Strategic objectives adressed:
The reduction of CO2 emission is a strategic goal of the EU where heavy duty vehicles can contribute in a relevant way.A very promising solution is the re-use of the waste heat, which is about the 60% of the combustion energy, transforming it in mechanical or electrical energy so to increase in overall vehicle energy efficiency and consequently its CO2 emissions and fuel consumption of about the 10% - 15% depending of the usage conditions. This benefit can be increased in case of a hybrid or hybrid-like powertrain where it is possible to store and then use the generated energy when is more convenient.The heat re-use can be performed by means of a thermodynamic cycle (e.g. organic or non-organic Rankine cycles) using the waste heat as energy source as is being adopted for large stationary applications. The adoption of such technology in the automotive domain requires a specific R&D activity to develop the components, identify the most appropriate system architecture and integration level so to achieve sustainable cost and the reliability requirements.
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, even if it is in form of high, medium and low temperature heat can be re-use and transformed in more useful forms as, for example, electricity. The transformation of medium temperature heat in mechanical energy and then in electricity can be performed by means of a thermodynamic cycle with an efficiency level ranging from 10% up to the 20% depending on the selected thermodynamic cycle, on the adopted technology and obviously on temperature level.
This approach is already well known and applied in the domain of large stationary power plants (bottoming cycle) to increase the overall energy production efficiency.
Adopting the same technology to the automotive domain, and at first to the heavy trucks involves being able to increase, theoretically, the overall vehicle efficiency of up the 20 %. However, to achieve this goal a new generation of components and system should be developed for the automotive application and so far compliant with the size (energy, weight), cost, environmental constraints of this domain of application. Then, smart solutions should be identified to integrate the heat re-use system with the engine, the exhaust line and with the other vehicle subsystems to minimize the impact on the vehicle performance and the cooling drag.
Finally, to achieve the higher efficiency level, the most suitable vehicle powertrain and on board energy management solution should be identified so to allow to produce the energy when the heat is available, to store and to re-use it when it is more convenient.
The key points of the waste heat recuperation that represent the NoWaste challenge are:
- 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 present and incoming regulation on greenhouse gas emission and environmental impact (e.g. F-Gas directive)
The waste heat recuperation and re-use in complementary to the powertrain hybridization being more effective for medium and high average cruising speed. Therefore, the purpose of the NoWaste Project is to improve the vehicle fuel economy increasing the overall vehicle energy efficiency from 12% up to the 15% thanks to an innovative system able to recover and re-use the waste heat transforming it, by means of a thermodynamic cycle, in mechanical energy. The mechanical energy will be then transformed into electrical energy contributing positively to the overall energy balance considering as reference a vehicle with an high level of electrification (i.e. electrical auxiliaries, engine boosting,…). The system will be integrated in an engine at first at tested at bench level and then installed on a vehicle demonstrator with suitable powertrain and electrified auxiliaries and experimentally validated.
The NoWaste project is devoted to the development of a thermodynamic cycle (Rankine) and related components to convert the waste heat in electricity and of its integration on an engine and then on a demonstrator vehicle.
All the integration aspects will be considered including the on board energy management to maximize the benefit of the system.
To face with 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 the heat recovery system integration with the engine and the exhaust system especially in transient and part-load conditions
- the adoption of a new solution to improve the heat rejection that minimize the impact in the cooling drag
- the development of innovative control strategies
- the integration with a vehicle having an hybrid powertrain and all the auxiliaries electrified
- compact unit integrating the expander, the high pressure pump and the generator.
- Fuel Economy: >12% fuel consumption reduction at vehicle level on a reference mission
- Cost (for the OEM): lower than 4500 Euro/system
- Weight: lower than 150 kg