# Evaluation of Investments in Wind Energy Projects, under Uncertainty. State of the Art Review
## 5 Discussion  
The purpose of this article is to review the literature on the evaluation of investment in wind systems under the real options approach, to determine the inclusion of public opposition (NIMBY projects) as a source of uncertainty, and to identify the flexible strategies implemented to overcome these types of barriers. As a result of the review, no studies related to the subject of public opposition (NIMBY projects) were found under the real options approach; however, some aspects that generate opposition were identified, which could be valued as real options, such as: the creation of participatory public policies; participatory models for decision-making; financial incentive schemes, including tax deductions and permanent investment support or subsidies; associative schemes for participatory financial investment in projects; implementation of technology systems of Renewable Energies at the community level, according to customs and housing conditions; information processes and prior consultations; environmental monitoring and control systems; and building up an institutional capital.  
For the assessment of these opposition generators under the real options approach, some models proposed in studies related to regulatory policies in wind energy projects can be adapted, such as [32; 55; 73; 74; 91; 92; 107; 111; 126]; models that use the decision tree technique to assess real options: [106; 111; 116; 117; 123; 124], or those that use dynamic programming, such as [58; 91].  
Regarding the uncertainties explored in research with a real options approach, most were found to be random variables with continuous states that are discretized over time (price, cost, and wind speeds). However, there are several studies that assume uncertainties as random variables with discrete states at discrete times, modeled by Markov chains, which could be assimilated to model public opposition because they have similar characteristics: climate policy [115], policy changes related to the current support scheme [74], and long-term stochastic uncertainties in the restructured energy market, such as demand and the price of fuel [58].  
Regarding the options to use, you can make use of options to invest now, postpone, or abandon [92; 111; 116], and the same is true for the compound options, the one associated with rate change [126], or the one to either carry out, postpone, or abandon the investment before continuing with the next stage [86; 107; 115; 122].  
From the analysis of public opposition, it follows that, in order to propose flexible strategies, the perception of the community must first be known; then, it must be determined what alternatives are available from the beginning and when these would be presented, based on consumer preferences.  
Given that, despite an exhaustive search in the literature, no studies that included uncertainties, such as public opposition, modeled with current techniques was found, and, therefore, it is not known how people will react, so there is a gap that would be interesting to address, to assess flexibility when this type of uncertainty arises through the real options approach.