Three important technologies – Electric Vehicles (EVs), solar, and smart micro-grids (all of which are electrical engineering technologies) – have come to the rescue of yet another climate change challenge, namely urban transportation. This time for the design of ultra light rail vehicles what is commonly referred to as ‘trams’, ‘street-cars’ or ‘trolley cars’.
The advancement of EV technologies has offered light weight (Li-Ion) battery storage and superior BLDC motor drives. The development of Micro-grids has offered three main advantages over large centralised grids – (a) more efficient local energy distribution that avoids transmission losses, (b) ability to disconnect (islanding capability) to minimise outages during storm or other calamities, and (c) smart or intelligent behaviour – ability to control and orchestrate multiple resources to meet the energy needs of the ‘tram’ network. India being a tropical country with abundant solar energy, it is now feasible to focus on ‘solar micro-grids’ where the resource is largely solar.
What is an Ultra Light Rail Transit or ULRT Tram?
Is the ‘Ultra Light Rail’/‘Tram’ the same as any of the following Mass Rapid Transit (MRT): Metropolitan Railways (Metros), ‘Subways’, ‘Light Rail’ transit or ‘Heavy Rail’? The answer is no. All the latter forms of public transport are far heavier. Heavier transport means higher inertia and momentum, and associated with it numerous disadvantages such as difficult braking, poor efficiency, and most importantly the grade separation issue – the need to segregate them from street traffic.
Rapid transit (heavy rail) lines and even the more recent Light Rail Transit (LRTs) are more segregated from street traffic than are tramways (particularly in congested urban areas). LRT is characterised by a combination of tram and rapid transit features. While its rolling stock is similar to a traditional tram, it operates at a higher capacity and speed and often with an exclusive right-of-way. Though the light rail vehicles were introduced in the 1970s as a technological outgrowth of trams, it appears to have amassed the disadvantages of trams along with that of the heavy rail lines. LRT is usually powered by overhead electrical wires, which are considered to be a nuisance in congested areas. At the same time, LRT needs to be segregated from street traffic like the heavy rail.
(Courtesy: Siemens)
On the other hand, the recently re-emerging trams (Ultra Light Rail Transit/ULRT) are truly a technological advancement to the older generation trams, and have preserved the ‘ultra-light’ nature of the carriage, (empty weight < 20 t), that is most essential if they are to run alongside street traffic in congested areas.
Ultra Light Trains – Tram’s New ‘Avatar’
The re-emergence of trams or ultra light trains in the 21st century can be attributed to two British companies – Parry People Movers Ltd. (PPM) located in the West Midlands, and the other is Warwick Manufacturing Group, Coventry. The German company – Siemens Transportation Systems, too, has become actively involved in the revival of trams with its ‘Combino Plus’ and ‘Ultra Low-Floor’ (ULF) tram platforms.
PPM’s Class 139 Trams
PPM manufactures lightweight trams that use Flywheel Energy Storage (FES) to store energy for traction, allowing electric systems to operate without overhead wires or third rails. These trams are fuelled by small gas, diesel or hydrogen engines.
PPMs utilise a rotating flywheel as a store of kinetic energy which is then used to power the vehicle. The PPM flywheel, made from steel laminates, is 1 metre in diameter and 500 kg in mass and rotates at a maximum speed of 2,500 rpm. It is mounted horizontally at the centre of the unit, beneath the seating area and is driven by an internal combustion engine or an electric motor. The flywheel is connected to the rail wheels via a hydrostatic variable transmission system. Unlike many other railcars that convert the flywheel energy into electricity before driving the wheels, in the case of PPMs, the wheels are directly driven by the flywheel.
The flywheel allows the direct capture of brake energy (when slowing down or descending gradients) and it’s reused for acceleration (called regenerative braking). When the vehicle brakes, the hydrostatic transmission feeds the energy back into the flywheel. Since the short-term power demand for acceleration is provided by the energy stored in the flywheel, there is no need for a large engine. A variety of small engine types can be used including LPG, diesel or electric traction.
On a route with stations a short distance apart it is theoretically possible to use the unit as a tram without any engine or overhead electrification at all. Instead, the flywheel could be re-energised at each station, storing enough power to carry it on to the next.
Despite the fact that Parry made only a single major breakthrough, namely the launch of the Class 139 Stourbridge trams in the UK market, he was a campaigner for cheaper-to-run, energy-efficient transport, and never gave up his battle for its recognition.
A couple of PPM’s Class 139 trams has been running on a short (1 km) ‘Stourbridge Junction to Stourbridge’ stretch, successfully since 2009. It is a ten minute interval shuttle, with 97 round trips every weekday. The Class 139s are powered by straightforward Ford 86hp 2.3-litre LPG-fuel engines (used in vans and trucks), have flywheels to capture the energy generated and then reuse it for acceleration and powering on-board systems.
