*3.2. Pump Centrifuge*

A necessary requirement of the SPS is the motor pump. The latter is made up of two parts: an electric motor coupled to a pump. In this study, the motor used to turn the pump (SQF 0-6-2 DC) is characterized by a nominal current In = 8.4 A, an input voltage ranging from 30 to 300 VDC. In the field of technology, two types of pump technology are generally used in pumping applications: the positive displacement pump and the centrifugal pump [25,26]. The first technology is distinguished by a constant load, whereas centrifugal pumps are distinguished by an aerodynamic characteristic. The latter are characterized by a load of torque that develops with the quadratic form of the drive speed. This characteristic clearly indicates that the drive torque of the pump is almost zero at the start-up. Therefore, the pump can be operated with very low solar irradiation, and as the solar irradiation increases, the drive motor can have a high speed. The proportionality of the different parameters as a function of the speed is expressed by the following equations [27]:

Torque (*Cr*)—speed (*ω*):

$$\mathbb{C}\_{\tau} = A \,\omega^2 \tag{2}$$

Flow (*Q*)—speed (*ω*):

$$\frac{Q\_2}{Q\_1} = \frac{\omega\_2}{\omega\_1} \tag{3}$$

Height (*H*)—speed (*ω*):

$$\frac{H\_2}{H\_1} = \left(\frac{\omega\_2}{\omega\_1}\right)^2\tag{4}$$
