열압축기를 채용한 다중효용 담수설비의 운전특성에 관한 연구(1보)

The efficacy of seawater desalination has a profound impact in terms of reducing the water demand-supply gap especially in dry and arid countries. In UAE, 90% of the country’s water supply relies solely on desalinated water where a high share of the desalination plant’s output is aimed towards water supply for residential buildings. The hospitality sector consumes 50% more than the global average. The purpose of this paper is to determine the technical and economic viability for the integration of a concentrated photovoltaic thermal (CPV/T) system with a hybrid reverse osmosis (RO) and multi effect desalination (MED) plant. The system was designed to meet the water demand of a luxurious beach resort located in Fujairah. The resort accommodates about 110 occupancies per day. The estimated water consumption is 51m3/hr. The proposed system was analyzed with the aid of numerical simulation and reverse engineering calculations. The capacity of the CPV/T module, which represents the electrical and thermal energy output supplied to the RO and MED plant was determined using TRNSYS software. The results showed an efficient solar system providing electricity of 3500 kWh/year and thermal energy of 14,100 kWh/year, that is required to meet the water consumption of the hotel. In addition, the proposed system proved to be economically feasible, achieving a payback period of 3.6 years under an average lifetime of 20 years.

Water is one of the most stressed resources on the planet. The limited availability of fresh water and the high cost of transportation have led to an increased interest in water desalination technologies. The two main categories of desalination techniques are membrane desalination and thermal desalination. Membrane technologies include pressure driven and electrical driven membranes. On the other hand, thermal desalination includes: multi-effect desalination (MED), multi-stage flash (MSF) desalination, and mechanical vapor compression desalination. Multi-effect desalination plants are usually made of a series of evaporators (also known as effects). In each effect, hot steam flows inside the tubes and evaporates the seawater that falls on the outside of the tubes. The vapor formed at each effect flows to the next effect and acts as the heating medium for the falling seawater. The prevailing flow mode of the falling seawater (i.e. droplet, jet, or sheet) influences heat and mass transfer as well as dry out in the evaporators of Multi-Effect Desalination (MED) plants. The objective of this paper is to predict and discuss the prevailing falling film flow modes in the evaporators of MED plants, under different operating conditions. The paper demonstrates the transitional Reynolds numbers between the main falling film modes for seawater. This closes a gap in the literature where there is a dearth of mode transition data for seawater. The effect of fluid properties and tube geometry on the transitions is discussed in details. The accuracy of the predicted transitional Reynolds numbers is evaluated via uncertainty quantification techniques.

scarcity. Underground water is mostly saline and other sources are small seasonal rivers and dams that collect rain water for sprawling population. Desalination plants can alleviate this problem to an extent. This paper examines various desalination plants, provides detailed technical discussion of Passive Vacuum Flash Type Solar Thermal technology and compares it with Concentrating Solar Desalination technology. Comprehensive levelised cost of water calculations are laid out for conventional Reverse Osmosis (RO) plant, Photovoltaic (PV) RO plant, conventional thermal Multi Effect Desalination (MED) plant and solar thermal MED plant. PVRO with cost of PKR 0.39 per gallon is the most suitable option.

Advanced MED process for most economical sea water desalination

Techno-economic analysis of a combined concentrated solar power and water desalination plant

Fresh water production is one of the main concerns in the new century. Population grows fast and potable water resources are decreased. In the other hand energy crises would also be another issue that must be well addressed by the politicians and also scientists. Developing desalination plant with using renewable energy (particularly solar energy) is one of the important options to overcome these concerns. Thus many researchers have been working on different desalination plants to find the best conditions and to realize the most efficient performances for different cycles. Different approaches have been used to achieve the most efficient conditions or to find the optimum operation and design conditions. Some of the researchers used parametric study approach while many other adopted different conventional optimization algorithms for these tasks. The algorithms such as gradient based algorithm, genetic algorithm, search and pattern algorithm and neural network method have been used in the field of desalination. For instance; Ophir and Lokiec (2005) described the design principles of a MED plant and various energy considerations that result in an economical MED process and plant. Kamali and Mohebbinia (2007) showed that parametric study as one of the optimization methods on thermo-hydraulic data strongly helps to increase GOR value inside MED-TVC systems. Shamel and Chung (2006) used parametric study to find the optimum condition of a Reverse Osmosis (RO) system for sea water desalination. Metaiche et al (2008) developed optimization software, Desaltop, for RO system for water desalination. They used genetic algorithm to find suitable operating parameters and also to find appropriate type of membrane. Al-Shayji (1998) used neural network method for optimization of large-scale commercial desalination plants. Djebedjian et al. (2008) used genetic algorithm for optimization of a reverse osmosis desalination system. Mussati et al. (2003) used an evolutionary algorithm for the optimization of Multi Stage Flash (MSF) system. Finding the optimum conditions is a major challenge on the desalination plant studies. The plant performance depends on several different variables and constraints that need exhausting efforts to find the optimum conditions. This chapter introduces Design of Experiment (DOE) method as a statistical tool for optimization of desalination systems. Thus two different desalination plants; Multi-Effect Desalination (MED) system and solar desalination using humidification–dehumidification cycle (SDHD) have been considered to show the ability of DOE method for optimizing such systems. These both desalination plants could use the low graded heating energy sources

