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1. Introduction to Solar Photovoltaic Land Suitability 63

could incorporate map algebra analysis and availability in several GIS software’s
(such as IDRISI, ILWIS, and ArcGIS) [61].
Ideal point methods order the decision alternatives based on their separations
from some reference point. The chosen alternative should have the shortest distance
from the Positive Ideal Solution and the farthest from the Negative Ideal Solution.
The final ranking is obtained using the closeness index [14]. The most popular
GIS-based ideal point method is the TOPSIS. Sa ´nchez et al. [14] has reduced the
studied area by applying restrictive criteria to discard unsuitable areas for solar
farms projects. AHP considered weighting criteria and TOPSIS approach applied
for alternative assessment according to their degree of adequacy. Sa ´nchez et al.
[69] applied AHP model to acquire weights of the criteria and the alternative assess-
ment completed by fuzzy TOPSIS method for the installation of solar thermoelectric
power plants.
Outranking Methods are based on pairwise comparison of alternatives on each
decision criteria. The major procedure of this approach is applying the concordance
and discordance measures. The concordance measure is based on concordance set
for which the ith alternative is not worse than the competing alternative j, on subset
of all criteria while the discordance is based on the discordance set for which alter-
native, i, is worse than the competing alternative, j [61]. The goal of outranking ap-
proaches is to find an alternative that dominate other alternatives while it cannot be
dominated by any other alternative. Outranking also requires knowing weights of the
criteria to find the best alternative [70]. There are a several formulas existed to calcu-
late the overall score for each alternative based on concordance and discordance
measures. The most widely outranking techniques integrated with GIS are the
ELECTRE and preference ranking organization method for enrichment evaluation
(PROMETHEE) [61]. Jun et al. evaluated seven wind/solar hybrid power stations,
weight the indicators by and evaluates these seven regions via ELECTRE [20].
Sa ´nchez et al. [19] integrated ELECTRE with GIS to optimize the solar farms loca-
tions according to multiple evaluations criteria. The restricted area excluded using
GIS and criteria applied to categorize the potential plots using decision support sys-
tem. Instead of finding the best suitable site to implement solar farms, the potential
locations classified into distinct categories according to multiple evaluation aspects.
Fuzzy Methods is the description of a set of objects that have not shown sharply
defined boundaries, and such imprecisely defined sets of objects are called fuzzy sets
[71]. The fuzzy criteria and fuzzy constraints are combined to generate a decision
where the best alternative is the one with highest grade membership value. In a
particular subset þ of the universe of discourse X, the grade of membership is
defined by the membership function mM(x). The function represents any elements
x of X partially belonging to M, or the grade of membership of x in M. An object’s
membership value, which shows the degree to which it belongs to a set, can be any
number between one and zero. If mM(x) ¼ 1 that indicate element x obviously be-
longs to M whereas if mM(x) ¼ 0 it indicates x not belong to M. The element of
higher membership value represents more belong to the set [61]. The fuzzy
MCDM has two essential terms: fuzzy number which is a set of real number and