR
ionizing radiation, (kg U235 eq)
LEC
levelized energy cost, (USD/kWh)
LEnCA
levelized energy costing per life cycle assessment, (USD⋅Pt/
kWh2)
LExC
levelized exergy cost, (USD/kWh)
LExCA
levelized exergy costing per life cycle assessment, (USD⋅Pt/
kWh2)
MD
metal depletion, (kg Fe eq)
ME
marine eutrophication, (kg N eq)
MET
marine ecotoxicity, (kg 1,4-DB eq)
NLT
natural land transformation, (m2)
NP
normalization value of impact, (Person for target)
NR
normalization reference, (Unit eq/person⋅y)
OD
ozone depletion, (kg CFC-11 eq)
OM
operating and maintenance costs, (USD/y)
PMF
particulate matter formation, (kg PM2.5 eq)
POF
photochemical oxidant formation, (kg NMVOC)
r
discount rate, (%)
RD
natural resource, ($)
TA
terrestrial acidification, (kg SO2 eq)
TET
terrestrial ecotoxicity, (kg 1,4-DB eq)
TLI
total lifetime impact, (kg emission eq)
Greek
η
ψ
urban land occupation, (m2a)
water depletion, (m3)
weighting factor, (-)
weighting point, (Pt)
material, (Unit)
energy efficiency, (%)
exergy efficiency, (%)
Abbreviation
IC
incinerator
LCA
life cycle assessment
LCI
life cycle inventory
LCIA
life cycle impact assessment
MSW
municipal solid waste
MSWI
municipal solid waste incinerator
ORC
organic Rankine cycle
RDF
refuse derived fuel
VSORC very small organic Rankine cycle
VSPP
very small power plant
Subscript
AP
B
C
CW
CT
e
EH
Exp
G
HB
HF
HW
OP
OT
P
PP
absorber pump
boiler
condenser
cooling water
cooling tower
electricity
exhaust gas
expander
generator
hot air blower
hot fluid
hot water
oil pump
operating time
refrigerant pump
power plant
Fig. 1. Electricity situation for 2019 and electricity model for 2037 in Thailand.
overall system performance. The results indicated that an exergy
destruction of 64% could be enhanced at a highest exergy efficiency
increment of approximately 21%. Yamankaradeniz et al. [7] studied the
energy and exergy analysis of an ORC-geothermal system with a heat
exchanger. R-600a was used for hot fluid between 60 and 120 ◦ C at the
fixed pinch point temperature differences in evaporator and condenser.
The energy and exergy efficiencies were enhanced of approximately
6.87% and 6.21% respectively.
In terms of the environmental impact, Tsai and Kuo [8] reported the
Taiwan emissions from methane (CH4) and nitrous oxide (N2O) of a
municipal solid waste incinerator (MSWI) power generation. The output
results based on the carbon dioxide (CO2) equivalent were
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Thermal Science and Engineering Progress 22 (2021) 100810
Fig. 2. A schematic diagram of the VSORC-MSWI cycle.
approximately 76,000 ton CO2 eq/year and 88,000 ton CO2 eq/year,
respectively. Lou et al. [9] presented the LCA of the MSW at a capacity of
1500 ton/day, in which six LCA impact categories of three human
toxicity impacts, nutrient enrichment, global warming, and personal
equivalents, were considered. Ning et al. [10] used the ReCiPe and Ecoindicator 99 techniques to report the low environmental impact of the
mechanical grate compared with that of the fluidized bed. Abusoglu
et al. [11] compared fifteen impact categories on a hypothetical cement
kiln (CK) and a fluidized bed combustor (FBC).
The exergy and economic perspectives, Jack and Oko [12] presented
the exergoeconomic investigation of a municipal solid waste (MSW)
power generation in Nigeria, that was driven from steam of heat re­
covery process, which was similar to the findings of Tozlu et al. [13,14]
and Emrah et al. [15].
The thermodynamic and exergetic perspectives, Özahi et al. [16]
simulated an organic Rankine cycle (ORC) powered by the MSW fuel.
The exhaust gas was used as the main heat source of the power unit,
where an optimal working from n-hexane was suggested in the MSWORC system. Arabkoohsar and Nami [17] also simulated the energy
and exergy results of a smart waste-fired combined heat and power
(CHP) plant. Both efficiencies of the CHP unit were found by approxi­
mately 10% and 20% compared with the primary unit. Azami et al. [18]
similarly analyzed a MSW-to-energy boiler based on both efficiencies of
approximately 79% and 16%, respectively.
