Stabilising solar ponds by utilising porous materials

The linear instability of a solar pond containing porous material in the lower convective zone (LCZ) is investigated. It is found that, in general, for physically realistic values, solar ponds that contain porous material are more stable than ones that do not. Interestingly, it is found that the percentage of porous material contained in the LCZ does not stabilise the system in a linear fashion and, in particular, approximately 60% of porous material in the LCZ appears to optimise the maximum temperature that can be stored in the LCZ provided the proportion of heat flux extracted at the base of the pond, f, is held fixed at a physically realistic value of f=0.5. When f is varied it is found that there is a critical value of f = 0.6 below which inclusion of porous material stabilises the system but above which it does not.