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Solar thermal Organic Rankine Cycle as a renewable energy option

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The objective of the paper is to study the feasibility of an Organic Rankine Cycle (ORC) driven by solar thermal energy as a renewable energy option for small and medium sized commercial usage, power generation of less than 10MW. ORC is principally a conventional Rankine Cycle that uses organic compound as the working fluid instead of water and it is particularly suitable for low temperature applications. Appropriate organic compound includes refrigerants and azeotropes. The ORC and the solar collector are sized according to the solar flux distribution in Malaysia. According to Malaysia Metrological Department, Kota Kinabalu has the highest yearly average of solar radiation in the country for year 2003, for this reason it is chosen for the location of study. The power generation system consists of two cycles, the solar thermal cycle that harness solar energy and the power cycle, which is the ORC that generates electricity. The solar thermal cycle circulates heat transfer fluid (HTF) in the cycle and harness thermal energy from the sun and transfers it to the organic compound in the ORC via a heat exchanger. Components in the power cycle or ORC include an ORC turbine for power generation, a condenser for heat rejection, a pump to increase the pressure and a heat exchanger. The HTF selected in this analysis is Therminol VP3, which is currently used for commercial solar thermal applications. For this research, 2 organic compounds were analyzed, R123 and isobutane. These two compounds are optimized for selection.
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Jurnal Mekanikal
December 2005, No. 20, 68 - 77
Cheng Eng Cong1
Sanjayan Velautham
Amer Nordin Darus
Department of Thermo-Fluids
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
The objective of the paper is to study the feasibility of an Organic Rankine Cycle (ORC)
driven by solar thermal energy as a renewable energy option for small and medium sized
commercial usage, power generation of less than 10MW. ORC is principally a
conventional Rankine Cycle that uses organic compound as the working fluid instead of
water and it is particularly suitable for low temperature applications. Appropriate organic
compound includes refrigerants and azeotropes. The ORC and the solar collector are
sized according to the solar flux distribution in Malaysia. According to Malaysia
Metrological Department, Kota Kinabalu has the highest yearly average of solar radiation
in the country for year 2003, for this reason it is chosen for the location of study. The
power generation system consists of two cycles, the solar thermal cycle that harness solar
energy and the power cycle, which is the ORC that generates electricity. The solar thermal
cycle circulates heat transfer fluid (HTF) in the cycle and harness thermal energy from the
sun and transfers it to the organic compound in the ORC via a heat exchanger.
Components in the power cycle or ORC include an ORC turbine for power generation, a
condenser for heat rejection, a pump to increase the pressure and a heat exchanger. The
HTF selected in this analysis is Therminol VP3, which is currently used for commercial
solar thermal applications. For this research, 2 organic compounds were analyzed, R123
and isobutane. These two compounds are optimized for selection.
Fossil fuel consumption in the recent years has been increasing and the burning of
fossil fuel is said to be a major contributor towards global warming, air pollution
and ozone depletion. Besides the environment, the fossil fuel price fluctuates
considerably, with the price of the petroleum reaching as high as USD 53 [1].
Such a high price will take a toll on the economy of any country especially when
Malaysia becomes a net importer of fossil fuel. Currently, 91.9% of Malaysia
power generation uses fossil fuels. In recent years, Malaysia plans to reduce the
reliance on fossil fuel by introducing renewable energy as the 5th Fuel in the 8th
1 Corresponding author, E-mail:
Jurnal Mekanikal, December 2005
Malaysia Plan [2]. In the 8th Malaysia Plan, renewable energy sources are set to
increase its power generation share to 5% of the total fuel mix in Malaysia.
Therefore, it is pertinent to explore renewable energy usage to generate
electricity. For a conventional Rankine Cycle, it is efficient to employ low-grade
heat source. Most renewable energy sources, for example solar and biomass are
considered as low-grade heat sources because the heat energy supplied is much
less compared to fossil fuel. Therefore in this study, it is proposed the use of solar
thermal energy for sustainable power generation using the Organic Rankine Cycle
(ORC). An example of a successful commercialized solar based power generation
systems is the Solar Electricity Generation System (SEGS) in America, which
generates 354 MW of electricity a year [3].
2.1 Solar Thermal Cycle
Solar radiation can be divided into 2 components, direct radiation and diffuse
radiation. Direct or beam radiation is the radiation that arrives at the ground
without being scattered by clouds. The scattered radiation is known as diffuse
radiation. The total radiation received; the sum of beam and diffuse, is called
global radiation.
