The bicycle has gone from being an old-fashioned recreational product to a less polluting means of transport and a compact, ultra-light personal mobility tool. This is how electrical bicycles will be used as the pillar that could support individual public transport in large cities worldwide. The objective of this manuscript is to detect how worldwide research on the electric bicycle is being developed, and, especially, around which scientific domains is it clustered, to finally identify the main trends in the field. This study has been carried out based on the Scopus database, where all the publications related to the topic of the electric bicycle have been analyzed up to the year 2017. Therefore, research on the global research trends of this topic was conducted. Its evolution over time shows that since 2008 the growth of publications is much higher than in the previous period. The main countries are China and the USA, and it can be inferred that there are two major trend countries with high environmental awareness, which also have a large population and that the electric bicycle is a suitable and sustainable form of transport. Among the main scientific fields, engineering leads in research. The keyword analysis shows that the central theme is electric, then battery and motor stand out. A community detection was applied to detect the six main clusters of this research, largely dedicated to the following topics: Transportation–Environment, Electrical Engineering, Safety, Batteries, Sporting Goods–Urban Planning, and Mechanical Engineering. This manuscript shows that global research trends about the electric bicycle are increasing, and that it should be considered a means of sustainable urban transport and will therefore contribute to energy saving and sustainable energy.
An electric bike is a type of electric vehicle based on a traditional bicycle to which an electric
motor has been added to help propel it . It is an ecological and urban means of transport and its
source of energy is a battery. In the 20th century, electric bicycles began to play a more important role
because they were an economic and simple option for urban transport problems and had environmental advantages , especially in highly populated countries like China . To highlight this fact, it is enough to indicate that over 31 million e-bikes were sold in 2012 . The main advantages of an electric bicycle are both economic and environmental. Among the economic advantages we can find the total cost per kilometer travelled by an electric bicycle (including the energy, purchasing and maintenance), is less than 0.7 cents, compared to $0.031/km for a gasoline scooter , or $0.62/km travelled by car. The batteries of the electric bicycles can be recharged by connecting them to a plug or when pedaling in some gears. In addition, a typical electric bicycle needs 6–8 h to charge the battery and has a range of travel of 35 to 50 km at a speed of about 20 km/h (depending on rider weight) .This means that, with a single battery charge, it would be enough to go to work, visit friends, and return home on a normal day, since statistics show that about half of the trips and procedures of a normal urban person are carried out within a distance of 15 km from his/her house, therefore within the reach of these bicycles.
From an environmental point of view, for petrol car consumption in urban areas, the emissions
are: HC (Hydrocarbons) 3.57 g/km, CO 3.15 g/km, CO2 1.82 g/km, and NOx 2.29 g/km .
Therefore, the electric bicycle, as an alternative means of transport to the car, shows that for every
100 km an average of 8.5 L of gasoline is saved, and this pollution would be avoided.
The electric bicycle as a new form of private transport has led to a new approach to mobility,
especially in cities, both for countries with large populations and for countries that are concerned about the environment. The research on the electric bicycle is relatively new, but today, nobody clearly knows where the efforts are being focused, nor what the main points of interest of the scientific community are. The objective of this manuscript is to detect how the worldwide research of the electric bicycle is being developed, and, especially around which scientific domains it is clustered. Finally, the main trends in this field can be identified.
A Brief Overview of the Electric Bicycle:
Electric bicycles began almost at the same time as traditional bicycles. In the 1890s, several patents
were granted for electric bicycle engines. In 1895, Ogden Bolton was granted in the United States the
patent (US Patent 552,271, 1895) for a bicycle battery with six brush poles, a DC collector and a hub
motor mounted on the rear wheel . In 1897, Hosea W. Libbey in Boston invented an electric bicycle (US Patent 547,441, 1895) that was powered by a double electric motor. That same design was later used by the Giant Lafree e-bikes (electric-assist bicycles) brand in the 1990s .
In 1920, Heinzmann, a German company, started to mass produce electric motors for bikes.
Their first motor was mounted on a tandem. Later, it continued to develop engines that incorporated
German mail distribution bicycles. In the 1930s, Minneapolis-based Lejay Manufacturing registers
patents that are the germ of the GoBike, an electric bicycle with a generator of a Ford T coupled to the rear wheel. Later, Moulton Consultants Ltd. manufactured a double chain transmission, one from the bottom bracket and another from the electric motor. In the 1940s, electric bicycles registered an increase due to a shortage in large motorized vehicles, as a result of the war efforts of the SecondWorldWar. Several patents were granted for prototypes that were eclipsed by the development and investment in the motorcycle industry, which played a more important role during that war. In post-war Europe and Asia, due to the prohibitions to countries like Italy and Japan to build and rearm their aeronautical industry, many engineers who were dedicated to the development of engines for airplanes saw a niche and dedicated themselves to the motorcycle industry, and in the shadows of this development were electric bicycles, which went a bit ignored but nonetheless benefited from the new technologies and innovations in that industry.
However, it was not until the first oil crisis in 1973, that the use of electric bicycles began
to be promoted, although they did not have much popularity. It was in the United States where
electric bicycles played a preponderant role in urban transport as a clean option for the oil problem.
This first mass-marketed model was a bit rough and heavy compared to the current models, as it had
a solid steel frame and was cumbersome to transport. However, it proved to be very versatile and
economical compared to the large and powerful engines of the cars of the seventies. This bicycle, like its predecessors, did not harm the environment nor depend on the fluctuations of the oil market. In 1982, the inventor Egon Gelhard developed a subtype of electric bicycles that worked with the electric cycle pedal principle, where the driver is aided by the electric traction of the engine when pedaling.