2.2.3. Economic Criteria

Economic criteria affect the construction and operation costs of wave power plants. They include distance from the shore, distance from the port, and population served. Distance from the shore and distance from the port are cost criteria, and population served is a benefit criterion. Distance from the shore is related to operation and maintenance costs; being far from the shore increases the cost of maintaining wave energy generation devices [32–34]. Distance from the port affects construction and installation costs; areas close to ports are better for constructing wave power plants because the related costs will be comparatively low [32,33,35,36]. Population served refers to the population of the island served by the wave power plant [32]. It reflects the number of potential energy consumers; the larger the population served, the more urgent the power demand of the island.

#### 2.2.4. Social/Environmental Criteria

Wave power plants may affect social benefits and environmental conditions around islands. Social/environmental criteria include fishing potential, tourism potential, shipping density, policy encouragement, and electricity demand. Fishing potential, tourism potential, and shipping density are cost criteria; policy encouragement and electricity demand are benefit criteria. Areas with high fishing potential and tourism potential are less suitable for wave energy development. Constructing wave power plants in areas with good fishing potential will affect the normal economic activities of island residents [36,54] Meanwhile, wave-energy-generation devices also cause visual and noise disturbances for tourists, which will affect the economic benefits of local tourism [30,55,56]. The deployment of wave-energy-generation devices should not disturb primary shipping routes since the probability of collision with the devices will increase [30,32,33,36]. Policy encouragement is important for achieving a successful, long-lasting wave power plant since a reliable institutional policy framework can promote constructing wave power plants [47,57,58]. The island population, infrastructure construction, distance from the shore, and current energy supply situation determine the island's power demand [59–61]. The greater the demand for power, the more urgent the need for construction.

After quantifying the above qualitative criteria through reclassification, vector normalization (VN) is further employed to normalize all criteria values. The purpose of normalization is to eliminate differences between attributes in dimensionality and order of magnitude. Normalization can affect the decision result by affecting the diversity of attribute data (DAD) [62]. VN does not change DAD and is considered to be the best normalization method for TOPSIS. The formula for VN is

$$\mathbf{x}\_{ij}^{\*} = \frac{\mathbf{x}\_{ij}}{\sqrt{\sum\_{i=1}^{m} \mathbf{x}\_{ij}^{2}}}, (i = 1, \dots, m, \ j = 1, \dots, n). \tag{1}$$

where *xij* represents the attribute value of *i*th alternative against *j*th criterion, *x*<sup>∗</sup> *ij* represents the normalized attribute value, *m* represents the number of alternatives, and *n* represents the number of criteria.

#### **3. Methodology**
