Waste heat recovery (WHR) from exhaust gases in natural gas engines improves the overall conversion efficiency. The organic Rankine cycle (ORC) has emerged as a promising technology to convert medium and low-grade waste heat into mechanical power and electricity. This paper presents the energy and exergy analyses of three ORC-WHR configurations that use a coupling thermal oil circuit. A simple ORC (SORC), an ORC with a recuperator (RORC), and an ORC with double-pressure (DORC) configuration are considered; cyclohexane, toluene, and acetone are simulated as ORC working fluids. Energy and exergy thermodynamic balances are employed to evaluate each configuration performance, while the available exhaust thermal energy variation under different engine loads is determined through an experimentally validated mathematical model. In addition, the effect of evaporating pressure on the net power output, thermal efficiency increase, specific fuel consumption, overall energy conversion efficiency, and exergy destruction is also investigated. The comparative analysis of natural gas engine performance indicators integrated with ORC configurations present evidence that RORC with toluene improves the operational performance by achieving a net power output of 146.25 kW, an overall conversion efficiency of 11.58%, an ORC thermal efficiency of 28.4%, and a specific fuel consumption reduction of 7.67% at a 1482 rpm engine speed, a 120.2 L/min natural gas flow, 1.784 lambda, and 1758.77 kW of mechanical engine power.Energies 2019, 12, 2378 2 of 22 and exergy efficiencies and minimizing exergy destruction [3]. Nevertheless, ORC-engine coupling must be carefully designed to avoid safety, performance, and revenue issues such as gas-fluid contact, as well as weight, complexity, and backpressure increase [4].ORC-WHR research has addressed the integration between ORC and combustion engines. Plenty of studies have established that ORC improves the overall conversion efficiency by increasing net power production without penalizing fuel consumption. Patel and Doyle [5] presented a first attempt for WHR from diesel engines by using ORC. Their ORC system achieved an overall power increase of 13% in a Mack 676 diesel vehicle engine without increasing fuel consumption. Peris et al. [6] simulated six ORC configurations for WHR from cooling water in internal combustion engines (ICE) by using 10 non-flammable fluids. Their study showed that ICE electric efficiency could be increased by 4.9-5.3%, by achieving overall conversion efficiencies up to 7.15% at a relatively low-temperature cooling water (90 • C). Yu et al.[7] simulated a diesel engine-ORC integration for WHR from the engine exhaust gases and cooling system by using R245fa as the ORC working fluid. Their results showed that 75% of exhaust gases energy and 9.5% of cooling water energy could be recovered if ORC operating conditions are optimized and controlled to maintain the power output. However, these results are limited to an exergetic analysis of a single ORC configuration. Lu et al. [8] ...

A bibliometric analysis of proton exchange membrane fuel cells (PEMFCs) content from a total of 15.020 research publications was conducted between 2008 and 2018, the papers being detailed in the online version of SCI-Expanded, Thomson Reuters Web of Science. Data processing tools such as Hitscite, CiteSpace, ArcGIS and Ucinet 6 were used to process the information. The parameters analyzed in the analysis were: type of document; the language of publication; volume and characteristics of publication output; publication by journals; performance of countries and research institutions; research trends and visibility. The study showed that "Fuel'', "Cell", "Membrane “and "Proton" were found in most of the titles of the documents, while "Performance", "Pemfc”, "Pem Fuel Cell" and "Fuel Cell" were the keywords most commonly used in documents. The analysis found that PEMFC studies have tended to be growing and that leading peer-reviewed journals have produced numerous publications on the subject. The investigation revealed that the country with the most significant production in the field is USA with a contribution of 3009; 20% of the total publications. Followed by China 2480; 16.5%, South Korea 1273; 8.5% and Germany 1121; 7.5%, showing to the main world powers as the most significant contributors to the research.

