Semiconductors are n or p-type doped materials, if the two semiconductors are of the same material, the p-n junction thus formed is called a homo-junction (case of silicon). Unlike the homo-junction, the combination of materials of type (I), (II), (III), and (IV) makes it possible to naturally obtain the formation of the p-n junction. The main pathways are cadmium telluride (CdTe), gallium arsenide (GaAs), copper indium sulfide (CIS), and its variant copper indium gallium sulfide (CIGS). Solar cells from this type of so-called hetero-junction are more promising for photovoltaic conversion and allow obtaining better efficiency.

The structure and operating principle of CIGS-based solar cells are presented in our previous articles [5] [6] [7] [8]. The differential equations whose resolution makes it possible to describe the operation of solar cells in general and of photovoltaic solar modules, in particular, are the so-called charge transport equations in semiconductor materials and are reduced to three in number, these equations are described in [1] [5] [7].

The development, characterization, modeling and simulation of PV solar cells involve a certain knowledge of the energy source concerned, but also of the technological tool to be used Figure 1 [1]. Numerical simulation is an effective

tool used to understand and solve very complex problems related to the structure of solar cells. It makes it possible to effectively model and improve the conversion efficiency of solar devices, in particular CIGS-based solar cells [1].

Digital simulation is an efficient means which permit to analyze and to understand physical phenomena. This takes more importance in applied research. Indeed, to properly describe the behavior of a system, it becomes necessary to use the digital models of its different components. The digital simulation makes it possible to guide the choice of approximations in analytical approaches and to obtain results directly comparable to those of the experience. In the field of digital simulation, several software has been developed by different institutions for simulation, dimensioning, and analysis of hybrid non-hybrid energy systems.

Simulsen software is used for hydraulic energy. It is mainly intended to simulate the operational management of multiple objective dams over a long period, by a calculation carried out in a daily time step. It makes it possible to assess the satisfaction of these objectives, depending on the water intake and the management instructions envisaged. The software is organized into three main parts: management of parameters and data, calculations, and exploitation of the results.

SAM (System Advisor Model) software is a technical and economic model that calculates the performance and financial parameters of renewable energy projects. SAM simulates the performance of photovoltaic solar energy (PV), thermodynamic solar power plants, solar heating of water, wind energy, geothermal energy, and biomass.

Homer dimensioning software is a tool known for its reliability in the design and analysis of hybrid energy systems, which contain a group of conventional generators, wind turbines, photovoltaic generators, and hydroelectricity [9].

SCAPS-1D and AMPS-1D are the most used simulation software for the modeling and characterization of thin-film solar cells and silicon-based solar cells. Available free of charge for research, this software is the pride of researchers. Detailed studies concerning this two software are presented in [10] [11] [12].

In the rest of our work, in addition to the results of the digital simulation, we will use the literature to defend our theme.

We consider energy renewable, any source of energy that is renewed quickly enough to be considered inexhaustible on the scale of man but also in certain cases of humanity (solar for example). Renewable energies come from regular or constant natural phenomena caused mainly by the sun (solar, hydraulic, wind, and biomass energy), the moon (tidal energy), and the Earth (deep geothermal energy).

The Sun provides enough energy each year to meet more than 7500 times the needs of the world’s population [13]. Our planet receives in the space of one hour the energy equivalent of the annual consumption of the world population. Unfortunately, electricity production is ensured by structures that are sometimes only a few micrometers thickness: photovoltaic cells, the heart of solar panels [13].

In addition to sunshine, Africa has immense potential for different types of renewable energy, particularly hydropower thanks to the many rivers that crisscross the continent, wind power through the winds blowing with different intensities throughout the year in almost the entire continent [14]. Similarly, we note the biomass thanks to the primary forest of Central Africa as well as those encountered across the continent and the bagasse from sugar cane plantations in the different countries. There is also thermal energy and deep geothermal energy which are also exploited in different countries across the continent. Africa therefore has the potential and the capacity to make renewable energies the main driver of its economic and social growth.

The deployment of renewable energies in Africa has important issues. Over the past two decades, the continent has indeed experienced sustained growth, both in terms of gross domestic product and population. This growth should lead to an increase in primary energy demand and also fossil energy resources. If the reduction in technological costs of renewable energies observed on a global scale is more pronounced in Africa, renewable energies will then have to play an important role in the African energy landscape as Rih Berahab notes in its report [2]. A comparative study of the rate of access to energy in different countries in the world carried out by the Montaigne Institute in 2019 [15] shows that only South Africa presents a good report in terms of individual energy consumption (4475 MW/year) (Figure 2). According to Figure 2, we note that North Africa is also doing with individual consumption of around 1287 MW/year. Sub-Saharan Africa recorded the lowest consumption rate with an average of 181 MW/year.