There are two main types of solar collectors available in the market,
concentrated solar collectors and non-concentrated solar collectors. Concentrated
collectors include the parabolic trough collector, the parabolic dish collector and
the solar tower collector; while the flat plate collector is a non-concentrated
collector. Concentrated collectors only harness direct radiation whereas non-
concentrated collectors collect global radiation [4]. For Malaysia, more diffuse
radiation is received as cloudy skies occur more frequently. Concentrated
collectors have higher operating temperature range of between 500°C and 1200°C
[5] while the non-concentrated collector, example the flat plate collector, operates
at temperatures from 80°C to 180°C [3]. The absorber surface temperature, Tab,
for a concentrated collector is calculate using,
ab ab
=− (1)
where Aap = aperture area
S = solar flux
= Stefan-Boltzman constant
Aab = absorber area
= collector efficiency
According to the Malaysia Metrological Department [6], Kota Kinabalu has a
yearly average global radiation of 1.6 MJ/m2. Diffuse radiation is calculated using
correlations from Orgill and Hollands [4]. The direct solar radiation calculated for
Kota Kinabalu is 1.01 MJ/m2. By using Orgill and Hollands Correlation, diffuse
radiation can be found as:
Jurnal Mekanikal, December 2005
I (2)
where clear sky index,
I is the measured global radiation and Io is the calculated global radiation which is
a function of latitude, day of the year and solar time for the location of study.
Direct radiation is obtained by subtracting the diffuse radiation value from the
global radiation.
2.2 Organic Rankine Cycle
Components that make up an ORC are similar to the conventional Rankine Cycle.
The layout of an ORC is as shown in Figure 1. The efficiency of solar collectors
had been rigorously studied, therefore the efficiency of various collectors are
cross-referenced from other studies. Assuming an ideal cycle, the mathematical
formulations for the components in an ORC are,
1) Feed pump to increase fluid pressure. Pump work,
34 3P
2) Condenser to reject heat to the environment, normally seawater. Heat
3) Heat exchanger to transfer heat from heat source to the working fluid. The
heat source is equals to the solar thermal energy collected by the collector.
Heat received,
4) Turbine for work conversion. Turbine work,
5) Cycle thermal efficiency, out
Where m
&= mass flow
= specific volume
h = enthalpy P = Pressure
Figure 1: A simple diagram of ORC
Pump WP
Jurnal Mekanikal, December 2005
Hung et. al has studied numerous organic fluids as a working fluid for Organic
Rankine Cycle [7]. Two organic compounds are studied in this study, R123 and
isobutane. These fluids are selected based on the criteria for an ideal Rankine
Cycle fluid suggested by Nag [8]. R123, an isentropic fluid, was shown to deliver
good results as per Yamamoto et. al [9]; while according to Larjola [10] isobutane
is a dry fluid and is recommended for low temperature utilizations. These two
working fluids are chosen to study the effects of different working fluids on the
ORC. For R123, the thermodynamic properties were obtained from the Modified
Benedict-Webb-Rubin (MBWR) equation of state from Younglove and McLinden
[11]. For isobutane, the thermodynamic properties are also obtained from the
MBWR equation of state which was tabulated by Younglove and Ely [12].
A parametric study was carried out to obtain the cycle efficiency of the ORC
along the saturated vapor line in the subcritical region for R123 and isobutane.
This was done in order to make the ORC’s efficiency closer to the Carnot Cycle
efficiency. Another important aspect is the limitation of the solar thermal
collector’s operating temperature. Cycles using these fluids will be optimized to
deliver the highest work output and the highest efficiency along the saturated
vapor line. The effects of turbine inlet temperature (TIT) on these fluids in the
superheated region will be investigated at 2 pressure levels as compared to the
optimized cycle. By increasing the TIT along the isobaric line, the working fluid
will be superheated. Table 1 presents the thermophysical properties of R123 and
Table 1: Thermophysical properties of R123 and Isobutane [13]
Parameters R123 Isobutane
Chemical Formula CHCl2 – CF3 C4H10
Molecular weight (g/mol) 152.93 58.125
Slope of saturated vapor line Isentropic Negative
Critical temperature (K) 456.831 407.85
Critical Pressure (MPa) 3.6618 3.64
Boiling point at 1 atm (K) 300.82 261.44
Maximum Pressure (MPa) NA 35
Maximum Temperature (K) NA 600
The performance of R123 and isobutane as the working fluid for an ORC is
analyzed. Computer programming using MATLAB is used to calculate and obtain
the relevant thermodynamic data and various system performances. The effects of
turbine inlet pressure (TIP) along saturated vapor line, the TIT in superheated
region and the T-s diagram of ORC are discussed. Figure 2 depicts the graphical
representation of R123 and isobutane in a T-s diagram. Unlike water, which has a
negative saturated vapor line gradient, R123 and isobutane has a near-straight and
positive gradient respectively. The gradient of the saturated vapor line will affect
the system efficiency [14]. When the two fluids are compared, R123 has a much
Jurnal Mekanikal, December 2005
Entropy [kJ/kg K]
Temperature [C]
smaller enthalpy of vaporization but a higher critical point. A smaller enthalpy of
vaporization means that less heat energy needed in vaporizing the fluid.
