Seawater could help solve water woesSeawater could help solve water woes, but at what price? By ANDY REID South Florida Sun-Sentinel August 06. 2007 7:37AM Small plastic bottles with labels proclaiming "a taste of Florida's future" contain drinking water mined from the sea. Filtered and treated at a desalination plant that supplements supplies in the Florida Keys, the bottled water is a crystal-clear marketing gimmick to show that taking the salt out of seawater offers a drought-proof solution to the state's water woes. But a few hundred miles from the Keys, Tampa's troubled desalination plant - built to become the largest of its kind in North America but still struggling to run at full capacity - stands as a monument to how costly and uncertain the investment can be. During a drought that has led to the toughest water restrictions in South Florida history, water managers have renewed their call to explore using the sea to help meet water needs. Fort Lauderdale is among the sites where the South Florida Water Management District proposes a pilot program to test tapping into ocean water. "We are sucking Florida dry right now," said Arlyn Higley, director of operations for the Florida Keys Aqueduct Authority. "Desalination is the way of the future." Desalination is not a new practice; the Keys have relied on it for more than a century. The first desalination plant in the United States was built in the 1840s in Key West to serve troops at Fort Zachary Taylor. Today, a desalination plant on nearby Stock Island, which produces the bottled water, and another on Marathon, serve as a backup water supply for the southern Keys in case hurricanes or other emergencies damage the freshwater pipeline from Florida City. Those plants, can produce about 3 million gallons of water a day, compared with the 17 million gallons a day the Keys can pump from freshwater wells. The earliest desalination involved heating saltwater, collecting the steam, and then condensing the steam for drinking water. Today's plants pump water at high pressure through membranes with hair-thin fibers that filter out the salt, producing fresh water that can be used for drinking water. Fishing boats and barges plow through the water in Safe Harbor Channel beside Stock Island, the same water the Florida Keys Aqueduct Authority taps to supply its desalination plant. The plant, on a finger of land jutting into the Atlantic Ocean, was rebuilt in 1998 at a cost of $8.3 million. It houses 440 membrane-packed cylinders that filter seawater, pumped through at 1,000 pounds per second by high-powered diesel engines. Thirty percent of the seawater emerges from the process as usable freshwater, while the salty leftovers get pumped into a 210-foot-deep disposal well. It costs about $5 per 1,000 gallons to produce the desalinated water, compared with less than $1 per 1,000 gallons to tap into conventional sources, Higley said. "The energy cost is much more expensive than just pumping it out of the ground," Higley said. "That's why we don't run this plant any more than we absolutely have to." The New Water Supply Coalition - made up of water management agencies, including in South Florida and the Keys - is lobbying Congress for legislation to help finance the construction of desalination plants, to follow the lead of countries such as Israel, Australia and Saudi Arabia, which already convert seawater to drinking water. "We in the United States are behind the curve," coalition director Hal Furman said. "When you have high growth rates ... coupled with droughts, it is natural that you are going to have to look for alternative water supplies." The South Florida district in 2001 teamed with Florida Power & Light Co. to explore building desalination plants beside electric power plants, with the hopes of limiting energy costs and using seawater already pumped in to cool the power plants. A list of 23 possible sites stretching from Fort Pierce to Miami ultimately was trimmed to three: beside FPL's Lauderdale and Port Everglades power plants, as well as one in Fort Myers. Eye-popping construction estimates - $276 million for Port Everglades, $148 million for Lauderdale and $91 million for Fort Myers - have kept the plants from being built. In Fort Lauderdale, the proposals compete with less expensive alternatives such as tapping into the Floridan aquifer, a deeper, more plentiful supply than the more commonly used Biscayne aquifer, and using water from a Palm Beach County reservoir. The city contends that the district should conduct a pilot program at the proposed sites to get a better handle on the costs and how that system would fit with the city's current water facilities, city spokesman Chaz Adams said. "It could potentially have regional benefits," Adams said. Tampa's problems with desalination leaves communities leery, said Ken Herd, director of operations and facilities for Tampa