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Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: The aim of this study was to design and manufacture an experimentally testable free-piston Stirling engine (FPSE), including a linear electric generator; to develop and validate a theoretical simulation model; to identify problem areas pertaining to its manufacture; and finally to assess the work undertaken, to lay out the groundwork for the future development of a 3 kWe FPSE suitable for incorporation in a solar Stirling dish power generator. A redesigned version of the Beale B- 10B demonstrator engine was manufactured to overcome design diffculties and to simplify testing. The design made use of an electric generator designed at the Department of Electrical and Electronic Engineering at Stellenbosch University. Experimental measurements included piston and displacer motions, hot side and cold side temperatures, working space pressure, electric generator output, as well as heat rejection via a water jacket. Experimental measurements were taken prior to and subsequent to the addition of the electric generator. Indicated power was calculated as 0,659 W at a frequency of 10,99 Hz prior to the addition of the electric generator. The addition of the electric generator was unsuccessful since it was not well matched with the engine. The indicated power calculated was between 0,138 W and 0,144 W for different loads on the electric generator, while the electrical output power ranged from 1,23 mWe to 1,79 mWe. The addition of the electric generator produced non-continuous motion caused by magnetic forces instead of engine pressure variations. The major manufacturing diffculty was the attachment of magnets for the electric generator, but this was overcome with the manufacture of a special assembly jig. The theoretical simulation model was a combination of a third-order and dynamic analysis. Working space values were solved by the application of the conservation of mass, momentum and energy equations for a one-dimensional discretised model of the engine, while the motion of the piston and displacer was determined by applying the equations of motion. The majority of experimental measurements were predicted more accurately when higher heat transfer coeficients were used between the working space and wall temperatures. The theoretical simulation model was used to gain insight into the effect of input parameters on engine operation. The displacer rod diameter was shown to have implications on output power and stability, while it was shown that there is a natural tendency to deliver constant output power at a near-constant frequency over a range of piston loads for an FPSE. It was also shown that the design of an FPSE is complex and that the design of all components should be done in parallel. The control of an FPSE was seen to be both a necessity and can be used to exploit the advantages of the uncoupled nature of an FPSE. / AFRIKKANSE OPSOMMING: Die doel van hierdie studie was om 'n eksperimentele toetsbare vrye-werksuier Stirling enjin te vervaardiging, wat 'n lineêre elektriese kragopwekker insluit; om 'n teoretiese simulasie model te ontwikkel en te yk; om vervaardiging probleme te identi seer; en om die ondernemende werk te assesseer om 'n fondasie te lê vir die toekomstige ontwikkeling van 'n 3 kWe vrye-werksuier Stirling enjin wat by 'n Stirling sonskottel ingelyf kan word. 'n Herontwerpte weergawe van die Beale B-10B demonstrasie enjin was vervaardig om ontwerp probleme te bowe te kom en om die toets daarvan te vereenvoudig. Die ontwerp het gebruik gemaak van 'n elektriese kragopwekker wat by die Departement Elektriese en Elektroniese Ingenieurswese aan die Universiteit van Stellenbosch ontwerp is. Eksperimentele metings het die werksuier en verplaser bewegings ingesluit, sowel as die warm kant en koue kant temperature, die werkruimte druk, die elektriese uitset van die kragopwekker, sowel as die hitteuitruiling wat met 'n water verkoelingskringloop gepaard gaan. Eksperimentele metings was geneem voor en na die byvoeging van die elektriese kragopwekker. Kraglewering was bereken op 0,659 W teen 'n frekwensie van 10,99 Hz voordat die elektriese kragopwekker bygevoeg is. Die byvoeging van die elektriese kragopwekker was onsuksesvol omdat die nie gepas was vir die enjin nie. Die kraglewering is bereken op vlakke wat gewissel het tussen 0,138 W en 0,144 W vir die verskillende belastings op die elektriese kragopwekker, terwyl die elektriese uitset gewissel het tussen 1,23 mWe en 1,79 mWe. Die byvoeging van die elektriese kragopwekker het 'n nie-aaneenlopende beweging veroorsaak weens die magnetiese kragte wat dit beinvloed het in plaas van enjindruk variasies. Die belangrikste ontwerpuitdagings was die ontwerp van 'n werksuier en verplaser wat 'n klein toleransie passing kon handhaaf