With their motorway tarmac-eating duty cycles, coaches might seem like the least possible vehicle type to electrify. Certainly full-electric coach options have been scarce in the market. That’s particularly compared to their back-to-base passenger transport cousins, buses, which also have a willing supporter in terms of funding (the UK government). By contrast, most coach operators are privately owned. But look more closely and a value proposition for electrification emerges.
“Coaches have a reasonable dwell time,” argues Ian Foley, MD of Norfolk-based bus electrification and electronics manufacturer Equipmake. “With reasonably fast charging, you can envisage a scenario where intermittent charging can do more and more as the charging network improves and faster charging is available in service stations, so doing longer routes will be more viable. Certainly in the short term, like a city bus, coaches cannot do every duty cycle that a diesel coach will do, but the question is about being smart about what applications are chosen. Once you have charging at 150-200kW, you can get a surprising amount of charging in 40-minute stopovers.”
In addition, Foley continues, compared to other types of commercial vehicle, they are very long lived. He says: “Coaches are really exciting; they are a neglected part of vehicle electrification. The life of a coach is longer than a city bus, and the capital cost is higher. The challenge today is that operators of a luxury coach, which might cost £500,000 and have an operational life of 30 years, know that they will not be running diesel in 30 years, so investment is difficult. But here we are repowering and upgrading a seven-year-old coach.”
As of writing in mid-July, it was in the last stages of pre-test construction of a repowered Van Hool T197 Altano tri-axle coach for operator Westway. The job was to strip out the MAN D2676 engine and ZF AS Tronic gearbox and replace it with a full-electric powertrain.
He estimates a daily range of 180-220mi with five batteries. That is based on Equipmake’s own simulations from bus duty cycles, plus data from a feasibility analysis that includes aerodynamics, mass and other factors. That should be ample for Westway’s planned routes around London. Foley adds that in this particular repower, up to two extra batteries could be added to increase range before the vehicle runs out of carrying capacity.
WHAT ABOUT RANGE?
Range is the critical question that everyone wants answered with an EV, Foley admits. He adds: “But it depends on the duty cycle and heating and cooling requirements. In general, city buses don’t have an air conditioning requirement, but heating in winter is an issue. Coach operators are more stringent about air conditioning cooling requirements in summer, and we had to factor that in. Some of our estimates need proving in our testing; some data we have had back already.”
All five 600kg batteries were fitted into the engine compartment and fuel tank space, as close as possible to the rear axle combination – and having a third axle helped with the coach’s carrying capacity, which remains 915kg. Operating at a nominal 750V, the batteries drive two HTM 3500 motors tandem-mounted on the propshaft running at 2,500rpm generating a combined 3,500Nm. (Originally having a ratio of 3.42:1, the rear axle diff was also changed to another Van Hool standard product, at 4.55:1.)
Foley says that maintaining the traditional power transmission architecture of propshaft and conventional rear axle with differential simplifies the engineering of the repower, compared with moving to an e-axle arrangement. The repowered coach’s top speed is expected to be the same as the original – 100kph.
In terms of power electronics, the bus will charge batteries via a CCS2 DC charger via a power distribution unit with contactors, fuses and isolation monitoring. The system feeds the propulsion motors via Semikron IGBT (insulated-gate bipolar transistor) inverters. An auxiliary power system powers an electrically driven air compressor and power steering pump brakes. The existing air conditioner is retained, but fitted with a new electric drive.
The pancake-shaped permanent magnet HTM motors are of the company’s own design, and while they may be quite conventional, he contends they are highly optimised for the city bus duty cycle, which leads to 50% savings in size and weight.
A bonus of the electrical drive system is the little that needs doing to keep it going, Foley reports. “The good thing about EVs is that servicing is light; it’s really the air compressor and a yearly check-over.” The system comes with a five-year warranty. During that time, Equipmake will provide an annual check, and an annual coolant change, though Foley suggests that latter job is only included through an abundance of caution. “Fundamentally, there are no maintenance requirements of the batteries, the motor and the inverter,” he says.
Although the EV powertrain’s design life seems long at 15 years, that is only half of a coach’s operational life. So some components might need to be replaced, and here again Equipmake can help, as it is the technology provider. It manufactures battery packs from the module level, and develops its own power electronics hardware and software, shortly to include the inverters.
Over the next year or so the company hopes to install, in future coach repower projects like this, its own inverter, using silicon carbide technology, once testing is completed. “It’s more power-dense than the Semikron; two IGBT inverters equal one SiC inverter of the same size. The peak efficiency of an IGBT inverter is 96%, but the silicon carbide one is 99%, so that translates to more range on the vehicle, and it is also smaller and lighter.” He claims it could increase vehicle range by 5%.
Power electronics is the 26-year-old company’s background, having supplied inverters to a supercar brand, and is also providing a motor to the first certified electric aircraft. Its bus repower projects include an order to repower 12 electric Optare Versa single-deck buses in First Group’s York fleet. The new range is expected to be 150 miles, thanks to a new battery and patented HVAC system. Also, Metroline is currently testing a repowered TfL new Routemaster in London. There are also bus projects in Buenos Aires, Argentina and to fire appliances in the USA.
Last year, Equipmake listed on the UK stock exchange to fund its expansion, and has since acquired a 50,000 sq ft facility to carry out a number of vehicle repowers simultaneously. “The initial vehicle engineering takes months [nine, in the case of the Van Hool]. But our target is, once that is done, that a repower should only take a couple of weeks,” the MD says. “One challenge with repowers is that while the retrofit is going on, the operator is not earning any revenue, so you need to be able to do the process quickly.”
To carry out the work, the company has grown quickly, increasing staff numbers by 20 to 100 since the flotation, and up from 35 four years ago, when it recognised the potential of the repower market.