## 1 Introduction  
In this study, a novel arrangement of cylindrical supercapacitors (SCs) stack is proposed. The possibility of combining aligned and staggered arrangement in order to lower the temperature rise in the most disadvantaged rows is investigated experimentally and numerically. Supercapacitors (SCs) are energy storage devices that store energy through a physical process of charge separation at the solid/liquid interface [1]. They have high power, power density, efficiency, and cycle life, but low energy density [2]. In particular, they have the advantage of being effective at very low temperatures [3]. A supercapacitor mainly consists of current collectors (usually made of aluminum), electrodes (anode and cathode) generally made of activated carbon impregnated with an organic or aqueous electrolyte, and a separator, which isolates the two electrodes. This composite is subsequently rolled and placed into a container. It should be noted that SCs are not only capable of discharging in a few seconds, but they can still charge at the same time [4]. In addition, one of the most important benefits of SCs is their lifespan. SCs represent an interesting alternative to conventional batteries. They provide higher power compared to batteries but lower than electrolytic capacitors. Their specific energy is much higher than that of the capacitors, but they cannot store the same amount of charge as the batteries [4]. Therefore, these devices are interesting since they can be placed from the point of view of their applicability, between capacitors and batteries, as they are able to store large amounts of energy. However, they do not offer very high densities due to their storage mechanism. This is the main reason why SCs are used in applications, where there is need to store or to release quick power peak [5; 6]. Nowadays, SCs are used in automotive applications [7] and transportation [8; 9; 10]. SCs are also used for the electronic devices such as the uninterruptible power supplies and the volatile memory backups in PCs [6]. The third area of use consists of the energy harvesting systems as the renewable energy applications, where SCs play a supplementary role next to the conventional batteries [6; 11]. In the built urban environment, SCs have huge advantages in improving the power quality of microgrids [12]. They are used for energy recovery control in elevators with automatic rescue application [13] or for optimal design and energy management in multi-energy collaborative clean energy network development [12; 14]. These kinds of devices are usually located in harsh electrical and thermal conditions and therefore require good thermal management to preserve their electrical properties and to increase their service life. [PERSON] [15] have shown that the capacity of the SCs decreases if the temperature increases; the dissipated power increases and the energy stored in the supercapacitor decreases with temperature. Therefore, the efficiency of SCs decreases. In addition, there are several disadvantages at high temperature such as connection hot spots, premature aging, variation in series resistance, leakage resistance, and electrolyte damage. In conclusion the SCs need a cooling system when temperature exceeds approximately 65 \({}^{\circ}\)C, which is usually the maximum operating temperature value [16]. The cooling systems used for the SCs and for the batteries are broadly classified into two categories [5; 17; 18; 19]: active and passive. Another classification [20] provides five methods for thermal management systems regarding the energy storage units: air cooling systems, liquid cooling systems, phase change material (PCM) cooling, heat pipes, and a composite cooling strategy. The active cooling system with airflow forced convection is usually used since it provides a compact structure and a cost-effective feature. The SCs used in modules are generally cylindrical in shape, and their cooling is usually achieved by blowing air, normal to the lateral surface of the cylinders [21].