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ISE Signs Exclusive 5-Year Agreement With Optare to Supply Ultracapacitor-based Energy Storage Systems for Buses

ISE CleanTech, Inc., a wholly-owned subsidiary of ISE Limited, a developer, manufacturer and distributor of energy storage systems (ESS) and heavy-duty hybrid-electric drive systems, signed a 5-year exclusive supply agreement with Optare UK Ltd, effective 21 June, for its ultracapacitor-based Ultra-E energy storage systems. ISE secured an initial order for 66 Ultra-E ES Systems with 22 systems to be delivered in 2010.

ISE also recently entered into an agreement with Maxwell Technologies, Inc. under which ISE will source ultracapacitor cells for use in its ultracapacitor energy storage systems exclusively from Maxwell through December 2011. (Earlier post.)

Optare, a leading manufacturer of electric and hybrid-electric vehicles, designs, manufactures, and sells single deck and double deck buses and mini coaches and offers post-sales service via operations throughout Continental Europe, North America, and elsewhere. On 10 May, Optare won an award for up to 66 units, or 100% of the hybrid bus order, from Greater Manchester Integrated Transport Authority (GMITA).

As not all hybrid buses are the same, we needed to ensure our low emission vehicles were each powered efficiently and effectively. After an extensive evaluation process, we choose ISE as our exclusive supplier for ultracapacitor-based ES Systems because of its rugged, modular and scalable designs. ISE’s Ultra-E ES System is clearly the best solution for our hybrid vehicles. We are confident that our selection of ISE will enable us to fulfill what represents the single largest order for hybrid buses so far to be placed with help from the Green Bus Fund. Our partnership also enhances Optare’s leadership position in this highly-competitive hybrid vehicle market.

—Glenn Saint, Optare’s commercial director

According to Frost & Sullivan as of December 2009, the estimated global hybrid and electric heavy commercial vehicle demand, which represents part of the addressable market for energy storage systems, is expected to reach approximately 240,000 units produced by 2015.

The basic ISE ultracapacitor module is a liquid-cooled, 100 VDC, 0.1 kWh unit built with 48 ultracapacitor cells (Maxwell Boostcap 3000P). Capacitance is 62 F, total energy stored nominal is 105 Wh (peak 125 Wh). Rated power is 40 kW, and DC ESR is 16 mOhms. The units have a cycle life of 1 million (50% DoD).

ISE’s liquid-cooled Ultra-E ES System includes a battery management system that actively monitors each cell.

ISE specializes in series hybrid-electric and all-electric/zero emission technologies, and offers industry-leading ES Systems and Hybrid System components. Over the past 10 years, ISE has sold more than 300 hybrid systems with more than 13 million miles combined of fleet operation.



Is the very low energy stored in the supercaps enough to move a bus more than a few dozen meters? Are high energy batteries + genset used for the rest of the way?


If we take a 10 Tonne bus, and extract 125 Wh of energy from it, this is 125 x 3600 W Seconds (or joules).
This is 450000 Joules, and is the equivalent to the 10 tonne bus doing 9.5 m/sec or about 21 mph.
Thus you can store the energy of a bus doing 21 mph in one module.
Then you have to factor the efficiency of the regenerative braking, which will be much less than 100% (say 50%), and you end up with the ability to absorb the energy of a bus doing about 29 mph (21x1.41) which sounds about right.
[ I also have a feeling that regenerative braking is more like 25% efficient, but I would be happy to be corrected. ]


Regenerative is a function of capacity and not production. The motors become alternators and can create electrical energy at speed. Obviously as you slow down, less energy is captured and the mechanical brakes come in at some point, but the brakes last much longer.

HEVs with only 1 kWh of batteries capture very little braking energy. If you increased the batteries to 4 kWh, you can capture more. Super caps are great at capturing this braking energy, but add additional cost.

If the captured energy can help the vehicle start from a stop without using as much battery or engine power, then the mileage should increase. More batteries can do the same thing, but it depends on their state of charge.


The efficiency of the regenerative braking is about 31.3% for a electrical system that uses batteries and 42.7% for a hydraulic system;

You have to remember that every time you convert energy from one form to another you lose some to entropy. In a braking HEV energy goes from kinetic(foreward motion) -> electric(generator) -> chemical(battery) and then from chemical -> electric -> kinetic when you re-accelerate. A HEV that uses capacitors will therefore be more efficient because you're bypassing the electrical -> chemical -> electrical convertion steps: Capacitors store the actual electrons that the generator produced.

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