Exergy analysis of a reverse osmosis desalination plant in California

With a reverse osmosis (RO) desalination plant designed to satisfy only the contracted-for water supply, the water company would be missing out on potential benefits that could have been obtained selling water in periods of high demand. On the other hand, sizing the RO desalination plant to produce water to satisfy peak demand means incurring additional costs as well as having the plant partially idle during periods of average or low demand. A model was developed using Excel macros to perform dynamic programming to optimize the capacity expansion of an RO desalination plant. The objective function is to maximize the present value of the total net benefits over the lifetime of the RO desalination plant. The model can be used to test different scenarios to capture time-variant tourism demand and price uncertainties on investment decisions. This study focuses on tourism dominated arid coastal regions, using Sharm El Sheikh (Sharm) in South Sinai, Egypt, as an example.19 RO plants in Sharm were surveyed and data were collected including unit production costs, O&M costs, energy consumption rates, contracted-for water supply, and utilization. Unit production cost of an RO desalination plant varies according to the degree of operation of the plant. This fact has to be taken into consideration when calculating the costs of RO desalination and when deciding on the plant capacity in order to maximize the total net benefit. Using the collected data, cost functions were developed for O&M costs as a function of utilization and plant capacity. The cost model calculated similar values to the actual total net benefit for one of the surveyed RO plant taken as an example. Using the optimization model, the maximum total net benefit is obtained with a smaller installed capacity than the actual case. A modified pricing structure is suggested in the paper that ties the water selling price to consumption in an effort to reduce demand in excess of contracted-for water supply aiding the water company to fulfill its contractual commitments to all users. However, price elasticity has to be taken into consideration to determine the impact of price change on water demand.

Seawater desalination is a vital source of drinking water, especially in coastal and remote areas. However, its sustainability is constrained by the high energy requirement. The need for fresh water supplies continues to rise due to its intensive use in many development sectors, such as agriculture and industry, as well as the continued increase in population. This has led to the idea of using nuclear power in seawater desalination to reduce the stress on the main electrical grid and enhance sustainable. The paper's goal is to optimize a reverse osmosis (RO) desalination plant to produce 100,000 m3 of fresh water daily. The best membrane is selected by testing 10 FilmTec membranes, with a focus on achieving optimal product quality (TDS) while maintaining an acceptable level of specific energy consumption (SEC). The study aims to address the challenge of delivering potable water by designing and modeling a standalone desalination plant powered by small modular reactors (SMRs). According to ROSA's analysis, the optimal RO desalination unit consists of two stages with a total of 175 membranes. The FilmTec SW30XHR-400 is identified as the best option based on superior water quality. This membrane has a specific energy consumption of 5.17 kWh/m3 and a low TDS of 141.4 mg/L. The total power consumption of the RO plant is approximately 21.5 MW; therefore, the KAREM-25 MWe reactor has been selected to be coupled with the RO desalination plant.

Exergy analysis of a combined RO, NF, andEDR desalination plant

The reverse osmosis (RO) process is one of the most popular membrane technologies for the generation of freshwater from seawater and brackish water resources. An industrial scale RO desalination consumes a considerable amount of energy due to the exergy destruction in several units of the process. To mitigate these limitations, several colleagues focused on delivering feasible options to resolve these issues. Most importantly, the intention was to specify the most units responsible for dissipating energy. However, in the literature, no research has been done on the analysis of exergy losses and thermodynamic limitations of the RO system of the Arab Potash Company (APC). Specifically, the RO system of the APC is designed as a medium-sized, multistage, multi pass spiral wound brackish water RO desalination plant with a capacity of 1200 m3/day. Therefore, this paper intends to fill this gap and critically investigate the distribution of exergy destruction by incorporating both physical and chemical exergies of several units and compartments of the RO system. To carry out this study, a sub-model of exergy analysis was collected from the open literature and embedded into the original RO model developed by the authors of this study. The simulation results explored the most sections that cause the highest energy destruction. Specifically, it is confirmed that the major exergy destruction happens in the product stream with 95.8% of the total exergy input. However, the lowest exergy destruction happens in the mixing location of permeate of the first pass of RO desalination system with 62.28% of the total exergy input.

This paper studies energy consumption management of seawater Reverse Osmosis (RO) desalination plants to maintain and enhance the Voltage Stability (VS) of Power Systems (PS) with Photovoltaic (PV) plant integration. We proposed a voltage-based management algorithm to determine the maximum power consumption for RO plants. The algorithm uses power flow study to determine the RO plant power consumption allowed within the voltage-permissible limits, considering the RO process constraints in order to maintain the desired fresh water supply. Three cases were studied for the proposed RO plant: typical operation with constant power consumption, controlled operation using ON/OFF scheduling of the High-Pressure Pumps (HPPs) and controlled operation using Variable Frequency Drive (VFD) control. A modified IEEE 30-bus system with a variable load was used as a case study with integration of three PV plants of 75 MWp total power capacity. The adopted 33.33 MW RO plant has a maximum capacity of 200,000 m3/day of fresh water production. The results reveal that while typical operation of RO plants can lead to voltage violation, applying the proposed load management algorithm can maintain the vs. of the PS. The total transmission power loss and power lines loading were also reduced. However, the study shows that applying VFD control is better than using ON/OFF control because the latter involves frequent starting up/shutting down the RO trains, which consequently requires flushing and cleaning procedures. Moreover, the specific energy consumption (SEC) and RO plant recover ratio decreases proportionally to the VFD output. Furthermore, the power consumption of the RO plant was optimized using the PSO technique to avoid unnecessary restriction of RO plant operation and water shortage likelihood.

