Heat collection options: heat transfer from solar collectors

Some requirements we can note on concentrators and heat transfer systems are:

• An absorber converts focused solar radiation to heat in the receiver.
  High concentration ratios are in particular needed for air based systems.
• With a stationary circulation loop, solar tracking axes must be around the absorber.
• A forced circulation system requires pumps or fans which can tolerate high temperatures.
• A natural circulation system (thermosyphon system) requires the storage to be at elevated heights.
• The heat extraction to the cooker can be direct (by conduction) or indirect (by separate heat transfer loop)   

We have experiences with several types of heat transfer options, both between the heat source and the storage
and between the storage and the cooker (heat transfer options)