DB AG made several test series on natural gas propulsion:

CNG vehicle at Usedomer Bäderbahn, LNG vehicle for shunting locomotive.

SNCF has a project for a regional railcar running with natural gas, using a 228 kW MAN gas engine.

Medium (Considerable optimisation expected on the basis of present materials and construction principles and improvement by < factor 2 in all fields)

Further progress in ANG technology to be expected.

Higher engine powers (500-2000 kW) needed for railway applications. There is an need for further R&D. Engines for 1500 kW and more presently only exist for stationary applications. Engine control has to be adapted to railway situation with constantly changing operation points.

• Provide clean alternative to diesel propulsion in terms of pollution and noise.
• Provide alternative fuel in view of limited petrol reservoirs

Costs

Low cost compared to other diesel alternatives (e.g. fuel cell).

Infrastructure

Solutions are possible without heavy installations (simple links to the existing distribution networks)

Resource supplies

Longer supply range than diesel (cf. General criteria - Benefits).

Emissions

Although today’s diesel vehicles generate quite low emissions, the key strength of thegas-powered version is to cut emissions down to levels never achieved before by an internalcombustion railcar.

Engine power

Available natural gas engines can only cover the low end of power classes needed for railway applications. More powerful gas engines only exist for stationary applications.

Technological know-how

There is virtually no experience with natural gas technology in railways, neither for propulsion system nor for fuel supply and handling.

Additional supply infrastructure

One problem is the need for an alternative supply system which can become costly, especially since there is no experience with natural gas infrastructure. Therefore a favoured application would be for a closed fleet, e.g. on an island or at a shunting station. Interoperability is problematic even on a national scale as long as natural gas infrastructure is confined to isolated parts of the network.

Operation range

Another problem is the lower operation range due to lower energy density of the fuel. Storage technology needs further progress. Energy content per volume for CNG and LNG solutions is still low compared to diesel (50% for LNG, 25% for CNG). The CNG vehicles tested in Usedom, Germany, had an operation range of about 500 - 600 km as compared to 800 - 900 km for equivalent diesel vehicles. This disadvantage can be substantially reduced if dedicated vehicles are designed.

Initial investment

Compared to diesel, initial investment for conversion to natural gas technology is still high.

Resource limitation

Although natural gas has a higher time range than diesel, it is a limited resource and therefore again a temporary solution.

DB AG gives the following success factors for a wide-spread introduction of natural gas propulsion:

• Availability of natural gas engines in higher power range for locomotives as well as for under-floor integration (for MUs).
• Further development of gas engine technology to improve efficiency at low load
• Reduction of higher costs of gas technology as compared to diesel technology
• Development of supply infrastructure
• low price for natural gas and long-term calculability (taxation)

LNG shunting locomotive at DB AG

DB AG has refitted a class BR 360 diesel-hydraulic shunting locomotive with a natural gas engine (Caterpillar G 3508 TA-54) and a 810 liter LNG tank system (by Linde). To fuel the vehicle an LNG station was constructed near Munich main station.