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A Spanish company has developed a new type of urban bus system based on a rapid charge hybrid (RCH) system which allows urban transit buses to substitute electricity for diesel in a practical manner using existing technologies with minimal changes. The company is looking for industrial partners interested in licensing or further development.
Recent advances in battery technology are
enabling novel solutions to existing problems. A rapid charge hybrid (RCH) system which allows urban
transit buses to substitute electricity for diesel in a practical manner using existing technologies
with minimal changes to existing fleets has been developed by the company.
Lithium titanate
(Li4Ti5O12 or LTO) batteries have two properties that enable a new type of urban bus system: rapid
charging and long cycle life. By placing a rapid charger at both ends of a bus route, LTO equipped
hybrid buses can run most of the time (70-90%) in electric-only mode. A rapid charger fills the
batteries each time a driver reaches the end of route. Existing hybrid diesel-electric buses with
backup diesel generators are used to prevent stranding. This Rapid Charge Hybrid (RCH) approach
requires virtually no changes to existing hybrid bus designs or fleet behavior, and requires little
additional
infrastructure. If the electricity comes from renewable sources such as wind and solar,
then RCH is a sustainable transit system.
The proposed RCH system is simple. High power opportunity
charging stations (~250kW) are added to the end of a bus route, and serial diesel-electric hybrid
buses with LTO batteries are deployed. When the driver stops for his “layover” time of 5 or 10
minutes at the end of the route, the batteries are rapidly charged. With the extraordinarily rapid
charging ability of these batteries, it is possible to pump enough charge into the batteries in this
time to run a route of 10 - 15km in the “electric-only” mode of a serial hybrid bus. Secondly, the
long cycle life of LTO batteries permits a practical battery lifetime.
This system uses a normal
serial hybrid bus with LTO batteries substituted for the usual traction batteries. This means that
if the bus runs out of battery power, the hybrid diesel generator can take over to run the bus
indefinitely on diesel alone. These non-battery exceptions might occur, for example, if the driver
is running late and doesn't have time to charge, or if it is a hot day and the air conditioner
is on. If the system is sized so that normally the bus can run 100% in all-electric mode, then
including exceptions, the bus should easily run 70 – 90% in all-electric mode overall.
Opportunity
charging is practical in urban bus systems because of their fixed routes. Other systems with fixed
routes such as refuse trucks should also be able to apply this system.
The company is looking for
industrial partners interested in licensing or further development.
Innovative Aspects:
- Converts
a 100% diesel hybrid bus to a 70-90% electric bus, with all of the
attendant, well-documented
benefits of electrification.
- Infrastructure is tiny compared to that of a trolleybus or tram
system: just two small charging stations at each end of the route. Only a relatively small amount of
construction or planning is needed, with no overhead or under-vehicle wires required along the
route.
- Uses existing technologies with very little engineering cost or risk. Suitable hybrid
buses already exist, as well as the required high power chargers. Large LTO battery cells with the
needed specifications are commercially available now.
- Buses use current diesel fueling
infrastructure. The operator can run the same routes and schedules as current diesel buses. Charging
is done at the route ends, where ordinarily there are no passengers. Passengers will never have to
wait while the bus is being charged at intermediate stops. Additionally, if a charging stop is
missed, the bus can continue indefinitely using the diesel generator.
- Integrates easily with
existing diesel bus systems, especially if the system already uses hybrids. The operator can
gradually add more RCH buses over time, phasing out pure diesel buses or non-chargeable hybrids as
they age.
- Additional power for accessories such as air conditioning on hot days is always
available from the backup diesel generator. The batteries and charging system can therefore be sized
for normal days.
- Flexible trade-offs between electricity and diesel can run the full spectrum. An
operator can decide to weight his percentage usage of electricity anywhere from 0 – 100% by changing
how much layover (charge) time is built into the bus schedule.
- Intelligent charging can be
coordinated with the electric supplier to avoid charging when there is a high electrical demand, and
diesel power can be substituted during these peak times.
Stage of Development
Available for demonstration
Exploitation of RTD Results
None
IPR
Patent(s) applied for but not yet granted
Company
Details
Collaboration Type
- Joint further development
- License Agreement
1. The type of partner sought: The company is looking for industrial partners interested in licensing or further development.
2. The specific area of activity of the partner: The partner should have experience in the transportation and/or renewable energy sector.
3. The tasks to be performed by the partner sought: Exploitation of the technology all over Europe and development and adoption of further applications.
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