New heat conversion technologies need to be developed and improved to take advantage of the necessary increase in the supply of renewable energy. The Organic Rankine Cycle is well suited for these applications, mainly because of its ability to recover low-grade heat and the possibility to be implemented in decentralized lower-capacity power plants. In this paper, an overview of the different ORC applications is presented. A market review is proposed including cost figures for several commercial ORC modules and manufacturers. An in-depth analysis of the technical challenges related to the technology, such as working fluid selection and expansion machine issues is then reported. Technological constraints and optimization methods are extensively described and discussed. Finally, the current trends in research and development for the next generation of Organic Rankine Cycles are presented.

Techno-economic survey of Organic Rankine Cycle (ORC) systems

https://hal.archives-ouvertes.fr/hal-00614641/document

Testing and modeling a scroll expander integrated into an Organic Rankine Cycle

Experimental study on an open-drive scroll expander integrated into an ORC (Organic Rankine Cycle) system with R245fa as working fluid

This thesis contributes to the knowledge and the characterization of smallscale Organic Rankine Cycles (ORC). It is based on experimental data, thermodynamic models and case studies. The experimental studies include: 1. A prototype of small-scale waste heat recovery ORC using an open-drive oil-free scroll expander, declined in two successive versions with major improvements. 2. A prototype of hermetic scroll expander tested on vapor test rig designed for that purpose. The achieved performance are promising, with expander overall isentropic effectivenesses higher than 70% and cycle efficiencies comparable or higher than the typical efficiencies reported in the scientific literature for the considered temperature range. New steady-state semi-empirical models of each component are developed and validated with the experimental data. The global model of the ORC prototype allows predicting its performance with a good accuracy and can be exploited to simulate possible improvements or alternative cycle configurations. Dynamic models of the cycle are also developed for the purpose of evaluating the system's reaction to transient conditions. These models are used to define and compare different control strategies. The issues of cycle optimization and fluid selection are treated using the steady-state semi-empirical models. The thermodynamic optimization of such cycles is first demonstrated by practical examples. Furthermore, three different methods for fluid selection are proposed, investigated and compared. Their respective advantages and fields of application are described. Finally, two prospective studies of small-scale ORC systems are proposed. The first one is a solar ORC designed for the rural electrification of remote regions in Africa. This prototype aims at competing with the photovoltaic technology, with the advantage of generating hot water as by-product. The second prospective study deals with the recovery of highly transient heat sources. Advanced regulation strategies are proposed to address the practical issues of such systems. These strategies are compared with the state-of-theart strategies and show a non-negligible potential of performance improvement.

Sustainable energy conversion through the use of Organic Rankine Cycles for waste heat recovery and solar applications

This paper presents the results of an experimental study carried out on a prototype of a hermetic scroll expander, integrated into a gas cycle test rig, whose working fluid is HFC-245fa. This system is designed to test only the performance of the expander. It is made up mainly of a scroll compressor, a scroll expander, a heat exchanger, and a by-pass valve. The latter is used to adjust the pressure ratio imposed to the expander. The expander was originally a compressor designed for heat pump applications and is characterized by a nominal power input of 2.5kWe. Performance of the expander is evaluated in terms of isentropic effectiveness and filling factor as functions of the main operating conditions. The study also investigates the impact of oil mass fraction on the expander performance. Maximum overall isentropic effectiveness of 71.03 per cent is measured, which is partly explained by the good volumetric performance of the machine. Using the experimental data, parameters of a semi-empirical simulation model of the expander areidentified. This modelisusedtoanalyse themeasured performance oftheexpander. Finally, a polynomial empirical model of the expander is proposed for fast and robust simulations of organic Rankine cycle systems.

https://journals.sagepub.com/doi/pdf/10.1177/0957650911413840

Experimental characterization of a hermetic scroll expander for use in a micro-scale Rankine cycle

Cryogenic expanders with work production have a predominant influence on refrigerator/liquefier reliability and efficiency. This paper presents a new cryogenic expander technology for a 10 L/h helium liquefier: the scroll expander. In order to optimize the spiral geometry, a numerical model was worked out to simulate the thermodynamic behavior of the scroll expander. This numerical tool highlights the strong influence on the isentropic efficiency of the clearances between the fixed and the orbiting spirals. Rigid driving mechanism with high rotation accuracy was needed to obtain clearances ranging from 10 to 20 μm. A three-crankshaft type mechanism was manufactured. A system of one thermal jack per shaft, based on controlled thermal expansion of an aluminum alloy tube and an abradable coating deposited on the fixed spiral were developed to overcome this constraint. This expander has been tested on a Brayton cycle refrigerator and reached an isentropic efficiency of 50 to 60% for inlet gas conditions of 35 K and 0.7 MPa. Comparison of measurements with numerical results shows the effect on the isentropic efficiency of the ultimate expansion pressure between the chamber just before opening and the cycle low pressure. Considering the good experimental results and the peculiar technology of the scroll expander, this prototype could be also used as a wet expander in place of a Joule-Thomson valve.

Cryogenic scroll expander for claude cycle with cooling power of 10 to 100 Watts at 4.2 K

The TORE SUPRA refrigerator design and manufacture have both been governed by several strict design criteria. These include reliable operation over long periods (8,000 hours per year), pulsed thermal loads at 1.75 K and 4.0 K (every 4 minutes), fully automatic control in the various operating modes, low operating costs and acting as a technical demonstration so that larger future designs could be extrapolated from this base. The paper reviews these criteria, and presents the current status.

The tore supra 300 W-1.75 K refrigerator

Two kinds of applications are considered for magnetic refrigeration, first in the 18 K range mainly for He II cooling of superconductors and second for He I refrigeration with precooling near 20 K At He II temperatures, refrigeration by a Carnot cycle has been investigated and analysed We give a survey of the results which demonstrate the capability of magnetic refrigeration to attain high thermodynamic efficiency More interest is now devoted to He I cooling for which we compare magnetic refrigeration to the standard existing solutions For temperatures higher than 10 K, we discuss the interest and the constraints of cycles with internal heat exchange Analysis of various configurations is given to explain the choice of a new experiment being built

Gerard Claudet

Papers

Cryogenic scroll expander for claude cycle with cooling power of 10 to 100 Watts at 4.2 K

The tore supra 300 W-1.75 K refrigerator

Magnetic Refrigeration Study at CEA Grenoble