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13:30   Poster session
System-search PERFORMANCE ANALYSIS OF ORC SYSTEM WITH IHE USING THE ZEOTROPIC MIXTURE AND THE PURE WORKING FLUID FOR VEHICLE CNG ENGINE
Songsong Song, Hongguang Zhang
Abstract: The thermal efficiency of most compressed natural gas (CNG) engines is about 30%, large amount fuel energy is rejected from CNG engines to the surroundings as waste heat, with a significant fraction through the exhaust [1]. Therefore, recovering the exhaust waste heat from CNG engines so as to improve thermal efficiency and save fuel has become a hot focus of recent research work. The organic Rankine cycle (ORC) is an effective method to recover waste heat from exhaust waste heat of internal combustion engines (ICE)[2]. For the working fluids of ORC system, the match of organic working fluids with heat source and systems significantly affects system performance. In this paper we analyze the exhaust characteristics from a six-cylinder CNG engine over its whole operating range by engine experiments, and a set of ORC system with internal heat exchanger (IHE) is designed to recover exhaust waste heat from the CNG engine. The organic working fluids under investigation are the pure working fluid R245fa and the zeotropic mixture R416A. Subsequently, the influence of the two different working fluids on performance parameters such as net power output, thermal efficiency, exergy efficiency and output energy density of working fluid are analyzed. The results show that R416A performs better. Finally, a combined CNG engine and ORC system with IHE is defined to evaluate the performance improvement. Results show that, Compared with the CNG engine, the thermal efficiency of the combined system can be increased by a maximum 7%.
System-search A NEW ULTRA-LOW GWP ORC WORKING FLUID
Gregory Smith, Abdennacer Achaichia, Raymond Thomas
Abstract: Organic Rankine Cycle system designs that operate with hydrofluorocarbon working fluids such as HFC-134a (1,1,1,2-tetrafluoroethane) and HFC-245fa (1,1,1,3,3-pentafluoropropane) have been operating in the field for a number of years, and HFC-245fa has emerged as a leading working fluid choice. These systems have demonstrated environmental benefits that validate their current and future use. Even so, there is great interest among system OEMs, equipment end-users, regulatory agencies, and the public to embrace new low global warming technologies. Honeywell has developed a fluid that can serve as a replacement for HFC-245fa in foam expansion, aerosols, and organic Rankine cycle applications, which has an ultra-low global warming potential of 1. This working fluid is fluorinated olefin R-1233zd(E) (1-chloro-3,3,3-trifuoroprop-1-ene). The environmental and thermo-physical properties of this fluid are reviewed, and theoretical thermodynamic efficiency and ORC system calculations are presented for R-1233zd(E) and are compared to HFC-245fa. Thermal stability data for R-1233zd(E) is also presented, along with the results of a high-temperature material compatibility study.
System-search REVERSE ENGINEERING OF FLUID SELECTION FOR ORCs USING CUBIC EQUATIONS OF STATE
Dennis Roskosch, Burak Atakan
Abstract: Fluid selection for thermodynamic cycles like organic Rankine cycles remains an actual topic. Generally the search for a working fluid is based on experimental approaches or on a not very systematic trial and error approach. An alternative theory based reverse engineering approach is proposed and investigated here: The process should start with a model process, designed with respect to the boundary conditions and with (abstract) properties of the fluid needed to fit into this process, best described by some general equation of state and the corresponding fluid-describing parameters. These should be analyzed and optimized with respect to the defined model process, which also has to be optimized simultaneously. The degrees of freedom of the process are restricted to some crucial state variables with variation regimes defined with respect to the boundary conditions like the heat source, heat sink, technical restrictions etc. Knowing the optimal fluid parameters, real fluids can be selected or even synthesized which have fluid defining properties in the optimum regime like critical temperature Tc or ideal gas capacities of heat cp, also allowing to find new working fluids, not considered so far. The number and kind of the fluid-defining parameters is mainly based on the choice of the used equation of state (EOS). In the present work the cubic Peng-Robinson equation was chosen due to its moderate numerical expense, sufficient accuracy and a general availability of the fluid-defining parameters for many compounds. The considered model-process is designed for a typical geothermal heat source with a temperature level of 423.15 K. The objective functions are the thermal efficiency and the net power output relative to the volumetric flow rate at turbine entrance (VSP) as a function of critical pressure pc, Tc, acentric factor and cp. Also, some crucial process variables have to be regarded as a problem variable. The results give clear hints regarding optimal fluid parameters of the analyzed process and deepen the thermodynamic understanding of the process. Finally, for the thermal efficiency optimization a strategy for screening large databases is explained. Several fluids from different substance groups were found to have high thermal efficiencies. These fluids will also have to fulfill further criteria, prior to their usage, but the method appears to be a good base for fluid selection.
System-search STUDY OF RECIPROCATING PUMP FOR SUPERCRITICAL ORC AT FULL AND PART LOAD OPERATION
Arnaud Landelle, Nicolas Tauveron, Philippe Haberschill, Remi Rivelin, Stéphane Colasson
Abstract: Recovery of waste heat in industrial processes is an important component of energy savings worldwide. At low temperature levels, thermodynamics preventss any high efficiency in the heat-to-electricity conversion; such dedicated systems have to be optimized and should achieve a maximum heat recovery, at partial and full load. These technical and technological problematic are also common with renewable natural resources use (solar, geothermal, biomass). Supercritical organic Rankine cycle is quite well investigated in the scientific community, but rarely experimentally studied, especially off-design and dynamic behaviors of such systems. The CEA/LITEN is developing a 10kWe prototypes of supercritical ORC to investigate experimental potential of such technology for low grade power generation. The first task is to characterize various components behavior in supercritical regimes. In such cycles, the pump plays a strategic role, as for supercritical operations the back work ratio is a key parameter to consider. Performance data of a reciprocating pump drive by an induction motor with variable speed drive are measured. Losses are evaluated and a power model is proposed and compared with experimental data. Results of this work aim to give a better knowledge for ORC pump design and optimization.
System-search INVESTIGATION OF A MASSIVE ELECTRICITY STORAGE SYSTEM BY MEANS OF A GEOTHERMAL HEAT TRANSFER PROCESS INVOLVING CO2 TRANSCRITICAL CYCLES
Fadhel Ayachi, Thomas Tartière, Nicolas Tauveron, Stéphane Colasson, Denis Nguyen
Abstract: This work presents a specific application of the Rankine cycle and heat pump technologies: electricity storage. A multi-megawatt thermo-electric energy storage based on thermodynamic cycles is studied as a promising alternative to PSH (Pumped-Storage Hydroelectricity) and CAES (Compressed Air Energy Storage) systems. As a preliminary work, the main objective is to assess the performances of the massive storage technology based on transcritical CO2 heat pump for charging and transcritical CO2 Organic Rankine Cycle for discharging, with power output in the 1-10 MWe range. The general concept of the system is presented, along with its thermodynamic modeling. A parametric analysis is carried out showing that it is possible to reach roundtrip efficiencies up to 53% that are competitive with other technologies. This work also shows the strong dependency between the different parameters of the system, and how an economic optimization will have to take all the subcomponents into account.
System-search AN AUTOMATIC ADJUSTING DEVICE OF THE SPIRAL GROOVE FACE SEAL USED ON ORC TURBINE SHAFT END AND THE ESTABLISHMENT OF CONTROL MODEL
Ya Zheng, Yue Cao, Dongshuai Hu, Xurong Wang, Yiping Dai
Abstract: With the development of high parameter, automation technology, testing and measurement technology, advanced process technology and some related disciplines for the rotating machinery, which promote the research and application of monitoring technology of the spiral groove face seals, the seal system could make real-time response to the change of working parameter. This paper mainly focus on the seal system which is appropriate for the inflammable, explosive, corrosive and toxic substance working medium, and the system must require attaining ‘zero-leakage’, so real-time monitoring the status of seal system is particularly important. This paper proposes a new method to achieve the seal pressure control. Firstly, to get the maximum differential pressure of inlet and outlet which can ensure zero leakage of the seal system in different working parameters through the experiment and numerical simulation. Secondly, to adjust the pressure of feed pump in real time through adjustment of control system when the pressure of sealed medium （the pressure of end face outlet）changes. Consequently, the pressure of end face inlet is adjusted to make the differential pressure of inlet and outlet less than or equal to the maximum differential pressure which can ensure zero leakage of the seal system.
System-search FACTOR ANALYSIS OF INTERNAL EXPANSION RATIO FOR SINGLE SCREW EXPANDERS
Wei Wang, Li-li Shen, Liang Chen, Yuting Wu, Chongfang Ma
Abstract: For low temperature waste heat recovery, Organic Rankine Cycle (ORC) is generally considered the most promising choice in varieties of potential technologies, and become a hotspot of research and development in international academic and industrial fields. However, reviewing the research results related ORC system in recent years, the actual situation was not optimistic. There were many technical bottlenecks hindered the application of ORC, especially for small scale system. Among those problems, the performance of expander was the key issue, and how to improve it was two aspects. First one was improving the shaft efficiency of expander, and it was the common sense of the researchers in this field. Second one was controlling appropriate expansion ratio, and it was special requirement of small scale ORC system. Due to relative small expansion ratio, the thermal efficiency of ORC was low even if high efficiency of expanders. In actual conditions, the high efficiency and expansion ratio of expanders was hardly obtained simultaneously. So, it is necessary to carry out the special discussion about expansion ratio. Single screw expander was a type of volumetric prime mover. Due to special configuration, it had the potential of realized relative high expansion ratio. So, it makes possible getting high thermal efficiency of ORC. In this paper, we tried to analyze the influence factors of internal expansion ratio for single screw expanders. Firstly, the thermodynamic model of ORC was described, and the analysis of expansion ratio influenced cycle thermal efficiency was carried out. From the calculation results, it was found that thermal efficiency was increased with expansion ratio, and the increment speed was to increase rapidly first and then slow down gradually. Considering the actual efficiencies of expander and pumps, appropriate expansion ratio should be existed. Secondly, the analysis of the influence factors of internal expansion ratio for single screw expanders was carried out, from the aspects of configuration, process and condition. From the results, high expansion theoretically could be obtained by changing the configuration of screw and gaterotor, inlet and outlet structure. The maximum volumetric ratio could above 20, and it could completely cover the temperature range of low temperature waste heat recovery. However, in actual condition, different meshing and fit clearances would influence leakage and cause expansion ratio reduced. So, configuration design and clearance control were key issues to improve the expansion ratio of single screw expanders.
