PAM Review Energy Science & Technology

Editorial

Jurgen Schulte — Mon, 01 Jun 2020 11:23:43 +1000

PAM Review is the peer-reviewed student research journal produced in the School of Mathematical and Physical Sciences at the University of Technology Sydney. The journal was created to provide a student-centered authentic learning experience in a theory heavy course to help facilitating Faculty of Science graduate attributes and the University’s model of teaching.

The student journal was first introduced in 2014 in the second-year physics course Energy Science and Technology. The course covers fundamentals of thermodynamics and statistical mechanics and their applications in current and emerging technologies.

Increasing the efficiency of a Peltier device by assessing the thermal performance of liquid-cooled microchannel heat sinks

Lauren Sharpe, Navil Burhanuddin, Tiana Majcan, Jonathan Rebolledo — Mon, 01 Jun 2020 00:00:00 +1000

Water is, arguably, Earth's most valuable and vital resource. Devices that extract water from the atmosphere have been intensely researched as a means of harvesting potable water in environments where it is otherwise scarce. One such device is a Thermoelectric Cooler (TEC); a device that utilises the Peltier effect to cool a system. TECs are a promising solution for atmospheric water generation (AWG) over their competitors due to their simplicity and refrigeration capabilities. Despite these advantages, TECs are still considered mostly inefficient as they demand relatively high costs and energy consumption. This meta-analysis focuses on optimising the efficiency of small-scale Peltier devices. It explores the means of optimising the liquid cooled heat sink by using a specific flow field microchannel configuration such that less pumping power is required to push the coolant and more energy can be saved. A combination of optimal operating current of the Peltier device and of a novel flow liquid-cooled microchannel heatsink configuration with bifurcated fins using Galinstan as a coolant promises a significant increase in water production per unit of energy consumption for the AWG system.

Meta study on the optimisation of thermoacoustic cooling systems for efficiency and cooling load

Daniel Holland, Nicholas Berryman — Mon, 01 Jun 2020 12:56:16 +1000

The emerging field of thermoacoustic cooling systems (TACS) has been explored in recent years, combining the disciplines of acoustics and thermodynamics to provide an alternative to mainstream cooling technologies. This hybridised system allows a system of travelling or standing waves to absorb and release thermal energy at different points spatially, which is then harnessed to produce a cooling effect. This meta-analysis will focus on analysing parameters such as stack plate spacing and selection of a working fluid, in order to optimise the system. As this will directly impact the temperature gradient, as the temperature gradient is the core operator in the cooling process. The above parameters were examined with a combination of comparative and normalisation techniques, to synthesise data from varied experimental sources and produce accurate conclusions. The parameters investigated had differing effects on the system with regards to COPR and maximum cooling power, due to cooling power and input acoustic power increasing at different rates. The meta study concluded that a ratio of parallel-plate stack spacing to thermal penetration depth of (equation) was ideal for maximising cooling load, where as a ratio of approximately (equation) was ideal for achieving maximum COPR.

A parametric analysis on PEFCs for high-temperature applications

Filip Bojko, Giorge Gemisis, James Mitchell, Christopher Parker — Mon, 01 Jun 2020 15:04:17 +1000

Polymer Electrolyte Fuel Cells (PEFCs) are an increasingly significant facet of modern renewable energy and transportation, providing an electrochemical method of energy generation with high power density, thermal properties, and efficiency. PEFCs tend to increase in efficiency as temperature increases but detrimental effects begin to occur, including membrane degradation and dehydration. These effects are unfavourable in the design of optimised fuel cells as they can result in reduced efficiency and lifetime. Current PEFCs are in a state where they are commercially viable but have a very limited temperature operation region (<80°C). This meta-study analysis presents research around expanding the operational temperatures of PEFCs through a parametric analysis of active cell area, phosphonic acid content, and organic/inorganic fillers. This analysis finds an increase in proton conductivity for PEFCs at higher temperature by using phosphonic acid functionalised membranes with maximised degree of phosphonation (up to 1.5 DP). It was also found that using ionic liquid functionalised carbon materials as fillers was an effective strategy to enhance the proton conductivity of PEFCs in a higher temperature environment while also providing increased thermal stability of the membrane. Additionally, higher thermal efficiency and power density may be achieved by increasing temperature and humidity to maximise proton conductivity towards theoretical maxima dictated by the active cell area, which was found to peak at 36 cm².

Meta-Study on Integrated Cooling of Modern Integrated Circuits using Microfluidics

Ben Andrew, Jesse McNamara, Michael Karanikolas — Tue, 02 Jun 2020 09:37:23 +1000

The substantial increase in the transistor density of integrated circuits (ICs) in recent times has allowed considerable improvements in computing power. With increasing transistor and power density, the heat produced by modern ICs has increased significantly. This in turn has negative effects on the performance, reliability, and power consumption of the ICs. A solution to the IC’s complications caused by overheating is integrated cooling, in which cooling fluid is delivered through microchannel heat sinks on the backside of an IC. This meta-study will investigate two microfluidic cooling technologies. First, implementing varied size microfluidic channels close to the silicone substrate of the IC. Additionally, a micro-pin fin heat sink is integrated into the ICs’ fluidic microchannels. Different sized pin fins were used, to achieve a wider understanding of the application of pin fins in microfluidic cooling and compare the thermal performances of each cooling method. Integrated cooling subverts the need for suboptimal thermal interfaces and bulky heat-sinks, as well as reducing the intensity of localised hotspots commonly present in high-power electronics. Further, by locating the main heat exchange medium closer to the die of an IC, we reduce the number of thermal interfaces. This meta-study suggests that cylindrical micro-pin fin arrays with pitch longitude and latitude of 60μm and 120μm, are more thermally efficient than plain microfluidic cooling channels.

Meta-analysis of concrete as a thermal energy storage medium

Guina Mourad, Harry Lennox, Madeline Turner, Madison Traynor — Tue, 02 Jun 2020 09:47:52 +1000

Solar energy is a renewable energy source however sunlight is only available during limited hours in the day. Researchers are looking towards an efficient energy storage system to ensure constant energy output. Concrete can be used as a filler material in a solar thermal energy storage system. This meta-study compared the heat capacity and thermal conductivity of concrete to other solid materials and concrete aggregates, allowing for the viability of concrete storage systems to be examined. The heat capacity of concrete was 5-10% higher than the comparative solid materials like brick and sand. Additionally, concrete without cement replacement materials were found to be more thermally conductive than concrete with added fly ash, blast furnace slag or silica fume with conductivity decreasing between 81-87%. However, concrete with the supplementary cementitious materials possess a higher heat capacity than concrete without cement replacement with capacity increasing by 25% at 30% replacement by fly ash with a grain size 300-600µm. When compared to the energy efficiency of other thermal energy systems, a concrete thermocline is shown to be less efficient than a molten salt two-tank energy storage system by less than 5%. Therefore, while concrete is a viable solid filler material in thermal energy storage systems, a molten salt two-tank thermal energy storage system is marginally more efficient. However, a partial cement replacement by supplementary cementitious materials can extend the effectiveness of the concrete thermal storage.