scholarly journals Exergy Analysis of Two-Stage Organic Rankine Cycle Power Generation System

Entropy ◽  
2020 ◽  
Vol 23 (1) ◽  
pp. 43
Author(s):  
Guanglin Liu ◽  
Qingyang Wang ◽  
Jinliang Xu ◽  
Zheng Miao
Keyword(s):  
Heat Source ◽  
Organic Rankine Cycle ◽  
Exergy Efficiency ◽  
Working Fluid ◽  
Two Stage ◽  
Working Fluids ◽  
Source Temperature ◽  
Split Ratio ◽  
Heat Source Temperature ◽  
Stage System

Organic Rankine cycle (ORC) power generation is an effective way to convert medium and low temperature heat into high-grade electricity. In this paper, the subcritical saturated organic Rankine cycle system with a heat source temperature of 100~150 °C is studied with four different organic working fluids. The variations of the exergy efficiencies for the single-stage/two-stage systems, heaters, and condensers with the heat source temperature are analyzed. Based on the condition when the exergy efficiency is maximized for the two-stage system, the effects of the mass split ratio of the geothermal fluid flowing into the preheaters and the exergy efficiency of the heater are studied. The main conclusions include: The exergy efficiency of the two-stage system is affected by the evaporation temperatures of the organic working fluid in both the high temperature and low temperature cycles and has a maximum value. Under the same heat sink and heat source parameters, the exergy efficiency of the two-stage system is larger than that of the single-stage system. For example, when the heat source temperature is 130 °C, the exergy efficiency of the two-stage system is increased by 9.4% compared with the single-stage system. For the two-stage system, analysis of the four organic working fluids shows that R600a has the highest exergy efficiency, although R600a is only suitable for heat source temperature below 140 °C, while other working fluids can be used in systems with higher heat source temperatures. The mass split ratio of the fluid in the preheaters of the two-stage system depends on the working fluid and the heat source temperature. As the heat source temperature increases, the range of the split ratio becomes narrower, and the curves are in the shape of an isosceles triangle. Therefore, different working fluids are suitable for different heat source temperatures, and appropriate working fluid and split ratio should be determined based on the heat source parameters.

Analysis of novel regenerative thermo-mechanical refrigeration system integrated with isobaric engine

2020 ◽  
pp. 1-27
Author(s):  
Ahmad K. Sleiti ◽  
Wahib Al-Ammari ◽  
Mohammed Al-Khawaja
Keyword(s):  
Heat Source ◽  
Environmental Effects ◽  
Power Efficiency ◽  
Waste Heat ◽  
Working Fluid ◽  
Refrigeration System ◽  
Cooling Systems ◽  
Working Fluids ◽  
Source Temperature ◽  
Heat Source Temperature

Abstract Refrigerants of the conventional cooling systems contribute to global warming and ozone depletion significantly, therefore it is necessary to develop new cooling systems that use renewable energy resources and waste heat to perform the cooling function with eco-friendly working fluids. To address this, the present study introduces and analyzes a novel regenerative thermo-mechanical refrigeration system that can be powered by renewable heat sources (solar, geothermal, or waste heat). The system consists of a novel expander-compressor unit (ECU) integrated with a vapor compression refrigeration system. The integrated system operates at the higher-performance supercritical conditions of the working fluids as opposed to the lower-performance subcritical conditions. The performance of the system is evaluated based on several indicators including the power loop efficiency, the coefficient of performance (COP) of the cooling loop, and the expander-compressor diameters. Several working fluids were selected and compared for their suitability based on their performance and environmental effects. It was found that for heat source temperature below 100 °C, adding the regenerator to the system has no benefit. However, the regenerator increases the power efficiency by about 1 % for a heat source temperature above 130 °C. This was achieved with a very small size regenerator (Dr = 6.5 mm, Lr = 142 mm). Results show that there is a trade-off between high-performance fluids and their environmental effects. Using R32 as a working fluid at heat source temperature Th=150 °C and cold temperature Tc1=40 °C, the system produces a cooling capacity of 1 kW with power efficiency of 10.23 %, expander diameter of 53.12 mm, and compressor diameter of 75.4mm.

scholarly journals Operational Optimisation of a Non-Recuperative 1-kWe Organic Rankine Cycle Engine Prototype

2019 ◽  
Vol 9 (15) ◽  
pp. 3024 ◽  
Author(s):  
Chinedu K. Unamba ◽  
Paul Sapin ◽  
Xiaoya Li ◽  
Jian Song ◽  
Kai Wang ◽  
...  
Keyword(s):  
Steady State ◽  
Heat Source ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Electric Heater ◽  
Part Load ◽  
Source Temperature ◽  
Heat Source Temperature

