Renewable Energy Engineering- ICAR JRF/SRF 2024

• Groundwater Wells and Drilling Technologies:
• Percussion (cable tool) drilling $\to$ (II): Uses heavy drill bits lifted and dropped repeatedly, exceptionally suited for hard, fractured, consolidated formations (rock/boulders).
• Rotary drilling $\to$ (I): Uses a rotating bit with circulated drilling mud (bentonite), fast and optimal for unconsolidated formations (sands, silts, clays).
• Artesian well $\to$ (IV): Taps a confined aquifer under hydrostatic piezometric pressure higher than the top of the aquifer (or ground surface).
• Perched aquifer $\to$ (III): A local lens of groundwater resting on an impermeable stratum above the regional main water table, behaving as a localized unconfined aquifer.
• Matching Result: (A) - (II), (B) - (I), (C) - (IV), (D) - (III) (Option 3).

Correct option: (3) (A) - (II), (B) - (I), (C) - (IV), (D) - (ttl)

• Specific Speed of Centrifugal Pumps:
• Statement (I): Specific speed of the pump is directly proportional to the square root of head. $\implies$ Incorrect.
• The dimensionless/standard specific speed of a pump is given by:

• Specific speed is directly proportional to the square root of discharge ($\sqrt{Q}$) and inversely proportional to head raised to the power 3/4 ($H^{3/4}$).
• Statement (II): The specific speed for a single impeller centrifugal pump varies between 300 to 5000. $\implies$ Correct.
• In US customary units (rpm, gpm, ft), single-impeller radial centrifugal pumps operate between 500 and 4000 (up to 5000 for mixed flow).
• Conclusion: Statement (I) is incorrect but Statement (II) is correct (Option 4).

• Crop Water vs. Field Irrigation Requirements:
• Statement (I): Water requirement of the crops is lesser than the field irrigation requirement. $\implies$ Correct.
• Water Requirement ($WR$) represents the total consumptive use plus leaching/nursery needs. Field Irrigation Requirement ($FIR = WR - ER - S$) accounts for field application losses (conveyance, deep percolation, runoff);
• Because of application efficiency $\eta_a \lt 100\%$, $FIR = \frac{NIR}{\eta_a}$, meaning field irrigation requirement is larger than net crop requirement.
• Statement (II): Field irrigation requirement does not include contribution from other sources except irrigation. $\implies$ Incorrect.
• Net irrigation requirement explicitly deducts contributions from effective rainfall ($P_e$) and groundwater contributions ($G_w$).
• Conclusion: Statement (I) is correct but Statement (II) is incorrect (Option 3).