Abstract
The present article focuses on the calculation of the wind capacity credit by integrating the Moroccan project on the wind energy of 1000 MW in 2020. After an introduction to the Moroccan Integrated Wind Energy Project, a wind capacity credit assessment program will be implemented on Matlab software including the whole information about “installed capacity, number of plants, failure rate, types of installed units, peak demand etc.” This program will be used to calculate the safety rate of an electrical system as well as the capacity credit of Morocco’s electricity production network. This section will be built in two phases: the first phase will examine the impact of TAZA wind farm with an installed power of 150 MW, while the second phase will focus on the generalization of this study on all the wind farms that will be injected to the Moroccan grid in 2020. The research provides conclusion according to comments and assessment of the impact of this electric energy integration based on the wind generation.
Introduction
As part of its energy strategy, Morocco undertakes a vast wind energy program, to support the development of renewable energy and energy efficiency in the country. As a result, a very ambitious program for the development of these renewable energies has recently been adopted by the Moroccan government. Also, Morocco has an important wind resource with regions exceeding 10 m/s for the average annual wind speed (Figure 1), in particular:
The average annual speeds in towns of Essaouira, Tangier, and Tetouan are between 9.5 and 11 m/s.
Tarfaya, Taza, and Dakhla are the towns with average annual speeds between 7.5 m/s and 9.5 m/s.

