Sample interview questions: Describe the behavior of photovoltaic cells and their relation to thermodynamics.
Sample answer:
Behavior of Photovoltaic Cells
Photovoltaic cells, also known as solar cells, convert light energy into electrical energy through the photovoltaic effect. This occurs when photons from light interact with semiconductor materials in the cell, generating charge carriers (electrons and holes). The separation of these charge carriers by an internal electric field creates a voltage and current flow.
Thermodynamic Considerations
The behavior of photovoltaic cells is closely related to thermodynamics, the branch of physics concerned with energy transfer and transformations. The following thermodynamic principles are relevant:
- Energy Conservation: The total energy input to a photovoltaic cell must be equal to the sum of the electrical energy output, thermal energy loss, and other energy losses.
- Entropy Generation: The conversion of light energy to electrical energy is an irreversible process that generates entropy, as some energy is lost as heat.
- Carnot Efficiency: The maximum efficiency of a photovoltaic cell is limited by the Carnot efficiency, which is determined by the temperature of the cell and the temperature of the surrounding environment.
Efficiency and Limiting Factors
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