om sodoende 'n seël te verseker terwyl dit aan temperatuur variasies blootgestel was. Die grootste vervaardigingsprobleem was die aanheg van magnete vir die elektriese kragopwekker, maar dit is te bowe gekom deur 'n spesiale voeg te vervaardig. Die teoretiese simulasie model was 'n kombinasie van 'n derde-orde en 'n dinamiese analise. Werkruimte waardes was opgelos deur die toepassing van die behoud van massa, momentum en energie vergelykings vir 'n een-dimensionele gediskretiseerde model van die enjin, terwyl die beweging van die werksuier en verplaser bepaal was deur die toepassing van die bewegingvergelykings. Die meerderheid van die eksperimentele metings was meer akkuraat voorspel wanneer hoër warmteoordrag koë siënte tussen die werkruimte en muurtemperature gebruik was. Die teoretiese simulasie model was gebruik om insig in terme van die e ek van invoer veranderlikes op die enjin gedrag te toon. Daar was getoon dat die verplaserstaaf diameter implikasies het op kragoplewering en stabiliteit, terwyl die natuurlike tendens van 'n vrye-werksuier Stirling enjin gewys was om 'n konstante kraguitvoer te lewer op 'n naby-konstante frekwensie oor 'n reeks werksuier laste. Daar was ook gewys dat die ontwerp van 'n vryewerksuier Stirling enjin kompleks is en dat die ontwerp van alle komponente in parallel gedoen moet word. Die beheer van 'n vrye-werksuier Stirling enjin was gewys om beide noodsaaklik te wees, sowel as gebruik kan word om die unieke voordele van 'n vrye-werksuier Stirling enjin se ongekoppelde natuur te ontgin.

A computational model for a resonantly coupled alpha free-piston Stirling cooler is presented. The cooler consists of two isothermal working spaces for compression and expansion connected by a regenerator consisting of a stack of narrow parallel channels. The regenerator is assumed to have a linear temperature distribution along its axial direction and the working fluid is taken as an ideal gas. Control volume analysis is adapted in this model, in which each of the components of the cooler is considered a separate control volume. The compression piston is given a predetermined motion to provide the work needed by the cooler. The expansion piston and the gas trapped between the piston and the walls of the expansion cylinder are modeled as a mass, spring, and damper system. The motion of the compression piston generates a pressure difference across the cooler, and forces the working fluid to pass through the regenerator. The expansion piston responds to the pressure in its space according to Newton's second law of motion. The motion of the expansion piston is governed by the forces originating from the pressure and the cold side gas spring and dash-pot. In this way the dynamics of the moving pistons are coupled to the thermodynamics of the cooler system. A definition for the coefficient of performance (COP) that considers the heat transfer by conduction through the material making up the regenerator is introduced. This definition of the COP reflects the dependence of the cooler's performance on the length of the regenerator. From a systematic variation of this regenerator length, an optimal value can be found for a given set of operating parameters. Conservation laws of mass, momentum and energy along with ideal gas relations are used to form a set of equations fully describing the motion of the pistons and the thermal state of the cooler. A marching-in-time technique with a Runge-Kutta scheme of the fourth order is adapted to integrate the equation of motion. The plots of the motion of the pistons, the pressure-volume diagrams of the workspaces and the COP plots are provided to describe the cooler behavior. / Graduation date: 1999

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Several transverse flux and longitudinal flux linear generator topologies exist for freepiston Stirling engine applications. In this thesis the transverse flux permanent magnet linear generators are investigated together with a back-to-back converter which can deliver the electrical energy from the linear generator to the electrical network. The transverse flux permanent magnet linear generator is geometrically optimised with the aim to maximise the power-to-weight ratio while maintaining preset power and efficiency levels. An optimised 3 kW linear generator is built and the measured results correlate to the simulation results. A close-loop current control scheme is introduced to control the current of the rectifier, which is part of the back to back converter. The transverse flux permanent magnet linear generator is connected to the input of the rectifier which has the ability to force a specific current from the generator. The measured results of the rectifier correlate to the results of the simulations that were done. The current control present some complications and it is