Several heat-to-power conversion technologies are being proposed as suitable for waste-heat recovery (WHR) applications, including thermoelectric generators, hot-air (e.g., Ericsson or Stirling) engines and vapour-cycle engines such as steam or organic Rankine cycle (ORC) power systems. The latter technology has demonstrated the highest efficiencies at small and intermediate scales and low to medium heat-source temperatures and is considered a suitable option for WHR in relevant applications. However, ORC systems experience variations in performance at part-load or off-design conditions, which need to be predicted accurately by empirical or physics-based models if one is to assess accurately the techno-economic potential of such ORC-WHR solutions. This paper presents results from an experimental investigation of the part-load performance of a 1-kWe ORC engine, operated with R245fa as a working fluid, with the aim of producing high-fidelity steady-state and transient data relating to the operational performance of this system. The experimental apparatus is composed of a rotary-vane pump, brazed-plate evaporator and condenser units and a scroll expander magnetically coupled to a generator with an adjustable resistive load. An electric heater is used to provide a hot oil-stream to the evaporator, supplied at three different temperatures in the current study: 100, 120 and 140 ∘ C. The optimal operating conditions, that is, pump speed and expander load, are determined at various heat-source conditions, thus resulting in a total of 124 steady-state data points used to analyse the part-load performance of the engine. A maximum thermal efficiency of 4.2 ± 0.1% is reported for a heat-source temperature of 120 ∘ C, while a maximum net power output of 508 ± 2 W is obtained for a heat-source temperature at 140 ∘ C. For a 100- ∘ C heat source, a maximum exergy efficiency of 18.7 ± 0.3% is achieved. A detailed exergy analysis allows us to quantify the contribution of each component to the overall exergy destruction. The share of the evaporator, condenser and expander components are all significant for the three heat-source conditions, while the exergy destroyed in the pump is negligible by comparison (below 4%). The data can be used for the development and validation of advanced models capable of steady-state part-load and off-design performance predictions, as well as predictions of the transient/dynamic operation of ORC systems.

scholarly journals Utilisation of bleed steam heat to increase the upper heat source temperature in low-temperature ORC

2011 ◽  
Vol 32 (3) ◽  
pp. 57-70 ◽  
Author(s):  
Dariusz Mikielewicz ◽  
Jarosław Mikielewicz
Keyword(s):  
Power Plant ◽  
Low Temperature ◽  
Heat Source ◽  
Silicone Oil ◽  
Hot Water ◽  
Working Fluid ◽  
Preliminary Heating ◽  
Source Temperature ◽  
Heat Source Temperature ◽  
Steam Heat

Utilisation of bleed steam heat to increase the upper heat source temperature in low-temperature ORC In the paper presented is a novel concept to utilize the heat from the turbine bleed to improve the quality of working fluid vapour in the bottoming organic Rankine cycle (ORC). That is a completely novel solution in the literature, which contributes to the increase of ORC efficiency and the overall efficiency of the combined system of the power plant and ORC plant. Calculations have been accomplished for the case when available is a flow rate of low enthalpy hot water at a temperature of 90 °C, which is used for preliminary heating of the working fluid. That hot water is obtained as a result of conversion of exhaust gases in the power plant to the energy of hot water. Then the working fluid is further heated by the bleed steam to reach 120 °C. Such vapour is subsequently directed to the turbine. In the paper 5 possible working fluids were examined, namely R134a, MM, MDM, toluene and ethanol. Only under conditions of 120 °C/40 °C the silicone oil MM showed the best performance, in all other cases the ethanol proved to be best performing fluid of all. Results are compared with the "stand alone" ORC module showing its superiority.

Performance of Working Fluids for Power Generation in a Supercritical Organic Rankine Cycle

2012 ◽  
Author(s):  
Rachana Vidhi ◽  
Sarada Kuravi ◽  
Saeb Besarati ◽  
E. K. Stefanakos ◽  
D. Yogi Goswami ◽  
...  
Keyword(s):  
Power Generation ◽  
Heat Source ◽  
Thermal Efficiency ◽  
Thermodynamic Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluids ◽  
Source Temperature ◽  
Heat Source Temperature ◽  
Organic Fluids

This paper reports on the performance of various organic refrigerants and their mixtures as working fluids for power generation in a supercritical Rankine cycle (SRC) from geothermal sources. Organic fluids that have zero or very low ozone depletion potential and are environmentally safe are selected for this study. Geothermal source temperature is varied from 125–200°C, and the cooling water temperature is changed from 10–20°C. The effect of varying operating conditions on the performance of the thermodynamic cycle has been analyzed. Operating pressure of the cycle has been optimized for thermal efficiency for each fluid at each source temperature. The condensation pressure is determined by the cooling condition and is kept fixed for each condensation temperature. Energy and exergy efficiencies of the cycle have been obtained for the pure fluids as a function of heat source temperature. Mixtures of organic fluids have been analyzed and effect of composition on performance of the thermodynamic cycle has been studied. It is observed that thermal efficiency over 20% can be achieved for 200°C heat source temperature and the lowest cooling temperature. When mixtures are considered as working fluids, the thermal efficiency of the cycle is observed to remain between the thermal efficiencies of the constituent fluids.

scholarly journals Configuration Selection of the Multi-Loop Organic Rankine Cycle for Recovering Energy from a Single Source