Figure 2: T-s diagram of R123 and Isobutane
3.1 Effect of Turbine Inlet Pressure along Saturated Vapor Line
The effect of TIP on the efficiency of the R123 and isobutane as the working fluid
is shown in Figure 3. From the figure, it is shown that the efficiency for both
fluids is a quadratic function of pressure. Relationship of work to pressure in the
same graph also shows a quadratic line. Work and efficiency converted from ORC
is a function of higher pressure for both fluids. Pressure point optimized work
converted is near to the pressure point optimized at the maximum obtainable
efficiency. As the pressure increases after the maximum point, less work is
produced because the fluid will move further into the superheated region at the
turbine outlet. This loss of work is due to the gradient of the saturated vapor line.
More heat is rejected to the environment as the result of the gradient of the line. In
power generation work output has priority over system efficiency if the difference
in efficiency is not significant between the two maximum points. Referring to
Table 2, the difference of efficiency obtained from optimized (Opt.) work cycle
and optimized efficiency cycle for both fluids is only 0.3% although work output
difference is about 0.4 to 2 kJ/kg.
A comparison between the two working fluids indicates that though R123
provides better overall thermal efficiency, isobutane gives better work output
albeit at a lower efficiency. The difference between the maximum work outputs
achieved by both working fluids is approximately 30 kJ/kg whereas the efficiency
difference is 6%, as shown in Table 2. The condenser temperature or the minimum
cycle temperature for R123 and isobutane is 28˚C. The common value for
condenser temperatures is 24˚C, but the saturation pressure for R123 at 28˚C is
equal to the atmospheric pressure. So, by fixing the temperature at 28°C, a
vacuum condition is not needed in the condenser.
Jurnal Mekanikal, December 2005
Figure 3: Work & efficiency vs. Turbine inlet pressure for R123 and Isobutane
The expansion ratio of R123 is nearly three times that of isobutene. The low
volume flow ratio of isobutane is due to its lower molecular weight. The Carnot
efficiency is evaluated at the same maximum and minimum working temperatures,
the difference between the actual cycle efficiency and the Carnot efficiency is only
from 6 to 8%. While, the difference in efficiency between a Rankine Cycle and a
Carnot Cycle is normally in the range of 10 to 20%, at the same working pressure
Table 2: Working fluid and conversion cycle characteristics for ORC System
Working Fluid R123 Isobutane
Condition Opt. Work
Efficiency Opt. Work Opt. Efficiency
Min. cycle pres. [MPa] 0.10 0.10 0.38 0.38
Min. cycle temp. [˚C] 28 28 28 28
Max. cycle pres. [MPa] 3.40 3.54 3.16 3.40
Max. cycle temp. [˚C] 180 182 127 132
Compression ratio 34 35.4 8.32 8.95
Turbine expansion ratio 50.6 60.2 12.5 17.6
Isentropic work [kJ/kg] 58.99 58.54 77.65 75.78
Wettest vapor quality 0.84 0.78 0.95 0.86
Exhaust vapor quality Superheated 0.98 Superheated Superheated
Turbine mass flow [kg/s] 1 1 1 1
Cycle Efficiency [%] 25.63 25.90 18.57 18.85
Carnot Efficiency [%] 33.82 33.55 24.74 25.62
From Table 2, the term of “wettest vapor quality” is used. This term is to
indicate the highest moisture content in the working section of the ORC turbine.
When higher-pressure level of ORC is tracked along the saturated vapor line, it is
0 0.5 1 1.5 4
Pressure [MPa]
Work [kJ/kg]
Efficiency [-]
22.5 33.5
Poly. (Efficiency
Poly. (Work (Isobutane))
Jurnal Mekanikal, December 2005
found that as the pressure approaches the critical pressure, fluid expansion in the
turbine will lead to higher moisture content as compared to the turbine outlet. This
occurs due to the saturated vapor line curvature in the T-s diagram of the fluid, at
higher pressures the gradient of the saturated vapor line changes from positive to
To make sure that the vapor is dry in the turbine, because high moisture content
will corrode the turbine, it is recommended that the TIP be set at the turning point
of the saturated vapor line in the T-s diagram. The turning point is situated
between the point of inflexion and the critical point. By changing the maximum
cycle pressure, the efficiency and work output will drop to a lower value but the
working fluid will be dry in the working section of the turbine. Table 3 shows the
work delivered after correcting the pressure and temperature to the turning point.
