XVI. On-Grid and Grid-Optional Transport
(originally published July 2, 2008)
Currently, vehicle-makers, researchers, investors and green technology analysts are involved in a high-stakes game of developing and investing in various battery chemistries and designs which may yield the result of more energy dense, longer-lasting, and less toxic batteries or ultracapacitors. It’s a good thing that more and more social and financial resources are pouring into electric transport and energy storage solutions. Still others are investing in and legislating in favor of solutions that have a more limited future, the biofuel and hydrogen fuel cell options, which unfortunately still have public and political support out of proportion with their short and medium term ability to drive a sustainable transport system. As other analysts and I have already highlighted, these liquid fuel solutions are highly inefficient in converting renewable energy into a fuel. They require vastly more natural resources and man-made instruments to capture an equivalent amount of usable renewable energy than does a electric generation/electric storage/electric drive solution.
But, in actuality, we don’t HAVE TO have better batteries to build the infrastructure for a livable, sustainable society. Sure it’s going to be nice but we should spread out our electricity-driven transport investments and development efforts. Before transport planners and consumers gave themselves over completely to fossil-fueled transport, we used to build electrified rights of way for trains and trolleybuses, which now look all the more attractive in an era of rising petroleum costs. Using electrical energy from the grid to power moving vehicles is an established technology that has received too little notice in our efforts to exactly reproduce the conveniences of the now closing fossil fuel era.
Thus, while better batteries are going to continue to be developed, on-grid and grid-optional vehicles will be a key component of a petroleum-free, carbon-neutral transport system. Grid-powered vehicles are already a mature technology so no breakthroughs are required. Thus, if we are serious about getting off petroleum and cutting our carbon emissions, developing a system of transport attached to a grid increasingly fueled by renewable energy sources can function as a “parachute” until more compact, durable and cheaper systems of mobile electrical energy storage can be developed.
On-Grid Transport and Renewable Energy
Transport of people and goods is now precariously dependent upon the output from oil fields and to a lesser extent natural gas deposits, which contribute to climate change. Building out our existing transport infrastructure with tested and easily modified grid technologies, allows us to use the limitless energy of renewable energy sources to generate electricity and drive land-based transport starting today and extending into the indeterminate future. While there are drawbacks to tying transport to the grid, these disadvantages are dwarfed by the mounting problems and expense associated with oil-based transport fuels.
In addition, predicating our transport future solely on the development of mobile energy storage (batteries/ultracapacitors) is putting all our eggs in one, albeit a promising, basket. The batteries are here, sort of, but we have not yet mass-produced battery electric vehicles in quantities that we will require to address our transport needs. There is no question, on the other hand, that we have the technical capacity to build and use on-grid vehicles to address many of our transport needs with no breakthroughs and no exotic materials. On-grid vehicles are already doing much of the heavy lifting in the area of transport in many industrialized countries. Why for the sake of embracing the “latest” or the “new” should we turn our backs on success?
The more developed and economical battery or ultracapacitor technologies become, the less we would need to depend on on-grid vehicles. On the other hand, I don’t believe we are in a position right now to only choose one “perfect” seeming future solution to the massive climate and energy challenge facing us. The challenge is too great and there are multiple excellent alternatives that will enable us to move beyond fossil fuels.
Already, zero emission vehicle and energy systems are here and functioning, often without much fanfare. The trolleybuses and light rail system of San Francisco’s Muni use hydroelectric power to power them. Calgary’s C-train system (pictured above) buys wind-generated electricity to power its light rail cars. Other electric train systems may not draw power from such clean sources, but it is only a matter, then of building renewable generators and energy storage systems to power these systems as well.
