Committed to Gas

Nottingham City Transport Engineering Director Gary Mason talks to Andy Izatt about how a fleet of gas-fuelled double-deckers will help the operator achieve Euro VI across its entire operation by the end of this year

By the end of 2019 Nottingham City Transport’s (NCT) fleet of 316 buses will be either Euro V or Euro VI-compliant as the operator responds to its major shareholder, Nottingham City Council’s clean air strategy. A key constituent will be 120 Alexander Dennis (ADL)-bodied gas-fuelled Scania double-deckers, the introduction of which having been championed by NCT Engineering Director Gary Mason over a number of years.
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“The Nottingham gas bus story really goes back to 2012 when Scania GB invited us to head office in Sweden to put across the operator’s perspective on the benefits of developing a gas (bio-methane) double-deck chassis,” explained Gary. “With the exception of three ethanol-fuelled Scanias, our fleet at that time was diesel. We knew our double-decks would need to be substantially replaced through to 2020-21. We were buying vehicles that complied with Euro V at that time, but recognised Euro VI was coming and were keen to explore all options.

“We were not lured down the hybrid route because of concerns over battery life and cost as well as component costs within the electric drivetrain. With our big emphasis on training drivers to read the road ahead and drive economically, we weren’t sure enough waste energy would be left in the bus to go back into the energy recovery system. Our Managing Director Mark Fowles also had concerns about the green credentials of battery manufacture, not least the mining and refining of all the rare metals that go into them.

“As Euro VI approached, we looked at electric vehicles. However, electric double-decks were still at prototype stage and even now, we would struggle to get the 250-mile range we require. While we have some running boards that are only 100 miles, each route has one or two that are in excess of 200 miles. Every vehicle we operate has to be able to perform any duty so, with at least a 10% safety margin, 250 miles is our key target.

“As Scania progressed with the development of a gas double-deck chassis with its bodybuilding partner ADL, we gave our support. The development costs were substantial and we knew there would be a cost premium to buying any vehicles. We also didn’t have any fuelling infrastructure.

“Like a knight in shining armour came the OLEV (Office for Low Emission Vehicles) funding stream in 2015. Focused on delivering low carbon solutions, it provided money for the differential cost of buying vehicles and for the supporting infrastructure. It would make buying gas double-decks viable, so we bid for funding to cover the extra cost of an initial 53 buses and building a fuel station.

“Our application was submitted in September 2015 with the results expected the following January, but there was a delay of six months over European state aid approval. We secured planning permission for the infrastructure, and a lot of design work in conjunction with our partner Roadgas, which was supplying a turnkey solution, was completed, but we couldn’t actually commit to hardware until there was confirmation the money would be in place. Three compressors were planned for the fuel station along with crates capable of storing six tonnes of compressed gas.

“There is a large 24-inch low pressure gas main that could supply the volume we needed the other side of the National Ice Centre in Lower Parliament Street where NCT’s head office and main depot is located. We needed the compressors to increase the gas pressure from 25milibar to 300bar and the energy required to do that meant we needed a new electricity supply that had to come from the other side of the BioCity office block some 300m away.

“What we did was make sure all the feeds had the capacity, not just for 53 buses, but the whole double-deck fleet based at Lower Parliament Street. That’s in excess of 200 vehicles. The site ground work was also put in place to accommodate that potential expansion.”

Going ahead

“We were finally told mid-2016 that our bid had been successful enabling us to go ahead with ordering vehicles and building the infrastructure,” said Gary. “The prototype gas double-decker and first few built for Reading Buses had utilised the same storage cylinders that had been developed for the single-deck. There were four over the engine and three smaller ones under the stairs. Gas filled at 200bar and the range of the vehicles was only around 170 miles.

“What was developed for us, and what became the standard specification going forward, was having two much larger storage cylinders capable of holding 1,000 litres of gas at 250bar on top of the engine at the back of the upper passenger saloon. That gave us the 250-mile range we required, but necessitated a complete reengineering of the gas storage and a number of key components like the pressure reduction valves, had to be recertified.

“The first chassis were built as kits by Scania in Södertälje, Sweden in early 2017 with assembly taking place at MI Vehicle Integration in Leyland. ADL bodied the buses at Falkirk. Rather than Enviro400 MMC (Major Model Change) body styling, we opted for the City, which has also been adopted as standard for the double-deck gas bus product.

“Weight was a consideration throughout the build, but the initial bus passed its tilt test first time. Seating is for 72 with 30 downstairs, plus 12 standees. There are just four seats across the back upstairs. A benefit was extra room in the lower saloon that meant we could increase the length of the buggy bay. That was important because Nottingham has historically operated 12m Scania ’deckers where we’ve been able to accommodate a wheelchair and several buggies without any conflict.

