Nanostructured Energy Systems Labs (NESLabs)

Critical Need: Development of an inexpensive and high performance heat-powered cooling system greatly expands utilization of solar-thermal energy and low-grade waste heat for cooling buildings and process fluids and improves the economics of energy efficient combined cooling, heat, and power (CCHP) systems. Two-thirds of the fuel used in the world is wasted in the form of heat. Solar energy is harnessed with only close to 20% efficiency and the rest becomes waste heat. Thus, efficient utilization of low quality heat has a revolutionary impact on our future energy economy and carbon emission.



Project Innovations + Advantages: Absorption refrigeration systems (ARS) are fundamentally attractive for our future energy economy because they can convert low quality heat energy to cooling at the highest efficiency compare to other technologies.
 
A typical ARS consists of large heat exchangers that constitute most of the system size and cost. The transport processes within the heat exchangers are responsible for their bulkiness. In this work, nanoengineered membranes are implemented to greatly enhance the transport processes. The membrane-based heat exchangers are integrated together into new configurations with significantly higher surface area per volume compare to the existing technology. The new system configuration along with the advance material and manufacturing technologies that the new generation ARS benefits from promise an inexpensive, reliable, and low maintenance ARS.

The latest experimental data on laboratory-scale system elements suggest that the heat exchangers of a high performance ARS can be made at an order of magnitude smaller size and cost compare to the existing systems. Also, the volume of the Li-Br solution in the new generation system is an order of magnitude less than that of the existing systems. 




Critical Need: Direct methanol fuel cell (DMFC) is the most promising type of fuel cell for portable applications and, to the best of our knowledge, the only fuel cell that has been successfully commercialized. High energy density of methanol, facility of its storage, and its direct oxidation on the anode catalyst are the main reasons for the great potential of DMFCs as an alternative energy source for portable applications. The existing DMFC membrane electrode assemblies (MEAs) deliver a low power density (an order of magnitude less than the hydrogen fuel cells). At the heart of the problem are deficiencies of the existing MEAs that suffer from
a) slow kinetics of methanol electro-oxidation on anode,
b) limited operating temperature,
c) significant methanol permeation through the membrane (i.e. fuel crossover), particularly at high fuel concentrations, and
d) high water permeation through the membrane and cathode water congestion.

Project Innovations + Advantages: In a recent study Moghaddam et al. (“An Inorganic-Organic Proton Exchange Membrane for Fuel Cells with a Controlled Nanoscale Pore Structure,” Nature Nanotechnology, vol. 5, pp. 230-236, 2010) demonstrated that through tailoring the material construct in atomic level the common deficiencies of the fuel cell MEAs could be alleviated. The membrane developed by Moghaddam et al. was engineered to achieve high power density with dry H2 supply at very low humidity ambient. The membrane delivered one order of magnitude higher performance than in the previous studies. The focus of this effort is to dramatically enhance kinetics rate through surface/interface nano-structuring and tailoring the proton selective layer construct to minimize fuel and water transport.



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