Thermo-economic optimization during preliminary design phase of organic Rankine cycle systems for waste heat recovery from exhaust and recirculated gases of heavy duty trucks

peer reviewedWaste heat recovery (WHR) Organic Rankine Cycle (ORC) system is a very promising technology for reducing fuel consumption and consequently the CO2 emissions of future heavy-duty trucks (HDT). Nonetheless, the adoption of this technology in the automotive domain requires specific R&D activities going from the system definition to the on-board integration. This study focuses on the preliminary design phase of ORC systems recovering the heat wasted from two of the sources available on a HDT: the exhaust and recirculated gases. From these heat sources and their combinations, 6 possible architectures are identified. On the other hand, 4 volumetric expansion machine technologies are considered (scroll, screw, piston and vane Expanders). At the end, 24 topologies are therefore modelled considering the main components (Pump, Heat exchangers, Expansion machines). A three-step optimization method is proposed to identify the most promising system. First, the most suitable conditions are identified for the design of the ORC systems using a simple model of volumetric expansion machine. In a second step, the design phase, using more detailed models for the expansion machines, a thermos-economic optimization is performed. Finally, in a third step, the output power of the latter system models is maximized in off-design conditions, optimizing the evaporating pressure and the overheating degree

Online Measurement Of The Working Fluid Mass Repartition In A Small-Scale Organic Rankine Cycle Power System

This paper presents an experimental investigation of the working fluid charge repartition in a 2kWe ORC (organic Rankine cycle) test bench. To this end, an online measurement apparatus is built and fully calibrated to evaluate the charge enclosed in the three heat exchangers and the liquid receiver of the ORC unit. By changing all the system boundary conditions (including the charge enclosed in the test rig), an experimental database of 304 steady-state points is gathered and post-treated. The charge inventories obtained by online measurements demonstrate promising results on average but experience high uncertainties when considering each point individually (i.e. the uncertainty on the global inventory is around ± 2.5 kg for a total charge of 31.2 kg). Deviations of the evaporator mass measurements are identified at high temperature of the heat source and discussed in details. A reconciliation method is applied to the raw measurements in order to retrieve consistent charge inventories while accounting for the different sources of uncertainty. Ultimately, the paper analyses the impact of increasing the charge in the ORC and how this parameter influences the thermodynamic state of the system

Impact of model reduction on the dynamic simulation of a micro-scale concentrated solar power system integrated with a thermal storage

peer reviewedBecause of the intermittent nature of solar irradiances, micro-scale solar thermal power systems almost never operate in nominal operating conditions. They are characterized by strong transients and require robust, fast and accurate dynamic simulation tools to permit a proper evaluation of their performance. Model reduction, i.e. the simplification of detailed models, is an attractive method to improve the computational efficiency while simulating such systems. In this context, a µCSP plant featuring a solar field of parabolic troughs, a thermocline storage and a 5kWe power unit is investigated. Both the solar field and the thermocline storage are modeled with complex and simplified methods. The whole power plant is simulated under identical operating condition and deviations between the simulation results are analyzed. Benefits and limitations of the current modeling approach are assessed. Improvements for the modeling of the thermocline storage are identified, implemented and validated. The Modelica language is used as simulation tool and the models developed in this work are integrated in the open-source ThermoCycle library

Experimental Investigation Of An ORC System For A Micro-Solar Power Plant

Because of the depletion of fossil fuels and global warming issues, the world energy sector is undergoing various changes toward increased sustainability. Among the different technologies being developed, solar energy, and more specifically CSP (Concentrated Solar Power) systems are expected to play a key role to supply centralized loads and off-grid areas in the medium-term. Major performance improvements can be achieved by implementing advanced control strategies accounting for the transient and random nature of the solar heat source. In this context, a lab-scale solar power plant has been designed and is under construction for experimental purposes and dynamic analyzes. The test rig includes an ORC unit, a field of parabolic trough collectors and a thermal energy storage. This paper presents the results of an experimental campaign conducted on the ORC module alone. This power unit, designed for a 2.8 kW net electrical output, consists of two scroll expanders in series, an air-cooled condenser, a recuperator, a volumetric pump and an oil-heated evaporator. The ORC engine is constructed using standard mass manufactured components from the HVAC industry, this practice reducing considerably the system cost. The overall unit performance and components effectiveness are presented in different operating conditions and relevant empirical correlations are derived to be implemented in a steady state model of the ORC unit

Effects of the Working Fluid Charge in Organic Rankine Cycle Power Systems: Numerical and Experimental Analyses

It is well known that organic Rankine cycle (ORC) power systems often operate in conditions differing from the nominal design point due to variations of the heat source and heat sink conditions. Similar to a vapor compression cycle, the system operation (e.g., subcooling level, pump cavitation) and performance (e.g., heat exchanger effectiveness) of an ORC are affected by the working fluid charge. This chapter presents a discussion of the effects of the charge inventory in ORC systems. In particular, both numerical and experimental aspects are presented. The importance of properly predicting the total amount of working fluid charge for optimizing design and off-design conditions is highlighted. Furthermore, an overview on state-of-the-art modeling approaches is also presented

From 1885 To Nowadays: A (Short) Techno-historical Review Of Solar Organic Rankine Cycle Systems

peer reviewedSince the first solar ORC system built by Charles Tellier in 1885, hundreds of solar ORC systems have been imagined, built, tested, operated and, in most cases, abandoned along the past century. Aiming to emphasize the technical maturity of these existing but yet little-known works, this paper presents some of the most innovative technological developments of SORC thanks to six existing examples. These systems have been selected to cover various sizes, technology and applications, from the end of XIXth century to nowadays