After examining the options involved in going over to gas power, UK supermarket company, Waitrose decided on going over to gas and running a few CNG powered trucks in its fleet to assess its effectiveness.
“We are on a bit of a journey,” says SimonGray, Waitrose Vehicle Engineering Manager. “We are keen to lower our carbon output and do the right things for the environment. We don’t take the manufacturers word for it. If they tell us these tyres will do X or Y, we will always test it ourselves, independently. Whatever we do has to fit with the Waitrose way of doing things.
“We had some dual fuel trucks and that was our step into doing CNG powered vehicles. We purchased two gas powered Scanias last year, based at our Leyland DC, because there is a CNG filling station there. We tested it ourselves, it is six per cent lower than diesel, in terms of CO2.
“So far, it has a lower operating cost, due to the price of CNG. The price can vary a lot between service stations, it depends how much you pay as to whether it’s economical. We have got a good deal and it all comes from bio-methane sources.”
The incentive to reduce fuel use, comes from the fact the UK has some of the most expensive diesel in the world. Operators pay 93 cents a litre in fuel duty alone. With these kinds of prices CNG, even with limited access to the fuel, becomes a more attractive proposition. Another factor is a promise by the government not to alter duty on CNG before 2024. This means investing in a truck now has some certainty of fuel cost over its entire lifetime.
Currently, the higher purchase price for a CNG-powered truck can be recovered in the first two years with the trucks travelling 160,000 km per year. The working life for a truck in the fleet is normally 6-7 years, so the business case is made. In terms of tare weight the penalty for going with CNG is just under one tonne. This is due to the weight of the CNG tanks themselves, which are thick walled pressure vessels.
The two evaluation trucks were joined by a further ten in 2016 and then another 50 this year as the trial ramps up. Waitrose monitor the trial at each step before committing to the next phase.
“The two we have are being monitored all of the time,” says Gray. “We compare them to the diesel comparators, we measure them all of the time as well. We ensure they are doing the same sort of job. All of our vehicles have telematics on them, so we know exactly where they are being driven, so we are comparing like for like. We have also done independent testing, funded by the government.”
On average these semis are running at 25 tonnes GCM with a single drive prime mover and tandem axle trailer. As a result tare is not an issue, as the maximum GCM allowed on UK roads for this combination is 32 tonnes.
“You have CNG and LNG, and in the early days we decided to go with CNG,” says Gray. “Looking at it from well to wheel, CNG is far superior. You are not just looking at tailpipe emissions, it’s the entire carbon footprint.
“The problem with CNG is the range. It’s 356 miles (573 km), we know it’s exactly that, because one of the trucks broke down about 400 yards before the filling station. We went to Scania to begin with and told them the tanks they were selling at the time were no good. They listened to what we said and bespoke tanks are being made for the new trucks, from carbon fibre. These will extend the capacity in the available chassis space and get up to a 500 mile (800 km) range. This means we could use them anywhere in our fleet.”
The trucks are proving to be popular with the drivers, as they are quieter and the CNG engine comes with an Allison transmission. The Allison is fitted with a five stage retarder, as well, necessary, as the CNG engine offers little in the way of engine retardation. Engineering by Scania for the next generation of CNG engines will include an Opticruise AMT and retarder package, coupled with the nine litre.
The CNG engine is rated at 340 hp, whereas the diesel version runs at 325 hp from the nine litre Scania engine. The power and torque curves, when comparing the CNG with the diesel, are almost identical.