Sustainable options for desalination: A look into renewable energies and brine disposal

Water is a crucial ingredient for human health and one of the very few vital needs of human beings. More than 1.2 billion people around the work suffer from a deficiency of safe drinking water so that it is estimated that 14% of the global population lives in water-scarce regions by 2050. Although desalination has been used as conventional water providing technology for a long time in the Middle East and the Mediterranean, it has extensive capacities in the USA, Europe, and Australia as well. Interest in investment in desalination sector has been extending beyond these regions of the world which are driven by water stress concerns. Even though desalination has the potential to increase the water supply in water-scarce regions, its associated adverse consequences and constraints cannot be ignored. Brine disposal is the primary environmental consequence that should be considered and studied when installing a desalination plant. Therefore, essential steps must be taken to ensure safe and sustainable brine disposal. Implementation of a proper brine disposal method incorporated with a qualified design and construction procedure can mitigate the destructive effects of the desalination plants on the water environments and groundwater aquifers. Using solar power as a renewable source can both imitate the environmental impacts of the conventional brine disposal methods and an increase in the evaporation rate of the solar traditional evaporation ponds. Directing the brine effluent into the solar saltworks can possibly produce salt, and therefore, the desalination plant would be zero liquid discharge (ZLD). This method requires large land areas and thus is only applicable in arid and semi-arid regions where the evaporation rates are high and the value of the land is low. Also, expensive liners are needed to avert salt seepage from the soil and the groundwater contamination. If the evaporation rate is improved, the need for the same amount of land would consequently be reduced. Enhancing the rate of evaporation would have two benefits of the flexibility to increase the amount of the brine wastewater flows out of an evaporation pond and a reduced amount of land that would be needed to achieve the same rate of evaporation.

Nowadays, shortage of the water resources is a global issue. Water desalination is a solution that can be used to solve the water shortage problem. Several methods have been proposed for water desalination and are categorized to membrane and non-membrane procedures. The most popular membrane processes are electrodialysis (ED) and reverse osmosis (RO); in contrast, the most popular non- membrane processes are capacitive deionization (CDI) and distillation. All water desalination procedures need energy supplies. The solar and Photovoltaic (PV) energy is potentially a desirable green energy supply for water desalination especially for non-residential areas where the grid is not available. In areas such as deserts and offshore stations, the PV solar energy is a practical and cost effective solution for water desalination systems. Where the grid connection is available, the PV and solar desalination systems produce fewer emissions. The PV energy needs to be processed through power electronic power conditioning systems. This paper proposes the application of PV power and solar energy to supply the water desalination systems.

With projected increases in population and urbanisation in Australia, the sustainable supply of water and energy over the medium to long term will be an important challenge. In this context, meeting a part of the growing demand for urban water may involve reliance upon desalinated water in the future. Moreover, the feasibility and viability of renewable energy sources for water desalination will be of policy importance, particularly in a potentially low carbon Australian economy. In this article, we analyse the potential applicability of solar and wind energy to provide power for water desalination. In two illustrative examples, we assess the feasibility of supplying 3% of Sydney’s projected total water consumption (supplied at an average rate of 24.7 Gl/yr) and 5% of Sydney’s projected water consumption (supplied at an average rate of 32.7 Gl/yr) over a 15-yr period (2011–2025) using a photovoltaic (PV) solar powered (130 MW) and a hybrid (PV solar and wind energy) powered (205 MW) reverse osmosis (RO) desalination plants, respectively. In addition to supplying cleaner energy, the renewable energy sources considered in this article have additional cost advantages in the presence of a carbon penalty. For example, at hypothetical carbon penalty rates of $20/tCO2 and $30/tCO2, the estimated cost savings—in net present value (NPV) terms assuming a discount rate of 4.2%—of the PV solar (hybrid) plant will amount to around be $18.7 m ($25.2 m) and $28.0 m ($37.9 m), respectively, over the 15-yr period, relative to a situation where the desalination plant is instead being powered by black coal. Under a discount rate of 8.4%, the cost savings of the PV solar (hybrid) plant associated with carbon penalty rates of $20/tCO2 and $30/tCO2 are estimated to be around $12.8 m ($17.6 m) and $19.2 m ($26.4 m), respectively, in NPV terms. Our analysis also shows that in addition to providing the required power supply for the illustrative desalination plants, the renewable energy supply sources analysed here would produce excess electricity that could be sold to a nearby grid. Consequently, assuming a wholesale electricity price of $36.74/MWh, the PV solar plant and the hybrid renewable plant are estimated to have the capacity to earn around $63.9 million and $110.0 million in NPV terms, respectively, over the 15-yr period, through excess electricity sales. Under a discount rate of 8.4%, the value of the excess electricity sales of the PV solar plant and the hybrid renewable plant are estimated to be around $54.5 million and $91.7 million, respectively, in NPV terms.

