A battery bus – definitely not “one-size-fits-all”
4 August 2016 • Author(s): Jakub Slavik, consultant
Battery electric buses are becoming popular in many European cities. They combine zero-emission operation of a trolley-bus with (at least partial) operational independence. A battery bus design, price and markets enable using standard public procurement procedures for their purchasing and operation, with possible contribution from the European Structural and Investment Funds (ESIF) – i.e. not just demonstration projects such as ZeEUS or current fuel cell bus projects. Despite this situation, a battery bus is definitely not a “one-size-fits-all” product.
Getting the right battery bus and charging technology
There is a big variety of vehicle configurations and charging concepts available. Getting the right vehicle and charging technology to the right place requires changing the product approach for the project approach with a sequence of steps in the project preparation stage that cannot be avoided. Let’s have a look at them closer, considering especially standard 12m buses as the most common bus type for urban service.
Which e-bus concept?
The key issue is: Where and how should the bus be operated and what is the expected daily mileage?
This will answer the principal question about the battery bus concept – an “overnight e-bus” charged just once a day with the battery capacity sufficient for the whole day shift or an “opportunity e-bus” with batteries recharged fast on the route.
The overnight e-bus concept using a standardised socket for its charging is a simple and robust solution wherever the required daily mileage does not exceed, say, 160 – 180 km. The e-bus usually offers as much space as a comparable diesel bus and its power consumption is still reasonable.
As soon as we get above the 180km required range, the choice becomes less clear.
There are obviously manufacturers offering even 250km range per single charging. However, a bus is primarily a device for carrying passengers. When filling it with batteries, the remaining space for passengers becomes limited and the power consumption per passenger place increases rapidly.
The opportunity charging concept then comes in question. As the carried battery capacity can be lower than by the overnight e-bus, the vehicle may offer more space for passengers. Furthermore, the unit power consumption is lower.
This concept, however, more or less pre-defines the e-bus operation area or routes and the buses lose their full operational independence. Sometimes a certain level of passenger discomfort and higher power consumption may be an acceptable “price” for retaining that independence or not resolving the opportunity charging issues.
There are additional opportunity charging concepts available. So, what’s the choice?
Inductive (contactless) charging such as that in Berlin offers almost no aesthetical impacts. It may, however, be a good source of various troubles as soon as the road surface above or around the charging plate needs to get repaired.
A non-grounded contact system using a bi-pole pantograph on the bus roof is employed in Vienna, for example. The trolley-bus or tram catenary is the power source by such systems and they are therefore likely to be the clear favourites if trolley-bus engineers become responsible for a battery bus project. The charging power, however, is quite limited by these systems. Also, the UN ECE 100 regulation requirements imply that placing a galvanic separation (simply: contactless power transfer) as a part of either the vehicle or the charging infrastructure is necessary here. The result is that such a “simple and cheap” solution may not be simple and cheap at all.
Grounded contact systems (often referred to as four-pole charging) use various mechanical consoles placed on vehicles or on the charging infrastructure, such as that in Hamburg. The charging process is automated, using M2M (machine-to-machine) communication between the vehicle and the charging device. The power source may be a DC substation as a part of the urban transit infrastructure (as in Dresden, for example) or a public AC network.
This is the only stream in the opportunity e-bus charging systems that (together with the overnight charging) is subject to the deliberate standardisation within the supplier industry and this process makes fast steps forward. Although there is a wide offer of many other technologies and concepts, it is worth pursuing and implementing those within the standardisation process. The story of the liked and hated Microsoft software may repeat: Surely there are more perfect systems, but this is the standard.
Not to forget: The old good socket may come in question for opportunity charging, too. If the timetable allows for, say, more than thirty minute break, why make things unnecessarily complicated and expensive? Well, if the drivers’ working conditions allow for that.
How about the suppliers?
So, now we precisely know what we want and it is time to go to the market and ask for it.
Issues related to professional culture may come in question by that. How often can I hear from transport operators’ engineers: “We were talking to the World-Class-Name Company people and we were told that they would make it for us just as we like”.
My dear engineering friends, nothing is impossible for the World-Class-Name Company’s engineers, indeed. Their sales people, however, will probably speak a slightly different language. They will be interested in the project size, the common or unique product requirements or the likely competitors and so on. They may asses your excellent idea as inadequate to the sunk cost or the business risk and decide not to take your promising chance.
It is therefore necessary to make the preliminary supplier market research, to stay in the real business world (and also, because the ESIF co-funding requires that).
Turnkey or separately?
If automated opportunity charging is chosen, the next question is: Tendering the vehicles and the charging infrastructure separately or together as a turnkey project?
The risk of the system unreliability, the likely project cost effectiveness, the tender administration demand and the risk of legal obstructions by the unsuccessful bidders should, at least, be carefully assessed by both alternatives, considering the project size and the level of experience by the operator.
System integration is always an issue wherever machines should talk to each other and co-operate. The worst possible position of a transport operator is becoming an arbiter between suppliers whose products refuse to work with each other.
So, simply speaking: a turnkey supply may be better for small projects, especially with the lack of relevant experience while separate tendering is the trend used by larger projects with proven technologies and experienced operators.
Getting as far as that, the project technological and operational definition should be summarised and the related project cash flows must be estimated and tested in a robust cost-benefit analysis, to make sure that the project is financially and socio-economically sound and worth public co-funding. Necessary additional costs such as new buildings etc. should not be forgotten by that.
If everything goes well, bingo! It is time to start with the tendering procedure. When asking for ESIF co-funding, the co-funding application comes in question beforehand.
Jakub Slavik is an independent business consultant in transportation and public service management.