By Peter Feuilherade
This article first appeared in the April 2013 issue of e-tech, published by the International Electrotechnical Commission (IEC), Geneva..
A revival after a long decline
More than half the world’s population now live in cities, according to United Nations data, and that percentage is forecast to hit 60% by 2030. By 2025 there will be 37 megacities (22 of them in Asia), each home to more than 10 million people. The growing use of electric buses, trams and metropolitan “light railways” offers an environmentally friendly option to reduce local emission of pollutants significantly in the expanding cities of the future.
Urban public transport systems powered by electricity can trace their origins to 1879 when Berlin launched the world’s first electric suburban railway (S-Bahn), followed by electric trams in 1881 and electric trolleybuses a year later.
With transport systems estimated to account for between 20% and 25% of world energy consumption and CO2 (carbon dioxide) emissions, electric vehicles offer greater efficiency than their diesel counterparts. Using their brakes, they can generate kinetic energy to be recycled back into the power network. Electric engines on buses and trams cause less vibration, making journeys more comfortable for passengers and reducing maintenance time and costs.
Several IEC TCs (Technical Committees) prepare International Standards for the electric buses, trams, trolleybuses and metro/light rail vehicles used in public urban transport networks, as well as the batteries, capacitors and fuel cells used in propulsion systems, and many other components.
Electric buses, which require neither great range nor speed and can be partially recharged during their journeys as they stop for passengers, are seen as the most promising area for potential growth of green urban public transport.
China is the world leader in developing battery electric buses. The southern city of Shenzhen has the world’s largest zero-carbon fleet of all-electric buses and taxis, and plans to have 6 000 electric buses in service by 2015. Shenzhen is also home to the world’s largest manufacturer of electric buses, BYD (Build Your Dreams). The company has started to enter overseas electric bus markets. At the start of 2013 its vehicles received Whole Vehicle Type-Approval from the European Union, giving the company the green light to sell its buses to all EU member countries without further certification.
The number of electric buses in countries other than China is limited but growing.
The US-based market research and consulting firm Pike Research forecast in August 2012 that the global market for all electric-drive buses including hybrid, battery electric and fuel cell buses will grow steadily over the next six years, with a CAGR (Compound Annual Growth Rate) of 26,4% from 2012 to 2018. According to Pike, the largest sales volumes will come in Asia Pacific, with more than 15 000 e-buses being sold in that region in 2018 – 75% of the world total. China will account for the majority of global e-bus sales, Pike predicts. It believes that growth in the e-bus market will accelerate strongly in Eastern Europe and Latin America, the latter driven largely by Brazil. Sales in Western Europe will experience steady growth (around a 20% CAGR), according to Pike.
A December 2012 report by the research and consultancy firm IDTechEx forecast that the market for electric buses and taxis will grow from USD 6,24 billion in 2011 to USD 54 billion in 2021, of which the largest part will be buses. China will become by far the largest market for both electric buses and electric taxis. According to Dr Peter Harrop, chairman of IDTechEx, “in China… over 100 000 electric buses a year will eventually be bought as part of the national programme”.
Trolleybuses are electric buses that use spring-loaded trolley poles to draw their electricity from overhead lines, generally suspended from roadside posts, as distinct from other electric buses that rely on batteries. Because they do not require tracks or rails, they are more flexible than trams and drivers can cross the bus lane, making the installation of a trolleybus system much cheaper. Trolleybuses operate in some 370 cities or metropolitan areas worldwide, according to the Trolley Project, which aims “to unlock the vast potential of trolleybuses to transform public transport systems” across Europe in line with the European Commission’s target to reduce traffic-related CO2 emissions by 60% by 2050.
In the 1960s the tram saw a decline in favour of diesel driven buses, but the backlash in recent years against pollution and dependence on fossil fuels has seen a resurgence of interest in electric trams as another urban transport system that can carry large numbers of passengers efficiently and generates no emissions at the point of use. Tram systems do not need vast financing compared with underground systems, which are typically four times more expensive to construct. However, in addition to its relative high cost, compared to that of buses or trolleybuses, the greatest disadvantage of the tram is its confinement to a set route by the wires and tracks it requires. The largest tram networks are in Melbourne, St Petersburg, Vienna, Berlin, Milan, Toronto, Budapest, Bucharest and Prague. Dozens of cities in North America are exploring or planning tram systems.
Metro and light rail
In a December 2012 study SCI Verkehr GmbH, an international management consultancy based in Germany, forecast the global growth in railway electrification at a CAGR of 3,4% up to 2016.
Market growth is mainly driven by new metro and electric light rail urban transport projects under way on most continents, from major cities in Asia and the Persian Gulf to North and South Africa and North American urban areas.
A metro rapid transit system is an electric passenger railway in an urban area with a high capacity and frequency, typically located either in underground tunnels or on elevated rails above street level. It allows higher capacity with less land use, less environmental impact and a lower cost than typical light rail systems.
