# Evaluation of Investments in Wind Energy Projects, under Uncertainty. State of the Art Review
## 4 Results Analysis
### Types of Uncertainties Explored in Publications with a Real Options Approach  
Uncertainty is inherent in events where possible outcomes are not known, and, therefore, their probability of occurrence cannot be quantifiable. Regarding projects, uncertainty grows over time, conditioning the occurrence of viability. The management of uncertainty, over the years, has always been a critical variable for decision-makers [130]. In the energy sector, including wind energy, decision-making is generally always conditioned by a level of uncertainty in the data [131].  
In the selected articles, with a real options approach, 28 types of uncertainties were identified, which were grouped into nine categories: 1. Power generation, 2. Environmental conditions, 3. Energy price, 4. Costs, 5. Revenues, 6. Regulatory policies, 7. Market, 8. Wind conditions, and 9. Technological progress, as shown in Table 4.  
\begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt}} \hline
**1. Power Generation** & **5. Regulatory Policies** \\
1.1. Electricity charge & 5.1. Production certificates \\
1.2. Wind energy level & 5.2. Changes in asset rates \\
1.3. Energy production & 5.3. Credits policy \\
1.4. Wind turbine hours of use & 5.4. Government policies \\
1.5. Investment planning & 5.5. Feed-in rates-subsidies \\
1.6. Future deployment of wind energy & **6. Market** \\
**2. Environmental** & 6.1. Market conditions \\
2.1. Climate change & 6.2. Price index \\
2.2. Solar irradiation & 6.3. Demand for electricity \\
**3. Prices** & **7. Wind Conditions** \\
3.1. Electricity price & 7.1. Wind disponibility \\
3.2. Carbon price & 7.2. Wind intensity \\
3.3. Corn price & 7.3. Wind speed \\
**4. Costs** & 7.4. Wind intermittency \\
4.1. Capital costs & **8. Technological Progress** \\
4.2. Investment costs & 8.1. Alternative technology \\
8.2. Technology levels & 8.2. Technology levels \\
8.3. Learning speed & \\ \hline \end{tabular}
\end{table}
Table 4: Types of uncertainties explored in research with a real options approach.  
4. Costs studies were integrated that analyze the uncertainties caused by the incidence of the behavior of costs in the profitability of the investment, whether they are capital costs or investment costs. Both costs were studied in four publications, as shown in Figure 7. 5. Regulatory policies include the uncertainties caused by changes implemented in the policies for the generation of wind energy, among which are production certificates, changes in asset tariff, credit policy, government policies, and feed-in tariffs-subsidies. The rates of food and subsidies have been the most studied by researchers, being considered in five publications, as reflected in Figure 8.  
Figure 6: Energy price.  
Figure 7: Costs.  
* 7. Wind conditions addresses uncertainties caused by variability of the wind characteristics in the generation of wind energy, such as the availability of wind, its intensity, its speed, and its intermittency. After the price of electricity, wind conditions are the source of uncertainty that generates the greatest interest in the studies analyzed, especially wind speed, as it has a great impact on the generation of wind energy. Wind speed was studied in six publications, as shown in Figure 10.  
Figure 8: Regulatory policies.  
Figure 9: Market.  
11. Technological progress.  
Table 5 shows, in a disaggregated manner, the type of uncertainty considered in each of the studies with a focus on real options to evaluate investment in wind systems, taking into account the categorization of Table 4. It is observed that 62.5% of the studies treat the price of electricity as a source of uncertainty, 18.8% wind speed, and 15.6% feeding-subsidy rates.  
Figure 11: Technological progress.  
Figure 10: Wind conditions.