Currently, PPM is focussing on a hybrid transmission comprising compressed air, flywheels and batteries that they have termed as ‘Tribrid’. They have amalgamated two hybrids – PPM’s Class 139 hybrid primary driveline and Clayton Equipment’s hybrid battery electric locomotives.
They claim that the ‘Tribrid’ tram will deliver the benefits of electrification by means of Compressed Air Energy Storage or CAES. The power from the traction batteries is supplemented by additional power from the PPM flywheel energy store. While the compressed air tanks are located centrally under the carriage floor, the rest of the components are accommodated within the traction car’s bogies.
The prime mover air motor of the Tribrid vehicle drives a flywheel that accumulates kinetic energy that is linked to an electricity generator providing traction current at a steady rate or in surges to accelerate the vehicle. When cruising at a steady speed the current maintains the momentum of the train and at the same time feeds energy to a pack of high charge batteries. These can be accommodated with space available in the carriage body, but more conveniently in a second bogie, which in most applications will not need to carry traction equipment and has space available. The Tribrid arrangement improves energy efficiency in two different ways:
At times when the vehicle is descending gradients and slowing down approaching a station it is not necessary to apply the brakes as the energy flow to the wheel’s reverses, returning charge to the batteries. When hydrostatic secondary drivelines are used (as in the Class 139s) this accelerates the flywheel, recovering kinetic energy;
Because the prime mover motor is far smaller than in a non-hybrid vehicle its energy consumption is lower, and needing less space is easier to fit in a bogie.
What we admire about Parry’s vision to help the environment, is that his design does not charge batteries from the AC mains supply generated from fossil fuels. Instead he uses CAES that can be stored in bulk quite cheaply and which can be piped across to the tram car very quickly at any time at any trackside store located at a tram stop.
At each of these trackside stores, PV solar energy can be used to drive air compressors till its storage tanks again become full and the same can be further used by the next tram taking a halt at the store.
Coventry Very Light Rail (CVLR) Tram System
The Coventry Very Light Rail (CVLR) tram system is also an ULRT and an environment-friendly and economic public transport system that will be the first of its kind to operate in the United Kingdom, and also the first tram network to operate in Coventry after the Second World War. The CVLR system includes lightweight, self-propelled vehicles. It uses batteries to avoid expensive overhead line equipment along much of the route. They have designed a new, thinner track system that is easier to install and repair. The vehicle is standard UK gauge and hence is compatible with their other rail networks. It is claimed that the CVLR tram system is designed to be substantially cheaper than conventional tramways and light railways. Work is headed by Warwick Manufacturing Group (WMG) and Transport Design International (TDI) and the system is planned to be operational by 2024. They eventually plan to operate these vehicles autonomously (without a driver).
The unladen weight of a CVLR tram vehicle is only 11 metric tonnes. Each vehicle accommodates 56 passengers, of which 20 will be seated. They plan to operate the vehicles at a frequency of every 5 minutes and later – when autonomous – every 3 minutes. The vehicles are equipped with batteries that would be charged using rapid charging systems. Thus, the need for overhead line equipment installation throughout the route is dispensed with, resulting in reduced installation costs.
The major feature of the CVLR system is the track which is prefabricated. It is relatively lightweight and shallower than a traditional tramway track. This means less excavation and that the tracks can be laid over existing utilities, thus avoiding the need for these to be relocated. The tracks are lodged in slabs mounted in the tarmac layer of the road. The 250mm thick slabs are built off-site and transported to the project site in sections to be clipped together at the location.
For ease of maintenance, the tracks are held together by a series of clips, which allow the track to be dismantled easily and quickly and later reused at other locations. The slabs can be removed from the sections within 90 minutes to allow repairs to utilities. A high-strength foam core with recycled plastic on top is being considered for the slab material. All these factors make the installation of tracks quicker and cheaper. The average cost per kilometre for the system is expected to be £10m, which is less than the £35m-£60m per kilometre for conventional systems.
To address air quality, the CVLR vehicle is battery powered, which means it is zero emission at the point of use. Additionally, it uses a regenerative braking system in collaboration with AP Racing, a Coventry-based company.
One of the key goals of the CVLR project has been to create a vehicle that can run on existing roads, minimising the need for demolition, land acquisition, change in road layouts, etc. The vehicle was designed with two key features, namely, an innovative turning mechanism, known as its ‘bogey’ and its on-board battery.
The University of Warwick created a new kind of ‘bogey’ that allows the CVLR vehicle to turn on 15 metre radius curves, which means that in most places, the track could be laid in the existing road.
Instead of overhead power, the CVLR vehicle will take advantage of ‘opportunity charging’. The vehicle will make a short stop at key sites along routes to charge a small amount using an overhead electric charger, which would also extend its battery life. The battery is estimated to offer a range of 70 km on a single charge.
The researchers from the University of Warwick are also working on integrating autonomous vehicle operation technology into the CVLR. They believe that introducing autonomy in a rail based system such as CVLR will be simpler than introducing it in cars, as it gets restricted to the rails and the environment can be mapped.