The energy and economic areas, the levelized cost of electricity in
renewable energy power plants was analyzed by various works, such as
Bano et al. [19] and Tu et al. [20]. From the energy, exergy, and eco­
nomic perspectives, Amirmohammad et al. [21] presented the WtE
power plant. The best performance values of the R-123 ORC system from
the energy, exergy, and exergoeconomic views were simulated to be
approximately 19.51%, 16.36%, and 24.65 $/GJ, respectively. Carneiro
and Gomes [22] studied a new design of the combined WtE and gas
turbine systems by using a conventional energy, and a new
environmental-economic approach. A case study configuration of 107
MWe was used as a demonstration, which implied that, a conventional
energy efficiency of 36% from input energy of 155 MWt. In the same
time, an ecological efficiency of 89% and an electricity cost of 64–89
USD/MWh was also represented.
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Thermal Science and Engineering Progress 22 (2021) 100810
Fig. 3. Hybrid steam sterilization process for infectious medical waste [26].
From the aforementioned literature data, it implied that the WtE
power generation technologies were studied by various works. The en­
ergy, exergy, economic, and environmental concepts were separately
used to evaluate the best method to produce power from waste. It can be
concluded that an integrated model of the 3E and 4E models to be a
single decision single value is not represented in recent literature. In
addition, the research gap and novelty in a new knowledge impact for
comparing and verifying the implications of renewable energy tech­
nology is also not defined as a new renewable energy knowledge. The
integrating value of the overall implications can use to select the suitable
technology for the renewable energy project in the future.
An approach using a very small organic Rankine cycle (VSORC) for
generation electrical power powered by the infectious-MSWI is proposed
and experimentally evaluated the 3E and 4E single score values.
The objectives of this work are as follows:
Table 1
Specifications of the VSORC-MSWI prototype.
Systems
Descriptions
• 1.09-m3 combustion chamber
• 250-kW double-tube heat
exchanger
• 30-cm volcanic-soil wall
• 2-mm steel wall
• 1.50-kWe hot air blower
• 1.147-m3 double absorber
• 1-mm spray nozzle
• 0.25-kWe absorber pump
• 1.099-m2 reheat tube
• 1.815-m2 cooling unit
• 0.157-m3 vacuum filter
• 280-kW plate heat exchanger
(boiler)
• 55-kg R-245fa (from weighing
measurement)
• 30-kW twin screw compressor
• 70–85% isentropic efficiency of
screw expander
• 25-kWe induction alternator
• 250-kW shell and tube heat
exchanger (condenser)
• 80-TR (ton refrigerant) cooling
tower
• 2.2-kWe cooling pump
• 1.2-kWe cooling fan
• 1.5-kWe vertical multistagerefrigerant pump
• 2.2-kWe vertical multistage-gear
pump
• 60-L vertical tank (oil and vapor
separator)
• 2.2-kWe hot fluid pump
• 2.2-kWe hot water pump
• Maximum pressure of 15 bar
(absolute pressure)
• Maximum volume capacity of
1,500 L
• Set control volume capacity of
1,000 L
• Volume flow rate of
approximately 3.0–4.5 L/s
To design and implement a new VSORC-MSWI powered by infectious
medical waste.
To investigate the energy and exergy system equations of the incin­
erator unit, the ORC cycle, and the VSORC-MSWI system.
To analyze a single score from the LCA method of the novel system.
To analyze the energy, exergy, economic, and environmental results
of the WtE power generation system to be a levelized exergy costing
per life cycle assessment.
2. System description
A simplify working diagram of the integrated VSORC-MSWI system
is depicted in Fig. 2. Infectious medical waste is used to thermal power
the electrical power system. Three main systems are combined to pro­
duce WtE from the hot fluid storage tank, incinerator, and ORC units.
The first system, the incinerator system, is selected for solid fuel
transformation technology. The solid fuel is fed though a small chimney
at the front side of the combustion chamber. Solid waste (a refusederived fuel type 3, RDF-3) is used as the combustion substrate, after
which heat is generated (points 1–3 h). The storage tank is used to
accumulate the heated fluid to supply the purified liquid fluid to the
power unit. The combustion gas (exhaust) moves via the treatment unit.
