Analysis of the Maximum Efficiency and the Maximum Net Power as Objective Functions for Organic Rankine Cycles Optimization.

Maximum efficiency and maximum net power output are some of the most important goals to reach the optimal conditions of organic Rankine cycles. This work compares two objective functions, the maximum efficiency function, ß, and the maximum net power output function, ω. The van der Waals and PC-SAFT equations of state are used to calculate the qualitative and quantitative behavior, respectively. The analysis is performed for a set of eight working fluids, considering hydrocarbons and fourth-generation refrigerants. The results show that the two objective functions and the maximum entropy point are excellent references for describing the optimal organic Rankine cycle conditions. These references enable attaining a zone where the optimal operating conditions of an organic Rankine cycle can be found for any working fluid. This zone corresponds to a temperature range determined by the boiler outlet temperature obtained by the maximum efficiency function, maximum net power output function, and maximum entropy point. This zone is named the optimal temperature range of the boiler in this work.

Thermo-economic and environmental optimization using PSO of solar organic Rankine cycle with flat plate solar collector.

The use of solar energy is considered a potential strategy for the production of electrical energy through thermal heat sources. This article portrays a study framed to be energetic, economic, and environmental fields. This study was carried out in two thermal configurations: the Regenerative Rankine Cycle (RORC) and the Simple Organic Rankine Cycle (SORC), which use solar energy to supply electrical power to a building. The thermodynamic and economic models were proposed for each subsystem of the thermal process, allowing hourly simulations to know the economic indicators such as the payback period (PBP), the levelized cost of energy (LCOE), the specific investment cost (SIC), and the initial investment cost ( C I n v ). The effect of operational variables such as the pressure ratio (rp), the evaporator pinch point temperature (Ap), the condensation pinch point temperature (Tcond), and the solar collector area (Ac) on the Relative Annual Benefit (RAB) were studied. Finally, the Particle Swarm Optimization (PSO) algorithm was implemented to optimize the economic indicators and the environmental impact of the thermal configurations. Results showed that the RORC configuration presented a better performance in terms of generation, purchase, and hourly sale of energy. However, in terms of RAB, the SORC (39,833 USD/year) showed better results in contrast to the RORC (39,604 USD/year) for an evaporator pinch point temperature of 35 °C. Finally, the application of the PSO optimization algorithm allowed the reduction of the LCOE (11.64%), SIC (11.67%), and PBP (11.81%) thermo-economic indicators from the base condition for the SORC, and the reductions obtained in the RORC were LCOE (18.11%), SIC (10.67%), and PBP (11.11%). However, the decrease in environmental Impact for both systems was less than 1% as a consequence of the high contribution of thermal oil in the construction phase of the system.

4E Assessment of an Organic Rankine Cycle (ORC) Activated with Waste Heat of a Flash-Binary Geothermal Power Plant.

In this paper, the 4E assessment (Energetic, Exergetic, Exergoeconomic and Exergoenvironmental) of a low-temperature ORC activated by two different alternatives is presented. The first alternative (S1) contemplates the activation of the ORC through the recovery of waste heat from a flash-binary geothermal power plant. The second alternative (S2) contemplates the activation of the ORC using direct heat from a geothermal well. For both alternatives, the energetic and exergetic models were established. At the same time, the economic and environmental impact models were developed. Finally, based on the combination of the exergy concepts and the economic and ecological indicators, the exergoeconomic and exergoenvironmental performances of the ORC were obtained. The results show higher economic, exergoeconomic and exergoenvironmental profitability for S1. Besides, for the alternative S1, the ORC cycle has an acceptable economic profitability for a net power of 358.4 kW at a temperature of 110 °C, while for S2, this profitability starts being attractive for a power 2.65 times greater than S1 and with a temperature higher than 135 °C. In conclusion, the above represents an area of opportunity and a considerable advantage for the implementation of the ORC in the recovery of waste heat from flash-binary geothermal power plants.

Thermoeconomic analysis of a combined supercritical CO2 reheating under different configurations of Organic Rankine cycle ORC as a bottoming cycle.

Supercritical Brayton cycles have been considered as one of the technologies that present high thermal efficiencies in a wide range of energy conversion systems. Also, these systems can even increase their efficiency by incorporating a suitable bottoming cycle. In this article, a combined supercritical Brayton cycle with an Organic Rankine cycle (ORC) was analyzed. The influence of key system parameters such as the Brayton circuit high-pressure (Phigh), the turbine-1 inlet temperature (TIT), the turbine-1 efficiency ( n t ), and the evaporation pressure ( P e v a p ) on the economic indicators such as the Levelized Cost of Energy (LCOE), the Payback Period (PBP), the Specific Investment Cost (SIC), and net work ( W ˙ n e t ) was studied. Besides, the effect of these parameters on the exergo-economic indicator r k and the relative cost difference r k were studied. Finally, a thermo-economic optimization of the proposed configurations was carried out. The study revealed that the turbine-1 inlet temperature (TIT) was the variable with the most significant effect on the economic and energy indicators of the configurations analyzed. The increase in the turbine temperature up to 850 °C caused a rise of 63.8% for both configurations. Also, the results revealed that the Brayton/SORC configuration presented the best economic performance compared to the Brayton/RORC system. The thermo-economic optimization revealed that temperatures above 800 °C and pressures between 25-30 MPa increase system performance. In addition, the Brayton/SORC configuration has a comparative reduced levelized energy costs and low payback periods, which makes it more attractive.

