sustainability Article Electrical Longboard for Everyday Urban Commuting Alexandru Ciocan 1,*, Cosmin Ungureanu 1,2,*, Alin Chitu 1, Elena Carcadea 1 and George Darie 2 1 National Research and Development Institute for Cryogenics and Isotopic Technologies—ICSI Rm. Valcea, 4 Uzinei Street, P.O. Box Râureni 7, 240050 Rm. Valcea, Romania; [email protected] (A.C.); [email protected] (E.C.) 2 Faculty of Power Engineering, Politehnica University of Bucharest, Splaiul Independent, ei 313, P.O. 060042 Bucharest, Romania; [email protected] * Correspondence: [email protected] (A.C.); [email protected] (C.U.) Received: 3 September 2020; Accepted: 28 September 2020; Published: 30 September 2020 Abstract: This paper addresses the possibility of using an electric longboard in daily travel. A conventional longboard was transformed into an electric one and tested in ICSI Rm. Valcea labs. A series of tests were performed both at the laboratory level and, under normal running conditions, outdoors. Nevertheless, two possible scenarios have been taken into consideration. First, when the electric longboard is running on a flat road with a cruise speed, while the second scenario considered was that of climbing a hill with a 10% slope. The results confirmed the expectations and showed that a full charge of the batteries allows a trip over a distance of almost 50 km on a flat route having a consumption of about 10 Wh/km. However, there are some things to keep in mind when making travel distance predictions. The quality and the profile of the road, the weight of the rider, the rider position, all of these are factors which can significantly influence the predictions regarding the travel distance. Moreover, if the optimization is taken into account, several adjustments can be done in choosing the size and wheel model, whether or not to equip the skateboard with suspensions as well as a compromise between power and energy densities when choosing battery type is essential. Keywords: lithium-ion batteries; energy storage; electric longboard; battery management system 1. Introduction In recent years, the problem of air pollution and increasing emissions of carbon dioxide has represented a real concern for scientific community, decision making factors, and the population. We are going through a transition period and a series of decisions have been taken and must continue with the main objective being to limit global warming. At the EU level, several directives have been required over the years considering the CO2 limitations and renewable energy technology integration into the energy sector mix [1–4]. There are several predicted scenarios regarding the roadmaps for 2050 with an interim target for 2030 and a consensus that a higher contribution of renewable sources is hard to achieve without energy storage solutions. Currently the EU proposes a 1 tn Euro budget through the Green-Deal project which aims to finance industrial sectors in order to reach the proposed goals. An important contribution to pollution from the industrial sector is given by transportation, which represents 25–27% of global pollution. In recent years, huge progress has been made in this field, as electric vehicles and hydrogen vehicles are being considered as the alternative to the fossil fuel-driven vehicle [3,4]. Neither technologies are mature yet, but the electric vehicle appears to be more affordable than hydrogen vehicles. Research and development activities have accelerated in order to bring advanced energy storage solutions to the market level, with minimal help from support mechanisms. A decrease in battery prices has been seen since 2015 [5–7]. Sustainability 2020, 12, 8091; doi:10.3390/su12198091 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 8091 2 of 14 Currently, there are three main types of Li-ion cells: cylindrical (with 18650 being the most common standard), pouch, and coin cells having different chemistries, unique properties, and being designed for various applications [6–17]. In the literature, a series of research activities in the field of energy storage are presented [8–12], the lithium batteries being one particular case. Nevertheless, different types of batteries are compared and the autonomy of the life cycle of an electric vehicle is evaluated [7]. Barré et al. [13], Salinas and Kowal [14] and Yi et al. [15] focus their attention on aging mechanisms of Li-ion batteries and algorithms that make the predictions to avoid batteries degradation. A series of key technologies that are correlated with battery modeling, with their state of charge (SOC), state of health (SOH), and the influence of temperature in the use of batteries are presented by Yi et al. [15], Liu et al. [16]. and Zeng et al. [17] refer to reducing energy consumption and the need to use as few resources as possible, highlighting the importance of recycling. Peter et al.