## 2 Applications of ANNs to Renewable Energies
### Applications of ANNs for Wave Prediction  
Tidal energy, like other renewable energies, is fundamental to achieving the European climate targets for 2030 and 2050. Recently, the use of NNs for wave height (H) and period prediction has gained importance. ANNs have also been applied in different fields of ocean, coastal, and environmental engineering [118]. The following table summarizes the main research pieces found when performing the review. The studies have been classified according to the ANN structure, journal and region, input and outputs for the network, and the activation function employed. The following Table 3 shows the H predictions. Figure 4: Inputs and outputs in ANNs applied to solar energy systems. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Authors** & **ANN Type** & **Journal** & **County/** & \multicolumn{2}{c}{**IVO Setting**} & \multicolumn{2}{c}{**Activation Function**} & \multicolumn{1}{c}{**Notes**} \\  & **and Year** & **and Structure** & **Region** & **Inspent** & **Outspot** & & & & \\ \hline \multirow{2}{*}{9} & \multirow{2}{*}{[127]} & MLP & Occum & \multirow{2}{*}{[128]} & \multirow{2}{*}{[129]} & \multirow{2}{*}{[130]} & \multirow{2}{*}{[131]} & \multirow{2}{*}{[132]} & \multirow{2}{*}{[133]} & \multirow{2}{*}{[134]} & \multirow{2}{*}{[135]} & \multirow{2}{*}{[136]} \\  & & & & & & & & \\  & & & & & & & & \\ \hline \multirow{2}{*}{10} & \multirow{2}{*}{[128]} & MLP & \multirow{2}{*}{[129]} & \multirow{2}{*}{[130]} & \multirow{2}{*}{[131]} & \multirow{2}{*}{[132]} & \multirow{2}{*}{[133]} & \multirow{2}{*}{[133]} & \multirow{2}{*}{[134]} \\  & & & & & & & \\ \multirow{2}{*}{} & & & & & & & \\  & & & & & & & \\ \hline \multirow{2}{*}{11} & \multirow{2}{*}{[131]} & MLP & \multirow{2}{*}{[132]} & \multirow{2}{*}{[133]} & \multirow{2}{*}{[134]} & \multirow{2}{*}{[135]} & \multirow{2}{*}{[136]} & \multirow{2}{*}{[137]} & \multirow{2}{*}{[138]} \\  & & & & & & & \\  & & & & & & & \\ \hline \multirow{2}{*}{12} & \multirow{2}{*}{[133]} & MLP & \multirow{2}{*}{[131]} & \multirow{2}{*}{[132]} & \multirow{2}{*}{[133]} & \multirow{2}{*}{[134]} & \multirow{2}{*}{[135]} & \multirow{2}{*}{[136]} \\  & & & & & & & \\  & & & & & & & \\  & & & & & & & \\ \hline \multirow{2}{*}{13} & \multirow{2}{*}{[13  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **Authors** & **ANN Type** & **Journal** & **County/ Region** & \multicolumn{2}{c}{**IVO Setting**} & \multicolumn{2}{c}{**Activation Function**} & \multicolumn{1}{c}{**Notes**} \\ \cline{1-1} \cline{6-10}  & **and Year** & **and Structure** & & & & **Inget** & **Output** & & & \\ \hline \multirow{4}{*}{16} & \multirow{4}{*}{[134]} & MLP & & & & Significant wave height (\(\lambda_{1/2}\)), & & & & \\  & & 8-4-1 & Ocean & & highest energy (\(\lambda_{1/2}\)), & & & & \\  & MLP & Engineering & & & (H\({}_{1/3}\)), highest wave height & H\({}_{1/3}\) & sigmoid & & Trained by BP \\  & & 2-2-1 & & & (H\({}_{1/3}\)), mean wave height & (station C) & (output layer) & & & \\  & & 2-2-1 & & & (H\({}_{1/3}\)) & & & & \\  & & & & ( stations A and B) & & & & & \\ \hline \multirow{4}{*}{17} & \multirow{4}{*}{[135]} & MLP & & & & & & Trained by BP \\  & & 2-5-1 & & & & & & algorithm \\ \cline{1-1} \cline{6-10}  & & & & & & & & & \\ \cline{1-1} \cline{6-10}  & & & & & & & & & \\ \cline{1-1} \cline{6-10}  & & & & & & & & & \\ \cline{1-1} \cline{6-10}  & & & & & & & & & \\ \hline \multirow{4}{*}{18} & \multirow{4}{*}{[136]} & ANN & & & & & & & \\ \cline{1-1} \cline{6-10}  & ANN & & & & & & & & \\ \cline{1-1} \cline{6-10  
While it is true that studies appear in the literature since 2001, unlike the two previous cases, there has been an increase in the number of studies carried out in recent years. Most of the research is concentrated in India, Canada, and the United States and applies to both lakes and the open sea. The main characteristics of the networks studied are detailed below. * ANN type: as in previous cases, the MLP has been the structure chosen by most researchers (17 out of 20 cases).