# The Role of Renewable Energy Sources and Industry 4.0 Focus for Africa: A Review
## 3 Renewable Energy
### Solar Energy  
Solar energy describes energy derived from the sun, either in heating or by photons that excite electrons in a photoelectric material to produce a current [67]. The data released by International Renewable Energy Agency (IRENA) shows that Egypt had the highest growth, with 581 MW of solar energy in Africa. South Africa contributed 373 MW, making it second on the continent. South Africa has a capacity of 2.5 GW, making it the highest market operational solar system. Kenya was third in 2018, with an estimated 55 MW added to the installed solar capacity. Namibia added 33 MW in 2018, taking installed solar power to 79 MW. The fifth highest was Ghana, adding 25 MW to increase installed capacity to 64 MW [68]. This is summarized in Figure 4. The breakdown of South Africa's installed solar capacity shows that photovoltaic accounts for 2321 MW and concentrated solar power account for 600 MW [69]. Currently, three technologies use solar energy: solar photovoltaic implementations, concentrated solar photovoltaic implementations, concentrated solar power--central tower/heliostat field, and parabolic trough, as illustrated in Figure 5.  
Solar photovoltaic (Solar PV) power plants use the photoelectric effect on a large scale. The electrons energized by the electromagnetic waves do not escape the atoms in the material (most commonly silica). The valence electrons move freely to produce a direct current (DC) at a specific voltage. This electric power--produced by substantial solar cells arranged in panels and strings--is converted to MV (medium voltage: 6.6 kV to 33 kV)  
Figure 3: Renewable-based generation in total electricity generation. Figure 2: Classification of renewable energy sources. alternating current (AC). The conversion to AC from DC aims to minimize heat losses from high electrical currents in cables (P\({}_{\text{loss}}\) = I\({}^{2}\)R). The MV AC is then distributed to a facility substation. It is transformed once more to obtain the electrical grid connection operating voltage (usually 132 kV, 220 kV, 330 kV, or 400 kV) before being injected into the grid. Solar PV panels are sold based on their rated peak power output (output produced under STP conditions utilizing perpendicular irradiance at 1 kW/m\({}^{2}\), considered \"full sun\"). Therefore, one can feel a perpendicular placement concerning solar PV panels' incident sunlight optimal. However, given the Earth's rotational behavior on its axis and tilt to the sun during the year, the solar PV panels' placement and performance are often optimized using software such as PVysyst. Solar PV power plants are also susceptible to some other issues. Soiling losses can reach up to 3%, while temperature losses can exceed 7%. The meteorological irradiance losses are also quite substantial, with deployed solar PV power plants only capturing 18 and 25% of  
Figure 4: A chart of Africa’s top 5 installed solar energy capacity countries in 2018. Figure 5: Types of solar energy technology. the available sunlight to convert into energy. Taking all losses and irradiance losses into consideration, on any given day, you may only produce peak power for a combined time of 4-6 h, depending on placement. The following Figure 6 demonstrates an example of the sun's path throughout a given year in South Africa, read from left to right in terms of the time of day:  
According to the information in Figure 6, there is little to no sunshine in the morning, while peak sun occurs around mid-day. This leads to irradiance losses in solar fields, meaning there are periods when the power output is significantly lower than the rated capacity.