Cost of operation of which plant is least?

Question

Examoogle · Accepted Answer

Hydroelectric plant

Explanation: The hydroelectric power plant has the lowest operating cost because it utilizes potential energy of water, which is a free and renewable resource, eliminating the recurring expenditure on fuel. Unlike thermal, nuclear, or gas plants, there are no fuel procurement, handling, or combustion costs associated with its daily operation.

Working Principle: Water stored in a reservoir possesses potential energy proportional to the head ($H$). As water flows down the penstock, potential energy is converted into kinetic energy, which strikes the turbine blades to produce mechanical energy. This mechanical rotation drives a synchronous generator to produce electrical power based on the equation $P = \eta \rho g Q H$.

Key Formulas: $P = \eta \cdot \rho \cdot g \cdot Q \cdot H$ — Power output equation where $P$ is power, $\eta$ is efficiency, $\rho$ is density, $g$ is gravity, $Q$ is flow rate, and $H$ is head.

Key Points: Hydroelectric plants have very low O&M (Operation and Maintenance) costs compared to thermal plants.; Fuel cost is the major component of operating cost in thermal and nuclear power plants.; Capital cost (installation) for hydro is high due to civil engineering works, but operating cost is minimal.; Life span of hydroelectric equipment is typically longer than that of thermal plants.

Advantages: No fuel cost involved; Environmentally clean (no carbon emissions); High operational life; Quick start-up and black-start capabilities

Disadvantages: High initial capital investment for civil works; Long construction time; Location specific (depends on water availability)

Applications: Base load power supply; Peak load management (pumped storage); Grid frequency regulation

Additional Info: Thermal power plants involve high recurring costs for fuel, transportation, and ash handling.. Gas turbine plants have low capital costs but very high operating costs due to expensive natural gas fuel.. Nuclear power plants have lower fuel costs than coal but high maintenance and decommissioning costs.

Answer: D is correct — Hydroelectric plants require no fuel for energy conversion, resulting in the lowest operating costs among all conventional power generation technologies.

Exam Tip: In competitive exams, always distinguish between Capital Cost (highest for Hydro) and Operating/Running Cost (lowest for Hydro).

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