Solar Desalination Technologies Research Articles

The AQUASOL System: Solar Collector Field Efficiency and Solar-Only Mode Performance

Water scarcity is a global problem that will be of capital importance during the first half of this century, when seawater desalination will often be the only way to achieve sustainable development. Despite significant energy efficiency improvements during recent years, seawater desalination is still an intensive energy consumer; therefore, in the current instability of oil prices and environmental requirements, the sustainability of this technological solution inevitably passes through continued improvement of energy efficiency of the physical processes involved, as well as the use of renewable energy resources such as solar energy. In 2006, the “Enhanced Zero Discharge Seawater Desalination Using Hybrid Solar Technology” Project (AQUASOL) concluded with the erection of a complete solar desalination facility at the Plataforma Solar de Almeria (Spain) for the main purpose of developing an improved-cost, energy-efficient multi-effect distillation (MED) solar desalination technology. The system was designed to make the following three desalination operating modes feasible: (a) solar-only: the energy to the first distillation effect comes exclusively from thermal energy from the solar collector field, (b) fossil-only: a double-effect absorption heat pump powered by gas supplies all of the heat required by the distillation plant, and (c) hybrid: the energy comes from both the heat pump and the solar field. In this paper, solar-only mode system performance is presented and discussed. Optimum working conditions achieved in the solar-only mode were in the range of 64–67°C of MED first cell inlet temperature, which implies specific thermal energy consumption from around 58 kW hth/m3 to 62 kW hth/m3 and a performance ratio of 11.1–10.4, respectively.

Selection and economical evaluation of solar desalination technologies via DesalSolar software

Worldwide projection indicated that in 2020 the situation of water resources in Iran reach to scarcity. Besides, global warming and energy crisis have forced countries to use renewable energy resources. Solar desalination technologies particularly in remote area of Iran could be a method to emancipate from this crisis. In this paper, all kind of desalination technologies were reviewed. Then, Niroo Research Institute (NRI) solar radiation model considered for choosing most potential regions. The radiation map indicated that south part of Iran with annual average daily global irradiation 5.6 kWh/m 2 had inherent potential for applying solar desalination. Finally, selection and techno-economic evaluation of desalination technologies was performed in capacities from 1 m 3 /day to 100 m 3 /day under four South’s Iran cities by applying DesalSolar simulation software. The result of investigation demonstrated that in all cases, reverse osmosis coupled to Photovoltaic system had best performance in terms of energy consumption, cost, and other criteria which was considered in assumption.

Desalination coupled with salinity-gradient solar ponds

Thermal desalination by salinity-gradient solar ponds (SGSP) is one of the most promising solar desalination technologies. Solar ponds combine solar energy collection with long-term storage and can provide reliable thermal energy at temperature ranges from 50 to 90°C. Solar-pond-powered desalination has been studied since 1987 at the El Paso Solar Pond Project, El Paso, Texas. From 1987 to 1992, the search mainly focused on the technical feasibility of thermal desalination coupled with solar ponds. Since 1999, the research has focused on long-term reliability, improvement of thermodynamic efficiency, and economics. During this period, a small multi-effect, multi-stage flash distillation (MEMS) unit, a membrane distillation unit, and a brine concentration and recovery system (BCRS) were tested over a broad range of operating conditions. The most important variables for the MEMS operation were flash range, concentration level of reject brine, and circulation rate of the first effect. The brine concentration and recovery system is part of the goal of developing a systems approach combining salinity-gradient solar pond technology with multiple process desalination and brine concentration. This system approach, called zero discharge desalination, proposes concentrating brine reject streams down to near NaCl saturated solutions and using the solution to make additional solar ponds. In addition to presenting the test results on the MEMS and BCRS units, this paper also presents a summary of solar pond operation experiences obtained from the 16-year operation at the El-Paso solar pond.

The analysis and performance of large-scale stand-alone solar desalination plants

The development of a simple dynamic computer model allows the performance and operational behavior investigation of a large solar seawater desalination system based on a multi-effect distillation plant and a solar pond, which is believed to be the most promising large-scale solar desalination technology known today. The whole system of dynamic behavior of the whole system is investigated, and annual water yield predictions are made during the thermal transient build-up and quasi-steady-state system operation. The effect of various design and operational parameters on system behavior are investigated. Results are offered for system sizing, design and water yield predictions, as well as system economic evaluation. Based on up-to-date construction experience, rates and market costs of components and labor, as well as updated costs of commercially available desalination plants, predictions of the unit water cost are made according to which appears to be most competitive with water cost from conventional resources in several arid and semi-arid geographical locations.

Technical and economical aspects of solar desalination with particular emphasis on solar pond powered distillation plants

Desalination remains an important and interesting application for the use of solar radiation as a source of undepletable energy. After almost a decade of research and development including the installation and testing of various smaller pilot systems, our solar desalination technology - among others - is now becoming available on a commercial level. The paper discusses the evolution of the technology both of the desalination and the collector-subsystems as a result of the technical and economical constraints associated with the utilization of solar energy, a highly fluctuating energy source of low surface density. Performance data is presented in particular for the coupling of a selfregulating MSF unit with a solar pond energy collection and storage system, both inhouse developments. The performance and layout data was obtained both from computer simulation and experimental results with a small sized solar pond and desalination subsystem in Switzerland. The economy assessment, which is presented for Middle East climate conditions, clearly demonstrates that solar desalination already becomes competitive for medium sized installation at remote locations. Potential further cost reductions also through upscaling may lead to the use of desalinated water for agricultural applications one day.

Design and operation experience with solar powered multistage desalination plants

Desalination is a favourable application for solar energy and has a good potential for economic viability, since water demand is a consequence of abundant solar irradiation (no long term storage needed) and only low temperatures are necessary for the required thermal energy (simplicity of solar collector system). An R + D partnership for the development and implementation of solar desalination technology has been set up between the Swiss Federal Institute of Technology (fundamental development and laboratory testing), Atlantis Energy Ltd. (hardware design, construction and delivery) and the Kuwait Institute for Scientific Research (field testing). A 3-phase-program is under way: 1. Phase 1 (completed): Initial construction of a conventional MSF plant, laboratory and field tests. Design criteria for solar equipment resulted such as capability of operation under heavily fluctuating energy input conditions, minimisation of mechanical energy consumption, simplicity of equipment, etc. 2. Phase 2 (completed): Design of a new “real solar” MSF-unit, meeting the above requirements, laboratory testing, field testing in Kuwait. 3. Phase 3 (under way): Upscaling of the pilot plant to commercial sizes of 100 to 1000 m 3/day, optimization of the process, realisation of a demonstration plant, coupled to a salt solar pond, specially developed for this purpose. It can be concluded, that solar desalination has been demonstrated to be a reliable method of obtaining drinking water when using a specially developed salt solar pond system as heat source, water at lower prices is obtained compared with that from an oil-fired evaporator.