Date of Graduation

12-2014

Document Type

Thesis

Degree Name

Bachelor of Science in Chemical Engineering

Degree Level

Undergraduate

Department

Chemical Engineering

Advisor

Penney, William Roy

Abstract

In arid regions of the United States potable water is a valuable resource and is sometimes produced using energy intensive processes by removing salts from brackish water. Task 4 provides a solar option for producing potable water from brackish water; in competing in Task 4, H2OGS has developed a simple, cost effective solar desalination process to provide these regions with necessary, potable water. H2OGS’ design takes into account WERC requirements, including cost, energy usage, worker safety, and easily obtained materials. U.S. government regulatory requirements are also taken into account as the proposed location for this process is Alamogordo, New Mexico. H2OGS’ design consists of a thin plate-type solar evaporator and also a thin plate-type condenser. Black-painted corrugated galvanized steel panels were used to construct the evaporator and condenser. The black-painted evaporator panels are protected from atmospheric convection by a six mil polyethylene film, commonly used for greenhouses. Radiant energy from the sun passes through the polyethylene film and is absorbed by the black-painted panel. Brine is sprayed onto the back side of the panel via a nozzle located at the top of the unit. As the brine runs down the evaporating face, it is evaporated. The warmed, evaporated brine gravity drains to an insulated holding tank from which it moves to the next evaporating stage to be further concentrated. The evaporated water is condensed on additional corrugated steel plates located opposite the evaporating face. Because this plate is shielded from direct sunlight, the evaporated water is condensed by convection to the atmosphere and drained into a holding trough at the bottom of the unit where it is pumped to a potable water storage tank. The brine effluent that remains after leaving the final still unit is transported to a solar pond where salts crystalize and are removed by manual raking from the evaporation basin. This basin is designed to be 3’ deep by 45’ wide by 180’ long and will evaporate the remaining 20% of the bring effluent and allow for crystallization and recovery of the salts. After air drying, the salts are sold. The health and safety of all individuals involved in the H2OGS project is important during the construction and the life of the project. The individuals involved in construction will be trained on the proper safety precautions before construction begins. Warning labels concerning the temperature of the unit will be printed on the solar brine concentrator. Regular and preventative maintenance will be performed by a trained individual(s) to keep the unit running safely and efficiently. The public involvement plan is crucial to the success of the solar brine concentrator in Alamogordo, New Mexico; this technology would be competing with the city’s current technology. Meetings will be held to inform the community of the benefits and disadvantages of both technologies. These meetings will help educate the community and address any community concerns. A training session will be held concerning operation, maintenance, and safety precautions of the facility. The H2OGS full scale unit will produce 25 L/day/person (1/2 of the UN minimum per day) for a community of 500 people or 12,500 L/day (3,300 gpd, 1.2 million gpy). The installed cost of the unit is $100,000. With capital cost amortized over 10 years the yearly capital charge is $10,000. With community volunteer labor the operating costs are $10,000/yr. With 15,600 L/day of brine feed the produced salts will be 198 lb/day (66,000 lb/yr). At a salt netback price of $0.33/lb, the benefits of salt sales are $21,780/yr. The salt sales will thus cover both capital charges and operating costs, assuming volunteer labor. This optimistic scenario will produce water at zero cost to the community. The current Alamogordo water cost for large volume users is $7.91/k gal23. With operating labor included at $50,000/yr the cost of water will increase to $40.01/k gal. The following report provides a detailed proposal of the solar brine concentrator, including design concepts, experimental results, health safety and environmental concerns, and a public involvement plan. While the design is recommended for Alamogordo, NM, H2OGS has designed the unit to be implemented anywhere there is a real need for potable water near a usable brine source.

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