Map of the average wind speed in Morocco (m/s) (Kousksou et al., 2014).
A first wind map of the country showed that the northern zone (Tangier to Tetouan) and the coastal strip from Tarfaya to Lagouira present exceptional sites with regular winds and average speeds sufficient to develop profitable projects.
Thus, the Moroccan Integrated Wind Energy Project (IEP), spanning a period of 10 years for a total investment estimated at 31.5 billion Moroccan dirhams, will enable the country to increase the installed wind power capacity from 280 MW in 2010 to 2000 MW in 2020. The goal of Moroccan IEP is to install 1600 MW of new wind farms in 2020 as follows (Azeroual et al., 2018; Kousksou et al., 2014):
600 MW under development: Tarfaya (300 MW), Akhfenir (200 MW), Bab El Oued (50 MW), and Haouma (50 MW);
1,000 MW planned on five new sites chosen for their great potential: Tangier 2 (150 MW), Koudia El Baida in Tetouan (300 MW), Taza (150 MW), Tiskrad in Laayoune (300 MW), and Boujdour (100 MW) (Azeroual et al., 2018; Oumounah, 2018).
The objectives of the Moroccan IEP are not only to ensure customer satisfaction but also to protect the environment. They can be listed as follows:
Increase the share of wind energy in the total power capacity to 14% in 2020;
Achieve a production capacity of 2 GW from wind power and an annual production capacity of 6600 GWh, corresponding to 26% of the current electricity production (Azeroual et al., 2018; Oumounah, 2018);
Save 1.5 million tons of oil annually, and avoiding the emission of 5.6 million tons of CO2 per year. This represents a no less committed to the fight against global warming (Choukri et al., 2017; Kousksou et al., 2015; Oumounah, 2018).
With a large capacity of wind energy that will be injected into the national grid, a particular importance must be attached to the impact of this insertion on the safe operation of the electrical system. In addition and since we are interested in wind power, some constraints are worth mentioning (Bloess et al., 2018):
The wind blows when it wants.
The wind blows as it wants; it is difficult to predict its exact intensity.
The wind blows where it wants and, unfortunately, it does not blow when we need a lot of electricity.
Therefore, the fact that electrical energy cannot be stored, the grid must be balanced to the nearest second (Appino et al., 2018; Bloess et al., 2018). Thus, the large-scale integration of wind energy constitutes a major challenge for the electrical system because it is difficult to stop accurate predictions of energy production. The uncertain nature of wind generation could also have an impact on the safe operation of the system. The operation reliability is considered in this case as the ability of the system to cope with the multiple risks that could disrupt its operation.
In light of all this, a study on the long-term impact of wind power production is necessary. To which level, in terms of capacity and flexibility, can wind power replace conventional power plants? To answer this question, we will use the concept of wind capacity credit (CC).
The wind CC measures the ability of wind plants to replace conventional production capacity in a given system (Castro and Ferreira, 2001; Clack et al., 2017). This definition may seem incomplete because it doesn’t include the impact of wind generation on the system reliability. For this reason, we take the proposed definition by Karki and Po (2007), which adding the influence of the intermittency of this energy on the system reliability. Thus, it is possible to define CC as the potential of wind farms to replace conventional plants without endangering the system or degrading reliability.
For CC calculation, two approaches are commonly used: chronological methods (Castro and Ferreira, 2001) and probabilistic methods (Castro and Ferreira, 2001; Clack et al., 2017; Karki and Po, 2007; Milligan and Parsons, 1999; Voorspools and D’haeseleer, 2006); the results show that the chronological approach can be very useful for the grid operator, while the probabilistic approach is especially useful for grid planning. The chronological methods provide information on the capacity of wind resources to cover peak demand, while the probabilistic methods provide information on the expected CC, obtained through statistical calculations.
Therefore, the aim of this article is to analyze the impact of the wind farms in the safety of the electrical system in accordance with an injection scenario of high wind energy. First, we will study the reliability of Moroccan electrical grid in presence of TAZA wind farm with an installed power of 150 MW and after, we will generalize this study on all wind farms that will be injected to national grid in 2020.
This article is structured as follows: In the second section, the production system reliability in the presence of wind energy is represented. In the third section, the CC calculation with the probabilistic model proposed is analyzed. In the fourth section, the calculation model of wind CC is applied to TAZA wind park. The fifth section presents a generalization on the analysis of CC for wind capacities installed on the national grid by 2020. Finally, the conclusion is summarized in the sixth section.
The reliability of production systems in the presence of wind
The goal of an electrical system is twofold. First, it consists in satisfying the demand at a reasonable cost and ensures with safety the continuity and the quality of service (Allan et al., 1989). Moreover, the determination of a safety criterion is a regular part of the operational reliability studies, namely the reliability of the electrical grid. Therefore, reliability refers to the ability of a system to perform a required function; in the case of the electrical grid, the primary function is the supply of electricity from the power plants to the final consumer (Allan and Billinton, 2000; Borges and Dias, 2017). Moreover, the ability of a system to meet the conditions established in the production system is quantified by various criteria called “reliability indices.” In the scientific literature, two methods are mainly mentioned (analytic approach and simulation approach). The analytical approach is the most used in the planning of the electric grid because it has fewer computer constraints and it is faster during its running. Thus, analytic approach will be adopted for this study.
The CC analysis
The analytical approach that can be used to evaluate the adequacy of a particular production system is composed of three parts as shown in Figure 2. In addition, the combination of the production and load model through a risk model makes it possible to determine the safety degree of a particular system. Also, the determination of the risk model consists in calculating the reliability index for covering the total demand of the electrical system. Indeed, reliability calculations are based on the calculation of probabilistic indicators at the time of peak demand. These indicators indicate the level of loss of production to cover the demand (Billinton et al., 1996; Schenk et al., 1984; Wangdee and Billinton, 2006). Furthermore, the most failure criterion used for the production planning and future capacities for the electrical system is the LOLE (loss of load expectation) index (Wangdee and Billinton, 2006). It can be described as the expected number of hours of failure during which the peak demand can exceed the available generation capacity. This indicator also gives the number of hours during which the load loss can occur (Singh and Kim, 1988).

Evaluation model of the adequacy of the electricity production systems.
In our study, in order to determine the wind CC we will model the electrical system in a probabilistic way. The probabilistic model of an electrical system must make it possible to describe the behavior of the uncertain variables of the system and the correlations between these uncertainties (Figure 3). Thus, the input parameters of the probabilistic model of the electrical system as we define it give way to a set of probability distributions, each probability characterizing the variation of a parameter (Mengshoel et al., 2010).

