Performance of a 5kWe Organic Rankine Cycle at part-load operation

Ibarra, Mercedes; Rovira, Antonio; Alarcón-Padilla, Diego-César; Blanco, J.

doi:10.1016/j.apenergy.2014.01.057

Cited by 66 publications

(24 citation statements)

References 41 publications

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“…This figure also shows the energy losses produced when the expander operates in under-expansion and, still more, in over-expansion. Other energy losses that contribute to draw this curve are heat losses during expansion, frictions, supply pressure drop, internal leakages [30], or the alternator electrical efficiency operating at partial loads [31]. Furthermore, if the gross electrical efficiency of the cycle is compared with the expander electrical isentropic effectiveness, as Fig.…”

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confidence: 99%

Performance evaluation of an Organic Rankine Cycle (ORC) for power applications from low grade heat sources

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Molés

et al. 2015

Applied Thermal Engineering

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In this paper the performance of an Organic Rankine Cycle (ORC) module, which was designed and built for a specific power application, is experimentally characterized. The ORC tested satisfies the main specifications for an efficient power system, highlighting a volumetric expander with large built-in volume ratio. For tests development, a monitored test bench has been used and adapted to the planned test procedure, which consisted of varying the thermal power input for different condensing conditions. Thereby, 10 steady state points are achieved and analysed according to thermal power input, gross and net electrical powers, electrical cycle efficiencies and expander effectiveness. The results show that the ORC performances are improved for higher thermal oil temperatures, capturing more thermal power, producing more electricity and achieving better cycle efficiencies. The maximum gross electrical efficiency obtained is 12.32 %, for a heat source temperature about 155 ºC and a direct dissipation to the ambient. Moreover, the expander reaches an electrical isentropic effectiveness about 65 % for an optimum pressure ratio around 7, being a suitable system for power applications from low grade heat sources.Keywords: Organic Rankine Cycle (ORC); power applications; test bench; heat recovery; energy efficiency.""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" I ntroductionThe Organic Rankine Cycle (ORC) has been proven as an efficient way for power generation from low grade heat sources [1]. It is a similar power cycle to the steam Rankine cycle, but uses more volatile fluids instead of water to improve the efficiency in low temperature applications [2]. Its operating principle consists of capturing the thermal energy from the heat source through the evaporation of the working fluid and reducing the enthalpy in an expander to produce mechanical work, which is turned into electricity by an electric generator. This is a closed system, which condenses the vapor from the expander outlet and pressurizes the liquid to restart the cycle again. [19] reported that in the literature the usual expander effectiveness ranges between 60-65% with peaks of 68-70%, which is in compliance with their results. The researchers tested a small-size ORC prototype using the working fluid R245fa and a scroll expander, adapted from a commercial HVAC, achieving a net cycle electrical efficiency around 8%. Kane et al. [20] proposed to use two superposed ORCs, each one with an optimized working fluid and expander to overcome the limited pressure range and built-in volume ratio (Vi) of a scroll expander modified from a standard compressor. The working fluids selected were R123 for the topping ORC and R134a for the bottoming ORC. Thereby, the results showed that the superposed cycle achieved a net electrical efficiency upper 12% during tests.As can be seen, the main expansion technology investigated for ORCs, intended for applications in low grade heat sources, is the volumetric or positive displacement machine. The reason is...

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confidence: 99%

Performance evaluation of an Organic Rankine Cycle (ORC) for power applications from low grade heat sources

Peris

Navarro-Esbrí

Molés

et al. 2015

Applied Thermal Engineering

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“…Both expanders showed linear trends for the torque and a peaked curve for mechanical power with respect to the rotation speed. Ibarra et al [9] predicted the off-design performance of a regenerative ORC system using a scroll expander. Both the expander rotation speed and working pressure were adjusted to meet the load requirement of ORC.…”

Section: Introductionmentioning

confidence: 99%

Off-design performance comparison of an organic Rankine cycle under different control strategies

Yong

et al. 2015

Applied Energy

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“…The methodology of the pump adopted in [16,19] is employed in this work. The non-dimensional performance curve of the refrigerant pump is derived from a centrifugal pump in a real power plant, as presented in Figure 6.…”

Section: Pumpmentioning

confidence: 99%

“…Nevertheless, they only considered the off-design performance of the preheater. Ibarra et al [16] researched the off-design performance of ORCs from a thermodynamic perspective and discovered that the isentropic efficiency of a scroll expander significantly influenced the cycle performance. In this work, both expander rotation speed and working pressure were regulated to satisfy different load demands.…”

Section: Introductionmentioning

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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Performance of a 5kWe Organic Rankine Cycle at part-load operation

Cited by 66 publications

References 41 publications

Performance evaluation of an Organic Rankine Cycle (ORC) for power applications from low grade heat sources

Performance evaluation of an Organic Rankine Cycle (ORC) for power applications from low grade heat sources

Off-design performance comparison of an organic Rankine cycle under different control strategies

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

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