%0 Journal Article
%T A Power Buffer in an Electric Driveline: Two Batteries Are Better Than One
%A Juan de Santiago
%A Florian Burmeister
%A Johan Lundin
%A Janaina G. Oliveira
%J ISRN Automotive Engineering
%D 2014
%R 10.1155/2014/525630
%X Fuel cells and high energy density batteries have limited overrated capacity and slow power response. Ultracapacitors and flywheels are proposed to overcome these limitations and to facilitate regenerative braking in hybrid and electric vehicles. The simulations presented in this paper show that a Secondary Energy Storage Unit (SESU) enhances the performance of the drivelines as previously suggested and provides additional improvements. A combined design of the primary energy source and the SESU reduces the total weight and volume and increases the battery lifetime. A full-electric driveline is simulated using a standard EPA FTP-75 drive cycle. Then the same vehicle is simulated with as SESU and the results are compared. The same is done for a hybrid driveline. Two drivelines are used as references and then enhanced with an SESU; four simulations are presented in total. Simulation results show that an energy storage device with very low energy and high power allows better battery selection and energy management. 1. Introduction Research in electric vehicles has a long history full of success and disappointment. There are great expectations that are fulfilled only recently with the latest developments in batteries. Batteries are the most challenging component of the electric car. Energy density is very low compared to gasoline. Electric cars have less range than gasoline as batteries become very heavy. Most commercial electric cars are intended for commuting purposes with an average range of less than 160£¿km [1]. The Tesla Model is the commercial electric car with higher range up to 480£¿km (300 miles) and the battery alone weighs 600£¿kg [2]. The battery is also an expensive component. Different forecasts agree that the price of future electric cars will be at least $5,000 higher than conventional petrol cars even with scale economies [3]. The power and energy density is a compromise of the reagents density. There are batteries with high power density, but their energy density is limited. There are batteries with high energy density, but the power density is compromised. A Secondary Energy Storage Unit (SESU) has been proposed to improve the dynamic response of drivelines [4, 5]. This paper argues that SESUs have a positive economic potential when the complete driveline is evaluated. A power buffer is here defined as a component that can provide high power for short periods of time without compromising its lifetime. The power buffer would not be the main energy source but work in combination with Internal Combustion Engines (ICEs) or batteries.
%U http://www.hindawi.com/journals/isrn.automotive.engineering/2014/525630/