Bay Water, which owns the plant. Tampa opened a plant in 2003 that was supposed to produce 25 million gallons of water a day, but it has been plagued with operational problems. Pre-treatment of the water drawn from Tampa Bay failed to filter out sediment, algae and other small particles that damaged the salt-filtering membranes. Switching contractors and fixing deficiencies cost $48 million and pushed the total plant price to $158 million. The plant now produces about 18 million gallons a day that gets mixed into the drinking water supply. Tampa Bay Water hopes to have the plant at full capacity by the end of the year, Herd said. "It has huge political risks," Herd said about policymakers pursing expensive desalinization alternatives. Along with the cost, desalination plants face environmental concerns. Getting rid of the briny leftovers could threaten fisheries and coral reefs. Environmental activists are fighting a similar waste product disposal problem for a new Lake Worth water plant that would tap into the Floridan aquifer and dump wastewater a mile off the coast. "Any waste we produce, we have to be careful where we put it," said Ed Tichenor, director of Palm Beach County Reef Rescue. No desalination plants are on the drawing board for South Florida through 2025, said Mark Elsner, water district director for alternative water supplies. That could change, he said, as South Florida's population pressures start to outweigh desalinization cost concerns. In the 1960s, Higley said periodic water "outages" helped persuade the Keys to invest in desalination. "People don't like to pay a lot of money for something they think is readily available," Higley said. "(People) are going to have to pay a lot more for water." --- Information from: South Florida Sun-Sentinel,
https://www.sun-sentinel.comhttps://www.gainesville.com/article/20070806/APF/708060581 A STUDY OF HYBRID FUEL CELL/DESALINATION SYSTEMS 03-AS-007 Principal Investigator Dr. Said Al Hallaj and Prof. J. Robert Selman, Illinois Institute of Technology, USA Ph.D. Scholarship Recipient (First one and half year) Mr. Nasser Dabaiebeh, Jordan Research Partners Prof. Mohamed Ali Darwish, Kuwait University, Kuwait Statement of Work: The goal of this project is to study the technical feasibility and suitability of hybrid integrations of fuel cells with desalination processes. Potential limitation of the current available fuel cell systems may result in shifting the project focus to small and medium sized desalination systems. Both seawater and brackish water desalination will be considered. Practical combination of fuel cells and desalting systems will be evaluated. Objectives: 1) Review the state of the art of fuel cell technologies and development trends. 2) Review different desalting systems for integration with fuel cells. 3) Identify the thermal and electrical availability/requirements for various operating conditions of different fuel cell and desalination processes. 4) Provide an assessment study of the technical feasibility and suitability for hybrid integration of fuel cells with power generation (PG) and water production, and also to verify the possibility of including cool-house refrigeration or airconditioning applications. 5) Investigating various modes of operations of hybrid power/desalination plants under different scenarios taking into account daily and seasonal variation in climate and power/water demand ratios especially for the MENA regions. 6) Develop technically feasible hybrid systems of fuel cells, power generation systems, cool-house refrigeration systems and desalination systems. 7) Develop mathematical models for fuel cell and desalination systems. Tasks Based on recommendations of the PAC members the project was split into two phases. Phase-A, which is the subject of this proposal, will focus on the conceptual study and understanding of appropriate fuel cell and desalination systems and arrive at technically feasible hybrid systems. Develop mathematical models for fuel cell and desalination systems. Phase B will focus on optimization through simulations of proposed hybrid systems in Phase-A while keeping in mind the importance of minimum cost of water and electricity for successful implementation of the concept. Phase A: Task 0: A preliminary outline of the project will be laid out with table of contents and short description of the project tasks and deliverables taking care of the above mentioned objectives. Specification sheets will be developed for both desalination and fuel cells, which shall include all the relevant parameter and information that are required for integration. A similar sheet will be developed for mechanical vapor compression and absorption cooling as part of the refrigeration systems. This task will be executed at the beginning of the project and will be conducted in communication and coordination with MEDRC. Task 1: Overview