Waste heat to power vehicles
Approximately 60 % of combustion energy in a conventional internal combustion engine is lost as waste heat through exhaust gases and the cooling system. A thermodynamic cycle such as the Rankine cycle could theoretically be used to enhance engine efficiency by up to 20 %. The Rankine cycle converts heat into electricity by exploiting vaporisation, expansion and condensation of a working fluid in a closed loop. The NOWASTE (Engine waste heat recovery and re-use) project developed this technology to satisfy automotive requirements without compromising vehicle design and performance. Benefits were even greater when integrated with a hybrid or hybrid-like powertrain that enabled the energy to be stored and used on demand. Researchers used heavy-duty trucks with electric auxiliaries, one Volvo and one Iveco, to demonstrate the technology and expected an overall increase of between 12 and 15 % in vehicle energy efficiency. Project partners made significant progress towards design, procurement and integration of components for testing with associated test benches. They developed new models of system components and the vehicle thermal management system, and designed Rankine cycle components (boiler, condenser, expander and pump). In addition, there was an increased understanding of the system design and its integration into a heavy duty vehicle application. All the integration aspects were considered, including on-board energy management to maximise the benefit of the system. NOWASTE was characterised by the high level of the heat recovery system integration with the engine and the exhaust system especially in transient and part-load conditions. Project partners also adopted a new solution to improve the heat rejection that minimises the impact in the cooling drag and developed innovative control strategies. Moreover, researchers conducted a computer-aided design study of the overall organic Rankine cycle system geared toward the test bench installation for the two applications. This resulted in development of the test bench for one of the vehicles and of an integrated system prototype for the other one. Experimental tests of the two systems have taken place. Finally, the team conducted a preliminary cost estimation and technology feasibility evaluation. Waste heat recovery from fossil fuel combustion for conversion into electricity to power auxiliaries or hybrid powertrains could substantially reduce fuel consumption for major impact on emissions. NOWASTE successfully developed the necessary components and systems required for the efficient and eco-friendly utilisation of energy in the road transport sector.
Keywords
Rankine cycle, NOWASTE, heat recovery system, engine system, on-board energy management, computer-aided design, waste heat recovery, energy efficiency, CO2 reduction