The choice of either choosing the maximum work, maximum efficiency or the
corrected pressure will depend on economic factors. Others include the effect of
wet vapor on the turbine blade, lifetimes of the turbine, cost of the turbine and
materials involved. However, these economic considerations are beyond the scope
of this study.
Table 3: Working fluid and conversion cycle characteristics at corrected pressure
3.2 Effect of Turbine Inlet Temperature in Superheated Region
The effect of superheating the working fluid is shown in Figure 4 for R123 and
isobutane. For R123, efficiency is constant with the increase of turbine inlet
temperature especially at higher pressures. Generally the efficiency declines with
temperature increase although there is a slight efficiency increase at lower
pressure. Therefore it is not attractive to increase the TIT to the superheated region
for R123 because the increase in temperature does not increase the efficiency.
With these two pressure levels plotted, performance at other pressure levels can be
found using interpolation or extrapolation method.
Working Fluid R123 Isobutane
Condition Corrected Pressure Corrected Pressure
Min. cycle pres. [MPa] 0.10 0.38
Min. cycle temp. [˚C] 28 28
Max. cycle pres. [MPa] 2.08 2.25
Max. cycle temp. [˚C] 150 107
Compression ratio 20.8 5.9
Turbine expansion ratio 71.2 7.0
Isentropic work [kJ/kg] 51.6 69.2
Exhaust vapor quality Superheated Superheated
Cycle Efficiency [%] 22.15 16.6
Carnot Efficiency [%] 28.88 20.72
Jurnal Mekanikal, December 2005
Isobutane ORC behaves quite similar to the R123 but the increase in efficiency
is steeper with temperature increase at both pressures. After the maximum point,
the drop of efficiency of the ORC is also steeper compared to R123. The increase
of efficiency with temperature is as high as 2%. Therefore, for the isobutane ORC
it is recommended to superheat within an allowable temperature limit at turbine
inlet. The optimum temperature is around 150°C to 170°C depending on the inlet
3.3 Temperature-Entropy Diagram of Organic Rankine Cycle
Figures 5 and 6 show the T-s diagram for R123 and isobutane corresponding to
the maximum work output cycle found in section 3.1. Superheating at 2 pressure
levels as shown in section 3.2, for each working fluid was plotted in the same
figures. From the T-s diagram, it is noticed that superheating ORC increases heat
rejection and will results in lower efficiencies. Though superheating increases the
efficiency for some fluids, example isobutane, but it will increase heat rejection.
Therefore, superheating will only be attractive if improvements are made to re-use
this heat rejection.
70 120 170 220 270 320
Turbine Inlet Temperature [C]
Efficiency [-]
2 MPa (Isobutane)
1.2 MPa (Isobutane)
1 MPa (R123)
Linear (2 MPa (R123))
Figure 4: The effect of turbine inlet temperature on efficiency at superheated region
for R123 and Isobutane
Jurnal Mekanikal, December 2005
3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Entropy [kJ/kg K]
Temperature [C]
P = 3.16 MPa (Opt Work)
P = 2 MPa
P = 1.2 MPa
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
Entropy [kJ/kg K]
Temperature [C]
P = 3.40 MPa (Opt.
P = 1 MPa
P = 2 MPa
Figure 5: T-s diagram of ORC Isobutane at maximum work, P = 1.2 MPa & \ P =
2 MPa
Figure 6: T-s diagram of ORC R123 at maximum work, P = 1 MPa & P = 2 MPa
In this study R123 and isobutane based ORC were examined for power
generation. Work output and efficiency of the system along the saturated vapor
Jurnal Mekanikal, December 2005
line and superheating are investigated. Based on the analysis done, the following
conclusions can be made:
1. R123 gives a higher thermal efficiency compared to isobutane, R123
efficiency ranges from 22 to 26% while isobutane ranges from 17 to 19%.
2. R123 is more suitable for higher temperature applications, while isobutane
is preferable for lower temperature applications.
3. The ORC efficiency is closer to the Carnot efficiency with the difference
being less than 10%.
4. The ORC efficiency for R123 is a weak function of turbine inlet
temperature; as a result, superheating is undesirable.