[18] evaluate the impact of lithium-ion battery (LIB) in electric vehicle (EV) and made a life cycle assessment, concluding that researchers’ efforts should focus not only on maximizing energy density but also on the life cycle and load efficiency. At the same time, Kang et al. [19] present a study in which they classify batteries according to the raw material used and the level of danger. On the other hand, the car manufacturers have a different approach regarding the type of batteries to be integrated on their vehicles; Tesla used 18650 and later passed to 21700, BMW are using prismatic cells and Nissan Leaf rectangular pouch cells. Regarding battery geometry, most EV markets and suppliers use 18650, but on the other hand the pouch cell market is covered by electronic devices, the most representatives being smartphones and laptops [20]. There are a lot of predictions which say that the number of EV users will increase rapidly; Miao et al. [6] expect 125 million EV by 2030. One of the key elements in batteries’ integration in electric vehicles is given by the battery management system. There are studies [21–27] that address the vehicle control unit and the battery management system, presenting new control systems, new hardware in the loop configurations, and evaluating the reliability of an EV system from the perspective of power supply. Besides mass transportation, another solution for short distance traveling can be represented by individual transport means such as: electric-bikes, scooters, longboards, or hoverboards. All of these can prove to be suitable solutions for commuting to work/school in crowded cities, to explore the neighborhood, or any other trips that do not involve carrying heavy baggage. Ito et al. [12], Muenzel et al. [28] and Yoo et al. [29] investigate the dynamics of the propulsion mechanism of a skateboard using computer simulations based on different lithium-ion battery chemistry. Kuleshov [30,31] followed the linear stability of the skateboard-skater system and develop a model of motion. Hart et al. [32] realized a first attempt of a computational fluid dynamics (CFD) aerodynamic analysis of a downhill skateboard. Varszegi et al. [33] focused their attention on how the balancing effort of the skater influences the stability. Hyvönen et al. [34] conducted a study aimed at seeing how the population of Finland responds to the challenges in the transport system and how they are seeing the use of the light electric vehicle. Studies [35–43] present the most frequent injuries among skateboarders and to which age groups they happen, meanwhile showing the influence of pedestrian crowdedness on light electric vehicle navigation behavior. When it comes to small electric vehicles, they are expected to have a battery with low weight, compact size, plenty of current delivery for quick acceleration, and high capacity for long-range. It is easy to see that the technology is ever-changing and nearer evident to observe that this is the case in the electronics market. If we are looking back several years ago a few people could imagine this evolution, and today, they are not only thoughts but realities. Therefore, this study aimed to present the challenges of riding an electric skateboard and makes the following contributions: (1) On global warming concerns, the paper presents the considerations of using light electric vehicles in everyday travels. (2) Turns a conventional skateboard into an electric one by integrating a battery stack, a battery cooling system, a battery management system (BMS) and finally testing it. Sustainability 2020, 12, 8091 3 of 14 (3) Show laboratory testing results for a battery stack discharging by simulating the travel conditions of an electric longboard both on flat ground and for an uphill (4) Show results from testing the electric longboard functionality in normal driving conditions The work was structured as follows: the first part introduces the topic, presents and briefly describes the issues addressed in a period of energy transition. In Section2, Materials and Methods, the electric longboard configuration is presented, the way it was conceived highlighting the characteristics of each component and proposing at the end of the section a mathematical model. Section3, Results and Discussions, illustrates the results obtained in both laboratory and real-time tests, then are discussed and critically analyzed, with the aim being to evaluate the options and establish strategies to address the issues to improve the system performances. The conclusions are presented in Section4, and convey the essential outcomes of this paper. 2. Materials and Methods First, when we talk about running a light electric vehicle, in this case an electric longboard, it is important to show the difference between power and energy densities. With double the energy we double the range, but power is that which determines how fast we move. A high-power drive train is useless without a high-power battery, mainly if we refer to the situation when we have to climb a hill.