A hot air blower is used to force the exhaust gas into a double-absorber
set, which all particulates and pollution such are reduced by an ab­
sorption technique from a spray water nozzles. These forms of air
pollution are controlled under the standards of the Pollution Control
Department, Thailand [23]. Then, the reheat tube, cooling set, and
vacuum filter are finally treated the dioxin compound of dibenzofurans
(PCDF) and polychlorinated dibenzo-p-dioxins (PCDD). Next, all clean
gas is circulated into the environment by using a main exhaust stack.
However, the bypass exhaust stack can be switched into operation in
cases of treatment service and maintenance. The byproduct of bottom
ash is rejected below the combustion chamber.
The second system, the ORC system, is used for the heat-to-power
technology. The hot fluid (points 4 h-6 h) is pumped from the storage
tank into the power unit (points 1–7). The ORC working fluid in the
liquid phase is pumped to transfer heat at the ORC boiler. A dry type or
an isentropic type of refrigerant is popular as a refrigerant loop (points
1–4 and 7). The superheated vapor is intently generated from the boiler
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N. Chaiyat
Thermal Science and Engineering Progress 22 (2021) 100810
Fig. 4. System boundaries of the VSORC-MSWI system.
component to efficiently drive the expander during the heat to thermal
power process. A commercial compressor, such as a scroll and screw
type, is popularly applied as the expander in the VSORC unit. A lubricant
oil loop (points 4–6) is designed for reducing the friction loss in the
reversed expander. Thus, in the expander, the refrigerant and lubricant
oil is mixed in the expander and sent to separate the mixed fluid at the oil
and separator tank. The generator is a work-to-power component that is
mechanically connected with the expander. Then, the refrigerant at the
vapor phase is divided from the oil and vapor separator and flows into
the condenser. This working fluid is extracted heat and condensed by
using a cooling loop (points 1c-3c), which is driven from the cooling
pump and cooling tower. Then, the condensed working fluid is pumped
to the boiler again, and a new ORC cycle starts.
Fig. 5. A correlation of midpoint categories, endpoint indicators, and single score.
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N. Chaiyat
Thermal Science and Engineering Progress 22 (2021) 100810
3. Methodology
3.1. Test rig
The integrated VSORC-MSWI test rig is comprised of a 250-kg/h
incinerator, a 1.5-ton storage tank, and a 25-kWe ORC. This integrated
system is supplied a heat source from a mixed RDF-3 fuel, in which in­
fectious medical waste and municipal waste are sterilized by hybrid
steam sterilization (HSS) [24], as shown in Fig. 3. Seven sterilization
processes are used: 1) loading the infectious medical and municipal
wastes into the machine, 2) shredding and reducing the materials at a
volume of 80% by cutting to a size of less than 1 cm, 3) heating with
steam at a superheated temperature of 138 ◦ C, 4) sterilization process
under high heat pressure at an absolute pressure of 4.5 bars and an
operating time of approximately 10 min, 5) cooling with clean water to
decrease the waste temperature, 6) draining the water out of the ma­
chine, and 7) unloading the treated solid waste. Next, this sterilized solid
waste at a low heating value (LHV) of approximately 26.92 MJ/kg from
the verified data [25], is transported for the WtE process. All specifi­
cations of the VSORC-MSWI prototype are presented in Table 1.
The VSORC-MSWI system is measured and recorded the operating
data by the real-time monitoring system via www.tdetlab.com/room/
dashboard. Four types of sensors—a temperature sensor, pressure
sensor, mass flow rate sensor, and power logger—are used to link the
experimental data with three types of electronic boards: an Arduino
Fig. 6. The conceptual design of the 3,4E-Chaiyat models.
Table 2
Comparison equations of the 3E and 4E integrated decision scores.