5. Superheating isobutane for the ORC can increase the efficiency but there
is an optimal temperature, from 150°C to 170°C.
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Fluids on Organic Rankine Cycle for Waste Heat Recovery, 29:1207-
... This superheat allows for a greater specific work output per pound of circulating working fluid. Cong et al. present a trade study of isobutane ORC working fluid specific work (kJ/kg) and efficiency (%) as a function of pressure (MPa) ranging from 0 to 4 MPa [35]. The work shows that as the pressure increases so does the specific work and the efficiency. ...
... Herein, analysis of the Rankine cycle with irreversibilities shows the following: For comparison, the above study shows for an isobutane ORC operating at 72.5 psi (500 kPa), i.e., the conditions of our proposed system; the specific work is on the order of 6.44 BTU/lb (15 kJ/kg), while the efficiency is on the order of 4.3%. Thus, our results are seen to be in quantitative agreement with the findings of [35]. ...
... The facility of Refs. [21,35] was able to draw approximately 250 CFM of moist air from 300 wet tons of compost divided into eight bays to allow for rotation. The heat transferred to a water tank from this air flow experienced a peak heat production rate of 31,221 Btu/h or 104 Btu/h-wet ton [36]. ...
This paper presents a feasibility study of a hybrid compost waste heat to power/ Concentrating Solar Panel (CSP) green energy Organic Rankine Cycle (ORC). The power plant is baselined to operate with a duty of 24/7 on compost waste heat and utilize solar thermal energy to boost power output during the day. This paper discusses the design of the power plant, the design of a compost driven heat exchanger/boiler, compost pile thermal analysis, CSP analysis, and simulated power plant output analysis The selection of isobutane as ORC working fluid is justified herein. A Levelized Cost of Energy (LCOE) analysis was performed to ensure that the energy produced by this hybrid power plant would come at a reasonable and competitive cost. The results herein show that the hybrid power plant affords an LCOE of 4 C/kWh for compost operation alone and an LCOE of 10.7 C/kWh for compost and CSP solar energy operation. The hybrid compost/ORC power plant presented herein affords an average energy conversion efficiency of 4.3%. Centric to the operation of the compost waste heat to power plant presented herein is the correct design and selection of the heat exchanger which interfaces the compost waste heat stream to the isobutane ORC. The design and analysis of this heat exchanger as well as commercially off the shelf hardware to meet the specifications is given in detail herein.
... On the other hand, when a low temperature heat source such as the sun are to be used to heat the working fluid, alternative working fluids have to be chosen to effectively capture the low-grade heat. The use of an organic fluid -a high molecular mass fluid with a low boiling point-allows Rankine cycle heat recovery from lower temperature sources and facilitates effective transformation of low temperature heat into useful electrical energy [2] [3] [4] [5] [6]. A distinct advantage of using organic fluids in a Solar Rankine cycle arises from the nature of their T-S curve. ...
... A significant drawback of small scale Solar Organic Rankine systems is its low efficiency, which typically ranges between 10-15% [7]. Efficiency improvements in Rankine cycles are traditionally brought about through the use of reheating and regeneration [5] [6] [7] [8]. The use of Regeneration and reheating results in the addition of heat at elevated temperatures, thereby improving efficiency. ...
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Solar power generation has emerged as one of the most rapidly growing sources of renewable energy. The solar thermal system with a Rankine cycle used to harness solar energy and generate electricity from a low temperature heat source is an emerging technology. The major drawback of solar thermal power generation is its poor efficiency, which is around 10% to 15%. Although prior attempts to improve the efficiency of the solar thermal system and use of Nano fluids in heat transfer applications have been carried out, very little work has been carried out using Nano fluids in Rankine cycle systems. Thus, the objective of the research undertaken was to primarily improve the efficiency of a small-scale solar thermal system by selecting working fluids, optimizing the system parameters and using Nano fluids with improved heat transfer properties for capturing heat. Thermodynamic simulation tool Aspen Hysys was used to carry out simulations of the Rankine and Regenerative Rankine systems. The system was simulated with combinations of Dowtherm-Cu O/Ag/Al2O3/TiO2 as the heat transfer fluid, and n-butane, n-pentane, n-hexane, or R-134a as the working fluid. System parameters such as mass flow, temperature, and pressure were optimized to obtain maximum power output and efficiency, keeping the system constraints and practicality in mind. The use of Nano fluids improved heat transfer to the working fluid in the heat exchanger by a maximum of 50%. The efficiency of the basic Rankine cycle was determined 16.03% for n-pentane, 14.90% for n-hexane, 13.83% for n-butane, and 9.82% for R-134a as the working fluid. Further, the use of regeneration improved the efficiency of the system by 6%, 3 %, 7% and 2% respectively. Highest efficiency of 27.96% was obtained when 6% volume concentration of Al2O3 was used in the heat transfer fluid, and n-pentane was used as the working fluid in the Regenerative Rankine cycle.
