We currently focus on several applications of energy and mass transport with broad applicability for sustainability:
Boiling of water in porous copper with tailored microstructure. [Palko et al., Appl. Phys. Lett. 2015]
Some of our current research projects are in the following areas:
Thermal management for energy efficiency and electronics cooling
Energy storage for renewable generation and electric vehicles
Thermal Management for Energy Efficiency and Electronics Cooling
Boiling in Porous Media
The potential for heat transfer via boiling in porous media is remarkable. However, the intertwined energy and mass transport processes involved are complex and currently not adequately understood. We use novel experimental methods to elucidate fundamental mechanisms of boiling in thin porous layers. We're exploring measurements of the transient distribution of vapor in thin porous structures with controlled microstructure using approaches such as high-speed imaging and electrical resistance tomography. We're also designing experiments to measure key bulk transport properties, in-situ, during boiling. We're using these insights to develop new porous materials with optimized boiling performance and integrate these into microfluidic two-phase heat exchangers for high heat flux and geometry constrained applications.
Laser micromachined diamond heat spreader with integrated thin porous copper. [Palko et al., Adv. Func. Mater. 2017]
Energy Storage for Renewable Generation and Electric Vehicles
Suppressing electrolyte depletion in an electrochemical cell [Palko, Hemmatifar, et al. J.Power Sources 2018]
Improving charge/discharge response of batteries and supercapacitors
Improved electrochemical energy storage has remarkable potential to enable expansion of renewable energy generation and vehicle electrification. Porous electrodes are essential in a wide array of energy storage devices including batteries, fuel cells, and supercapacitors as well as other electrochemical and electrokinetic applications. We explore the optimization of electrokinetic transport in these systems and the interaction of transport processes and material modification for improving their energy and power density and robustness while lowering their cost. The animation here shows an example of these interacting transport effects simulated in a charging a supercapacitor electrode. The electrode has a very high conductivity, as is usually the case. This favors charging of the electrode near the separator. As charge is stored on the electrode (red curve), a corresponding number of ions are removed from solution, lowering its conductivity (blue curve). The resulting low conductivity of the solution slows charging response of the cell and creates high electric fields. We're developing approaches to alleviate this problem and other limitations to rapid charging of batteries for electric vehicle applications. We also explore the design of electrodes using low cost materials for grid applications of energy storage.
Thermal Energy Storage for Concentrating Solar Collectors
Solar energy is one of the fastest growing sources of energy but faces a significant challenge due to its intermittency. The ability to store collected solar energy would allow for much expanded use. We are developing technologies to efficiently and economically store energy from concentrating solar thermal collectors that harvest solar energy as heat. We use solid/liquid phase change to store and recover large amounts of heat at high density with low temperature loss. The stored thermal energy is useful for a variety of processes such as desalination.
Water is one of the grand challenges of this century. Two-thirds of the world's population experiences water scarcity for at least one month each year. Demographic trends and climate change are expected to exacerbate this problem. We work on a number of solutions to this challenge. These include advanced, high-efficiency thermal desalination approaches and electrochemical methods for removal of ionic contaminants. One focus is the removal of nitrate ions from drinking water. Nitrate is a pollutant of major concern worldwide and is paricularly prevalent in agricultural regions like here in the Central Valley of California. We develop technology to remove nitrate using chemically functionalized, high surface area adsorbents that are electrically regenerated. Advanced technologies like these offer hope to solve some of the most vexing problems in water treatment.
Nitrate removal from water using electrically regenerated adsorbents [Palko, Oyarzun, et al., Chem. Engr. J. 2018]
Additive manufacturing offers the opportunity to revolutionize production processes, but there are serious hurdles to adoption. Optimizing processes for resolution, surface finish, and reliability are particular challenges, relying largely on laborious trial and error. A large class of rapid manufacturing techniques relies on the thermal processing of materials initially in powder form (e.g. selective laser melting, SLM; electron beam melting, EBM; and selective laser sintering, SLS). We are developing mesoscale multi-phase thermal analysis approaches to allow optimization of these techniques.
The research is being led by the Palko Group (PI: Dr. James Palko).