Author: admin
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Start–Stop Hybrid
As we consider the energy storage requirements for the start–stop hybrid, it is important to know the power required as a function of time. The intended driving schedule and many of the specifics for the vehicle are not needed for design of the energy storage system for this type of hybrid, since the RESS does…
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Hybrid Vehicle Architectures
There are many architectures used in hybrid systems. We will not attempt to cover them extensively; rather, our objective is to review some typical architectures and to provide a broad overview of terminology. In subsequent sections, we will explore in more detail electrochemical devices for energy storage for specific hybrid architectures. Because there are many…
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Battery Electrical Vehicle
We begin our discussion of vehicles by first exploring the use of a battery to store energy for an all-electric vehicle. In a battery electric vehicle (BEV), the battery provides all of the power and energy needs. As mentioned earlier in the chapter, here are three key aspects to sizing the battery: energy capacity, power,…
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Regenerative Braking
Before turning to specific vehicle architectures, we pause to consider regenerative braking, which plays an important role in increasing hybrid vehicle efficiency. A key benefit of the vehicle strategies considered in this chapter is that kinetic and potential energy can be recovered during braking. Clearly, energy is required to accelerate a vehicle to a higher…
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Driving Schedules and Power Demand in Vehicles
In evaluating powertrain systems, the vehicle speed is often prescribed as a function of time. This relationship is generalized with a driving schedule. Figure 12.3 provides such a relationship for an urban dynamometer driving schedule, one of many standardized schedules that are available. This plot shows speed versus time for the vehicle driven in an…
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Why Electric and Hybrid-Electric Systems?
A key feature of systems that include energy storage is that excess energy can be accumulated for later use. Our focus will be on vehicles, but applications for hybrid power systems are common. For example, a renewable energy system based on wind power alone will struggle to match electrical power production and demand. What do…
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Pseudo-Capacitance
Other than self-discharge, our discussion of EDLCs has not involved faradaic reactions; that is, we have assumed that no charge is transferred across the double layer, and that there is no change in oxidation state due to reaction. The resulting current–voltage behavior is purely capacitive and would approximate the ideal box shown earlier in Figure 11.9. The…
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Cell Design, Practical Operation, and Electrochemical Capacitor Performance
Construction of a typical cell sandwich for an EDLC is shown in Figure 11.18. The differences in how energy is physically stored aside, these EDLCs have many similarities to batteries, two porous electrodes coated onto current collectors and separated by an electrolyte. The cell designs are similar too. Typical configurations for EDLCs include cylindrical, prismatic, button,…
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Power and Energy Capabilities
Both the energy and power density are important characteristics of capacitors, and are considered in this section. The change in energy associated with a change in capacitor voltage is (11.36)The total energy stored in the capacitor can be obtained by integration (11.37)where we have assumed that C is constant. Recall that capacitance has units of…
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Impedance Analysis of EDLCs
In this section, we apply impedance spectroscopy to electrochemical double-layer capacitors in order to gain insight into their transient behavior. Additionally, we use the impedance results as a basis for a simplified EDLC model that will facilitate our analysis of these devices. Analysis for Highly Conductive Solid PhaseIn order to use impedance to examine the…