Properties
3E model
4E model
Incinerator
Capacity of solid waste
QRDF = ṁHW LHVRDF
QLoss = QRDF − QHF − QEH
ExRDF = fex,RDF ṁHW LHVRDF
(
)
T0
ExHF = QHF 1 −
THF,IC,i )
(
T0
ExEH = QEH 1 −
TEH,IC,o
ExLoss = ExRDF − ExHF − ExEH
ηIC =
ψ IC =
Capacity of hot fluid
Capacity of exhaust gas
Capacity of heat loss
Incinerator efficiency
ORC
ORC efficiency
Power plant efficiency
VSORC-MSWI (energy and exergy scores)
VSORC-MSWI efficiency
Environment
Characterized value
Midpoint characterization factor
Normalization value
Weighting point
Weighting factor
Single score
Single score per functional unit (environmental score)
Economic
Costing per life cycle assessment
Discount rate
Levelized costing (economic score)
Integrated decision score
Levelized costing per life cycle assessment
QHF = ṁHF (hHF,3h − hHF,2h )
QEH = ρEH vEH AEH,Stack (hEH,Stack,i − h0 )
QHF
QRDF + WHB + WAP
ηORC =
ηPP =
WExp − WP − WOP
WORC
=
ṁHW (hHW,4h − hHW,5h )
QHW,B
WPP
WORC − WCT − WCP
=
ṁHW (hHW,4h − hHW,5h )
QHW
ηVSORC− MSWI =
WVSPP− MSW
QRDF
ExHF
ExRDF + WHB + WAP
WExp − WP − WOP
(
)
T0
QHW,B 1 −
THW,ORC,i
W
W
− WCT − WCP
(
)
ψ PP = PP = ORC
T0
ExHW
QHW 1 −
THW,ORC,i
ψ ORC =
WORC
=
ExHW,B
ψ VSORC− MSWI =
WVSPP− MSW
ExRDF
CVj = CFj xj
∑
CFmx,c = j CVj
CVEx,j = CFj xEx,j
∑
CFmEx,x,c = j CVEx,j
NPj =
NPEx,j =
CFmx,c
NRj tPd
WPj = WFj NPj
CFmx,c,Reference year
CFm
∑ x,c,Target year
Im,Pd,Total = j WPj
∑
j WPj
Im,Pd,1 Unit = ∑N
(W
VSORC− MSWI,net )tOP
t=1
CFmEx,x,c
NRj tPd
WPEx,j = WFj NPEx,j
WFj =
Inv +
∑N
t=1
OM
(1 + r)t
Ix,Pd,Total =
∑
j WPEx,j
∑
j WPEx,j
Ix,Pd,1 Unit = ∑N
t=1 (WVSORC− MSWI,net )tOP
Inv +
∑N
t=1
OM
(1 + r)t
EnACCHP =
TLI
) m,Pd Total
(
1 + iReal
− 1
r =
1 + iInflation
∑n
OM
Inv + t=1
(1 + r)t
LEnCCCHP = ∑
n WORC,net tOT
t=1
(1 + r)t
ExACCHP =
LEnCACCHP = LEnCCCHP Im,Pd 1 Unit
LExCACCHP = LExCCCHP Ix,Pd 1 Unit
6
TLIx,Pd Total
∑
OM
Inv + nt=1
(1 + r)t
LExCCCHP = ∑
n WORC,net tOT
t=1
(1 + r)t
N. Chaiyat
Thermal Science and Engineering Progress 22 (2021) 100810
Fig. 7. The incinerator performance curves.
based on an energy cost per functional unit and an energy cost per the
LCA single score to determine the 3E integrated decision score, as pre­
sented in Table 2.
The 4E model is proposed to characterize the results of the energy,
exergy, economic and environmental analyses, as also shown in Fig. 6.
The exergy concept, as a more accurate measurement of the system
performance, deeply evaluates the input exergy, which is converted to
an output benefit. The 4E integrated decision score of a levelized exergy
costing per life cycle assessment (LExCA) is elucidated in terms of an
exergy cost per functional unit and an exergy cost per the LCA single
score.
Both conceptual assessments are referenced in our previous work
[29] and are named “3,4E-Chaiyat models”. The first law of thermody­
namics in terms of enthalpy, heat capacity, and energy efficiency and the
second law of thermodynamics in terms of entropy, exergy capacity, and
exergy efficiency are used to analyze the system performances. In
addition, the single score from the LCA method and the levelized cost
from the economic analysis are also used to consider the overall impli­
cations from the renewable energy project. All of the characterization
equations used in the 3E and 4E models are specified in Table 2.
platform, a network attached system (NAS), and a programmable logic
controller (PLC).
3.2. LCa
The VSORC-MSWI boundary for the LCA of all the materials, fuels,
emissions, and energies in a construction process, an operation phase,
and a decommissioning process of the recycle and landfill methods is
depicted in Fig. 4. The most important consequence of adhering to the
ISO standards of 14,040 (principles) and 14,044 (requirements) is
considered for the careful documentation of the goal, scope and inter­
pretation issues. Thus, four processes—a goal and scope definition, an
inventory analysis, an impact assessment, and an interpretation—from
the ISO methods are referenced to determine the environmental
impacts.