Waste-heat recovery (WHR) systems based on the organic Rankine cycle (ORC) improve the thermal efficiency of natural gas engines because they generate additional electric power without consuming more gas fuel. However, to obtain a cost-effective design, thermoeconomic criteria must be considered to facilitate installation, operation, and penetration into real industrial contexts. Therefore, a thermo-economic analyses of a simple ORC (SORC), ORC with recuperator (RORC) and a double-pressure ORC (DORC) integrated with a 2 MW Jenbacher JMS 612 GS-N. L is presented using toluene as the organic working fluid. In addition, the cost rate balances for each system are presented in detail, with the analysis of some thermoeconomics indicator such as the relative cost difference, the exergoeconomic factor, and the cost rates of exergy destruction and exergy loss. The results reported opportunities to improve the thermoeconomic performance in the condenser and turbine, because the exergoeconomic factor for the condenser and the turbine were in the RORC (0.41 and 0.90), and DORC (0.99 and 0.99) respectively, which implies for the RORC configuration that 59% and 10% of the increase of the total cost of the system is caused by the exergy destruction of these devices. Also, the pumps present the higher values of relative cost difference and exergoeconomic factor for B1 (rk = 8.5, fk = 80%), B2 (rk = 8, fk = 85%).

A multiobjective optimization of an organic Rankine cycle (ORC) evaporator, operating with toluene as the working fluid, is presented in this paper for waste heat recovery (WHR) from the exhaust gases of a 2 MW Jenbacher JMS 612 GS-N.L. gas internal combustion engine. Indirect evaporation between the exhaust gas and the organic fluid in the parallel plate heat exchanger (ITC2) implied irreversible heat transfer and high investment costs, which were considered as objective functions to be minimized. Energy and exergy balances were applied to the system components, in addition to the phenomenological equations in the ITC2, to calculate global energy indicators, such as the thermal efficiency of the configuration, the heat recovery efficiency, the overall energy conversion efficiency, the absolute increase of engine thermal efficiency, and the reduction of the break-specific fuel consumption of the system, of the system integrated with the gas engine. The results allowed calculation of the plate spacing, plate height, plate width, and chevron angle that minimized the investment cost and entropy generation of the equipment, reaching 22.04 m 2 in the heat transfer area, 693.87 kW in the energy transfer by heat recovery from the exhaust gas, and 41.6% in the overall thermal efficiency of the ORC as a bottoming cycle for the engine. This type of result contributes to the inclusion of this technology in the industrial sector as a consequence of the improvement in thermal efficiency and economic viability.The optimization of equipment used for waste heat recovery (WHR) has been studied by many researchers using different methods and formulations. Technical challenges, such as the high acquisition costs and entropy generation inside the heat exchanger, represent an improvement opportunity to increase ORC performance [4]. In these cases, mathematical tools can be used to find the best solutions through a stochastic search according to the objective selected. Holland [5] and De Jong [6] introduced the concept of genetic algorithms in publications, although these were not applied to the heat transfer field of knowledge.Several researchers have applied optimization techniques to design industrial equipment using thermodynamic and economic approaches, specifically in heat exchangers in the last years. Martin et al.[7] used a dimensionless function proportional to the sum of annual investment costs and operating costs, where the minimum of this function made it possible to determine the optimal Reynolds number, which depends on the type of heat exchanger chosen. In other research, Niclout et al. [8] describe an optimization problem in which objective functions, such as manufacturing cost and heat exchanger volume, as well as operating and manufacturing constraints were studied considering as decision variables the geometric parameters of the fins. To solve this problem, the author developed nonlinear programming of mixed integer numbers, like other options of the solution. Nevertheless, his work is limited by not considering the...

This paper presents the application of a systematic methodology to obtain a semi-physical model of phenomenological base for a 2 MW internal combustion engine to generate electric power operating with natural gas, as a function of the average thermodynamic value normally measured in industrial applications. Specifically, the application of the methodology is focused on the cylinders, exhaust manifold, and turbocharger turbine sections. The proposed model was validated with actual operating data, obtaining an error rate not exceeding 5%, which allow a thermal characterization of the Jenbacher JMS 612 GS-N based on the model. A parametric analysis is conducted; considering the volumetric efficiency, the output electric power, the effective efficiency, the exhaust gas temperature, the turbine mass flow, the specific fuel consumption under the nominal operation conditions, which is 1.16 bar in the gas pressure, 65 °C in the cooling water temperature, 35 °C in the average ambient temperature, and 1500 rpm. The results of this model can be used to evaluate the thermodynamic performance parameters of waste heat recovery systems. On the other hand, new control strategies and the implementation of state observers for the detection and diagnosis of failures can be developed based on the proposed model.