A more detailed study shows that the ASS countries encounter enormous difficulties in terms of access to energy. These difficulties vary from one region to another, from one country to another, and from one area to another, showing sometimes very complex socio-economic inequalities (Figure 3). The price of the kilowatt-hour (KWH) is also very high as well as household rate and company rate and is not within the reach of all citizens even in urban areas, most of which have a daily income below the poverty line (1.9 - 2 USD/day). We can cite most African countries and in particular Burkina Faso, a country where the price per kilowatt-hour is among the most expensive in the world and amounts to 0.213 USD for household tariff and 0.471 USD for company tariff [16]. Figure 3 shows an unequal distribution in terms of energy access in certain countries of Sub-Saharan Africa with individual consumption varying from (57 to 181 KWH/inhabitant in 2012).

These prices remain very expensive compared to the international average which is respectively 0.137 USD household rate and 0.125 USD company tariff [16]. When renewable resources are abundantly used in different sectors of everyday life, they help save significant quantities of fossil fuel. Since 2015, the World Bank had confirmed the installation of several thousand MW by the Independent Power Project in several countries of the ASS (Figure 4) [14].

In 2017, 4.6 TWH (terawatt-hours) of electricity from solar was produced on the continent, this represents only 2% of its electric mix while its theoretical potential is estimated at more than 60 million TWH per year [17]. Figure 5 shows the forecasts in terms of access to electricity 2030 [18]. In comparison, Asia has a theoretical potential of 37.5 million TWH/year and Europe, only 3 million TWH/year. While Africa is largely under-equipped in terms of energy production, we emphasize that it has not yet taken the way to catch up because on 80 GW installed, the photovoltaic represents only 1.5 GW [17]. Recent studies dating from 2018 and conducted by Arnaud Rouget, Africa Analyst at the International Energy Agency confirms that almost half of Africans, or about 600 million people do not have access to electricity, and around 80% Sub-Saharan African

companies are undergoing frequent cuts, causing substantial economic losses [19]. A very interesting aspect of the energy investment efforts of African countries is existing interconnection projects which already make it possible to make up for load shedding in the countries least wealthy in energy resources. As an example, the Ivory Coast alone exchanges interconnection lines with six countries in the West African sub-region, namely Benin, Burkina Faso, Ghana, Liberia, Mali, and Togo [20] allowing these different countries to overcome a little bit to their energy needs.

Nevertheless, more than 90% of the renewable energy potential of the African continent remains unexploited. Ethiopia, South Africa, Egypt, and Angola are home to 37% of hydroelectric capacity. Although it remains below its potential, the consumption of hydroelectricity still experienced significant growth per year during the period 2000-2017, which testifies to the efforts of African countries to invest in this technology.

Studies have effectively shown that the African subcontinent has an unqualified potential for renewable energy, including solar (10 TW) and hydraulics (350 GW, or 10% of the world potential), which rallied to off-Grid technologies, can quickly and low cost the problem of access to electricity in rural areas [14]. One of the scenarios developed by IRENA, estimates that the share of renewable energies in Africa can drop from 17% in 2009 to 50% in 2030 and almost 75% by 2050. Electrical production from these sources could go from 28 GW in 2010 to 800 GW by 2050 with 245 GW generated from photovoltaic solar, 242 GW hydroelectricity, 94 GW of the solar thermal energy, 69 GW of biomass, and 8 GW geothermal energy [2]. This scenario takes into account the objective of achieving universal access to modern energy services by 2030, while considerably reducing long-term costs [2].

The electrical supply of rural areas of Africa represents a considerable issue, which can be a propellant factor in long-term socio-economic development if the conditions of use of clean fuel and cooking technologies, especially sanitary are taken into account. The provision of modern energy services can contribute to the creation of jobs for young people upstream, thus resolving the issue of unemployment. Downstream it will cause large-scale development of African cities both economically and socially. Among other things, we note the development of local skills, the creation of income-generating activities, and the improvement of hygiene measures which are necessary conditions for family and social well-being. This is why in 2013 the International Agency for Renewable Energies in its report stresses that the economic integration of rural and urban areas is crucial to support the sustainable growth of the continent and promote the convergence of living standards of all Africans in the future [21].

