Why Correct: India's first and only operational Ocean Thermal Energy Conversion (OTEC) plant was established at the National Institute of Ocean Technology in Chennai (Madras), Tamil Nadu, utilizing the temperature difference between surface and deep ocean waters.
Distractor Analysis: Kolkata is a major port city on the Hooghly River but lacks OTEC infrastructure. Haldia is a port in West Bengal known for petrochemicals, not OTEC. Paradwip (Paradip) is a port in Odisha focused on cargo handling, with no OTEC facility.
Takeaway: OTEC requires a minimum temperature difference of 20°C between surface and deep water, making tropical coastal regions like Chennai suitable, and it represents a renewable energy source with potential for desalination.