## 4 Design
### Energy Generation Simulation of Kinetic Photovoltaic Facade System  
To measure the amount of renewable energy generated from the facade of a car park building, a photovoltaic system designed for energy optimization was implemented in a virtual three-dimensional space. The specific photovoltaic energy simulation process is as follows: first, the building and photovoltaics were placed using Revit software to construct a physical building environment. Second, we built an algorithm to implement a moving photovoltaic system using Dynamo, a plug-in program for Revit software. The algorithm designed with Dynamo is based on a constraint-based system, which creates a final structure by applying different constraints to the elements comprising the building. The algorithm was designed to adjust the photovoltaic by inputting the optimal tilt angle monthly on the south, east, and west facades of the car park building. Third, we measured the amount of renewable energy generated on the three sides of the building. To conduct a solar-energy-based energy generation simulation, we utilized Insight, a plug-in program for Revit software. A virtual space environment was established to run the energy generation simulation. The study location was Seoul, and the research environment was set for the period from January to December 2023. The period for which the photovoltaics were exposed to sunlight was set from 6 AM to 8 PM. Figure 7 shows an example of a simulation of energy generation from kinetic photovoltaics attached to the facade of a car park building in March 2023. The energy generation simulation results for March 2023 show that the building facades with the highest energy production were south-facing, west-facing, and east-facing, in that order.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Month**} & **East Facade** & **West Facade** \\ \cline{2-3}  & \(\alpha\) & \(\alpha\) \\ \hline January & 20\({}^{\circ}\) & 30\({}^{\circ}\) \\ February & 30\({}^{\circ}\) & 30\({}^{\circ}\) \\ March & 30\({}^{\circ}\) & 40\({}^{\circ}\) \\ April & 50\({}^{\circ}\) & 60\({}^{\circ}\) \\ May & 60\({}^{\circ}\) & 70\({}^{\circ}\) \\ June & 60\({}^{\circ}\) & 70\({}^{\circ}\) \\ July & 60\({}^{\circ}\) & 70\({}^{\circ}\) \\ August & 50\({}^{\circ}\) & 60\({}^{\circ}\) \\ September & 40\({}^{\circ}\) & 50\({}^{\circ}\) \\ October & 30\({}^{\circ}\) & 40\({}^{\circ}\) \\ November & 30\({}^{\circ}\) & 40\({}^{\circ}\) \\ December & 30\({}^{\circ}\) & 30\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: South-facing tilt angle (\(\alpha\)) for optimizing renewable energy generation for photovoltaics in the east and west.  
Figure 6: Dynamo algorithm for the parametric design of kinetic photovoltaic facades. Example of applying the optimal angle of 38.3\({}^{\circ}\) for the photovoltaic facade in March to the “PV Cell 1” model.  
A simulation of solar energy generation using BIM was conducted for a car park building in Seoul for one year, from January to December 2023. As a result, 692,386 kWh-year\({}^{-1}\) of energy was generated from a photovoltaic area of 2034 m\({}^{2}\). The energy generation efficiency was lowest in July (25,856 kWh-month\({}^{-1}\)) and highest in March (83,348 kWh-month\({}^{-1}\)) (Table 3).