This work suggests a solution for preventing/eliminating the predicted Sea Level Rise (SLR) by seawater desalination and storage through a large number of desalination plants distributed worldwide; it also comprises that the desalinated seawater can resolve the global water scarcity by complete coverage for global water demand. Sea level rise can be prevented by desalinating the additional water accumulated into oceans annually for human consumption, while the excess amount of water can be stored in dams and lakes. It is predicted that SLR can be prevented by desalination plants. The chosen desalination plants for the study were Multi-Effect Desalination (MED) and Reverse Osmosis (RO) plants that are powered by renewable energy using wind and solar technologies. It is observed that the two main goals of the study are fulfilled when preventing an SLR between 1.0 m and 1.3 m by 2100 through seawater desalination, as the amount of desalinated water within that range can cover the global water demand while being economically viable.

طی دوره‌ی 2010 تا 2016 بازار نمک‌زدایی آب با رشد سالانه‌ی 9 درصد و مجموع سرمایه‌گذاری 88 میلیارد دلار، یکی از پررونق‌ترین بازارهای جهان بوده است. رشد شتابان بیش از 60 درصد ظرفیت جهانی نمک‌زدایی، نه تنها حکایت از سهیم شدن دریاها در تأمین آب شرب کانون‌های جمعیتی سواحل دارد، بلکه گویای زوال تدریجی کیفیت آب‌های داخلی نیز می‌باشد. پیش‌بینی افزایش دما و تقلیل بارندگی در افق 2050 در بیست کشور واقع در شمال آفریقا و غرب آسیا (منطقه‌ی منا) منابع جدید آب را در این منطقه‌ی حساس جهان، کمیاب‌تر و دسترسی به آن‌ها را پرهزینه‌تر کرده و دولت‌ها را به ناچار به سمت گزینه نمک‌زدایی آب پیش می‌برد. در مقیاس جهانی، 38 درصد از حجم روزانه‌ی تولید جهانی آب نمک‌زدایی شده (2/65 میلیون متر مکعب) متعلق به کشورهای منطقه‌ی منا است و در محدوده‌ی جنوبی خلیج فارس، ظرفیت نصب شده نمک‌زدایی آب از 10 میلیون متر مکعب در روز فراتر است. پایه و اساس فرآیندهای گوناگون نمک‌زدایی آب، بر بهره‌گیری از انرژی استوار است و هر گونه تحلیل، سیاستگزاری و آینده‌نگری در موضوع نمک‌زدایی آب، بدون لحاظ سیاست‌های انرژی، ناقص خواهد بود. مهم‌ترین مسئله‌ی زیست محیطی این تأسیسات، شورابه‌های آن‌ها است که در گروه پساب‌های صنعتی قرار داشته و تخلیه‌ی گسترده‌ی آن‌ها به خلیج‌ها و سواحل مرجانی، سبب تغییر گونه‌ها و تهدید حیات آبزیان می‌شود. در سال‌های اخیر با توسعه و بهینه‌سازی فرآیندها، هزینه‌ی نمک‌زدایی هر متر مکعب آب، به حدود نیم دلار تقلیل یافته است، اما قیمت بازار آن هم‌ چنان در محدوده‌ی یک تا دو دلار باقی مانده است. ظرفیت نمک‌زدایی آب در ایران افزون بر 450 هزار متر مکعب در روز است که 65 درصد آن مربوط به آب شرب است. این مقدار کم‌تر از 2 درصد ظرفیت جهانی نمک‌زدایی آب است.

