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Dr. Dimitris Manolakos
Department of Natural Resources Management & Agricultural Engineering, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece

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Research Keywords & Expertise

0 Trilateral Flash Cycle
0 Low temperature heat to power conversion with ORC
0 Solar sub-critical ORC prototypes (power generation and desalination) design, manufacturing and testing
0 Volumetric expanders and heat exchangers design, manufacturing and testing
0 Super-critical, TransCritical prototypes design manufacturing and testing

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Low temperature heat to power conversion with ORC

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Journal article
Published: 28 July 2021 in Renewable Energy
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The operation of an integrated CPVT/ORC unit is investigated to identify the possibility of combining efficiently an ORC engine with a CPVT collectors’ field. The combined system is designed to operate so that the heat provided by the CPV field is at a temperature level in the range of 70–90 °C. The performance of the ORC engine is assessed towards comprehending its behavior under varying thermal loads and, as a result, maximizing the overall system electricity production. The analysis reveals that the electricity production from the ORC engine may be in the order of approximately 17 % of the total output of the combined system and that the implementation of the examined technological solution could increase the solar energy conversion efficiency of the CPV field, provided that the ORC engine operates at its maximum thermal efficiency. Finally, the preliminary economic analysis highlighted the potential of the integrated unit, which could be competitive even for small-scale systems.

ACS Style

Chrysanthos Golonis; Anastasios Skiadopoulos; Dimitris Manolakos; George Kosmadakis. Assessment of the performance of a low-temperature Organic Rankine Cycle engine coupled with a concentrating PV-Thermal system. Renewable Energy 2021, 179, 1085 -1097.

AMA Style

Chrysanthos Golonis, Anastasios Skiadopoulos, Dimitris Manolakos, George Kosmadakis. Assessment of the performance of a low-temperature Organic Rankine Cycle engine coupled with a concentrating PV-Thermal system. Renewable Energy. 2021; 179 ():1085-1097.

Chicago/Turabian Style

Chrysanthos Golonis; Anastasios Skiadopoulos; Dimitris Manolakos; George Kosmadakis. 2021. "Assessment of the performance of a low-temperature Organic Rankine Cycle engine coupled with a concentrating PV-Thermal system." Renewable Energy 179, no. : 1085-1097.

Journal article
Published: 15 December 2020 in Sustainability
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Low-enthalpy geothermal resources (e) ORC engine manufactured to operate at temperatures up to 140 °C are used to add reliability in the calculations. In order to meet the needs of the people, four different APMs based on PVs, wind turbines, and geothermal ORC of different but appropriate configurations were designed and sized through optimization. The optimization process was based on particle swarm optimization (PSO). The comparative examination of the results shows that the use of a low-power, low-temperature ORC engine in an APM is technically feasible; more cost effective than the configurations based on PVs, wind turbines, or combination of both; and has increased environmental sustainability.

ACS Style

George Kyriakarakos; Erika Ntavou; Dimitris Manolakos. Investigation of the Use of Low Temperature Geothermal Organic Rankine Cycle Engine in an Autonomous Polygeneration Microgrid. Sustainability 2020, 12, 10475 .

AMA Style

George Kyriakarakos, Erika Ntavou, Dimitris Manolakos. Investigation of the Use of Low Temperature Geothermal Organic Rankine Cycle Engine in an Autonomous Polygeneration Microgrid. Sustainability. 2020; 12 (24):10475.

Chicago/Turabian Style

George Kyriakarakos; Erika Ntavou; Dimitris Manolakos. 2020. "Investigation of the Use of Low Temperature Geothermal Organic Rankine Cycle Engine in an Autonomous Polygeneration Microgrid." Sustainability 12, no. 24: 10475.

Journal article
Published: 13 September 2019 in Applied Thermal Engineering
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The current paper investigates the performance behavior of an ORC unit in which the expansion process is realized by two in series scroll expanders. The heating load varies from 50 to 120 kWth and the heat supply temperature to the employed organic fluid (R245fa) from 80 to 130 °C. The two expanders in series configuration is chosen so that to achieve operation as close as possible to the nominal pressure ratio of each scroll machine at high evaporation temperatures where a total pressure ratio in the order of 10 is met. An extensive discussion and analysis is provided on how the key variables, such as pressure ratio, intermediate pressure and filling factor, interact between the two expanders and how this interaction affects each expander separately. This analysis leads to better understanding the overall performance in terms of isentropic and thermal efficiency and power generation. Emphasis is paid in off-design performance comprehension, while useful conclusions on how such split expansion process can be efficiently controlled by speed regulation are extracted. Focus is given on the interpretation of results for the partial heat load of 50 kWth at 130 °C, which show a very large scattering of both isentropic efficiencies of expanders and thermal efficiency. Accordingly, a variation of thermal efficiency is detected from slightly above 3% to about 10%. The results show that there are certain operating conditions where system performance is ameliorated and the maximum thermal efficiency of almost 10% is achieved, while the isentropic efficiency of high pressure expander reaches a maximum of 68% and that of low pressure expander 57%.

