5.3.2 Rail

Railway transport is widely used in many countries. In Europe and Japan, electricity is a major energy source for rail, while diesel is a major source in North America. Coal is also still used in some developing countries. Rail’s main roles are high speed passenger transport between large (remote) cities, high density commuter transport in the city and freight transport over long distances. Railway transport competes with other transport modes, such as air, ship, trucks and private vehicles. Major R&D goals for railway transport are higher speeds, improved comfort, cost reductions, better safety and better punctuality. Many energy efficiency technologies for railways are discussed in the web site of the International Union of Railways.^[29] R&D programmes aimed at CO₂ reduction include:

Reducing aerodynamic resistance

For high speed trains such as the Japanese Shinkansen, French TGV and German ICE, aerodynamic resistance dominates vehicle loads. It is important to reduce this resistance to reduce energy consumption and CO₂ emissions. Aerodynamic resistance is determined by the shape of the train. Therefore, research has been carried out to find the optimum shape by using computer simulation and wind tunnel testing. The latest series 700 Shinkansen train has reduced aerodynamic resistance by 31% compared with the first generation Shinkansen.

Reducing train weight

Reduction of train weight is an effective way to reduce energy consumption and CO₂ emission. Aluminium car bodies, lightweight bogies and lighter propulsion equipments are proven weight reduction measures.

Regenerative braking

Regenerative brakes have been used in railways for three decades, but with limited applications. For current systems, the electric energy generated by braking is used through a catenary for powering other trains, reducing energy consumption and CO₂ emissions. However, regenerative braking energy cannot be effectively used when there is no train running near a braking train. Recently research in energy storage device onboard or trackside is progressing in several countries. Lithium ion batteries, ultracapacitors and flywheels are candidates for such energy storage devices.

Higher efficiency propulsion system

Recent research on rail propulsion has focused on superconducting on-board transformers and permanent magnet synchronous traction motors.

Apart from the above technologies mainly for electric trains, there are several promising technologies for diesel swichers, including common rail injection system and hybridization/on-board use of braking energy in diesel-electric vehicles (see the web site of the International Union of Railways),