The project manager for natural gas storage systems championed monovalent CNG technology at Magna Steyr. Here he shares with Eliot Lobo the benefits of a lightweight cylinder his group has developed and the prospects he sees for its adoption in India.

Autocar Pro News DeskBy Autocar Pro News Desk calendar 19 Apr 2010 Views icon3011 Views Share - Share to Facebook Share to Twitter Share to LinkedIn Share to Whatsapp

When did Magna Steyr start its work on CNG systems?
We were dealing with LPG buses 20 years ago. They were very early concepts with gas for city buses, but the technology was not standard at the time. The Mila single-seat sportscar we presented four years ago was the development for which we first started to deal with CNG technology and CNG cylinders. At that time we used a lightweight cylinder of Type 3, made up of an aluminium liner fully wrapped in carbon fibre. We wanted to demonstrate that we could engineer a sporty, fun-to-drive car with low emissions and high fuel efficiency. This was a monovalent CNG car and had a range of 250 km.

How different are “dedicated” CNG vehicles from petrol vehicles that are modified to run on CNG?
It depends on the design of the base engine. Normally the part-load fuel efficiency of a naturally aspirated (NA) gas engine with an unmodified compression ratio is lower compared to petrol, because of a different thermodynamic behaviour of natural gas/biogas in the engine. NA engines with standard intake injection or a venturi mixture system (carburettor) achieve a lower filling grade as the gaseous fuel displaces the intake air. The fuel’s potential to pre-ignite compensates only marginally for this reduced engine performance.Dedicated CNG engines on the other hand use a higher compression ratio compared to standard petrol mode or are turbocharged or supercharged to make them as efficient as the base petrol engines in part-load conditions. We have seen that at wide-open throttle the efficiency of our supercharged Mila natural gas engine is 23 percent higher because the high knock-resistance of methane allowed us to advance the ignition by 45deg, compared to a permissible maximum of 22deg for a petrol engine, resulting in lower peak pressure and lower exhaust gas temperature.We have further seen that enrichment of the gas/air mixture above stoichiometry leads to misfiring and therefore is to be avoided, while base engines use between 10 and 20 percent.The difference a real efficient, dedicated CNG/biogas engine can make is manifested in two ways today. One, with turbo- and supercharging the engine has the same performance as with petrol. Two, such charged engines are used for downsizing, i.e. using a powerful, durable gas engine with a displacement that is one step smaller, e.g. 1.4 litres instead of 1.6 or even 1.8 litres, for the same vehicle. This is achieved by means of mechanical measures like increasing the compression ratio and using more robust piston rings, exhaust valves, and valve seat rings.

There’s a lot of hype surrounding hybrids. Which in your opinion is more suitable for India as a passenger car technology — hybrids or CNG?
Hybrids have the potential to be totally clean, when they eventually evolve into all-electric vehicles. But CNG is an existing technology that gives you good fuel efficiency and allows you to reduce CO2 emissions — today. There are many examples of dedicated CNG vehicles. Europe particularly is very progressive in dedicated engine and vehicle technology for CNG. But the one problem you have with CNG is range. The density of natural gas is lower, even when stored at 200 bar, than petrol or diesel. And this requires you to use good packaging technology on the car.We’ve been working on this integration technology for the last two or three years, and have found a good way to install CNG tanks without reducing the volume of the inner compartment. This is the bottom-mount cylinder technology.If you want a range similar to a petrol vehicle, 500–550km on a medium-class passenger car, you need a minimum of three cylinders and a storage capacity of between 140 and 160 litres. With steel technology the weight of the cylinder is 1kg per litre of gas stored, maybe even more. So there you have an additional weight of 140 or 160kg with the cylinders alone.

Are you aware of any Indian OEM that wants to produce a CNG car?
At the moment monovalent vehicles are only for local use. It’s especially city transports – buses, waste handling and community vehicles – that use monovalent systems. In cases of a low CNG network density, passenger car OEMs normally install bifuel systems with reserve or full-capacity petrol tanks because of low CNG supply in regions outside the big cities. For local use it is a decision by the company or community to use monovalent CNG vehicles. The benefit would be a wider driving distance using the greater available installation space.

Would you offer such an OEM a bottom-mounted steel cylinder module? What about the weight?
At the moment we will not offer steel cylinder modules. What we can offer is CNG engineered modules that differ in installed weight from both steel and lightweight composites, modules which combine Type 4 lightweight cylinders with steel cylinders. The weight reduction potential with Type 4 cylinders is 75 percent compared to steel — the weight of a carbon fibre cylinder is only 250g per litre. For a passenger car this is between 50kg and 120kg, for a bus between 500kg and 1,000kg. But carbon fibre is expensive, and it drives the price of a lightweight cylinder up.

