*2.1. Geometry of a Floating Solar Power Farm*

In general, an FSP consists of a floating body, a frame bar that supports the floating body, and a solar panel. In this study, the FSP components for the model test were designed as shown in Figure 1. The floating body has a length, breadth, and depth of 0.12 m, 0.105 m, and 0.12 m, respectively.

**Figure 1.** Geometry of a floating solar power farm used in the experiment: (**a**) floating body; (**b**) unit; (**c**) block.

The unit consists of nine floating bodies. These were designed as cuboids for convenient production. To understand the relative behavior between units under wave conditions, two-row and two-column matrix forms were combined and called a block. Table 1 lists the specifications of the FSP components. In addition, a uniaxial hinge system with a length of 50 mm was constructed so that relative behavior between units could be investigated. The position of the connector was installed on the parallel line where the frame bars were located. Figure 2 shows the overall geometry of the model tested in this study.



**Figure 2.** Schematic of the floating solar power farm in the experiment.

*2.2. Experimental Setup and Procedure*

The experiment in this study was conducted in the IUTT (see Figure 3). The IUTT consists of a wave maker that can generate a maximum wavelength of 2.0 m and wave height of 0.2 m; a wave absorber; and a concrete tank that has a length, breadth, and depth

of 50 m, 3.5 m, and 1.5 m, respectively. The breadth of the FSP at the waterline is about 1.1806 m (see Figure 2). The model size was selected to minimize the effect of blockage.

**Figure 3.** The towing tank in Inha University.

The movement of the FSP was extracted as time-series data using a camera (OptiTrack Prime X13, Motion Technologies, Inc., Seoul, Republic of Korea) considering its high frequency, accuracy, and convenient installation. Four cameras were used in this study to capture motion based on the principle that infrared light emitted from a camera is reflected by a marker and sensed by the camera. The camera tracks the marker with positional errors less than ± 0.2 mm and rotational errors less than 0.5◦. To keep the position of the FSP, weights and wires were used as anchors and mooring lines. The 7 × 7 stainless-steel wires had a diameter of 1.2 mm, an axial stiffness of 565.2 N/m, and a weight of 0.0063 kg/m. The mooring line connection in the FSP was placed in the center of the frame bar connection the floating bodies. The anchor was fixed at a parallel position 1.5 m away from those positions, and the length of the mooring line was set to 1.9 m.

In general, the mooring system of the FSP is a taut spread to restrain its motion. However, since the water depth could be changed according to the tide condition, the mooring system in this study was assumed to be a catenary mooring considering a loosened state at low tide.

A one-component force meter has been manufactured to measure tension up to 50 N with a linearity, hysteresis, and reproducibility of 0.7%, −0.4%, and 0.6%, respectively. A tension gauge was installed on the upstream mooring lines of the FSP.

As shown in Table 2, the experimental conditions were selected within the range that can be experimented with using the IUTT. *Lunit* refers to the waterline length of a unit in the *x*-direction. Two incident wave angles (139◦, 180◦), two wave steepnesses (*H*/*λ* = 0.03, 0.05), and wavelength ratios (*λ*/*Lunit* = 1.6–3.2) were considered in the experiment. Here, *λ* is the wavelength and *H* is the wave height. Only regular waves were used.

Schematic diagrams of the model test of the FSP under wave conditions are shown in Figures 4 and 5. The direction of wave travel, direction from the FSP toward its right, and direction opposite to that of gravity were set as the positive *x*-, *y*-, and *z*-directions. An ultrasonic wave height meter was installed 2.0 *Lunit* in front of the FSP to ensure the reliability of the waves generated by real-time wave height information. The first and second rows were defined as the first and second groups, respectively. The experimental setup of the test model of the FSP under wave conditions is shown in Figure 6.


**Table 2.** Test conditions of the experiment.

**Figure 4.** Diagram of the experimental setup for head sea conditions.

**Figure 5.** Diagram of the experimental setup for oblique sea conditions.

**Figure 6.** Experimental setup: (**a**) head sea conditions; (**b**) oblique sea condition.