Frist process, the environmental impacts of the VSORC-MSWI system
for generating electricity from RDF-3 of infectious medical waste is the
goal definition of this work. The system boundary and scope under a
cradle-to-grave approach for a life span of 20 years and a functional unit
of 1 kWh are considered, as shown in Fig. 4.
Second process of the inventory analysis, all of the raw materials,
emissions, and energies that enter and leave the several stages of the
VSORC-MSWI’s life cycle are collected in the life cycle inventory (LCI).
While, all the raw material and energy data of the infectious medical
treatment system are neglected because this system is out of the LCA
framework of this study.
Third process of the impact assessment, the ReCiPe2016 method
[27] under the SimaPro database [28] is considerably selected to
analyze eighteen midpoint impact categories of the life cycle impact
assessment (LCIA), as shown in Fig. 5.
Last process of the interpretation, the midpoint impact categories
from the LCIA procedure are determined a LCA single score of the
VSORC-MSWI system. The single value is defined from the global
normalization point of the SimaPro database [28], and is specially
considered the weighting set from the environmental data in 2019 and
the environmental aim by 2037 of Thailand.
4. Results and discussion
4.1. Energy and exergy performance curves
In this study, a linear regression analysis was used to verify the en­
ergy and exergy performance curves of the incinerator, ORC, and
VSORC-MSWI systems under the static parameters of a coefficient of
determination (R2) higher than 0.8 and a probability value (P-value) less
than 0.05. The two main input variables of the heat source (THW,i) and
heat sink (TCW,i) temperatures were assessed in terms of the different
values (THW,i – TCW,i). This concept was considered from the Carnot
cycle efficiency. When, the temperature different between heat source
and heat sink increased, the Carnot efficiency decreased.
The incinerator performance curves, presented in Fig. 7, are sharply
increased when the difference in the temperature between the heat
source and heat sink increases. The average values of the energy (ηIC)
and exergy (ψIC) efficiencies were observed to be approximately 31.66%
and 4.05%, respectively, at the very high reliability of the static decision
values in terms of R2 at an excess of 0.80 and P-value at a less of 0.05.
The exergy value was lower than the energy value because the incin­
erator operated at a very high temperature level. Thus, the exergy value
3.3. The 3E and 4E models
The 3E model is intended to identify and justify the effects of energy,
economic, and environmental impacts as represented in Fig. 6. The 3E
model uses a levelized energy costing per life cycle assessment (LEnCA)
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Thermal Science and Engineering Progress 22 (2021) 100810
Fig. 8. The ORC performance curves.
Fig. 9. The VSORC-MSWI performance curves.
was sharply reduced when the ambient temperature was used to refer to
the exergy methodology.
Energy efficiency of the incinerator unit was directly driven from hot
water temperature. At the steady state, the incinerator behavior was
operated at the high process temperature, which implied that the
optimal thermal performance of incinerator was revealed at the high
level of hot water temperature. Thus, the use of low level temperature
for the incinerator effected to the best combustion conditions. Low water
temperature could increase the heat transfer rate between, on the other
hand, this fluid could decrease the temperature of combustion heat.
The ORC performance curves are elucidated as presented in Fig. 8;
the curves are nearly constant when the temperature difference is
increased. The average energy (ηORC) and exergy (ψORC) efficiencies
were approximately 8.05% and 39.98%, respectively, at the acceptable
reliability value of a R2 of nearly 0 and a P-value of approximately 0.81.
The exergy trend was higher than the energy trend by approximately 2
times because the ORC system could generate high-quality energy by
using a low-temperature level.
The increase of hot water temperature effected directly to enhance
the enthalpy, heating rate at the ORC boiler, high side pressure, kinetic
energy of working fluid, mechanical power of the expander, electrical
power of the generator, respectively. On the other hand, the increased
fluid temperature was also affected to increase consumption electrical
power of the refrigerant and oil pumps, which influenced that to net
electrical power of the ORC system. However, the overall image of this
technique was the advantageous impact for the ORC system.
In the case of the decrease of cooling water temperature, this tech­
nique could also enhance the ORC efficiency. When, the cooling fluid
temperature decreased, the working fluid temperature and pressure at
the ORC condenser similarly decreased. Thus, the different value of the
high and low pressures increased, that resulted to the gross power of the
expander and generator, respectively. This technique was one of the
improvement efficiency method, which had been published by Chaiyat
et al. [30], Ghasemian and Ehyaei [31].
8
N. Chaiyat
Thermal Science and Engineering Progress 22 (2021) 100810
Fig. 10. The performance data under the steady-state condition of the VSORC-MSWI system.
