Moscow's SuperCap Bus
By EV World
Moscow is famous for many things: Red Square, the Kremlin, the Bolshoi, the Metro, Gorky Park and . . . its long, cold winters. So when ESMA and its partners approached Moscow City Government with a proposal to develop an electric shuttle bus for use in the city's many parks, they had no intention of operating it using conventional electrochemical secondary batteries. Instead, their bus would be powered solely by 950 kg (2,094 lbs.) of energy stored in 8.6kW of super or ultra capacitors, possibly the first application ever of capacitors to power a vehicle this size.
The bus, pictured above, was developed by jointly by ESMA, a Moscow-based super capacitor manufacturer, and several other Russian companies, weighs 9,500 kg (20,994 lbs.) and has a top speed of 20km/hr, not overly fast, but quite suitable for use in its public park environment.
Not only are supercapacitors less subject to the detrimental effect of extreme cold weather than conventional storage batteries, but they offer very fast recharge times and significantly longer cycle lives. The 300 supercapacitors, grouped in modules of 25 each, can be recharged in a mere 12-15 minutes time and have an estimated cycle life of more than 10,000 cycles or the equivalent of some 100,000 kilometers. ESMA states that its supercapacitors can operate from -50 to +50 degrees centigrade, clearly superior to just about any battery in existence other than "heat" batteries like the ZEBRA battery from Switzerland.
The supercapacitor power bank is used to power both the DC motor and a DC-to-DC converter for running the buses low voltage equipment at 24-volts. A pulse current controller regulates the amount of energy used by the 40kW (maximum power) direct current engine (DCE). Nominal power output is 20kW at 2700 rpm.
During preliminary tests in one of Moscow's city parks, the bus traveled 9.5 km before being recharged. While this is substantially less than what a comparable bank of lead-acid batteries might provide, bus developers found it an acceptable compromise since the bus makes frequent stops and can be quickly recharged. Where a comparable lead-acid bus might travel 30 miles before needing a recharge, it could take 4-6 hours to recharge. By comparison, a supercapacitor bus could travel the same 30 miles with just 30 minutes of recharge time, effectively offering 4 to 6 times the range of the lead-acid powered bus. Recharge is accomplished at 220-volts at 360 A.
As the authors of the paper put it, "It should be noted beforehand, that [from] the authors' standpoint, these capacitors with energy density delivered of 8-10 Wh/kg and charge time of 12-15 minutes, provides [an] acceptable compromise solution for certain specific applications."
Since the bus was designed to operate on a course that was 6.5 km in length, supercapacitors proved the ideal solution for this application. The bus can be recharged while
The developers also built a city delivery van based on a GAZ-33021 ("Gazel") chassis with a max gross weight of 4,000 kg (8,818 lbs.) and a cargo capacity of 1,000 kg (2,204 lbs.). This vehicle, also supercapacitor-powered has a top speed of 70 km/hr and an average range of 33km at 30-35km/hr before needing to be recharged. Again recharge is a relatively rapid 1-2-15 minutes. The truck uses regenerative braking to help recharge the supercapacitor bank. During tests it recaptured as much as 40% of the energy expended.
More information on ESMA can be found on their web site at http://www.esma-cap.com.
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