Electric bus

Battery electric bus

One of the most popular electric buses nowadays are the battery electric buses. They have stored the electricity on board in a battery. Today such buses have a range over 200 km with one charge. These buses are usually used because of its limited range as city buses. As a city bus with all costs they are cheaper than a comparable diesel bus.

City driving mostly is accelerating and braking the battery electric bus is superior to diesel buses as it can recharge most of the kinetic energy back to batteries in braking situations. This reduces brake wear and it also improves air quality in city centers.

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 3000kg lighter than comparably-sized modern steel buses (curb weight 9500kg) . Reducing weight allows for a greater payload and reduces wear to components such as brakes, tires, and joints bringing costs savings to the operator.

Capabus

The best ultracapacitors can only store about 5 percent of the energy that lithium-ion batteries hold, limiting them to a couple of miles per charge. This makes them ineffective as an energy storage medium for passenger vehicles. But what ultracapacitors lack in range they make up in their ability to rapidly charge and discharge. So in vehicles that have to stop frequently and predictably as part of normal operation, energy storage based exclusively on ultracapacitors begins to make sense.

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 onboard electric double-layer capacitors, which are quickly recharged whenever the vehicle stops at any bus stop (under so-called electric umbrellas), 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 3 miles (4.8 km), 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 20 miles (32 km) 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 (for comparison, a high-performance lithium-ion battery can achieve 200 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.

Proterra's EcoRide BE35 transit bus, called the Ecoliner by Foothill Transit in West Covina, California, is the world’s first heavy duty, fast charge, battery-electric bus. Proterra's ProDrive drive-system uses a UQM motor and regenerative braking that captures 90% of the available energy and returns it to the TerraVolt energy storage system, which in turn increases the total distance the bus can drive by 31-35%. It can travel 30–40 miles on a single charge, is up to 600% more fuel-efficient than a typical diesel or CNG bus, and produces 44% less carbon than CNG.

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.

Pantographs and underbody collectors at bus stops

Pantographs and underbody collectors are integrated in bus stops to quick electric bus recharge, making possible to use a smaller battery on the bus, which reduces the investment and subsequent costs.

Solar-charged

Tindo is an experimental battery electric bus being tested in Adelaide, Australia. The word "Tindo" comes from the aboriginal word for sun. The bus will get its electricity from a photovoltaic system on Adelaide's central bus station. Rides are free as part of Adelaide's public transport system.

Zinc

There is a 40-foot (12.2 m) pure electric bus being developed, using a pre-commercial battery technology. Electric Fuel Corporation is developing and demonstrating a 40-foot (12.2 m) electric bus powered by a zinc air cell, along with an ultracapacitor. The zinc-air energy device, often described as a battery, converts zinc to zinc oxide in a process that provides energy to the bus. The bus is not recharged; instead, the zinc oxide cartridges are swapped out for new zinc ones. This bus has shown a range of over 100 miles (160 km) in testing and has been demonstrated in Las Vegas, Nevada. However, this technology is in the development phase, and several major hurdles must be overcome before it can be adopted for transit fleet use, including available refueling infrastructure or use in bus stations.

Air conditioning

Solar panels and supercapacitors are used in some electric buses to power the specific air conditioning circuit.

School Buses

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, CA. The bus was one of four the district ordered. The first round of SST-e buses (as they are called) 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. [3]

Makers and models

Transit use

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

Malaysia

India

China

As of 2016, greater than 40,000 buses are being put into service per year in China.

Japan

South Korea

Finland

France

Great Britain

Italy

Netherlands

Russia

Spain

Sweden

Switzerland

Canada

Ontario

Québec

United States

California

There is a Californian mandate (Zero Emission Bus, in short, ZBus) 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.

Aruba

Brazil

Chile

Colombia

Uruguay