Executive Summary
Water remains a very essential resource in human life. Water has been used for agricultural purposes to supplement the natural rains, for a long time. Many parts across the world have reported water shortages, which is partly a consequence of changing environmental conditions. Water demands have risen sharply in some areas around the world because of rising population and environmental problems such as lack of rains, which have led to the drying up of water channels. Water purification is becoming an essential practice as many more people (more than a quarter of the world’s population) continue to suffer from “inadequate fresh water supply” (Saggie et al.; Leblanc & Andrew, 249). Water purification and other management options have played a key role in the alleviating of water shortages and the associated problems. Yet in the wake of many options of water purification systems, there is need to identify the most efficient and the most cost efficient among the many. In addition, not all systems can be employed anywhere, first because they differ in application and procedure, and secondly, some will be suited in specific areas because of the available resources that present the make them more viable options. The efficiency and applicability of the method of purification is an important consideration every time such a project is being desired. More importantly, pure water is necessary in animal life in order to avoid the water borne diseases. The applicability of Solar- Powered Desalination system as a method of water purification has been tried for water because of the opportunity it present to save cost and improve on efficiency of desalination. Moreover, because the method makes use of solar energy, it would be best fitted in areas where there is stable solar power. Such places include Saudi Arabia and other parts of the Middle East. The Middle East is part of the arid areas that have been suffering from water shortages because of the changing weather conditions across the globe (Leblanc & Andrew, 249).
Introduction
Shortage of water has necessitated the exploration of techniques needed to utilize the scarcely available water resource. Increased demand for water in the whole world has been caused a number of factors, among them rise in population and destruction of existing water sources. Particularly, the demand of water in Saudi Arabia was expected to reach “3000 million m³/year by the year 2010” (Water technology). The increased shortage for water would cause serious trouble as people fight over the available limited water resources. These calls for innovative techniques that will help alleviate the water shortage, in addition to boosting the efficiency and reducing the cost of the existing methods. Water desalination techniques have been employed in Saudi Arabia following indications of “chronic water shortage” and rising population (Water technology). This paper explores the application of Solar- Powered Desalination method and how it can be successfully employed in Saudi Arabia while incorporated into Multi-stage Flash (MSF). Although other techniques have been explored, they have challenges such as high cost and demand “extensive pre-treatment” of water (Water technology). The paper provides the background, the recent attempt for the project application, and conclusion. The background provides the information on what would make the application of such a project important in the Saudi Arabia case. The recent attempt presents a recent case scenario for application of the water purification method. A good alternative for renewable energy desalination technique that “compete(s) economically” with Reverse Osmosis (RO) is the use of thermal energy from solar, for distillation by evaporation (Sagie, Eli and Weinberg, 1).
Background
Water is very essential in the livelihood of the animal and plant termed as the “living organisms” (Leblanc and Andrew, 249). Fresh water is also very essential for sustaining life because it plays a very vital role in the success of agriculture. Water shortage is likely to spark chaos as people fight for the limited available water resources for agricultural and other use. Many people (over a quarter of its population) are faced by the danger of illnesses following “Inadequate fresh water” supply (Leblanc, and Andrew, 249). There has been “chronic water shortage” in the Middle East which demands serious solutions so as to continue sustaining lives amidst rising population (Water technology). Saudi Arabian Central Department of Statistics projected that the population of Saudi Arabia would rise to more than “29 million people by 2010” and the demand for water would rise to over “3000 million m³/year by the year 2010”, taking into consideration that the consumption per person per day was 300 liters (Water technology). Water shortage in the Middle East has already caused a lot of difficulties and application of innovative solutions to proper management of the situation is necessary to avoid the associated problems. Already, there are no stable water sources in the Middle East and therefore water is presently not sufficient for agricultural, domestic or any other use. Saudi Arabia lacks lakes, rivers and other sources of water that would alleviate the shortage. The condition of shortage is worsening as the population continues to rise in the area demanding for more water. Reliance on traditional sources of water and especially pure water proves to be difficult in this situation, and this calls for modern methods that could alleviate the shortage by managing the available water sources and water itself. Serious demand for water in the Middle East has called for need for application of innovative methods and means of alleviating the shortage problem. In addition, management of the existing water resources is very essential towards the efficient utilization of the water resources. It is important to note that wastage of water can be avoided through efficient management of the resources such as water recycling and treatment. In turn, the need for water management systems and methods, calls for extensive and sufficient knowledge of the available channels or options of water management. Water management systems are not only essential, but economical and more efficient option such as desalination by “nanofiltration membranes” (Escobar & Coleman) must be explored to harness the associated benefits. The likelihood of utilization of Modern methods such as usage of solar powered desalination systems that “compete economically” with other methods such as RO has been explored (Sagie, Eli and Weinberg, 1).