System-search IMPLEMENTATION OF A SMALL SCALE ORGANIC RANKINE CYCLE TEST BED SYSTEM USING STEAM AS HEAT SOURCE
Muhammad Usman, Muhammad Imran, Dong Hyun Lee, Byung-Sik Park
Abstract: Organic Rankine cycle based power systems are well known for waste heat recovery application due to their adaptability to follow heat source variations. Industrial exhaust steam has an appreciable potential for the installation of waste heat recovery units. Korea Institute of Energy Research has developed waste heat recovery units which can generate power in the range of hundreds of kilowatts. In order to, rigorously test new cycle configurations and control strategies with least cost for heat source, a small-scale organic Rankine cycle test bed was implemented which a has steam condensing heat exchanger for using steam as a heat source in similar configurations as of larger units. The test bed was equipped with data logging and standalone control system and was configured for the electrical output around 1kW using R245fa as a working fluid. The system is composed of plate type heat exchangers, scroll type expansion machine, screw type working fluid pump and control valves with actuators. This work will present the difficulties, solutions and operational results in terms of design, equipment selection, fabrication and operational experience of system for small-scale power generation with efficiency over 5.2 % for a temperature difference of 120oC. Complexities involved in superheat control of working fluid for the system powered by steam will also be discussed
System-search THERMODYNAMIC STUDY OF INFLECTION POINT OF SATURATED VAPOR CURVE FOR DRY AND ISENTROPIC WORKING FLUIDS
Xinxin Zhang, Congtian Zhang, Jingfu Wang, Maogang He
Abstract: In this paper, the definition of inflection point on saturated vapor curve of dry fluid and isentropic fluid was given according to the shape of the saturated curve of working fluids in a T-s diagram. On this basis, the model of near-critical region triangle was established. Using this model, the effect of inflection point on saturated vapor curve on performance of organic Rankine cycle(ORC) was studied when 38 kinds of dry and isentropic organic working fluids was adopted in ORC. The performance includes relationship between the inflection point temperature and the area of near-critical region triangle, the relationship between the exergy at the inflection point and the area of near-critical region triangle, and the relationship between the area of near-critical region triangle and reciprocal value of slope of saturated vapor curve. On this basis, if the type of heat source is taken into account, the theoretical analysis results show that heptane, cyclohexane, octane, nonane, decane, and dodecane are the suitable working fluids for open-type heat source utilization.
System-search DESIGN AND NUMERICAL ANALYSIS OF PROCESSES IN SILOXANE VAPOR DRIVEN TURBINE
Aleksandr Sebelev, Roland Scharf, Nikolay Zabelin, Maksim Smirnov
Abstract: The problem of decreasing of fossil fuel consumption and energy efficiency is one of today’s major conceptions in the field of energy economics. Waste heat recovery is one of the promising solutions for this problem. One of the ways to increase efficiency of the waste heat recovery process is using siloxanes as working fluids for organic Rankine cycles (ORC). SPbPU scientists have analyzed peculiarities of the steady-state expansion process in the siloxane vapor driven turbine. The design of the nozzle and the blade wheel of the turbine is supersonic due to the low speed of sound of siloxanes. Initial parameters of siloxane were subcritical; a pressure ratio of the turbine was 25. Progressive steps of the initial temperature, pressure ratio and rotational velocity were used to obtain convergence of the solution process. The changings of positions of the nozzle and blade wheel critical sections were established. The details of the supersonic vortices interaction in the blade wheel flow range were analyzed. The efficiency and power output of the investigated turbine stage were estimated as 0.699 and 309.1 kW, respectively.
System-search HIGH-TEMPERATURE SOLAR ORGANIC RANKINE CYCLE – ANNUAL SIMULATION OF VARIOUS SYSTEM DESIGNS
Björn Hunstock, Sabine Strauch, Wilhelm Althaus, Björn Bülten, Johannes Grob, Ralf Paucker
Abstract: This paper deals with the simulation of high-temperature solar organic Rankine cycles. In contrast to previous simulations the diurnal variations and the effect of charging and discharging the thermal energy storage are taken into account. Furthermore, the presented simulations cover one full year. The simulations use discrete time steps with a constant operation over a period of one hour. Considering a full year, 8 760 connected simulations have been carried out to describe the full and part load operation of one plant. Annual simulations allow a detailed evaluation of a solar organic Rankine cycle. The work describes the effect of varying solar field area and thermal energy storage capacity with different design points. High values of irradiance result in small solar fields. These fields often cannot provide enough thermal energy to produce the nominal electrical power at time steps with low irradiance. Design points using a low value for irradiance allow full load operations during the winter season. On the other hand, they generate a large percentage of waste heat during summer, which cannot be used due to limited storage and power capacity. The presented annual simulations show that different design points for a solar organic Rankine cycle cause various results for the plant performance over a full year. A design point in December leads to a large solar field and a thermal energy storage with a high capacity. The annual simulations show the continuous operation over a full year and are used to evaluate the plant designs.
System-search EXPERIMENTAL STUDY ON A LOW TEMPERETATURE ORC UNIT FOR ONBOARD WASTE HEAT RECOVERY FROM MARINE DIESEL ENGINES
Aris - Dimitrios Leontaritis, Platon Pallis, Sotirios Karellas, Aikaterini Papastergiou, Nikolaos Antoniou, Panagiotis Vourliotis, Nikolaos Matthaios Kakalis, George Dimopoulos
Abstract: The aim of this work is the experimental study of an ORC prototype unit which has been designed as a waste heat recovery system for the jacket water of marine diesel auxiliary internal combustion engines (ICEs). In order to simulate the operating characteristics of such engines, the heat input is in the order of 90kWth at low-temperature (90 oC) and is supplied by a natural gas boiler. The ORC unit produces 5 kWel of net electrical power, using as working medium the refrigerant R134a at a design cycle pressure of 25 bar and a temperature of 82 oC. The experimental evaluation of the unit focuses more on operational issues than overall performance which has already been experimentally studied by a number of researchers. Accordingly, this study includes the investigation of the behaviour of the whole ORC system as well as of its key components under varying operational parameters, such as the occurrence of cavitation in the system feed pump and optimal scroll expanders operation. These outcomes contribute to an optimized configuration of the ORC system components and of the necessary measuring equipment as well as to the development of an efficient automatic control strategy of a dedicated ORC test bench which could then be directly coupled to an adequately sized marine auxiliary ICE for real time operation assessment.
System-search REDUCING FUEL CONSUMPTION BY UP TO 10% FOR DIESEL-BASED POWER GENERATION BY APPLYING ORC
Quirijn Eppinga, Jos van Buijtenen
Abstract: A high efficiency Organic Rankine Cycle (ORC) power unit has been developed by Tri-O-Gen B.V. of The Netherlands. The ORC system is based on a thermally stable hydro-carbon as a working fluid, hence suitable for direct use of intermediate temperature heat sources. The unit is capable of transforming heat flows at temperatures between 350 and 600 ºC into electricity. Typical applications involve the exhaust gasses of gas- or diesel engines and small gas turbines. These can be either fuelled by bio-gas, landfill gas, mine gas, or by natural gas as CHP units, where the power-to-heat ratio can be improved considerably. Unit power ranges from 65 to 165 kWe. Generally, the power produced by the ORC is considered as extra (renewable) power. This paper describes the effect of applying this technology to Diesel engine based power generation, by recovering the heat in the exhaust gas and converting it into electricity. Here, the effect is a direct saving on fuel, as the power output is generally a number dictated by the grid. For a given amount of power, the Diesel engine can run in part-load, reducing its fuel consumption by up to 10 % and increasing its life, and also reducing its emissions of CO2 and other harmful constituents. Applications are in decentralized and remote power, where fuel costs are generally high. An economic evaluation will be given, together with some application examples and recent operating experience.
System-search TORQUE RESEARCH OF SINGLE SCREW EXPANDERS
Ruiping Zhi, Yuting Wu, Yeqiang Zhang, Biao Lei, Wei Wang, Guoqiang Li, Chongfang Ma
Abstract: Energy saving is a global problem we commonly face. And ORC(Organic Rankine Cycle) system offers great opportunites. ORC system can capture waste heat from internal combustion engines and industry process discarding heat at low and moderate temperatures, and then converts it to high quality energy(green electricity). And single screw expander as a key component is gaining ever increasing interest in this relative fields due to its unique advantages, including its own rated power(1-200 kW), simple structure, balanced loads, low noise and long service life, etc. Many experiments have been carried out on the performance of single screw expanders in ORC system. W. Wang did some experimental study of single screw expander prototype and stated that the output power has a maximum point with increase of rotational speed. W. He carried out expriements on the performance of the single screw expanders with compressed air as working fluid under different intake pressures and showed that the measured torque has a large increase as the intake pressure increases and has a slight decreases as the rotational speed increases. It is known that the torque of single screw expanders is an important factor that we are more concered about in its design and application. However there are no papers to study the theoretical torque of single screw expander under variable conditions. In this paper, we establish the mathematical model of theoretical torque about single screw expanders, and then develop the MATLAB programming code to get the theoretical results under different conditons such as different diameter of main rotor, different intake pressure and different tooth width of gate rotor. So the aim of this paper is to study the theoretical torque of single screw expanders under variable conditions. By comparation of experimental and theoretical results, we found that the error is in a permissible range. These results acquired here can provide theoretical foundation for estimating the output power of single screw expanders, selecting the type of single screw expanders, and even designing the single screw expanders.
System-search EXPERIMENTAL STUDIES ON AN ORGANIC RANKINE CYCLE (ORC) SYSTEM UNDER VARIABLE CONDENSATION TEMPERATURE
Feibo Xie, Tong Zhu, Jihua Liu, Naiping Gao, Wei An
Abstract: For a thermal power system the operating condensation temperature fluctuates significantly throughout the year in many areas due to the change of ambient temperature. Therafore, off-design operation of an organic Rankine cycle (ORC) system is unavoidable. The present paper focuses on the test and analysis of an ORC system using R123 as the working fluid under various condensation temperature conditions. A scroll expander was integrated into the ORC system and connected with a synchronous generator. The exhaust gas from a furnance and the water from cooling tower were adopted to simulate the low-grade heat source and the cold source,respectively.The temperature of the exhaust gas was about 180°C.With the increasing of the cold water temperature from 22°C to 42°C,the condensation temperature of the working fluid varied from 50 °C to 65 °C and the pressure from 0.21MPa to 0.32MPa, respectively. It affected the expansion ratio and the temperature difference between the inlet and out of the expander, evaporator, condenser, pump and the whole system were influenced subsequently. The measured electric power output declined from 2.36kW to 1.54kW, and the thermal efficiency fell from 7.25% to 5.52% as well. Under the operation conditions, the electric power and thermal efficiency decreased, by34.75% and 23.86%, respectively.These results indicate that the operating condensation temperature plays a key role on the performance of the ORC system, and suggest that a proper condensation temperature is important to the design and operation of the ORC system.
