Grantee Research Project Results
Final Report: Concentrated Solar Distillation as a Means to Purify Saline/Brackish Water
EPA Grant Number: SU834294Title: Concentrated Solar Distillation as a Means to Purify Saline/Brackish Water
Investigators: Matsumoto, Mark , Chen, Alexander , Salinas, Christopher , West, Elizha , Johnson, John , Tam, Kawai , Chen, Luke , Chen, Wesley
Institution: University of California - Riverside
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2009 through August 14, 2010
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2009) RFA Text | Recipients Lists
Research Category: Nanotechnology , P3 Awards , Sustainable and Healthy Communities , Pollution Prevention/Sustainable Development , P3 Challenge Area - Air Quality , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
As the population of the world continues to grow, the need for potable water also will continue to grow. To meet this need in areas of the world with underdeveloped infrastructure, new sustainable methods of preparing potable water are being sought. Thermal energy has the ability to both purify water with respect to bacterial content as well as to separate purified water from salts. As part of Phase I of the EPA P3 competition a Fresnel lens has been tested as a means of delivering thermal energy for producing drinkable water. Both direct and indirect methods of heat delivery with respect to water production and purification have been studied. Furthermore, small scale experiments were performed to determine the degradation of the lens when exposed to ultraviolet radiation.
Summary/Accomplishments (Outputs/Outcomes):
Initial experiments focused on the ability of the lens to deliver enough energy to produce water with minimal salt content. Raw sample waters were prepared using quantities of Epsom salt (MgSO47H2O) dissolved in purchased distilled water. Three separate samples of increasing concentration were introduced batch wise into a constructed boiler unit and attached condenser. The raw samples and collected product were analyzed using a conductivity meter. The three raw samples had measured concentrations of 710, 2812, and 5526 ppm. The collected product waters all showed salt concentrations of approximately 0 ppm.
A second parameter to be tested was the use of a secondary solar collector versus direct heating of the boiler unit by the Fresnel lens. Secondary collection would allow multiple lenses to apply solar energy to a single boiler unit. In terms of scalability this would allow greater energy input with respect to the boiler unit and pumping system, which encompasses the bulk of the per unit costs. Preliminary testing of the secondary receivers showed an inability to deliver enough energy to bring the raw sample water to a boil.
The lenses also were tested with respect to degradation under exposure to direct ultraviolet radiation. The lenses under consideration were acrylic, which can discolor over time in direct sunlight. In order to simulate solar exposure, the lenses were placed in a fume hood with constant ultraviolet radiation delivered via a 15 W UV lamp. Prior to placement in the fume hood the three lenses were placed within an enclosed space and their luminosity with respect to a constant light source at a fixed distance was determined. The luminosity was determined using a lumen meter purchased from Fisher Scientific. The three lenses then were placed in the fume hood and removed once per month for 3 months. During each removal, the luminosity of each lens was once again tested and compared to the initial readings. The lenses then were replaced back into the fume hood. All readings showed approximately equal values with respect to time spent under ultraviolet radiation.
Conclusions:
With respect to the lens’ ability to deliver energy sufficient to purify test samples, it was found that direct heating of the boiler unit was able to purify the water and eliminate the salt content from tested samples. The secondary off-boiler solar receivers were unable to produce the heat necessary to produce purified water. Further testing is required utilizing sufficient insulation to account for convective heat losses from the receiver. The degradation experiments showed no decrease in the amount of light produced from the lenses but more extensive testing and equipment are required to meet the American Society for Testing and Materials (ASTM) specifications. These specifications also are required in order to produce commercial products in the United States.
Proposed Phase II Objectives and Strategies:
As part of Phase II of the P3 competition, further improvements in the production capabilities will be examined. These improvements will focus mainly on the distillation and condensation of the contaminated water. Special focus will be applied to the possibility of producing a multi-stage flash system to allow for maximum heat recovery as well as the possibility of designing a true flow-through system. More comprehensive lens degradation tests also will be performed using the Q-Lab, QUV Accelerated Weathering Tester. Finally a two-access solar tracking system will be designed and used for automation of the device.
Journal Articles:
No journal articles submitted with this report: View all 4 publications for this projectSupplemental Keywords:
Solar distillation, Fresnel lens, renewable energy, drinkable water, concentrated solar energy, solar collector, basin solar still,Relevant Websites:
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The 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.