"Please could you tell me how many MW of electricity the trains will use when they are operational? Also, how much electricity will be used by the stations themselves, and what will happen when there are power outages?"Their reply was:
"We cannot say for sure what this will during operation as we’re still in the construction phase. This will also depend on various aspects that still need to be finalised from now until the operational phase."According to the information brochure dated 15 April 2007, page 4, there will be 24 trains of 4 cars each. No mention is made of the power requirements. In fact, the words "power" and "electricity" are entirely absent from the 23 page document. They are also absent from this and this document too. Considering that the Koeberg blackouts had lasted for several weeks a year before, and Eskom had already issued warnings about power shortages for years to come, these documents, coming a year later, are surprisingly short-sighted.
According to Wikipedia, the trains are of the Electrostar family. I found further information on these locomotives, including the following:
Bodywork is aluminium, with steel ends. There are two Adtranz 250kW three-phase traction motors on each motor coach, with IGBT control. The motor bogies are at the trailing end of the driving coaches and at the centre of the unit on the non-driving coach. Bogies are a development of the BREL P3 and T3 design used on class 465/0 and 465/1. Driving coaches have pick up shoes on both bogies. Classes 375 and 377 have a potential maximum speed of 160km/h, but do not normally operate at more than 140 km/h.Assuming a motor coach on each end, each train will use 1MW of power, so the entire system would consume 24MW, excluding lighting, power consumption at each station, and power loss due to normal transmission. Given the fact that the Kelvin power station produces a maximum of 600MW, this one project will use 4% of the power station's entire output, capacity it simply doesn't have. It already only provides less than a third of the city's power requirements.
Update 30 Jan 2008: I finally got an answer of sorts (see comment below). I under-estimated the power requirements (it's 28.8MW), and the only mention on the web site can be found here.
- The rail cars are known as Electric Multiple Units (EMUs) and will be powered from overhead electrification wires at a voltage of 25kVAC.
- An EMU allows distributed power along the train and in the case of the Gautrain, twelve of the sixteen axles of a four car train unit are provided with 200kW electric motors (a motorisation ratio of 75%), leading to a relative high power to weight ratio of approximately 11 kW per ton. This power to weight ratio ensures the high levels of acceleration and deceleration required to achieve the required maximum journey times specified of 42 minutes from Johannesburg Park station to Hatfield station.
- Having distributed power allows the train to climb gradients significantly steeper than on the national rail network. The direct alignment needed to achieve the shortest distance between the specified stations requires gradients of up to 4% which is significantly steeper than normal railway main line gradients which are normally restricted to 1,5% or occasionally 2% in special instances. The Gautrain has a motorisation ratio of 75% which could allow it to climb gradients in excess of 10%.
- The use of a high voltage alternating current (AC) system permits the entire Gautrain system to be fed from a single electrical traction substation which will be located at the Gautrain Midrand Depot. The traction substation will be provided with two independent supplies from Eskom to ensure reliability of electrical power supply.
- All train units will be provided with blended braking systems. Once it is decided to brake a train, the system first goes into regenerative braking mode, thus using its electric motors as brakes. The electrical power is then supplied back into the overhead lines and can then be used by other trains in the system that are accelerating or are otherwise in a power receptive (consuming) mode. Should there be no receptive trains, then the power will be fed back to Eskom supply, thus ensuring efficient electrical usage characteristics throughout the system. Should higher levels of braking be required this can be provided by the motors, the system then automatically applies the disc brakes. Disc brakes are provided on all wheels and the configuration is similar to advanced modern motor vehicle disc braking systems, being fitted with an Anti-skid Braking System (ABS).