System-search ADVANCED THERMODYNAMIC MODEL OF ORGANIC RANKINE CYCLE
Parsa Mirmobin, Chris Sellers
Abstract: Low-grade heat from geothermal or industrial processes is an eco-friendly resource for electric power production. The Organic Rankine Cycle (ORC) has become a popular means to exploit these energy sources. This growing popularity has resulted in the need for rapid, accurate simulation tools for plant design and specification. In this paper, an advanced, steady state, thermodynamic model of an ORC is developed. The model is composed of several sub components including: a plate evaporator and condenser, centrifugal pump, turbine expander, and pipe elements. Each of these components is modelled independently and their inputs/outputs are combined together to form the overall system loop. The model is developed using simple programming language (VBA) in excel and utilizes NIST Refprop for calculation of state properties. This medium was chosen because of its simplicity and low cost; however, the general model structure can easily be implemented in any programming language. The model predictions are validated against experimental data from an ORC system operated at several evaporating and condensing conditions.
System-search THERMAL EXPANSION AND STRUCTURAL BEHAVIOR OF A CLOSED LOOP THERMAL WIND TUNNEL FOR ORC FLUIDS
Maximilian Passmann, Karsten Hasselmann, Felix Reinker, Stefan aus der Wiesche
Abstract: The Organic Rankine Cycle (ORC) offers great potential for recovering waste heat and using low–temperature sources for power generation. However, the ORC thermal efficiency is limited by the relatively low temperature level, and therefore, designing ORC components with high efficiencies and minimized losses is of major importance. The use of organic fluids creates new challenges for turbine and component design, due to dense gas behavior and the low speed of sound leading to high Mach numbers. Computational fluid dynamics (CFD) offers great potential for design and optimization of ORC components. But the employment of CFD methods requires careful validation by means of experimental data. For ORC components, such an experimental approach requires the use of specially designed wind tunnels for organic vapors. The closed wind tunnel, presented in this contribution, is designed as a pressure vessel system to allow for pressure levels up to p = 10 bars and temperatures up to θ = 180°C. The investigation of heavy weight organic fluid flows at superheated state also needs for higher temperature levels. Heating and cooling units are therefore used to achieve steady state conditions inside of the test section. In this poster contribution the design process of a closed cascade wind tunnel is presented, focusing on the thermal expansion of the system. Thermal finite element method (FEM) analysis is applied to calculate temperature distributions, considering thermal loads and heat losses of the facility. Based on these data, linear FEM analysis is used to investigate thermal stress in the closed loop vessel system. Supporting points and critical zones are assessed in a more detailed analysis. A method to analyse the structure’s transient behavior and to determine allowable heating rates during heat–up phase is presented. The testing facility is part of a large research project aiming at obtaining loss correlations for performance predictions of ORC turbines and processes, which is supported by the German Ministry for Education and Research (BMBF).
System-search ANALYSIS OF PURE FLUID AND ZEOTROPIC MIXTURES UESD IN LOW-TEMPERRATURE REHEATING ORGANIC RANKINE CYCLES FOR POWER GENERATION
Changwei Liu, Tieyu Gao, Jiamin Xu, Jiangnan Zhu, Xun Xu
Abstract: The shortage of fossil energy sources boosts the development and utilization of renewable energy. Among various novel techniques, recovering energy from low-grade heat sources including industrial waste heat, geothermal energy and solar energy through power generation via organic Rankine cycles has been one of the focuses. Compared with basic organic Rankine cycle, reheating organic Rankine cycle includes a high pressure expander and a low pressure expander instead of a single expander, thus the thermal energy can be utilized more sufficiently. Investigations indicated that reheating organic Rankine cycle can improve the thermal performance of the system. In this paper, the cycle performance was mainly measured by the system net output work which was calculated by programming through MATLAB and REFPROP. By taking pure fluid M1 (R245fa) and zeotropic mixtures M2 (R245fa/R152a) and M3 (R245fa/R21) as the cycle working fluid, the influences of working fluid, mixtures component and reheat pressure ratio on low-temperature reheating organic Rankine cycle system were investigated. The results showed that taking zeotropic mixtures as cycle working was superior in the improvement of overall system thermal performance. In addition, the optimal mixtures component and reheat pressure ratio of reheating organic Rankine cycle system were obtained.
System-search STRUCTURE RELIABILITY ANALYSIS OF A NEW FREE PISTON EXPANDER
Gaosheng Li, Hongguang Zhang
Abstract: ABSTRACT A new free piston expander coupled with liner generator (FPE-LG) was proposed, which can be used as a thermo-electric conversion device for organic Rankine cycle (ORC). Compared to other expanders, the free piston expander (FPE) is more suitable for engine exhaust waste heat recovery owing to variable compress ratio and compact-simple structure [1]. A novel inlet/outlet control mechanism was designed for FPE and a FPE-LG prototype was manufactured [2]. In this paper, mechanical structure simulation about valve control mechanism (VCM) of the FPE was carried out, which has a significant impact on the FPE performance. Based on elastic mechanics theory and finite element method, more precise simulation results about stress distribution of the VCM was obtained through transient structural module in Ansys14.5. Subsequently, the FPE was experimentally validated in the air test rig before it is connected into whole ORC system. The results show that the maximal stress is 1.2e6 Pa between sliding block and cam disc in design condition which can be eliminated through heat treatment. The stress on the valve reaches 5.8e8 Pa that exceeded its allowable stress when the FPE worked at input frequent 6Hz. FPE prototype with VCM can realize the suction, expansion and discharge processes properly in the air test rig. The FPE can work stably in a relatively wide range of servo motor input frequency from1Hz~4Hz.The theoretical basis for mechanism performance optimization can provide a good reference value for next generation FPE and further validation of the FPE-LG in the ORC system will be conducted in the near future.
System-search WORKING FLUID SELECTION FOR ORGANIC RANKINE CYCLES BASED ON CONTINUOUS-MOLECULAR TARGETS
Johannes Schilling, Matthias Lampe, Joachim Gross, André Bardow
Abstract: Organic Rankine Cycles (ORCs) use low-temperature heat to generate electrical power. To ensure optimal use of a heat source, the cycle needs to be tailored to the specific application. Tailoring the cycle means optimizing both process and working fluid. This leads to a mixed integer nonlinear program (MINLP) of prohibitive size and complexity. Today, the selection of working fluid and process optimization are typically carried out separately following a two-step approach: In a first step, working fluid candidates are preselected using heuristic knowledge; in the second step, the process is optimized for each preselected working fluid. If the heuristics underlying the preselection fail, the optimal working fluid is excluded and this approach leads to suboptimal solutions. Continuous-molecular targeting (CoMT) is a framework for simultaneous optimization of process and working fluid [1]. Herein, working fluid properties are calculated by a physicallybased thermodynamic model, the perturbed-chain statistical associating fluid theory (PCSAFT) [2]. A set of pure component parameters describes each working fluid. These pure component parameters are relaxed during the simultaneous optimization of process and working fluid. Relaxation transforms the MINLP into a nonlinear program (NLP). The solution is a hypothetical optimal working fluid and the corresponding optimal process. In general, the hypothetical optimal working fluid does not coincide with a real fluid. Thus, real working fluids with similar properties are identified in the following step, the so-called structure mapping. Currently, a Taylor approximation of the objective function around the hypothetical optimal working fluid is used to estimate the objective function value of real working fluids. The Taylor approximation does not account for changes in the active set of constraints, whereby a substantial deviation between the Taylor prediction and the actual performance can occur leading to poor classification of the real working fluids. We present an iterative method to improve the approximation in the structure-mapping. A Taylor approximation is added around a new sampling point if its prediction is poor. The Taylor approximations from different points are combined using inverse distance weighting. The starting point is the optimal hypothetical fluid identified in the simultaneous optimization. The result of the method is a ranked set of working fluids. The iterative method improves the quality of the ranking and allows for efficient identification of the best working fluids. The approach is demonstrated in a case study for working fluid selection of a solar ORC. REFERENCES [1] M. Lampe, M. Stavrou, H. M. Bücker, J. Gross, and A. Bardow, “Simultaneous Optimization of Working Fluid and Process for Organic Rankine Cycles Using PCSAFT,” Ind. Eng. Chem. Res, 53(21): 8821–8830, 2014. [2] J. Gross and G. Sadowski, “Perturbed-Chain SAFT: An Equation of State Based on a Perturbation Theory for Chain Molecules,” Ind. Eng. Chem. Res, 40(4):1244–1260, 2001.
System-search NUMERICAL AND EXPERIMENTAL INVESTIGATION ON THE ROTARY VANE EXPANDER OPERATION IN MICRO ORC SYSTEM
Piotr Kolasinski, Przemyslaw Blasiak
Abstract: Volumetric expanders are nowadays used in micro, small and medium power ORC systems. As it was indicated by Bao and Zhao (2013) most often spiral and screw machines are applied. However, it can be seen that the application of rotary vane expanders is also growing (Tchanche et al. (2011)). Rotary vane expanders are particularly interesting because of the many advantages they have. The most important features of such expanders are: very simple construction; high power in relation to the dimensions; the ability to operate in low inlet pressure and wet gas conditions; low weight; lack of clearance volume; lack of steering valves; possibility to construct an oil-free machines; ease of sealing; the ability to operate at low rotational speeds and a low price. As it was described by Gnutek and Kolasiński (2013) power range of the rotary vane expanders is 0.1—7 kW, thus these machines are particularly interesting for micro and domestic ORC systems. Vane expanders used in ORC systems are very similar to these commonly used in pneumatic systems, however, it is necessary to carry out the appropriate adaptation of the machine. This includes special hermetic sealing, lubrication and cooling. As a part of the research works on ORC power systems with vane expanders conducted by the authors on Wrocław University of Technology a research test-stand (comprehensively described by Gnutek and Kolasiński (2013)) was designed and realized. This micro power, R123 based, ORC prototype enables experimental analysis of the vane expander operation under different conditions. In this article authors present the results of numerical simulation of vane expander operation in ORC prototype and compared them with the results of experiment. 3D model of the expander was built and analyzed in ANSYS CFX based on the geometrical data obtained by complete disassembly of the machine. The numerical analysis included the same, as in the case of the experiment, expander operating conditions, i.e. pressure, temperature and R123 flow rate at the inlet and outlet of the expander.
