Energy Consumption and Water Production Costs of Desalination Technologies in PLN

Energy consumption and water production cost of conventional and renewable-energy-powered desalination processes

Systematic Analysis Reveals Thermal Separations Are Not Necessarily Most Energy Intensive

Desalination is probably the only means for fresh water supply to countries in decertified climate. The majority of GCC counties rely on desalinated water for fresh water supply to major cities. Over 70% of the desalinated water in the GCC comes from thermal desalination plants including Multi Stage Flash (MSF) and Multi Effect Distillation (MED). The new trend in the desalination plant in the GCC is 30% Reverse Osmosis (RO) and 70% thermal. However, these percentages vary from one to another country depending on feed water quality and expertise. For example, Oman Sea has lower salinity than the Gulf water and hence Oman uses more RO for desalination than MED and MSF. This decision is also driven by economy as RO process less energy intensive and hence the produced water is less expensive as compared to thermal plants. On the contrary, Qatar and Kuwait use more MSF followed by MED due to the high salinity and low quality feed water. This is also because trials of RO in both Qatar and Kuwait were not successful because of the problems of membrane fouling and restrict pre-treatment requirements due to the quality of the water intake.The advantages of RO over thermal technologies are well known in terms of lower energy consumption and the cost of produced water; but are not yet taken advantage of in the GCC zone. One of the reasons is blamed on high feed water salinity and bad water quality; other reasons such as lack of experience, red tides and reliability are contributed to the dominance of thermal plants. However, field experience showed that good pretreatment and optimized RO design may overcome the problems of high feed salinity and bad water quality. Several RO plants, such as Fujairah in UAE, are good examples of a working RO technology in the harsh water environment. Good RO design includes design and optimization of both pretreatment and post-treatment. Field experience showed that most of RO plants failure was due to inefficient pretreatment which resulted in providing low quality water to the RO membrane that caused fouling. Fouling, including biological and scaling, can be handled once an efficient pretreatment process is available. Recent advances in pre-treatment techniques include the combination of Forward Osmosis (FO) with RO among other methods. Recent studies by the authors including commercial implantations have shown that the combination of FO with RO addresses the most technical challenge of RO process and that is fouling, which results in lower energy consumption and less chemical additives. Experience showed fouling in FO process in reversible, i.e. can be removed by backlashing while fouling in conventional RO process is irreversible.In this study, the feasibility of integrating FO with RO process for the desalting of the Gulf water in Qatar is presented. The results are expressed in terms of specific energy consumption, process recovery, produced water quality, chemical additives and overall process cost.The implementation of RO for desalination is not only reducing the cost of desalination but also the environmental impact. More R&D should be done to provide useful data about RO application and suitability for the Gulf water. The R&D should be focused on laboratory to market development of RO technology using rigorous lab scale and pilot plant testing program.

Novel Tri Hybrid Desalination Plants

Solar energy, amongst all renewable energies, has attracted inexhaustible attention all over the world as a supplier of sustainable energy. The energy requirement of major seawater desalination processes such as multistage flash (MSF), multi-effect distillation (MED) and reverse osmosis (RO) are fulfilled by burning fossil fuels, which impact the environment significantly due to the emission of greenhouse gases. The integration of solar energy systems into seawater desalination processes is an attractive and alternative solution to fossil fuels. This study aims to (i) assess the progress of solar energy systems including concentrated solar power (CSP) and photovoltaic (PV) to power both thermal and membrane seawater desalination processes including MSF, MED, and RO and (ii) evaluate the economic considerations and associated challenges with recommendations for further improvements. Thus, several studies on a different combination of seawater desalination processes of solar energy systems are reviewed and analysed concerning specific energy consumption and freshwater production cost. It is observed that although solar energy systems have the potential of reducing carbon footprint significantly, the cost of water production still favours the use of fossil fuels. Further research and development on solar energy systems are required to make their use in desalination economically viable. Alternatively, the carbon tax on the use of fossil fuels may persuade desalination industries to adopt renewable energy such as solar.

This work presents a detailed thermo-economic analysis of unit water costs from dual-purpose cogeneration plants. The power levelized cost was first calculated for stand-alone steam, nuclear, and combined-cycle power plants. The cost of energy needed to operate the desalination systems connected to power plants was evaluated based on two different approaches: power- and heat-allocated methods. Numerical models based on the heat and mass balances of the power and desalination plants’ components were developed and validated. Comprehensive and updated data generated using Desaldata libraries were correlated to estimate the capital, labor, overhead, and maintenance costs for different desalination systems. The levelized water cost produced by multi-effect distillation, multi-effect distillation with vapor compression, multi-stage flash, and reverse osmosis systems connected to different power plants was estimated. The impact of various controlling parameters, including the price of natural gas, nuclear power plant installation cost, and the desalination capacity on water cost, was investigated. For all simulated cases, the levelized water cost evaluated using the heat-allocated method was found to be lower by 25–30% compared to that estimated using the power-allocated method. The cost of water produced using reverse osmosis remains below that produced by other desalination technologies. However, using the heat-allocated method to estimate the levelized water cost narrows the gap between the costs of water produced by multi-effect distillation and that produced by seawater reverse osmosis. The results also show that the use of the multi-effect distillation process in a cogeneration configuration rather than multi-effect distillation with vapor compression can result in a lower water cost. The profit analysis shows slight differences between the profit of a power plant connected to a reverse osmosis system and the profit of a power plant connected to a plain multi-effect distillation system.

Performance analysis of hybrid system of multi effect distillation and reverse osmosis for seawater desalination via modelling and simulation

Desalting - prospects for improvement in technology and reduction in costs

Hybrid systems in seawater desalination-practical design aspects, status and development perspectives

Desalination site selection on North-African coasts

Desalination site selection on North-African coasts

Water scarcity is an alarming global problem for a growing population with depleting sources of fresh water. Desalination is thus becoming an important solution for water management to address such looming shortage of the municipal water supply. At present, several technologies dominate the desalination industry which can be categorized either as a thermal process such as multi-stage flash distillation or a membrane process such as that of reverse osmosis. New desalination systems are also being developed to make the process more cost-effective and energy efficient. Hence, this work proposes a systematic approach for optimal selection of desalination systems using fuzzy analytic hierarchy process (FAHP) and grey relational analysis (GRA). Fuzzy AHP addresses the vagueness involve in the trade-off of the criteria or attributes used in evaluating the alternatives. On the other hand, the GRA solves the multiple criteria decision problem by aggregating the entire range of performance attribute values for every alternative into a single score in spite of incomplete information. An illustrative case study was presented wherein five desalination systems namely reverse osmosis (RO), combined reverse osmosis and forward osmosis (RO-FO), electrodialysis (ED), multi-stage flash distillation (MSF), and combined forward osmosis and membrane distillation (FO-MD) were evaluated. These desalination systems were compared to each other with respect to energy requirement, land footprint, system efficiency, economic viability, and maturity of technology. Sensitivity analysis was also done to determine the robustness of the modeling results from the variation of weights of the criteria.

Evaluation and minimisation of energy consumption in a medium-scale reverse osmosis brackish water desalination plant

State-of-the-art of reverse osmosis desalination

Mega-scale desalination efficacy (Reverse Osmosis, Electrodialysis, Membrane Distillation, MED, MSF) during COVID-19: Evidence from salinity, pretreatment methods, temperature of operation