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Engine Waste Heat Recovery and Re-Use

Final Report Summary - NOWASTE (Engine Waste Heat Recovery and Re-Use)

Executive Summary:
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 30-40% of the fuel indicated energy is still lost through 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. The heat re-use performed by means of thermodynamic cycles using the waste heat as a source of energy (as is already being developed for application in large stationary applications) and transforming it into mechanical or electrical energy can increase the overall vehicle energy efficiency directly. The adoption of such a 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, University of Liège, AVL List GMBH, Faurecia systèmes d’échappement SAS.
This project aims at developing a waste heat recovery system based on Organic Rankine Cycle (ORC) for a Heavy Duty Truck (HDT) application with the aim to realize fuel economy savings. The target applications have been chosen among the IVECO and VOLVO fleets.
The NoWaste Project shall demonstrate waste heat recovery system feasibility within both a purpose-built test rig and a vehicle demonstrator.
The key points are:
• definition of a reference mission;
• selection of the most appropriate architecture following an in-depth technology screening;
• innovative heat rejection system minimizing the cooling drag and the impact on the front end;
• development of specific heat exchangers to maximize the heat recuperation efficiency;
• integration with the exhaust system;
• validation of the developed system initially on a test rig and then on vehicle demonstrator based on a hybrid powertrain;
• evaluation of the system applicability on various missions via simulation.
The target performances are:
• Fuel Economy: ~5% fuel consumption reduction at vehicle level on a reference mission
• Cost (for the OEM): < 4500 Euro/system
• Weight: < 150 kg

Project Context and Objectives:
Despite recent improvements of diesel engine efficiency, a considerable amount of energy is still rejected as heat both in the exhaust gases and from the cooling system. The amount of waste energy is in the order of 50–60% of the combustion energy. This energy, in form of heat at high, medium and low temperatures, can be re-used and transformed into more useful forms, e.g. electricity.
The transformation of medium temperature heat into mechanical energy and then into electricity can be performed by means of a thermodynamic cycle typically with an efficiency level ranging from 10% up to 20% depending on the temperature level, on the thermodynamic cycle selected, and on the specific technology adopted.
This approach is well known and has already been applied in the domain of large stationary power plants where thermodynamic cycles are implemented so as to exploit the heat produced and available
at the bottom of the primary process, thus increasing the overall efficiency of energy production (bottoming cycle).
Applying the same technology in the automotive domain, initially to heavy trucks, enables the overall vehicle efficiency to be increased by up to 20 % in theory. However, to achieve this goal, a new generation of components and systems should be developed for automotive applications which are fully compliant in terms of dimensions, energy, weight, cost, and environmental constraints as is required for such applications. Then, smart solutions should be identified to integrate the heat re-use system with the engine, the exhaust line and other vehicle subsystems in order to minimize the impact on vehicle performance and cooling drag.
Finally, to achieve a higher efficiency level, the most suitable vehicle powertrain and on board energy management solutions should be identified to enable the energy to be produced when the heat is available, and then storing and re-using it when most convenient. The key points of the waste heat recuperation, that also represent main challenges of NoWaste, are:
• the development of a thermodynamic cycle and component to re-use the vehicle waste that is compliant with the automotive constraints;
• minimization of the impact on the vehicle architecture and performance;
• cost sustainability;
• technology feasibility;
• compliancy with the current and forthcoming regulations regarding greenhouse gas emissions and environmental impact.
The purpose of the NoWaste Project is to improve the vehicle fuel economy increasing the overall vehicle energy efficiency thanks to an innovative system capable of recovering and re-using the waste heat by transforming it, by means of a thermodynamic cycle called Rankine Cycle, into useful energy.
The Rankine cycle is a thermodynamic cycle which converts heat into work. The heat is supplied externally to a closed loop, which usually uses water or an organic fluid as the working fluid. The Rankine Cycle System can be operated on the exhaust gases of the Internal Combustion Engine. The system is composed of four/five different components: Exhaust gas heat exchanger, expander (+generator), pump, and the condenser. The mechanical energy produced by the expander machine can be directly used as powertrain power or it can be transformed into electrical energy, hence contributing positively to the overall energy balance considering a reference vehicle with a medium-high level of electrification.
The system will be integrated on an engine for testing and experimental validation, initially at the bench level, and then a second unit will realized and installed on a heavy duty truck with hybrid e power-train and electrified auxiliaries.
All the integration aspects will be considered including the on board energy management in order to maximise the benefits of the system.
To address the challenges related to the development and application of a bottoming cycle in the automotive domain the NoWaste project is characterised by:
• the high level of integration of the heat recovery system with the engine and the exhaust system, especially in transient and part-load conditions;
• the adoption of a new solution based on low temperature coolant circuit in order to avoid that the higher heat rejection demand increases the size and pressure drop (air side) of the front thermal module causing a negative impact on the vehicle aerodynamics (higher cooling drag);
• the development of innovative control strategies;
• the integration with a vehicle equipped with electrified auxiliaries;
• a compact unit which incorporates the expander, the high pressure pump and the generator.
The reference application (baseline commercial vehicle) considered is a Euro 6 diesel engine (e.g. 500 HP/372 kW) and the related 4x2 tractor. The baseline engine as the vehicle will be fully characterised following the procedure identified in the first part of the Project and these data will be considered the reference again which the project results will be compared. At first the comparison will be made virtually, by means of the mathematical models that will be developed within the project. These data will be continuously refined and updated after having acquired the data coming from the components and subsystems evaluation at first and then after the system experimental validation at bench level is completed. Finally the data collected on the prototype vehicle will be compared with the reference data.
The main performance indicators that will be used to measure in the project results can be summarized as follows:
Technical Indicators
• Overall Rankine System Efficiency: Generated Energy (Watt) / [Absorbed Heat(Watt) + Energy required by auxiliaries of the Rankine system (watt)
• Vehicle Fuel Economy: [NoWaste validation vehicle fuel consumption (l/100 km)-Reference fuel consumption]. The data will be measured following the procedure identified in the WP1
• System Cost estimation as cost variation from reference engine and reference vehicle.