The probabilistic model for wind CC analysis.
The proposed wind CC determination algorithm presented in Figure 3 receives as inputs the characteristics of the electrical system:
The conventional production units and their default rates;
The system consumption data;
The wind profile of the site on which the wind turbines will be installed;
The power curve of the wind turbines that will be installed.
The wind CC will be determined after a comparative study of the reliability of the system without and with the presence of wind energy production. The wind CC analysis is done according to the criterion of replacement of the conventional production; this means that a unit A of capacity X MW will be removed from the system. The objective is to estimate the minimum capacity of wind power to be installed by keeping the same level of reliability.
The explanation in parametric form is as follows: When an X MW capacity is removed from the system, the safety rates
Consequently, the credit of capacity can be calculated by the following expression
In order to automate this computation which is expensive, we will implement the algorithm proposed by National Office of Electricity Water (ONEE; 2018) (Figure 4).

CC determination algorithm.
Conventional production model
The model of the production system is defined as the sets of power generation Units available in a production park. Each unit is characterized by its failure rate. The unavailability rate (forced outage rate (FOR)) is the probability that a unit will be unavailable at a given time.
At the end of 2016, Morocco’s national production plant, with an installed capacity of 11,278 MW, is composed of thermal, hydraulic, interconnection plants, and also the local production of certain dealers. The details of the park and the FOR are given in Table 1.
Power installed on the national power grid (National Office of Electricity Water, 2018).
FOR: forced outage rate.
The installed capacity increased to 12,813 MW at the end of December 2017 and to 12,983 MW at the end of December 2018 against 11,278 MW in 2016, an increase of 15.11% due to the commissioning of the two coal groups of Safi (2 × 660 MW), Jerada coal group (350 MW) followed by the decommissioning of the existing power plant groups (–135 MW) in 2017, and the commissioning of the M’dez and El Menzel hydropower plants (170 MW) in 2018 (Azeroual et al., 2018).
Load model
The load model is acquired with the construction of the monotone consumption for a given period corresponding to 1 year (8760 h or 365 days; Figure 5).

The monotone of load in 2020.
To construct the monotone of consumption or the cumulative model of load, it is necessary to have the information of the hourly or daily consumption of the system which we will have to classify in descending order, and then we can be able to calculate the weight of each state of consumption.
In the medium term, demand forecasts mainly reflect the needs of industrial customers and private electricity distribution companies in the main cities of the country. These forecasts also cover the assessment of the distribution market in Morocco, which mainly corresponds to rural areas. Thus, the expected growth rate for 2010–2013 is about 6%. Moreover, the evolution of electricity consumption results from the combination of factors from different reasons: economic activity, demography, user behavior, technical progress, development of new uses of electricity, market shares between energy sources, energy control actions, and so on. The basic scenario, relying mainly on economic reforms, focuses on an evolution of 5.82% over the period 2015–2020. This emerging scenario, used as the reference scenario for the development of the Moroccan grid equipment plan, translates a 6% long-term growth (Coopération République du Sénégal—BAD, 2011).
Probabilistic model (risk model)
Once the production and load models are founded, a convolution of these two models is necessary for the risk model establishment that quantifies the risk of the system. This method leads to a possible determination of the reliability indices, which is the risk of loss of load mentioned above. In this study, we will work with the LOLE index, which is the mathematical expectation of failure hours (the number of hours per year during which the available production resource is not sufficient to cover the entire demand) (Yang et al., 2018).
This index can be represented as follows
where
The LOLE is the most widely used index for determining the production capacities required in the medium- and long-term horizons. The reliability level of the national park is determined after the running the MATLAB program; this helps us to calculate the LOLE reliability index, as presented in this chapter. Table 2 shows the result obtained after program simulation on the Moroccan National Grid (MNG).
MNG reliability level.
MNG: Moroccan National Grid; LOLE: loss of load expectation.
Application to the TAZA wind farm
Wind production model for the TAZA park
First, it is necessary to create the unavailability table of the intermittent production. Then, the unavailability of the intermittent production model must be integrated into the unavailability table of the conventional production model. This subsequently allows the convolution between the production model and the cumulative load model to be made, and also to determine the risk level of the system. The safety studies in Karki et al. (2006) and Catalão (2016) present an approach using a specific time series model called “Auto-regressive moving average” to predict a series of wind speed data in a particular region. This approach is difficult to implement if the access to a complete database of wind speed of a particular site is impossible. In our study, we choose to model the distribution of wind by the normal distribution—getting as parameters the mean μ and the standard deviation σ at the site where the wind turbines are installed and the number Nb of wind samples that it is desired to simulate (Karki and Po, 2007). Also, it is necessary to inspect the power variation of each installed turbine, according to the wind speed (Yang et al., 2018).
In order to establish the model of wind generation, we will combine the data of the wind resource on the TAZA park with the wind turbines installed there.
The distribution of wind at the TAZA site is represented in Figure 6.

