We talk about electric cars. What about electric buses for Hereford? September 2019
Updated: Aug 31, 2021
Progress in electric bus technology is rapid and operators now have more than one method of charging their vehicles. Overnight charging is what you might call the ‘traditional technique’; you plug in, leave it for several hours, hit the road with a full battery and repeat each day. The alternative is opportunity charging – a rapid and intense blast of power at strategic points along the route, which can allow for a longer range.
Bus manufacturer Optare produce an electric version of its best-selling ’Solo’ vehicles. The local Hereford operator Yeomans has a sizeable fleet of the diesel version, many of which are showing their age. Optare’s biggest seller the ’Solo’ is already produced with an electric version. The vehicle shown is of one of a fleet destined for the island or Orkney. If an island off the coast of Scotland can go electric with its bus services then surely Hereford can!
Daan Nap, Global Sales Director for electric bus charging, at electricity infrastructure firm ABB, explains the difference between the two. “On average [a bus] might drive 100 or 200 miles a day, so you take a very big battery, charge the bus overnight, drive around all day, and at night, you charge it again; that’s overnight charging. It generally means quite big batteries, for example, 200 or 300kWh, and the charge happens at probably 50kW or 80kW over four, five or six hours.
“However, some people say ‘it’s a big battery, it’s a lot of weight and it takes up a lot of space, so I can’t carry as many passengers.’ Also, the range becomes a limiting factor, so if you want to drive 300 or 400 miles in a day, the other option is opportunity charging.
This means you take the same vehicle but use a smaller battery [and] there’s a charging system at the end point of each route. That’s at the point where, normally, the bus is empty, the passengers have got out and there’s a break of five or 10 minutes. We charge the bus at a higher power – a level of around 300 or 450kW – which charges the bus in three to six minutes. Then it can run the route again maybe one, two, three or four times. By doing this, you reduce the size of the battery, you reduce the weight, you reduce the cost and you can carry more passengers.”
According to Nap, opportunity charged buses typically lend themselves to longer routes that are out of reach of overnight charge vehicles, while
Adrian Felton, City Mobility Manager at Volvo Buses – which manufacturers an electric hybrid opportunity charge bus – says they make sense on routes that involve a mixture of inner and outer city driving.
“Say you had a route that was 20-30 kilometres long and ran from Dudley into the centre of Birmingham; it would be ideally suited to that. Ultimately, you would have an efficient hybrid vehicle running for 20 kilometres, and you could then zone-manage it so that the two kilometres in Dudley town centre were carried out as a full electric vehicle and the other five kilometres could be used in Birmingham city centre, to give the air quality benefits in those areas.”
“We can zone-manage, or geo-fence, that vehicle to set up and agree specific areas with the operators, the local authorities or the passenger transport executives and it’s fully automatic; I guess this really is one of the first stages of moving towards that low level of autonomy. [The changes are activated via] GPS, and there are three different types of zones: we can set the vehicle to operate on zero emissions, we can also set it to operate in silent mode – reducing some of the ancillaries makes it quieter in certain areas, and with the PHEV we can actually switch off the engine if it’s a silent zone as well as a zero emissions zone – and finally, we can set safety zones to reduce the vehicle’s speed in a specific area.”
Opportunity charging also suits short-cycle, repetitive routes, as Matt Horton, Chief Commercial Officer at US-based electric bus specialist Proterra, explains, “what we have found is that the best use cases for en-route [opportunity] charging tend to be situations like airports, where the buses will follow the same route for hours on end, and generally very short routes. So sometimes, dense urban areas, downtown or airport-style circulator routes tend to be the best shape for en-route charging.”
Felton says it’s also possible to cut down on the amount of charging infrastructure if the route involves a longer period of downtime. “If we take something like a park and ride, they have a much longer layover – between five and seven minutes – so you might only want one piece of charging infrastructure for a longer route. If you’re going to get seven minutes’ layover time, you can actually travel into the city centre and back without putting any extra infrastructure in place. But if you’re looking at growing your network, you may want to place strategic infrastructure at bus interchanges anyway.
However, as technology marches on, opportunity charging could end up battling it out with overnight charging as the dominant method. “En-route charging systems are going to need to continue to drop in price to remain competitive with [overnight] charging,” explains Horton. “One of the reasons is that chargers [for overnight charge buses] are dropping in price quickly because of all of the passenger electric vehicles out there.
“If you look at the price of the batteries, it’s dropped by 75% in the last five years, so we’re in the midst of a transformation as the industry matures, and the key driver to watch is the battery technology; that will determine how big a future, I think, en-route charging has.”
(Extract courtesy of Electricity Infrastructure Company ABB)
As an example of the hardware, Volvo’s opportunity charging system uses an overhead mast to power up the bus from the top down. “The vehicle pulls over under the mast, and you have a marker on the roadside; there is quite a lot of leeway in the rails and the charging mast, so it doesn’t have to be within millimetres,” says Felton. “The vehicle then locates the mast, positions itself looking for the marker in the road, and the driver applies the handbrake. You then get a message on the dashboard that says ‘ready to charge’ and the charger comes down. It tops up the battery and once that’s complete it says ‘fully You release the parking brake, the charger disconnects automatically and, until it’s fully retracted, the vehicle can’t move away.”
Other systems use an in road wireless charging system, this one developed by Electrec Ltd. “For electric transit, wireless charging is the most effective method for on-route opportunity charging. Within five minutes, the wireless charging system automatically adds enough energy to the vehicle’s battery to complete another route during its routine transfer station stop. This allows the electric bus to drive unlimited route cycles. Buses with Momentum’s wireless charging system stop over the charging transmitter embedded in the road to charge automatically”.
Many cities and towns in Britain are moving towards electric buses, often as a partnership between the local authority and operators. The mechanisms are there for such a move…. government grants under the greener buses scheme and advice on setting up partnership schemes. Is it not time for Herefordshire to wake up to such developments for a cleaner future?