System-search THE METHOD OF THE WORKING FLUID SELECTION FOR ORGANIC RANKINE CYCLE (ORC) SYSTEM WITH VOLUMETRIC EXPANDER
Piotr Kolasinski
Abstract: Volumetric expanders are nowadays used in micro, small and medium power ORC systems. Tchanche (2011) indicated that most often spiral, screw and the rotary vane machines are applied. Volumetric machines have a number of specific features determining their operation. The most important are: the possibility of building expanders for small and very small capacities; small and moderate frequency of operating cycle - allowing for consideration of the processes taking place in the machine as a quasi-static; the ability to operate at high pressure drops in a single stage and ease of the hermetic sealing. The most important feature of the volumetric expander operation is the relationship of the expander power and the expansion ratio (the ratio of the inlet and outlet pressure). Each type of volumetric expander also has the optimum value of the expansion ratio. Unlike the turbines, volumetric expanders can operate at low working fluid flow rates and lower pressures. Thus, it is possible to apply volumetric expanders in ORCs powered by low-temperature heat sources, such as e.g. domestic waste heat. The task of a suitable working fluid selection to the ORC system with volumetric expander should be considered differently than in the case of the turbine-based systems. It is caused by low thermal parameters of the cycle and indicated earlier volumetric expander characteristic features. In this paper a new method of the working fluid selection to the ORC system working with volumetric expander was presented. The method is based on the dimensionless parameters useful for the comparative analysis of different working fluids. Dimensionless parameters were defined for selected thermal properties of the working fluids, namely the ability of heat absorption from the heat source, heat removal, mean temperature of the heat supply and the efficiency of the energy conversion. These comparative parameters were calculated for selected low-boiling ORC working fluids and selected temperature of the heat source and the heat sink. Basing on the values of these parameters the working fluids comparison was presented and applicable working fluids were selected.
System-search THERMODYNAMIC AND DESIGN CONSIDERATION OF A MULTISTAGE AXIAL ORC TURBINE FOR COMBINED APPLICATION WITH A 2 MW CLASS GAS TURBINE FOR DEZENTRALIZED AND INDUSTRIAL USAGE
René Braun, Karsten Kusterer, Kristof Weidtmann, Dieter Bohn
Abstract: The continuous growth of the part of renewable energy resources within the future mixture of energy supply leads to a trend of concepts for decentralized and flexible power generation. The raising portion of solar and wind energy, as an example, requires intelligent decentralized and flexible solutions to ensure a stable grid and a sustainable power generation. A significant role within those future decentralized and flexible power generation concepts might be taken over by small to medium sized gas turbines. Gas turbines can be operated within a large range of load and within a small reaction time of the system. Further, the choice of fuel, burned within the gas turbine, is flexible (e.g. hydrogen or hydrogen-natural gas mixtures). Nevertheless, the efficiency of a simple gas turbine cycle, depending on its size, varies from 25% to 30%. To increase the cycle efficiencies, the gas turbine cycle itself can be upgraded by implementation of a compressor interstage cooling and/or a recuperator, as examples. Those applications are cost intensive and technically not easy to handle in many applications. Another possibility to increase the cycle efficiency is the combined operation with bottoming cycles. Usually a water-steam cycle is applied as bottoming cycle, which uses the waste heat within the exhaust gas of the gas turbine. In small to mid-sized gas turbines the temperature and heat amount within the exhaust gas are often not sufficient to operate a water steam cycle efficiently. Further, in industrial applications, a part of the heat, within the exhaust gas, is often used in secondary processes which lower the total amount of heat, which can be transferred to a bottoming cycle. An alternative to water-steam bottoming cycles can be given by organic Rankine cycles (ORC) based on organic fluids. An advantage of organic fluids is the characteristic of evaporating at lower temperatures and lower heat amounts and thus, the usability in a Rankine cycle even at low heat source temperatures. This paper discusses an ORC process design for a combined application with a simple cycle gas turbine in the 2 MW class. The thermodynamic cycle configuration is shown and it will be pointed out that the cycle efficiency (simple GT) of 26.3% can be increased to more than 36% by application of a bottoming ORC cycle (simple GT+ORC). A key component within the ORC cycle is the turbine. This paper shows the results of an extended aerodynamic ORC axial turbine pre-design based on the thermodynamic cycle considerations. Within the design study the real gas properties of the organic fluid are taken into account. Based on the outcome of the pre-design a 3D aerodynamic axial turbine design is investigated. By application of CFD simulations the turbine design has been optimized and the ORC power output could be increased from 598kW (pre-design) to 657 kW, which lead to a combined cycle efficiency of more than 36%.
System-search CONTROL STRATEGIES FOR AUTOMOTIVE RANKINE SYSTEM EVALUATION USING A COSIMULATION PLATFORM
Abdelmajid Taklanti, Jin-Ming Liu, Régine Haller
Abstract: Today, several solutions to recover wasted heat in automotive power train are considered and evaluated in order to reduce vehicle fuel consumption and to meet new emission regulation targets (El Habachi et al. (2010), Abbe Horst et al. (2014), Domingues et al. (2013) and Haller et al. (2014)). One of the solutions is to use Organic Rankine Cycle to recover waste heat from engine cooling system and/or engine exhaust gas and transform it to mechanical or electrical power. Automotive environment is very severe and very transient, the key point for operating such system is to set up and validate a suitable control strategy to maximize the recovered output power. In automotive industry development processes the control strategies are mainly described in a control tool environment. Commonly, the control is then tested and the control parameters are set up using physical mockups and prototypes of the studied system on a test bench. Afterwards the control is coded into a control unit and integrated in a vehicle or a demo-car in order to validate and tune up the control strategies and parameters. This process is very long and time consuming because physical prototype and demo-car are needed. In this paper, we are going to present a methodology using a virtual model of a R134a low temperature Rankine system integrated in a vehicle platform developed in a system simulation tool environment and coupled to a Rankine control system developed in a control tool environment. This methodology and co-simulation (see Taklanti et al., 2013) allow us to test and evaluate different control strategies, to select the optimal one and to set up control parameters prior to physical mockup or demo car availability. Finally, some results are presented showing the performance of a low temperature R134a Rankine system in a vehicle environment and the performance of a control strategy for constant velocities and transient driving cycles.
System-search PVT PROPERTIES AND VAPOR PRESSURES OF HFO-1336MZZ(E)
Katsuyuki Tanaka, Ryo Akasaka, Eiichi Sakaue
Abstract: Experimental data of PVT properties and vapor pressures are presented for trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(E)). HFO-1336mzz(E) can be an alternative for conventional working fluids. However, reliable property information on the refrigerant is scarce at this time. This work performed measurements of the PVT properties at temperatures from 323 K to 443 K and pressures up to 10 MPa, including supercritical region. An isochoric method was employed with a constant volume cell designed for operation at high temperatures and high pressures. The critical temperature, pressure, and density were estimated from the PVT properties in the critical region. The saturation properties were also obtained.
System-search ORC-DEMONSTRATION-PLANT WITH 1 KW SCROLL EXPANDER - DESIGN AND OPERATIONAL EXPERIENCES
Albrecht Eicke, Slawomir Smolen
Abstract: Within the framework of many projects and activities in the JRM-Institute and Laboratory for Energy Engineering at the University of Applied Sciences in Bremen, several practical and theoretical aspects of energy transformation using Organic-Rankine-Cycle have been investigated. The prior activities focused on two general optimization and designing tasks. A special procedure and program has been elaborated and developed in the area of universal theoretical analysis, which facilitates working fluid selection in Organic Rankine Cycle for waste energy recovery from potential low and medium temperature level sources. An essential part of the program is a wide range database of organic fluids and the elaborated tool should create a support by choosing an optimal working fluid for special applications and become a part of a bigger optimization procedure by different boundary conditions. The second main task is more practical and corresponds to the particular two-stage ORC-installation concept for waste heat recovery from combustion engines - especially from gas motors of biogas plant. Relating to the theoretical concept a special test bench has been developed and assembled in our laboratory. The main goal of this installation is testing the operation of expansion machines, especially screw engines. In this paper the current project – an ORC demonstration and test plant with an oil free expander - will be presented. The core of the micro power plant is a scroll-expander with a nominal power of 1 kW (Air Squared Inc., E15H22N4.25). In the future the installation will be coupled to solar collectors, which will provide the heat to keep the ORC process running. Alternatively the heat can be generated by an electric driven thermal heater rated at a nominal power of 17 kW to demonstrate the functionality of the ORC itself without using solar energy. Disregarding the source of the heat, it is transmitted by two plate heat exchangers to the working fluid (R245fa). This process ensures a complete vaporization of the working fluid and overheats it to a temperature of 115 °C at a pressure of 1,38 MPa. To simulate a working load, 15 halogen lamps with a nominal power of 100 W each are integrated in the system. The extensive measurement instrumentation will be able to evaluate the entire process and the components used for the installation, especially the effectiveness of the expansion device. REFERENCES [1] Hung, T.C., Shai, T. Y., Wang, S. K., A review of Organic Rankine Cycles (ORCs) for the recovery of low-grade waste heat, Energy, Vol. 22, No. 7, 1997, pp. 661 – 667. [2] Eicke, A., Smolen, S.: Screw Engine as Expansion Machine Applied in an ORC-Test-Installation – Lubrication System for a Screw Machine in Reverse Rotation, VDI-Berichte (Energy and Environment), International Conference on Screw Machines, TU Dortmund University - 2014, ISSN 0083-5560, ISBN 978-3-18-092228-7 [3] Smolen, S., Bandean, D.: Working Fluid Selection for Organic Rankine Cycle Applied to Heat Recovery Systems, WREC, World Renewable Energy Congress 2011, Sweden, Linköping, May 2011, www.wrec2011.com
System-search DIESEL ENGINE WASTE HEAT HARNESSING ORC DEVICE
Jovana Radulovic
Abstract: Use of ORC in waste heat recovery is widely seen as a viable and promising solution for increasing energy efficiency and emission reduction efforts. Recently, several of “on-board” vehicular applications have been patented and further development of similar systems is on-going [1]. Along attempts to control the costs, the quest for a safe and justifiable choice of a working fluid with appropriate thermodynamic performance continues. Flammability and toxicity are of primary concern, especially when exhaust heat is utilised, and further environmental issues may arise. Component design, size and costing are also under scrutiny. Superiority of mixtures over pure fluids has been documented in the literature. Zeotropic mixtures in particular are an attractive choice, as they provide a better thermal match due to the temperature glide they exhibit. A mixture can also offer improved thermodynamic behaviour, such as lower exergy destruction and extended temperature range [2]. We have studied use of several organic fluids in bottoming ORC systems in diesel-powered vehicles [3] and we are expanding our approach to diesel generators. Both pure fluids and their mixtures were considered, and their advantages and drawbacks were identified. Cycle operational parameters were optimised to allow for safe device operation while achieving satisfactory outputs. Selected working fluids were compared in terms of thermal and exergy efficiency as well as the required turbine size and power produced. In addition to fluid selection our approach is focused on design and safety elements compatible with common diesel generators. We comment on applicability of high-temperature working fluids, which diesel exhaust can thermally support, whilst taking in account practical risks associated with the use of flammable and toxic substances, as well as fluid stability, material compatibility and size limitations. REFERENCES 1. Capata, R. and C. Toro, Feasibility analysis of a small-scale ORC energy recovery system for vehicular application. Energy Conversion and Management, 2014. 86(0): p. 1078-1090. 2. Radulovic, J. and N.I. Beleno Castaneda, On the potential of zeotropic mixtures in supercritical ORC powered by geothermal energy source. Energy Conversion and Management, 2014. 88(0): p. 365-371. 3. Koelsch, B. and J. Radulovic, Utilisation of Diesel Engine Waste Heat by Organic Rankine Cycle. Applied Thermal Engineering, article in press.