Wind distribution in the TAZA park.
For this probability distribution, we will consider wind speeds ranging from 0 to 10σ to account the extreme wind variables. The distribution is divided into Nb intervals, with each interval having a length of 10σ/Nb.
In our study, the wind resource data is the mean and the standard deviation. The Taza wind distribution requires a mean μ = 9 m/s and standard deviation σ = 2.79 m/s.
Capacity credit calculation
Based on the previous study, we are going to examine the impact of the TAZA park integration to the national electric grid. In addition, the new safety rate will be calculated and interpreted. Also, the obtained results are represented in Table 3.
Reliability of the hybrid park (conventional + wind).
LOLE: loss of load expectation.
Subsequently, it will proceed to the calculation of the CC granted to the national electric grid following the introduction of 150 MW of wind energy. The addition of 150 MW of wind in the mix of national production has an impact on improving the safety rate of the electrical system; in effect, the safety rate has increased from 0.0413 h/year to 0.0398 h/year.
In order to analyze the CC of the wind park, we will proceed by the same way as presented above; we will remove a certain capacity of thermal energy and replace it by the wind turbines. Furthermore, using the Matlab program already implemented, we will simulate the different scenarios of existing capacities removed from the national park.
The plotted curves in Figure 7 are obtained after having to remove simultaneously 30 MW and 33 MW of conventional production capacities; for each case, the simulation was run to calculate the LOLE in function of the injection of [0, 200] MW wind capacity. According to the curves and after the withdrawal of the two conventional capabilities, the LOLE was degraded. However, once the wind parks were injected, the LOLE marked significant improvement.

