2.1.2. Wave Power Density

Wave power density (WPD) is an important technical criterion for evaluating wave energy resources considering both wave height and wave period. As an exclusion criterion, the lowest WPD value should meet the technical feasibility requirements of wave-energygeneration devices.

#### 2.1.3. Water Depth

For economic and technical reasons, water depth (WD) imposes many space restrictions on wave power plants site selection. The type and installation method of wave energy generation devices and cost-related issues (e.g., wiring, operating, and maintenance costs) are all affected by WD [49,50].

#### *2.2. Evaluation Criteria*

To determine the preference order of islands, 14 evaluation criteria related to resource, natural, economic, social and environmental factors are identified to evaluate island alternatives. Table 1 presents the classifications of evaluation criteria.


**Table 1.** Evaluation criteria.

#### 2.2.1. Resource Criteria

Resource conditions are critical for the economic viability and technical feasibility of wave power plants. WPD and wave height are both benefit criteria, and they are important resource criteria for wave energy resource evaluation [32–36]. These two criteria are used to describe how much wave energy is available for wave-energy generation at a site. The greater the WPD and wave height, the more suitable it is for wave energy development.

#### 2.2.2. Natural Criteria

Natural criteria affect the construction and operation of wave power plants for islands, including WD, seabed geology, coastal erosion, and geological disaster. Seabed geology is a benefit criterion, while WD, coastal erosion, and geological disaster are cost criteria. WD limits the type and placement of wave energy generation devices. Installing wave energy generation devices in areas with a large WD will increase foundation costs and technical difficulties [30,32,33]. Seabed geology affects the installation of energy generation devices and submarine cables [49,51,52]. It is very valuable for selecting a suitable seabed geology for installing wave energy generation devices. After that, a developer can determine the appropriate slope, installation location, and connection route to the coast for installation. Coastal erosion indicates the soil erosion of a near-shore beach zone [30,52,53]. Installing wave energy generation devices around areas with severe coastal erosion will increase the difficulty of construction and reduce the stability of power generation. Geological disaster refers to the frequency of geological disasters around the island; areas with a high frequency of geological disaster are not suitable for constructing wave-energy power plants [52].