System-search SMALL SCALE ORC DESIGN FOR A COGENERATION SOLAR BIOMASS SUPORTED APPLICATION
Joaquín Navarro-Esbrí, Francisco Molés, Bernardo Peris, Adrián Mota-Babiloni
Abstract: Due to environmental constrains, Combined Heat and Power (CHP) systems and bottoming power cycles for waste heat recovery have received considerable attention over the past decades. Among the several proposed power cycles, the Organic Rankine Cycle (ORC) has been attracting increasing attention. ORCs have been proved as a feasible technology for low temperature (< 250 ºC) and small scale (< 1 MWe) applications, as converting renewable energy into heat and power [1]. The aim of this work is to present the design process of a small scale ORC, suitable for a Combined Cold, Heat and Power (CCHP) application that use solar biomass supported renewable energy as heat source [2]. The ORC module has to be designed in order to work in cogeneration mode and power only generation mode. The first part of the paper deals with the preliminary design of the ORC module, including working fluid and configuration selection, from the technical requirements of the equipment imposed by the application. The operating conditions have been selected in order to maximize the efficiency of the system. In the second part of the paper, an expander has been proposed and characterized. The experimental results from the expander have been used in order to predict the expected behaviour of the ORC module. The performance of the cogeneration system, producing hot water at 70ºC, is summarized.
System-search CONSTRUCTION AND PRELIMINARY TEST OF AN ORGANIC RANKINE CYCLE (ORC) USING R245FA AND SINGLE SCREW EXPANDER
Biao Lei, Yuting Wu, Wei Wang, Chongfang Ma
Abstract: Organic Ranking Cycle (ORC) is one of the most promising methods for converting low-grade heat into power. In this paper, an experimental ORC system, which includes a single screw expander, a shell and tube evaporator, an air-cooled fin-and-tube condenser and a metering pump, has been built. R245fa was adopted as the working fluid considering of its good performance and environmentally-friendly characteristics. The heat source of the experimental system is the conduction oil which was heated by electricity. In the evaporator of the system, R245fa was evaporated into vapor by the high-temperature conduction oil. Experiments were conducted to analyze the operational characteristics and performance of the developed ORC. The key parameters of the ORC, such as the efficiency of the cycle and the expander, were obtained. In addition, the factors which influence the performances of the developed ORC were analyzed and discussed.
System-search DESIGN AND ANALYSIS OF AN ORGANIC RANKINE CYCLE SYSTEM FOR COGENERATION
Peter Collings, Zhibin Yu
Abstract: This paper covers the design and construction of a small scale prototype of Organic Rankine Cycle (ORC) system for domestic-scale cogeneration application, using a variety of working fluids. The efficiency of such systems is limited by the low temperature range available to them. Researches indicate a first law efficiency of up to 11% for such ORC system for a heat source temperature less 250 degree Celsius, meaning that a large proportion of the heat used to drive them is rejected to the environment. This makes them ideal candidates for micro-scale Combined Heat and Power projects producing up to 10kW of electricity. This research aims to investigate the effects of varying several cycle parameters, as the thermal efficiency of a cycle operating in such a limited temperature range is quite low, and even small absolute gains can represent large percentage increases in efficiency, and correspondingly, small decreases in efficiency due to conflicting optimisation demands can be very costly. In particular, the effect that the selection of the working fluid has on the performance of the cycle is investigated, but also the operating pressures of the system, the temperatures at each point in the cycle, the presence or lack of a regenerator, and the flow rates of the working fluid, heating, and cooling water. The ultimate goal is to develop a system configuration that produces the most electrical power while still providing an acceptable final temperature of coolant to be used for space heating. Initially, simulation work was carried out using MATLAB, linked to the REFPROP 9.1 fluid properties program. The results of this program were used to design a lab-scale prototype ORC system, built around a 1kW scroll expander from Airsquared, which will be used to validate the model, and gather experimental data to complement the theoretical predictions.
System-search ON THE OPTIMUM AXIAL FLOW TURBINE DESIGN IN ORGANIC RANKINE CYCLES
Luca Da Lio, Giovanni Manente, Andrea Lazzaretto
Abstract: Organic Rankine Cycles (ORCs) can effectively recover low grade heat for electricity production from industrial wastes and renewable energy. The general design problem of an ORC system is not trivial due to the choice of several design variables related to the thermodynamic cycle and equipment. Most of the optimization studies in the literature search for the optimum cycle configuration, design parameters and working fluid, disregarding the influence of these choices on expander design and efficiency. Indeed, the latter is often fixed to a constant value implicitly assuming that it will be achieved by a proper expander design in a subsequent design phase. This approach may be weak especially for the working fluids operating in ORCs having a high molecular weight and a low speed of sound. In these applications the high volumetric expansion ratios which may occur even at small temperature differences between turbine inlet and outlet markedly decrease the expander efficiency. Moreover, this efficiency is strongly affected by expander size that may vary from only few kWs up to several MWs. The aim of this study consists in searching for the optimum axial flow turbine design parameters (so called duty parameters) in a wide range of ORC operating conditions. Flow coefficient, loading coefficient and degree of reaction are selected as input values in a mean line design procedure that generates the main turbine geometrical characteristics and evaluates the turbine efficiency according to recent loss correlations. The variation of turbine efficiency with duty parameters is then shown in efficiency charts (like the Smith’s one) to highlight suboptimal design options. This procedure is repeated for a range of ORC duty specifications (mass flow rate and expansion ratio) to detect their influence on turbine efficiency. So, any penalty associated with the selection of non-optimum duty parameters is clearly separated from the efficiency decay deriving from more severe operating conditions (e.g., high expansion ratios and small sizes).
System-search ORC APPLICATIONS FROM LOW GRADE HEAT SOURCES
Bernardo Peris, Joaquín Navarro-Esbrí, Francisco Molés, Adrián Mota-Babiloni
Abstract: The Organic Rankine Cycle (ORC) has been proven as an efficient way to benefit from low grade heat sources, with a great interest in waste heat recovery and use of renewable heat sources. In this way, this work deals about three different applications implemented in Spain. The first application consists of a power only system for industrial waste heat recovery. The system takes advantage from the exhaust air of a ceramic furnace to produce a rated electrical power of 20 kW [1]. The second application is a Combined Heat and Power (CHP) system integrated as a bottoming power cycle of an Internal Combustion Engine (ICE), with the purpose to recover waste heat from exhaust gases. This system is installed in a hospital to increase the ICE electrical production and generate hot water up to 90 ºC [2]. The third application can operate producing both power only and CHP. The ORC module is used to profit thermal energy from a biomass supported solar thermal system and produce a maximum electrical power about 6 kW and hot water above 80 ºC [3]. Thereby, these applications are addressed in this paper. Moreover, focusing on the ORC modules performance, experimental data obtained from tests developed under different operating conditions, that correspond to low grade heat sources, are analyzed and discussed.
System-search TESTING AND MODELING A VANE EXPANDER USED IN AN ORC WORKING WITH HEXAMETHYLDISILOXANE (MM)
Vaclav Vodicka, Ludovic Guillaume, Jakub Mascuch, Vincent Lemort
Abstract: Waste heat from industrial production carries considerable potential for further use. Organic Rankine Cycle (ORC) brings a possibility to produce electrical energy from heat, originally intended to release to the surroundings. For ORC with power output up to 10 kW, small-scale turbines are still expensive to manufacture and their use can be problematic in terms of high shaft speed or quality of inlet steam. It is therefore preferable to use positive displacement expanders. The first part of this paper presents and analyses the measurements conducted on a prototype of vane expander. This vane expander characterized by a 1 kW power output operates in an ORC that uses hexamethyldisiloxane as a working fluid. The expander inlet temperature varies approximately from 135 °C to 150 °C, inlet pressure varies approximately from 200 to 300 kPa abs, isentropic efficiency from 0,4 to 0,58. The second part of the paper proposes a grey-box model, which is calibrated on the base of the measured data. This lumped-parameter model takes into consideration major losses of the expander: supply and discharge pressure losses, under and over-expansion, internal leakages and mechanical losses. The model is finally used to assess the impact of each source of losses on the overall performance of the expander.
