16. 3. 2020

Eco-friendlier, affordable, and available today: CNG powertrains. Biomethane and synthetic gas can achieve up to 90-per-cent and full carbon neutrality respectively.

Natural gas vehicles are a well-known alternative for efficient and eco-friendly individual mobility and are popular in many European countries. Vehicles like the all-new ŠKODA OCTAVIA G-TEC due to be released in the second half of 2020 and the already available G TEC versions of the ŠKODA SCALA and KAMIQ enable immediate CO2 savings of around 25 per cent compared to a conventional petrol engine, depending on the origin and production method of the gas used. Biomethane and synthetic gas can achieve up to 90-per-cent and full carbon neutrality respectively. Yet G-TEC models are perfectly suited for everyday driving, with the same Simply Clever benefits as any other ŠKODA model, and provide undiminished comfort and driving pleasure. The G-TEC models of SCALA, KAMIQ and OCTAVIA will remain in the ŠKODA model range for several years to come.

Cleaner combustion and a higher energy content than petrol and diesel are two of the key advantages of compressed natural gas (CNG). In addition, it can be topped up as easily and quickly as conventional fuels at suitably equipped filling stations. With the European network of CNG stations continually expanding, mid-2019 saw Italy in the lead in Europe with close to 1,300 filling stations, ahead of Germany with around 900. The Czech Republic came in third place, followed by Sweden and the Netherlands, all approaching the 200 mark.

Larger CNG tanks ensure excellent range
The design of the new ŠKODA G-TEC versions of the SCALA, the KAMIQ and the all-new OCTAVIA generation features larger CNG tanks, with the resulting greater ranges enabling drivers to cover even longer journeys using the more eco-friendly and economical CNG mode for the most part. Meanwhile, additional 9-litre petrol tanks safeguard mobility in regions without CNG filling stations. ŠKODA AUTO took great pains in development to ensure that the engines will run almost exclusively on natural gas.

In CNG mode, running on natural gas, these cars emit 25 per cent fewer CO2 emissions than vehicles powered by a conventional petrol engine. When adding a 20-per-cent share of bio-CNG, as is currently common in Germany, CO2 emissions are reduced by as much as 35 to 40 per cent. Using an even higher bio-CNG proportion made from plant residues and biological waste can achieve improvements of up to 90 per cent, approaching carbon neutrality. Full carbon neutrality can be achieved when running on synthetic methane produced from renewable energy using a power-to-gas process. However, this technology is currently still in development.

Significant reduction of fuel costs
CNG has a higher energy content than petrol or diesel and is cheaper to buy. This significantly reduces fuel costs for each journey. In Germany, the single largest European market for ŠKODA, the price advantage over diesel-powered vehicles comes in at around 40 per cent, and as much as 50 per cent for petrol engines. Even greater savings can be achieved in Italy, due to higher petrol and diesel prices.

The all-new ŠKODA OCTAVIA G-TEC due to be launched in the second half of 2020 has a 1.5-litre four-cylinder TSI engine delivering 96 kW (130 PS), which enables sprightly performance. Its three CNG tanks have a joint capacity of 17.3 kilograms, allowing for a range of up to 480 kilometres in CNG mode. The 1.0-litre TSI in the SCALA G-TEC and the KAMIQ G-TEC produces an output of 66 kW (90 PS). In both models, the three CNG tanks have a capacity of 13.8 kilograms – equivalent to a CNG-only range of around 410 kilometres in the SCALA and KAMIQ.

G-TEC engines specially modified for CNG use
Compared to the standard engine and to enable it to run on CNG, the 1.0 G-TEC is fitted with different intake and exhaust cams, a redesigned cylinder head and a new induction tract as well as special CNG-compatible injector nozzles and particularly heat-resistant exhaust valves. In addition, an electronic control unit reduces the pressure of the gas in two stages: the first mechanically reduces the pressure in the tanks from 200 bar to around 20 bar; in the second stage, a solenoid valve is used to lower the pressure to the absolute working level of between 9 and 5 bar prevalent in the low-pressure system. The 1.5 G-TEC features similar modifications. It is also designed to support a high 12.5:1 compression ratio and uses the so-called Miller cycle, with the inlet valves remaining open slightly longer during the compression stroke. A turbocharger with variable turbine geometry ensures timely and even build-up of charging pressure.