ACS Style

Dimitris Manolakos; George Kosmadakis; Erika Ntavou; Bertrand Tchanche. Test results for characterizing two in-series scroll expanders within a low-temperature ORC unit under partial heat load. Applied Thermal Engineering 2019, 163, 114389 .

AMA Style

Dimitris Manolakos, George Kosmadakis, Erika Ntavou, Bertrand Tchanche. Test results for characterizing two in-series scroll expanders within a low-temperature ORC unit under partial heat load. Applied Thermal Engineering. 2019; 163 ():114389.

Chicago/Turabian Style

Dimitris Manolakos; George Kosmadakis; Erika Ntavou; Bertrand Tchanche. 2019. "Test results for characterizing two in-series scroll expanders within a low-temperature ORC unit under partial heat load." Applied Thermal Engineering 163, no. : 114389.

Journal article
Published: 01 July 2019 in Computers and Electronics in Agriculture
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Environment control in broiler houses aims at achieving optimal growth rate and welfare conditions through ventilation, heating and cooling and is currently realized by using conventional techniques such as Liquefied Petroleum Gas (LPG) heaters, fans and evaporative panels. These systems use electricity or fossil fuels as energy sources and they are neither efficient nor renewable, thus further contribute on the increase of Greenhouse Gases (GHG) from livestock operations. They are technologies not always capable to establish optimal comfort conditions, in terms of indoor temperature and relative humidity, within the broiler house. Heat pump, on the other hand, is fully aligned with EU directive for energy efficiency and nearly Zero Energy Buildings (nZEBs) as a Renewable Energy Source (RES). The application of heat pumps as heating technology in Heating, Ventilation and Air Conditioning (HVAC) systems are capable for precise control the environment of broiler houses assuring comfortable conditions that maximize animals’ welfare and productivity. This study presents a time series model to simulate in hourly step the behavior of a broiler house equipped with HVAC system with heat pump that finally concludes to the calculation of the basic design parameters of the system. The model was developed in Engineering Equation Solver (EES) model and applied for a 10,000 broilers’ house at the area of Kavala in Northern Greece. Maximum grand total cooling and heating loads were estimated at 390 kW and 47 kW, respectively. The size of cooling unit should be 8 times larger than that for heating, pointing-out the major problem of high temperatures in Southeast Mediterranean. In terms of heat consumption, a year-round simulation of the broiler house reveals that sensible cooling loads account for 189 MWh while heating for 24 MWh. Sensible cooling is mostly accompanied with dehumidification and reheating, an expected finding for such dense population buildings. The model results for heating were very similar with those available from energy audits, but unfortunately no cooling data were found for comparison.

ACS Style

Dimitris Manolakos; Panagiotis Panagakis; Thomas Bartzanas; Konstantinos Bouzianas. Use of heat pumps in HVAC systems for precise environment control in broiler houses: System’s modeling and calculation of the basic design parameters. Computers and Electronics in Agriculture 2019, 163, 104876 .

AMA Style

Dimitris Manolakos, Panagiotis Panagakis, Thomas Bartzanas, Konstantinos Bouzianas. Use of heat pumps in HVAC systems for precise environment control in broiler houses: System’s modeling and calculation of the basic design parameters. Computers and Electronics in Agriculture. 2019; 163 ():104876.

Chicago/Turabian Style

Dimitris Manolakos; Panagiotis Panagakis; Thomas Bartzanas; Konstantinos Bouzianas. 2019. "Use of heat pumps in HVAC systems for precise environment control in broiler houses: System’s modeling and calculation of the basic design parameters." Computers and Electronics in Agriculture 163, no. : 104876.

Review
Published: 25 June 2019 in Applied Sciences
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Supercritical operation is considered a main technique to achieve higher cycle efficiency in various thermodynamic systems. The present paper is a review of experimental investigations on supercritical operation considering both heat-to-upgraded heat and heat-to-power systems. Experimental works are reported and subsequently analyzed. Main findings can be summarized as: steam Rankine cycles does not show much studies in the literature, transcritical organic Rankine cycles are intensely investigated and few plants are already online, carbon dioxide is considered as a promising fluid for closed Brayton and Rankine cycles but its unique properties call for a new thinking in designing cycle components. Transcritical heat pumps are extensively used in domestic and industrial applications, but supercritical heat pumps with a working fluid other than CO2 are scarce. To increase the adoption rate of supercritical thermodynamic systems further research is needed on the heat transfer behavior and the optimal design of compressors and expanders with special attention to the mechanical integrity.

