Grantee Research Project Results
Final Report: Solar-Powered Membrane System for Emergency Drinking Water Supply
EPA Grant Number: SU835528Title: Solar-Powered Membrane System for Emergency Drinking Water Supply
Investigators: Mi, Baoxia , Birney, Catherine , Manzi, Elizabethe , Lee, Michael , Fiedler-Ross, Vincent
Institution: University of Maryland - College Park
EPA Project Officer: Packard, Benjamin H
Phase: I
Project Period: August 15, 2013 through August 14, 2014
Project Amount: $14,714
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2013) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Air Quality , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
The objective of this project is to provide a supply of sustainable, clean drinking water for disaster-struck or off-the-grid areas by developing a novel, integrated, and portable membrane filtration system that is powered by solar energy. The novel membrane system will integrate two emerging membrane processes: forward osmosis (FO) and membrane distillation (MD), which allows us to use low-grade heat as the main form of energy input. The proposed system will have a number of salient advantages:
- Enhanced energy sustainability: The dual-stage FO-MD membrane filtration achieves energy sustainability by using a cheap and renewable energy resource: solar thermal. In addition, the input energy can be low-degree heat, such that a minimum of a 15oC temperature difference would be adequate to drive the process.
- High-quality product water: The high-rejection FO membrane retains most of the water contaminants in the first stage; the MD process further safeguards the effluent quality.
Description:
Unlike the widely used hydraulic pressure driven membrane processes (such as reverse osmosis), the FO process is driven by a natural osmotic pressure that is generated by a concentrated draw solution, thereby requiring no energy input except for that for pumping. FO is used in the proposed system to remove most contaminants from the feed water. The MD process is used to re-concentrate the draw solution and finally to produce clean water. MD utilizes temperature gradient, which generates vapor pressure gradient, to drive water molecules through the membrane. The required temperature gradient can be as low as 20oC. As a result, MD can be directly powered by renewable energy sources, such as solar energy, geothermal energy, and waste heat from power plants. Solar-powered membrane system for emergency drinking water supply 835528 Executive Summary-UMD The proposed research will potentially transform the current water purification technology by integrating the FO and MD membrane processes in a novel manner. Desalination and water reuse have become two of the final avenues for addressing water sustainability issues worldwide. However, current technologies require substantial energy inputs. In contrast, the proposed novel membrane separation system will minimize energy consumption and reduce greenhouse gas emissions by using renewable energy as opposed to fossil energy. Therefore, this system will potentially revolutionize the membrane-based water separation industry by drastically enhancing energy-efficiency and environmental friendliness. Developing a sustainable solution to water scarcity is a critical component of an overall national strategy of energy and environmental sustainability in the coming decades.
Summary/Accomplishments (Outputs/Outcomes):
We have successfully built an off-grid, portable solar-powered FO-MD membrane system for the Phase I project (Figure 1). The whole system is composed of two major units: one for water filtration and the other for solar energy collection. The water filtration unit is composed of one FO membrane module and four MD membrane modules. The FO membrane uses osmotic pressure naturally generated by a NaCl draw solution to filter pure water from the source water into the draw solutions, and subsequently the MD membrane uses temperature gradient as the driving force to filter pure water from the draw solution into the permeate, which is the final product of potable water. The solar collection unit fuels the water filtration unit by supplying solar thermal energy, collected with a solar thermal panel to generate the temperature gradient required for the MD to work. In addition, a photovoltaic (PV) panel harnesses solar energy to power four pumps, which circulate the source water, draw solution, potable water, and heating fluid through system.
Conclusions:
In this project, we successfully built a sustainable solar powered membrane system that can be used in a disaster-struck or remote area to supply safe drinking water without consuming electricity/ fossil fuels or releasing additional chemical waste and pollutants into the environment. The intended end users of this system are not only people who need an emergency water supply after disasters, but also small communities, such as single buildings on the University of Maryland campus, student housing, etc. As our system can also be installed in individual homes, we want to promote this system to everyone possible. Therefore, advertising is being actively done at the University of Maryland and at various conferences, such as the Water Resources Symposium being held in Washington, D.C. on April 4, 2014.
The expected environmental benefits of this Phase I project include minimal negative impacts to the environment and no production of carbon emissions or air pollution. Current small scale water purification systems, such as reverse osmosis, require a huge amount of energy from fossil fuels. The use of these fossil fuels releases pollutants into the air, which contribute to the greenhouse effect and climate change. The FO unit of our filtration process occurs naturally by osmosis, without the need of an additional energy source. The second unit, MD, does require energy, but will run off of renewable energy sources (e.g., solar energy). As the system is fueled by solar power only, no greenhouse gases will be released into the environment and there will be no depletion of limited fossil fuels.
Economically, this system requires little energy to run on and has no high-pressure pipes and pumps, making it inexpensive compared to other processes such as reverse osmosis. As this system is both environmentally and economically friendly, it is ideal for disaster affected areas. It can be set up quickly and easily for immediate relief to disaster victims. If applied on an industrial scale, this membrane system could work to provide water for entire communities in areas with scarce freshwater sources.
Journal Articles:
No journal articles submitted with this report: View all 3 publications for this projectSupplemental Keywords:
- Forward Osmosis – using a semi-permeable membrane, osmotic pressure drives the removal of water from dissolved solutes. Caused by a high-concentration draw solution (NaCl) relative to the feed solution, osmotic pressure produces a flow of water through the membrane into the draw solution.
- Membrane Distillation – using a hydrophobic membrane for the barrier between the liquid and vapor phases of water, a temperature gradient causes water vapor to pass through the membrane. A temperature difference of approximately 20 degrees allows for an adequate partial vapor pressure for water vapor to form on the opposite side of the membrane.
- Heat Exchanger – a metal capsule designed for efficient heat transfer. The shell and tube heat exchanger used in this system is composed of many tubes through which hot liquid flows to transfer heat to the surrounding liquid in the capsule.
- Solar Thermal Panel – by absorbing sunlight and solar radiation, this device collects heat. Using a glycol solution, the solar thermal panel directly uses sunlight to create a temperature gradient necessary for membrane distillation processes.
- Photovoltaic (PV) Panel – using multiple panels connected electrically, the system uses direct sunlight to generate power. The power is stored by a battery and is constantly being regenerated when the system is outdoors and facing the sun.
Relevant Websites:
Website: Baoxia Mi - Assistant Professor Exit
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.