suggested that another control scheme is used. A close-loop voltage control scheme is introduced for the control of the DC bus voltage. The DC bus is connected between the rectifier and the inverter, which is the other part of the back-to-back converter. A close-loop current control scheme is introduced to control the inverter current that flows from the inverter to the electrical network. The measured results of the inverter and the DC bus correlate to the results of the simulations that were done. The results of the system, including the generator, rectifier and inverter, tested as a unit is presented and discussed. / AFRIKAANSE OPSOMMING: Verskeie tranverse vloed en longitudinale vloed lineˆere generator topologie¨e bestaan vir vrysuier Stirling enjin toepassings. In hierdie tesis word ’n transverse vloed permanente magneet lineˆere generator ondersoek saam met ’n omsetter. Die omsetter dra die elektriese energie van die generator oor aan die elektriese netwerk. Die transverse vloed permanente magneet lineˆere generator word geometries geoptimeer met die doel om die drywing-tot-gewig verhouding te maksimiseer terwyl vasgestelde drywing en effektiwiteit vlakke behou word. ’n Geoptimeerde 3kW lineˆere generator prototipe is vervaardig en die gemete resultate is geverifieer met die simulasie resultate. ’n Geslote lus stroombeheer strategie word voorgestel om die stroom te beheer van die gelykrigter, wat deel is van die omsetter. Die transverse vloed permanente magneet lineˆere generator word aan die gelykrigter, wat die vermo¨e het om ’n spesifieke stroom uit die generator te forseer, se intree verbind. Die gemete resultate van die gelykrigter wat gebou is stem goed ooreen met die van die simulasies wat gedoen is. Die stroombeheer hou komplikasies in wat bespreek word. Dus word die gebruik van ’n alternatiewe stroombeheer voorgestel. ’n Geslote lus spannings beheer strategie¨e word voorgestel om die gs. busspanning te beheer. Die gs. bus is gekonnekteer tussen die gelykrigter en die wisselrigter, wat ook deel uitmaak van die omsetter. ’n Geslote lus stroom beheer word voorgestel om die stroom te beheer wat vanaf die wisselrigter na die elektriese netwerk toe vloei. Die gemete resultate van die wisselrigter en die gs. bus stem goed ooreen met die van die simulasies wat gedoen is. Die resultate van die hele stelsel, wat die generator, gelykrigter en die wisselrigter insluit, wat as ’n eenheid getoets is word weergegee en bespreek.

Thesis (PhD)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: Control of beta-type free-piston Stirling engines has been the topic of research and development for many years. In this dissertation, an alternative approach to free-piston Stirling engine control, namely direct piston displacement control, is proposed. Direct piston displacement control entails the instantaneous and direct control of the piston displacement to control the engine according to preferred criteria, e.g. maximum power conversion or efficiency. To control free-piston engines in this manner, it is necessary to independently control both the displacement of the displacer and the power piston in real time. The primary arrangement by which to achieve this is through external control of the instantaneous forces exerted by the linear electrical machines fixed to the pistons. The challenge of displacement control is whether suitable linear machine technology exists or whether technology could be established that would adhere to the requirements of real time direct control. To answer the question whether direct piston displacement control is at all possible, a process was followed to set specifications that linear machines should adhere to and to set design guidelines for linear machines and free-piston Stirling engines. The first step was to establish the ability to simulate free-piston Stirling engine dynamics accurately. This was done by adapting a second order formulation and to verify and improve the accuracy thereof by comparing simulated results with experimental results of one of the best documented Stirling engines, namely the GPU-3 engine. It was found that this second order formulation could simulate the GPU-3 engine to a fair degree of accuracy. Key indicators were defined and later refined with the view of setting specifications. A case study of the influence of a range of variations, including operational, dimensional and other variations, on the dynamics of the GPU-3 was then undertaken. From the findings of this case study, specifications of the key indicators and design guidelines were established. A design optimisation approach was proposed to evaluate linear machine topologies. This approach makes specific provision for the specifications that linear machines need to adhere to, as well as for representative dynamic responses of the forces exerted on the linear