Electric bus


An electric bus is a bus that is powered by electricity.
Electric buses can store the electricity on board, or can be fed continuously from an external source.
Buses storing electricity are majorly battery electric buses, in which the electric motor obtains energy from an on-board battery, although examples of other storage modes do exist, such as the gyrobus which uses flywheel energy storage.
When electricity is not stored on board, it is supplied by contact with outside power sources. For example, overhead wires, as in the trolleybus, or with non-contact conductors on the ground, as in online electric vehicles.
This article mostly deals with buses storing the electricity on board.
As of 2019, 99% of the battery electric buses in the world have been deployed in China, with more than 421,000 buses on the road, which is 17% of China's total bus fleet. For comparison, the US had 300, and Europe had 2,250.

History

Electric vehicles have been around since the 19th century. In the early 19th century, researchers in Hungary, the Netherlands, and the United States began exploring the idea of battery-powered vehicles. There had previously been progress with an electric carriage, a horseless carriage that was powered by an electric motor. However, as people wanted to get around more easily and quickly, cars became a faster and more reasonable alternative to horse-drawn carriages.
In 1835, American Thomas Davenport is credited with building the first practical electric vehicle, a small locomotive. He developed a battery-powered electric motor which he used to operate a small model car on a short section of track.
The first successful electric car was made in the United States in 1890. William Morrison of Des Moines, Iowa, built an electric vehicle that could hold up to six passengers and could reach from 6 to 12 miles per hour. Specifications for the 1890 Morrison Electric included 24 storage battery cells mounted under the front seat. The vehicle could travel for a range of 100 miles before needing to be recharged.
This initial invention helped spark interest in electric cars, and automakers started building their own versions around the globe. Due to the extreme sudden interest, electric cars reached their peak popularity by 1900 and made up a majority of all vehicles on the road.
At this time electric cars were the preferred vehicles. Gasoline-powered vehicles required a lot of effort to drive, from changing gears to starting the engine with a hand crank, as well as other cons like strong and unpleasant exhaust fumes.
However, improvements were made to the gasoline-powered car that caused the electric car to lose some momentum. The hand crank was soon replaced with an electric starter and gasoline-powered vehicles became more affordable. Gasoline cars soon overcame the popularity of electric powered vehicles.
By 1935, electric cars practically disappeared. It was not until the 1970s when a gas shortage hit, causing gas prices to soar, that electric cars entered back into the marketplace. Gasoline-powered cars still remained more popular due to better performance and reliability.
The 1990s saw electric cars made more popular as societal concern for the environment began to rise. At the start of the 21st century, the technology of electric cars looked more promising than ever with the release of the Toyota Prius, the first majorly manufactured electric vehicle. Today, electric vehicles are on the rise and continue to advance as more Americans demand a more efficient and eco-friendly vehicle.

Principles

Battery

One of the most popular types of electric buses nowadays are battery electric buses. Battery electric buses have the electricity stored on board the vehicle in a battery. such buses can have a range of over 280 km with just one charge, however extreme temperatures and hills may reduce range. These buses are usually used as city buses due to particularities in limited range.
City driving involves a great deal of accelerating and braking. Due to this, the battery electric bus is superior to diesel bus as it can recharge most of the kinetic energy back into batteries in braking situations. This reduces brake wear on the buses and the use of electric over diesel reduces noise, air and greenhouse gas pollution in cities.
When operating within a city, it is important to minimize the unloaded and rolling weight of the bus. This can be accomplished by using aluminium as the main construction material for a bus. Composite paneling and other lightweight materials can also be used. According to Linkkebus their fully aluminium bus construction is about 3000 kg lighter than comparably-sized modern steel buses. Reducing weight allows for a greater payload and reduces wear to components such as brakes, tires, and joints bringing cost savings to the operator annually.

Charging

Buses may be charged at plug in stations, or on special wireless charging pads.

