Dr Mark Baxendale Project Abstracts
BSc Project Abstracts
Thermoelectric properties of materials
Thermoelectric generators convert waste heat into usable electrical energy. The primary figure of merit for a thermoelectric material is the Seebeck coefficient, the voltage measured across a sample in response to a small temperature gradient. This experimental project aims to measure the temperature variation of the Seebeck coefficient for some new candidates for thermoelectric energy generation. The data will be interpreted in terms of the fundamental underlying thermal and electrical phenomena. The objective is to assess whether the new materials could be used to generate usable electrical power at room temperature from the small temperature gradients of ~10⁰C encountered in everyday life, for example from computers, body heat, or car exhausts. The project requires basic laboratory skills and elementary knowledge of condensed matter physics.
Beyond the detailed balance limit for the efficiency of silicon solar cells
This project follows the landmark derivation of the detailed balance limit for silicon solar cell efficiency by Schockley and Queisser [1]. The aim is to extract the underlying assumptions made in the calculation and to explain qualitatively why the theoretical maximum efficiency ~40% is much less than the thermodynamic limit (95%). The project will then experimentally measure the efficiency of contemporary silicon solar cell; then you can attempt to explain why the efficiency of an actual solar cell is somewhat less that the detailed balance limit. You can then comment on the strategies being employed by designers to bring the efficiency closer to the thermodynamic limit. The project would suit those who are comfortable with both theory and experiment, and have a basic knowledge of condensed matter physics.
[1] W. Schockley and H.J. Queisser, ‘Detailed Balance Limit of Efficiency of p-n Junction Solar Cells’, Journal of Applied Physics 32, 510 (1961)
MSci Review Project Abstracts
Thermoelectric power generation
There are many sources of heat that dissipate energy to the environment, for example computers, car exhausts, humans. A thermoelectric generator is a device that employs semiconductor materials to generate electrical energy from the heat flowing in a temperature gradient. These all seem to work a high temperature and none at the modest absolute temperature and temperature gradients that are typical of the sources of low-grade heat. This review project will investigate the basic principles of thermoelectricity, look the requirements for materials for thermoelectric generator construction, and review the strategies used to achieve low temperature operation.
Modelling Climate Change
International agreements have achieved a consensus figure of 2⁰C for the acceptable increase in the average temperature of the surface of the Earth relative to the pre-industrial level by the year 2100. Whether current greenhouse gass emission levels are compatible with this target figure is a matter of some debate. The modelling of climate systems, the greenhouse effect, and feedback mechanisms which can either accelerate or decelerate global warming all feed into to simulations. This review will focus on the various climate models in common usage, critically evaluate the strengths and weaknesses, and assess the reliability of the predictions.
MSci Research/Investigative Project/ MSc Project Abstracts
Complex thermoelectric materials
Thermoelectric materials convert waste heat to usable electrical energy. The primary figure of merit for these materials is the Seebeck coefficient, the voltage measured across the sample in response to a small temperature gradient. This project aims to synthesise and measure the Seebeck coefficient of some new candidates for thermoelectric energy generation and to make a comparison with that of the best known thermoelectric material, bismuth telluride (~100 uV/K at room temperature). These new materials are based on a carbon nanotube network and a conducting polymer - the flows of electrical and thermal current follow complex filamentary paths. The temperature variation of the Seebeck coefficient will be measured and the behaviour interpreted in terms of the underlying electrical and thermal phenomena. The aim is to develop a new category of thermoelectric devices capable of harvesting energy from sources of waste heat encountered in everyday life, e.g. computers, body heat, car exhausts. The project requires basic laboratory skills plus condensed matter and statistical physics knowledge.
