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Highlights:• Multi objective optimization is applied for optimal hybrid electric powertrain designs.• A holistic approach for optimal design and control strategies is presented on vehicle usages.• Hybrid electric vehicles can reach large range of efficiency -26% to 45%.• Hybrid electric vehicle can emit very low CO 2 emissions -30 g/km for D class vehicles. Abstract:The improvement of the efficiency of vehicle energy systems promotes an active search to find innovative solutions during the design process. Engineers can use computer-aided processes to find automatically the best design solutions. This kind of approach named "multi-objective optimization" is based on genetic algorithms. The idea is to obtain simultaneously a population of possible design solutions corresponding to the most efficient energy system definition for a vehicle. These solutions will be optimal from technical and economic point of view. In this article this kind of "genetic intelligence" is tested for the holistic design of the optimal vehicle powertrain solutions and their optimal operating strategies.The methodology is applied on D class hybrid electric vehicles, in order to define the powertrain configurations, to estimate the cost of the powertrain equipment and to show the environmental impact of the technical choices. The optimal designs and operating strategies are researched for different vehicle usages -normalized, urban and long way driving. Introduction:

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6Highlights:The hybrid pneumatic powertrain is an alternative solution for hybridization. 8• The main advantages are the low cost and the direct transmission of the torque. 9• The hybrid pneumatic powertrain suits for urban driving and mild hybridization. 10• An efficiency improvement of 50% is reached for urban driving and C Segment vehicle. 11• The CO2 emissions on the urban cycle are very low -only 51 g CO2/km. 13Abstract: 14The largest applied convertors in passenger cars are the internal combustion engines -gasoline, diesel, adapted 15 also for operating on alternative fuels and hybrid modes. The number of components that are necessary to realize 16 modern future propulsion system is inexorably increasing. The need for efficiency improvement of the vehicle 17 energy system induces the search for an innovative methodology during the design process. 18In this article the compressed air is investigated as an innovative solution for hybridization of small gasoline 24The hybrid pneumatic concept is applied on a largely deployed C Segment commercial vehicle with 3 cylinder 25 gasoline engine. The lowest fuel consumption results are investigated on the usage of this vehicle. 26Key words: 27Hybrid pneumatic engine, Vehicle hybridization, ICE efficiency 29Nomenclature: 30 CV Charge Valve 31 CVT Continuously Variable Transmission 32 HPE Hybrid Pneumatic Engine 33 HPP Hybrid Pneumatic Powertrain 34 ICE Internal Combustion Engine

Highlights:• The hybrid pneumatic powertrain is efficient for urban usage • Organic rankine cycle suits for peri-urban and holiday drives and downsized engines • Both technologies combine efficiently on combined driving cycles Abstract:This article presents an innovative concept for alternative mild hybridization. The concept is studied on a CSegment vehicle. Short term hybrid pneumatic energy storage and a waste heat recovery system are introduced for the efficiency improvement of a small downsized gasoline engine. The modelling methodology for the hybrid pneumatic powertrain is presented. The waste heat recovery system is an organic rankine cycle. An innovative methodology using energy integration and multi-objective optimization is applied for the design of the organic rankine cycle loop. The selection of the organic rankine cycle design is based on techno-economic indicators and is done by using a qualification utility function for the population of solutions on the Pareto curve. The concept of hybrid pneumatic powertrain and organic rankine cycle is evaluated on different driving cycles and the economic analysis of the customer mobility is done, according to his drive profile.