Hybrid Transport System

NECESSITY

The propulsion systems of the terrestrial transportation means, progressed in parallel a long period of time (fig.1). The trains and the trucks were one by one driven by the steam machines and internal combustion engines. The locomotives took advance, starting using the hybrid systems (Diesel Engine combined with electric drive or Diesel Engine combined with hydraulic drive). This difference was amplified when the propulsion system of the trains becomes electric to increase its efficiency. It may say that the rail transport is with two steps in advance comparing with the actual road interurban transport. Normally if the parallel trend continues, also the trucks and buses will be in the nearest future hybrid or electric.

STATE OF THE ART

It is known that usually electric vehicles named trolleybuses (fig. 2) can circulate on ways shared by general urban traffic, but that they will have to follow imperatively the trajectory imposed by their source of energy supply, a feeder usually named catenary (dual overhead line) system. This “in motion charging system” limits the vehicle speed at 70 Km/h and consequently the trolleybus cannot be used in highways. It is known also a solution which can be named “hybrid” trolleybus that uses an APU (auxiliary power unit) to act the vehicle from the garage or in some portion of the way. In this case, the main problem becomes to put in connection the trolleybus with the overhead lines. This operation is often very delicate and must be made usually with the vehicle stopped. Another disadvantage is the limited transverse freedom allowed by the trolley, which is subject to disjunction from the line, if the trolleybus, in order to avoid encumbrances, deviates transversely too much with respect to the electrical line.

A new solution was proposed by Siemens , the trolley assist technology (fig. 3), seems to solve the main problems of trolleybus. A truck (or bus) hybrid powertrain can have a supplementary electrical source through two lines in the air thus becoming completely electrically powered on electrified road sections.

“Fuel savings made possible by electrification are huge, and this project is a foundation stone for fossil-free road transport. “

                                                                                    —Henrik Henriksson, Executive Vice President and head of Scania’s sales and marketing

Siemens’ e-Highway concept for the electrification of road-freight traffic has three core components:

• Diesel-electric hybrid technology
• Power supply via catenary lines and regenerative braking
• Intelligently controllable pantograph for energy transmission

In normal operation, e-Highway HGVs draw electric energy from a catenary system using an adaptive pantograph to establish contact with the overhead wire. Wherever there is no overhead line, the e-Highway HGVs automatically switch over to their diesel-hybrid drive system. This means that they can be used just as flexibly and universally as conventional HGVs. The catenary systems are designed as two-pole systems for two-way electricity transmission (infeed and outfeed); unlike railway technology, the current return circuit cannot flow via the road. The overhead wire is fed from a container substation.

Even Siemens solution has these big advantages it has also a number of drawbacks:

-The double overhead line is very complicate and expensive;

-The adaptive pantograph is different than existing pantograph and unfortunately is expensive and very complex as construction;

-A relatively small lateral displacement of the truck generates the interruption of the contact with the double overhead line;

-Due to the pantograph system, the distance between the truck and the double overhead line is relatively small and this limits the height of the vehicles used in this e-Highway to a relatively small value.

-If the highway is electrified for trucks and bus, why is not also electrified for passenger cars?

Another method of energy transfer is that of the dynamic inductive charging. This has the disadvantage of producing strong electromagnetic fields that are incompatible with the passengers and therefore require costly protection solutions. The changing infrastructure is very expensive and then these routes do not exceed 10 km. The cost of energy inductive transducer per car is about $ 4,000. In addition, the vehicle traction batteries can not be removed. This system requires no uneven roads and the system may not apply to countries with temperate or cold climate (because of snow deposited on the road surface even in a thin layer).

Other solutions were proposed like in the French patent FR 2277694, which describes an electric urban bus supplied by a single overhead electric line where the two polarities are intercalated and separated by isolated portions. The vehicle uses two pantographs distanced with the length existing between two neighbour-isolated portions. Even the principle of this concept is highly innovative the proposed practical solution supposes the using of discontinued electric line supplied with electricity in some points aligned with the isolated portions, each point being supported by a pillar. Consequently the distance between the electric supplied pillars is very small being equal with the distance between two neighbour-isolated portions.

Such pillar density is not acceptable in term of network costs and is a reason for which this solution was not putted in practice.