ŠKODA G-TEC models “make an important, additional contribution to reducing CO₂ emissions”

With the G-TEC variants of the all-new OCTAVIA as well as the SCALA and KAMIQ, ŠKODA will in future offer a choice of three models designed to run on efficient and eco-friendly compressed natural gas (CNG). CNG vehicles produce hardly any nitrogen oxides (NOx) and enable an instant reduction in CO₂ emissions of around 25 per cent or even significantly more, compared to cars with conventional internal-combustion engines. In the interview below, Philip Paul, CNG expert and Head of ŠKODA SUV Product Marketing, explains the benefits and technical details of CNG engines.

What role will natural gas (CNG) play in ŠKODA’s fuel/energy mix over the coming years?

Philip Paul: Even though electric mobility will be the leading technology over the next few years, CNG technology is set to make an important, additional contribution to reducing CO₂ emissions. It’s cleaner, with fuel costs lower than those of conventional internal-combustion engines, but, most importantly, it is effective and available today. In addition, natural gas burns nearly without particles. Even when using gas from natural deposits, CO₂ reductions are up to 25 per cent lower than with petrol. Adding 20 per cent of biomethane, as is currently done in Germany, for instance, makes for even greater CO₂ reductions of 35 to 40 per cent. And once you start using 100 per cent biomethane from plant material or even synthetic methane produced from renewable energy, the ŠKODA G-TEC models can actually achieve carbon neutrality.

On the other hand, Volkswagen board members have recently said that they want to move away from CNG engines and will stop developing this technology. How can those two views be reconciled?

Paul: There is no contradiction between the current range of CNG models and these statements on long-term development. The automotive industry engages in very long-range planning, with strategies designed for as much as a decade ahead. Therefore, CNG engines will continue to be a part of the range over the coming years. At ŠKODA, this also includes the recently launched G-TEC versions of the SCALA, KAMIQ and the natural gas variant of the new OCTAVIA, which will soon be launched in the first markets.

Does it make a difference whether a ŠKODA G-TEC vehicle is powered by natural gas, biomethane or synthetic methane?

Paul: To the vehicle or the customer it makes no difference at all, but it makes a big difference to the environment. Biomethane and synthetic methane, also known as e-gas, are so-called drop-in energy sources which can be added to natural gas in any combination. There is no need for technical modifications to the engine or the vehicle. Biomethane manufactured entirely from plant residues or biological waste and using renewable energy is already available today and on offer at filling stations. It enables drivers to reduce their CO₂ emissions by a significant amount. Synthetic methane, produced from solar or wind energy, has a similar potential. However, the end product isn’t commercially viable yet and thus only available in smaller quantities.

Unlike petrol or diesel, CNG has to be stored in the vehicle under high pressure. How does this affect safety?

Paul: Our natural gas vehicles are just as safe as comparable models with conventional internal-combustion engines. The CNG tanks installed in the ŠKODA G-TEC models are engineered, produced and certified to meet the highest industry standards. They are fitted with a safety valve which, in the unlikely event of a technical problem, ensures that the gas is released in a controlled manner. CNG is non-toxic and lighter than air, so it dissipates quickly. In addition, all the CNG tank components are designed to withstand extreme conditions. The pressure inside the tank is around 200 bar. However, these tanks are designed and approved for pressures up to 600 bar, which is three times what they usually encounter in practice.

Why do G-TEC engines still have to use petrol in certain situations?

Paul: This is usually only required for a very short time during cold starts and immediately after refuelling. Our top priority in development has always been that the engine should run almost exclusively on natural gas. Even when outside temperatures drop to –10 °C, a warm engine can be started in CNG mode, and drivers can also use the Stop/Start feature without any issues. There is a persistent myth that very low temperatures below freezing could cause problems for natural gas. But for CNG to liquefy inside its tank, the temperature would have to drop below –160 °C according to the laws of physics. In other words: even in the winter season, natural gas is an excellent all-round fuel.

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