the adaption of renewable energy (RE) in electric systems (ESs) involves many technical challenges when its share exceeds certain levels. Various strategies are used to manage these challenges. The reverse osmosis (RO) desalination plants can play a significant role in RE integration because of their high energy consumption and flexibility of operation. This paper investigates how RO desalination plants can help in integrating RE resources in ESs. First, the impact of different levels of RE penetration on IEEE 30-bus system was studied in terms of voltage profile. Then, the adaption of an RO plant in the system as a flexible load was introduced to reduce the effects of RE penetration. The consumption of RO plant was decreased during the absence of RE and increased at the midday hours to absorb the surplus power generated by RE. This prevented the ES voltage profile to fall below the permissible limits. The results showed that, the coordination between RO plants and ESs operation had a significant positive role.

Impact of solar energy cost on water production cost of seawater desalination plants in Egypt

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The population in Ramanathapuram district of Tamil Nadu State (India) faces potable water scarcity throughout the year in general and acute drinking water problems in lean periods of the year. To mitigate this problem, eleven reverse osmosis (RO) desalination plants were installed in problem villages in the district. General performance of these eleven plants and in-depth evaluation of two plants was undertaken to focus attention on the physico-chemical quality of water at various stages of treatment, present status with respect to operation and management (O & M) financial implications and overall management in a rural situation. The study indicated that performance of these RO plants was satisfactory in removing high TDS, though the efficiency deteriorated with time. The average utilization of these RO plants since their installation was 46% as compared to the design capacity, mainly due to non-availability of power in rural areas, time lapsed in repairs of pumps, and non-availability of spares. The average capital cost/m3 and O & M cost/m3 of product water from these eleven plants works out to Rs. 27.40 and Rs. 44.50 respectively; when plants are utilized as per the design capacity. These costs are high and not affordable by the rural population. The RO plants were socially acceptable since the population was satisfied with the treated water quality.

Modified PID control with H∞ loop shaping synthesis for RO desalination plants

Capital cost estimation of RO plants: GCC countries versus southern Europe

Saline groundwater is the primary water source for agricultural development in the United Arab Emirates (UAE). Many small-scale reverse osmosis (RO) desalination plants have been installed to desalinize saline groundwater for use in irrigating vegetables (mainly in green houses), forages, date palm and fruit trees. Twelve plants in inland areas and three plants in coastal areas were studied to evaluate the existing brine disposal practices. The capacity of ROs varied from 28 to 325 m3 d-1. Pre-treated brackish groundwater, salinity varying from 4 to 37 dS m-1, was used as feed water. Higher groundwater salinity was observed in coastal areas due to sea-water intrusion. Chemical analysis of brine and soils at the disposal sites showed trace existence of heavy metals. The methods of brine disposal include (i) surface disposal (to excavated/non-excavated pits or mountain terrain or steep edge of sand dunes), (ii) well injection or dug well, (iii) pipeline discharge to sea beach, (iv) irrigation of salt-tolerant plants or blending brine with feed water for irrigating date palm, (v) use in cooling pads of green houses, and (vi) discharge to wadi beds. Among the disposal methods, surface disposal and dug well near the RO plants are critical as feed water can be further polluted by brine and chemicals used in the desalination process. These disposal practices could be replaced by environmental friendly methods such as non-leaking evaporation ponds and biosaline agriculture.

This report has been prepared as part of an effort to design and build a Modeling and Simulation (M&S) framework to assess the economic viability of a Nuclear-Renewable Hybrid Energy System (N-R HES). In order to facilitate dynamic M&S of such an integrated system, research groups in multiple national laboratories and universities have been developing various subsystems as dynamic physics-based components using the Modelica programming language. In Fiscal Years (FYs) 2015, Idaho National Laboratory (INL) performed a dynamic analysis of two region-specific N-R HES configurations, including the gas-to-liquid (natural gas to Fischer-Tropsch synthetic fuel) and brackish water Reverse Osmosis (RO) desalination plants as industrial processes. In FYs 2016–2017, INL developed two additional subsystems in the Modelica framework: (1) a high-temperature steam electrolysis plant as a high priority industrial plant to be integrated with a light water reactor within an N-R HES and (2) a gas turbine power plant as a secondary energy supply. In FY 2018, the RO desalination system model developed in FY 2015 has been updated such that the model is compatible with the most recent version of the ThermoPower library. Special attention has been given to the controller settings based on process models, aiming to improve process dynamics and controllability. A dynamic performance analysis of the updated RO desalination plant was carried out to evaluate the technical feasibility (load-following capability) of such a system operating under highly variable conditions requiring flexible output. Simulation results involving several case studies show that the suggested control scheme could maintain the controlled variables (including the variable electrical load and RO feed pressure) within desired limits under various plant operating conditions. The results also indicate that the proposed RO plant could provide operational flexibility to participate in energy management at the utility scale by dynamically optimizing the use of excess plant capacity within an N-R HES. For a small-scale energy storage system, a sensible Thermal Energy Storage (TES) model has been developed in the Modelica Framework in FY 2018.

A theoretical analysis on upgrading desalination plants with low-salt-rejection reverse osmosis