The publicity that battery developed and battery-dependent vehicles have generated relative to on-grid vehicles has a lot to do with the fact that we live in a society and economy that has been moved in the last 60 years towards individual and familial consumption and away from public infrastructure investment. In absolute terms, battery-based solutions deserve substantially more media attention than they get as, for example, the New York Times, the US “newspaper of record”, has been functioning essentially as a public relations arm for automakers marketing hydrogen vehicles. In the consumer market, powerful interests supporting biofuels and hydrogen fuel cells have overshadowed battery electric and plug-in hybrid electric vehicles (PHEVs/EREVs) in the media beauty contest to date. Still, in the world of electric transport, autonomous battery vehicles are the way that people prefer to imagine the future, as a battery electric vehicle, perhaps with quick-charge capability, will mimic what a fossil fueled vehicle would do.
If we rank the amount of media attention that the various electric transport alternatives receive, we put battery electric and PHEVs/EREVs first, then a distant second are new battery electric utility vehicles like trucks and, in last place, are electrified trains and trolleybuses, which, I suppose for the novelty-hungry press are considered “old hat”. This post, I hope will be one attempt to remedy this balance.
One element that reduces publicity for the on-grid alternative is that there are relatively few actual buyers for a massive transport infrastructure in even the best circumstances. Only governments or large private companies will invest in an electrified right of way for obvious monetary reasons as well as possess the legal right to build over or transform a route/road/railway of any length. There are also no giant companies that are yet significantly invested in building the electrical infrastructure, at least enough to suggest to the general public, governments or corporate buyers that this is an important solution for our energy and transport challenges.
While the existing grid-tied alternatives have not been fully brought into public consciousness, a fan-base exists for the sole new monorail-based technology called Personal Rapid Transit or PRT. Because of PRT’s newness and some other potential benefits, there are occasional articles that discuss this technology that will be installed at London’s Heathrow Airport to transport travelers to parking from Terminal 5.
The electrification of railways has for a century been the sign of the maturity of a rail route or railway system; the highest traffic routes in the world all tend to be electrified. If given the budget, most designers of rail systems would choose electrification over diesel. The electrification of a rail line costs more initially than simply building a non-electrified line but electric locomotives or “multiple unit” electric motorized trains (with motors in rail cars distributed throughout the train like many commuter trains and subways) are much longer lasting and energy efficient than train propulsion units that rely on internal combustion. Electric motors are simply more durable than internal combustion engines, which must endure millions of internal explosions throughout their lifespan. Electrification also allows for railways to use regenerative braking by returning electrical energy to the grid while braking; one train going down a hill can help power another train going up a hill. Electric locomotives are quieter, can be much more powerful, and, of course, do not emit any pollutants at the point of use.
Beyond the world of strictly electric locomotives there has been an interesting convergence of internal combustion engines and electric motors, that predated the recent convergence of these two types of traction in automobiles. Most fossil fueled locomotives are “diesel electric”, using a diesel generator to make electricity that drives the electric traction motors that turn the wheels. Some locomotives are “dual-mode” allowing the train to operate on either an electrified track or a nonelectrified track. Diesel electrics are the equivalent of a “serial hybrid vehicle,” while less common dual-mode locomotives are the equivalent of plug-in hybrids, using either a liquid energy carrier or electricity for locomotion.
There are two predominant systems for electrifying a railway: overhead wires and a third rail. Overhead wires are usually used for long-distance trains and for higher power applications while commuter and urban rail systems sometimes use the third rail. Other than higher voltages/power, overhead wires have the advantage of putting some distance between the electrical circuits and ground-based challenges including flooding or human interference. Third-rail systems are more compact and avoid the visual effect of overhead wires and towers over the railway. In the future, it may be possible to also use track-embedded linear induction motors that can propel railcars through the use of magnetic fields. An advantage of linear induction motors is that they would not pose the same electrocution danger as a third rail system, as electrical contacts are not exposed.