machine by the displacer or the power piston. These representative responses and the associated piston displacement were determined for the displacer, the power piston and the combination of the two from the study conducted to set specifications. An air-core, longitudinal flux linear machine with surface mounted permanent magnets (LFPM) was then evaluated to determine its suitability for direct piston displacement control. This linear machine topology was optimised for the traditional approach to establish a benchmark with which to compare subsequent optimisations. The LFPM linear machine not only compared well with other topologies for the traditional application in resonant free-piston Stirling engines, but it was found also to be able to perform displacement control for both the displacer and the power piston. For both pistons, displacement should however be limited to sinusoidal displacement, and in the case of the displacer, an important qualification is that the linear machine should be assisted by spring forces to reach practical design optimisations. Direct piston displacement control is shown to be possible. Future work should concentrate on the practical implementation thereof in free-piston Stirling engines. / AFRIKAANSE OPSOMMING: Die beheer van beta-tipe vrysuier Stirling enjins is al vir baie jare die onderwerp van navorsing en ontwikkeling. In hierdie proefskrif word ’n alternatiewe benadering tot vrysuier Stirlingenjins voorgestel, naamlik direkte suierverplasingsbeheer. Direkte suierverplasingsbeheer behels die oombliklike en direkte beheer van die suierverplasing om die enjin volgens voorkeur kriteria, soos maksimum drywingsomsetting of benuttingsgraad, te beheer. Om vrysuier enjins op hierdie wyse te beheer, is dit noodsaaklik om intyds die verplasing van beide die verplaser en die werksuier onafhanklik te beheer. Die primêre wyse om dit te bereik is deur eksterne beheer van die oomblikskragte wat uitgevoer word deur die lineêre masjiene wat vas is aan die suiers. Die uitdaging van verplasingsbeheer is of toepaslike lineêre masjien tegnologie bestaan en of tegnologie gevestig kan word wat sal voldoen aan die vereistes van intydse direkte beheer. Om die vraag te beantwoord of direkte suierverplasingsbeheer hoegenaamd moontlik is, is ’n proses gevolg om spesifikasies daar te stel waaraan lineêre masjiene moet voldoen en om ontwerpsriglyne vir lineêre masjiene en vrysuier Stirling enjins te stel. Die eerste stap was om die vermoë daar te stel om vrysuier Stirling enjin dinamika akkuraat te simuleer. Dit is gedoen deur ’n tweede orde formulering aan te pas en om die akkuraatheid daarvan te kontroleer en te verbeter deur gesimuleerde resultate met eksperimentele resultate van een van die bes gedokumenteerde Stirling enjins, naamlik die GPU-3 enjin, te vergelyk. Daar is bevind dat die tweede orde formulering die GPU-3 tot ’n redelike mate akkuraat kon simuleer. Sleutel aanwysers is gedefinieer en later verfyn met die oog op die daarstelling van spesifikasies. ’n Gevallestudie van die invloed van ’n reeks variasies, insluitende operasionele, dimensionele en ander variasies, op die dinamika van die GPU-3 is onderneem. Gegrond op die bevindinge van hierdie gevallestudie kon spesifikasies en ontwerpsriglyne vasgestel word. ’n Ontwerpsoptimeringsbenadering is voorgestel om lineêre masjiene te evalueer. Hierdie benadering maak spesifiek voorsiening vir die spesifikasies waaraan lineêre masjiene moet voldoen, sowel as verteenwoordigende dinamiese response van die kragte wat op die lineêre masjien van die verplaser en die werksuier uitgeoefen word. Vanaf die bevindinge van die studie wat uitgevoer is om spesifikasies daar te stel, is verteenwoordigende response en gepaardgaande suierverplasing bepaal vir die verplaser, die werksuier en die kombinasie van die twee. ’n Lugkern, longitudinale vloed lineêre masjien met oppervlak-gemonteerde permanente magnete (LVPM) is toe geëvalueer om die geskiktheid daarvan te bepaal vir direkte suierverplasingsbeheer. Hierdie lineêre masjien topologie is geoptimeer vir die tradisionele benadering om ’n maatstaf te vestig waarteen daaropvolgende optimerings vergelyk kan word. Die LVPM lineêre masjien vergelyk nie net goed met ander topologieë vir die tradisionele toepassing in resonante vrysuier Stirling enjins nie, maar daar is ook bevind dat dit in staat is om verplasingsbeheer te doen vir beide die verplaser en die werksuier. Vir beide suiers moet die verplasing egter tot sinusvormige verplasing beperk word en in die geval van die verplaser, is ’n belangrike kwalifikasie dat die lineêre masjien ondersteun moet word deur veerkragte om praktiese ontwerpsoptimerings te bereik. Daar is aangetoon dat direkte suierverplasingsbeheer moontlik is. Toekomstige werk moet konsentreer op die praktiese implementering daarvan in vrysuier Stirling enjins.