Solar Energy-Based Future Perspective for Organic Rankine Cycle Applications.

This article explores the patents of solar energy technologies in the organic Rankine cycle (ORC) applications. The conversion of low-quality thermal energy into electricity is one of the main characteristics of an ORC, making efficient and viable technologies available today. However, only a few and outdated articles that analyze patents that use solar energy technologies in ORC applications exist. This leads to a lack of updated information regarding the number of published patents, International Patent Classification (IPC) codes associated with them, technology life cycle status, and the most relevant patented developments. Thus, this article conducts a current investigation of patents published between January 2010 and May 2022 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology and keywords. One thousand two hundred ninety-nine patents were obtained as part of the study and classified in F and Y groups of the IPC. The time-lapse analyzed was between January 2010 and May 2022. In 2014 and 2015, a peak of published patents was observed. China (CN) was the country that published the most significant number of patents worldwide. However, the European Patent Office (EP), the World Intellectual Property Organization (WO), and the United States (US) publish the patents with the highest number of patent citations. Furthermore, the possible trend regarding the development of patents for each technology is presented. A high-performance theoretical ORC plant based on the patent information analyzed by this article is introduced. Finally, exploration of IPC revealed 17 codes related to solar energy technologies in ORC applications not indexed in the main search.

A comparative study of the energy, exergetic and thermo-economic performance of a novelty combined Brayton S-CO2-ORC configurations as bottoming cycles.

This paper presents a comparative study on the energy, exergetic and thermo-economic performance of a novelty thermal power system integrated by a supercritical CO2 Brayton cycle, and a recuperative organic Rankine cycle (RORC) or a simple organic Rankine cycle (SORC). A thermodynamic model was developed applying the mass, energy and exergy balances to all the equipment, allowing to calculate the exergy destruction in the components. In addition, a sensitivity analysis allowed studying the effect of the primary turbine inlet temperature (TIT, PHIGH, rP and TC) on the net power generated, the thermal and exergy efficiency, and some thermo-economic indicators such as the payback period (PBP), the specific investment cost (SIC), and the levelized cost of energy (LCOE), when cyclohexane, acetone and toluene are used as working fluids in the bottoming organic Rankine cycle. The parametric study results show that cyclohexane is the organic fluid that presents the best thermo-economic performance, and the optimization with the PSO method conclude a 2308.91 USD/kWh in the SIC, 0.22 USD/kWh in the LCOE, and 9.89 year in the PBP for the RORC system. Therefore, to obtain technical and economic viability, and increase the industrial applications of these thermal systems, thermo-economic optimizations must be proposed to obtain lower values of the evaluated performance indicators.

A comparative energy and exergy optimization of a supercritical-CO2 Brayton cycle and Organic Rankine Cycle combined system using swarm intelligence algorithms.

This article presents a multivariable optimization of the energy and exergetic performance of a power generation system, which is integrated by a supercritical Brayton Cycle using carbon dioxide, and a Simple Organic Rankine Cycle (SORC) using toluene, with reheater ( S - C O 2 R H - S O R C ), and without reheater ( S - C O 2 N R H - S O R C ) using the PSO algorithm. A thermodynamic model of the integrated system was developed from the application of mass, energy and exergy balances to each component, which allowed the calculation of the exergy destroyed a fraction of each equipment, the power generated, the thermal and exergetic efficiency of the system. In addition, through a sensitivity analysis, the effect of the main operational and design variables on thermal efficiency and total exergy destroyed was studied, which were the objective functions selected in the proposed optimization. The results show that the greatest exergy destruction occurs at the thermal source, with a value of 97 kW for the system without Reheater (NRH), but this is reduced by 92.28% for the system with Reheater (RH). In addition, by optimizing the integrated cycle for a particle number of 25, the maximum thermal efficiency of 55.53% (NRH) was achieved, and 56.95% in the RH system. Likewise, for a particle number of 15 and 20 in the PSO algorithm, exergy destruction was minimized to 60.72 kW (NRH) and 112.06 kW (RH), respectively. Comparative analyses of some swarm intelligence optimization algorithms were conducted for the integrated S-CO2-SORC system, evaluating performance indicators, where the PSO optimization algorithm was favorable in the analyses, guaranteeing that it is the ideal algorithm to solve this case study.