Sustainable development is described as “the organizing principle for the achievement of human development objectives while at the same time preserving the capacity of natural systems to provide the natural resources and ecological services on which the economy and community rely” [1]. Sustainable development often implies “a development that addresses current needs without influencing potential generations’ capacity to fulfill their own needs” [2,3].

In 1979 René Passet proposed a three-sphere framework for sustainable development projects [4] (Figure 1) According to this framework, development can be considered as sustainable only if it simultaneously has positive social, environmental, and economic impacts. If a project satisfies the economic and social aspects but fails to satisfy the environmental aspects, it is categorized as equitable. If a development project can satisfy the environmental aspects but fails one of the social or economic aspects, the development could still be bearable or viable, respectively. If a development cannot satisfy at least two of the three mentioned aspects, it cannot be categorized anywhere in this definition. Some authors consider a fourth sustainability pillar of culture, institutions, or governance [5], or reconfigure the four domains to be social-ecology, economics, politics, and culture [6]. Overall, the focus of the modern sustainable development concept is simultaneous economic development, social progress, and environmental protection for current and future generations [7].

 

Renewable energy is defined as energy that is obtained from resources that are fully replenished on a human time scale [9]. According to REN21’s year 2019 report, renewable resources provided 2378 GW of power capacity, which is more than 33% of the world’s total electrical generating capacity. In this list, hydropower capacity (excluding pure pumped storage capacity) is 1132 GW, which is about half of total renewable energy. It is worth mentioning that in 2018, annual new investment in hydropower grew 11% in comparison to the previous year [10]. The majority of hydropower investment is in large dams and associated generating stations that inherently include complex networks of social, economic, and ecological effects, maybe more than any other large infrastructure project [11].

 

Hydropower is one of the most efficient and confident sources of renewable energy [12] and has considerable value for a sustainable future [13]. By the end of 1999, around 2650 Terawatt hours (TWh) (19%) of the world’s total electricity relied on hydropower [14]. It rose to about 3100 TWh until 2009, and it is estimated that it reaches to 3606 TWh in 2020 [15]. Dams are essential tools for controlling, storing, managing, and operating water for humankind. Large dams serve various specific purposes for our civilization, including water supply, flood control, navigation, sedimentation control, and hydropower [16]. However, they also come with disadvantages, including flooding large areas of land, impeding fish migration, and affecting the physical characteristics of the dam’s downstream river [17]. Construction of large dams needs significant capital, so many large dam projects are national (or even international) in scope. Currently, most new large dams are being constructed to provide combinations of energy, irrigation, and flood control in developing countries. At the same time, dam decommissioning is an increasing trend in developed countries because of environmental impacts and the economic costs of maintaining aging structures [11].

Hydropower plants can be classified based on their installed electrical generating capacity. Typical categories and associated capacities are: large hydro (>10 MW), small hydro (<10 MW), mini-hydro (<1 MW), micro-hydro (<100 kW), and pico-hydro (<5 kW) [18]. It is estimated that about 10% of global hydropower is generated from powerplants with less than 10 MW of capacity [18]. Micro-hydro plants often utilize the natural flow of water in a run-of-river (ROR) configuration [19]. ROR plants include little or no controlled water storage, meaning that ROR typically has small or no reservoirs. The lack of a large reservoir formed by a dam, or significant control of river flow, avoids or minimizes the disadvantages associated with large reservoirs, at a cost of having to accept more variable or poorly timed power generation.

Micro hydropower plants can often be considered as a sustainable development option for generating electricity in both developing and developed countries. There is often no need to build expensive dams and flood massive areas for the reservoir. This minimizes land and soil destruction, threats to wildlife, climate change effects, and other environmental impacts, especially on ecosystems [20] as well as the social impacts of ROR hydropower plants. New ROR hydropower technologies such as Archimedes Screws Turbines (ASTs) can be particularly advantageous in these regards.

 

The Archimedes screw is considered to be one of the earliest hydraulic machines [21]. It is composed of a helical array of simple blades that are wrapped around a central cylinder, like a woodscrew [22]. This screw is supported within a surrounding fixed trough. There is a small gap between the trough and screw that allows the screw to rotate freely while allowing only a small amount of water to leak past the blade edges. It is believed that the Archimedes screw was invented by Archimedes of Syracuse (circa 287-212 BCE), the Greek physicist, mathematician, and inventor [23]. However, there is evidence suggesting the invention and use of the screw technology may date back to over three centuries before Archimedes under the reign of King Sennacherib (704-681 BCE) in the 7th century BCE in the Assyrian Empire [24].