Autonomous solar tracking in flat-plate photovoltaic panels using kirigami-inspired microstructures
There is disclosed Kirigami-inspired structures for use in solar tracking applications. When coupled with thin-film active materials, the disclosed microstructures can track solar position and maximize solar power generation. In one embodiment, there is disclosed a photovoltaic system comprising a single-axis, or multi-axis solar tracking structure comprising a support structure made of a flexible material having a defined unit cell structure, and a flexible photovoltaic cell disposed on the support structure. There is also disclosed methods of making such structures in which the photovoltaic cell is mounted to the support structure by a direct-attachment bonding processes such as cold-welding.
1. A photovoltaic system, comprising:
a solar tracking structure comprising:
a support structure comprising a flexible material having a unit cell structure defined by a pattern of openings in the support structure, wherein said pattern of openings comprises a cut length (L c ), an uncut length (L u ), and a spacing between cuts (W c ), which can be expressed in terms of the dimensionless parameters R 1 and R 2 where
R 1 =L c /L u and R 2 =L c /W c
wherein the support structure tracks a light source by tilting when stretched; and
a flexible photovoltaic cell disposed on the support structure.
2. The photovoltaic system of claim 1 , wherein the flexible material comprises a plastic material or metal foil.
3. The photovoltaic system of claim 2 , wherein the flexible material comprises a plastic material having a conductive metal coating on one surface.
4. The photovoltaic system of claim 3 , wherein the plastic material comprises a polyimide.
5. The photovoltaic system of claim 3 , wherein the metal coating comprises at least one metal chosen from Au, Ag, Pt, Pd, Ni, and Cu.
6. The photovoltaic system of claim 1 , wherein the photovoltaic cell comprises an active photovoltaic region comprising a flexible crystalline semiconducting cell.
7. The photovoltaic system of claim 6 , wherein the flexible, crystalline semiconducting cell comprises InGaP, GaAs, InGaAs, InP, or InAIP.
8. The photovoltaic system of claim 1 , wherein the photovoltaic cell is mounted to the support structure by a direct-attachment bonding process chosen from cold-welding, thermally assisted cold-welding, or thermo-compression bonding.
9. The photovoltaic system of claim 1 , further comprising an actuator operably coupled to the support structure, wherein the support structure and the photovoltaic cell change their shapes in response to a force applied by the actuator.
10. The photovoltaic system of claim 1 , wherein R 1 =R 2 .
11. The photovoltaic system of claim 1 , wherein the support structure has a thickness ranging from 25 to 100 μm; and the flexible photovoltaic cell has a thickness ranging from 2 to 10 μm.
12. The photovoltaic system of claim 1 , further comprising an optical collector or concentrator.
13. The photovoltaic system of claim 1 , wherein the support structure is a three-dimensional expanded mesh structure when stretched from a linear two-dimensional structure.
14. The photovoltaic system of claim 13 , wherein the expanded mesh is created by the pattern of openings in the structure.