## 2 Literature Review  
### Active Design Based on Solar Panel System for Energy-Efficient Architecture  
The photovoltaic effect, which generates energy from sunlight, was first introduced by the French physicist [PERSON] in 1839. Solar cells were first used as an energy source when they were deployed as a power source for communication networks in Americas, Georgia in 1955 [14; 15]. Solar panels were first applied in the architectural field by American architects and engineers just before World War II up to the late 1950s. After the war, as concerns about energy supply and global environmental problems emerged, interest in the development of ecorfriendly architectures that utilize solar energy increased. However, as oil energy was used as the main energy source at the time, interest in solar energy decreased, whereas interest in renewable energy increased again following the oil crisis of the 1970s [16]. Today, solar-energy-based active designs are being applied to various buildings because of the global interest in low carbon emissions and energy savings in all industrial fields.  
The methods for utilizing solar energy in the construction sector can be broadly divided into two types. First, some buildings produce electrical energy from solar energy. This method involves installing a solar power generation system in a building. Solar cells are installed on the roofs of buildings to convert the natural energy of sunlight into electrical energy. Second, some buildings produce heat energy from solar energy. Solar collectors are installed on the roofs of buildings to produce energy for heating water [17; 18].  
Solar panels installed in buildings are placed on the rooftops of the buildings to expose the solar panels fully to sunlight and facilitate their maintenance. Building-integrated photovoltaics (BIPVs) are widely used to install solar panels on sloped roofs and building facades rather than on flat roofs [19]. Before applying BIPVs, the selection of the optimal solar panel location and various climatic conditions are considered to increase the energy production efficiency [20]. Once the location of the solar panel is selected, the panel is attached to the exterior wall of the building, and such an integration changes the building's envelope from an energy consumer to an energy producer. Solid-based active building envelopes are systems in which solar panels are integrated into the building roof and exterior walls. Currently, owing to the development of solar panel materials, solid-based active building envelopes are applied not only to opaque building shells but also to transparent windows [21]. Semitransparent solar panels have been inserted into double-glazed windows to maximize the amount of renewable energy produced by building envelopes [22; 23; 24]. In particular, the active energy facade system installed on the southern vertical surface of a building facade maximizes the energy production efficiency through the attachment of solar panels to moveable louvers installed to control the solar influx [25; 26]. Solar-panel-integrated louvers with fluid properties have the potential to be applied to the exterior of a building and used as a design element for creative facades and to produce renewable energy. Research related to the kinetic facade system installed on the exterior wall of a building aims to use technology to increase the energy efficiency of buildings through architectural design. Investigations have been conducted on kinetic facades based on geometric patterns inspired by traditional architectural designs in the Middle East [27]. In addition, researchers have developed a kinetic biomimetic system in which plants respond to light as a kinetic facade [28]. Glass facades of various colors with different geometric shapes and a kinetic facade abstracting a biomimetic system were developed on a building facade. These studies aimed to improve daylight performance within the building space using the developed kinetic facade. Daylight performance was measured in a virtual space via parametric simulations.