Energy storage bed dynamics -the ever-expanding magnesium bed conundrum

In order to facilitate high penetration of renewable energy in to the grid, energy storage is needed to in order to better manage the supply and demand for the grid. Hydrogen offers a high energy density solution and, rather than storing the hydrogen as a gas at high pressures, solid state storage of hydrogen in a metal like magnesium offers a low pressure and low cost technology. The hydrogenation of magnesium is very exothermic (74.5 kJ mol-1) and the material is also being investigated as a thermal energy store (i.e. using the exotherm of hydrogenation to liberate the stored thermal energy back as heat at 400C).

A fear was that cycling a magnesium bed at high temperatures would lead to sintering and a loss of void space. However, the startling result was that the powdered magnesium bed when cycled at temperatures of 350-400C, rather than losing porosity, gained porosity. The form of the bed had changed from a loose powder to a metal porous plug which had swelled in dimensions to fill the available head space in the vessel. Further cycling at temperature below 350C results in the bed resorting back to a more densely packed loose powder.

The intriguing question is to uncover the fundamental mechanism(s) behind this process and to develop a predicative model based on the physical and chemical processes occurring. For the application, understanding these processes will enable optimisation of the porous structure for heat and mass flow; moreover, there is also concern the expanding bed may exert significant stress on the wall of the storage vessel eventually leading to failure of the vessel.

This challenging research project will develop new mathematical models based on the chemical and physical processes occurring in order to develop a model that simulates the expanding porous bed phenomenon. Some of these processes include: nucleation, growth of the metal hydride phase, crystal lattice expansion leading to defect formation, decrepitation, atomic diffusion and surface energy minimisation, annealing. The models developed will thus need to encompass a wide range of physical phenomena; the focus will be on partial-differential-equation/moving-boundary formulations, building on the established sintering literature but, for the reasons described above (specifically, to generate increased, rather than decreased, porosity), of necessity raising significant additional challenges. The project will accordingly equip the student with an unusually wide experience of experimental and modelling questions and of mathematical techniques, as applied in a context with clear energy and sustainability implications.


About the Energy Research Accelerator
The Energy Research Accelerator (ERA) is a cross-disciplinary energy innovation hub which brings together capital assets, data and intellectual leadership to foster collaboration between academia and business to accelerate the development of solutions to the global energy challenge. It will provide new buildings and cutting-edge demonstrators, develop highly skilled people and jobs, as well as new products and services to ultimately transform the UK’s energy sector. Building on existing programmes and academic expertise across the partnership, universities within ERA have committed over £2m for doctoral students as a critical part of the ERA skills agenda.
Delivered through Innovate UK, the government has committed an initial capital investment of £60m, and ERA has secured private sector co-investment of £120m. ERA’s initial priorities of Geo-Energy Systems, Integrated Energy Systems and Thermal Energy will help deliver the new technologies and behaviours that will open the avenues for its future development and demonstrate the transformative effect ERA can have across the energy spectrum.

Through the Midlands Energy Consortium (MEC), Midlands’ universities have already worked closely to deliver essential research and postgraduate skills - clustering energy research and development to deliver technologies capable of enabling the UK’s transition to a low-carbon economy. ERA is the next step along that journey to become a major hub for energy talent.

ERA is a key programme within Midlands Innovation - a consortium of research intensive universities which has the overall aim of harnessing the Midlands’ combined research excellence and industry expertise to play a critical role in tackling some of the biggest challenges facing the UK.

Summary: UK/EU students - Tuition Fees paid, and full Stipend at the RCUK rate, which is £14,296 per annum for 2016/17. There will also be some support available for you to claim for limited conference attendance. The scholarship length will be 3.5 years and the successful applicant will be part of the Energy Research Accelerator at the University of Nottingham (http://www.era.ac.uk/).