INNOVATIVE ASPECTS

The inconveniences and disadvantages of the previous described systems are overcome by the transportation system which constitutes the object of the present concept. The hybrid transportation system described herein mainly intended for urban and transit transportation, is electrically supplied in motion in some portions, named electric charging station and therefore non-polluting and noiseless. According to this new concept, the vehicles are operated by electric or hydraulic reversible machines fed by storage device, which are recharged (recharged and not replaced) at the stops or in motion. Recharge is obtained by means of connecting means which connect the vehicle to a distribution electrical network having connecting points at most of the stop stations established (in the case of the urban buses), on the city roads or on the highways (for other vehicles). This concept represents an “in motion plug-in system” because the vehicle can be charged when is in moving. With such a system, the following cumulative advantages are obtained: high exploitation of system resources; range adequate to the class of service considered with a safety margin exceeding traffic incidental events; complete path freedom among two consecutive electric charging stations; optimization in the utilization of storage device; elimination of the electric power line in the cross passages and elimination of the problems caused by the intersected electrical line such as installation, isolation, maintenance; unlimited transverse freedom; a small price of the distribution electrical network; low size and cost APU with Hybrid Opposed Piston Engine; and warranty of continued service, even in the case of an electrical power lack at the stations, at least for a duration depending on the vehicle range.

DESCRIPTION OF THE SOLUTION

The hybrid transportation system described above considers the utilization of free routing vehicles, but it is clear that the invention may be applied also to rail vehicles, such as trolley-cars, underground vehicles, suburban railways, and, by suitable modifications, also to transportation systems using boats having predetermined docking points as well as to private internal transportation systems employing electrical trucks and elevators.

The system can be used for urban or interurban buses, trucks or other vehicle types without discrimination. It is a “bi” or “tri” mode hybrid system which uses mainly a clean external electric source of power to charge an accumulating device coupled with a regenerative brake transmission. The vehicles are charged in motion by an interrupted or continue grid system. A schematic description of the system is made in the Figure 4.

The Hybrid Opposed Piston Engine (HOPE) and its associated Auxiliary Power Unit (APU) is used as a back-up source of power because has a reduced weight, and can use different fuels (including hydrogen) without adding an auxiliary supercharger (which is expensive and costly). The effective efficiency of Hybrid Opposed Piston Engine with hydrogen is between 50 and 60% being at least equal with the fuel cell efficiency but with a fraction of the cost.

In another arrangement the traction batteries can be completely removed. That means a low cost of the hybrid vehicle, which becomes attractive for clients.   

The hybrid transport system, conformable with this concept has two main components: the infrastructure and the hybrid vehicles. For heavy vehicles the infrastructure supplies with energy a street network built as a single overhead line containing the both polarities. For passenger cars and medium size vehicle is used a simple and safe system with two electric lines.

The essential differences with the patent FR 2277694 are:

-The two electric cable representing the two polarities are situated in parallel and have continues structure permitting the industrialization of the process.

-The pillars which support the single overhead line are distanced so that to sustain the structure. The interval becomes bigger and the network is simplified. Also only the pillars situated at the each end contain cables to supply the line. The rest are made only for support of the network. All these reduce costs and make the possibility to achieve in practice this system.

-Using this logics can be imagined another variant for the regions or areas having bad weather and that is not possible in the case of the French patent FR 2277694. The single line 286 conformable with the new concept (Fig. 5) uses, at the interior, two parallel cables 325 and 326, which are isolated, each of them representing a polarity. The cable 325 is electrically connected with a metallic plate 290 located in the inferior side using few bolts (or screws) 327. The metallic plate 290 represents one of the polarities. Similarly, the cable 326 is electrically connected with another metallic plate 329 representing the second polarity. Between each metallic plate 290 and 329 is intercalated an isolating plate 328. The distance between two isolating plates is equal with the distance between the two pantographs of the vehicles. The cables 325 and 326 are closed between the metallic plates 290, 329 and the isolating plates 328 located to the inferior side, and a number of support plates 289 located to the superior side. The support plates 289 are made by isolating material. 

The hybrid vehicle (Fig. 6), in this case a bus, conformable to the invention, present as mobile charging device two articulated arms (pantographs) 310 each of them supplying the propulsion system with one polarity. Each arm 310 has a transversal plate 312 which enter in contact with the overhead line 286. The distance between the two articulated arms 310 is equal with the distance between two isolating plates of the overhead line. During the motion of the vehicle each articulated arm 310 changes periodically the polarity. A device existing in interior of the vehicle achieves the current regulation to obtain same polarity at the supplying contacts of the internal electrical circuit.

The mobile charging device (the articulated arms) 310 and the overhead line 286 form together the temporary mobile connection (fig. 4). During the motion of the vehicle in the area of the electric charging station (docking station), the electric energy is transferred trough the hybrid vehicle. When the hybrid vehicle is operated out of the area of the electric charging stations, the mobile charging device 310  is lowered.

When the hybrid vehicle is a truck (Fig. 7), one articulated arm can be located on the tractor and the second on the top of trailer. All hybrid vehicles using this transport system can have same standardized distance between the articulated arms. On the other hand the articulated arms can be replaced with other devices having same function (as multi arm pantographs, etc.).

The hybrid vehicle can be built as hybrid electric vehicle or as hybrid electro-hydraulic vehicle  the last variant being more adapted for city drive. 

There is also a charging system proposed for passenger cars and medium size vehicles which can create the possibility to fully electrify an entire highway.

