2.1 Sustainability2.1.1 ConceptSustainability means the potential to achieve sustainable development. Generally, it is development aimed at meeting current needs without having a bad influence on the ability of future generations to meet their needs. It mainly covers two concepts: The notion of “needs” refers specifically to the basic needs of the poor. Second, “limits” refer to the capacity of technology and social organization to meet current and future environmental needs. (Source: Brundtland Report of 1987) 2.1.2 Reasons for sustainable development The demand for energy in the industrial and residential aspect is increasing due to the growth of the world population. As shown in the figure, the energy consumption rate increases rapidly despite limited energy. This strains the environment and deficient fossil resources. All the resources in the world are obviously insufficient. According to BBC News, two thirds of the world's population could live in areas of severe water scarcity by 2025 (Kirby, 2004). Additionally, Kirby noted that I...