2.1.2. Wind Energy System

The wind speed at hub height varies depending on several factors, such as the wind speed at ground level, the hub height, time (hour, day, season), the nature of the terrain, and the ambient temperature. These variables can be represented by one factor known as the wind profile exponent or wind shear coefficient (α). In the absence of the site-specific data, can be taken as 1/7 [39,40]. The wind speed at hub height (uZ) can be extrapolated using equation A.3. By assuming that the energy generated is constant during the hour and each turbine generates the same amount in the case of having multiple turbines, the total hourly electrical energy generated by a wind turbine(s), Ew, can be estimated by A.4 in App. An under wind energy model section. The Weibull distribution shape parameter of the available wind speed, K can be calculated based on Justus theory using Equation (A5). A wind turbine with 2 MW of rated power from GAMESA company (G114-2.0) was used in this study. It should be noted the hourly TMY wind speeds at ground level were obtained from Meteonorm software.

#### 2.1.3. Hydropower System

Al-Tafilah has the potential to construct two small hydropower systems with a total capacity (Ph) of 1 MW, as reported in [32]. In this study, a 1 MW hydropower system with capacity factor (CFh) of 80% [41] is designed to provide continuous energy generation as part of the baseload of Al-Tafilah, where the annual energy production from the hydropower system, Eh, can be estimated as shown in A.6.

### *2.2. System Modelling and Energy Flow: With and Without an Energy Storage System*

Energy Storage System is introduced into the power system as a solution for the intermittent behavior of renewable energy resources. This way, is it possible to reach a match between supply and demand. In this work, two scenarios consisting of and without an Energy Storage System (ESS) are adopted and discussed for the fitness of a hybrid off-grid system to supply the electricity demand of Al-Tafilah. Flow chart for with and without ESS are introduced in Figure 1. In comparison with other batteries for the ESS, this study considered Zinc-Bromine batteries (ZBB) as they show better performance and lower cost. In this study, the round-trip efficiency of the ZBB was taken as 72% and the depth of discharge was considered as 80% as reported in [42,43].

**Figure 1.** Energy flowchart of the photovoltaic (PV)/wind/hydro hybrid system: (**a**) Without an energy storage system (ESS) and (**b**) with ESS.

To inspect the matching between the energy production from the hybrid system and the demand, the RES Fraction (*FH*), which represents the annual fraction of demand met by the RES, was used. *FH* can be calculated by A.7. The forecasted demand of 2030 was used in this study, where the average hourly demand of Al-Tafilah in 2010 obtained from [44] was used for estimating the 2030 demand. The population of 2030 was forecasted using the Piecewise Cubic Hermite Interpolating Polynomial method, where 1994, 2004, 2015, and 2019 populations were used for this forecast [35,36].