Recent Attempt
The efforts for water purification through desalination has increased as can be exemplified by the dramatic rise of the number of desalination plants being planned across the globe. There have been attempt to apply some other techniques on water purification too. The most important consideration is the fact that each of the methods has their limitations as well as their advantages. “Electro-Dialysis (ED)”, “Reverse Osmosis”, and “Multiple-Effect”, among others are the several proven methods of water purification (Leblanc & Andrew, 249). Multi-stage Flash and Multi-Effect evaporation are the mostly applied thermal desalination techniques. The efficiency of the method is an important competitive factor over others.
“Chronic water shortage” has risen in Saudi Arabia amidst rising population. Saudi Arabian Central Department of Statistics projected that the population of Saudi Arabia would rise to more than 29 million people by 2010. The demand for water would rise to over 3000 million m³/year by the year 2010, taking into consideration that the consumption per person per day was 300 liters. This shortage gave rise to the need to invest in desalination project by the country’s supplier of water to the municipalities, i.e., Saline Water Conservation Corporation (SWCC). The company invested in Shoaiba Desalination Plant which is currently largest in the world (Water technology). In order to allow the solar powered generation technique to be competitive “economically” with RO, the first step of generation of electricity by using renewable energy source, and then using this electricity to “power generation” would be eliminated (Sagie, Eli and Weinberg, 1).
Multi-Stage Flash Distillation has remained crucial in the provision of pure water around the world, accounting for more than “85% of the world’s desalinated water” (Water technology). Much of the previous demand for water in Saudi Arabia has been alleviated by the availability of desalinated water supplied by SWCC and more desalination facilities are underway. The method for desalination that is applied in the SWCC is the Multi-Stage Flash Distillation (MSF) process. Application of this method has been of “interest” in the Middle East market, and has been favored by the fact that the” price of the units” has deteriorated thus becoming important for large corporations. Large-scale application of the method in Middle East has been enhanced by the fact that they have relatively “low maintenance” and higher efficiency (Water technology). Alternative technologies such as reverse osmosis have lost popularity in the some parts of Middle East because of the “extensive pre-treatment of raw sea water intake” that these technologies demand (Water technology). This project was estimated to cost a total of $ 1.06 billion and serve a population of about 1.5 million. Challenges of other processes such as generation of poisonous by-products in the reverse osmosis process and generation of pollutants and their being “sucked into the process” need to raise interest for exploration of other options of desalinating water (Water desalination process, 4).
Water from sea is heated by the means of tubes contained in brine heaters in a distiller. The water is converted into steam in a low-pressure vessel. The heater is supplied with steam from steam power plant or a bypass station. The water then is changed to steam. The steam is cooled by means of water (in feed to the brine heater) passing over the heat exchanger tubes. A system of multi-distillers, each with lower atmospheric pressure than the preceding one, is used. The method has a number of limitations. These include the fact that the number of multi-level distillers is limited to the temperature difference between the brine heater and the final condenser at the cold end of the plant. Rising the temperature may increase the possibility of increased efficiency of the method, but also may raise the risk because of the possibility of accelerated corrosion of metal surfaces. Use of corrosion resistant metals coatings as well as matching the steam cycles and optimum plant power with MSF performance, can help in minimizing the possibility of dangers.
One of the problems of the usage of fuel power in water purification plants lies in the implications of rising prices or the cost of operation. Rising oil prices have been witnessed at times which present cost challenges to the power plants utilizing this form of energy source. In addition, environmental concerns are becoming a very vital issue in the current society, with requirements that companies must lower their levels of green gas emissions and reduce the amounts of other associated pollutants released in the air. In additions, interests have shifted on “lowering traditional energy requirements for desalination” through utilizing renewable energy sources such as solar power (Leblanc & Andrew, 250). The solar power techniques provide an efficient and cost effective route to desalinating water in Saudi Arabia, because the country receives enough isolation. Such options as thermal desalination process have gained ground with possibilities of engineering techniques on reducing challenges presented by other options, through efficient process design, performance analysis and consideration of the possibilities to save on cost. Integration of the previous thermal solutions with the solar energy possibilities present another option of saving on the cost. The heat sources from the boilers utilizing oil energy to heat steam can be integrated with solar ponds, solar thermal collectors as well as solar-thermal heat sources to save on costs and energy. The possibility of coming up with a solar-thermal desalination unit with a single-unit flash (unit where water is converted to steam) has been explored through experimentation. The success of such a process will present a great opportunity for the water desalination plants and those interested because it comes with a number of advantages. Modeling has proved that less thermal energy would be consumed by using several numbers of stages although many stages would raise the capital requirements. The method also has some options that could be explored in the incorporation of the solar power energy into the MSF models discussed earlier on. The once through desalination process (SP-MSF-OT) present the lowest specific energy consumption as compared to the conventional MSF (MSF-C) and the mixing MSF system (MSF-M). The SP-MSF-OT does not have a heat rejection stage available in the Conventional model which also incorporates a heat recovery section. In the mixing model, a mixing box replaces the heat rejection and involves the mixing of incoming feed brine with part of hot brine from the final stage of heat recovery.