ACS Style

Steven Lecompte; Erika Ntavou; Bertrand Tchanche; George Kosmadakis; Aditya Pillai; Dimitris Manolakos; Michel De Paepe. Review of Experimental Research on Supercritical and Transcritical Thermodynamic Cycles Designed for Heat Recovery Application. Applied Sciences 2019, 9, 2571 .

AMA Style

Steven Lecompte, Erika Ntavou, Bertrand Tchanche, George Kosmadakis, Aditya Pillai, Dimitris Manolakos, Michel De Paepe. Review of Experimental Research on Supercritical and Transcritical Thermodynamic Cycles Designed for Heat Recovery Application. Applied Sciences. 2019; 9 (12):2571.

Chicago/Turabian Style

Steven Lecompte; Erika Ntavou; Bertrand Tchanche; George Kosmadakis; Aditya Pillai; Dimitris Manolakos; Michel De Paepe. 2019. "Review of Experimental Research on Supercritical and Transcritical Thermodynamic Cycles Designed for Heat Recovery Application." Applied Sciences 9, no. 12: 2571.

Journal article
Published: 04 May 2017 in Energies
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In this study, the performance of a helical coil heat exchanger operating at subcritical and supercritical conditions is analysed. The counter-current heat exchanger was specially designed to operate at a maximal pressure and temperature of 42 bar and 200 °C, respectively. The small-scale solar organic Rankine cycle (ORC) installation has a net power output of 3 kWe. The first tests were done in a laboratory where an electrical heater was used instead of the concentrated photovoltaic/thermal (CPV/T) collectors. The inlet heating fluid temperature of the water was 95 °C. The effects of different parameters on the heat transfer rate in the heat exchanger were investigated. Particularly, the performance analysis was elaborated considering the changes of the mass flow rate of the working fluid (R-404A) in the range of 0.20–0.33 kg/s and the inlet pressure varying from 18 bar up to 41 bar. Hence, the variation of the heat flux was in the range of 5–9 kW/m2. The results show that the working fluid’s mass flow rate has significant influence on the heat transfer rate rather than the operational pressure. Furthermore, from the comparison between the experimental results with the heat transfer correlations from the literature, the experimental results fall within the uncertainty range for the supercritical analysis but there is a deviation of the investigated subcritical correlations.

ACS Style

Marija Lazova; Alihan Kaya; Marijn Billiet; Steven Lecompte; Dimitris Manolakos; Michel De Paepe. Experimental Assessment of a Helical Coil Heat Exchanger Operating at Subcritical and Supercritical Conditions in a Small-Scale Solar Organic Rankine Cycle. Energies 2017, 10, 619 .

AMA Style

Marija Lazova, Alihan Kaya, Marijn Billiet, Steven Lecompte, Dimitris Manolakos, Michel De Paepe. Experimental Assessment of a Helical Coil Heat Exchanger Operating at Subcritical and Supercritical Conditions in a Small-Scale Solar Organic Rankine Cycle. Energies. 2017; 10 (5):619.

Chicago/Turabian Style

Marija Lazova; Alihan Kaya; Marijn Billiet; Steven Lecompte; Dimitris Manolakos; Michel De Paepe. 2017. "Experimental Assessment of a Helical Coil Heat Exchanger Operating at Subcritical and Supercritical Conditions in a Small-Scale Solar Organic Rankine Cycle." Energies 10, no. 5: 619.

Original articles
Published: 09 August 2013 in International Journal of Sustainable Energy
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A small-scale, low-temperature solar organic Rankine cycle (ORC) is investigated, focusing on some key aspects of its design and operation, in order for the system to track the optimised point under variable weather conditions. Two major configurations can be identified for small-scale ORCs using two expansion stages, for improving the performance at variable loads. The first concerns the use of a cascade ORC and the second one of a single circuit with two in-series expanders. The first goal of this study is to theoretically investigate the performance of these two alternative configurations under variable heat inputs from evacuated tube solar collectors. The configuration finally selected is the ORC with two in-series expanders, showing higher efficiency for the entire range of incident solar radiations. This configuration is then further investigated, focusing on its operation and control, such as the by-passing of the first expander, in order to optimise its operation.

ACS Style

G. Kosmadakis; D. Manolakos; G. Papadakis. An investigation of design concepts and control strategies of a double-stage expansion solar organic Rankine cycle. International Journal of Sustainable Energy 2013, 34, 446 -467.

AMA Style

G. Kosmadakis, D. Manolakos, G. Papadakis. An investigation of design concepts and control strategies of a double-stage expansion solar organic Rankine cycle. International Journal of Sustainable Energy. 2013; 34 (7):446-467.

Chicago/Turabian Style

G. Kosmadakis; D. Manolakos; G. Papadakis. 2013. "An investigation of design concepts and control strategies of a double-stage expansion solar organic Rankine cycle." International Journal of Sustainable Energy 34, no. 7: 446-467.

