Question

Given below are two statements
Statement I: In solar cell electromagnetic energy is converted into electricity while as in fuel cell chemical energy is converted into electricity
Statement II: In both solar cell and fuel cell conversion efficiency is limited by externally reversible heat engine cycle
In light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

Because fuel cells and solar cells are direct energy converters, they bypass the Carnot limit.
This allows them to achieve higher theoretical efficiencies than conventional combustion-based heat engines.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Direct energy conversion systems bypass the traditional mechanical steps of generating power.
They convert forms of energy, such as light or chemical energy, directly into electricity without using a rotating generator.
Detailed Explanation:
Let us evaluate Statement I:
- A solar (photovoltaic) cell absorbs electromagnetic radiation (sunlight) to excite electrons, generating an electrical current via the photovoltaic effect.
- A fuel cell uses an electrochemical reaction to combine a fuel (such as hydrogen) with an oxidant (such as oxygen), converting this chemical energy directly into electricity.
Therefore, Statement I is correct.
Let us evaluate Statement II:
The efficiency of a heat engine is limited by the Carnot cycle, as it must convert heat energy into mechanical work: \[ \eta_{\text{Carnot}} = 1 - \frac{T_C}{T_H} \] However, solar cells and fuel cells are not heat engines; they convert energy directly without converting it to thermal energy first.
Therefore, their theoretical conversion efficiencies are not limited by the Carnot or reversible heat engine cycle.
Instead, they are governed by quantum limits (for solar cells) and Gibbs free energy limits (for fuel cells).
Therefore, Statement II is incorrect.

Step 2: Final Answer:
Statement I is correct, but Statement II is incorrect.