“Practical, durable, easy to maintain Lazzerini Pratico seats were specified with double padding with the ones downstairs having high backs. Going for low backs upstairs makes the saloon feel more open and improves the effectiveness of the CCTV. Every window that can accommodate one has a hopper opening so plenty of ventilation is available.

“The launch had been planned some time in advance in Nottingham’s Old Market Square for 19 May – what turned out to be a very soggy Friday – by which time the first vehicle had been certified. The first of what was an initial batch of 30 entered service on our West Bridgford route on 4 July with the remainder all on the road by the end of 2017.

“Because of the time taken to recertify some of the components, those first buses weren’t initially able to operate at full range. We had to bring some of our longest running boards back in for refuelling during the day. Also, we were cautious because we weren’t familiar with the buses and didn’t know how reliable they were going to be. Because of that, we opted to have more in unbranded livery than we might otherwise have done. It underlines our confidence now that by the end of this year when all 120 we’ve ordered are delivered, the bulk of our spare fleet will be diesel. Unless they’re in for service or maintenance, the branded gas buses will be out there all the time.

“For all intents and purposes this was an all-new bus design, but I think we only had to make around a dozen minor changes to the second batch of 23 which entered service by the end of March 2018. We waited so they could have 18-plate registrations.”

Wider agenda

“About the time we made our OLEV funding bid, it became clear that Nottingham was one of five cities outside London that needed to have a clean air plan. The expectation was that the bus fleet was going to have to meet Euro VI standard by 2020 when a CAZ (Clean Air Zone) was proposed. In 2016 we had around 325 buses and not one of them met that, so there was limited time to do something. With our gas bus project, we had accounted for 53 of those vehicles, but there was still a long way to go. In conjunction with the city council, we needed to look at what we could do.

“It’s our normal company policy to aim for an average age of six years for the fleet which means that we look to replace vehicles once they get past their 12th birthday. We do that to keep under control total cost of ownership.

“By 2020, the Euro III fleet would have been due for replacement anyway so there was no point investing lots of money in it. Our Euro IV double-deckers – not quite so many vehicles – would have been within a year or two of being due for replacement so we took the view, there’s no point doing anything to upgrade those either. We would replace them all in 2019 with more gas double-deckers, which had proved themselves, and we’d future-proofed the infrastructure so fuelling capacity could be increased to accommodate that.

“That still left 180 Euro V vehicles we couldn’t afford to replace so, working with both the city and county council, we secured money through the Clean Bus Technology Fund to upgrade those with Euro VI-compliant emission abatement systems. There’s also actually another six buses that are training vehicles. We chose Baumot to convert all of them because at the time we placed our order, it was the only company that had an accredited system for our entire fleet.

“In many respects the exhaust retrofit project is more challenging than introducing gas buses because third party equipment is being bolted onto an OE (Original Equipment) chassis. All our Euro V double-decks are Scanias. The single-deckers are ADL E200s and Optare Solo SRs. It’s not too much of a mixture, but the Scanias don’t use AdBlue because it’s an EGR (Exhaust Gas Recirculation) engine. To meet Euro VI necessitates installing an SCR (Selective Catalytic Reduction) system and using AdBlue, so it’s a real challenge.

“Baumot is carrying out the work at our Trent Bridge depot starting with single-decks working towards upgrading three a week. It will start on the Scanias in a few weeks’ time and then there will be two teams converting at least four buses a week.

“There’s another 10 older midibuses we need to replace – eight Scania East Lancs OmniTowns and two ‘classic’ Solos – that we’ll replace with Euro VI buses. That will give us a Euro VI or Euro VI-compliant fleet by the end of the year.

“When the OLEV (Office of Low Emission Vehicles) funding scheme was announced last year, we were disappointed that the focus was on delivering zero emissions rather than low carbon solutions.

“Our view has been that Euro VI, whether it be diesel or gas, is intrinsically clean. Our gas buses are as close to being carbon neutral as the current technology allows and that has been the way we have wanted to move forward. However, while they’re more economical to run than diesel equivalents, they still cost more to buy. The payback is in the order of eight years. Despite all of that, we went ahead and ordered an additional 67 gas double-deckers.

“While there was no money available to help pay for those vehicles through OLEV, fortunately it was possible to secure a contribution towards increasing the infrastructure and we were very grateful to hear the announcement at the beginning of February that we’d been allocated £1.12m. Roadgas had been busy on the planning, but this means we could start the physical work – important because there are long lead times on some of the equipment to be installed.

