University of South Wales Master of Sciences Thesis
Power density/Specific power
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- Điều hướng trang này:
- Durability (cycling capacity)
- Self-discharge
| Power density/Specific power: is a measure of how much power can be extracted from a battery per
unit of battery weight or volume. Autonomy: This variable is defined by the ratio of restorable energy capacity to maximum power discharge [17]. It refers to the maximum amount of time the system can continuously release energy. The autonomy of a system depends on the type of storage and the type of application. 2.35 Durability (cycling capacity): Energy storage system is designed to release the energy stored after each recharge in a fixed time. The number of times the energy storage can release the energy level it was designed for after each recharge is referred to as durability or cycling capacity. It is expressed in Standalone hybrid generation system for the remote area of Thar, Pakistan number of cycles, N-cycles. The cycling capacity mainly depends on the depth of discharge. Figure 2- 22 below shows the number of cycles versus the DOD of VRLA14 batteries. Figure 2.22: Cycling capacity Vs depth of discharge for lead-acid battery [19, 20] The higher the DOD, the lower will be the cycles and the lifetime of the batteries (can be seen from Figure 2-22). The battery cycles depend on the DOD and EOL [6]. 2.36 The smaller the DOD, the more cycles can be provided by the battery but not in a linear relationship because of the EOL criterion. The EOL, in general, is a decrease of 80% of its capacity [6, 17]. The normal capacity needed can then be given [6] as: 2.37 Self-discharge: This refers to the portion of energy which was initially stored and dissipated in a given non-use period of time. There are different types of batteries, but the most commonly used rechargeable batteries are [6, 11, 17]: - Lead acid battery - Nickel cadmium (NiCad) battery - Nickel metal hydride (NiMH) battery - Lithium ion battery - Lithium-polymer battery - Zinc-air battery The main properties with their main application, the advantages and disadvantages of each these batteries are explained in [6, 11]. |