In the following decades there will be a fundamental structural change in the European power supply system. This structural change is forced by several factors, e.g. the European Union Greenhouse Gas Emission Trading Scheme, the strategic goal for the European Union of a more sustainable development, energy policy targets to double the share of renewable ener-gies, the phase out or moratoria of the nuclear industry in some European Union member states, and the need of more than 200 GW of new power plant capacities in EU-15. The struc-tural change has to be embedded into an economic, social and ecological framework. Within this framework, there is a variety of possible options to create a future power supply which fulfils the multiple criteria. Generally, different technologies can be chosen which all have their own advantages and disadvantages. It is a challenging decision-making process because fossil-fired power plants tend to be economically advantageous and ecologically disadvanta-geous whereas renewable energy systems tend to be ecologically advantageous and economi-cally disadvantageous. This study gives a comparison of the estimated external costs (environmental aspects) and internal costs (economic aspects) of different power generation technologies in the year 2010 in order to support the decision-making process of future power plant investments in the framework of a sustainable development. A life cycle analysis gives considerable life cycle data for photovoltaic systems, wind turbines, fuel cells, bio-fuelled combined heat and power plants, biomass, water, solar thermal, geothermal, coal-fired, lignite-fired and natural gas-fired power plants as well as nuclear power plants. This database is used for the estimation of external costs which is based on updated factors of damage and avoidance costs for selected emissions. The damage factors are calculated with the software tool EcoSense following the impact pathway approach. Global warming and discounting are considered to be the hot spots in the external costs discussion. An avoidance costs approach is applied which is assumed to fulfil sustainability criteria. The comparison of the external costs of the technologies analysed shows that external costs of power generation technologies using renewable energies and nuclear power plants are in the range of 0.03-3.79 €-Cent/kWhel whereas the external costs of power generation technologies using organic fossil fuels are in the range of 3.37-27.98 €-Cent/kWhel. However, the comparison of the internal costs shows that fossil-fuelled power plants have the lowest internal costs compared to the other technologies analysed. This trade-off between external and internal costs requires a comparison of the social costs which are the sum of internal and external costs. The comparison of the social costs shows five social cost clusters for the ana-lysed technologies for the year 2010. Nuclear power plants have social costs of less than 10 €-Cent/kWhel. Wind turbines and river power plants have slightly higher social costs of 10-15 €-Cent/kWhel. Biomass power plants, bio-fuelled combined heat and power plants, solar ther-mal power plants, geothermal power plants and natural gas-fired power plants have social costs in the range of 15-20 €-Cent/kWhel. Photovoltaic systems in Spain, fuel cells, coal-fired power plants and lignite-fired power plants have social costs in the range of 20-35 €-Cent/kWhel. The highest social costs are caused by Photovoltaic systems in Germany with more than 35 €-Cent/kWhel.

