Andrew Burke

Ultracapacitors: why, how, and where is the technology

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Batteries and Ultracapacitors for Electric, Hybrid, and Fuel Cell Vehicles

The application of batteries and ultracapacitors in electric energy storage units for battery powered (EV) and charge sustaining and plug-in hybrid-electric (HEV and PHEV) vehicles have been studied in detail. The use of IC engines and hydrogen fuel cells as the primary energy converters for the hybrid vehicles was considered. The study focused on the use of lithium-ion batteries and carbon/carbon ultracapacitors as the energy storage technologies most likely to be used in future vehicles. The key findings of the study are as follows. 1) The energy density and power density characteristics of both battery and ultracapacitor technologies are sufficient for the design of attractive EVs, HEVs, and PHEVs. 2) Charge sustaining, engine powered hybrid-electric vehicles (HEVs) can be designed using either batteries or ultracapacitors with fuel economy improvements of 50% and greater. 3) Plug-in hybrids (PHEVs) can be designed with effective all-electric ranges of 30-60 km using lithium-ion batteries that are relatively small. The effective fuel economy of the PHEVs can be very high (greater than 100 mpg) for long daily driving ranges (80-150 km) resulting in a large fraction (greater than 75%) of the energy to power the vehicle being grid electricity. 4) Mild hybrid-electric vehicles (MHEVs) can be designed using ultracapacitors having an energy storage capacity of 75-150 Wh. The fuel economy improvement with the ultracapacitors is 10%-15% higher than with the same weight of batteries due to the higher efficiency of the ultracapacitors and more efficient engine operation. 5) Hybrid-electric vehicles powered by hydrogen fuel cells can use either batteries or ultracapacitors for energy storage. Simulation results indicate the equivalent fuel economy of the fuel cell powered vehicles is 2-3 times higher than that of a gasoline fueled IC vehicle of the same weight and road load. Compared to an engine-powered HEV, the equivalent fuel economy of the hydrogen fuel cell vehicle would be 1.66-2.0 times higher

An assessment of electric vehicles: technology, infrastructure requirements, greenhouse-gas emissions, petroleum use, material use, lifetime cost, consumer acceptance and policy initiatives.

Concerns about climate change, urban air pollution and dependence on unstable and expensive supplies of foreign oil have led policy-makers and researchers to investigate alternatives to conventional petroleum-fuelled internal-combustion-engine vehicles in transportation. Because vehicles that get some or all of their power from an electric drivetrain can have low or even zero emissions of greenhouse gases (GHGs) and urban air pollutants, and can consume little or no petroleum, there is considerable interest in developing and evaluating advanced electric vehicles (EVs), including pure battery-electric vehicles, plug-in hybrid electric vehicles and hydrogen fuel-cell electric vehicles. To help researchers and policy-makers assess the potential of EVs to mitigate climate change and reduce petroleum use, this paper discusses the technology of EVs, the infrastructure needed for their development, impacts on emissions of GHGs, petroleum use, materials use, lifetime costs, consumer acceptance and policy considerations.

The present and projected performance and cost of double-layer pseudo-capacitive ultracapacitors for hybrid vehicle applications

The performance of carbon/carbon double-layer and pseudo-capacitive ultracapacitors are assessed based primarily on testing done in the laboratory at UC Davis. The useable energy density of commercially available carbon/carbon devices is between 3.5 and 4.5 Wh/kg. The corresponding power density for high efficiency (95%) discharges is between 800-1200 W/kg. The pseudo-capacitive devices have higher energy densities in the range of 10-13 Wh/kg for constant power discharges less than 500 W/kg, but the energy density decreases significantly at higher power densities. Projections of future development indicate that the energy density of the carbon/carbon devices will increase to 5-6 Wh/kg in the relatively near future along with higher power densities of 1500-3000 W/kg. In the case of the pseudo-capacitive approaches, the carbon/PbO/sub 2/ device looks particularly promising from both the performance and cost points-of-view primarily because of its relationship to the low cost lead-acid battery. Costs of the carbon/carbon ultracapacitors are expected to continue to decrease from the present costs of 2-3 cents/Farad to about 0.5 cents/Farad. Further reductions in cost require a low cost carbon of

Prospects for ultracapacitors in electric and hybrid vehicles

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The Continued Design and Development of the University of California, Davis FutureCar

10/kg. Comparisons of the costs of ultracapacitor and battery energy storage units for mild hybrid vehicles depend critically on the energy storage requirement (Wh) assumed for the ultracapacitor unit. If the storage requirement is less than 100 Wh, there is a strong possibility that ultracapacitors can compete with nickel metal hydride and lithium-ion batteries in the future hybrid vehicles.

Present and future applications of supercapacitors in electric and hybrid vehicles

The prospects for ultracapacitors for use in electric and hybrid vehicles in the near-term (within five years) are discussed based on the present status of the technology world-wide and the characteristics of devices that are available for purchase or in an advanced state-of-development and thus nearly ready to be marketed. The energy density (Wh/kg) of the devices presently available for purchase are too low (2.2 Wh/kg) for most vehicle applications and their price (

An intelligent solar powered battery buffered EV charging station with solar electricity forecasting and EV charging load projection functions

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Life cycle testing of lithium batteries for fast charging and second-use applications

300) is too high for even applications requiring only a small energy storage capacity (50-100 Wh). Prototype devices having an energy density of 5-8 Wh/kg are almost ready for marketing from several capacitor/battery companies. The higher energy density capacitors are carbon-based and use an organic electrolyte. They are fabricated using existing production equipment, so their price can be expected to be much lower when they are manufactured in high quantities and there are multiple sources for purchasing them. Projections of the future performance of ultracapacitors were made indicating energy densities of 10-20 Wh/kg are achievable in the relatively near-term using carbon electrode materials having specific capacitances of 150-200 F/gm.

Ultracapacitors in micro-and mild hybrids with lead-acid batteries: Simulations and laboratory and in-vehicle testing

The UC Davis FutureCar Team has redesigned a 1996 Ford Taurus as a parallel hybrid electric vehicle with the goals of tripling the fuel economy, achieving California ultra low emissions levels (ULEV), and qualifying for partial zero emissions vehicle (ZEV) credits in California. These goals were approached using a highly efficient powertrain, reducing component weight, and improving stock aerodynamics. A charge depletion driving strategy was chosen to maximize energy economy and provide substantial all-electric operating capabilities. The UC Davis FutureCar couples a Honda 660 cc gasoline engine and a UNIQ Mobility 48 kW-peak brushless permanent magnet motor within a compact, lightweight, and reliable powertrain. The motor is powered by a 15.4 kWh Ovonic Nickel Metal Hydride battery pack. The body of the vehicle has been reshaped using carbon fiber composite panels to improve airflow characteristics and reduce weight. At the 1997 FutureCar Challenge, the vehicle achieved an equivalent fuel consumption of 5.64 L/100 km (41.7 mpg) on the federal urban driving schedule and 3.74 L/100 km (62.8 mpg) on the federal highway driving schedule for a combined fuel consumption of 4.79 L/100 km (49.1 mpg). This represents a doubling of the stock vehicle’s fuel economy. Driving range exceeded 400 km on the combined driving schedules. The vehicle accelerates from 0 to 100 kph in 14.4 seconds and has an all-electric range of 105 km.