of Fuel Cell Technologies: This task will include an overview of fuel cell technologies with emphasis on the types of fuel cells, thermal and power availability for various operating conditions and the market availability. Some of the fuel cells being currently used are broadly classified into low temperature fuel cells and high temperature fuel cells. Proton exchange membrane (PEM) fuel cells (low temperature fuel cells), which are operated around 80oC, may be used to supply the energy needs of small and medium scale desalination units. The high temperature fuel cells are molten carbonate fuel cells (MCFC) and solid oxide fuel cells (SOFC), which operate at about 650oC to 1000oC, can be considered for cogeneration and larger desalination applications. Of these the MCFC are commercially available and research is being carried out for SOFC to be available for stationary applications. Having a thorough background of the fuel cells, various possible desalination processes such as electrodialysis (ED), vapor compression (VC) (thermal and mechanical), reverse osmosis (RO), multistage flash (MSF), multi effect evaporation and humidification/dehumidification processes will be considered for possible combination. This involves an in-depth understanding of the various systems and studying similar types of works done in this area. Task 2: Overview of desalination processes: In this task, different desalting systems for integration with fuel cells will be reviewed. The review includes:- i) The type of feed water to be desalted (seawater or brackish water). ii) The range of required energy and the mode of this energy (electrical, mechanical and thermal) at what temperature level. iii) Cooling water that may be required and. iv) Capacity and foot print size of the desalting unit. Only well proven type desalting systems are considered. Theses systems include:- 1. Electrodialysis for brackish water desalting by utilizing the DC current produced by the fuel cells. A rough relation between feedwater salinity and consumed power is to be presented. 2. Reverse Osmosis (RO) for desalting seawater or brackish water. RO can utilize the fuel cell main power output after its conversion to AC current. In case of gas turbines (GT) being combined with MCFC or SOFC, the GT output can be utilized to operate the RO system. In proton exchange membrane type of fuel cells, its thermal output can be utilized to heat the feed for RO system. 3. Conventional multi effect distillation (MED) (low temperature): In case of PEMFC, operating at 80oC-100oC, its thermal output can operate low temperature MED. 4. Mechanical vapor compression (MVC) desalting system: The main power output of the fuel cell can be used to operate MVC system. In the case of using PEMFC is used, its thermal energy can be utilized as auxiliary heat. If MCFC or SOFC are used and combined with a GT, the GT power can be used to run the MVC system. 5. Thermal vapor compression system: This can be operated at a moderate steam pressure of 5-20 bar, generated by heat recovery steam generator (HRSG). Hot gasses from MCFC or SOFC can operate the HRSG. In case these fuel cells are combined with GT, the gas turbine exhaust can be used to operate the HRSG. 6. MSF system operates with steam at a maximum temperature of 120oC, and can be generated by HRSG as in item 5. 7. Humidification-dehumidification desalting systems. In case proton exchange membrane system is used, the low temperature energy can be used to humidify the air, and this air can be dehumidified by exposing it to ordinary water, then the condensed vapor would be the product. Task 3: Review of typical power/water cogeneration requirements: This task will include a comprehensive study of projects and also an assessment of the actual demands of power and water for different climatic and water conditions. Specific areas under the MENA region will be considered as case studies. Task 4: Technical Feasibility: - a review of various cogeneration techniques and an evaluation and comparison with respect to the size and system specifications will be made for both desalination techniques as well as fuel cell systems. Various system specifications, components and the parameters involved will be studied. Based on such kind of evaluation, analyses will be made for the best way of practically integrating cogeneration technology. Task 5: Control Strategies: From the above analyses, various control parameters will be studied and depending on the most feasible modes/schemes of operation will be considered. Such analysis will take into account the seasonal and climatic variations and changes in power/water demand ratios. Task 6: Mathematical Models: Develop mathematical models for fuel cell systems and desalination processes useful for optimization studies in Phase-B. Status Draft final report submitted
https://medrc.org/research/Statusofprojects2007.pdf