Evaluation of different hybrid power scenarios to Reverse Osmosis (RO) desalination units in isolated areas in Iraq

RES Directive 2009/28/EC on the promotion of the use of energy from renewable energy sources sets an overall binding target of supplying 20% of European Union (EU)’s final energy consumption from renewable energy sources by 2020 with binding national targets for each Member State. Details of how these targets will be achieved in each Member State are described in National Renewable Energy Action Plans (NREAPs). High RES scenario presented in Energy Roadmap 2050 by European Commission (EC) foresees that 75% of the gross final energy can be supplied from renewable energy sources by 2050. This challenging target calls for a major effort to increase the number of qualified workers in the market able to cover the demand for high quality RES installations in the upcoming years. The substantial need for training and qualification is acknowledged in the RES Directive, Article 14(3), which includes an obligation on the Member States to make provision for the training and certification of installers of RES. This effort is also supported by actions such as the EC initiative Build Up Skills, launched by the Commission in 2011, which aims to unite forces to increase the number of qualified workforce by promoting training and qualification in the field of energy efficiency and renewable energy in the building sector in Europe. The Install+RES training courses are fully in line with this line of action and aim at providing a pool of highly qualified trainers and installers (electricians, plumbers, roofers and technicians for heating systems) of small-scale renewable energy systems (biomass, solar, photovoltaic systems and heat pumps) for buildings in several European countries, namely Bulgaria, Greece, Italy, Poland and Slovenia, by establishing training courses. 33 courses have been implemented, 78 trainers and 516 installers have been qualified during the Install+RES project in the field of renewable energy systems installations. The Install+RES project started in May 2010 and ended in April 2013. The Install+RES project was co-financed by the European Commission in the framework of the Intelligent Energy Europe (IEE) Program. The Install+RES training courses material was developed in line with the requirements mentioned in Directive 2009/28/EC (Article 14, Annex IV). The Install+RES training courses were completed with an exam leading to a certification or qualification according to the requirements of the Directive 2009/28/EC. The high quality of the courses offered within the Install+RES project was ensured by the “train the trainers” courses. During the “train the trainers” courses, the trainers, who will implement the training courses for installers, acquired practical and theoretical knowledge to properly implement the training courses for installers of small-scale renewable energy systems in their countries. During the “train the trainer” courses, the trainers obtained the pedagogical and technical skills to implement the “Install+RES” courses for installers in their respective countries (Italy, Slovenia, Bulgaria, Greece and Poland). The innovative aspects of the Install+RES “train the trainer” courses such as the “hand on learning” concept, “tandem teaching” approach and the “multiplier effect” are highlighted in the following explanatory pages. The Install+RES “train the trainer” courses was established in Munich, Germany, in German and English languages. The participants of the training courses were the Install+RES training providers and also third party organisations interested in establishing training courses in their own countries. The content and the methodology of the training courses have been adapted to each target country (Poland, Italy, Slovenia, Bulgaria and Greece) according to the potential installers’ and markets’ needs resulting from the NREAPs in line with the RES Directive. The adapted material has been translated into the National languages of each target country. One pilot course and two training courses for installers have been offered in Bulgaria, Greece, Italy, Poland and Slovenia in the National languages. The Install+RES training courses are meant to be an investment for sustainability by evolutionary processes, which will lead to the establishment of a high quality of skills and as consequence to the maximization of Renewable Energy Systems (RES) s efficiency, reliability, lifetime and safety. The training material and training concept developed during the Install+RES project has given a strong contribution to ensure the achievement of the targets stated in the National Renewable Energy Action Plans and in the High RES scenario of the Energy Roadmap 2050 as well as to the roadmaps to 2020 developed within the BUILD UP SKILLS Initiative.

