# A Comparative Study of Storage Batteries for Electrical Energy Produced by Photovoltaic Panels
## 1 Introduction
### Literature Review  
Ref. [1] presents a solar panel connected to a mains supply through an energy storage system involving batteries. In this case, a system of photovoltaic panels generates the energy needed for supplying local consumers, and surplus energy is stored in batteries for further use. An autonomous hub for co-generating energy is presented in ref. [2]. A new topology for a step-up/step-down convertor is presented in ref. [3]. This system can adjust the output voltage's average value by considering an input voltage fluctuating to the desired value of the reference rate. By means of this type of convertor, Lithium-Ion batteries can be charged by photovoltaic panels. Ref. [4] presents a prototype composed of a 3 kW supply source that simulates the running of solar panels, an electric battery, and an inverter. The prototype allows the charging and discharging cycles of the battery to be evaluated in order to establish the efficiency of electrical energy production by the photovoltaic panels. A comparative analysis of different energy storage methods for complex energetic systems is provided in ref. [5]. The most productive storage methods for complex energetic systems are exemplified in the storage systems of pumped hydroelectric energy, hydrogen systems, and thermal and thermochemical accumulations. In ref. [6], solar panels are used to charge the battery of a hybrid vehicle. As such, in addition to other energy sources, the photovoltaic panels contribute to enhancing the efficiency of the vehicle compared to a vehicle based only on a thermal engine. Ref. [7] presents an economic analysis of photovoltaic systems combined with electrical energy storage systems, revealing an important increase in the self-consumption of electrical energy. As such, the results prove that photovoltaic panels with energy storage systems are more advantageous than those without electrical energy storage systems. Ref. [8] presents an analysis of the most important applications in the electrical energy market where the storage of electrical energy confers several benefits: control over voltage and frequency, spare energy sources, load modeling and leveling, etc. Through a normalization technique based on five functions and a comparative evaluation, 19 electrical energy storage technologies are identified along the energetic chain. For low-scale residential applications, Pb-Acid and Li-Ion batteries are the most efficient, whilst for medium- and large-scale residential applications, as well as for industrial and commercial consumers, advanced Pb-Acid and melted-salt batteries are the most suitable. In ref. [9], a method is presented for calculating the maximum theoretical solar energy storage requirement in order to obtain an independent energy system. This method was applied in Taiwan to assess the annual energy storage requirements up until the year 2030 elaborated in the governmental plan. Refs. [4,10,11] present the usage of the photovoltaic panels for producing electrical energy in combination with the usage of thermal solar panels for supplying energy to residential habitations. These hybrid systems are controlled through various methods and allow the storage of both electrical and thermal energy. Analyses of energy management strategies developed for the systems based on photovoltaic batteries are presented in refs. [12,13]. The simulation and optimization of a photovoltaic system connected with Li-Ion batteries is presented in ref. [14]. Ref. [15] demonstrates how electrical energy produced by photovoltaic panels can be utilized to supply water pumping systems. Solar panels can also be used to charge batteries that supply electric vehicles. Refs. [16-20] present chargers for electric vehicle batteries based on photovoltaic solar panels. Such chargers can be implemented using convertors equipped with IGBT-type CMOS power transistors. Ref. [21] presents an innovative integrated PV-ESS (photovoltaic panel energy storage system) to enhance the speed of charging of an electric vehicle.