High speed rail, where trains travel in excess of 120 miles per hour (200 km/h) and as high as 200 miles/hour (320 km/h), can compete in terms of convenience and speed with airplane trips of up to 400 miles when all legs of a journey are considered. Europe and Japan now have fairly extensive high speed rail networks and there is now a proposal in California to build a high speed line from San Diego to San Francisco and Sacramento that at least theoretically could reach a maximum speed of 220 mph. High speed rail requires the building of special rail routes with very slight turns, low grades, smooth railbeds with welded rails. The fastest scheduled rail segment (of the French TGV) averages 173 mph (279 km/h) while the railed speed record also belongs to a specially prepared TGV that achieved 357 mph (574.8 km/h) in 2007 on an ordinary high speed route in France.
In America, where most areas are starting from a deficit of passenger rail options, the cachet of high speed rail projects may distract from building a functioning (electric) regional and commuter rail system where appropriate. With a wider dispersion of population such as in the West or between major business centers like New York and Chicago, high speed rail projects will be a more feasible and practical option. One could imagine, for instance a high speed line that ran from New York to Chicago with stops in Pittsburgh and Cleveland. On the other hand such a route would benefit from coordinated regional lines from surrounding cities, as well as a local train system. Because of the low friction of rails, ordinary express trains can maintain speeds of well over 100 mph on well maintained tracks which are fairly straight.
A systemic approach to rail is preferable to a sole focus on single marquee projects that advertise an intention but may overshadow equally useful regional and local rail projects. California’s High Speed Rail initiative is a good start but it is only the starting point for improving rail infrastructure in the West.
The electrification of trains does not in itself solve the multiple problems associated with transferring more people-moving and freight tasks from the roads onto rails. A railway can typically carry more freight or passengers per unit area than a road system yet a bi-directional dual track corridor is less flexible than a multilane highway, which can carry both passenger and freight vehicles. In the United States, railways are oriented mostly towards freight while in Europe, passenger rail predominates to the detriment of freight. As anyone who has traveled on Amtrak outside the Northeast knows, heavy freight and passenger traffic do not mix well on rails, so a stable solution would be to have separate passenger and freight tracks in most situations. High speed rail adds an additional set of tracks on routes where this is feasible. A high volume of rail traffic can also interfere with road traffic and interfere with surrounding communities unless grade separated and with pedestrian overpasses or underpasses.
Building more sets of rails, reviving existing rails, grade-separating road and rail and then electrifying those rails are all projects that require large public and/or private investment. The extent to which the United States or for that matter other advanced industrialized countries will pursue a strategy of pushing most transport onto rail will depend, in part on both the commitment to rails as well as a cost accounting of the alternatives and the need for immediate action on climate, energy and transport.
Magnetic Levitation (Maglev) Rail
While the land speed record for passenger rail is still held by the TGV, magnetic levitation rail holds out the possibility of trains that can cruise at a higher rate of speed than ordinary rail. While ordinary trains on well-maintained rails encounter very little friction as compared with wheeled transport on roads, magnetic levitation reduces to practically zero the friction of the train with the track by lifting the train up over the surface of a specially prepared track through the force of electromagnets that repel each other. It is not yet clear whether the additional expense and energy requirements of a maglev system have a significant enough advantage over a high speed rail system to warrant those one-time and on-going expenditures. The only maglev train in operation is a shuttle between Shanghai city center and Pudong airport, a 30 km (18 miles) trip that is covered in 7 minutes, 20 seconds, reaching at one point 267 miles per hour (421 km/hr). There is a controversial proposal that a maglev line be built between Disneyland in Anaheim California and Las Vegas, though such a project seems designed more as a tourist attraction than a replacement for either road or high volume air traffic. Maglev is yet another step into the realm of high profile newer technologies that while potentially promising, are even longer-term prospects than building a functioning rail network of any description.