In recent years, reverse osmosis water desalination has developed rapidly and has become the most competitive and widely used technology in the world. The number of desalination plants is increasing rapidly as freshwater needs increase. Various membrane technologies have been developed and improved, including nanofiltration (NF) and reverse osmosis (RO), whose desalination costs have been relatively reduced. Therefore, this work proposes an experimental study for a small desalination unit based on RO generated by renewable energy, which is mainly suitable for arid regions or desert areas that do not have electricity and water and can be applied for emergency treatment to meet strong freshwater resource needs. In this study, to meet the drinking water demand, a reverse osmosis desalination system is designed and evaluated in order to improve and optimize its operation. This system has a daily capacity of 2 m3. We used brackish groundwater, which has been characterized as reference water, to produce synthetic water for different salinities until seawater. The analysis is based on data obtained from experiments carried out in the standalone RO pilot designed for the production of fresh water. For this purpose, we conducted relevant experiments to examine the influence of applied pressure, salt concentration and temperature on the RO membrane performance. The effects of different factors that affect the energy consumption in the RO desalination process were analyzed, and those with significant influence were explored. The effectiveness of RO desalination coupled with a photovoltaic (PV) energy system is shown. We found the recovery rate for system operation to be 32%. An optimization study is presented for the operation of an autonomous RO desalination system powered by photovoltaic panels. The energy produced by the PV system was used to feed two pumps forthe production of drinking waterwithanRO membrane, under the conditions of the town of Bou-Ismail. As results, a 3 kWp PV system was installed based on the energy demand. The design data have shown that a 3 kWp PV system can power a 1.8 W RO load given the Bou-Ismail climate. Energy consumption in the case study under Bou-Ismail weather conditions were analyzed. The desalination of brackish water at a TDS value of 5 g/L requires an energy of about 1.5 kWh/m3. Using seawater at a TDS value of 35 g/L, this value increases to 5.6 kWh/m3. The results showed that the optimal recovery rate for system operation was determined to be 32% for a feedwater salinity of 35 g/L, and 80% for a feedwater salinity of 1 g/L.

Hybrid membrane system for desalination and wastewater treatment : Integrating forward osmosis and low pressure reverse osmosis

Nanofiltration (NF) and reverse osmosis (RO) membranes are used to produce clean water, but also produce a concentrate stream which contains most of the contaminants. Discharging concentrate streams to the environment is hindered by regulations, which are becoming more strict, and by the desire of recovering every single valuable atom. Therefore, the minimization of the concentrate volume to almost zero, is required in order to make treatment of the concentrate feasible. Currently several research studies are being conducted to find smart zero liquid discharge (ZLD) strategies in water desalination. In this PhD work the feasibility of reaching very high recovery (which equals a very low volume of concentrate) in a system consisting of cation exchange pretreatment, NF and RO (with the RO implemented on the NF concentrate to increase feed water recovery) was studied. The outcome of this research indicates that the nearly ZLD concept is technically possible, with the right combination of techniques. The studied system could be applied for the production of drinking water from ground water or surface water with high concentrations of bivalent cations, silica and/or organic micropollutants.

Brine disposal from reverse osmosis desalination plants in Oman and the United Arab Emirates

This study introduces a Zero Liquid Discharge (ZLD) scheme for Reverse Osmosis (RO) desalination, integrating ultra-filtration pretreatment and Electrodialysis (ED) for brine concentration. The scheme divides brine reject into fractions, directing them to an electrolyser and evaporator powered by renewable energy sources. Notable findings include the treatment plant's capability to produce 792 cubic meters of fresh water daily, while decreasing salt concentration from 4,660 ppm to 30 ppm, showcasing efficient desalination. Additionally, recycling fractions of RO unit waste to various components enhances resource efficiency. The study highlights the daily production of 2,269.27 kg of hydrogen, coupled with minimal electricity consumption of 74,885.91 kWh, thereby improving overall energy efficiency. Furthermore, the utilization of solar energy significantly reduces reliance on fossil fuels, thereby promoting sustainability and mitigating the environmental impacts associated with traditional energy sources. Solar energy is a clean, renewable resource that helps decrease greenhouse gas emissions and other pollutants, contributing to cleaner air and a healthier planet. This shift towards renewable energy is crucial in addressing climate change and ensuring a sustainable future for generations to come. In the context of desalination, emphasizing environmental preservation and water security is paramount. Desalination processes, while providing essential fresh water in arid regions, often produce brine as a byproduct. The brine, with a high salt concentration of 13,648 ppm, poses a disposal challenge that can negatively impact marine ecosystems if not managed properly. This is where Zero Liquid Discharge (ZLD) systems come into play. With a ZLD index of 2.7%, these systems ensure that all wastewater is treated and reused, leaving no liquid waste behind. ZLD technology captures and recycles every drop of water, converting waste into reusable resources, thus minimizing environmental harm. The model showcased a significant decrease in brackish water extraction from 1,200 cubic meters per day to 871.52 cubic meters per day, marking a notable 27% reduction. These results highlight the promising effectiveness of the proposed ZLD scheme in enhancing the efficiency of brackish water treatment, demonstrating its potential to significantly reduce the demand for fresh water resources while achieving sustainable desalination practices. This article will present a detailed yet a simple description of reverse osmosis and ZLD, how do they correlate and how these two technologies represent the future of water treatment.

