Can solar desalination be small and beautiful? A critical review of existing technology under the appropriate technology paradigm

Many territories have limited access to fresh water, so there is an urgent need to develop technologies to purify the available water resources. Some of these territories share geographical and social characteristics that allow them to be analyzed as a whole. As a result, the suitability of different desalination technologies for a given context can be assessed. For example, many territories lacking access to fresh water share access to saline water resources, high levels of solar radiation and a precarious economic situation. If appropriate technologies are defined as decentralized, labor-intensive, energy-efficient, environmentally friendly and locally autonomous solutions developed for a given context, there is a strong need to develop and promote appropriate technologies that are adapted to these conditions. This paper evaluates the available technologies for indirect concentrating solar desalination under the appropriate technology paradigm. For this purpose, these systems are divided into three subsystems: desalination itself, solar supply and by-product treatment. Each is explored in terms of its qualification as appropriate technology, which is defined by the degree to which it meets a series of 10 attributes. A specific literature review has been conducted to present and analyze potential technologies for each subsystem, which have been evaluated as appropriate technology through an evaluation matrix. The analysis of the candidate technologies and their attributes is carried out for each of the three subsystems using the Formal Conceptual Analysis method. The analysis shows that humidification-dehumidification desalination systems combined with Fresnel line collector systems are the most promising option to meet the requirements of appropriate technology. To minimize the environmental impact, evaporation ponds are considered the best option for brine treatment. Finally, it should be noted that the methodology developed has proven to be a very suitable tool for the critical evaluation of technologies and serves as a first step to group and relate different alternatives by means of a deterministic set of attributes.