“A diesel bus takes a minute and a half to two minutes to refuel, while a gas bus takes three to four minutes. At the moment, when there’s a run of gas buses coming in after the evening peak, we fuel around half of them and put the remainder in a holding bay to be fuelled later when it’s quieter.

“Currently our capacity to put gas into buses is much greater than the capacity of the compressors to compress the gas that comes out of the main, but even now we’re learning how to improve the efficiency of that. Data we’ve had to collate for TRL (Transport Research Laboratory) as a condition of the OLEV funding has highlighted how the pressure drops towards the end of refuelling and we’ve been able to make adjustments to make the flow more constant.

“When Roadgas has finished expanding our fuelling capacity, the output will double. We’ll go from three to six compressors and the number of dispensers on the fuel island will increase from three to five – the same as for diesel. There’s already another dispenser by the gas station for third party use. The amount of gas stored will be trebled to 18 tonnes to give us more of a buffer.”

Fuel with a difference

“Training for our engineers working on the vehicles has been relatively straightforward because the engine is spark ignition like one that uses petrol. All the major mechanical components are the same as a diesel bus so the technology is fairly straightforward. What’s different is there isn’t a complicated exhaust treatment system like there is on a diesel. A gas bus has a three-way catalytic converter so is much simpler.

“There have inevitably been some teething problems, but for both us and our Scania dealer, Keltruck, we’ve been learning as we go along. As I’ve said, the buses have proved very reliable and 18 months down the line there isn’t much that catches us out now. Our guys have no concerns about working on them.

“However, gas does present different challenges. Lower Parliament Street is a very old garage, but is equipped with remotely operated opening rooflights. We have a detection system in the critical maintenance and fuelling areas that sounds an alarm and automatically opens those vents if any leakage of gas is detected. As methane is lighter than air, it just goes up.

“The detection system also shuts off and isolates the compressors stopping the feed to the gas dispensers and shuts down the gas heating system. There are procedures in place and our engineers have handheld gas detectors, but to date, we’ve not had a single alarm go off.

“We’ve also finalised emergency response procedures for Nottinghamshire Fire & Rescue Service and are now working with it to develop an e-learning programme that can be cascaded out to its staff. As we get more routes converted to gas, we’re covered by more fire stations. Each typically has four watches so there are a lot of people to educate.

“The infrastructure we’ve installed at Lower Parliament Street is not something we could easily replicate at Trent Bridge where the midibus fleet is based. It is in a predominantly residential area with a residential size gas main. Likewise, our other depot in Gotham is in a much more rural area and doesn’t even have gas in the workshop.”

Future options

“For every kg of gas we inject into a bus, we buy a kg of bio-methane, which is a renewable energy source,” said Gary. “We buy through Air Liquide, a company involved in all sorts of gas production and distribution, but it’s not the only one. There are a growing number of suppliers.

“It was only a couple of months ago, in response to global warming issues, that the government announced its objective to legislate away from food waste going to landfill. When it goes to landfill it’s attacked by the same microorganisms that are intentionally put into anaerobic digesters to turn that feed stock into bio-methane. In landfill, it’s not captured. It goes into the atmosphere and is actually a much more potent greenhouse gas than CO2 ever is.

“Food waste is one of the key feed stocks for anaerobic digesters, of which more and more are being setup. Not that there’s any shortage of it now, but looking forward it should become more readily available and it’s not just bus operators that see it as a viable option. It’s haulage companies as well.

“The infrastructure needs to be there, but I don’t think that should be an obstacle to wider adoption. Compared to the cost of a new bus, it’s the smaller cost. We pay road fuel duty on our gas the same way we do on our diesel. It’s treated no differently.

“By the end of this year we will have our 120 gas double-deckers and there will be 112 Euro V ’deckers retrofitted with exhaust treatment systems, as will 68 midibuses operating out of Trent Bridge. In addition to the new midibuses we’re buying, it means the average age of the fleet will be quite a bit under six years and we won’t need to replace any more ‘deckers until 2022 – quite something for a commercial bus operation.

“We still have to make a profit and have shareholders that expect a dividend at the end of each year. Fortunately our majority shareholder is the city council which appreciates what we term as the social dividend – the benefit we provide to the citizens they represent and that counts.

“Who knows what is going to be the best fuel by 2022, such is the way technology is changing. For us, it might be more gas or, if we can get the range, an electric double-decker. It might be a fuel cell vehicle. Our upgraded Euro V midibus fleet will fall due for replacement by 2022 and I suspect we could look at electric, but cost will be an issue.

“What is for sure is that we want to keep refreshing the fleet. We want it to be young, clean and as green as possible, but what will be the best way of achieving that once we get into the next decade remains to be seen. It’s exciting times.”

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