Current brine management strategies are based on the disposal of brine in nearby aquifers, representing a loss in potential water and mineral resources. Zero liquid discharge (ZLD) is a possible strategy to reduce brine rejection while increasing the resource recovery from desalination plants. However, ZLD substantially increases the energy consumption and carbon footprint of a desalination plant. The predominant strategy to reduce the energy consumption and carbon footprint of ZLD is through the use of a hybrid desalination technology that integrates renewable energy. Here, we built a computational thermodynamic model of the most mature electrified hybrid technology for ZLD powered by photovoltaic (PV). We examine the potential size and cost of ZLD plants in the US. This work explores the variables (geospatial and design) that most influence the levelized cost of water and the second law efficiency. There is a negative correlation between minimizing the LCOW and maximizing the second-law. And maximizing the second-law, the states that more brine produces, Texas is the location where the studied system achieves the lowest LCOW and high second-law efficiency, while California is the state where the studied system is less favorable. A multiobjective optimization study assesses the impact of considering a carbon tax in the cost of produced water and determines the best potential size for the studied plant.

Optimization of sustainable seawater desalination: Modeling renewable energy integration and energy storage concepts

Solar energy is one of the pure and non-detrimental resources for environment which has long been utilized by humans. Therefore, in order to move toward sustainable development, it is required to pay attention to practical and scientific use of renewable energies such as solar energy even more seriously than before. Hence, one of the main objectives of sustainable architecture is to move toward designing solar buildings and supplying heating and cooling needs of buildings by renewable energies. Among the important characteristics of benefiting from renewable energies such as solar energy, one could refer to their purity and nonpolluting features which lead to removing greenhouse gas emissions, free costs and availability, safety and finally reducing fossil fuel consumption. The present research is a descriptive and analytic study and it should be noted that the advantages of using solar energy in an administrative building is examined. Given the utilization of solar photovoltaic panels in the building of Ministry of Economic Affairs and Finance, the method for selection and the advantages of utilizing the aforementioned technology for sustainable urban development with respect to economics and environment will be investigated.

Currently, most photovoltaic (PV) modules are aligned in a way that maximizes the overall annual yields, which leads to significant peaks in electricity production and could threaten energy policy objectives such as security of supply as well as environmental sustainability. The exploitation of remaining PV potentials at seemingly economically sub-optimal inclinations and azimuth angles could partly counteract this trend by achieving significant temporal shifts in the electricity production. This paper addresses the potential of these counter-measures by evaluating the optimal mix of wind and PV installations with different inclination and azimuth angles in a regional context. It does so by adhering to three distinctive energy policy goals: economic efficiency, sustainability and security of supply. It is further assumed that the examined regions aim for energetic autarky. The hourly yields of wind parks and PV installations with different mounting configurations are simulated for four representative NUTS3-regions in Germany, based on assumed installed capacities and specific weather conditions. These profiles are combined with standardized regional electricity demand profiles and fed into an optimization model, which is employed to maximise each of the three energy policy goals independently. As a result the optimal installed capacity for PV for every possible configuration – determined by inclination and azimuth angles – and the optimal installed capacity of wind power are determined. The results indicate that the optimal mix differs significantly for each of the chosen goals and depends on regional conditions, but shows a high transferability in terms of general conclusions. For economic efficiency – the first of the three goals – a focus on a high share of wind power and south-oriented PV-systems is feasible for all German regions. When sustainability is chosen as the energy policy goal, results depend largely on the conventional power plant utilization and its CO2-equivalent emissions leading to a high share of PV-systems in ratio to wind power. When maximizing the third goal, the security of supply, PV plants facing east and west as well as wind turbines are preferred, since this homogenizes the daily combined PV production. The developed methodology is found to be robust with regard to the relative conclusions, whilst the absolute magnitude of the results is sensitive to the input data. Further work should focus on refining the representativeness of the four model regions and on quantifying the three considered criteria more holistically.