Other Indicators
• Number of published papers;
• Number of presentation during international acknowledged event.

Project Results:
The No Waste project plan was divided into six main WorkPackages (WP).
Covering theoretical and numerical studies on innovative technologies in the very first project phase allowed to evaluate those concepts and to make a decision on waste heat recovery system architecture to be developed and tested on the engine test bench and on the vehicle.
This very first project phase was extended over one year. After having defined the system boundary conditions two work packages covered investigations on possible heat recovery and rejection architectures using steady state thermodynamic simulation models. A specific working fluid analysis has covered all aspects beside the thermodynamic analysis of working fluids and investigated on innovative mixtures and fluids properties further used in the architecture definition analysis.
After six months after start a pre-decision was taken regarding possible concepts and working conditions of the waste heat recovery system. Once the heat recovery and heat rejection systems were defined a detailed numerical simulation model in a 1D-environment of the waste heat recovery system was modelled to evaluate the system performance for steady-state and transient conditions. When the system was defined, components and control strategies were developed in work package two. The components were first tested separately before being installed as a whole waste heat recovery system on an engine test bench.
The choice of the expansion device was considered very important for efficient power recuperation and transmission and depends mainly on the working fluid, system architecture and cycle conditions.
The development work within the partners of this project was then focused on the integration and adaptation to the cycle and engine as well as validation of the component. The heat exchanger technical specifications were made by the project partners. Depending on the architecture of the cycle it was planned to work together with the most experienced suppliers for the specific component development.
Further development concerning integration and validation were done by the project partners.
Therefore the WP1 was fully devoted to the system specification and target performance definition and the WP2 was focused on the system component development and prototyping.
In WP3 a first engine test bench installation was used for the optimisation of the control strategy and the optimisation of the system working conditions on steady state working points. In a second step the system was installed on an engine test cell that represents realistic engine environment conditions. Here the system was tested on engine test cycles before being installed on a vehicle.
An on-board unit was planned to be realized and experimentally tested in the WP4, the activity includes the NoWaste system on board installation and its functionality and performance analysis and validation.
To promote the results exploitation and to ease the NoWaste system industrialisation complete work package (WP5)was devoted to the system cost estimation and technology feasibility evaluation. The WP were intended to be run along all the project duration so to drive the development and the technical decision so to achieve acceptable system cost assuring that the results could be rapidly industrially exploited. Finally the WP6 was concerned with dissemination and exploitation, and will ensure that the results of the project are known to and used by a wide audience.

Potential Impact:
The main achievements of the No Waste Project can be summarized as:
• a relevant improvement in respect of the understanding of the system design and its integration on a heavy duty vehicle application;
• an increased motivation of the components’ suppliers in the investment on specific component development;
• an increased motivation of the OEM involved in the project, but also other ones for internal investment on ORC developments;
• a new synergy of the OEM working on this topic that has driven the suppliers to increase their effort in the development of new and specific components;
• a demonstrated energy saving realized on the considered applications through a waste heat recovery system based on the ORC technology.
Exploitation will ensure that the results of the NoWaste project are known to and used by a wide audience. This process is a key for the success of the project. Therefore one of the main exploitation principles will be to publish the project results.These papers must be aligning with the business requirements of each partner of the consortium.

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