In Hungary, the rationale for replacing older model diesel buses with new model Compressed Natural Gas (CNG) buses has been justified by the outcomes of a study organised by Magyar Gázüzemű Közlekedés Klaszter Egyesület (MGKKE) — Hungary’s natural gas vehicle association, in conjunction with the Scientific Institute of Transport (KTI) and others.
In March this year, the city of Miskolc received 75 compressed natural gas (CNG) -powered buses – 40 solo and 35 articulated MAN Lion’s City CNG vehicles, all rated Euro VI. The buses were acquired as part of the European Union co-funded PAN-LNG Project, financed throught the Connecting Europe Facility (CEF) program.
MGKKE instigated the PAN-LNG project in order to develop refueling infrastrucure for CNG and LNG vehicles, to construct the first filling stations, and to ensure integrity of gas supply. In this project at least five filling stations are planned for in Hungary, serving long-distance cargo transport as well as local transport, offering liquefied and compressed natural gas by 2017.
Now, thanks to this cooperation, Hungary has had the opportunity to measure the emission level under real conditions for the very first time. The measurements which were carried out with the portable emission measurement system (PEMS) device from AVL, confirmed the expectations associated with natural gas, said Henrik Domanovszky Henrik, the president of MGKKE.
As part of the PAN-LNG Project, the KTI installed for the first time in Hungary the PEMS device, which is able to continuously analyze the composition and quantity of the gases during real operation. “With this device in Miskolc, we wanted to find out how much impact we can achieve with the installation of a clean gas-powered fleet,” said Domanovszky.
Although the 75 new CNG buses all replaced old diesel vehcles, still there is a significant ageing diesel fleet in Miskolc and MGKKE is arguing for further adoption of natural gas for public transportation. Domanovsky argues that despite being fitted with diesel particulate filter (DPF) assemblies, older diesel buses produce nitrogen oxide compounds that are toxic to wildlife, erode the city environment, and contribute to smog formation.
For the comparison with the new gas-powered buses, MVK, the city owned transportation company (Miskolc Városi Közlekedési Zrt.) provided a bus from its fleet that is fully operational with a relatively advanced Euro IV diesel powertrain, fitted with a particulate filter. To assist the comparison, the vehicle chosen is fundamentally of the same design as the new CNG articulated buses and manufactured also by MAN. The buses carried the same load, equivalent to 90 passengers, and were driven over three typical city routes.
Diesel-Powered: Neoplan 489 EURO IV (Tested 21.-25th of March 2016)
Gas-Powered: MAN Lions City GL EURO VI (Tested 29th of March to 1st of April 2016)
The tests demonstrated the gas-powered bus released 99.2% less nitrogen dioxide (NOx) into the air than the diesel-powered one.
Not visually blowing smoke, the diesel powered bus showed the effectiveness of the DPF. But despite this, MGKKE ‘s president explains the test showed the severe carcinogenic effects of diesel continues to prevail because the remaining particles on the filter paper of the measuring equipment are so small that they can get through the lungs into the bloodstream without any barriers. “In contrast, the gas engine does not need a particulate filter, because the natural gas does not have any components which could develop soot formation during the burning process. Particle matter is reduced by 80% compared to particulate matter from the bus equipped with DPF, with released particles so small they fall into the 10-100 nanometer range,” Henrik Domanovszky told NGV Global News.
The 75 buses are expected to travel 4.25 million kilometers this year in and around Miskolc. These vehicles release 66 tons less nitrogen oxide to the air of the city every year compared with the same amount of diesel buses.
The series of measurements gathered a lot of practical experience and information about the use of the PEMS device, and about the environmental impact regarding the different fueled busses. Based on the success of the trials, the test partners believe it necessary to continue the emissions testing project in other major cities of the country, and on other buses which are of different type and have different technical parameters.
“In the long term this kind of measuring practice should be a target on other segments of the road vehicles, as well on non-road applications too,” said Szabados György of KTI.
99,2 % less NOx, 80% less PM and 20% CO2 emission compared to a diesel bus, equipped by DPF, during real daily drive conditions.