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Bus maker Alexander Dennis to fit GKN Gyrodrive flywheel hybrid systems to 250 buses; partners on international development

GKN Hybrid Power Gyrodrive technology
Gyrodrive. Click to enlarge.

Alexander Dennis Limited (ADL), Britain’s biggest bus and coach manufacturer, has chosen GKN Hybrid Power as a preferred partner and committed to the purchase of 250 of its Gyrodrive electric flywheel hybrid systems (earlier post). ADL will focus initially on the introduction of the low emission technology to bus fleets in London and Oxford but anticipates rapid deployment across the UK in the next few years. It will also be working closely with GKN to develop the technology for international markets.

Instead of a battery, the Gyrodrive system uses a magnetically loaded high-speed carbon-fiber flywheel to store the energy generated by a bus as it slows down to stop. It then utilizes the stored energy to power a GKN EVO electric motor which helps accelerate the bus back up to speed, generating significant fuel savings of up to around 25% at a considerably lower cost than battery-hybrid alternatives.

The electric flywheel technology is particularly suited to applications that demand high symmetric power transmission at continuous cyclic duty cycle. Used in this way, the electro-mechanical efficiency of this technology is very high compared to competing electric storage technologies, the company notes.

Although this flywheel kinetic energy recovery (KERS) technology offers higher specific energy than ultracapacitor technologies, compared to batteries, the energy capacity is much lower. In other words, the flywheel cannot be considered as a battery replacement from perspective of storing energy over long durations (such as overnight). Instead, the flywheel is a very efficient, short duration energy accumulator, that can capture and re-deploy large cumulative amounts of energy with little waste. This sort of operation is ideally suited to Kinetic Energy Recovery on a city bus, for example, where energy captured during braking only needs to be stored until the next pull-away from the bus stop.

ADL’s Euro6 Enviro400 bus—the UK’s best-selling double decker—fitted with the Gyrodrive system recently achieved Low Carbon Emission Bus Certification, which acknowledges a 30% reduction in greenhouse gas emissions and entitles operators to enhanced fuel rebates.

The Gyrodrive system is designed to last for the life of the bus eliminating the need for any battery changes and offering much lower whole-life costs than other hybrid alternatives, making it a viable proposition commercially.

The same technology helped Audi’s R18 e-tron win the Le Mans 24 Hours Endurance race in June, Audi’s third consecutive win with GKN’s technology.

Earlier this year transport operator Go-Ahead Group selected GKN to supply 500 systems for use on buses in cities across the UK following successful trials in London.

ADL is now well established as Britain’s leading provider of advanced hybrid systems with almost 800 of our low carbon buses operating across the country. This alliance with GKN introduces a new dynamic to the market place, courtesy of a lower cost solution that provides significant fuel and greenhouse gas reductions, coupled with reliability and durability. Add to this the incomparable aftermarket support that we can provide together and it represents a powerful proposition.

—Colin Robertson, CEO of Alexander Dennis

GKN Hybrid Power us further developing the Gyrodrive technology is being further developed for other mass transit markets including trams, construction and agricultural equipment. Earlier this year GKN announced the acquisition of Williams Hybrid Power from Williams Grand Prix Engineering Limited to form GKN Hybrid Power, which is focused on delivering complete hybrid solutions across multiple vehicle, power and industrial markets.



I have been waiting for a company to put this into a car.
Kers systems can even be used to give a boost to a lower horse power car. Smaller ICE motor with a cheap Kers boost really makes sense. If you are getting 30MPG from a small ice and this boost it 25% and adds some extra HP to your movement it make sense.


KERS favours vehicles whose drive cycle demands frequent stops. IMO for cars, the adoptiion of a driving style that includes coasting when the opportunity arises would probably yield better results.

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