... So, refrigerants altered from the chlorofluorocarbons (CFC) or hydrofluorocarbons (HFC) refrigerant are usually adopted. Cong [1] used R123 and isobutene for the ORC. The optimum turbine inlet pressure and temperature in the cycle was studied when the solar energy was applied as heat source. ...
... The pressure after pumping should be equal to the pressure at the turbine inlet. (8) The system efficiency can be determined from the input power including the pump power and the output power of the turbine 1 6 ...
... Cong et-al. [97] inspected the performance of R123 and isobutene for solar thermal applications and obtained higher efficiency for R123. According to Pedro et al. [98], using dry fluids, R-123, R-113, isobutane, and R245Ca, a regenerative ORC achieves better thermal performance [99]. ...
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The Organic Rankine Cycle (ORC), Supercritical Rankine Cycle (SRC), and Supercritical Brayton Cycle (SBC) are three power cycles that are systematically investigated in the present paper, with particular emphasis on the different types of working fluids that are employed in each cycle and their influence as well as potential opportunities for enhancing the efficiency and thermal performance of power generation systems. The Organic fluids, the refrigerants, and the gasses are all taken into consideration as prospective working fluids in the study. The results demonstrate the distinct advantages and disadvantages of each cycle, with the ORC being best suited for low-temperature recuperation of waste heat, the SRC for operations requiring medium temperatures, and the SBC for high-temperature energy production. This research provides valuable insights regarding the selection of working fluids, considering various factors such as system parameters, environmental impacts, and thermodynamic efficiency. This study also discusses the recent findings on the utilization of organic working fluids, zeotropic mixtures, and nanofluids in these cycles, as well as provides a detailed summary of current trends and developments made in the field. Optimization of different working variables and the utilization of certain changes of working fluids for improving cycle efficiency is also reviewed. This study is motivated by the ongoing energy crisis and the necessity for alternate energy sources, particularly for the transformation of low-quality heat sources. Finally, the potential impact of this research on the scientific community lies in its ability to assist researchers and engineers in making well-informed decisions regarding the selection of the optimal operational fluid for a specific power cycle. Furthermore, this connection between power industries and working fluid selection highlights the relevance of this study to practical applications within the field.
... Operating condition Temperature of condenser Tc=293K and Condenser outlet weight P3=2.5Mpa among the fluid inspected, benzene was to give most raised most astounding productivity pursued successively by R113, R11, R12, R134a and ammonia. Sanjayan Velautham et al [2] examine the practicality of an ORC driven by Solar thermal energy as a sustainable power source choice for little and medium measured business utilization, power generation under 10MW. The solar thermal cycle circulates heat move liquid in the cycle and bridle thermal energy from the sun and exchange it to the natural compound in the ORC by means of a heat exchanger R123 and iso-butane are chosen as working liquid ,among R123 gives a higher warm proficiency contrasted with iso-butane, R123 productivity ranges from 22 to 26% while iso-butane ranges from 17 to 19%. ...
Full-text available
The increasing energy need due to industrial expansion and population size led the human race for usage of major conventional energy sources like oil, coal, gas. But these resources trouble the environment leading to potential problems like pollution, global warming etc. Thus, in order to overcome the burning issues, many alternative energy sources are developed such as wind, hydro, solar, tidal, geothermal, biofuel, nuclear etc. are used for power generation. Among these the solar energy is plentifully available resource and can be employed to organic rankine cycle technology for power generation. The main aim of this research work is to develop a novel power generating system by using alternative energy resource i.e. solar energy. The work focussed on simulating the power generation of producing unit by employing solar organic rankine cycle and working fluids R-245fa, R-227ea & R-245fa/ R-227ea mixture. The Organic Rankine cycle efficiency mainly depend on the Selection of working liquid, working condition has extraordinary impact, and its vitality proficiency and effect on nature. The performance parameters like Solar Organic Efficiency, Solar Collector Area, second law efficiency, Turbine volume expansion ratio etc. are studied. It is noticed that organic efficiency of refrigerant mixture R245fa/R227ea is 4% more compared to pure fluid R227ea at turbine outlet temperature of 353K.The Volume expansion ratio of the turbine comparing to refrigerant mixture is reduced by 25.4% & 30% compared to pure refrigerant R227ea and R245fa.