The VSORC-MSWI performance curves are investigated as presented
in Fig. 9; the curves are slightly enhanced by increasing the difference in
the heating and cooling source temperatures. The average energy
(ηVSORC-MSWI) and exergy (ψVSORC-MSWI) efficiencies were approximately
0.91% and 0.89%, respectively, at high R2 and P-values. These values
was slightly low, because used many electrical components especially
the hot fluid pump and the hot water pump. Both pumps could reduce to
be only one pump by integrated the hot fluid and hot water loops, which
were operated as the parallel connection to be the same loop as the
cascade connection. Therefore, the modified hot fluid loop could
improve the net electrical power. This disadvantage point will develop
in the recent future of the revolution VSORC-MSWI system.
The analysis results implied that both VSORC-MSWI efficiencies
were directly affected by the temperature of fluid entering the WtE
system. Both thermal performance curves were nearly because the same
output power and similar input energy values were used to determine
Table 3
The VSORC-MSWI responsible for the average value of all impact categories.
Steel
Concrete
Paint
Glass
wool
Sanitary
Gypsum
All
plastic
74.67%
1.00%
1.11%
1.78%
1.00%
1.78%
3.22%
Flat
glass
1.33%
Aluminum
Lubricant
Brass
Sand
Transport
1.00%
1.00%
2.94%
1.00%
1.22%
R245fa
0.50%
the energy and exergy values. Thus, the economic and environmental
perspectives receive additional attention in the next section. In addition,
Fig. 10 provides the measurement values under the steady-state condi­
tion of the VSORC-MSWI from Figs. 7 to 9, which is used in the 3E and 4E
assessment.
9
N. Chaiyat
Thermal Science and Engineering Progress 22 (2021) 100810
Table 4
The LCA impact categories and single score.
Table 5
The analysis results of the 3E and 4E models.
Impact
TLIm,Pd,
1
Total
TLIx,Pd,
1
Total
Im,Pd,1 Unit
(Pt)
Ix,Pd,1 Unit
(Pt)
Climate change (kg CO2
eq)
Ozone depletion (kg CFC11 eq)
Particulate matter
formation (kg PM2.5
eq)
Terrestrial acidification
(kg SO2 eq)
Freshwater
eutrophication (kg P
eq)
Marine eutrophication
(kg N eq)
Human toxicity (kg 1,4DB eq)
Terrestrial ecotoxicity
(kg 1,4-DB eq)
Freshwater ecotoxicity
(kg 1,4-DB eq)
Marine ecotoxicity (kg
1,4-DB eq)
Metal depletion (kg Fe
eq)
Fossil depletion (kg oil
eq)
Photochemical oxidant
formation (kg NMVOC)
Ionizing radiation (kg
U235 eq)
Agricultural land
occupation (m2a)
Urban land occupation
(m2a)
Natural land
transformation (m2)
Water depletion (m3)
Sum
4.43E+04
4.43E+04
3.28E− 06
3.28E− 06
2.45E− 03
2.48E− 03
1.44E− 07
1.46E− 07
8.72
8.72
7.46E− 07
7.46E− 07
3.75E+01
3.75E+01
1.00E− 06
1.00E− 06
1.47E+01
1.47E+01
3.14E− 05
3.14E− 05
5.25E+01
5.25E+01
5.18E− 06
5.18E− 06
4.28E+04
4.28E+04
8.11E− 05
8.11E− 05
3.04
3.04
4.78E− 07
4.78E− 07
8.15E+02
8.15E+02
6.57E− 05
6.57E− 05
8.10E+02
8.10E+02
9.28E− 05
9.28E− 05
3.86E+04
3.86E+04
4.81E− 05
4.81E− 05
2.64E+03
2.65E+03
1.66E− 06
1.66E− 06
6.90E+01
6.90E+01
1.29E− 07
1.30E− 07
1.13E+03
1.13E+03
2.28E− 07
2.28E− 07
4.97E+02
4.97E+02
1.29E− 07
1.29E− 07
1.18E+02
1.18E+02
3.40E− 07
3.40E− 07
2.16
2.17
1.55E− 05
1.56E− 05
1.83E+03
1.34E+05
1.83E+03
1.34E+05
5.46E− 07
3.48E− 04
5.46E− 07
3.49E− 04
Properties
3E model
4E model
Incinerator
Solid waste
Hot fluid
Exhaust gas
Heat loss
Incinerator efficiency
QRDF = 1,379.02 kW
QHF = 246.25 kW
QEH = 82.75 kW
QLoss = 1,050.02 kW
ηIC = 17.84%
ExRDF = 1,406.60 kW
ExHF = 48.29 kW
ExEH = 9.78 kW
ExLoss = 1,348.53 kW
ψIC = 3.43%
ORC
Heat inlet at the boiler
ORC efficiency
Power plant efficiency
ηORC = 8.52%
ηPP = 7.29%
QHW,B = 240.36 kW
ExHW,B = 46.78 kW
ψORC = 43.75%
ψPP = 37.43%
ηVSORC-MSWI = 0.91%
ψVSORC-MSWI = 0.89%
Im,Pd,Total = 297.60Pt
Im,Pd,1 Unit =
0.000348Pt
Ix,Pd,Total = 297.68Pt
Ix,Pd,1 Unit = 0.000349Pt
VSORC-MSWI
