# Evaluation of Investments in Wind Energy Projects, under Uncertainty. State of the Art Review
## 4 Results Analysis
### Studies with a Real Options Approach, Based on the Ends and Purposes of Its Application
The evaluation of energy auctions, portfolios, and energy market investments is focused on proposing schemes to measure immersed risks in private markets and in restructuring, to evaluate investment decisions through energy auctions, or to establish portfolios with possible areas for the development of wind farm projects. Eight studies appear. The evaluation of renewable energy technologies groups the studies focused on optimally supporting the decision to invest in a renewable energy technology, or the adoption of hybrid systems that combine several technologies, such as wind and solar photovoltaic energies, wind and thermal energies, or gas and wind plants. Three studies appear. The evaluation of the impact of regulatory policies on wind energy projects, seeks to assess the uncertainty caused by the expectation of retroactive changes in wind energy policy, and the flexibilities associated with changing tariffs or subsidies, regulatory frameworks, support schemes such as feed rates and renewable energy certificate trading, and future renewable energy policy. There are nine publications. The evaluation of wind energy systems, considers the investment required to adopt energy systems integrated by wind energy and hydraulic storage by pumping, or photovoltaic systems, and to expand the network by investing in stages, generating flexibility for the planning of the electrical system. There are three publications. The evaluation of wind resources integrates studies of wind energy projects planning, considering real options for the evaluation of said resources. There is one publication. Finally, there are studies aimed at evaluating the design, size, and location of wind farm projects to allow for optimal investment. There are two publications. 1.1 Analysis by Group According to Their Application Purposes Evaluation of Wind Energy Generation Project or Investment Uncertainties  
For the evaluation of wind energy generation projects or investment, uncertainties such as electricity load, energy sales, or energy production [77; 99; 123; 125]; climatic variables or wind conditions [75; 99; 106; 117; 125], the price of electricity [31; 72; 99; 117; 123; 124; 125], carbon price, or other incentives [75; 106; 124], have been considered. Others have explored  
Figure 3: Purpose of the study. things such as market conditions, investment planning, investment costs, capital, or other costs [77; 99; 119], government policies, and technology levels [75], as uncertainties. Techniques to Model Uncertainties  
To model uncertainties, stochastic processes of the geometric Brownian Movement type-GBM [56; 75; 106; 119; 125], the binomial model of [PERSON], [PERSON], and [PERSON] [124], reversal of the mean [31; 72; 123], normal distribution [31], Weibull distribution [77; 123], and Box-Jenkins and Ornstein-Uhlenbeck [99; 100], have been used. The options that have been used during the evaluation are the option of expansion or closure of facilities [117; 124], invest now, postpone, or abandon [72; 75; 99; 123], or the option to switch between alternatives, either capacity [125], or investment [72]. Techniques to Evaluate Used Options  
Techniques such as Black-Scholes [119; 125], decision trees [106; 117; 123; 124], the binomial model of [PERSON], [PERSON], and [PERSON] [124], Monte Carlo simulations [56; 75; 106; 117; 123; 124], the Wiener process [31], Dynamic programming [56], Monte Carlo (least squares) [99; 100], and optimization algorithm [77]. Evaluation of Energy Auctions, Portfolios, and Energy Market Investments  
Uncertainties  
For the evaluation of energy auctions, portfolios, and energy market investments, one can find energy production [122], electricity price [58; 108; 122], capital or investment costs [108; 122], future deployment of offshore wind energy [86], and electricity demand [58] being considered as uncertainties.