S. A. Ageev, Head of the Production Division Partnership of Energy and Electro-mobile Projects LLC (TEEMP)
In an age of the rapid spread of electric transport and growing demand for efficient energy-storage units, a technology with a proven track record stretching decades of R&D and practical application is getting a new lease on life. At issue here are supercapacitors (SC), which are capable of providing devices (including standalone units) with a high-power current. Work in this area is being carried out by TEEMP (part of Rotec JSC): the company has developed a structurally-new type of SC cell with the potential for use in railway transport. The creation of hybrid shunting diesel locomotives with the use of supercapacitors at Russian Railways JSC has been identified as one of the promising areas for the development of rolling stock .
SCs are capable of instantly delivering high-power current and boast a huge resource while not differing in terms of high energy density . Thanks to this combination of qualities, SC are an ideal basis for starter systems, energy recovery and start-stop systems on rolling stock, as well as for high-power uninterruptible power supplies (UPS) capable of compensating for voltage drops and short-term power outages at industrial and railway facilities.
The volume of the global supercapacitor market amounted to $487 mln in 2019, indicating the broad distribution and use of SC throughout the world (analytical report data) . Yet, this technology has never been strictly sought after in Russia. This can be explained by a whole host of factors, ranging from the traditional skepticism about resource conservation to the complicated bureaucratic procedures entailed in approving the integration of additional systems into the existing transport infrastructure.
The revitalization of demand for SC would be facilitated by the development of supercapacitor modules that have no analogues in terms of the specific energy per unit volume and unit mass, the uniformity of current-load distribution and the integrated system of thermal-field dissipation (cooling).
Fig. 1. SC cell in the TEEMP form factor
Fig. 2. Method of connecting SC cells in a module
TEEMP decided to implement this approach. In 2014, specialists from the company’s R&D center, together with MISiS, began developing a construct and electrolyte for a supercapacitor cell – a unit element from which modules with the required voltage and capacity characteristics are assembled at the customer’s request (Fig. 1, 2). In 2017, the product was put into full-scale production. Due to the original design, the base cells of the SC modules have a number of advantages: the minimum number of parts in the cell; the minimum internal resistance; switching over the entire lateral surface of the cell; retained operability after testing by short-circuit currents; optimization of current and thermal fields; reduced weight of the cell and the assembled module by 30% in comparison with the similar devices of competitors. The use of a multicomponent organic electrolyte expands the range operating temperatures of SC and start-up system up to −60 °C.
The higher characteristics in comparison with analogs (Table 1) allowed the company to develop the implementation of SC in railway transport in two directions:
Table 1. Comparison of the characteristics of 2.7 V supercapacitor cells from different manufacturers (data from the official websites of foreign supercapacitor manufacturers)
On shunting and mainline diesel locomotives in the cold season, coolant warm up (water, oil) is carried out when the diesel generator is idling, which leads to the ineffective consumption of fuel and energy resources. To nullify this effect, it is advisable to use automated warm-up systems with automatic on/off switching of the locomotive's propulsion system. Taking this into account, at the initiative of AVP Technology LLC, which is engaged in the automation of control systems for rolling stock, ASDL specifications for shunting and mainline diesel locomotives were developed and agreed, an integral element of which is the SC manufactured by TEEMP.
Table 2. Economic effect during the operation of the TEM18DM diesel locomotive after the installation of ASDL
When using ASDL, fuel consumption is reduced, the resource of propulsion equipment increases , and the negative impact on the environment is reduced. The economic effect was calculated when installing ASDL on the TEM18DM diesel locomotive (Table 2). When operating diesel locomotives, the lion’s share of all costs (up to 80%) is represented by diesel fuel. During the lengthy downtime of a locomotive, the unproductive consumption of diesel fuel at idle speed can reach 40% of total consumption (data from the RPDA-T onboard recording systems – author’s note), including 17% during idle parking for more than 15 minutes. For example, the average fuel consumption of an idling diesel locomotive is 7.5 kg/h . During such downtime, the ASDL makes it possible to automatically turn off the diesel locomotive with coolant (water) temperature control and automatically start the diesel engine using the energy-storage unit when the temperature drops below the allowable level. This ensures a reduction in consumption by up to 50% of the locomotive’s normal warmup. Savings are also achieved through the lower cost of motor fuel and reduced emission charges . In addition, when using energy-storage units, the load on the diesel locomotive’s battery during engine startup is significantly reduced, which makes it possible to increase battery life by a factor of 1.6-1.8.