The percentage of renewable energy within the global electric power generation portfolio is expected to increase rapidly over the next few decades due to increasing concerns about climate change, fossil fuel costs, and energy security. Solar thermal energy, also known as concentrating solar power (CSP), is emerging as an important solution to new demands for clean, renewable electricity generation. Dish-Stirling (DS) technology, a form of CSP, is a relatively new player in the renewable energy market, although research in the technology has been ongoing now for nearly thirty years. The first large plant utilizing DS technology, rated at 1.5 MW, came online in January 2010 in Peoria, AZ, and plants rated for several hundred MW are in the planning stages. Increasing capacity of this technology within the utility grid requires extensive dynamic simulation studies to ensure that the power system maintains its safety and reliability in spite of the technological challenges that DS technology presents, particularly related to the intermittency of the energy source and its use of a non-conventional asynchronous generator. The research presented in this thesis attempts to fill in the gaps between the well established research on Stirling engines in the world of thermodynamics and the use of DS systems in electric power system applications, a topic which has received scant attention in publications since the emergence of this technology. DS technology uses a paraboloidal shaped dish of mirrors to concentrate sunlight to a single point. The high temperatures achieved at the focal point of the mirrors is used as a heat source for the Stirling engine, which is a closed-cycle, external heat engine. Invented by the Scottish clergyman Robert Stirling in 1816, the Stirling engine is capable of high efficiency and releases no emissions, making it highly compatible with concentrated solar energy. The Stirling engine turns a squirrel-cage induction generator, where electricity is delivered through underground cables from thousands of independent, autonomous 10-25 kW rated DS units in a large solar farm. A dynamic model of the DS system is presented in this thesis, including models of the Stirling engine working gas and mechanical dynamics. Custom FORTRAN code is written to model the Stirling engine dynamics within PSCAD/EMTDC. The Stirling engine and various other components of the DS system are incorporated into an electrical network, including first a single-machine, infinite bus network, and then a larger 12-bus network including conventional generators, loads, and transmission lines. An analysis of the DS control systems is presented, and simulation results are provided to demonstrate the system's steady state and dynamic behavior within these electric power networks. Potential grid interconnection requirements are discussed, including issues with power factor correction and low voltage ride-through, and simulation results are provided to illustrate the dish-Stirling system's capability for meeting such requirements.

Ce travail traite la modélisation et l'optimisation des centrales solaires thermodynamiques à concentration produisant de l'électricité pour l'électrification des zones rurales isolées et mal raccordées au réseau électrique. D’abord, un modèle optique et thermique détaillé des concentrateurs solaires cylindro-paraboliques est présenté permettant l'identification de capteurs existants et la création de corrélations qui peuvent être injectées dans un modèle plus global. Dans un second temps, un modèle original d'un stock de chaleur stratifié de type « lit de roche » est développé. Le nouveau modèle proposé permet de déterminer analytiquement le profil de température dans le stock à n'importe quel instant dans le cas d'une température d'entrée régulée. Ensuite, deux alternatives de bloc moteur sont modélisées : le moteur Stirling et le Cycle Organique de Rankine (ORC acronyme anglais pour Organic Rankine Cycle). Concernant le moteur Stirling, une revue critique des modèles existants a été effectuée. Certains de ces modèles ont été implémentés et complétés par des modèles originaux des pertes par fuite de matière et par effet navette. Le cycle organique de Rankine, lui, est modélisé par un modèle orientée vers l'optimisation. Enfin, une optimisation mono et multicritère d’une centrale solaire est effectuée. La configuration étudiée est équipée d’un stock de chaleur et d’une chaudière d’appoint. Elle est optimisée selon trois critères : le coût moyen actualisé de l'électricité (LCOE acronyme anglais pour Levelized Cost Of Electricity), le rendement énergétique de la centrale et la quantité de CO2 émise par Kilowatt heure d'électricité produite / This work deals with the modelling and the optimization of thermodynamic solar power plants intended to supply electricity to isolated locations. Firstly, a state of the art of solar collectors is achieved and a model for parabolic trough collectors is proposed. This model is used for actual collectors identification. It is used also to propose correlations to be introduced in the whole system model. In a second time, a state of the art of energy storage technologies is conducted and an original model of a packed bed storage tank is proposed. This model gives an explicit solution of the temperature inside the tank