... Roy et al. [24] conducted studied on parametric optimization and performance analysis of a waste heat recovery system based on ORC using R-12, R-123 and R-134a as the working fluids for power generation, and the results show that the ORC system using R-123 had the maximum work output and highest efficiency. Cong et al. [25] examine on ORC by using fluids R123 and isobutene for analysed and they concluded that R123 have a higher thermal efficiency compared to isobutene. Tchanche et al. [26] investigate on 20 of fluids selection for ORC and R134a appears as the most suitable for small scale ORC in solar applications while R152a, R600a, R600 and R290 show and offer attractive performance but they need more safety precautions due to their flammability. ...
... The solar energy is collected using photovoltaic solar collector operating at a temperature ranging from 80°C -180°C. To calculate the absorber surface temperature for the collector, T ab , the following formula was applied [27]. ...
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The utilization of solar energy is on a rise due to serious global energy crisis.This paper presents the simulation generated data in energy and exergy analysis to determine the performances for an organic Rankine cycle (ORC). The system was simulated to supply both electrical and thermal energy to an existing residential apartment. The simulation of the operating ORC was performed using Therminol 55 as the heat transmitting fluid within the oil tank, pump and evaporator and using R-245fa as the working fluid within the cycle. The highest power output was obtained when the expander inlet pressure was 2MPa and the solar source temperature was 163.5°C, delivering an output power of 33.34kW with an achievement of overall process efficiency of 14.55%. The proposed system is intended to be potentially attractive for real estate investors in Thika town with good solar irradiation and without (or with very high cost) access to the general public electricity supply. Detailed analysis of energy and exergy in the organic Rankine cycle has been done in order to determine the best rational use of energy and suggestions on exergy saving are provided based on simulated results.
The aim of reducing exploitation of the earth leads to the development of Renewable Energy Sources (RES). A technology that achieves this purpose using the solar energy is the Compound Solar Concentrator, able to increase the conveyance of the sun’s rays onto the solar cells. In this work this technology is equipped with a Coil Cooling System, to cool the system by improving the conversion efficiency. The heat absorbed by the cooling water represents usable energy in an Organic Rankine Cycle (ORC) system. The first part of the work is based on transient numerical simulations of the cooled Compound Parabolic Concentrator (CPC) with COMSOL Multiphysics (CM) software. The performance parameters show that after about n.20 models the improvements are contained reaching a thermal equilibrium. The selected number of cooled CPCs is n.20, reaching a temperature of the outlet water from coils of 50 °C and a flow rate composed of n.2 coils of 1.2 l/min. Exploiting this outlet water, an ORC technology is coupled from a simulation point of view with the cooled CPC, making it possible to obtain an electric and thermal efficiency of 11.73% and 60.30% respectively with a pump pressure of 20 bar.
Concentrating solar power (CSP) is a mainstream of solar energy utilization, and thermionic emission is a potential way to convert concentrated solar radiation into power with a theoretical efficiency of 50-70%, surpassing both Shockley-Queisser limit and photo-thermal limit. This literature attempts to provide a comprehensive understanding of and an insight into solar thermionic energy conversion. The fundamentals of electron emission from electrodes and electron transport in vacuum gap are presented, as well as the state of the art of solar thermionic energy conversion technologies, including heat-induced thermionics and photon-enhanced thermionics. The former is driven by thermal energy, whereas the latter takes advantage of both quantum photon energy and thermal energy. Burgeoning research indicates that photon-enhanced thermionic conversion is a promising technology for concentrating solar power due to the high efficiency and simple operating mode. Now, it is important to develop novel materials and coating technologies to facilitate electron emission and reduce space charge effect in interelectrode vacuum. Structural design of thermionic converters and top-bottom configuration of solar-electricity systems are suggested for practical applications.
The organic Rankine cycle has been widely used to convert the renewable energy such as the solar energy, the geothermal energy, or the waste energy etc., to the electric power. Some previous studies focused to find what kind of refrigerant would be a best working fluid for the organic Rankine cycle. In this study, R245fa was chosen to the working fluid, and the cycle analysis was conducted for the output power of 30kW or less. In addition, properties (temperature, pressure, entropy, and enthalpy etc.) of the working fluid on the cycle were predicted when the turbine output power was controlled by adjusting the mass flowrate. The configuration of the turbine was a radial-type and the supersonic nozzles were applied as the stator. So, the turbine was operated in partial admission. The turbine efficiency and the optimum velocity ratio were considered in the cycle analysis for the low partial admission rate. The computed results show that the system efficiency is affected by the partial admission rate more than the temperature of the evaporator.
