Comparison of sub- and supercritical Organic Rankine Cycles for power generation from low-temperature/low-enthalpy geothermal wells, considering specific net power output and efficiency

Vetter, Christian; Wiemer, Hans-Joachim; Kühn, Dietmar

doi:10.1016/j.applthermaleng.2012.10.042

Cited by 122 publications

(53 citation statements)

References 6 publications

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“…[128] In previous studies,V etter et al showedt hat significant performance improvementsw ere possible under supercritical conditions. [129] As tudy in Bayreuth comparedt he specific costs of sub-and supercritical cycles,a nd showed as horter paybackp eriod for as upercritical RC318 cycle than that for as ubcriticalc ycle of the same fluid ands pecific investment cost (SIC). [130] They concluded that as upercriticalm ode of operation had significant potential for increasing gross power at medium temperatures (130-160 8C).…”

Section: Tool Design For the Thermoeconomic Optimization Of Geothermamentioning

confidence: 99%

Integrated Research as Key to the Development of a Sustainable Geothermal Energy Technology

et al. 2017

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As estimated by the International Energy Agency, geothermal power can contribute to 3.5 % of worldwide power and 3.9 % to heat production by 2050. This includes the development of enhanced geothermal systems (EGSs) in low‐enthalpy systems. EGS technology is still in an early stage of development. Pushing EGS technologies towards market maturity requires a long‐term strategic approach and massive investments in research and development. Comprehensive multidisciplinary research programs that combine fundamental and applied concepts to tackle technological, economic, ecological, and safety challenges along the EGS process chain are needed. The Karlsruhe Institute of Technology (KIT) has defined a broad research program on EGS technology development following the necessity of a transdisciplinary approach. The research concept is embedded in the national research program of the Helmholtz Association and is structured in four clusters: reservoir characterization and engineering, thermal water circuit, materials and geoprocesses, and power plant operation. The proximity to industry, closely interlinked with fundamental research, forms the basis of a target‐orientated concept. The present paper aims to give an overview of geothermal research at KIT and emphasizes the need for concerted research efforts at the international level to accelerate technological breakthrough of EGS as an essential part of a future sustainable energy system.

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Section: Tool Design For the Thermoeconomic Optimization Of Geothermamentioning

confidence: 99%

Integrated Research as Key to the Development of a Sustainable Geothermal Energy Technology

et al. 2017

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“…These variables are regarded as decision variables to conduct a single-objective optimization based on a genetic algorithm (GA). The net power output is chosen as optimization objective since the maximum value is desirable for a geothermal power system [29,30]. In this work, all the programs are written in MATLAB 2011b (The MathWorks, Natick, Massachusetts, USA), and the thermodynamic properties are attained from REFPROP 9.0 (NIST, Gaithersburg, Maryland, USA).…”

Section: System Components Modeling and Designmentioning

confidence: 99%

Off-Design Performances of Subcritical and Supercritical Organic Rankine Cycles in Geothermal Power Systems under an Optimal Control Strategy

Gao

Liu

2017

Energies

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Abstract:The conditions of heat source and heat sink in a geothermal ORC system may frequently vary due to variations in geological conditions, ambient temperature and actual operation. In this study, an off-design performance prediction model for geothermal ORC systems is developed according to special designs of critical components, and an optimal control strategy which regards the turbine guide vane angle, the refrigerant pump rotational speed and the cooling water mass flow rate as control variables is proposed to maximize the net power output. Off-design performances of both subcritical and supercritical ORCs are analyzed. The results indicate that, under the optimal control strategy, the net power output of both ORCs increase with greater geothermal water mass flow rate, higher geothermal water inlet temperature and lower cooling water inlet temperature, which is mainly due to a greater working fluid mass flow rate, higher turbine inlet pressure and lower condensing pressure, respectively. The net power output of supercritical ORC is always greater than that of subcritical ORC within the range of this study, but the difference tends to decrease when supercritical ORC activates the geothermal water reinjection temperature restriction.

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“…The pinch point temperature difference showed to have a significant influence on the maximum net power output. A higher thermal efficiency of 10.1% is achieved when operating with supercritical vapour in the heat exchanger and using propane as working fluid [8]. As a continuation of the previous work and in order to determine the most compact design and obtain the highest efficiency, an evaluation of several types of heat exchangers such as double-pipe, shell-and-tube and plate heat exchangers operating only at supercritical conditions was made [9].…”

Section: Introductionmentioning

confidence: 99%

“…Both the heat transfer coefficients and the pressure drop show a similar trend and both increase by raising the heat flux and mass flow rate of the working fluid. Furthermore, numerical analysis on the net power output and efficiency at subcritical and supercritical operating conditions of a low-enthalpy geothermal (150 • C) ORC is done by examining 12 working fluids [8]. For the optimisation procedure, a counter-current heat exchanger with a pinch point temperature difference of 20 K is assumed.…”

Section: Introductionmentioning

confidence: 99%

Experimental Assessment of a Helical Coil Heat Exchanger Operating at Subcritical and Supercritical Conditions in a Small-Scale Solar Organic Rankine Cycle

et al. 2017

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Abstract: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/m 2 . 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.

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Comparison of sub- and supercritical Organic Rankine Cycles for power generation from low-temperature/low-enthalpy geothermal wells, considering specific net power output and efficiency

Cited by 122 publications

References 6 publications

Integrated Research as Key to the Development of a Sustainable Geothermal Energy Technology

Integrated Research as Key to the Development of a Sustainable Geothermal Energy Technology

Off-Design Performances of Subcritical and Supercritical Organic Rankine Cycles in Geothermal Power Systems under an Optimal Control Strategy

Experimental Assessment of a Helical Coil Heat Exchanger Operating at Subcritical and Supercritical Conditions in a Small-Scale Solar Organic Rankine Cycle

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