ZEBRA safety

The molten salt electrolyte also contributes to the safety behavior of ZEBRA cells. The large amount of energy stored in a 700 g cell, which means about 30 kWh in a 300 kg battery, is not released suddenly as heat as be expected in a system with liquid electrodes such as the sodium sulfur cell. In the case of accidental destruction of ZEBRA cells, the sodium will react mainly with the molten salt, forming A1 sponge and NaCl. -The diffusion of the NaAICI ... 

The safety of the ZEBRA battery has been proven extensively by abuse testing overheating, overcharging, short-circuiting of battery terminals and of cell groups, crash tests on the battery itself by dropping it at 50 km h 1 onto a pole or spike, and crash tests of cars with built-in ZEBRA batteries at 50 kmh-1 [10]. The results of abuse testing prove the ZEBRA battery to be a safe battery system. 

For the calculation of free volume inside the cell, which is essential for the design of a ZEBRA cell to keep internal pressure low for safety reasons, the density of molten NaAlCl4 over the full temperature range between 160 and 600 °C should be known. Berg et al. [33] have compared these values with the literature. The densities are compiled in Table 9. 

Brieger, G. and R.D. Hunter. 1993. Uptake and depuration of PCB 77, PCB 169, and hexachlorobenzene by zebra mussels (Dreissena polymorpha). Ecotoxicol. Environ. Safety 26 153-165. 

Doherty FG, Evans DW, Neuhauser EF. 1993. An assessment of total and leachable contaminants in Zebra mussels (Dreissena polymorpha) from Lake Erie. Ectotoxicology and Environmental Safety 25 328-340. 

Zebra batteries have been subjected to a series of tests to demonstrate their ruggedness and safety. These include overcharge, short circuit, overheating and vibration and shock. Drop testing to simulate the effect of a... 

Battery safety is so important for mobile and vehicle apphcations. Especially for vehicles, on the road, accident likely becomes heavy, and the crash accident should not bring more danger by release of the energy stored in the cells. And various tests are usually conducted. In ZEBRA battery case, test results were reported. Crash of an operative battery against a pole with 50 km/h, overcharge test, overdischarge test, short circuit test, vibration test, external fire test, and submersion of the battery in water have been specified and performed [6]. The ZEBRA battery did pass all these tests owing to its four-barrier safety concept [7, 8] chemical aspects, cell case, thermal structure, and battery controller. 

Zyl AV, Dustmann CH (1995) Safety aspects of ZEBRA high energy batteries. evt95, Paris, 13-15 Nov 57... 

Trickett D, Current Status of Health and Safety Issues of Sodiiun/Metal Chlmide (ZEBRA) Batteries (1998) National renewable energy laboratory report, TP-460-25553... 

This same reaction of the liquid salt and liquid sodium is relevant for the high safety standard of ZEBRA batteries In case of mechanical damage of the ceramic separator due to a crash of the car the two liquids react in the same way, and the salt and aluminum passivates the NiCb cathode. The energy released is reduced by about 1/3 compared to the normal discharge reaction of sodium with nickel chloride. 

D Trickett. Current status of health and safety issues of sodium/metal chloride (ZEBRA) batteries. National Renewable Energy Eaboratory Report TP 460 25553, 1998. 

FIGURE 40.18 Two sodium-beta batteries foUowing safety/abuse testing that was performed while the batteries were charged and at operating temperature (a) an SPL HP sodium/sulfur battery dropped onto a steel pole, and (b) a Zebra battery after a steel beam was pushed through its mid-section (Photograph (b) is courtesy of MES-DEA SA). 

Relative to safety, ZEBRA batteries must satisfy the requirement noted earlier in the section on Battery Safety that the presence of the battery cannot contribute to the hazard of an accident. Some of the specific safety tests that must be passed include the follow-... 

Paradoxical effects of marked pedestrian crossings. Interestingly, the ubiquitous marking of crosswalks by two lines or zebra crossing - the most common pedestrian safety device - does not seem to be an effective accident countermeasure, and may even be counterproductive. This is despite the fact that drivers are more likely to yield to pedestrians in marked and conspicuous crosswalks than when they cross the street in unmarked or less conspicuous crossings (Katz et a ., 1975 Shinar, 2000 Van Houten, 1992). 

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