Research
9.13.2024: We are in the process of updating this page! For more details on our current research, please reach out to Prof. Straub and his students or check out our recent publications. Thank you for your interest in our work!
Worldwide, 3.6 billion people are living in areas that experience water scarcity at least one month per year, and this figure is expected to increase to as much as 5.7 billion people by 2050 according to the United Nations. Alongside growing issues of water scarcity, current global energy demands far exceed the capacity for sustainable production, with more than 85% of energy production worldwide provided by fossil fuels.
The challenges of water and energy supply are closely linked. Water treatment and distribution systems currently account for around 4% of energy consumption in the United States, and this number is expected to grow as energy-intensive water production methods, such as desalination, are further expanded. Similarly, more than 40% of U.S. water withdrawals are made by the energy sector with more water being needed as unconventional energy sources, such as shale gas, are exploited. Both water and energy will become even more critical resources as demand grows due to economic growth and climate change.
Innovative water treatment and power generation technologies will contribute to the portfolio of tools needed to address the challenges at the water-energy nexus. Our research group works to develop environmental technologies that can operate more efficiently and with greater versatility than state-of-the-art systems. To accomplish this, we conduct work across scales from small-scale materials design to laboratory-scale testing to system-level optimization. In general, our research is divided into the following subgroups:
- Dense polymer membranes
- Pressure distillation
- Gas separation
Membrane-based processes at the water-energy nexus
Systems utilizing membranes hold great promise in addressing water- and energy-related challenges. The introduction of reverse osmosis for desalination in the 1970s initiated a more than 80% decrease in the energy consumption of desalination, paving the way for expanded use in water-strained regions. The advantages of membranes processes—high efficiency, compact systems, and modular operation—can be leveraged to not only further improve desalination, but enable a wide range of advanced water treatment and power generation systems.
Advanced water treatment processes (e.g., reverse osmosis, forward osmosis, membrane distillation)
We conduct research to improve the performance of emerging water treatment processes. These processes can be driven by hydraulic pressure (reverse osmosis), salinity (forward osmosis), or heat (membrane distillation). We are particularly interested in developing membranes and process designs that can address issues related to selectivity, fouling, and energy consumption. Through these investigations, we work to develop the next generation of water treatment processes.
Power generation systems (e.g., thermo-osmotic energy conversion and pressure-retarded osmosis)
Underutilized sources of energy, such as low-grade heat and salinity gradients, are abundant and have the potential to sustainably supply massive amounts of power. In the case of low-grade heat, enough energy is available in the United States to theoretically power more than 10 million homes, but actual utilization of low-grade heat is limited because current heat-to-electricity energy conversion technologies are expensive and inefficient. We work on developing a new technology, called thermo-osmotic energy conversion, to harvest energy from low-grade heat using hydrophobic nanoporous membranes. We are specifically interested in improving the process by developing new membranes and exploring process configurations that can enhance efficiency. We also have experience in other membrane-based power generation processes that can generate power from salinity gradients.
Related Publications:
- Straub, A.P., Yip, N.Y., Lin, S., Lee, J., Elimelech, M. “Harvesting Low-Grade Heat Energy Using Thermo-Osmotic Vapour Transport Through Nanoporous Membranes.” Nature Energy 1, Article Number: 16090 (2016).
- Straub, A. P., Deshmukh, A., Elimelech, M. “Pressure-Retarded Osmosis for Power Generation from Salinity Gradients: Is It Viable?” Energy & Environmental Science 9, 31-48 (2016).
- Straub, A.P., Yip, N.Y., Elimelech, M. “Raising the Bar: Increased Hydraulic Pressure Allows Unprecedented High Power Densities in Pressure-Retarded Osmosis.” Environmental Science & Technology Letters 1, 55–59 (2014).
Materials design for environmental applications
Rapid innovations in materials science will facilitate dramatic improvements in environmental technologies. Our group is interested in leveraging materials design for a variety of water-related applications. In this area, we have previously worked to surpass the selectivity limits of osmotic membranes using a new class of vapor-gap membranes with hydrophobic nanopores. These membranes improve upon current polymeric membranes to provide distillation-quality water (including near complete rejection of neutral solutes!) without the high energy consumption that is associated with traditional thermal processes. Beyond this work, we are exploring the use of nanomaterials and electrochemistry to enable tunable selectivity, contaminant degradation, fouling relief, and microbial inactivation.
Related publications:
- Lee, J., Straub, A.P., Elimelech, M. “Vapor-gap membranes for highly selective osmotically driven desalination.” Journal of Membrane Science 555, 407-417 (2018). .
System-scale optimization for enhanced efficiency
While insights from bench-scale experiments are critical for materials development and proof-of-concept testing, real membrane systems are implemented in full-scale systems utilizing large membrane modules. Thus, the ability to probe behavior in large-scale systems is necessary to yield insights into the overall performance of membrane systems. We use computational modeling approaches, guided by experimental results, to simulate the performance of full-scale systems. These approaches allow us to understand the efficiency of a system and systematically analyze the impact of various parameters on full-scale performance.
We have previously used module-scale modeling to determine the viability of emerging membrane-based processes, such as pressure-retarded osmosis, and we have also used these methods to gain insights into the optimal configuration of thermo-osmotic energy conversion. We continue to examine both water treatment and power generation applications using advanced system-level models.
Related publications:
- Straub, A.P., Elimelech, M. “Energy Efficiency and Performance Limiting Effects in Thermo-Osmotic Energy Conversion from Low-Grade Heat.” Environmental Science & Technology 51, 12925-12931 (2017).
- Straub, A. P., Lin, S., Elimelech, M. “Module-Scale Analysis of Pressure-Retarded Osmosis: Performance Limitations and Implications for Full-Scale Operation.” Environmental Science & Technology 48, 12435-12444 (2014).
- Lin, S., Straub, A. P., Elimelech, M. “Thermodynamic Limits of Extractable Energy by Pressure-Retarded Osmosis.” Energy & Environmental Science 7, 2706-2714 (2014).