In 2021, Sofia will operate 45 ultracapacitor electric buses. Chariot Motors became a worldwide supplier of this innovative solution.
Sofia’s air quality challenge
Sofia is one of Europe’s most polluted cities. It constantly breaches WHO and EU air safety criteria, increasing the risk of heart disease, lung cancer, respiratory disease, and stroke. The main reason for urban pollution is the old public transport fleet and passenger cars, as well Sofia’s location in a plain between mountains.
Fine particulate matter (PM), NOx, SO2, O3 and CO2 saturation exceeds permitted levels in central Sofia, especially in winter. According to European Environment Agency figures, the air in Bulgaria’s capital is “very unhealthy” and rates the highest pollution index.
The solution: e-buses
The Sofia city fathers plan to make most or all the urban bus fleet zero emission. E-buses were tested in the last six years. Some used traditional battery charging and others had fast charging ultracapacitors. Fast charging is practical in cities with relatively short bus routes and easy power access from tram, trolleybus, or subway networks.
A successful ultracapacitor e-bus pilot project
In a first for Sofia and the European Union, 2014 saw an ultracapacitor e-bus piloted by innovative company Chariot Motors.
Route 11 with its unduplicated 11.2km length was flat, had moderate traffic, and operated for some 14 hours a day. The route received two 150kW DC/DC fast chargers at its termini, using trolleybus power supply.
The vehicle was a 12m low floor e-bus with two doors and two 67kW Siemens electric motors. Its 20kWh ultracapacitor gave enough energy for reliable end to end travel, including reserves.
The 18-month pilot project was a success.
Why choose ultracapacitors for opportunity e-buses
Reputable German laboratory Belicon GmbH measured Chariot e-bus net energy consumption (traction only; no air conditioning and sundry consumers) at just 0.95kWh/km. This is among the lowest operational e-bus power consumptions.
Power economy is only one reason why ultracapacitors are attractive for e-buses. Batteries effectively and safely use between 20 and 90 percent of their storage capacity, while ultracapacitors can use 100 percent. This makes otherwise identical ultracapacitor e-buses cover longer distances on a single charge.
Ultracapacitor e-buses need no overnight charging. They retain the last fast charge until the first one in the morning, including any depot relocation runs.
Another benefit of ultracapacitor e-buses is that frequent charge/discharge cycles do not affect longevity. Chariot e-buses come with full ten-year ultracapacitor pack warranties.
Ultracapacitors are also more robust, environmentally friendly, and safer than batteries. They cannot ignite or explode in difficult operations and retain performance in temperatures between -40 and 60°C. They have no harmful or toxic components, presenting no pollution hazard and no hidden end-of-life disposal costs.
Sofia chooses ultracapacitor e-buses
In January 2020, the Stolichen Elektrotransport Sofia public transport operator put fifteen Higer-Aowei 12m ultracondenser e-buses into operation. Equipped with 40kWh ultracapacitors, the buses run on routes 11, 84, 184, and 123, with 11km average unduplicated length. By October they helped cut Sofia air pollution by 20,678kg CO2 and 60.2kg NOx.
In October 2020, the Stolichen Elektrotransport signed up for another 30 Chariot Motors ultracapacitor e-buses for delivery in 2021. Sofia’s 45 ultracapacitor e-buses will then form 7 percent of the city bus fleet.
Chariot e-buses: more cities, more solutions, no vendor lock-in
Chariot ultracapacitor e-buses operate worldwide. A fleet of 37 ultracapacitor Chariot e-buses plies Tel Aviv routes. Five serve Belgrade. Three operate in the Bulgarian city of Gabrovo. Chariot has proven its technology in pilot projects at Graz (Austria), La Spezia (Italy), and Aalborg (Denmark). Further pilot projects are coming shortly, including ones in Turin (Italy), Budapest (Hungary), and Sarajevo (Bosnia and Herzegovina).
As well as two pole charging as used in Sofia, the e-buses can also be delivered with four pole fast charge equipment to European standards (roof up and top down), compatible with the charging infrastructure for other electric buses using the same standards. Despite different energy storage physics, vendor lock-in is not an issue when choosing Chariot ultracapacitor e-buses.
For customers who, for whatever reason, prefer electric buses with overnight slow charging and no opportunity charging, Chariot Motors offer a full product range of slow charge battery electric buses of 8.5, 12, and 18m lengths with corresponding passenger capacities and 172, 345 and 516kWh batteries. Depending on operational conditions, single charge daily range, including auxiliaries, can easily exceed 200km. Ten such buses operate in Tel Aviv.
Ultracapacitors for opportunity electric buses and batteries for overnight electric buses: the proven Chariot Motors concept
The case study appears on the Czech Transport Company Association website page 4 (in Czech).