Journal article
Published: 01 June 2013 in Desalination
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ACS Style

C. Li; G. Kosmadakis; Dimitris Manolakos; E. Stefanakos; G. Papadakis; D.Y. Goswami. Performance investigation of concentrating solar collectors coupled with a transcritical organic Rankine cycle for power and seawater desalination co-generation. Desalination 2013, 318, 107 -117.

AMA Style

C. Li, G. Kosmadakis, Dimitris Manolakos, E. Stefanakos, G. Papadakis, D.Y. Goswami. Performance investigation of concentrating solar collectors coupled with a transcritical organic Rankine cycle for power and seawater desalination co-generation. Desalination. 2013; 318 ():107-117.

Chicago/Turabian Style

C. Li; G. Kosmadakis; Dimitris Manolakos; E. Stefanakos; G. Papadakis; D.Y. Goswami. 2013. "Performance investigation of concentrating solar collectors coupled with a transcritical organic Rankine cycle for power and seawater desalination co-generation." Desalination 318, no. : 107-117.

Journal article
Published: 28 February 2011 in Solar Energy
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In concentrating photovoltaic (CPV) systems the incident solar radiation is multiplied by a factor equal to the concentration ratio, with the use of lenses or reflectors. This is implemented, in order to increase the electric power production, since this value has a linear dependence from the incident radiation. Therefore, the specific energy production of the cells (kWh/m 2 ) radically increases, but due to this high intensity CPVs consequently operate at elevated temperatures, because heat dissipation to the environment is not so intense and heat produced cannot naturally convected. This temperature increase not only leads to a reduction of their electric efficiency, but also it must be dissipated, since issues regarding their degradation and reduction of their lifetime might arise. There are many reported ways of removing this heat, either by adding a cooling unit on the back side of the CPV module, or by recovering with possible uses in buildings, industry, additional power production or even desalination of seawater. The current work is actually a feasibility study, concerning a concentrating photovoltaic/thermal (CPV/T) system, where the heat produced is recovered by an organic Rankine cycle (ORC) for additional power production. A pump drives the organic fluid of the cycle, which is evaporated in the tubes of the CPV/T and driven to an expander for mechanical power production. For the condensation of the organic fluid several possible alternatives can be applied. That way, the PV cells can be cooled effectively and increase their electrical efficiency, while the recovered heat is designated to produce additional electric energy through the organic Rankine process, when the expander of the Rankine engine is coupled to a generator. The scope of the present work is to investigate an alternative application of concentrating PV modules through exploiting the generated heat by the ORC process and combining both technologies into an integrated system. The design of the system is presented in details, along with an optimization of some main parameters. The performance of the system will also be examined and compared with an equivalent conventional CPV system, referring to their design points. Finally, the annual and daily performance will be studied, which is a more realistic indicator, concerning the increased efficiency this integrated system is expected to have, followed by a cost analysis, in order to examine its economic feasibility as well.

ACS Style

G. Kosmadakis; Dimitris Manolakos; George Papadakis. Simulation and economic analysis of a CPV/thermal system coupled with an organic Rankine cycle for increased power generation. Solar Energy 2011, 85, 308 -324.

AMA Style

G. Kosmadakis, Dimitris Manolakos, George Papadakis. Simulation and economic analysis of a CPV/thermal system coupled with an organic Rankine cycle for increased power generation. Solar Energy. 2011; 85 (2):308-324.

Chicago/Turabian Style

G. Kosmadakis; Dimitris Manolakos; George Papadakis. 2011. "Simulation and economic analysis of a CPV/thermal system coupled with an organic Rankine cycle for increased power generation." Solar Energy 85, no. 2: 308-324.

Journal article
Published: 28 February 2011 in Renewable Energy
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The use of efficient, innovative and cost effective renewable energy systems in order to produce potable water seems to be a very promising research objective for scientists, engineers and economists, since the choice of the appropriate technologies is combined with the fact that these systems should be economically feasible. This paper presents a general concept of designing a desalination system which uses a solar collectors’ field to drive a reverse osmosis process through an Organic Rankine Cycle. The auxiliary equipment power demand (i.e. cooling pump, collectors’ circulator and working fluid pump) is satisfied by a hybrid system based on a PV generator. An inverter is used to convert the DC to AC current while a battery array is also integrated into the system as energy storage. In order to make a complete study of the system, the pumping loads through the sea and to the area’s municipal water network have been taken into consideration. The objective of the current work is to study an autonomous desalination system that can be applied to several Greek islands where two problems are to be solved at the same time: the lack of potable water and the absence of electrical grid. The investigation of the financial conditions for the realization of a feasible project of an integrated hybrid desalination system (including Solar Thermal and PV technology) is finally presented.

ACS Style

Sotirios Karellas; Konstantinos Terzis; Dimitrios Manolakos. Investigation of an autonomous hybrid solar thermal ORC–PV RO desalination system. The Chalki island case. Renewable Energy 2011, 36, 583 -590.

