Discharge water temperature assessment of thermal power plant using remote sensing techniques

Thermal power plants are generally constructed near to sea coast to meet their requirement of cooling water. The warm water discharge from the thermal power plant is one of the major environmental concerns in view of the thermal pollution in the sea water. The temperature limit for the warm water discharge from the thermal power plant has to be monitored and controlled. Coastal Gujarat Power Limited (CGPL) operates (24 × 7) at an “once-through system” based sea water circulation for power generation. The used sea water is then discharged into the sea through an outlet channel. As per environmental norms, the discharge water temperature needs to be maintained below the stipulated “delta” rise (+7 °C) with respect to ambient sea surface temperature at the inlet. We demonstrate the applicability of thermal remote sensing data in understanding the seasonal and temporal variations of the temperature difference between the discharge water and the ambient sea water. We used thermal band data from Landsat-8 satellite imagery to map water surface temperature and create temperature profiles along the intake and outflow channels (till the sea), to understand the variation of temperature and estimate the “ΔT” between intake point and various observation points along the outflow. This analysis was carried out for all 11 months (except June) of the year 2018 to correlate temperature variations with seasonal changes. Tidal conditions during the time of data acquisition were also considered to account for the effect of tides on ΔT. The result shows that the average temperature rise between intake and outflow are maintained at ∼3 °C across all the months of 2018, with minor variations in the months of July and August. Further, average temperature drop from outflow to cooling channel (before diaphragm) is seen to be ∼2 °C across all the months with similar seasonal fluctuations.