In a first variant (fig. 8)  the system uses as charging device two pivoting arms 181 and 190, one mounted laterally (181) for one of the phase and the second mounted centrally (190) for the other phase. The arms can be pivoted to enter in contact with the electric supplying lines 195 and 196, one line being mounted as a way layer (196) and the other as a lateral strip (195).  If the highway is with three lances the first lance is used by hybrid tracks and buses, the second is for overtaking and the third for the hybrid passenger cars and medium hybrid vehicles.

A second variant for passenger cars is described in the figure 9. In this case the both lines (polarities) 257 and 258 are contained in a single support which is so positioned to be easy used by all light vehicles. 

If the highway is with three lances, the first lance is used by hybrid tracks and buses, the second is for overtaking and the third for the hybrid passenger cars and medium hybrid vehicles.

In summary, existing or newly constructed roadways may be readily and relatively inexpensively electrified in accordance with the present proposal. The entire electrification system for heavy vehicles, is applied as a single inexpensive overhead line supported with few pillars, interrupted or not by the roadway exits, being charged for the relatively small stations formed at approximately 1 kilometre centres, necessary for the junction boxes each of which supplying with electrical energy to corresponding 1 kilometre electrically isolated segments of the line. The single overhead line contents the both polarities of the electric current and is protected from bad weather. The roadway can readily be utilized by both electrically or electro-hydraulically operated vehicles according to the present concept, and by conventional nonelectric motor vehicles. The vehicles may be operated on the electrified highway, utilizing the electric current (DC or AC) picked up from the roadway to provide the energy for driving the vehicle and simultaneously charge the battery pack. There is no power interruption when the electric charging process is stopped, as the power is automatically taken from the accumulating device until such time as contact with the roadway energizing is re-established. Same centres supply with energy the system created for passenger cars and medium weight vehicles.

ADVANTAGES OF THE INVENTION

A) As General Transport System:

This concept creates the possibility to achieve at present a mass-production high efficiency zero-pollution transport system for goods and passengers. This transport system can be used both in the city and in the highways. The charging system is not influenced by the bad weather and can work at all latitudes. It is a system which does not increase the electromagnetic pollution (as in the case of the inductive charging) in the vehicle interior or in the external area.

The hybrid transport system has a number of major advantages: compatibility with current technologies, effortlessly adaptable infrastructure, reduced energy consumption, zero emission in normal conditions, and lower operating and life cycle costs.

1. Compatibility with current technologies. All the technologies used to develop this new system are well known and are already proved separately in different applications. Some hybrid vehicles are already in use. With a few small modifications these propulsion systems can be transformed to perform the hybrid transport system new requirements.

2. Effortlessly adaptable infrastructure. The current infrastructure will be easily modified to be compatible with this concept. After the conversion, the infrastructure remains compatible with the usually unmodified vehicles.

3. Reduced energy consumption. The total propulsion efficiency of the hybrid vehicle in normal conditions is equal with the multiplication of few factors being similar with that obtained by the trolleybus or by the tram. This value is superior to a fuel cell’s total efficiency. The regenerative braking operates with a total efficiency up to 70%.

4. Zero emission. In normal working conditions is a zero-emission vehicle. "Greenhouse" gas emissions, believed to contribute to global warming, are completed eliminated. Consequently the estimated reduction in pollutant emissions (CO2 in special) would be 180 kg/day in case of the urban buses.

5. Lower operating and life cycle costs. This hybrid system results in lower operating costs due to reduced stress and maintenance on mechanical components.

Other advantages of this system are the very low level of NVH, even when is used the Auxiliary Power Unit which reduces also the environmental noises pollution and the easiness to recycle the component parts at the end of the lifetime.

B) As a solution proposed to replace the trolleybus:

1. The intermittent charging system can be safely coupled with the supplying system at high speed (even at 100 Km/h or more) and the hybrid bus, conformable with this new concept, will be no more stopped to make this operation. Consequently this vehicle will not block the traffic behind it.

2. The speed limit can increase without problem because the charging of the accumulating device can be made in motion at high vehicle speed much (more than 70 Km/h). Consequently the new hybrid bus can be used as suburban and interurban means of transport.

3. Using a single overhead line without cross passages the electric supplying network is simplified at maximum and the cost will be reduced.

4. The new proposed concept permits a total flexibility and will be not imposed trajectories.

C) As an alternative solution at the actual propulsion system of the interurban (transcontinental) heavy trucks:

1.This concept creates a real world alternative to the actual propulsion system of the heavy vehicles. It is not need to make so many researches to develop such a system because all the components are already used separately in some applications.

2.The total efficiency is improved and consequently the cost reported to km will be diminished.

3. It maintains the same flexibility of the actual transport system based on the diesel trucks.

Bibliography:

1. ***, www.tbus.org.uk

2. Clean Urban Transport for Europe final report, Fuel Cell CITARO, 2006