The SDAWES project: lessons learnt from an innovative project*
Abstract
The Seawater Desalination by an Autonomous Wind Energy System (SDAWES) project was developed to produce a natural scarce resource (fresh water) by the use of a natural, renewable resource (wind energy). The basic concept consists in the connection of three kinds of desalination systems: reverse osmosis, vacuum vapour compression and reversible electrodialysis to a stand-alone wind energy system to produce fresh water from seawater on a significant scale (total nominal water production: 440 m3/d). The main objectives of the project were to identify the best desalination system for connection to a stand-alone wind farm and to assess the influence of the variations of wind energy on the operation of the desalination plants and on the quality of the water produced. This is a project where several lessons were learnt after two years' testing experience. This paper presents the main problems detected during that period and the experimented proposed solutions.
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Modular operation of renewable energy-driven reverse osmosis using neural networks for wind speed prediction and scheduling
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Optimization of sustainable seawater desalination: Modeling renewable energy integration and energy storage concepts
2023, Energy Conversion and ManagementMany arid and semi-arid regions of the world face growing freshwater scarcity, requiring increased utilization of seawater desalination to augment the existing freshwater resources. Seawater reverse osmosis (RO) is currently one of the most deployed technologies, due to its electrical energy efficiency and comparatively low costs. However, the required energy for desalination processes is often still converted from fossil sources. Given the growing demand for seawater desalination and the energy sector’s parallel decarbonization, the substitution by renewable energy sources (RES) is a critical issue. The volatility, lower availability of renewable energy, and cost for required electrical energy storage (EES) are all obstacles to the decarbonization of large-scale desalination plants and may affect production volume and water production costs negatively.
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Results indicate that RES cannot meet an RO desalination plant’s full and constant electrical load demand without a high BES capacity, which is probably not feasible from a technical and economic point of view. The economic penalty from energy storage costs on one unit of desalinated water ranges from 3.10 $/m3 up to 5.38 $/m3. However, operating an oversized RO desalination plant intermittently could reduce the energy-related costs substantially and potentially provide a more appropriate way of adapting to a volatile supply of energy from renewable sources in order to decarbonize the desalination processes. Specific emissions of desalinated water can be reduced from 1.5 kg CO2 eq./m3 when relying mostly on combined cycle gas turbines down to 0.124 kg CO2 eq./m3 by intermittent operation and fully relying on renewable energy sources.
Renewable energy systems for water desalination applications: A comprehensive review
2023, Energy Conversion and ManagementRenewable energy sources are expected to provide viable alternative solutions for water desalination to address the issues of high-energy consumption and negative environmental impacts. However, the compatibility of each desalination process with solar technology strongly depends on the kind of energy required as thermal (collectors) or electrical (photovoltaic panel) and its availability. Due to the Bulkiness of solar-based systems and intermittency and non-uniformity of solar energy, several issues arise when it comes to its utilization to drive the desalination processes while targeting positive competitiveness with fossil fuels powered systems. The water production costs of large-scale renewable energy-assisted desalination systems are still higher than those of traditional fossil fuels. This study comprehensively summarizes the efforts made in renewable energy utilization in the desalination industry, with an emphasis on technological advances and economics. This study also includes recent developments and improvements in desalination processes, renewable energy technologies, and energy storage systems. In addition, this review highlights the geographical distribution, potential application, and main barriers and challenges of renewable energy-based desalination. Finally, the current and expected costs of water production using conventional and renewable energy systems were presented. Thermal desalination processes consume more energy than membrane-based systems because the former consumes a large amount of energy for water vaporization. Regarding the production cost of renewable-energy-powered desalination systems, the wave-powered reverse osmosis (RO) system had the lowest production cost, followed by solar multiple effect distillation (MED), solar multi-stage flash (MSF), wind RO, and wind mechanical vapor compression (MVC), whereas the PV-powered RO system had the highest production cost.
Variable operation of a renewable energy-driven reverse osmosis system using model predictive control and variable recovery: Towards large-scale implementation
2022, DesalinationPowering Reverse Osmosis (RO) systems with Renewable Energy (RE) is essential for decarbonising water production. Integration of RE requires large-scale RO plants to operate efficiently using variable power. Nevertheless, variable operation (involving matching the RO load to available power without battery back-up) has only been implemented for small-scale systems. This paper presents a variable-speed operation technique suitable for large-scale RO systems using an optimised operational strategy and a Model Predictive Controller (MPC). The technique was validated using a laboratory test rig having comparable performance to large-scale systems. A dynamic plant model was used to design the operational strategy and control system. Several operational strategies were explored for varying the operating parameters according to power available from a RE source. An advanced control system based on MPC was designed and compared to a conventional Proportional-Integral-Differential controller. The results showed that operation at variable recovery with constant brine flowrate delivered the lowest specific energy consumption and widest operation range for a system with an isobaric pressure exchanger. The MPC controller improved the settling time for a 10% step-change in permeate flowrate by 47%. Moreover, it improved energy utilisation, giving a 2.35% increase in hourly permeate production for a defined power input time-series.
Performance of reverse osmosis membrane with large feed pressure fluctuations from a wave-driven desalination system
2022, DesalinationWave-driven desalination systems are proposed water treatment systems that involve reverse osmosis of seawater powered directly by wave motion. Such a configuration would result in drastic feed pressure fluctuations. For a technology conventionally operated with a constant feed condition, the effect of these variable pressures on membrane integrity and performance is unknown. Experiments were conducted with spiral wound membranes coupled to a system capable of producing feed pressure fluctuations of more than 400 psi. Feed composition included 5, 20, and 35 g/L NaCl, and a synthetic seawater at normal and 1.5× concentration. The variable feed conditions included sine-like pressure waves swings of 200–500 and 500–900 psi with frequencies of 1.25, 7.5, and 12 waves/min, and a model-generated random waveform. Between each wave experiment we performed membrane integrity tests at 650 psi and 25 g/L NaCl feed, which showed a 7.4% drop in the membrane's water permeability coefficient, an 18.4% flux decline, and more than 99% salt rejection over 1770 h of cumulative experimental time. Analysis of permeate samples showed high salt rejection. In general, variable feed pressure had no significant deleterious effect on membrane integrity or performance.
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Presented at the EuroMed 2004 conference on Desalination Strategies in South Mediterranean Countries: Cooperation between Mediterranean Countries of Europe and the Southern Rim of the Mediterranean. Sponsored by the European Desalination Society and Office National de l'Eau Potable, Marrakech, Morocco, 30 May–2 June 2004.