A thermoelectric composite sandwich structure comprising: two prepreg composite face sheets (12, 18); an integrated honeycomb core assembled between the face sheets (12, 18), the honeycomb core comprising: a plurality of core elements; each core element having a first side substantially coated with a negative Seebeck coefficient conductive material each core element having a second side substantially coated with a positive Seebeck coefficient conductive material a plurality of electrical connections for connecting in series the coated first side to the coated second side; wherein a temperature gradient across the honeycomb core generates power; wherein (i) the plurality of core elements are bonded together with a core adhesive; (ii) the coating on the first side of each core element forms a plurality of first spaced gaps; (iii) the coating on the second side of each core element forms a plurality of second spaced gaps; and (iv) the first spaced gaps on the first side of each core element do not overlap with the second spaced gaps on the second side of the same core element. two prepreg composite face sheets (12, 18); an integrated honeycomb core assembled between the face sheets (12, 18), the honeycomb core comprising: a plurality of core elements; each core element having a first side substantially coated with a negative Seebeck coefficient conductive material each core element having a second side substantially coated with a positive Seebeck coefficient conductive material a plurality of electrical connections for connecting in series the coated first side to the coated second side; wherein a temperature gradient across the honeycomb core generates power; wherein (i) the plurality of core elements are bonded together with a core adhesive; (ii) the coating on the first side of each core element forms a plurality of first spaced gaps; (iii) the coating on the second side of each core element forms a plurality of second spaced gaps; and (iv) the first spaced gaps on the first side of each core element do not overlap with the second spaced gaps on the second side of the same core element. a plurality of core elements; each core element having a first side substantially coated with a negative Seebeck coefficient conductive material each core element having a second side substantially coated with a positive Seebeck coefficient conductive material a plurality of electrical connections for connecting in series the coated first side to the coated second side; wherein a temperature gradient across the honeycomb core generates power; wherein (i) the plurality of core elements are bonded together with a core adhesive; (ii) the coating on the first side of each core element forms a plurality of first spaced gaps; (iii) the coating on the second side of each core element forms a plurality of second spaced gaps; and (iv) the first spaced gaps on the first side of each core element do not overlap with the second spaced gaps on the second side of the same core element. (i) the plurality of core elements are bonded together with a core adhesive; (ii) the coating on the first side of each core element forms a plurality of first spaced gaps; (iii) the coating on the second side of each core element forms a plurality of second spaced gaps; and (iv) the first spaced gaps on the first side of each core element do not overlap with the second spaced gaps on the second side of the same core element.