New Electrified Urban and Commuter Rail
Even in the United States during the cheap fossil fuel era, some urban and commuter rail projects were built as a sign of urban revitalization and smart development efforts. While subways were usually built in the pre-1970 era of massive infrastructure projects, surface rail projects, sometimes called light rail have been built more recently in cities like Portland that were modeled on European street rail systems. These rail projects can operate both above and below ground, thereby blurring the distinction between subway and surface rail. Los Angeles’ Metro light rail system with underground and surface segments, which initially was considered by critics to be an expensive feel-good project, may start to become more useful to Angelenos as high oil prices start to take their toll.
While light rail is popular with commuters, there are controversies associated with it, including whether to grade-separate light rail from automobile traffic and pedestrians. While the initial selling point of light rail was its lesser expense than subways, grade separation adds considerable additional expense. A controversy in Los Angeles about a new line to the West Side, now splitting formerly allied transit advocates, illustrates some of the tough issues associated with the degree to which streetcars are integrated or separated from traffic.
The implementation of regional or suburban commuter rail on existing tracks would seem to be less expensive, though coordinating and balancing passenger traffic with freight traffic remains a challenge. The electrification of stretches of rail will require coordination between private freight companies that own the rights of way and the public agencies that now run US passenger rail.
Electrified Roadway Systems
Trolleybuses are one of the “sleeper” solutions to our climate and energy concerns in urban, suburban and even medium-sized towns. Almost any bus route can be turned into a trolleybus route with the installation of overhead wiring, making them substantially less expensive per mile to build than rail-based systems. Trolleybus systems were most popular in the middle of the 20th century and remain particularly widespread in cities of Central and Eastern Europe. The advent of cheaper and more flexible diesel bus systems led to a decline in trolleybuses which of course require the greater initial capital expense. In the US, trolleybus systems are operating in San Francisco, Seattle, Dayton, and Boston. Dayton has used electric public transport for now almost 120 years continuously.
Trolleybuses are ordinary buses with an electric motor instead of a diesel engine and twin trolley poles on top that connect the bus to the electric grid. Because electric motors have greater torque than equivalent diesel engines trolleybuses are well suited for very hilly cities and are equally good at flat stretches with excellent acceleration and high power-to-weight ratio. Negatives for trolleybuses, as for all transport systems using overhead wires, are the visual appearance of wires and designing the system to enable buses to pass each other. Transit riders also prefer riding smoother railed systems and while trolleybuses avoid the smell of diesel buses still share the ride quality of other buses. Also trolley poles can come off the wires requiring manual or automatic pole replacement. As climate and energy concerns rise in importance, the drawbacks of trolleybuses start to seem trivial or mere technical challenges.
Bus-Rapid Transit and Trolleybuses
Bus Rapid Transit (BRT) is a system that segregates bus traffic from other traffic, allowing buses to achieve average speeds closer to 20 mph including stops rather than the more typical 8 mph in regular traffic. BRT can be applied to any buses but if combined with Trolleybuses, BRT allows trolleybuses to achieve faster travel speeds through crowded urban and suburban streets than when intermingled with traffic. The much studied transit system of the Brazilian city of Curitiba makes extensive use of BRT.
Grid-Optional Road Vehicles
A very exciting area of growth despite little attention has been the development of “dual-mode” or hybrid road vehicles that can travel attached to the grid or can use a battery or diesel engine to travel independently of the grid for a few miles or many miles. Newer trolleybuses now have a battery pack that allows these buses to travel a few miles on battery power alone. Currently in operation in Boston is a dual mode diesel and electric trolleybus called the Silver Line, which travels from Logan Airport as a diesel bus then attaching within a minute to overhead wires to traverse a dedicated BRT/subway into the center city. While currently something of a novelty, this type of re-attachable vehicle will have a vast set of applications in a world of diminishing oil and rising climate concern. One can imagine long-distance trucks that take advantage of grid electricity on stretches of highway, detaching from the grid to make deliveries and then returning to use grid electricity on truck routes.