System-search EFFECT OF WORKING FLUID MIXTURE COMPOSITION ON THE PERFORMANCE OF AN ORGANIC RANKINE CYCLE
Peter Collings, Zhibin Yu
Abstract: Whereas single-component working fluids exhibit phase changes at a constant temperature, working fluid mixtures containing two or more components can exhibit a change in temperature across a phase change, known as “glide”. These fluid mixtures are termed “zeotropic”. Zeotropic mixtures can possess several advantages when used as working fluids in ORC systems. Similarly to supercritical cycles, they can match the temperature profiles on the hot and cold sides of the evaporator, resulting in less of a need for superheating, and increasing second law efficiency. The major advantage of a zeotropic fluid over a supercritical one is that this effect can also be felt in the condenser, which can greatly reduce the need for coolant for a given cycle efficiency. This is of particular benefit in desert areas, where cooling water is not readily available. In general, zeotropic cycles can be made to exhibit significant temperature glide at far lower pressures than an equivalent supercritical cycle. A temperature glide can also result in a greater amount of energy being transferred in a recuperator, should one be included in the system, by increasing the difference in temperature between the cold fluid leaving the pump, and the hot fluid leaving the expander, which results in a greater transfer of energy for a given cycle configuration, especially when this enables a certain amount of phase change to occur in the recuperator. This paper uses a numerical simulation in MATLAB to analyse the effects of varying the composition of a zeotropic mixture of R245fa and R134a on the overall performance of a cycle, both with and without a recuperator installed.
System-search EVALUATION OF ORC USING LOW GWP WORKING FLUIDS FOR WASTE HEATS
Osamu Furuya, Eiichi Sakaue
Abstract: Ironworks have various furnaces and have been exhausting waste heats of various temperatures. Though waste heats of more than 250℃ have already been utilized for electricity and heat recuperations, that of lower than 200℃ have not been effectively utilized yet. For 40 years, electric power generation system using organic working fluid has been commercialized for the geothermal hot water of lower than 200℃ in geothermal power plants. But due to environmental problems of organic working fluids, electric power generation system using organic working fluid has not been applied in the lower waste heats. Organic working fluid’s problems for commercial application are toxicity, flammability, ozone depletion and global warming potential (GWP). Recently, in respect of climate change, low GWP working fluids have been paid attention and developed. Some are being released into market. The low GWP working fluids are more degradable in high atmosphere and have shorter lifetime than existing organic working fluid such as R134a and R245fa and less flammability than flammable working fluid such as pentane, butane, propane due to its molecule structure. In this study, to design ORC system using low GWP working for waste heat of lower temperature, various kinds of thermal properties of those low GWP have been evaluated using publicized reliable database, for the first step. Also other properties such as stability, productivity and economics are evaluated to find out effective low GWP working fluids. As the second step, power generation efficiency for waste gas of lower than 200℃ using low GWP working fluids such as R1234ze(E) and R1233zd(E) was evaluated compared with conventional ones. Various power generation system types are evaluated such as subcritical Rankine cycle, supercritical Rankine cycle and recuperated Rankine cycle, based on depending on critical temperature of working fluids and turbine outlet gas superheated temperature. Evaluations also take into accounts following factors, such as turbine efficiency, working fluid pump efficiency, generator efficiency, pinch-point temperature difference and pressure loss of heat recovery heat exchanger, condenser, recuperator, and pipe pressure loss. Since, expected power generation output is more than 1MW, and turbine inlet pressure is more than 1MPa, multi-stage axial is picked up as turbine type. As the result, power generation gross efficiency and net efficiency are estimated and heat exchangers scales are determined by basic designation.
System-search COMPARATIVE STUDY OF ORGANIC RANKINE CYCLE(ORC) FOR LOW GRADE ENERGY IN TURBINE AND PAT METHOD WITH FLUID
Farzam Alimardani, Mohammadreza Rostamzadeh
Abstract: In this paper, the organic fluid open Rankine cycle is analyzed when the variable expander is common assumption. The cycle arrangement in this plan is semi-open that is the layout is as a semi-cycle and the exhaust gas is directed to a drain tank. The effect of various parameters such as the inlet pressure on the expander, inlet temperature, pressure limit, injection rate on the thermal efficiency, the second law efficiency is measured and energy conversion to work is done with laboratory fixed effects. The highlighted characteristic in this study is the source serviceability capability in low-temperature and introduction of different blades as expander and its using to determine different organic fluids serviceability. This study shows that to what extent is the efficiency of the organic serviceable liquid R11, R22, R134a and how is each relation with the critical temperature and the impact of various changes on the cycle will be displayed and changes in temperature and flow rate, pressure and weights change will be analyzed and in the next stage expander replacement effect on results process will be shown. But what is important for us in this study project is to get work from lower temperature source, today’s using water is used as fluid as the main and original factor in powers with high costs to raise the water temperature to and using low temperature energy sources as the new energy for the future has importance and should be studied.
System-search EFFECT OF RADIAL HEAT TRANSFER IN THE PEBBLE BED THERMAL ENERGY STORAGE TANK COUPLED TO A SOLAR ORGANIC RANKINE CYCLE
Pardeep Garg, Abhishek Kshirsagar, Pramod Kumar, Matthew Orosz
Abstract: Organic Rankine cycle is an efficient and a scalable technology to convert low temperature heat into electricity available from a number of heat sources like geothermal or waste heat from industrial processes or low concentration solar collector systems. The nature of the above mentioned heat sources can be different from one another, wherein some of these can be expected to yield continuous and constant power supply while, others such as concentrated solar systems are bound to have fluctuations. In such cases, a thermal energy storage (TES) system can be used to suppress the effect of fluctuations and also if needed to generate power during non-solar hours. Presently, there are a number of storage options available, for example one tank or two tank technology with heat storage media as pure heat transfer fluid (HTF). One tank technology definitely has the cost advantage factor; but to reduce the cost further, pebble bed systems are used, wherein a fraction of heat is stored in the pebbles depending upon the void fraction of the bed. This paper analyzes the heat transfer mechanisms in the pebble-bed storage medium and reports the issues associated with it. A case study is performed considering the storage requirements for an R-134a ORC operating between 150 °C and 45 °C with a cycle efficiency of 10 %. A100 kWe system is analyzed to mitigate the diurnal fluctuations in direct normal insolation (DNI) using propylene glycol as the HTF. DNI is calculated for a typical day of vernal equinox on the tropic of Cancer, which approximately represents the mean of Indian latitude. Variation in DNI is recorded using ASHRAE clear sky model for single axis tracking in case of parabolic collectors. A cylindrical geometry is considered for the TES tank in the present analysis. TESs reported in the literature use a central inlet and outlet configurations which are prone to have thermally isolated regions in the extreme corners. The theoretical models and procedures developed for these system do not capture radial effects of heat transfer. Though, ideally it is desirable to have no radial effects on heat transfer in order to maximize the energy storage capacity, may often not be practically realizable. In this regard, governing equations considering the 3-dimensional geometry need to be solved to account for radial effects. This is achieved by modeling the fluid flow in TES using a CFD tools. Three geometrical configurations are modeled using a commercial solver, Fluent 6.0, ANSYS for various cases of inlet and outlet port positions a) central inlet and outlet, b) uniform inlet and uniform outlet and c) diametrically opposite inlet and outlet ports on the lateral surface of the cylindrical TES tank. In case of central inlet and outlet, formation of thermally isolated corners is observed in the extreme corners of the geometry. Theoretically, temperature at the outlet of the TES is supposed to be steady; however, CFD results reveal that high temperature fluid is discharged from the TES system after a 20% of the charging cycle. These issues are found to be absent for the case of uniform inlet and outlet configuration, which often is difficult to practically realize. Therefore, a new configuration is proposed by placing the inlet and outlet ports at extreme ends to mitigate the above issues, the details of which are provided in the paper.
System-search THERMO-ECONOMIC ANALYSIS OF A MIXTURE OF RC-318 AND PENTANE AS WORKING FLUID IN A HIGH TEMPERATURE SOLAR ORC
Ankit Saini, Karthik G.M., Pardeep Garg, N.C. Thirumalai, Pramod Kumar, Vinod Srinivasan
Abstract: Organic Rankine Cycle (ORC) technology is well-documented to be economically viable when integrated with cheap heat sources such as geothermal or waste heat recovery. However, when coupled to a solar field, the same ORC is found to be expensive for each unit of electricity generated. This is because the solar collectors, generally parabolic troughs, used in these low temperature (< 150 °C) cycles are directly adopted from steam based solar Rankine cycles operating at ~ 300 °C. The solar field cost associated with ORCs for the same power generation can be brought down by increasing its maximum temperature and hence cycle efficiency. This motivates the thought to explore the possibilities of high temperature solar based ORCs which in theory have the potential to be more economically viable. Further, these high temperature ORCs can be compared to the steam based solar Rankine cycle where the operating boundaries (maximum and minimum cycle temperatures) are more likely to be identical. In literature so far, high temperature ORCs have not been explored in a great depth. Herein, we investigate working fluids suitable for high temperature ORCs for solar applications which yield higher cycle efficiencies and have the potential of realizing lower initial cost. This paper aims to compare the cost of the power block (measured in $) per unit of electricity generated (measured in We) for a high-temperature ORC with that of a steam based Rankine cycle operating under identical conditions. The analysis considers a 10,000 m2 solar field area that supplies heat to a power block for a location at the Tropic of Cancer which is roughly the mean of Indian extreme latitudes. Such a solar field ensures an averaged supply of 4 MWth for 12 solar hours on a Vernal equinox day. Hot heat transfer fluid (HTF) from this solar field is stored in a pebble based thermal storage tank. This ensures a steady heat input to the working fluid in the power cycle which is either a regenerative ORC or a steam Rankine cycle. The thermodynamic model developed herein is realistic since it accounts for the inevitable irreversibilities in various components. Design of heat exchangers and condenser is based on the standards followed in industry and is then coupled to the economic model wherein various components are modeled as per their respective capacities. NIST REFPROP database is exhaustively searched and 20 fluids are shortlisted based on the criteria of having positive condenser pressure (at 45 °C) and zero ozone depletion potential (ODP). The fluids are further scrutinized considering their thermal stabilities at 300 ºC. Those stable at 300 °C are either flammable (propane, butane) or have a very high GWP (RC-318). However, the mixture of propane and RC-318 (30 and 70 % on molar basis) is observed to overcome the demerits of the individual components and helps in achieving the possibility of having an organic fluid stable up to 350 °C. Subsequently, a thermodynamic analysis is performed which predicts that the efficiency of the steam cycle is ~ 2 % higher than that of the mixture based ORC. However, economic evaluation of both the cycles suggests that the mixture based cycle cost can be ~ 40 % lesser than the steam based cycle cost because of lower volumetric flow rates in the former resulting in a more compact power block and lower initial investment. Finally, both the cycles are compared on the parameter of $/We for solar applications which for the mixture based ORC is found to be 15 % lesser.
