# The Role of Renewable Energy Sources and Industry 4.0 Focus for Africa: A Review
## 3 Renewable Energy
### Hydropower Stations  
Hydropower generation uses the kinetic energy in moving water to spin turbines that, in turn, spin a generator that generates electricity, as shown in Figure 7.  
The working principle of a hydropower plant is shown in Figure 8.  
Two methods are primarily used to achieve this: reservoir hydropower stations and pumped-storage hydropower stations. Pumped-storage hydropower stations are not suited  
Figure 8: Schematic of a hydropower plant with its structures and components (**a**) general layout form (**b**) block diagram form (72), Reproduced with permission from [PERSON] et al., Renewable and Sustainable Energy Reviews; published by Elsevier, 2007. Figure 7: A sectional view of Kaplan turbine (71), Reproduced with permission from [PERSON], Thermal Power Plant; published by Elsevier, 2017.  
to continuous operation and will not be considered in this instance. In run-of-river applications, the head (inlet) and tail (outlet) races are part of a flowing river. Depending on the installation's size, the river's flow rate, or the requirements stipulated by environmentalists, different mechanisms are used to operate plants of this nature. Notwithstanding, the most fundamental operating mechanism is having water captured by the head raceway flowing into a Francis-type turbine, with the water's momentum impacting the turbine's blades, inducing rotation, and being released back into the river further downstream from the power station via the tail raceway. In this instance, the mass flow rate and the associated kinetic energy of the water passing through the turbine determine how much electrical energy can be produced, with a proportional relationship between electrical energy output and the physical energy input using the water captured by the head raceway flowing into a Francis-type turbine. Hydropower installations are typical in the African continent and other continents around the world. Notably, Africa currently has 37 GW of hydropower generation capacity installed and generates over 130 TWh annually using the same. The continuity of the flow of a river makes hydropower generation a potential candidate for baseload generation. That said, the infrastructure required to produce energy using this mechanism varies significantly depending on the installation size. For example, the REIPPPP in South Africa allowed for hydropower installations up to 5 MW in size. This is small enough for the infrastructure to remain at ground level and use only the river flow. Conversely, Namibia has a hydropower installation located at the northern border that it shares with Angola. It produces 330 MW and accounts for under half of the country's energy needs. However, the river's flow characteristics are sporadic, allowing for complete generation during the summer. The river almost reaches a standstill at other times during the year. To account for this, the Namibian installation has a collection reservoir. It holds enough water to operate all turbines during the entire flow of the river and partial operation during dry periods. This leads to a penstock that allows for an approximate 170 m drop before entering the turbine, thus significantly increasing the kinetic energy of the volume of water flow through the same. The water is then released back into the river a significant distance downstream. This highlights the primary issue with this technology. There needs to be a river with sufficient sustained flow to generate energy that depends on the infrastructure deployed. Africa may have significant lakes and rivers to tap for energy using this technology. Still, it is highly localized since the African continent itself is considered water-scarce, meaning that there is a risk that a given region may need the ability to deploy this technology. Deployment of this technology is also often met with criticism by environmentalists due to the potential impact of the technology on the river fauna and flora. Secondly, the amount of energy may only sometimes be suitably sized to meet the region's energy demands.