With grid-optional road vehicles that can detach and reattach to the grid either in staging areas or on the go comes the possibility for road-going dual mode trucks and buses to use the grid to travel long distances just as do trains but with greater flexibility. An electrified highway with overhead wires allows all-electric or dual-fuel large road-going vehicles to travel long distances without carrying large batteries. A challenge in such a set up would be maintaining voltage levels in such a wire as demand for power would be unscheduled unlike that experienced in a closed train or trolley system. The power management system as well as the attachment and reattachment devices for such vehicles would require some development and testing. Electrified highways could enable the continued usage to something approaching their capacity of existing highway infrastructure in tandem with railways in an era of ever more expensive fossil fuels.
As suggested above, a trolley or pantograph can be mounted on any vehicle with a electric motor as a means to connect the vehicle to the grid for energy. Trolleytrucks have been used in urban delivery and in mining operations. If electric wires can be strung over or next to a field, tractors could use trolleys rather than batteries to do work in the fields. 18-wheelers and other long-distance trucks would be naturals for using a trolley, if catenary wires are strung over highways. An energy storage medium, either a battery or an electric generator using liquid fuel, an electric motor, and a trolley to tap into electric can allow any vehicle with tires to become a grid-optional vehicle.
Personal Rapid Transit
A new system of public transport has been under study for the last 20 years that seeks to combine the best of private vehicle use with public transport. Personal Rapid Transit or PRT uses advances in computer control and satellite navigation to create a system of automated 4-6 person lightweight vehicles or “pods” on an elevated or ground-based track that can be entered by passengers at a number of stations around a network-like system. Passengers then select a destination and the vehicle then takes them to the selected end-station. Personal rapid transit has, at least in theory, the potential to be one of the most energy efficient means of transporting people in suburban or dispersed urban areas, as vehicles are only activated and use energy when there is demand for them. By contrast scheduled mass transit can usually only achieve at best a load factor of 20-30%, meaning that on average 70-80% of seats are empty on buses, trams, and subways. Especially at off hours, mass transit will generally operate at low load factors.
By contrast PRT in theory offers the possibility for higher load factors and lower energy use, especially at off hours, as each “pod” might contain only 2 to 4 seats. PRT also offers the possibility for a variety of sizes of “pod” depending upon the size of the group, though this variety would add to the complexity of PRT stations. Theoretically PRT could approach a load factor of 50% and lower overall system energy use with 24 hour availability.
PRT however is a controversial concept as its advocates have often portrayed mass transit in pejorative terms that confirm the prejudices of individual vehicle owners that riding with strangers is a dangerous and unpleasant affair. In Austin, TX, advocates of a light rail system and those of a PRT system were diametrically opposed and highly critical of each others’ plans. The lack of experience especially with rush hour conditions make PRT plans seem at the moment more theory than practice. The idea that PRT would require a new system of suspended guideways at height of approximately 20 feet over ground might be more intrusive than the ground-level transit options it attempts to replace.
It may be that in a post fossil fuel age that mass transit and PRT might both have a place in an electric transit system. PRT’s strength at off hours may complement mass transit’s strengths at rush hours.
Pulling the Ripcord
Battery electric vehicles are coming and will enable a new age of sustainable automobility. However, it will be a long time before we can store anything close to the amount of energy in diesel fuel in the same weight and volume in a battery. To enable electricity and eventually renewable electricity to power transport as soon as we need it, an electric transport infrastructure that directly powers trains, trolleybuses, streetcars, and perhaps other work vehicles from the grid will enable commerce to continue without a dependence on scarce fossil fuels.
To do this, governments and large companies involved in transport need to start planning for and investing in the post-fossil fuel world. It requires a leap but, given the chaos that fluctuations in oil markets can deliver to our economy, the leap to an electric transport infrastructure is a necessary one. In California, we have an opportunity this fall to the take the first step, but this is only a first step on a long road. Government should take the lead, as building the transmission and distribution infrastructure for electric transport requires the reach and authority of government. On the other hand, supplier firms can help create markets for their products and services by alerting government officials to current and near-future technical possibilities.