without using a time step based numerical resolution. Two alternatives for the power block are given: Stirling engines and Organic Rankine Cycles. For Stirling engines, a critical review of existing models is performed. Some losses occurring in Stirling engines are not well documented in the literature as leakage losses at the power piston and displacer gap losses. Therefore, original models are proposed to estimate these losses. When compared to former models in the literature, the new model of the displacer gap losses demonstrates clearly that it is very important to use decoupled models with caution. Concerning the ORC, an optimization-oriented model is proposed. Finally, a mono and multi-objective optimization of a solar power plant is performed. The optimized system is composed of a solar field, a packed bed heat storage, a power block and an auxiliary fired heater. Objective functions used in this study are: the Levelized Cost of Electricity (LCOE), the energetic efficiency of the power plant and CO2 emission per kilowatt hour of electricity

Cette thèse s'inscrit dans le cadre du projet collaboratif MICROSOL, mené par Schneider Electric, et qui oeuvre pour le développement de micros centrales solaires thermodynamiques destinées à la production d'électricité en sites isolés (non connectés au réseau électrique) en exploitant l'énergie thermique du soleil. Le but de cette thèse étant le développement de lois de commande innovantes et efficaces pour la gestion de l'énergie de deux types de micros centrales solaires thermodynamiques : à base de moteur à cycle de Stirling et à base de machines à Cycle de Rankine Organique (ORC). Dans une première partie, nous considérons une centrale solaire thermodynamique à base de machine à cycle de Stirling hybridée à un supercondensateur comme moyen de stockage d'énergie tampon. Dans ce cadre, nous proposons une première loi de commande validée expérimentalement, associée au système de conversion d'énergie du moteur Stirling, qui dote le système de performances quasi optimales en termes de temps de réponse ce qui permet de réduire la taille du supercondensateur utilisé. Une deuxième loi de commande qui gère explicitement les contraintes du système tout en dotant ce dernier de performances optimales en terme de temps de réponse, est également proposée. Cette dernière loi de commande est en réalité plus qu'un simple contrôleur, elle constitue une méthodologie de contrôle applicable pour une famille de systèmes de conversion de l'énergie.Dans une deuxième partie, nous considérons une centrale solaire thermodynamique à base de machine à cycle de Rankine Organique (ORC) hybridée à un banc de batteries comme moyen de stockage d'énergie tampon. Etant donné que ce système fonctionne à vitesse de rotation fixe pour la génératrice asynchrone qui est connectée à un système de conversion d'énergie commercial, nous proposons une loi de commande prédictive qui agit sur la partie thermodynamique de ce système afin de le faire passer d'un point de fonctionnement à un autre, lors des appels de puissance des charges électriques, le plus rapidement possible (pour réduire le dimensionnement des batteries) tout en respectant les contraintes physiques du système. La loi de commande prédictive développée se base sur un modèle dynamique de la machine ORC identifié expérimentalement grâce à un algorithme d'identification nonlinéaire adéquat. / This Ph.D thesis was prepared in the scope of the MICROSOL project, ledby Schneider Electric, that aims at developing Off-grid solar thermodynamic micro powerplants exploiting the solar thermal energy. The aim of this thesis being the development of innovative and efficient control strategies for the energy management of two kinds of solar thermodynamic micro power plants: based on Stirling engine and based and Organic RankineCycle (ORC) machines.In a first part, we consider the Stirling based solar thermodynamic micro power planthybridized with a supercapacitor as an energy buffer. Within this framework, we propose afirst experimentally validated control strategy, associated to the energy conversion system ofthe Stirling engine, that endows the system with quasi optimal performances in term of settlingtime enabling the size reduction of the supercapacitor. A second control strategy that handlesexplicitly the system constraints while providing the system with optimal performances interm of settling time , is also proposed. This control strategy is in fact more than a simplecontroller, it is a control framework that holds for a family of energy conversion systems.In a second part, we consider the Organic Rankine Cycle (ORC) based thermodynamicmicro power plant hybridized with a battery bank as an energy buffer. Since this system worksat constant speed for the asynchronous generator electrically connected to a commercial energyconversion system, we propose a model predictive controller that acts on the thermodynamicpart of this system to move from an operating point to another, during the load power demandtransients, as fast as possible (to reduce the size of the battery banks) while respecting thephysical system constraints. The developed predictive controller is based upon a dynamicmodel, for the ORC power plant, identified experimentally thanks to an adequate nonlinearidentification algorithm.