Entropy ◽  
2021 ◽  
Vol 23 (11) ◽  
pp. 1435
Author(s):  
Youyi Li ◽  
Tianhao Tang
Keyword(s):  
Heat Source ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Optimal Solution ◽  
Rankine Cycle ◽  
Optimal Number ◽  
Exergy Efficiency ◽  
Working Fluid ◽  
Levelized Cost Of Electricity ◽  
Multi Objective

The Organic Rankine Cycle (ORC) is a well-established way to recover energy from a single waste heat source. This paper aims to select the suitable configuration, number of loops, and working fluids for the Multi-Loop ORC (MLORC) by using multi-objective optimization. The thermodynamic and economic performance of MLORC in three various configurations was analyzed. Multi-objective optimizations of the series and parallel MLORC using different working fluid groups were conducted to find the optimal configuration, number of loops, and working fluid combination. The analysis results show that the series–parallel MLORC performed the worst among the three configurations. The optimization results reveal that series MLORC has a higher exergy efficiency than the parallel MLORC. The exergy efficiency of the optimal solution in series dual-loop, triple-loop, and quadruple-loop ORC is 9.3%, 7.98%, and 6.23% higher than that of parallel ORC, respectively. Furthermore, dual-loop is the optimal number of cycles for recovering energy from a single heat source, according to the grey relational grade. Finally, the series dual-loop ORC using cyclohexane\cyclohexane was the suitable configuration for utilizing a single waste heat source. The exergy efficiency and levelized cost of electricity of the series dual-loop ORC with the optimal parameters are 62.18% and 0.1509 $/kWh, respectively.

scholarly journals Design and experimental research on the combined flash-binary geothermal power generation system driven by low-medium temperature geothermal system

2020 ◽  
Vol 24 (2 Part A) ◽  
pp. 831-842
Author(s):  
Chao Luo ◽  
Jun Zhao ◽  
Yongzhen Wang ◽  
Hongmei Yin ◽  
Qingsong An ◽  
...  
Keyword(s):  
Power Generation ◽  
Heat Source ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Hot Water ◽  
Geothermal Resource ◽  
Medium Temperature ◽  
Source Temperature ◽  
Heat Source Temperature ◽  
Variable Capacity

To match for the different temperature of the geothermal resource and strengthen the flexibility of organic Rankine cycle, a variable capacity power generation superstructure based on flash and organic Rankine cycle for geothermal energy was proposed. A combined flash-binary experimental prototype is newly established to investigate thermodynamic performance both on system and equipment in this paper. Pressured hot water is adopted as the extensive worldwide existed hydrothermal geothermal resource, eliminating the influence of the used heat transfer oil on evaporating process. The experimental results show that there is an optimal mass-flow rate of R245fa under the condition of different heat source temperature. Flash and binary power subsystem dominate the flash-binary power system, respectively, when the heat source temperature is 120? and 130?. The isotropic efficiency of modified compressor just between 0.2 and 0.25. The power output of per ton geofluid are 0.78 kWh/t and 1.31 kWh/t, respectively, when the heat source temperature are 120? and 130?. These results will predict the operation data of flash-binary power plant driven by the low-medium temperature geothermal water for construction in western of China.

scholarly journals Experimental and Techno-Economic Analysis of Solar-Geothermal Organic Rankine Cycle Technology for Power Generation in Nepal

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Suresh Baral
Keyword(s):  
Power Generation ◽  
Heat Source ◽  
Power Output ◽  
Solar Collector ◽  
Hot Spring ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Maximum Temperature ◽  
Working Fluid ◽  
Working Fluids

The current research study focuses on the feasibility of stand-alone hybrid solar-geothermal organic Rankine cycle (ORC) technology for power generation from hot springs of Bhurung Tatopani, Myagdi, Nepal. For the study, the temperature of the hot spring was measured on the particular site of the heat source of the hot spring. The measured temperature could be used for operating the ORC system. Temperature of hot spring can also further be increased by adopting the solar collector for rising the temperature. This hybrid type of the system can have a high-temperature heat source which could power more energy from ORC technology. There are various types of organic working fluids available on the market, but R134a and R245fa are environmentally friendly and have low global warming potential candidates. The thermodynamic models have been developed for predicting the performance analysis of the system. The input parameter for the model is the temperature which was measured experimentally. The maximum temperature of the hot spring was found to be 69.7°C. Expander power output, thermal efficiency, heat of evaporation, solar collector area, and hybrid solar ORC system power output and efficiency are the outputs from the developed model. From the simulation, it was found that 1 kg/s of working fluid could produce 17.5 kW and 22.5 kW power output for R134a and R245fa, respectively, when the geothermal source temperature was around 70°C. Later when the hot spring was heated with a solar collector, the power output produced were 25 kW and 30 kW for R134a and R245fa, respectively, when the heat source was 99°C. The study also further determines the cost of electricity generation for the system with working fluids R134a and R245fa to be $0.17/kWh and $0.14/kWh, respectively. The levelised cost of the electricity (LCOE) was $0.38/kWh in order to be highly feasible investment. The payback period for such hybrid system was found to have 7.5 years and 10.5 years for R245fa and R134a, respectively.

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