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Technical information
How the buses work
The hybrid bus uses two different power sources. They are an electric motor and a Capstone Micro-Turbine engine, an electric motor powers the bus, and the turbine engine keeps the batteries charged, only requiring a trickle charge during off road time at the depot This contrasts with all-electric buses which use batteries charged by an external source. Benefits of the hybrid design include the following:
The vehicle is lighter than a purely electric vehicle of comparable size and power because only eighty batteries are needed.
The turbine engine in the vehicle is much smaller, lighter, and more efficient than the one in a conventional vehicle, because the electric motor can asked to provide a boost of power for acceleration.
Braking in a hybrid vehicle is assisted by the electric motor which recaptures part of the kinetic energy of the bus to partially recharge the batteries. This is called regenerative braking and one of the reasons for the high efficiency of hybrid buses. In a conventional vehicle with internal-combustion engine braking is done only by mechanical brakes, and the kinetic energy of the vehicle is wasted as heat.
Power is supplied from sealed lead acid gel, batteries; a Capstone Micro Turbine (TM) charges the batteries as required. The Turbine is fuelled with Diesel oil and meets Euro III 1999 Enhanced Environmentally Friendly Vehicles (EEV) standards.
Top speed can be set at 80-km/h, 22-km/h average speed and 340 maximum distance in a day, all with virtually zero emissions. This means the vehicle is suitable for virtually all city operations.
In the case of the Olymbus, it is plugged in to an electric supply point, rather like a caravan power connection whilst it is in its depot overnight, When it is about to leave the depot it is uncoupled and runs on its batteries until the system detects that they are becoming discharged. The Capstone Turbine then starts automatically and its attached generator re-charges the batteries as required.
The traction motor is attached to the input side of a conventional differential, which in turn drives the rear road wheels. The motor is water-cooled and therefore can cope with loadings which require it to produce more power when required on the hilly QuayLink route
All ancillaries such as turbine fuel pump, and turbine starting igniters are electically driven, and are designed for low maintenance
Hot exhaust gases from the turbine are used to pre-heat the inlet air in a recouperater before being ejected at a lower temperature at roof level at the rear.
The result of all this is that the bus is extremely quiet in operation, even when the turbine is operating and it is extremely fuel efficient and "green" when compared with the most modern Diesel engine vehicles.
Performance is excellent, having good acceleration to the comparatively low speeds that the service requires. Power take up is extremely smooth as is braking, thus making for a very smooth journey through the city streets.
(Below) 61005 uses it's regenerative braking to help it to halt at the Guildhall bus stop
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Benefits of a Capstone turbine
 Capstone-energized hybrid-electric buses, deliver benefits unattainable through conventional approaches. Partnering power generation with electricity storage
A micro turbine is a compact turbine generator that delivers electricity close to the point where it is needed. Operating on diesel fuel, this form of distributed generation technology made its commercial debut in 1998. A fleet of Capstone-Energized HEV buses in New Zealand have amassed more than a half-million miles worth of revenue service in their 14-hour/day schedules.
Electric vehicles are clean, but are limited in the distance they can travel between battery charges.
The Capstone Micro Turbine serves as an onboard battery charger, enhancing range, providing added power for air conditioning and consistent acceleration. Thus, the need for daytime battery charging or swapping is eliminated. At night, hybrid-electric vehicles (HEVs) can plug into the local grid, recharging when electric rates are at their lowest. This functionality makes the total fuel cost significantly lower than a conventional diesel or natural gas vehicle. Further, maintenance costs are dramatically reduced since the micro turbine is air-cooled and uses no oil. Regenerative braking also reduces the cost of brake pad replacements:
Capstone MicroTurbines are the only turbine systems being sold in volume for commercial revenue service on urban transit vehicles.
The world's largest hybrid electric bus order to date? 31 buses for the city of Tempe, with an option to buy a total of 200? are exclusively Capstone-energized. The City of Tampa followed suit with an order to buy 18 and an option for 90.
Systems design includes more than 30 patents.
All field operation to date has demonstrated lower maintenance, lower life cycle costs and vastly lower emissions than the best internal combustion engines
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How a Capstone Turbine works
The heart of the Designline Olymbus is the on board power plant, the Capstone C-30 Turbine.
The illustration below shows in principle how this works.
The unit is lightweight and relatively small in dimension and extremely simple in operation. It is about the size of a domestic waste bin and is modular in its concstruction for ease of service.
It has multi-fuel capabilities but in the Olymbus for Tyneside runs on standard Diesel fuel. The fuel is injected by electronically controlled. injectors into the combustion chamber where it is ignited, the resultant expansion of gases passes through the single stage turbine which drives a shaft holding a compressor. The compressor re-charges the combustion chamber and excess air is exhausted to the roof mounted outlet
One feature of the turbine is that it has no bearings, air keeping the surfaces apart in a frictionless way. Thus there is no need for lubricating oil and only one moving part in the engine, i.e. the turbine
The compressor shaft also drives the electric generator which then re-charges the gel-batteries which then provide the energy source for the electric drive motor which eventually propels the bus.
The initial starting of the turbine is done with conventional controls and it soon runs up to its 90,000 r.p.m. operating speed. It produces 30 kw. of power and the exhaust runs at very high temperatures but with extremely low emissions. When the batteries are in a sufficient state of charge to drive the vehicles, the turbine idles but automatically runs up to full speed dependant on demands of acceleration or load being demanded by the operation of the bus. Because there are no reciprocating parts, there is little vibration or noise from the unit and its maintenance costs should prove to be extremely low.
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