Efficiency restoration in a photovoltaic cell

Abstract

The electrical output efficiency of a photovoltaic thermal system can be restored from degradation due to light exposure by annealing a photovoltaic thermal cell at an elevated temperature. The elevated temperature at the photovoltaic thermal cell can be provided by redirecting the flow of a heat exchange fluid to bypass a heat exchanger unit. A boiler unit may be employed to provide additional heating of the heat exchange fluid during the anneal. Further, a variable configuration lid can be provided over a front surface of the photovoltaic thermal cell to control ventilation over the front surface. During the anneal, the position of the variable configuration lid can be set so as to trap heat above the front surface and to elevate the anneal temperature further.

What is claimed is: 
     
         1 . A method of operating a photovoltaic thermal (PVT) system comprising:
 providing a photovoltaic thermal (PVT) system including a photovoltaic thermal (PVT) cell configured to generate electricity and to provide a thermal output; and   annealing a photovoltaic material within said photovoltaic thermal cell at a temperature greater than 130 degrees Celsius for a duration of time.   
     
     
         2 . The method of  claim 1 , further comprising:
 operating said PVT system in an operational mode that generates said thermal output while a variable configuration lid on said PVT cell is in one position; and   changing a position of said variable configuration lid to a different position during said annealing.   
     
     
         3 . A method of operating a photovoltaic thermal (PVT) system comprising:
 providing a photovoltaic thermal (PVT) system including a photovoltaic thermal (PVT) cell configured to generate electricity and to provide a thermal output; and   circulating a heat exchange fluid through at least two different circulation paths in different operational modes, wherein said at least two different circulation paths include a first circulation path including a pipe through said PVT cell and a pipe through a heat exchanger unit in which said heat exchange fluid loses heat, and a second circulation path that includes said pipe through said PVT cell and does not include said pipe through said heat exchanger unit.   
     
     
         4 . The method of  claim 3 , wherein said PVT system comprises a first valve that is configured to select a circulation path of said heat exchange fluid between a first circulation path including a pipe within said heat exchanger unit and a second circulation path that bypasses said pipe within said heat exchanger unit, and said method further comprises actuating said first valve to select said second circulation path during said annealing. 
     
     
         5 . The method of  claim 4 , wherein said at least one means comprises a first valve that is configured to select one of said at least two different circulation paths, and said method further comprises heating said heat exchange fluid employing said boiler unit. 
     
     
         6 . The method of  claim 5 , wherein said PVT system further comprises a second valve that is configured to select a circulation path between one of said first and second circulation paths and a third circulation path that bypasses said boiler unit and said heat exchanger unit, and said method further comprises raising a temperature of said heat exchange fluid by actuating said second valve to select said third circulation path prior to said annealing. 
     
     
         7 . The method of  claim 6 , wherein said PVT system further comprises a third valve configured to select one of two inlets that are connected to an outlet of said heat exchanger unit and an outlet of said second valve, respectively, and connected to an inlet of said PVT cell, and said method further comprises actuating said third valve to accept an influx of said heat exchange fluid from said outlet of said second valve prior to said annealing, and to accept an influx of said heat exchange fluid from said boiler unit during said annealing. 
     
     
         8 . The method of  claim 3 , further comprising elevating a temperature of a photovoltaic material of said PVT cell above a boiling point of said heat exchange fluid during said annealing. 
     
     
         9 . The method of  claim 3 , further comprising:
 operating said PVT system in an operational mode that generates said thermal output while a variable configuration lid on said PVT cell is in one position; and   changing a position of said variable configuration lid to a different position during said annealing.   
     
     
         10 . The method of  claim 9 , wherein said variable configuration lid is attached to a body of said PVT cell by a hinge around which said variable configuration lid can rotate, and said method further comprises rotating said variable configuration lid whereby a front surface of said PVT cell is less ventilated during said annealing than during said operational mode. 
     
     
         11 . The method of  claim 9 , wherein said variable configuration lid is configured to slide in a plane that is substantially parallel to said front surface of said PVT cell, and said method further comprises sliding said variable configuration lid in said plane whereby a front surface of said PVT cell is less ventilated during said annealing than during said operational mode. 
     
     
         12 . The method of  claim 9 , wherein said variable configuration lid is configured to move in a direction substantially perpendicular to said front surface of said PVT cell, and said method further comprises moving said variable configuration lid in said direction whereby a front surface of said PVT cell is less ventilated during said annealing than during said operational mode.