How do you “bottom-mount” a CNG module on a saloon car?
Modern systems consisting of CNG pressure cylinders are mounted from outside to the bottom of the car (belly mounted) and hang from the bottom platform. It is important to design the platform and rear axle in such a way that the cylinders (with smaller diameters than the type installed inside the car, but longer and more than one of them) can be positioned between the tyres – for this, a torsion beam rear axle is ideal – or in front of or just behind the axle beams. The diameter of the cylinders depends on the ground clearance of the car — cars with smaller tyres will have smaller cylinder diameters. The rear place for the reserve wheel normally will also be used and the spare tyre will have to be mounted vertically in the inner compartment.

Are you actually doing CNG engine work as well, as part of a full package? Or is it just storage technology?
My role in the Mila project was to integrate the CNG storage technology together with the engine in the car. I worked with colleagues from our chassis division on the tanks. For the engine work we used support from within our company and colleagues from the Institute of Internal Combustion Engines and Thermodynamics at the Graz University of Technology in Austria. We did a lot on car technology because if you are talking about emission reduction for passenger cars, which we deal with mainly in Graz, emissions are produced not only by the engine; they are a combination of engine and car. The mass, the transmission, the thermodynamics of the engine, the catalytic conversion — all these systems work together to produce or to reduce emissions. That’s important. So the application and integration of technology in the car involves not only the engine; it’s a combination of all the systems.

How would you say the tank system contributes to that?
The tank system is one of the systems feeding the engine, but with a higher volume compared to petrol, in the relation of 3:1 or 4:1. So it means three times to four times more volume to find on the car. This is a bodywork package solution — again, a whole-vehicle activity. To find the right package for the cylinders is an engineering challenge that needs high competence. We think we have this competence parallel to the OEMs that make dedicated CNG cars.

Do you have anything that’s commercial right now?
We were talking till now about engineering. We think we can engineer the complete car, organise what you have on the engine, and also test CNG engines and controls. If you are asking about products, a CNG vehicle is similar to a diesel or petrol car — only it has additional systems and parts. It’s a petrol car plus CNG components/systems.At Magna our competence extends from the parts to the total vehicle. And especially for CNG, it is of high interest to us that we can supply CNG modules. We could, of course, supply components, but there is a well-established supply base for valves, plumbing, and the pressure regulator — in Italy, South America, and India. Where we see potential is to supply the total fuel system.

You would make the tanks yourself and integrate the regulating parts and fuel lines?
Yes. And to supply a system for any company it is important to have a main component in it. A main component means either valve parts, or the cylinder. If you supply a system, you must have one part that gives you the potential to guarantee the system.

Do you have such a system available, or is it still in development? What prospects do you see in India?
We know that there are well-established after-sales solutions here in India and also in a lot of other countries. And real volumes of CNG solutions today are after-sales solutions. But who guarantees their entire functioning on the car? This is an emerging problem that OEMs must take responsibility for, and the OEMs are thinking in terms of creating their own CNG versions so they can offer a real guarantee on their cars. As Magna we could supply modules to these OEMs.

Will you also look at the aftermarket?
After-sales installations require high flexibility. Since we are talking of systems here and not just cylinders, a decision to do aftermarket business requires that we balance the development effort against the potential sales volume. Besides, the guarantee we can offer on aftermarket systems is only partial, whereas OEM solutions for CNG give a complete vehicle and engine guarantee. This because the full car has been developed by the OEM for the alternative drive plus storage system, and the customer gets full service support from the OEM’s authorised service stations.So Magna Steyr is looking for volume supply of systems to OEMs. If the aftermarket requires volumes, this can be of business interest too but the warranty will be different and only for the cylinder itself.

What technology would you offer there?
It depends. At the beginning you asked about the price level of CNG systems, the add-on price to be amortised by the fuel price. The end-customer wants a system at a low price. And we understand this because we are working on these business cases for different countries. And we found that there is a big difference in add-on price relation between India and Europe. In Europe an add-on system costs 2,000–4,200 euros for a car. We found installations in India cost Rs 50,000–90,000, which is 900–1,500 euros, to the final customer. This is a big difference, and so the steel version is now installed as a single bottle in the rear compartment of the car, which lowers comfort, and restricts the range to 150–220km.We think the next generation on the market will have to offer a bigger range. Then the OEMs must think of a platform that allows them to integrate two cylinders, on the bottom of the car. So the price will increase, but hopefully not too much for the end-customer. And steel cylinders have a good price, they are well suited.