System-search STUDY ON LABYRINTH SEAL AT THE HIGH-PRESSURE SIDE OF THE SCREW IN SINGLE SCREW EXPANDER
Guoqiang Li, Yuting Wu, Ruiping Zhi, Yeqiang Zhang, Chongfang Ma
Abstract: Single-screw expander can be used in small scale ORC power system in which the output power is from 1 to 500 kW. There are many advantages of single screw expander, such as long working life, balanced loading of the screw, high volumetric efficiency, low noise, low leakage, low vibration and simple configuration. However, reliable seal is required at the high-pressure side of the screw for single screw expander. Labyrinth seal is a widely used seal method in the scope of industry. It is characterized by simple structure, well-adapted, great stabilization, long lifetime and convenient maintenance. It is widely used to seal compressors, steam turbines, gas turbines and blowing plants. Therefore it is very promising that single screw expander adopts labyrinth seal to get well sealing at high-pressure side of the screw. In this paper, several models were built, and then numerical simulation was conducted. Sequentially, the operating principles of labyrinth seal were analysed according to the simulation results. In addition, the influences of the labyrinth seal parameters, such as types of organic working fluids, pressures at inlet and outlet, size of clearance (length & width), tooth width, tooth height, tooth distance, number of teeth, and angle of inclination, were studied.
System-search EFFICENCY OF THE ARCHISOL CONCEPT
Harold Lever, Edo Wissink
Abstract: A simplified ORC cycle is proposed for small temperature differences. The most important simplification is the replacement of the pump section by a a hydraulic column. The weight difference between the downward moving liquid column and the upward moving gas column provides the driving pressure for the cycle. Especially for Ocean Thermal Energy Conversion applications, it is expected to be an advantage that less mechanical components are necessary for the cycle.
System-search EXPERIMENTAL SETUP OF A SMALL SUPERSONIC TURBINE FOR AN AUTOMOBILE ORC APPLICATION RUNNING WITH ETHANOL
Harald Kunte, Jörg Seume
Abstract: A significant part of the global emissions of greenhouse gases is caused by road traffic. Therefore, automobile manufacturers are in search of opportunities to decrease these emissions by increasing the efficiency of combustion engines. The analysis of the energy flows in such combustion engines showed that a considerable part of the inserted chemical energy is lost as thermal energy in the exhaust gas. Prior investigations have shown that an Organic Rankine Cycle (ORC) is convenient to recover some of this energy. Within these ORCs, ethanol promises to be a suitable working fluid for this application. But the efficiency of the whole ORC is significantly dependent on the efficiency of the expansion machine. On this account, it is necessary to develop suitable expansion machines for such ORCs. At the Institute of Turbomachinery and Fluid Dynamics (TFD) an axial turbine was developed to prove that an efficient operation is possible. But the boundary conditions are quite challenging for a turbine. Firstly, the ORC requests a high pressure ratio to maximize the power output. Secondly, the small amount of thermal energy in the exhaust gas causes low mass flows. The single stage design promises a compact prototype and reduced manufacturing costs. But this also leads to a supersonic flow velocity in the turbine. Special blade shapes are used to achieve an efficient operation of the turbine. Additionally, the small mass flows cause a small turbine diameter and a very high rotational speed. The target, a compact expansion machine, requires the mounting of the turbine rotor and the generator rotor on one shaft. This requires the utilization of a high speed generator, which can handle the rotational speed. The prototype of such a machine was manufactured at the TFD for an experimental investigation. Firstly, the experiments shall confirm that a turbine is suitable for the automobile ORC-application and achieves the predicted performance. Secondly, the feasibility of the turbine-generator design should be demonstrated. The experiments will be performed at a test bench of the University Hannover. This test bench is able to provide vaporous ethanol at the requested pressure level, for a safe operation of the expansion machine. The poster gives an overview of the planned experiments and the setup. This contains detailed description of the prototype itself. The accurate measurement of the operation conditions is challenging, because several loss mechanisms occur. Therefore several measurement points are implemented to get an accurate measurement of the operation of the expansion machine. In addition, several ancillary units are necessary for running the test bench. This includes a power electronic for high speed generators, a water conditioning system and the steam producing unit.
System-search PERFORMANCE STUDY OF A SCROLL EXPANDER WITH AMMONIA-WATER
James Muye, Juan Carlos Bruno, Rajagopal Saravanan, Alberto Coronas
Abstract: This paper examines the performance of an open drive scroll compressor modified to work as an expander operating on ammonia-water working medium. The modelling and simulation of the scroll expander is carried out with EES program. In this study a simulation of the expander performance at various pressure ratios (2-4), expander speeds (2500-7500 rpm) and ammonia concentrations (0.8-0.99) at a constant supply pressure (5 bar) and temperature (105oC) has been presented. The scroll expander produced a work output of 0.29 to 1.5 kW, with isentropic efficiencies of between 0.48-0.64. At the assumed in let conditions, the optimum expansion ratio for the expander is 3.
System-search PERFORMANCE ASSESSMENT OF ORGANIC RANKINE CYCLE DRIVEN VAPOR COMPRESSION HEAT PUMP
Violette Mounier, Jürg Schiffmann
Abstract: Vapor compression cycle heat pumps driven by thermal engines such as organic Rankine cycles (HP-ORC) are able to provide both heating and cooling for domestic applications for a large set of heat sources. Recently, an oil-free Compressor-Turbine Unit (CTU) in a HP-ORC has been investigated in which both the radial ORC turbine [1] and the radial heat pump compressor are running on the same gas bearing supported shaft [2]. The radial compressor and the radial inflow turbine have tip diameters of the order of 20 mm. The CTU has been tested at rotor speeds in excess of 200 krpm with shaft powers up to 2.4 kW. The compressor and the turbine were operated at pressure ratios of up to 2.8 and 4.4, while reaching isentropic efficiencies in excess of 70%, thus validating the concept based on small-scale turbomachinery[3]. Based on reduced order models, a study has been conducted to investigate the feasibility of the HP ORC system using an optimized CTU running with different working fluids and with different operating conditions. The effect of a regenerator and of the turbine inlet pressure has been investigated. The results reveal that HP-ORC systems can achieve a theoretical COP up to 2.11 and exergetic efficiencies up to 80% with R134a working fluid for an heating capacity of 40 kW, a sink temperature of 35 °C, an inlet turbine temperature of 180 °C and an evaporation temperature of 7 °C while preliminary experimental results [4] show COP up to 1.55 and exergetic efficiency up to 41%. It turns out that these cycles are of great interest since they are highly flexible, offer a wide operation range and can run on low GWP, hazard less fluids. Since heating power has a direct impact on the CTU-unit the scaling effects on the turbomachinery design and on rotor speed are investigated and presented in this article.
System-search SYSTEMATIC FLUID-SELECTION IN EARLY STAGES OF ORC DESIGN – A PRACTICAL ENGINEERING APPROACH
Maximilian Roedder, Christoph Laux, Matthias Neef
Abstract: The selection of a working fluid plays a major role in the design phase of organic Rankine cycles (ORC). Therefore, a suitable working fluid builds the foundation for a high power production in an ORC, which also leads to high cycle efficiencies and is hence one of the most significant selling arguments. But the selection of a working fluid should not only depend on the power output of the ORC. There are technical rules for example given by the legislator, which also has to be respected with high priority. For a detailed research of potential working fluids a selection-procedure was developed. The method uses 22 criteria out of six main categories (thermodynamical, procedural/thermodynamical, safety, environmental, economical and chemical), which should be considered with adequate priority related to the implementation of the ORC. During the first tests, not all of the 22 criteria were evaluated, therefore, the process was improved with an accurate elaboration of the omitted criteria and by the integration of the working fluid mass flow directly into the selection process. The procedure itself is divided into four main steps, the pre-selection, the elimination process, the ranking process and the final fluid choice. Such a proceeding requires the subdivision of the 22 criteria into elimination criteria (EC) and tolerance criteria (TC). An advantage of this disposition into a structured processing in the early design phase of the ORC is the direct elimination of working fluids in the pre-selection- and elimination-phase. The application of the selection-procedure into the design process leads also to a saving in development time and helps to make an educated decision. This contribution deals with a comprehensive compilation of all 22 criteria deemed as relevant for the fluid selection and shows examples of fluid selections.
System-search EXPERIMENTAL STUDY OF AN ORC (ORGANIC RANKINE CYCLE) WITH THERMAL OIL FOR WASTE HEAT RECOVERY OF A DIESEL ENGINE
Gequn Shu, Mingru Zhao, Hua Tian
Abstract: Waste heat from exhaust gas of diesel engine could be recovered to increase engine’s efficiency and decrease exhaust pollution. In this research, an Organic Rankine Cycle (ORC) test bench with thermal oil as heat transfer medium was set up to recovery the waste heat from a 240kW heavy-duty diesel engine. R123 was chosen for working fluid and expansion valve was employed temporarily to investigate the properties of waste heat. Experiments have been conducted to measure the available heat of exhaust gas in the different loads and speeds of engine. The results show the amount and the quality of waste heat that can be potentially recovered by this test bench during different conditions of engine, of which the maximum exergy and the potential power ability are 18.53kW, and 9.67kW separately. The maximum efficiency of exergy and potential power ability are 26.80% and 14.32% separately. Also, with thermal oil cycle integrated, the transient performance of the ORC test bench was investigated.