Fig. 3. ASDL are also installed on the TEM18DM diesel locomotives of Russian Railways JSC
Within the scope of the investment project “Implementation of Resource-Saving Technologies in Railway Transport,” the Traction Directorate, a branch of Russian Railways JSC, carried out a feasibility study that served as the basis for the decision to use ASDL. At the moment, more than 1,000 ChME3 and TEM18 shunting diesel locomotives are equipped with these systems (Fig. 3). The rolling stock is equipped with ASDL based on the supercapacitors of MO-110V18F-0, MO-75V50F-01, MO-75V100F models. Just a single diesel locomotive can save up to RUB 300 thousand a year on diesel fuel, motor fuel and emission charges due to the automatic start-stop system of diesel engines based on TEEMP supercapacitors. As a result of the project feasibility study, the payback period of the system is: when parked for 15 minutes or more – 2.6 years; when parked for 30 minutes or more – 5.1 years.
TEEMP, together with AVP Technology LLC and Russian Railways JSC, is currently collecting statistics on ASDL efficiency with the results expected by the end of 2020. Failures to start diesel locomotives in subzero temperatures using the SC have not yet been recorded. A supercapacitor maintains its performance in delivering power, regardless of low temperatures (unlike a battery) – its internal resistance remains unchanged in cold weather.
Equipping an electric train with a standalone propulsion system using SC and an optional DGU makes it a hybrid capable of autonomously covering a distance of up to 320 km at a speed of 120 km/h.
Fig. 4. Equipping an electric train with a standalone propulsion system using SC and Li-ion and an optional DGU
The required power is distributed between the DGU and the energy-storage unit from batteries and supercapacitors. The system is capable of recovering braking energy and returning it back for powering the electric motors (Fig. 4). Table 3 presents the technical performance of the system; calculations were made on the Vladimir – Ivanovo railway section, where, due to the lack of an electrical network, the “Lastochka” electric train was connected to the TEP70BS diesel locomotive.
Table 3. Technical performance of a standalone propulsion system using SC and Li-ion and an optional DGU
The benefits of such a combined installation can be fully implemented on non-electrified railway sections and yield savings on diesel locomotive use and operating costs. According to our calculations, the estimated cost of such a system is RUB 115.2 mln (excluding the cost of the carriage itself).
The new type of SC cell opens up wide opportunities for the application of solutions in railway automation as well. TEEMP has developed an uninterruptible power-supply system that increases the reliability of power supply to facilities during drawdowns and short-term outages of the main power source. The supercapacitor UPS is capable of providing a maximum power supply of 20 kW for 6 minutes in the absence of a main power source. In 2018, TEEMP, together with a Ducati Energia Spa business unit dealing with electronics and automation systems for transport – including railway infrastructure, completed a supercapacitor-based UPS assembly for the Italian railway network (Fig. 5). At present, a trial run of the system is being carried out with the aim of subsequent certification for use at high-priority facilities.
Fig. 5. Uninterruptible power-supply assembly for Ducati
The use of supercapacitors in recuperation systems is in the process of development, and should help eliminate the wastage of excess braking energy in railway transport. It can operate in tandem with the existing propulsion system in two modes – energy saving and network voltage stabilization. It is planned to complete the development process in 2021-2022. So far, this energy-storage system is only being used in the Warsaw subway system.
List of references
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3. Global Supercapacitor Market Report (2020–2025). Mordor Intelligence Industry Reports. – [An Online Document] URL: www.mordorintelligence.com. (Date of reference: July 15, 2020).
4. O. S. Popel et al. Physical modeling of hybrid electric energy-storage operation when starting the engine at low ambient temperatures / O. S. Popel, A. B. Tarasenko, A. A. Fedotov, S. E. Frid // Intelligent electrical engineering. – No. 3. – 2018.
5. A. B. Tarasenko etc. Cold engine cranking by means of modern energy-storage devices – physical simulation / A. B. Tarasenko, T. S. Gabderakhmanova, S. V. Kiseleva, M. J. Suleymanov // MATEC Web of Conferences – Vol. 178. – 2018.
6. RF Governmental Resolution No. 344 dated June 12, 2003 (as revised on December 24, 2014) “On standard charges for atmospheric emissions from stationary and mobile sources, pollution discharges into surface and underground bodies of water, including through centralized drainage systems and the disposal of production and consumption waste.”