The global status of desalination: An assessment of current desalination technologies, plants and capacity

Seawater desalination in China: Retrospect and prospect

Change of editorial structure at Social Science & Medicine

In multi-effect desalination (MED) plants, the evaporators are usually of horizontal falling film type. For this kind of evaporators, high heat transfer coefficient can be achieved over low temperature difference and low spray density/liquid load. The current operating temperature range of MED plants is from 65 to 40 °C and researchers are trying to widen this range (85–5 °C), in order to enhance desalted water productivity. In this study, review of heat transfer coefficient correlations for falling films was carried out. The heat transfer coefficient prediction by different studies was compared with respect to film Reynolds number and working temperature. It was found that the empirical correlations by Fujita and Tsutsui, and Danilova et al. were better in evaluating heat transfer coefficient for MED application. It was concluded that increasing the top brine temperature (TBT) of MED evaporator is more beneficial than decreasing the lower temperature. The estimated heat transfer coefficient at 5 °C was 30–65% was less than that of heat transfer coefficient at 85 °C.KeywordsFalling filmHeat transfer coefficientHorizontal tubeMED

Assessment of an Integrated Gasification Combined Cycle using waste tires for hydrogen and fresh water production

Although current water desalination technologies are mature enough and advanced, the shortage of freshwater is still considered as one of the most pressing global issues. Therefore, there is a strong incentive to explore and investigate new potential methods with low energy consumption. It is well-known that polymer hydrogel network has the ability to absorb water via swelling. In the case of polyelectrolyte hydrogels, the charges localized on the polymer chains, which mainly drive the swelling pressure inside the hydrogel, can also separate added salt via charge-based selectivity (Donnan exclusion). When combining this material with a temperature-sensitive polymer, the heat generated by solar energy can trigger the desorption process via conformational change of polymer chains. Hence, hydrogels designed from both materials, polyelectrolyte and thermo-responsive polymer can reduce the salinity of water, such as brackish water by means of reversible thermally-induced absorption and desorption desalination processes. In addition, the desorption process can also be achieved based solely on a polyelectrolyte hydrogel system by altering the ionization of charges within the hydrogel via pH. In this thesis, hydrogel-based water desalination process were developed using acrylic acid (AAc)/sodium acrylate (SA)-based polyelectrolytes as the charge-based separation function, alone or with a combination of N-isopropylacrylamide (NIPAAm) as thermo-responsive comonomer. In the latter case, a series of chemically cross-linked polymeric hydrogels were synthesized via either free radical-initiated copolymerization or reversible addition-fragmentation chain transfer (RAFT) polymerization, thus realizing different macromolecular architecture. According to the nature of hydrogels, the reversible sorption/desorption state were triggered by either chemical stimulus (pH), or physical stimulus (heat) as the thermo-responsive polymer introduced into the hydrogels. In detail, the effect of hydrogel composition as well as the influence of the macromolecular architecture on the swelling/deswelling behavior for the synthesized hydrogels were studied. For this, their properties including their responses to external stimuli were investigated, and their ability to desalinate brackish water as well as the effciency of such desalination process were evaluated. Generally, the results demonstrated correlations between macromolecular architecture of the network structure and their performance in the proposed desalination process, such as salt rejection and desalination capacity. Moreover, the potential of the best performance materials for applications was also discussed.

As freshwater resources progressively decline, desalination capacities around the world are projected to increase. However, high electricity consumption costs hinder the broader development of desalination plants. A promising solution to offset a portion of these costs is to enable water distribution system operators (W-DSOs) to offer the flexibility of their water desalination plants in electricity markets. This article proposes a model to integrate the available flexibility of water desalination plants in W-DSOs operation and optimize their participation in electricity demand response (DR) and frequency regulation markets. The proposed model co-optimizes the operation of desalination plants with variable speed pumps and water storage tanks in order to optimally allocate the available WDS flexibility between the day-ahead energy and frequency regulation markets. The proposed model takes into account the hydraulic operating constraints of the WDS, thus ensuring the delivery of DR and regulation services in the markets while supplying the water demand at the desired pressure. In addition, the proposed model considers the unavailability of freshwater resources when providing flexibility services to the grid, thus enabling W-DSOs to balance their profits against water shortages. The numerical studies, conducted on a test 15-node water network, show that the proposed model effectively utilizes the operational flexibility of desalination plants to offer DR and regulation services in the markets, considering the hydraulic constraints of the WDS, freshwater availability conditions, and desalination plants’ freshwater recovery rates.