Library of Congress Cataloging-in-Publication Data Patel, Mukind R., 1942. Wind and solar power systems / Mukund R. Patel. p. cm. Includes bibliographical references and index. ISBN 0-8493-1605-7 (alk. paper) 1. Wind power plants. 2. Solar power plants. 3. Photovoltaic power systems. I. Title. TK1541.P38 1999 621.31 ′ 2136—dc21 98-47934 CIP This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior permission in writing from the publisher.
The efficiencies of ORCs using cryogens such as benzene, ammonia, R11, R12, R134a and R113 as working fluids have been analyzed parametrically and compared. For operation between two isobaric curves, the system efficiency increases and decreases for wet and dry fluids, respectively, and the isentropic fluid achieves an approximately constant value for high turbineinlet temperatures. These effects are primarily due to the different slopes and shapes of the saturation vapor curves of the fluids. Isentropic fluids are most suitable for recovering low-temperature waste heat. Freons and their alternatives have been studied and shown similar system responses in ORCs.
A modified Benedict–Webb–Rubin (MBWR) equation of state has been developed for Refrigerant 123 (2,2-dichloro-1,1,1-trifluoroethane) based on recently measured thermodynamic property data and data available from the literature. Single-phase pressure-volume-temperature (PVT), heat capacity, and sound speed data, as well as second virial, vapor pressure, and saturated liquid and saturated vapor density data, were used with multiproperty linear least squares fitting techniques to fit the 32 adjustable coefficients of the MBWR equation. Coefficients for the equation of state and for ancillary equations representing the vapor pressure saturated liquid and saturated vapor densities, and ideal gas heat capacity are given. While the measurements cover differing ranges of temperature and pressure, the MBWR formulation is applicable along the saturation line and in the liquid, vapor, and supercritical regions at temperatures from 166 to 500 K with pressures to 40 MPa and densities to 11.6 mol/L (1774 kg/m3). This formulation has been selected as an international standard based on an evaluation of the available equations of state by a group working under the auspices of the International Energy Agency.
This study presents an analysis of the performance of organic Rankine cycle (ORC) subjected to the influence of working fluids. The effects of various working fluids on the thermal efficiency and on the total heat-recovery efficiency have been investigated. It is found that the presence of hydrogen bond in certain molecules such as water, ammonia, and ethanol may result in wet fluid conditions due to larger vaporizing enthalpy, and is regarded as inappropriate for ORC systems. The calculated results reveal that the thermal efficiency for various working fluids is a weak function of the critical temperature. The maximum value of the total heat-recovery efficiency occurs at the appropriate evaporating temperature between the inlet temperature of waste heat and the condensing temperature. In addition, the maximum value of total heat-recovery efficiency increases with the increase of the inlet temperature of the waste heat source and decreases it by using working fluids having lower critical temperature. Analytical results using a constant waste heat temperature or based on thermal efficiency may result in considerable deviation of system design relative to the varying temperature conditions of the actual waste heat recovery and is regarded as inappropriate.
We propose a new type of environmentally friendly system called the “Organic Rankine Cycle” (ORC) in which low-grade heat sources are utilized. This system combines a circulated thermosyphon with a turbine system. The working fluid used in this study is an organic substance which has a low boiling point and a low latent heat for using low-grade heat sources. A numerical simulation model of the ORC is made in order to estimate its optimum operating conditions. An experimental apparatus is also made in this study. From the numerical simulation, it is suggested that HCFC-123 gives higher turbine power than water which is a conventional working fluid, and operating conditions where saturated vapor at the turbine inlet would give the best performance. From the experimental results, HCFC-123 improves the cycle performance drastically. In addition, the turbine made for trial use in this study gives good performance.
In the conversion of low temperature heat into electricity the greatest efficiency is obtained in many cases by using an organic Rankine cycle (ORC). The ORC-process may be feasible also in high temperature applications, if the output is small. This paper deals with an ORC-design, in which a high-speed oil free turbogenerator-feed pump is used. The use of high-speed turbogenerator makes the ORC small, simple, hermetic and reduces significantly the maintenance expenses.
Government of Malaysia
  • Eighth Malaysia
Eighth Malaysia Plan. Government of Malaysia. K.L. 2000
  • B A Younglove
  • J F Ely
Younglove, B.A. and Ely, J.F., (1987), J. Phys. Chem. Ref. Data: Thermodynamical Properties of Fluids. II. Methane, Ethane, Propane, Isobutane, and Normal Butane, 16(4):577-797.