A hybrid system was analyzed and optimized to produce electric energy in non-interconnected zones in the Colombian Caribbean region, contributing to the reduction of greenhouse gas emissions and the improvement in efficient energy management. A comparative analysis of the performance of hybrid was conducted using a proposed model, built with historical data for meteorological conditions, wind speed, and solar radiation. The model is integrated by a Southwest Wind Power Inc. wind turbine AIR 403, a proton-exchange membrane fuel cell (PEM), an electrolyzer, a solar panel, and a regulator based on proportional, integral, and derivative (PID) controllers to manipulate oxygen and hydrogen flow entering in the fuel cell. The transient responses of the cell voltage, current, and power were obtained for the demand of 200 W under changes in solar radiation and wind speed for each day of the year 2013 in different meteorological stations, such as Ernesto Cortissoz airport, Puerto Bolívar, Alfonso Lopez airport, and Simon Bolívar airport. Through the adjustment of the hydrogen and oxygen flow into the fuel cell, the maximum contribution of power generation from the fuel cell was presented for the Simon Bolívar airport in November with a value of 158.35 W (9.45%). Multiobjective design optimization under a Pareto diagram front is presented for each place studied to minimize the levelized cost of energy and CO2 emission, where the objective control variables are the number of panel and stack in the photovoltaic (PV) system and PEM.

To contribute to the economic viability of waste heat recovery systems application based on the organic Rankine cycle (ORC) under real operation condition of natural gas engines, this article presents a thermoeconomic optimization results using the particle swarm optimization (PSO) algorithm of a simple ORC (SORC), regenerative ORC (RORC), and double-stage ORC (DORC) integrated to a GE Jenbacher engine type 6, which have not been reported in the literature. Thermoeconomic modeling was proposed for the studied configurations to integrate the exergetic analysis with economic considerations, allowing to reduce the thermoeconomic indicators that most influence the cash flow of the project. The greatest opportunities for improvement were obtained for the DORC, where the results for maximizing net power allowed the maximum value of 99.52 kW, with 85% and 80% efficiencies in the pump and turbine, respectively, while the pinch point temperatures of the evaporator and condenser must be 35 and 16 °C. This study serves as a guide for future research focused on the thermoeconomic performance optimization of an ORC integrated into a natural gas engine.

The waste heat recovery system (WHRS) is a good alternative to provide a solution to the waste energy emanated in the exhaust gases of the internal combustion engine (ICE). Therefore, it is useful to carry out research to improve the thermal efficiency of the ICE through a WHRS based on the organic Rankine cycle (ORC), since this type of system takes advantage of the heat of the exhaust gases to generate electrical energy. The organic working fluid selection was developed according to environmental criteria, operational parameters, thermodynamic conditions of the gas engine, and investment costs. An economic analysis is presented for the systems operating with three selected working fluids: toluene, acetone, and heptane, considering the main costs involved in the design and operation of the thermal system. Furthermore, an exergo-advanced study is presented on the WHRS based on ORC integrated to the ICE, which is a Jenbacher JMS 612 GS-N of 2 MW power fueled with natural gas. This advanced exergetic analysis allowed us to know the opportunities for improvement of the equipment and the increase in the thermodynamic performance of the ICE. The results show that when using acetone as the organic working fluid, there is a greater tendency of improvement of endogenous character in Pump 2 of around 80%. When using heptane it was manifested that for the turbine there are near to 77% opportunities for improvement, and the use of toluene in the turbine gave a rate of improvement of 70%. Finally, some case studies are presented to study the effect of condensation temperature, the pinch point temperature in the evaporator, and the pressure ratio on the direct, indirect, and fixed investment costs, where the higher investment costs were presented with the acetone, and lower costs when using the toluene as working fluid.