Efficiency
Environment
Single score
Single score per functional
unit
Economic
Discount rate1
Total lifetime impact
Maintenance cost3,4
Operating cost3,5
Operating and maintenance
costs
Costing per life cycle
assessment2,3
Levelized costing2,3
Integrated decision score
Levelized costing per life
cycle assessment
r = 4.41%
TLIx = 1.34E+05 kg
TLIm = 1.34E+05 kg
emission eq
emission eq
OMMaintenance = 1,022 USD
OMOperating = 3,807 USD
OM = 4,829 USD
EnA = 1.290 USD/kg
emission eq
LEnC = 0.153 USD/
kWh
ExA = 1.290 USD/kg
emission eq
LExC = 0.153 USD/
kWh
LEnCA = 8.95E− 05
USD⋅Pt/kWh2
LExCA = 8.96E− 05
USD⋅Pt/kWh2
Remark: 1 Interest (iReal) and inflation (iInflation) rates are 6.5% and 2.0%,
respectively [33].
2
Working time (tOT) is 12 h/d and operating day is 350 d/y.
3
One USD is 32.663 Baht [33].
4
OM consists of cleaner and service charge for the OM period at 2 time/y.
5
The minimum labor cost in Thailand is 9.49 USD/person⋅day.
Remark: 1 Unit of each impact is referred from each equivalent unit.
power generation units essentially drove all eighteen midpoint impact
categories. These impacts included the energy and exergy perspectives
were similarly revealed based on a functional unit of 1 kWh. In addition,
the LCIA results suggested that the highest impacts of a construction
phase of 87.16%, followed by an operation phase of 11.94%, and a
decommissioning phase of 0.90%, were investigated for the VSORCMSWI system.
In the interpretation procedure, as also presented in Table 4, all LCA
impacts (total lifetime impact, TLI) were normalized and weighted into a
single score indicator result based on the energy (Im,Pd,1 Unit) and exergy
(Im,Pd,1 Unit) methods. All LCA impacts were compared with a normali­
zation reference (NR) value, which was referred from the standard
global score (the ReCiPe2016 method). After that, a weighting point
(WP) based on the Thailand political targets and goals were used to the
energy and exergy single values. In addition, the details of environ­
mental analysis such as the each LCA characterization factor, NR, WP
values were presented in our previous work [32]. It could be concluded
that the final LCA single scores in terms of the energy and exergy aspects
were approximately 0.000348Pt and 0.000349Pt, respectively.
4.2. LCA
The LCI of all the raw materials and energies in three phases of the
VSORC-MSWI, as shown in Fig. 10 and Table 3. Steel at a mass capacity
of 11.56 tons was revealed in the construction phase as the main raw
material following by a copper of 426 kg, a glass fiber reinforced plastic
of 285 kg, a polyvinylchloride (PVC) of 152 kg, a brass of 81.5 kg, a high
density polyethylene (HDPE) of 40 kg, and etc. In addition, in the
operation phase, RDF-3 of infectious solid waste at a combustion mass of
13,000 tons and electricity at a power consumption of 802 MWh were
supplied to produce a total electrical power output of 1021 MWh and a
net electrical power output of 854 MWh. The air pollution from the
operating phase was found in form of a carbon dioxide of 7070 kg, a
carbon monoxide of 4000 kg, a nitrogen dioxide of 3500 kg, a nitrogen
monoxide of 8500 kg, a sulfur dioxide of 210 kg, a nitrogen of 10,000 kg,
a methane of 105 kg. In the same time, the water pollution—a biological
oxygen demand of 4.07 m3, a chemical oxygen demand of 7.53 m3, a
nitrogen of 0.25 m3, and a phosphorus of 0.001225 m3—and bottom ash
at a mass capacity of 833 tons were also found in the working time. After
a life span of 20 years, approximately 55.29% of all the materials from
the construction phase could be recycled. Other materials, at approxi­
mately 1.04% of the construction phase, were disposed of by the landfill
method. In the note that, more information of the LCI data can assess
from our previous work [32].
