A Purely Mechanical Energy Storing Concept for Hybrid Vehicles
The paper contains the design and simulation of a purely mechanical system for storing energy during vehicle deceleration, which can be utilized during subsequent acceleration (regenerative braking). A continuously variable transmission (CVT) regulates the energy transfer, energy storage is accomplished by means of a spiral spring and additional use of a planetary transmission. The transmission ratio of the CVT is adapted by a combined feed-forward and feed-back control. A computer simulation for a vehicle with an overall mass of 1500kg, and an energy storage capacity of 30kJ was performed for different driving cycles. In a typical urban stop and go situation the proposed device will save up to 0.72kg fuel per 100km and the overall efficiency analysis together with simple design, easy recycling, and long life expectance, showed a clear advantage over other hybrid concepts for frequent stops and accelerations.
An electro-mechanical braking energy recovery system based on coil springs for energy saving applications in electric vehicles
Abstract Regenerative braking system is a promising energy recovery mechanism to achieve energy saving in EVs (electric vehicles). This paper focuses on a novel mechanical and electrical dual-pathway braking energy recovery system (BERS) based on coil springs for energy saving applications in EVs. With the aims of maximizing energy recovery efficiency, mechanical and electrical recovery strategies are respectively employed under two different brake situations of inching braking and emergency braking. This system mainly consists of three parts, including the mechanical module, electrical module and control module. The mechanical module utilizes coil springs to store the kinetic energy in the form of elastic potential energy which can be utilized to provide a part of the starting torque for EVs. The electrical module enables recovery of the braking energy into the vehicle battery. The control module controls the mechanical module and the electrical module to work coordinately to select an appropriate energy recovery pathway under different braking modes. A full-size prototype, manufactured and based on this design, is introduced. Simulations and experiments of the proposed regenerative braking system are conducted to verify the system. Auxiliary starting torque of 12.7 N m, maximum voltage of 3.5 V and total energy recovery efficiencies of 0.53 can be obtained, verifying that the proposed braking energy recovery system is effective and beneficial for vehicle energy savings.
Coulombic efficiency of a sealed, thin plate, spiral lead-acid battery
Optima Advanced Technologies has developed prototype 15 Ah valve regulated, sealed, thin plate spiral lead-acid batteries for hybrid electric vehicle applications. These batteries were evaluated for coulombic efficiency using charge rates ranging from 1.5 A to 24 A. Pressure and temperature data were also collected, to investigate gassing behavior unique to valve regulated lead-acid batteries. Unlike conventional thick plate traction batteries, this battery had coulombic efficiencies as high as 98% for 100% charge replacement, making it desirable for hybrid applications. Both coulombic and energy efficiency decreased as the charge rate increased, as might be expected. The energy efficiency decrease was greater than the coulombic efficiency due to polarization effects. The characteristic voltage peak near the end of the charge was found to correlate closely with the pressure behavior. At low charge rates, the pressure stays below the cracking pressure of the valve, indicating that the peak in pressure observed is due to gassing and recombination, rather than venting.