High Density Heat Storage for Homes

The United Kingdom has an objective of reducing fossil fuel emissions to 80% lower than
1990s’ levels by 2050 mandated by the UK Climate Change Act [1]. With 47% of total final
energy demand in the UK as of 2012 attributable to heating demand [2], methods to
decarbonise the UK’s heating supply are essential to hitting emissions targets.
Phase change material (PCM) based heat storage, a subset of energy storage, presents a
unique opportunity to temporally displace the consumption of energy from its production,
providing a solution to reduce the economic costs of transitioning to a low carbon energy
supply.
This thesis details experimental and computational fluid dynamic modelling investigations,
(with Ansys Fluent), using temperature dependant properties of the melting process of
beeswax and paraffin wax in several isothermal configurations intended to emulate underfloor
heat storage using phase change. The effect of changing a key parameter of these models,
the mushy constant is also investigated and analysis is performed with dimensionless and
non-dimensionless variables.
Experimentation quantified the melt process of these materials with temperature sensors,
thermal and visual camera imagery for validation of the generated models.
Moderate agreement is found with the latter paraffin wax model and experimental data
however beeswax models were found to be invalid with larger domain models having issues
with model convergence and mesh resolution / time step insensitivity.
Experimentation had success with visual and thermal imaging despite thermal attenuation by
the vessel walls; thermal imaging was found to be unable to visualise small length scale
phenomena.
The temperature sensor matrix had some success despite over-prediction of melt fraction due
to lack of sensors at the vessel edges. In addition, these sensors contributed negatively to
isotropy due to heat losses through the wires from the melting material.