Light rail systems use small electric-powered trains or trams that generally have a lower capacity and lower speed than normal trains to serve large metropolitan areas. They usually operate at ground level, but can include underground or overhead zones.
A common feature to rail systems: IEC International Standards
All urban rail systems rely on International Standards developed by IEC TC 9: Electrical equipment and systems for railways. Areas covered include rolling stock, fixed installations, management systems (including communication, signalling and processing systems) for railway operation, their interfaces and their ecological environment. These standards deal with electromechanical and electronic aspects of power components as well as electronic hardware and software components.
Batteries and fuel cells
Buses, which have defined, short routes and daily travel distances of less than 200 km, are well suited to battery-only electric technology. Li-ion (Lithium-ion) technology is the most commonly used. Pure electric buses divide into those using high power density Li-ion batteries alone and those with large banks of supercapacitors in the roof to manage fast charge and discharge and increase battery life. Hydrogen powered fuel-cell vehicles provide longer range than battery electric vehicles. Refuelling times are short and comparable with present internal combustion engine vehicles. Currently, the main drawbacks of hydrogen powered vehicles are the high cost, mainly due to expensive fuel cells, and the lack of refuelling infrastructure. IEC TCs prepare International Standards for batteries and fuel cells used in urban transport systems.
IEC TC 21: Secondary cells and batteries, has prepared standards covering requirements and tests for batteries for road vehicles, locomotives, industrial trucks and mechanical handling equipment. Its work includes standards for performance, reliability, abuse testing and dimensions for hybrid and plug-in hybrid Li-ion batteries, which are seen as one of the most promising types of secondary batteries.
IEC TC 105: Fuel cell technologies, is responsible for standards for fuel cell commercialization and adoption. It focuses on safety, installation and performance of both stationary fuel cell systems and for transportation, both for propulsion and as auxiliary power units.
Almost all fuel cell buses incorporate a battery for energy storage and there is also a balance to be struck in the hybridization of the fuel cell power plant and the supporting battery pack. While fuel cell costs remain high and hydrogen infrastructure sparse, it may be more economical to use battery-dominant buses with fuel cell range extenders. The fuel cell bus sector is showing year-on-year growth, with more prototypes being unveiled. Successful deployments have taken place in Europe, Japan, Canada and the USA but the high capital cost is still a barrier to widespread adoption.
Pike Research forecasts that global demand for Li-ion batteries in electric drive buses will be more than 162 000 kWh in 2012. It expects that demand to grow to more than 1,3 million kWh by 2018, a CAGR of 42%. Fuel cell buses will drive demand for Li-ion batteries as well, but to a lesser degree. Pike Research estimates that they will require around 1 600 kWh in 2012, but will grow to 22 240 kWh by 2018.
More IEC standardization activities for electric urban transport
Electric urban transport systems depend also on standardization work from many other IEC TCs and their SCs, such as, TC 22: Power electronic systems and equipment, TC 36: Insulators; TC 40: Capacitors and resistors for electronic equipment; TC 47: Semiconductor devices, and obviously TC 69: Electric road vehicles and electric industrial trucks, to name only a few. Other TCs may be less obvious, such as TC 56: Dependability, which is involved in rolling stock-related standardization work. It maintains liaison activities with TC 9 and stresses that “without dependable products and services (…) transport [would be] non-functioning (…) there would be numerous car, train (…) accidents”.
“Down to Electric Avenue”
Wireless or induction charging technology to charge electric vehicles, including buses and light rail trains, is in use or undergoing testing in many countries, including South Korea, the USA, Canada, the United Kingdom, Germany, Belgium and Italy.
Wireless charging plates built into the road at bus stops and terminals enable electric buses to be charged wirelessly through a brief connection while passengers get on or off the bus at a stop. This resolves the current battery limitations that prevent an all-electric bus from operating all day off an overnight charge. It would also mean the end of unsightly overhead cables to power trams and trolleybuses. There can be a loss of energy in the transfer, but tests using a light rail train in Germany in 2011 to demonstrate the technical capability of the system under actual conditions of daily operation indicated an efficiency rating above 90%.
Researchers at the Korea Advanced Institute of Science and Technology say the transmitting technology they road tested supplied 180 kW of stable, constant power at 60 kHz to passing vehicles equipped with receivers, and they recorded 85% transmission efficiency. Installing similar chargers at busy traffic lights and junctions and in parking spaces could extend the technology to consumer electric cars.
There are concerns, however, about different competing wireless charging technologies, the costs of installing the infrastructure and its capacity to stand up to extreme weather. Meanwhile companies, notably in China and the USA, have developed ultra-fast charging technology capable of charging an electric bus battery in five to ten minutes.
Other features likely to be become standard in the electric buses of the future include regenerative charge braking, energy harvesting shock absorbers, solar panels and quickly replaceable battery packs.
These and other innovations in transportation and urban mobility are set to play a prominent part in “smart city” projects around the world, a technology market that Pike Research forecasts will be worth USD 20,2 billion annually by 2020.