System-search AERODYNAMIC DESIGN OF RADIAL INFLOW TURBINE FOR MEDIUM SCALE ORGANIC RANKINE CYCLE SYSTEM
Lei Chen, Boaz Habib, Nick Inskip
Abstract: The Organic Rankine Cycle (ORC) has been considered to be the most feasible technology among the existing approaches to convert low grade heat source (such as geothermal energy) and industrial waste heat into electricity. For a medium scale ORC system with a general power range of 50kW to 500kW, radial inflow turbines, with low mass flow rate and high pressure ratio, are applied more often than other types of turbines, because they are more efficient, adaptable, stable and cost-effective. When developing such a turbine, aerodynamic design is a step of vital importance. This paper presents a complete aerodynamic design process of a 100kW radial inflow turbine, including preliminary design, three dimensional modelling of blades and volute, and three dimensional numerical simulation. The preliminary design is carried out by using ANSYS RTD which can efficiently generate an optimal solution whilst fixing the mass flow rate, the pressure ratio and the blade speed ratio. Then, based on the preliminary design results, the cascade shape modelling of stator and rotor is conducted through in-house code and ANSYS BladeGen respectively. Following that, the three dimensional modelling of stator and rotor is conducted by stacking the cascades along a specified line. The volute is defined by a series of radial circular sections on the periphery of the turbine and the radii of the sections are obtained through the free vortex theory. ANSYS DesignModeler is used to perform three dimensional modelling of the volute. Finally, three dimensional numerical simulation of the radial inflow turbine is carried out by employing ANSYS TurboGrid, ICEM and CFX, where the R245fa is used as the working fluid. Detailed analyses of the flow field across the turbine stage and the volute are presented and the performance assessment of the turbine in terms of efficiency, blade speed ratio and mass flow rate is illustrated.
System-search ADAPTING WASTE HEAT RECOVERY TECHNOLOGIES FOR LOW CARBON OFF-HIGHWAY VEHICLES
Apostolos Pesiridis, Fuhaid Alshammari, Benjamin Franchetti Benjamin Franchetti
Abstract: Waste Heat Recovery (WHR) technologies aim at recovering part of the otherwise wasted heat in the exhaust gases of a combustion engine and convert it to useful power, resulting in lower fuel consumption and pollutant emissions. Brunel University London, Entropea Labs and Mahle Powertrain have jointly optimised Waste heat Recovery technologies based on the Rankine cycle for other applications in the past. Experience gained in the design and manufacturing of the components for Organic Rankine Cycle (ORC) WHR systems for large displacement diesel engines is applied to increase the Off-Highway Vehicle (OHV) diesel engine fuel economy by 10% or higher. The project is funded by Innovate UK for a two -year period ending in May 2017. The proposed technology is modular, non-invasive and reversible, enabling it to be scaled across the range of new engine production irrespective of manufacturer while also being retrofitable to the large number of OHV engines already in service. Moreover, the technology and expertise has the potential to be further exploited by adapting it and scaling it to other transport and stationery power generation applications. The specific objectives of the project are: (1) ORC Model Development for ORC WHR applications, (2) Engine Simulation Development, (3) ORC WHR Component Development, (4) ORC WHR system performance demonstration and validation On-Engine, and (5) Validate retrofit capability in preparation for On-Vehicle demonstration. The potential impact from the realization of the project makes the technology highly competitive. The OHVs account for approximately 15% of all UK surface transportation emissions [1], achieving a retrofitable and scalable ORC-WHR technology, with 10% fuel efficiency increase, can account to a potential £1 billion (€1.4 billion) in fuel savings for fleet operators in the UK alone. In addition, the reduction in emissions will enable OEMs to meet the requirements outlined in pollution reduction legislation.
System-search ABOVE GROUND GEOTHERMAL AND ALLIED TECHNOLOGIES – PAVING THE RESEARCH ROADMAP
Boaz Habib, Nick Inskip, Lei Chen Chen, Mohammed Farid, Brent Young
Abstract: The Above Ground Geothermal and Allied Technologies (AGGAT) Research and Development (R&D) Programme is a collaborative initiative borne out of a Clean Energy development focus in the Heavy Engineering Industry of New Zealand. The programme is a positive testament to government, industry and academia as well as international experts working collaboratively to achieve a common objective of providing an R&D platform for growth in the clean energy technologies. The predominant focus of this programme is on the Organic Rankine Cycle using the research expertise of academic institutions and manufacturing capability of Heavy Engineering companies in NZ. Research is carried out in the areas of Technology Concepts, Turbines, Heat Exchangers, Control Systems, Materials and Fluids. The programme has been in operation for nearly three years now and has made progress towards establishment of pilot scale testing facilities on waste heat and geothermal based heat resource sites. Research progress update is provided along with opportunities identified for future collaboration especially with international partners.
System-search CONNECTION OF A DISTRICT HEATING SYSTEM AND AN ORC GEOTHERMAL PLANT
Valdimarsson Pall
Abstract: Cogeneration of electricity and heat for district heating is feasible in colder climates, where a city having market for district heating is close to the plant. Geothermal power plants usually produce base load. Heat load for district heating is dependent on the ambient temperature, and has a high peak to average heat load ratio. The production of district heating will reduce the electrical output of the geothermal plant, thus incurring lost revenue. This loss it the more, the higher the district heating load is. The characteristics of district heating consumption influence these losses as well, and certain measures to influence the consumer behaviour are necessary. The minimization of this loss of electrical generation of the geothermal plant is crucial for the economics of the cogeneration. This paper presents the cogeneration couplings suggested by Atlas Copco. Good temperature profiles for district heating supply and return are presented, and the relation between these temperature profiles and revenue loss is presented. Suggestions regarding tariff system and how the district heating consumer should me motivated are as well presented.
System-search A NEW DESIGN OF AN ORC PLANT FOR HIGH ENTHALPY GEOTHERMAL RESOURCES
Valdimarsson Pall, Markus Sauerborn
Abstract: The fluid in a high enthalpy geothermal field is saturated liquid with dissolved minerals and gases. The wells produce a mixture of mineralized brine, non-condensable gas and steam. The well fluid cannot be cooled below the silica saturation in the plant. The non-condensable gas has to be separated from the fluid at some stage and disposed of. This will all influence the power plant design. The heat of the geothermal fluid is transferred to a working fluid in heat exchangers in an ORC plant. All heat transfer over a finite temperature difference will cause exergy loss, which will be less, the smaller the temperature difference is. But the cost of the heat exchanger will be higher the smaller this difference is, so an optimization has to be made. The temperature profiles both for the geothermal fluid and the ORC working fluid are determined from the thermodynamic properties of the fluids. The selection of the working fluid has thus to be made with the thermodynamic properties of the complex geothermal mixture in mind. Atlas Copco is proposing a novel way of fitting an ORC power plant to geothermal fluid from high enthalpy resources. This plant is described, and temperature-heat duty and Carnot efficiency-heat duty diagrams are used to describe how the ORC plant is optimized for each geothermal fluid mixture and enthalpy.
System-search NOWASTE: WASTE HEAT RE-USE FOR GREENER TRUCK
Ludovic Guillaume, Vincent Lemort, Andrea Perosino, Federica Bettoja, Thomas Reiche, Thomas Wagner
Abstract: Automotive world is rapidly changing driven by the CO2 emission regulations worldwide asking for a significant fuel consumption reduction. The internal combustion engine will be the principal powertrain concept for the upcoming decades, especially when it comes to road transportation. Even if the efficiency of the ICE’s has increased within the last years, around 30-50% of the fuel indicated energy is still lost via waste heat and could be partly recovered via secondary cycles as the Rankine cycle, Brayton cycle or Stirling cycle. However, preliminary studies have shown that for a heavy duty Diesel application the Rankine cycle offers the highest potential when it comes to efficient waste heat recovery. The adoption of such technology in the automotive domain requires specific R&D activities to develop the components and identify the most appropriate system architectures and level of integration in order to achieve sustainable costs and the required level of reliability. In this context, the EU has funded in the frame of the 7th framework program the project NOWASTE: a collaborative project between several companies and institutions: Centro Ricerche Fiat S.C.p.A., Volvo Technology AB, Dellorto SPA, Univesitè de Liege, AVL List GMBH, Faurecia systems d’echappement SAS. This project has the goal to develop a waste heat recovery system based on Organic Rankine Cycle (ORC) for a Heavy Duty Truck application with the aim to realize fuel economy savings. The target applications have been chosen among the Iveco and Volvo fleets. The partners have designed and realized two Rankine cycle systems suitable to be installed on board of a truck with the aim to convert the waste heat of the exhaust gases into useful energy to be used in mechanical or electrical form. The performances of these systems have been evaluated on engine test benches and are currently under evaluation also the system’s on board performances.
System-search MODELLING, EXPERIMENTATION AND SIMULATION OF A REVERSIBLE HP/ORC UNIT TO GET A POSITIVE ENERGY BUILDING
Olivier Dumond, Carolina Carmo, Sylvain Quoilin, Vincent Lemort
Abstract: This paper presents an innovative building comprising a heat pump connected to a solar roof and a geothermal heat exchanger. This heat pump is able to invert its cycle and operate as an ORC (Fig. 1). The solar roof is producing large amount of heat throughout the year. This allows covering the building annual heating needs and, furthermore, electricity is produced thanks to the surplus of heat produced by the roof in the HP/ORC reversible unit. This paper is focusing on three main points: sizing, experimentation and simulation of the reversible unit. First, an optimal sizing of the components and fluid R134a shows promising performance with a net electrical energy produced over one year reaching 4030 kWh. Following that, a prototype has been build and has proven the feasibility of the technology. Finally, a dynamic simulation code including the building, the ground heat exchanger, the thermal energy storage, the solar roof and the reversible HP/ORC unit is developed and allows to perform a sensivity analysis. Annual results show that this technology allows to get a Positive Energy Building.
System-search EXPERIMENTAL VALIDATION OF A DOMESTIC STRATIFIED HOT WATER TANK MODEL IN MODELICA FOR ANNUAL PERFORMANCE ASSESSMENT
Carolina Carmo, Olivier Dumot, Mads Nielsen
Abstract: The use of stratified hot water tanks in solar energy systems - including ORC systems- as well as heat pump systems is paramount for a better performance of these systems. However, the availability of effective and reliable models to predict the annual performance of stratified hot water tanks coupled with energy system solutions is limited. In this poster, a discretized model of a stratified tank developed in Modelica is presented. The physical phenoma to be considered are the thermal transfers by conduction and convection – stratification, heat loss to ambient, charging and discharging with direct inlet and outlet and immersed heat exchangers. Results of experimental and numerical investigations in a residential hot water tank with two immersed heat exchangers, one inlet and one outlet are presented and the performance of the model is assessed.