(Courtesy: Siemens)
Siemens
Siemens has been addressing the consequences of urbanisation and demographic change mega-trends by focusing on public transportation. With the growing need for environmental protection, increasing mobility and growing demand for safety, security, healthcare and elderly care, Siemens Transportation Systems has been introducing new technologies to keep rail-based systems competitive. Siemens has successfully completed two tram projects at Almada (Portugal) and Budapest.
From its learnings, Siemens has developed its new tram platforms such as the Combino Plus and the Ultra Low-Floor (ULF), which they claim to be the lowest floor light rail tram in the world. These latest models are used in Budapest and Vienna respectively. Vienna’s tram network was considered to be the biggest with over 850 tramcars in 2005.
I hesitate in calling the Siemens’ Combino or the Ultra Low-Floor tram platforms as ultra-light since they possess the characteristics of an LRT – such as an exclusive right-of-way and grade separation.
Integration with Bicycles and Wheelchair-Accessibility
Ultra low floor is a desirable feature for ULRT trams. It is particularly helpful for the elderly (wheelchair-accessibility) and for bicycles. In order to promote bicycles, many light rail lines and fleets have favourable policies on bicycles. In the rear section of the tram cars, commuters are allowed to carry their bicycles on board in many fleets. Though some restrict bicycles in trams during peak hours, I believe the scenario will change further as environmental and climate change factors gain further importance.
Designing At-Grade Ultra Light Rail Transit
The planning, design and construction of an Ultra Light Rail Transit (ULRT) line requires that a wide range of complex issues are resolved. The grade separation issue is particularly critical, as it directly affects the operational, economic, and political viability of an ULRT line. Traffic analysis and evaluation techniques can be used effectively to make early decisions on vertical and horizontal ULRT alignments, to both guide ULRT planning policy and focus subsequent ULRT design efforts. Traffic issues play a critical part in making these decisions, and transit planners and traffic engineers need to know the potential magnitude of LRT impacts on traffic circulation, parking, and the degree of ULRT priority or grade separation for which to plan.
The key characteristic of an ULRT (that differentiates it from an LRT) is its ability to operate at grade, interfacing with traffic and pedestrians. This can reduce construction costs significantly thereby justifying rail development in corridors where costly construction may not be warranted. Operating at grade also improves access to the trip generators. However, it could also reduce transit reliability, reduce operating speed, and may interfere with traffic movements. The key elements in a successful at-grade ULRT design include effective intersection control and traffic interface design.
Due to limited experience in this field, it has been observed that at-grade LRT (not ULRT) design projects have been foreclosed at the planning stages even before potential problem resolution can occur when beset with misconceptions. The higher weight and higher speed of LRT make it difficult to design at-grade.
However, in the case of ULRT, due to desirable features such as smaller turning radius, lighter weight, and lower speeds, I believe that designing an at-grade ULRT system would be much simpler and easier.
Central Government’s LRT Plans and Concluding Remarks
Due to the rising concern over the viability of the cost of metro rail projects, especially in smaller cities of India, the Central Government is planning to promote the LRT system called Metrolite as an alternative mass rapid transport system in urban areas. They too believe that the LRT uses rolling stock similar to a tramway but can operate at a higher capacity. However, as we have discussed earlier, the main issue to be addressed is an exclusive right-of-way which is impossible in dense urban centres. A dedicated rapid rail corridor with tracks on the surface instead of elevated or underground stretches is impossible in the cities. The Delhi and Nasik Tender’s of the LRT have already been floated. The government is planning to introduce LRT for the remaining 3 corridors of the phase 4 project of the Delhi Metro, and for two corridors of Nasik Metro.
We hope that the Indian Government will consider the implementation of autonomous (driverless) battery driven ultra-light ULRT for Tier 2 and Tier 3 cities. In India, we can pick up the positive features from each of the trams covered above. In Parry’s tribrid, they planned to use PV solar energy to drive the air compressors at each of the trackside stores. In the Indian ULRT, we can consider a combination of electric motor driven flywheel (like Parry’s) and battery like Coventry’s CVLR. The batteries could be partly re-charged (during the day) using PV panels placed on the roof of the tram, while the reset of the energy could be tapped from the trackside stores during the brief halt. More importantly, during the halt, energy can be tapped from the trackside stores to increase the kinetic energy (speed) of the flywheel. The trackside stores are also recharged using stationary PV solar panels.
Vithal Kamat has a Doctorate in Artificial Intelligence from the University of New Brunswick, Canada as a Commonwealth Scholar in 1996. He completed Masters in Control and Instrumentation from IIT Bombay. His current role – reviving a sick industry as a Managing Director of Baroda Electric Meters Ltd. Current interest lies in exploring ways to replace the Human centric Judiciary with an AI Judiciary, to replace the 24-hour clock with Ghati clock, and to replace ICE vehicles with solar vehicles.
