ABSTRACT A new concept hybrid vehicle is introduced based on energy substitution. This is best realised in a Supercharger Air Hybrid Vehicle (SAHV) which uses a supercharger-tank- engine energy chain for regenerative braking. In the SAHV, a supercharger is added to a vehicle with a fully developed highly boosted downsized engine, and its main function is to act as a vehicle brake. The SAHV uses braking energy to drive the supercharger instead of using engine energy to drive a turbocharger to produce an equivalent amount of boost air which is stored temporarily in a low pressure air tank. This provides regenerative boost to the engine for free for short periods during accelerations after braking. At the same time the saved engine energy is available fully to drive the vehicle. This process represents 90+% recovery of the captured braking energy when the saved engine energy is returned to the vehicle, which is equivalent to the braking energy captured earlier by the supercharger. INTRODUCTION Conventional hybrid vehicles work by energy conversion. The best example is the Hybrid Electric Vehicle (HEV) which uses a generator-battery-motor energy chain to achieve regenerative braking. In the HEV, braking energy is first converted into electricity by an electric generator, then stored as chemical energy in a battery, later released as electricity, and finally converted back to mechanical energy by an electric motor. Each energy conversion stage will incur some losses so that the final regenerative efficiency is typically only 60%. The SAHV could be more efficient in regenerative braking than the HEV. It also uses a simple air tank for energy storage with lower lifecycle CO 2 than the HEV, avoiding the production and disposal CO 2 cost of chemical batteries.This paper describes the generic principle of regenerative braking by energy substitution. It further identifies eight key design guidelines which can be scaled and applied in a wide range of engines and vehicles including all turbocharged and supercharged diesel, petrol, bio-fuel and CNG engines in cars, vans, buses and trucks. REGENERATIVE BOOST BY ENERGY SUBSTITUTION The principle of regenerative boost by energy substitution is shown in Figure 1. Starting from the bottom, a standard engine is replaced a highly boosted downsized engine. The standard engine will be able to satisfy the acceleration power demands of the vehicle but is oversized and inefficient for low load cruising conditions. The downsized engine is designed to meet the low load cruising demand of the vehicle at a higher efficiency but requires an air boost to produce more power for accelerations. This air boost is normally supplied by an air charger which may be a turbocharger or supercharger or both. In the SAHV, an existing supercharger or an added supercharger is used separately for regenerative braking. Braking energy is used as a substitute for engine energy for driving the supercharger to produce boost air which is stored in a low pressure air tank. An equivalent amount of energy (including efficiency losses) is saved when the downsized engine is later boosted from the air tank in substitution of the supercharger and other air chargers which are temporarily switched off, providing boost for a short time without taking energy from the engine. Supercharger Air Hybrid Vehicle2010-01-0822 Published 04/12/2010 Tom Ma and Jon Ma Ma Innovation Ltd. Copyright © 2010 SAE InternationalDownloaded from SAE International by University of Minnesota, Thursday, August 02, 2018Figure 1. Principle of energy substitution In Figure 1, because the air charger and the supercharger have similar efficiencies operating during braking and during driving, they draw the same amount of energy from the respective energy sources and produce the same amount of boost air so that the two sources of energy are equivalent and interchangeable. This method of energy substitution has theoretically 100% regenerative efficiency when the subs