Electrification

In Progress

Hydrogen

According to a 2016 factsheet report from the Canadian Hydrogen and Fuel Cell Association, carbon footprint of hydrogen vehicles may be considerable lower than that of BEVs: 2.7g/km for FCEV versus 20.9g/km for BEV on average . According to the International Council on Clean Transportation (2017), increased energy efficiency, quick refueling time, increase renewable energy use, and reduced greenhouse gas emissions feature among the main benefits of hydrogen fuel cell vehicles. A recent study by Ueckerdt et al. (2021) found that the mitigation costs of hydrogen range between 800-1200 €/tCO2. Yet, they suggest that large-scale deployment of the technology could bring down costs to 20-270 €/tCO2 by 2050 certain highly unlikely conditions are met. It means that hydrogen is still a debated alternative given its cost-competitiveness compared to electric vehicles (van Vliet et al., 2011). 

Hydrogen could be particularly useful in hard-to-electrify subsectors such as long-distance transport, according to Van Renssen, as in the case of buses and heavy-duty freight. The future of hydrogen fuel cell buses depends on the charging possibilities. It could be a good solution to build common charger points to buses and HFCEV long distance freight heavy goods vehicles (HGVs).

However questions remain about the feasibility of implementation, and the hydrogen combustion engine does present several issues which limit its applicability. Critically, hydrogen engines generate incredibly high heat within the combustion chamber, which creates NO2. Additionally hydrogen combustion engines have a low energy density by volume. This means it has almost half the efficiency that other alternatives have and matching other fuel mixtures would require a much larger tank. The use of hydrogen as fuel in a combustion engine may be ideal in rocket science, however on-the-ground solutions would require an alternative to the combustion engine.

Current initiatives include the Joint Initiative for hydrogen Vehicles across Europe programme (JIVE and JIVE2) is funded by the EU and is introducing new fleets of FCBs and associated hydrogen refuelling infrastructure in cities and regions across Europe in partnership with the International Association of Public Transport. Their recent knowledge brief provides an analysis of best practices drawing on a fictional case study from the JIVE best practice report of 2020. In addition, the H2Bus Europe initiative, centered in the UK, Denmark, and Latvia aims to introduce low zero emissions hydrogen busses to participating cities, hoping to achieve the scale required to achieve ideal savings. 

Other Examples:

France launched the world’s first hydrogen-powered bus rapid transit system in Pau in 2019.

Poland: city of Konin in Greater Poland will be the first in Poland to introduce hydrogen cell-powered buses into its fleet. The buses are designed and produced in Poland by a Poznań-based company Solaris, which exports its public transportation vehicles throughout Europe. They will be in use in 2022 and leased for the next 4 years. The Solaris buses are equipped in a micro-power plant producing electricity from hydrogen, where the only byproducts are steam and heat. lt’s feature is an additional electric energy storage battery.

Heilbronn, Germany also opted for the Solaris hydrogen buses, as the region is planning to use generate low-emission hydrogen from wind energy and use it to power its fleet with a zero-emission fuel. The overall environmental balance of the whole value chain is therefore close to zero.

Germany, Austria, Sweden and the Netherlands have also already ordered Solaris’s Urbino hydrogen buses.

Overhead Charging

In order to meet demand and use requirements of a well functioning bus network when using electric busses, special considerations must be made for charging and range. Busses must be able to charge with relatively little downtime in order to maximise fleet efficiency, something which requires significant power and transmission capabilities. Plug-in chargers are currently limited by wire gauge and weight, however other charging strategies such as opportunity charging and in-motion charging may provide enough energy to maintain a bus fleet with at a high service level.

Opportunity charging is a charging strategy where a vehicle is not only charged overnight at the depot, but at strategically placed charging locations throughout the network as it makes stops during the day. Advancements are being made in this field as more efficient and powerful pantograph chargers are being built, which allow drivers to wirelessly dock at a passenger stop and charge for a short period of time. By adapting busses for overhead pantographic charging, transport authorities can ensure that service is uninterrupted and range requirements are met.

In motion charging (also called dynamic charging) is a process through which busses charge while in motion. This is typically facilitated through overhead systems, and in the case of busses was adapted from charging systems typically used to deliver electricity to trains and trams. As opposed to opportunity charging this requires no extra time during the day, however flexibility is restricted as busses must follow the set lines where possible. Studies have shown that 20-40% network coverage is capable of providing enough charge while ensuring functionality and flexibility. 

Examples:

Madrid has implemented a series of changes to its bus service, including increasing the number of electric busses and charging stations along bus lines. Beginning in 2016 line no. 76 was equipped with wireless charging stations at each terminus, to test the feasibility of wireless charging with shorter stops. Following this success and later expansion the city transit authority opened the first fully electric bus line to passengers in 2020 and expanded from there, with a complete diesel phase out expected in 2022 following the expected acquisition of over 500 electric busses supported by dynamic and opportunity charging across the city. 

Berlin has the largest e-bus fleet in Germany with 137 busses currently in service and a tender for delivery of 90 more in 2022. Berlin is in the midst of increasing non-depot charging options for its fleet, and is placing inverted pantograph charging systems at different stops and terminuses around the city. BVG is partnering with the Technical University of Berlin to continue research  into energy efficiency and wireless charging potential throughout the city.