Capacitors

Buses can use capacitors instead of batteries to store their energy.
Ultracapacitors can only store about 5 percent of the energy that lithium-ion batteries hold for the same weight, limiting them to a couple of miles per charge.
However ultracapacitors can charge and discharge much more rapidly than conventional batteries.
In vehicles that have to stop frequently and predictably as part of normal operation, energy storage based exclusively on ultracapacitors can be a solution.
China is experimenting with a new form of electric bus, known as Capabus, which runs without continuous overhead lines by using power stored in large on-board electric double-layer capacitors, which are quickly recharged whenever the vehicle stops at any bus stop, and fully charged in the terminus.
A few prototypes were being tested in Shanghai in early 2005. In 2006, two commercial bus routes began to use electric double-layer capacitor buses; one of them is route 11 in Shanghai. In 2009, Sinautec Automobile Technologies, based in Arlington, VA, and its Chinese partner, Shanghai Aowei Technology Development Company are testing with 17 forty-one seat Ultracap Buses serving the Greater Shanghai area since 2006 without any major technical problems. Another 60 buses will be delivered early next year with ultracapacitors that supply 10 watt-hours per kilogram.
The buses have very predictable routes and need to stop regularly, every, allowing opportunities for quick recharging.
The trick is to turn some bus stops along the route into charging stations. At these stations, a collector on the top of the bus rises a few feet and touches an overhead charging line. Within a couple of minutes, the ultracapacitor banks stored under the bus seats are fully charged. The buses can also capture energy from braking, and the company says that recharging stations can be equipped with solar panels. A third generation of the product, will give of range per charge or better.
Such a bus was delivered in Sofia, Bulgaria in May 2014 for 9 months' test. It covers 23 km in 2 charges.
Sinautec estimates that one of its buses has one-tenth the energy cost of a diesel bus and can achieve lifetime fuel savings of $200,000. Also, the buses use 40 percent less electricity compared to an electric trolley bus, mainly because they are lighter and have the regenerative braking benefits. The ultracapacitors are made of activated carbon, and have an energy density of six watt-hours per kilogram, but the ultracapacitor bus is also cheaper than lithium-ion battery buses, about 40 percent less expensive, with a far superior reliability rating.
There is also a plug-in hybrid version, which also uses ultracaps.

Future developments

Sinautec is in discussions with MIT's Schindall about developing ultracapacitors of higher energy density using vertically aligned carbon nanotube structures that give the devices more surface area for holding a charge. So far, they are able to get twice the energy density of an existing ultracapacitor, but they are trying to get about five times. This would create an ultracapacitor with one-quarter of the energy density of a lithium-ion battery.
Future developments includes the use of inductive charging under the street, to avoid overhead wiring. A pad under each bus stop and at each stop light along the way would be used.

Drawbacks

As with other electric vehicles, climate control and extremely cold weather will weaken the performance of electric buses. In addition, terrain may pose a challenge to the adoption of electric vehicles that carry stored energy compared to trolleybuses, which draw power from overhead lines. Even when conditions are favorable, internal combustion engine buses are frequently diesel powered, and diesel is relatively inexpensive per mile. High local utility rates and proprietary charging systems pose barriers to adoption.

Makers and models

School use

In 2014, the first production-model all-electric school bus was delivered to the Kings Canyon Unified School District in California's San Joaquin Valley. The Class-A school bus was built by Trans Tech Bus, using an electric powertrain control system developed by Motiv Power Systems, of Foster City, California. The bus was one of four the district ordered. The first round of SST-e buses is partly funded by the AB 118 Air Quality Improvement Program administered by the California Air Resources Board.
The Trans Tech/Motiv vehicle has passed all KCUSD and California Highway Patrol inspections and certifications. Although some diesel hybrids are in use, this is the first modern electric school bus approved for student transportation by any state.
Since 2015, the Canadian manufacturer Lion Bus offers a full size school bus, eLion, with a body made out of composites. It is a regular production version that is built and shipped in volume since early 2016, with around 50 units sold until 2017.

Transit use

Transit authorities that use battery buses or other types of all-electric buses, other than trolleybuses:

Asia

Malaysia

As of 2016, 156,000 buses are being put into service per year in China.

Belarus

Canada

British Columbia
About 650 electric buses were on the road in the US in 2019, about double the 300 estimated to be in use the previous year. In November 2019, orders for new electric buses had outpaced manufacturing capacity.
Cities using electric buses include:
A California mandate required that 15% of new buses after 2011 be electric. The ZBus Regulation is part of the Fleet Rule for Transit Agencies, which is also referred to as the Public Transit Agencies Regulation.
Long Beach, California and the Antelope Valley Transit Authority charge some of their buses on special wireless charging pads located along bus routes.
By 2019, more than 200 e-buses were in service in California. Several hundred more e-buses for California were in backlogged orders.
States without plans for e-buses
In 2019, "only five states, Arkansas, New Hampshire, North Dakota, South Dakota and West Virginia,... no transit agencies planning to operate electric buses or hydrogen fuel cell buses."

Oceania

Australia

Aruba