Safety ratio according to the injected wind capacity for 30 MW and 33 MW withdrawn.
For those different tests, the TAZA wind farm with its installed capacity of 150 MW may be used to replace only 30 MW units, with the wind power required for the replacement is 135 MW that is below 150 MW of the park. As regards the to replacement of 33 MW units or more, the number of failure hours in the national grid will increase from 0.0413 to 0.0416 (Figure 7). Thus, the TAZA park does not achieve the required level of reliability for the national grid.
The results are summarized in Table 4.
The wind CC of the park of TAZA.
CC: capacity credit.
Generalization on the analysis of CC for wind capacity installed on the MNG by 2020
In the previous section, we have studied in detail the integration of TAZA wind farm impact on the safety rate of the national grid, and the conventional production capacity which can be removed without impacting the safety parameters of the grid. In addition, the Moroccan Government envisage the injection of a significant amount of wind parks by the year 2020. Moreover, considering the continuous increase of the annual load consumed at the level of the country, we will go on to consider the impact of all these parks on the national grid in terms of overall operational safety and in terms of the total capacity that can be removed safely.
The Moroccan IEP which consists of injecting a total power of 2000 MW in wind energy before 2020 will contribute certainly in
Development of Morocco’s potential in renewable energy;
Optimization of fossil source production;
Postpone the realization of the new conventional power plants of production;
Improve the safety of the electrical network;
Improved power quality of electric power served to customers;
Face the perpetual increase of the annual consumption;
Winning in the emission of greenhouse gases and contribute to saving our planet against climate change due to greenhouse gases.
The Moroccan IEP is distributed as follows:
280 MW already achieved and in service;
720 MW in development by the private sector;
1000 MW to be built on five new sites, and which will be commissioned between 2018 and 2020 according to the program in Table 5.
The wind capacities planned to be installed in Morocco before 2020.
The previous approach to studying the impact of the integration of the TAZA wind farm will be used to determine the operational reliability rate of the power grid, and to calculate the CC. Furthermore, the approach will be used to calculate the CC of wind farms planned to be installed on the national grid before 2020.
In a concern to obtain reliable and significant results, the already implemented program is made annually by certain elements, in order to make the assumptions of its functioning closer to reality, particularly:
The growth rate of demand for energy consumed is about 5%.
Complete the Matlab program on existing production facilities by means of conventional production facilities which are scheduled to be commissioned before 2020 as shown in Table 6.
As regard the year of study, the wind farms already in operation are well declared in the Matlab program on existing means of production.
The conventional capacity installed in Morocco by 2020.
The scenarios decided for the simulation work are as follows:
The Scenario to add wind capacities of 100, 150, 200, 300, and 1000 MW each time;
The Scenario to remove from the park of conventional production the respective capacities of 33, 39, 42, 75, 95, 100, 111, 143, 153, and 170 MVA.
The two scenarios were made in order to simulate the wind farms needed to be added before 2020 and to verify the traditional production capacities which can be withdrawn each time following the new integration of the parks.
The objective of this work is to
Calculate the LOLE for each scenario;
Calculate the wind capacities required to substitute the conventional capacities removed;
Calculate the CC for different scenarios.
The various simulations realized for the calculation of the safety rate (LOLE) of the electrical system according to the connection of the new wind farms planned before 2020 are represented in Table 7, showing that as long as the part of the wind energies increase in the national energy mix, the LOLE improves advantage, since its variation is almost linear, as represented in Figure 8.
The LOLE (h/year), CC, and the IWC for each conventional capacity removed.
LOLE: loss of load expectation; CC: capacity credit; IWC: injected wind capacity.

Safety rate (LOLE) according to the injected wind capacity.
The injection of renewable energies based on the wind turbine makes it possible to increase the safety rate of the electrical network in a normal situation and a safe environment.
Figure 9 shows the simulation results for various scenarios realized in Table 7.

The capacity credit and the wind capacity injected according to the removed conventional capacity.
From the results obtained in Figure 9, it can be concluded that
The advantageous injection of wind energies increases the reliability of the electrical network in an almost linear way.
In 2020, a scenario is envisaged to substitute a conventional power of about 160 MVA without impacting the safety level of the electrical network. This power is equivalent to two groups of 80 MVA about “2 × 80 MVA”.
The CC increased until the end of 2017 and subsequently decreased to reach a value in 2020 of 16.58% against a value of 23.17% in 2017. This means that if the wind energy represents a significant part of the mixing energy, we can say that the CC of the wind energy is reduced.
In the term of this study the Moroccan IEP which aims to achieve a part of wind power of 2000 MW in the national mix energy presents several advantages:
Allow benefiting from an important level of operating safety of the electrical network;
Avoid the power supply interruptions in the event of an incident in the grid;
Allow maintenance operations on conventional production plants, which generally take a long time;
Benefit from the electrical energy generated from renewable sources with an interesting cost price;
Adequacy in primary, secondary, and tertiary reserves, this refers to the capacity of the electrical system to cope with any imbalance, for example, in case of an unforeseen change in demand or in case of a loss of production.
Conclusion
The reliability study conducted in this article has demonstrated that wind energy can contribute to system safety, and replace a part of installed conventional capacity measured by the CC. The CC is estimated in this article basing on the probability of the national grid reliability, which becomes more complex when the system dimension is important. For this reason, we relied on the existing literature about the reliability and the operation safety, using existing models to deepen them with different parametric criteria. It has also been observed that the CC is reduced linearly according to the injection rate of the wind turbine and is effectively dependent on the conventional power stations considered. Consequently, in a perspective of massive integration of wind power, conventional production will have to be put in place to mitigate the deterioration of CC and preserve the reliability of the system.
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