AMA Style

Sotirios Karellas, Konstantinos Terzis, Dimitrios Manolakos. Investigation of an autonomous hybrid solar thermal ORC–PV RO desalination system. The Chalki island case. Renewable Energy. 2011; 36 (2):583-590.

Chicago/Turabian Style

Sotirios Karellas; Konstantinos Terzis; Dimitrios Manolakos. 2011. "Investigation of an autonomous hybrid solar thermal ORC–PV RO desalination system. The Chalki island case." Renewable Energy 36, no. 2: 583-590.

Journal article
Published: 31 May 2010 in Renewable Energy
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The present work concerns the parametric study of an autonomous, two-stage solar organic Rankine cycle for RO desalination. The main goal of the current simulation is to estimate the efficiency, as well as to calculate the annual mechanical energy available for desalination in the considered cases, in order to evaluate the influence of various parameters on the performance of the system. The parametric study concerns the variation of different parameters, without changing actually the baseline case. The effect of the collectors' slope and the total number of evacuated tube collectors used, have been extensively examined. The total cost is also taken into consideration and is calculated for the different cases examined, along with the specific fresh water cost (€/m 3 ).

ACS Style

G. Kosmadakis; D. Manolakos; G. Papadakis. Parametric theoretical study of a two-stage solar organic Rankine cycle for RO desalination. Renewable Energy 2010, 35, 989 -996.

AMA Style

G. Kosmadakis, D. Manolakos, G. Papadakis. Parametric theoretical study of a two-stage solar organic Rankine cycle for RO desalination. Renewable Energy. 2010; 35 (5):989-996.

Chicago/Turabian Style

G. Kosmadakis; D. Manolakos; G. Papadakis. 2010. "Parametric theoretical study of a two-stage solar organic Rankine cycle for RO desalination." Renewable Energy 35, no. 5: 989-996.

Journal article
Published: 01 January 2010 in Desalination
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The present work concerns the design of a two-stage Organic Rankine Cycle (ORC) for RO desalination exploiting a thermal source of steady heat flow supply. Aiming at improving the efficiency of the single stage low temperature (in the range of 70–80 °C) Organic Rankine Cycle for RO desalination, a high temperature (in the order of 130 °C) stage is added. The basic principle of operation is that the heat extracted from the condensation of the high temperature stage (e.g. upper stage), evaporates the refrigerant of the low temperature stage (e.g. lower stage), thus increasing significantly the overall efficiency. In comparison with the two-stage Solar Organic Rankine Cycle (SORC) that was developed and designed in a previous work, waste heat is considered as a steady thermal source in this study, in order to identify the desalinating limits of the proposed system. It is expected the quantity of fresh water to increase significantly with the incorporation of a constant heat flow, as well as the efficiency of the system, since it operates almost constantly at full load the whole day long. The system design was done with the aid of TRNSYS V16.0 software.

ACS Style

G. Kosmadakis; D. Manolakos; S. Kyritsis; G. Papadakis. Design of a two stage Organic Rankine Cycle system for reverse osmosis desalination supplied from a steady thermal source. Desalination 2010, 250, 323 -328.

AMA Style

G. Kosmadakis, D. Manolakos, S. Kyritsis, G. Papadakis. Design of a two stage Organic Rankine Cycle system for reverse osmosis desalination supplied from a steady thermal source. Desalination. 2010; 250 (1):323-328.

Chicago/Turabian Style

G. Kosmadakis; D. Manolakos; S. Kyritsis; G. Papadakis. 2010. "Design of a two stage Organic Rankine Cycle system for reverse osmosis desalination supplied from a steady thermal source." Desalination 250, no. 1: 323-328.

Journal article
Published: 31 July 2009 in Desalination
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A comparison of many organic working fluids was made. Emphasis was given to the efficiency of the thermodynamic cycle using each working fluid, as well as its environmental impact. The thermodynamic cycle consists of two stages: high temperature and low temperature. The maximum temperature of the first one is around 137°C and the second one 77°C. Not all the working fluids had a critical temperature higher than 137EC; therefore, not all could be used under these conditions. The study focused on 33 organic working fluids; according to various criteria that were followed, the most appropriate found was the R245fa. Although it was not the most efficient, nor produced the maximum mechanical work, it performed quite well and, in addition, its use is not restricted by any international regulations. The concept was part of the research within the framework of the project COOP-CT-2003-507997.

ACS Style

G. Kosmadakis; D. Manolakos; S. Kyritsis; G. Papadakis. Comparative thermodynamic study of refrigerants to select the best for use in the high-temperature stage of a two-stage organic Rankine cycle for RO desalination. Desalination 2009, 243, 74 -94.

