Building accessory structure

A building accessory structure applicable to an external area of a building, the building accessory structure comprises:

• a plurality of the solar thermal collectors, each of the solar thermal collectors comprising:
• at least one heat absorbing plate, comprising at least one first slab and a plurality of first engaging parts connected with the first slab;
• and
• at least one heat insulating plate, comprising:
• at least one second slab;
• and
• a plurality of second engaging parts connected with the second slab, wherein each of the second engaging parts comprises an extending groove and a hook groove, and each of the first engaging parts comprises an extending section and a hook section, each extending section is engaged with the corresponding extending groove, and each hook section is engaged with the corresponding hook groove in order to attach the heat absorbing plates to the heat insulating plates, and a gap is maintained between the first slab and the second slab to form a heat collecting channel, that allows a heat transfer medium to flow through, and the heat conductivity of the heat absorbing plate is at least 30 times greater than the heat conductivity of the heat insulating plate;
• and
• at least one frame configured to hold the solar thermal collectors, which are disposed in parallel to each other in the frame.