But steel cylinders are not your technology…
We can supply a mix of lightweight bottles and steel cylinders. This is a compromise, but it really depends on the guarantee. We will need to make a compromise with the OEM or the final supplier on the guarantee — after all, the relation of added value to cost must be in a region we can handle. On lightweight systems, which are mainly needed today already for buses, where they are top-mounted, you have to use lightweight cylinders. And this is a business that is of interest to our company. On passenger cars it depends on how many cylinders you install and how much additional weight is acceptable for reasons of driveability, comfort, and so on. If the range of Indian cars is to be improved to 500km, you will definitely need lightweight cylinders. And then it is of high interest to our company to supply these systems.

Is this a realistic compromise? What about warranty for a module consisting of one steel and one composite cylinder?
There is no difference. Because each of the cylinders must fulfil the safety and lifetime requirements by itself. There is a difference in installation between retrofitted and dedicated OEM-base CNG vehicles. Both must be safe and differ therefore in their installation form. So a combination of both types of cylinders is a potential to mix price and weight for final customer requests.

In truck applications it makes great sense to have lightweight cylinders because they allow you that much more payload. Is this an area where you could really offer value to an Indian OEM?
We can offer lightweight modules for local distribution trucks, where you have a good compromise between fuel capacity and daily range. While the efficiency of diesel is still highest, with CNG you achieve a good efficiency compromise. On the other hand you have extremely low particulates and a good CO2 relation compared to petrol. Particularly if you have an environmental mandate, this is a good alternative. In big cities it is a solution you can easily use because you have the supply network of gas.

You said this is necessary for buses, with roof-mounted cylinders. What is the technology that is current in Europe?
In Europe it is ultra-lightweight cylinders. They use Type 4 composite cylinders already because the frame construction needs this light weight for CNG. And a lot of cities are thinking of converting their diesel fleets into CNG. And to have similar lifetime as with diesel, or to extend the lifetime with roof mounting you must use lightweight cylinders.

Do you think busbuilders in India will be interested in this?
Definitely. Many of the global bus OEMs use Type 4 technology already and are highly interested. In India I guess they are using steel at the moment. In modern low-floor and low-entry buses there is no place for CNG bottles in the rear compartment or in the floor; they have to be fitted atop the roof. And then you cannot carry – without problems – two tonnes on the roof. If you don’t use lightweight cylinders you will remarkably reduce the life of your frame, and the operator will have to invest in a replacement early.

Magna Powertrain’s Engineering Centre Steyr does bus work as well, and you do the CNG. So how much can Magna bring to a bus development? Can you together do a complete CNG bus?
Yes, why not? Our sister company ECS in Sankt Valentin has a long tradition in trucks, buses, heavy duty vehicles, and engines. And that means this combination of our facility and our colleagues also in India, together with the heavy duty truck group, is a unique synergy. In fact we are already working together — every week we meet together in Graz or St Valentin to discuss ongoing projects in the heavy duty business.

If you have to put this tank on a bus, what is different? Are there any additional safety devices needed?
If you use it on a bus, you have a mass on the roof which you haven’t had before, so you must do two things — one, a lifetime validation, which can be done on a testbed for a CNG module. And then you must also undertake a lifetime investigation of the additional mass on the top. This is a dynamic shake test with a high mass system. If you have a big test bed, like we do in St Valentin, you can do it this way. But you can even run it on a local test track. At ECS in St Valentin they have a very well-appointed test facility for heavy duty applications, but in India our test engineers could run it at the customer test facility.

How would you do an entire integration here in India?
We can handle any development from concept phase up to project management in any form that the customer wants. That’s easy, because within Magna we have just one project management team that the OEM deals with, and we have strictly standardised ongoing how we manage projects, no matter where they are. The project team is responsible for the product, regardless of which Magna facilities are involved.The vehicle development is normally handled by the OEM, because CNG is quite a new development for many of them. But after a concept phase together with the OEM we could also do the complete integration and vehicle validation if the OEM asks us to.

Do you have projects for CNG in India?
We’ve already had a number of interesting meetings with OEM customers, and there is a high interest in our lightweight solutions for passenger cars as well as for buses. Not much for the trucks at the moment, but who knows?It’s important to understand that a module is different from a cylinder alone. From our experience of developing and assembling passenger cars and heavy duty vehicles, we think we understand the needs of the OEMs more in detail as to the overall application than in terms of single parts.

What do you expect your first orders for Type 4 cylinders/modules to be for — a commercial vehicle or a passenger car?
I think either is possible, depending on the market price level we can achieve. The amortisation could be greater and faster on commercial vehicles – owing to the number of passengers carried and the distances travelled – and taxis. Passenger car customers are more sensitive to the system price because of the longer amortisation owing to lower driving ranges per year than commercial vehicles.

Where do you see the better prospects in India?
Today we think buses have the more urgent need for a lightweight system on top. This is related to the life of the body. We might have have an opportunity to enter the passenger car market in the future when the required driving distances with CNG go up and the significant additional weight of steel cylinders is no longer acceptable.

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