AMA Style

G. Kosmadakis, D. Manolakos, S. Kyritsis, G. Papadakis. Comparative thermodynamic study of refrigerants to select the best for use in the high-temperature stage of a two-stage organic Rankine cycle for RO desalination. Desalination. 2009; 243 (1-3):74-94.

Chicago/Turabian Style

G. Kosmadakis; D. Manolakos; S. Kyritsis; G. Papadakis. 2009. "Comparative thermodynamic study of refrigerants to select the best for use in the high-temperature stage of a two-stage organic Rankine cycle for RO desalination." Desalination 243, no. 1-3: 74-94.

Journal article
Published: 30 June 2009 in Renewable Energy
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The current paper presents the economic evaluation of a two-stage Solar Organic Rankine Cycle (SORC) for using the mechanical energy produced during the thermodynamic process to drive a Reverse Osmosis (RO) desalination unit. The developed integrated system is briefly analysed and the specific fresh water cost, as well as the cost of energy is calculated. The economic assessment results are compared with those obtained from a low-temperature SORC-RO and two alternative variants of PhotoVoltaic RO (PV–RO) systems (with and without batteries). It is found that the critical fresh water cost for the system under consideration is 7.48 €/m 3 of permeate water and the cost of energy equals to 2.74 €/kWh, when the water cost is slightly higher than the critical one (meaning 8 €/m 3 ). These values are considered satisfactory enough, in comparison to the other autonomous desalination technologies. Additionally, the specific fresh water cost of the developed technology was calculated to be 6.85 €/m 3 , being very close to the values of the PV–RO systems. The variant of two-stage SORC significantly improves the efficiency and reduces the cost of the already developed prototype system (single-stage low-temperature SORC for RO desalination), because the specific cost is found to be much lower and taking into consideration its reliability, this technology can constitute an alternative desalination method competitive to the PV–RO on the basis of techno-economic feasibility. Keywords Solar organic Rankine cycle Economic assessment RO desalination Specific cost Nomenclature AEC the annual equivalent cost (€) B t = j the benefit of the investment in each year, including the damping value of some subsystems after the end of the life cycle (€) CF t =0 the present value of the future cash flow (€) CF t = n a cash flow in n years (€) C t = j the cost of the investment in each year, including the installation cost in the beginning of its operation (€) IC C the installation cost of each component (€) n C the life cycle of each component (years) r the interest rate (%) 1 Introduction The current work is focused on the economic assessment of a two-stage SORC, where the mechanical energy produced during the expansion is used to drive the High Pressure Pump (HPP) of the RO desalination unit, which is directly coupled with the Rankine engine. The concept of developing a two-stage SORC for RO desalination demonstrates the evolvement of a single-stage low-temperature SORC for RO desalination developed within the framework of COOP-CT2003-507997 EC project, in which several technical and economic aspects were explored. From technical point of view, the main conclusions derived from the study and experimental evaluation of the integrated system, clearly prove that the SORC is technically feasible, robust and reliable and has the capacity to be efficiently coupled with the RO unit [1–3] . However, the fresh water cost of the single-stage system is considerably higher than that of a PV–RO of comparable size [4–7] . In view to increase the efficiency of the single-stage SORC with a simultaneous reduction of fresh water cost the two-stage variant was studied within the framework of 05NON-EU-219, partly financed by the Greek government. The results obtained incorporate, together with significant technical outcomes [8] , the radical deduction of fresh water cost. The research concerning the organic Rankine cycle with its various applications is becoming evident, because it is considered to contribute in the exploitation of low-temperature heat, as well as of solar energy. Therefore the efficiency of such systems is kept low, following closely the low Carnot cycle efficiency in such low temperatures, but with the coupling of renewable energy sources, even if the efficiency is in the order of 4%, the annual produced electricity or desalinated water is significant. There are various technologies for desalinating seawater, as described thoroughly in Ref. [9] , which cover a variety of systems, using direct or indirect coupling with renewables (i.e. solar collectors, photovoltaic, solar ponds and geothermal energy). There are many examples, which deal not only with the technologies of desalinating seawater, but also with electricity production powered either by geothermal or waste heat or even solar energy, such as those found in Refs. [6,10–12] . However, the current work is focused on the use of an organic Rankine cycle for RO desalination. The new concept of introducing a second stage in the organic Rankine cycle has been found to increase the efficiency, but most important the annual production of desalinated water [8] . The approach of the authors to the thermal process is quite different than the one followed in Ref. [13] , where parabolic trough solar collectors have been used and the operating temperatures are much higher than the ones used in the current work, therefore the efficiency of the system in Ref. [13] is expected to be much higher. The effort given here is to exploit solar energy or even low-temperature waste heat for desalinating seawater, which means that the efficiency is expected to be quite low, because of the quite low evaporation/condensation temperature of the two cycles involved. In Ref. [14] an organic Rankine cycle (ORC) for power generation for recovering of low-grade waste heat (below 370 °C) has been investigated. The same application has been tested also in Ref. [15] , but in that case the evaporation temperature was lower and equal to 120 °C. There are also some applications, where the design evaporation temperature is even lower, such as in Ref. [10] , where Nguyen et al. developed a small-scale ORC for electricity production with power output of 1.5 kW. The heat supply is low-temperature heat (at around 81 °C) and although the thermal efficiency is low and around 4.3%, the whole system...

