Feature: Transportation
For popular applications like low-
Figure 1: Comparing two popular transportation battery technologies with an ultracapacitor
temperature engine starts, ready-assembled ultracapacitor modules provide quick and easy implementation. An example is the MDLC0300C0, a 300F 24V module, with a robust IP65 battery-style profi le. T is unit can operate down to -40°C and deliver a maximum peak start-up of 45kW.
technology have led to the design of relatively compact capacitors with high capacitance values, known as supercapacitors and ultracapacitors. T ese off er exceptional energy-to-weight characteristics and are becoming an emerging option for transportation energy storage. With their high power density, rapid charging and high discharge current, ultracapacitors satisfy the demand for engine start-up, peak load capability and regenerative energy storage. Comparison of performance characteristics between lead-acid, lithium-ion batteries and ultracapacitors is shown in Figure 1.
Ultracapacitors in transportation systems T e capacitance of supercapacitors and ultracapacitors are typically in the tens and hundreds, even thousands, of Farads. T ey behave like an ordinary electrolytic capacitor, with quick charge and discharge cycles, but their low internal resistance and high energy storage capacity make them more like a rechargeable battery. Because of this, ultracapacitors are fast becoming a viable energy storage medium, replacing conventional batteries in some applications. Ultracapacitors from specialist supplier
Supreme Power Solutions (SPSCAP) use an activated carbon coating and organic electrolyte, which enables high capacity, low internal resistance, low leakage and high-reliability characteristics. T e high surface area of the porous, activated carbon electrode and charge separation by a thin electrolyte layer create a double-layer capacitor, to meet the demands of several transportation applications:
• Braking energy recovery systems for subway trains and light rail trams;
• Integration with batteries for high performance;
• Low-temperature start-up of diesel locomotives; and
• Load balancing for multiple-axle drive units during fast acceleration. Ultracapacitors can deliver the instant
peak load capability required to start a diesel engine, prolonging battery life and reducing maintenance and replacement costs. For this, SPSCAP, for instance, off ers its SCE and SCP series of low ESR, cylindrical, high-duty-cycle ultracapacitors. T e SCE series (Figure 2) off ers between between 100F and 800F, and options of weldable or threaded terminations at one end. T eir compact dimensions lend them to use in series or parallel, to form backup power for instant power delivery. SPSCAP’s SCP series off ers weldable
terminations at either end and a duty cycle over one million. T ese ultracapacitors suit energy recovery solutions, locomotive engine starts and hybrid drive trains. T e SCP2000C0, for example, is a 2000F, 2.7V, measuring 60.8 x 108.4 mm and weighing 402g. It can operate across a temperature range from -40°C to + 65°C, and its peak current exceeds 2000A; its maximum continuous current capability at ∆40°C (temperature rise 40°C) is 208A. Recent additions to the SPSCAP
lineup include the CDCL and CDCM ultracapacitors, comprising diff erent capacitance values, dimensions and working voltages. For example, the CDCL family consists of 650F, 1200F, 1500F and 3000F ultracapacitors.
High-density energy storage As mobility and transportation become more diverse, the need for long-life, rapid charging, high-energy-density storage has never been greater. Here, ultracapacitors have quickly become a viable energy storage method, for instant power delivery in traction control, energy recovery and engine start-ups. T ey easily complement existing battery installations for peak- and multiple-load balancing, or as the primary power source for a host of onboard systems.
Figure 2: The SPSCAP’s SCE series of ultracapacitors; four sizes shown here
Figure 3: The SCP series of ultracapacitors, also by SPSCAP
www.electronicsworld.co.uk June 2022 33
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