If you study the working solar heat systems currently in use in Europe they all have shading controls to regulate how much sunlight is gathered. You must be referring to early American experiments because the rest of the world is forging ahead with solar thermal projects tht work.
Given how much of our energy use is directed towards heat production it makes more sense to create this heat directly. Measurements have shown solar thermal is 3X as effective in using solar comparredto a photovoltaic cell.
For low temp residential use, heat can be stored in insulated water containers. Low heat is defined as below the boiling point of water. Hot rocks or hot water storage is already a well known application in passive solar houses. Other storage solutions for heat above boiling point of water are being developed.
I had exprresed doubt about solar food cookers for when hot meals after sun down was required. I totally forgot about hay box cookers.
Glaubers salts have been used for a decade that I know of for heat storage and molten sodium is already used as a heat transfer medium in reactors. It is also used in non nuclear process for heat treating. Outdoor enthusiasts are probbly familiar with the phase change chemicals used in hand warmers.
You can use solr heat instead of a microwaave or electric stov to recycle them.
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