Libertine Waste Heat Recovery Unit

  • Morgan, Robert (PI)

Project Details


This project provided a demonstration of a commercially viable exhaust heat recovery system for trucks, running in test at 20kWe, working with partners Libertine FPE and Nidec SR Drives.

The global market for commercial vehicles was expected to exceed 20 million units per annum by 2015 (Global Industry Analysts Inc. 2011). The Automotive Council's low carbon technology roadmap for commercial vehicles had identified a specific need for technologies to improve thermal efficiency focused on using waste exhaust and coolant heat - particularly for higher duty commercial vehicles - in the period to 2025 and potentially beyond.

This 2013-15 project sought to research and develop a novel free piston expander based waste heat recovery system aimed at the commercial vehicle market. The free piston expander offered efficiency and cost benefits over conventional turbine and screw expanders, impacting positively both on the initial investment cost of the system and potential returns to the end user. Improvements to the business case for waste heat recovery would significantly increase market uptake of the technology in the commercial vehicle market and reduce CO2 emissions from the sector.

The claimed benefits of the free piston expander were realised both through novel manufacturing methods for the Libertine technology and the inherent characteristics of a free piston expander. The Libertine device could be manufactured from extrusions, significantly reducing the manufacturing cost of the device. The device also integrated an electrical machine in the barrel of the expander that improves power conversion efficiency and the controllability of the device.

Simulation indicated that the free piston expander technology gave the opportunity to use high expansion ratios, possibly with some condensation of the working fluid. These features allowed a wider selection of working fluids, better matched to the available thermal energy from the vehicle internal combustion engine cooling and exhaust system. The Libertine free piston expander therefore offered potential benefits compared to screw and turbine expanders in matching the heat recovery system to the available thermal energy, improving both power output and conversion efficiency.

The project aimed to quantify through simulation, and then validate through hardware, the benefits of a free piston based waste heat recovery system applied to a commercial vehicle platform. This was to include both technical and commercial performance in the target application. The work would focus on a 20kWe output device, of a suitable size for implementation on a commercial vehicle.

The objectives of the University of Brighton's contribution to the project were:
> To research, through simulation, the performance potential of a free piston expander based waste heat recovery system, including working fluid selection and system configuration
> Working with the other partners, to optimise the system and free piston mechanical and electrical component design to deliver the optimal solution in terms of efficiency, package and cost
> To design and procure a test rig based on the optimal configuration
> To undertake a development and validation programme using the test rig to validate system models and prove the concept.

The research programme incorporated a number of activities with potential for improved energy conversion efficiency, new collaborations and training. This would lead to:
> removing market barriers to using this novel technology;
> taking a step towards realising a free piston combustion engine;
> reducing C02 emissions;
> increasing market share and profit to UK industrial collaborators;
> training and enthusing the next generation of British engineering;
> broadening the research activities at the Centre for Automotive Engineering.

The beneficiaries of this work are primarily the industrial partners (Libertine and Nidec SR Drives Ltd) in supporting the development and commercialisation of their novel technology. The research therefore supported new hi tech industry, promoting economic activity within the UK and boosting export revenues. The potential reduction in CO2 emissions from successful commercialisation of the technology would benefit the road haulage industry through reduced operating costs and society as a whole in reducing greenhouse gas emissions.
Effective start/end date1/10/1330/06/15


  • TSB


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