Solar desalination systems may utilize various components that use solar energy. Solar ponds traps and store energy from solar radiation and use this to supply energy when combined with long-term energy supply sources. Utilization of salinity-gradient ponds (SGSP) presents a viable option for a solar desalination project and the technology has been proven as “most promising” (Leblanc & Andrew, 251). These pods present an opportunity to saving the cost of the whole project because they material used to construct them are readily available from the local scenery. The cost of setting up more desalination plants in places like Saudi Arabia where they are demanded would be lower than other systems. Coupling a solar pond to a Multi-stage Flash desalination system (SP-MSF-C) may present cost saving options for Multi-stage Flash desalination. Therefore clear understanding of how the Multi-stage Flash desalination systems work is very essential.
Solar-thermal desalination systems are also very useful in the salinity mitigation scheme because it can lead to reduction of the number of evaporation ponds used in the project. This is through producing fresh water through desalinating of the salty groundwater to produce fresh water while the saline solution is employed in the production of salt in the process.
Solar desalination systems would be probable in the case of Saudi Arabia because the country still demands water for use. More importantly, the country would save a lot of resources which would go to the many planned desalination plants to alleviate the pure water demand in the country. Replacing of previously used desalination mechanisms may be difficult, and therefore it may become necessary to continue employing them, while making sure that present and future plans build on solar desalination plants. It has also been found that when power costs exceed a certain value of over (7.1 cents/kWh), solar Multiple Effect Distillation (MED) systems are more economical compared to Reverse Osmosis option (Sagie, et al.).
Conclusion and Recommendation
Water demand across the globe has come as a result of many factors, among them, increasing population. Environmental changes have resulted to a decrease in the water sources and channels. Management of the available water resources therefore is a crucial issue. The availability of fresh water has been challenged by increasing environmental pollution. There has been attempt to invest in various technology in order to not only increase the supply of clean water, but to increase the efficiency of such mechanisms. A number of factors must be considered when applying various options that are available in water purification technology. Some methods can not be applied everywhere, while application of others is favored by the availability of options such as favorable environmental conditions. The importance of the efficiency of water purification systems, as well as cost and capital cannot be ignored. There is increasing need to invest in water desalination systems for water purification.
Middle East has explored a number of water desalination methods among them Multi-stage Flash desalination methods. This system has played an important role in the desalination of water across the globe, with over 85% of desalination water being resultant to the process. Middle East and Saudi Arabia in this case continue to suffer high water demand and hence there is need to invest in desalination techniques which are more efficient and cost effective. MSF has proven to be efficient in the production of desalinated water, but still is dogged with high energy usage that can be saved with alternative solar options. The recent options in this field have been the trial for application of the solar desalination method. One route to application of this is the combination of the MSF and the solar method, where the latter is included to replace the oil energy usage. Extensive research into viable application of the solar options into existing desalination systems such as MSF and MEE is required to harness the possible benefits as theorized. There is evidence that cost and efficiency benefits would result from application of solar desalination systems and therefore there is need to invest in the application of these systems to alleviate the demand for pure water in Saudi Arabia. Saudi Arabia is more suited for such technologies because it is located in an area of high solar radiation. There is evidence that MEE are more cost effective that MSF (Wade; Leblanc and Andrew, 250) and therefore there is a necessity to investigate the application of solar options in MEE.
Works Cited
Escobar, Isabel and Coleman, Maria. “Desalination using forward osmosis with nanofiltration membranes.” Faversham House Group. 2009. Web.
Leblanc, Jimmy and Andrew, John. “Solar- Powered Desalination: A Modeling and Experimental Study.” Foxit Software Company, 2007.
Sagie, Dan, Eli, Mandelberg, and Weinberg, Joseph. Rotemi Co. “Commercial Scale Solar-Powered Desalination.” 2009. Web.
Wade, Niel. “Energy and cost allocation in dual-purpose power and desalination plants.” Desalination 123 (1999): 115-125. 20
Water Desalination Report 2009 45. 26. AMTA Conference. Web.
Water technology. “Shoaiba Desalination Plant, Saudi Arabia.” 2009. Water Technology. Web.