The observation is that the rural areas of African countries are very disadvantaged in terms of electrification as can be seen in Figure 6. Figure 6 shows a very

low, even almost non-existent electrification of rural areas in most ECOWAS countries, these results are widespread in almost all countries on the continent. For example, in Nigeria (the first economic power on the continent) the rate of access to electrification drops from 36% of urban areas to rural areas [18]. This creates a social and economic imbalance, making populations living in rural areas very dependent on those in urban areas. A study conducted by the International Institute for Water and Environmental Engineering (2 IE) shows for example in 2015 that the electrification rate in Burkina Faso is 16.4%, the 12^th position in the classification of Economic Comunateum of West African States (ECOWAS) (Figure 6) [22]. On the other hand, we note that only 112 departments are served on the 350 that the country has [22]. There is a significant gap between the rural environment and the urban environment regarding access to modern energies; thus the rate of access to electricity in Burkina Faso in rural areas is only 2.2% against 54.0% in urban areas (Figure 6) [22]. Any long-term approach for Africa must take into account two kinds of different energy issues, namely:

1) Those with African cities are faced: lack of energy in sufficient quantity for the transformation of raw materials and their industrialization;

2) In rural areas: the energy necessary for the production, processing, and transport of local products.

The energy supply of isolated communities is essential, not only to improve the quality of life of individuals but also to give impetus to local businesses and industries. To ensure the development of renewable energies at the rural level, it is necessary to set up specific and sectoral public policies focused on energy and to invest in the long term in research and innovation. This is why projects entering into the context of renewable energies are constantly created, such as the “Desert to Power” project which aims to generate 10 GW of solar capacity in eleven (11) countries in the Sahel region [23].

Figure 7 and Figure 8 present the production capacity of the four most exploited renewable energy types in Africa. According to the two figures, we compare the production capacity of solar energy, wind energy, bioenergy, and hydraulic energy between 2008 and 2018. We note from Figure 7 that the production capacity of bioenergy is greater than those of solar and wind energies between 2008 and 2012. Beyond 2012, the production capacity of wind energy becomes more important until 2017. In 2017, the most important is solar energy production capacity. In Figure 8, we note that between 2008 and 2010, the production capacity of hydraulic energy is significantly equal to the production capacity of all exploited renewable energies (solar, wind, bioenergy, hydraulic). Beyond 2010, the production of the whole becomes more and more important. In short, the results of this study show that investment policies in renewable energy are becoming more and more interesting. We note a production capacity

that increases exponentially over time. As an advantage, there is a significant decrease in the cost of renewable technologies as IRENA points out. Indeed, studies carried out by IRENA Costing Alliance show that the total cost of solar energy projects in Africa between 2013 and 2014 varied in the range of 0.13 to 0.26 USD per kilowatt (KWH).

For example, in South Africa, the lowest cost for utility photovoltaic systems was less than 0.075 USD per KWH, which is among the most competitive photovoltaic projects in Africa. Wind energy in this country has also been subcontracted at prices less than 17% of the prices provided for the two new coal power plants in the country [2].

Still, in comparative dynamics, we note a hydraulic energy production capacity of 25,987 MW in 2009 and 35,681 MW in 2018 against the production of 739 MW in 2009 and 5464 MW in 2018 for wind energy. For solar energy, we note production of 108 MW in 2009 and 6093 MW in 2018 while for bioenergy the production capacity amounted to around 600 MW in 2009 and 1400 MW in 2018. In 2009, Africa totaled a renewable energy production capacity of 26,097 MW, this production exceeded 46,000 MW in 2018 [24] [25]. Other studies carried out by [14] show that in 2016, the energy mix in ASS was 23.7% hydraulics, 1% geothermal energy, 0.9% wind, 0.6% solar, and 0.3% bioenergy [14].

Morocco is one of the few African countries that are increasingly interested in large-scale development of renewable energies. Since 2009, Morocco has embarked on an ambitious energy transition aimed at developing renewable energies, supporting energy efficiency, and reaching a renewable energy mix of at least 52% by 2030 [26]. With an additional installed capacity of 2965 MW since 2018, the energy mix had almost crossed the 35% mark. For the achievement of its objectives, the country has launched large projects and plans to produce an additional 10⁴ MW of renewable energy with the production of 4500 MW of photovoltaic and thermal solar electricity, 4200 MW of wind turbines and 1300 MW of hydraulics at the horizon of 2030. This will permit the Morocco mixt energetic to atteint 20% for solar energy, 20% for wind energy and 12% for hydraulic energy [26].

It emerges from our study that hydraulic energy is the most exploited through the African continent, but with regard to the availability and simplicity of exploitation of PV solar energy, we will study it in the next section.

Photovoltaic conversion is still the only one that is effective in directly converting solar radiation into electrical energy. In developing countries, such as African countries, the mastery of this technique for high-performance and low -cost production rightly deserves researchers in this area. The work carried out in the field of renewable energies in particular in the field of photovoltaic solar energy in the third world in general and more particularly in the West African sub-region aims to advance scientific and technological knowledge so that energy policy in our countries can benefit from advances in this sector. Several research works have been carried out to promote the popularization of this energy category [1] [5] [6] [7] [8] [27] [28] [29] [30] [31].