ACS Style

G. Kosmadakis; D. Manolakos; S. Kyritsis; G. Papadakis. Economic assessment of a two-stage solar organic Rankine cycle for reverse osmosis desalination. Renewable Energy 2009, 34, 1579 -1586.

AMA Style

G. Kosmadakis, D. Manolakos, S. Kyritsis, G. Papadakis. Economic assessment of a two-stage solar organic Rankine cycle for reverse osmosis desalination. Renewable Energy. 2009; 34 (6):1579-1586.

Chicago/Turabian Style

G. Kosmadakis; D. Manolakos; S. Kyritsis; G. Papadakis. 2009. "Economic assessment of a two-stage solar organic Rankine cycle for reverse osmosis desalination." Renewable Energy 34, no. 6: 1579-1586.

Journal article
Published: 30 June 2009 in Energy
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This paper presents the detailed laboratory experimental results of a low-temperature Organic Rankine Cycle (ORC) engine coupled with a Reverse Osmosis (RO) desalination unit. In a previous work, the identification of performance of the scroll type expander was presented. At that primary experimental phase an electric brake was co-axially connected to the expander to act as the mechanical load of the ORC engine. The identification of behaviour of the integrated ORC–RO system is a research step ahead since the electric brake is replaced by the RO desalination unit representing the actual system's mechanical load. Several characteristic quantities of both energy supply (ORC) and demand (RO) side have been measured and are illustrated in the current paper. The results show that ORC can be effectively used to exploit low-temperature thermal sources (i.e. in the range from 40 to 70 °C) for desalination of sea or brackish water through the RO process. Such low-temperature values can be available from excess industrial heat, solar collectors and geothermal fields making the ORC–RO process an alternative desalination variant. However, it becomes clear that the system performance strongly depends on the corresponding operation point.

ACS Style

D. Manolakos; G. Kosmadakis; S. Kyritsis; G. Papadakis. Identification of behaviour and evaluation of performance of small scale, low-temperature Organic Rankine Cycle system coupled with a RO desalination unit. Energy 2009, 34, 767 -774.

AMA Style

D. Manolakos, G. Kosmadakis, S. Kyritsis, G. Papadakis. Identification of behaviour and evaluation of performance of small scale, low-temperature Organic Rankine Cycle system coupled with a RO desalination unit. Energy. 2009; 34 (6):767-774.

Chicago/Turabian Style

D. Manolakos; G. Kosmadakis; S. Kyritsis; G. Papadakis. 2009. "Identification of behaviour and evaluation of performance of small scale, low-temperature Organic Rankine Cycle system coupled with a RO desalination unit." Energy 34, no. 6: 767-774.

Journal article
Published: 31 May 2009 in Solar Energy
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The paper presents the on site experimental evaluation of the performance of a low-temperature solar organic Rankine cycle system (SORC) for reverse osmosis (RO) desalination. This work is a research step forward to the experimental evaluation of the SORC under laboratory conditions, where the system was tested using an electric brake as load and an electric thermal heater as heat supply. The difference is that solar collectors have been applied as heat supply and there has been a realistic investigation of the performance of the system under the conditions implied by solar energy. The thermal energy produced by the solar collectors’ array evaporates the refrigerant HFC-134a in the pre-heater–evaporator surfaces of the Rankine engine. The superheated vapour is then driven to the expander, where the generated mechanical work produced from expansion drives the high-pressure pump of the RO desalination unit. The superheated vapour at the expander’s outlet is directed to the condenser and condensates. Finally, the saturated liquid at the condenser outlet is pressurized by a positive displacement pump and the thermodynamic cycle is repeated. A special energy recovery system of Axial Pistons Pumps (APP) has been integrated into the RO unit to minimise the specific energy consumption. The results prove that the above concept is technically feasible and continuous operation is achieved under the intermittent availability of solar energy. However, considerably low efficiency has been observed, in comparison with the results taken under controlled thermal load. Nevertheless, it becomes apparent that further optimisation work is required to improve the system efficiency. The research work has been done within the framework of COOP-CT-2003-507997 contract, partly financed by EC.

ACS Style

D. Manolakos; G. Kosmadakis; S. Kyritsis; George Papadakis. On site experimental evaluation of a low-temperature solar organic Rankine cycle system for RO desalination. Solar Energy 2009, 83, 646 -656.

AMA Style

D. Manolakos, G. Kosmadakis, S. Kyritsis, George Papadakis. On site experimental evaluation of a low-temperature solar organic Rankine cycle system for RO desalination. Solar Energy. 2009; 83 (5):646-656.