From Table 4, the LCIA found that steel was the main cause affecting
all the impact categories. Steel from the construction phase of the hot
fluid piping, hot water tank, infectious medical waste incinerator, and
4.3. The 3E and 4E model results
From the results of the 3E and 4E models as specified in Table 5, it
can be seen that the total capital cost was 109,260 USD from an ORC cost
of 82,398 USD, a hot fluid tank cost of 16,480 USD, a 55-L working fluid
cost of 1,813 USD, an incinerator cost of 6,592 USD, and a piping cost of
1,978 USD. The annual operating and maintenance cost was 4829 USD/
y based on a minimum labor cost in Thailand (350 day/year) of 10.88
10
N. Chaiyat
Thermal Science and Engineering Progress 22 (2021) 100810
USD/day and a service maintenance cost (2 times per year) of 1022
USD/year. In contrast, an output power generation of approximately
51,240 kWh/y could be produced from the VSORC-MSWI system.
In the 3E (energy, economic, and environment) model, a LEnC value
of 0.153 USD/kWh was observed, which was lower than that of a Feed-in
Tariff (FiT) model for the solid-waste power plant at a power capacity
lower than 1 MWe of 0.209 USD/kWh. In addition, this result was also
economical in the infectious management range of 0.494–0.659 USD for
1 kg medical waste in Thailand. Moreover, a LEnCA value of 8.95E− 05
USD⋅Pt/kWh2 was estimated for the 3E final parameter.
Furthermore, the 4E model was determined under the exergy, eco­
nomic and environmental perspectives. A single LExCA score was found
to be approximately 0.00009 USD⋅Pt/kWh2. This value is the decision
point for comparison with other power plants to investigate the ad­
vantageous behavior under a comprehensive process. The San Kam­
phaeng geothermal system, Chiang Mai, Thailand, a combined system
with an absorption cooling of 15 kW, a drying of 20 kW), and an ORC
power generation of 10 kWe based on our previous work [29] at a LExCA
of 0.008 USD⋅Pt/kWh2, is used for comparison with the VSORC-MSWI
system. The 4E decision value implied that the infectious-WtE technol­
ogy shows an advantage compared with the combined cooling, heating,
and power (CCHP) geothermal system. The main reason is the high
amount of raw material in the environmental impact of the CCHP
geothermal system at the high value energy and exergy scores of
approximately 0.026Pt. In addition, the energy, exergy, and economic
results of both power plants are the same. Thus, the 4E decision point of
the geothermal system is higher than that of the WtE power plant of this
study.
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5. Conclusions and recommendations
The analysis of energy, exergy, economic (3E), and environmental
(4E) impacts from the infectious medical waste incinerator and ORC
system could be concluded as follows:
• The VSORC-MSWI system powered by infectious medical waste
could be managed RDF-3 at a combustion rate of 184.42 kg/h.
• The VSORC-MSWI system could produce a gross electrical power of
23.65 kWe under the energy and exergy efficiencies of approximately
0.91% and 0.89%, respectively.
• The LCA was characterized by eighteen midpoints using the database
in SimaPro software to evaluate the energy and exergy single scores
of approximately 0.000348Pt and 0.000349Pt, respectively, which
were mainly driven from steel in the construction process.
• The LEnC and LEnCA values of 0.153 USD/kWh and 8.95E− 05
USD⋅Pt/kWh2, respectively, were observed from the 3E model.
• The LExCA value of approximately 0.00009 USD⋅Pt/kWh2 was
finally determined under the single score of 4E model.
For the future study, the hot fluid and hot water loops as the parallel
connection should be integrated to be one cycle as the cascade
connection. The modified hot fluid loop can improve the net electrical
power and the system efficiency, respectively.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Acknowledgements
The author would like to thank Maejo University, Thailand for sup­
porting testing facilities and research budget.
11
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Thermal Science and Engineering Progress 22 (2021) 100810
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12