Head-end power

In rail transport, head-end power (HEP), also known as electric train supply (ETS) is the electrical power distribution system on a passenger train. The power source, usually a locomotive (or a generator car) at the front or 'head' of a train, provides the electricity used for heating, lighting, electrical and other 'hotel' needs. The maritime equivalent is hotel electric power. A successful attempt by the London, Brighton and South Coast Railway in October 1881 to light the passenger car between London and Brighton heralded the beginning of using electricity to light trains in the world. Oil lamps were introduced in 1842 to light trains. Economics drove the Lancashire and Yorkshire Railway to replace oil with coal gas lighting in 1870, but a gas cylinder explosion on the train led them to abandon the experiment. Oil-gas lighting was introduced in late 1870. Electrical lighting was introduced in October 1881 by using twelve Swan carbon filament incandescent lamps connected to an underslung battery of 32 Faure lead-acid rechargeable cells, suitable for about 6 hours lighting before being removed for recharging. The North British Railway in 1881 successfully generated electricity using a dynamo on the Brotherhood steam locomotive to provide electrical lighting in a train, a concept that was later called head-end power. High steam consumption led to abandonment of the system. Three trains were started in 1883 by London, Brighton and South Coast Railway with electricity generated on board using a dynamo driven from one of the axles. This charged a lead-acid battery in the guard's van, and the guard operated and maintained the equipment. The system successfully provided electric lighting in the train. In 1887, steam-driven generators in the baggage cars of the Florida Special and the Chicago Limited trains in the US supplied electric lighting to all the cars of the train by wiring them, to introduce the other form of head-end power. The oil-gas lighting provided a higher intensity of light compared to electric lighting and was more popularly used until September 1913, when an accident on the Midland Railway at Aisgill caused a large number of passenger deaths. This accident prompted railways to adopt electricity for lighting the trains. Throughout the remainder of the age of steam and into the early diesel era, passenger cars were heated by low pressure saturated steam supplied by the locomotive, with the electricity for car lighting and ventilation being derived from batteries charged by axle-driven generators on each car, or from engine-generator sets mounted under the carbody. Starting in the 1930s, air conditioning became available on railcars, with the energy to run them being provided by mechanical power take offs from the axle, small dedicated engines or propane.