Grantee Research Project Results
Final Report: Safe Drinking Water from Atmospheric Moisture using Desiccants and Solar Radiation
EPA Grant Number: SU834741Title: Safe Drinking Water from Atmospheric Moisture using Desiccants and Solar Radiation
Investigators: Immethun, Cheryl , Davies, Caroline P , Mitchell, James
Institution: University of Missouri - Kansas City
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2010 through August 14, 2011
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2010) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
The primary Phase 1 design objective was to create an affordable, portable device capable of collecting water chemically through the use of desiccant materials and recovering it with only solar radiation. With the use of a Fresnel lens, solar radiation will heat a desiccant material to its point of regeneration (the temperature at which water is desorbed or released from solution) within a sealed box. The sealed box will have one exit hose leading to a simple condenser, which then leads to a sealed water collection bucket. As the box is heated, the air expands and water leaves its solution in the form of vapor. Both of these processes increase vapor pressure within the box, creating a pressure differential with it and the sealed bucket. The vapor flows naturally from high to low pressure as it tries to equalize the differential. As it moves through the intercooler, the extreme temperature difference causes the water vapor to condense and flow into the sealed bucket.
To accomplish the objective, research was conducted on various desiccant materials. Because of a general lack of publically available hydration and dehydration characteristics of desiccant materials, a list of desiccant candidates was compiled. A testing apparatus that creates a controllable stream of moist air was constructed and all desiccants were tested for their hydration characteristics. Variables in this experiment were temperature, humidity, and airflow. Dehydration tests were then conducted in a wide range of temperatures to determine dehydration rates at various temperatures. Based on the results, two desiccant materials were selected for further use in this project. These desiccants were then researched for all aspects of human and/or environmental toxicity, chemical stability, and availability.
Following desiccant selection, a solar heated desiccant containment box was designed and constructed. Considerations in box design were that it must be as compact as possible, durable at any temperature, easily and inexpensively produced, and easy to operate. Research that went into the creation of the box first included identification of materials that would be most thermally conductive, while remaining durable in any environment. Using this information and information from desiccant tests, finite element analysis software was used to test the heating characteristics of various box designs. Once adequate designs had been rendered they were constructed without the use of tools (aside from tin snips). This was a step necessary to ensure the devices could be recreated and implemented throughout the world.
Preliminary field tests were undertaken using the solar heated box and a Fresnel lens. Variations in box design tested included: box size, box material, box angle relative to the sun, box insulation, and heating plate design. Box design was varied according to results of preliminary field tests.
The project’s next objective was to design a simple condensing mechanism. The mechanism’s function is to act as an ideal surface for condensation to occur. For the mechanism to be effective, it should stay much cooler than the incoming heated vapor flow. Said large temperature difference is the natural mechanism by which this system condenses heated vapor into clean drinking water.
By examining cooling properties of various materials, Aluminum was an obvious choice for its properties. Through research it was decided that the ideal condenser would have the maximum surface area of aluminum as well as be designed to stay cool and be cooled with a simple solar fan if necessary. The time, skill, and cost required to build a mechanism with said attributes was reasonable within the U.S.; however, this was not the case in developing areas, especially rural ones like this project’s phase 2 implementation location. In an effort to reduce waste as well as save time and money this project will use an automotive intercooler from a turbocharged car as the condenser.
Final field tests will be carried out in San Antonio, TX in April 2011. Results, including water quality information, will be presented at the 2011 National Sustainable Design Expo.
Summary/Accomplishments (Outputs/Outcomes):
Because of their superior hydration characteristics and chemical stability, Lithium Chloride (LiCl) and Calcium Chloride (CaCl2) were selected for further use in this project. From the results of testing both compounds in a range of conditions, hydration and dehydration rates were successfully developed for both LiCl and CaCl2. Using this information, the amount of desiccant needed to collect X amount of water was calculated and applied to box design.
Using finite element analysis, a scalable box was designed that will be most effectively heat-able by a Fresnel lens. Sheets of aluminum and steel were chosen to construct the box and a single glass pane was included in the lid. Preliminary box testing at 39°N and a low winter sun angle has produced 400°F throughout a portion of the solar heated box. This temperature provides for rapid dehydration of both compounds. To improve heat retention, box size was minimized and insulation was added.
This newest design will be tested in early April 2011. This full device trial will use desiccants and fully test the condensation system.
Conclusions:
This project was successful in identifying and thoroughly testing desiccant materials. Rates of dehydration were developed for both compounds throughout the temperature range attainable by the device. Hydration characteristics were successfully determined for both compounds. With this, water collection systems can be optimized for environments.
This project was also successful in designing a solar heated box capable of reaching temperatures required to dehydrate desiccants quickly, which then allows for maximum hydration time. The entire water collection device has been constructed; however, a full field test has not been carried out at this point. Although the device works theoretically, it is prudent to withhold ultimate conclusions until final field trial results have been obtained and analyzed.
The system was successfully designed to be both affordable and portable. If final field tests are successful, this will aid in the creation of devices to serve both the developed and developing regions.
Supplemental Keywords:
Desiccant, water vapor, evaporation, evaporate, condense, condensation, drinking water, water, watershed, groundwater, war, pipeline, treatment plan, sustainability, green, solar radiation, solar energyThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.