Chicago/Turabian Style

D. Manolakos; G. Kosmadakis; S. Kyritsis; George Papadakis. 2009. "On site experimental evaluation of a low-temperature solar organic Rankine cycle system for RO desalination." Solar Energy 83, no. 5: 646-656.

Journal article
Published: 01 March 2008 in Desalination
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ACS Style

Dimitris Manolakos; Essam Mohamed; I. Karagiannis; George Papadakis. Technical and economic comparison between PV-RO system and RO-Solar Rankine system. Case study: Thirasia island. Desalination 2008, 221, 37 -46.

AMA Style

Dimitris Manolakos, Essam Mohamed, I. Karagiannis, George Papadakis. Technical and economic comparison between PV-RO system and RO-Solar Rankine system. Case study: Thirasia island. Desalination. 2008; 221 (1-3):37-46.

Chicago/Turabian Style

Dimitris Manolakos; Essam Mohamed; I. Karagiannis; George Papadakis. 2008. "Technical and economic comparison between PV-RO system and RO-Solar Rankine system. Case study: Thirasia island." Desalination 221, no. 1-3: 37-46.

Journal article
Published: 05 February 2007 in Desalination
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ACS Style

D. Manolakos; G. Papadakis; S. Kyritsis; K. Bouzianas. Experimental evaluation of an autonomous low-temperature solar Rankine cycle system for reverse osmosis desalination. Desalination 2007, 203, 366 -374.

AMA Style

D. Manolakos, G. Papadakis, S. Kyritsis, K. Bouzianas. Experimental evaluation of an autonomous low-temperature solar Rankine cycle system for reverse osmosis desalination. Desalination. 2007; 203 (1-3):366-374.

Chicago/Turabian Style

D. Manolakos; G. Papadakis; S. Kyritsis; K. Bouzianas. 2007. "Experimental evaluation of an autonomous low-temperature solar Rankine cycle system for reverse osmosis desalination." Desalination 203, no. 1-3: 366-374.

Journal article
Published: 01 November 2005 in Desalination
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ACS Style

Dimitris Manolakos; George Papadakis; Essam Mohamed; S. Kyritsis; K. Bouzianas. Design of an autonomous low-temperature solar Rankine cycle system for reverse osmosis desalination. Desalination 2005, 183, 73 -80.

AMA Style

Dimitris Manolakos, George Papadakis, Essam Mohamed, S. Kyritsis, K. Bouzianas. Design of an autonomous low-temperature solar Rankine cycle system for reverse osmosis desalination. Desalination. 2005; 183 (1-3):73-80.

Chicago/Turabian Style

Dimitris Manolakos; George Papadakis; Essam Mohamed; S. Kyritsis; K. Bouzianas. 2005. "Design of an autonomous low-temperature solar Rankine cycle system for reverse osmosis desalination." Desalination 183, no. 1-3: 73-80.

Journal article
Published: 31 January 2004 in Energy
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The present paper regards the implementation of a stand-alone photovoltaic plant in which battery storage is partially replaced by a micro-hydraulic system. The plant was installed on Donoussa Island in the Aegean Sea, Greece to cover basic electricity needs of the remote village of Merssini (13 houses). Lighting, TV set and refrigerator were considered basic electricity needs for each house. The photovoltaic array consists of 300 photovoltaic modules of 60 Wp each, for a combined 18 kWp total installed power. The micro-hydraulic system consists of a water pump of 6 kV A and a water turbine coupled with a DC generator of 7.5 kW and two identical water reservoirs of 150 m3 capacity each. During the day, the load is satisfied directly form the photovoltaic generator through an inverter (UPS unit of 25 kV A, 380 V-3 phases alternative current), while any energy surplus is directed to the pump for pumping water from the low level reservoir (at about 100 m altitude from sea level), to the high level reservoir (at about 200 m altitude from sea level). During the night, water is turbined to the low level reservoir providing energy to the load. There is also a battery bank of 186 cells of 2 V nominal voltage in series, with a total capacity of 100 A h. The batteries cover primarily load peaks. The paper presents first results and experience gained from the system performance.

ACS Style

D Manolakos; G Papadakis; D Papantonis; S Kyritsis. A stand-alone photovoltaic power system for remote villages using pumped water energy storage. Energy 2004, 29, 57 -69.

AMA Style

D Manolakos, G Papadakis, D Papantonis, S Kyritsis. A stand-alone photovoltaic power system for remote villages using pumped water energy storage. Energy. 2004; 29 (1):57-69.

Chicago/Turabian Style

D Manolakos; G Papadakis; D Papantonis; S Kyritsis. 2004. "A stand-alone photovoltaic power system for remote villages using pumped water energy storage." Energy 29, no. 1: 57-69.