Evaluation of ocean thermal energy for supplying the electric power of offshore oil and gas platforms

The Caspian Sea, the world's largest enclosed body of water, covers an area and volume of 371,000 km2 and 87,200 km3, respectively, and limited to the north by Russia and Kazakhstan, to the east by Turkmenistan, to the south by Iran, and to the west by Azerbaijan. The Caspian Sea can be considered the most important source of energy storage, although this focus is currently limited to fossil fuel reserves due to the multitude of offshore oil and gas projects in the North, Middle and South basins, while the potential benefits of renewable energy sources such as Oceanic thermal energy in offshore areas has not been well studied. The present study seeks to evaluate the ocean thermal energy in the offshore regions of the Caspian Sea and examine the vertical variations of water temperature using UNESCO data and ECMWF water surface temperature database. Accordingly, the mean water temperature difference has been investigated as daily, monthly and seasonal across the permanent thermocline for the Caspian Sea using Pyferret software and the possibility of the use of ocean thermal energy in offshore oil and gas fields has been evaluated. In order to show the accuracy of the ERA Interim, Daily database data, its surface water temperature data at 25 points in three Caspian basins were validated according to UNESCO field measurements at those sites. Trends of changes between the Unesco and ECMWF data are in good agreement, including in the eastern part of the Caspian Sea basin, indicating a upwelling phenomenon in this region. In general, ECMWF site surface water temperature data with a correlation coefficient of 0.971 have good accuracy. Therefore, due to the lack of field measurement data, ECMWF site data for Caspian surface water temperature can be used. To study the temperature profile of the Caspian Sea to identify areas where the vertical water temperature difference reaches 20 ° C. First, UNESCO field measurement data covering all three Caspian basins were used. By plotting temperature profiles for 25 UNESCO field measured points only at points A and B, respectively, at geographical locations 37.550 N, 50.692 E, 38.380 N and 51.853 E, the eligible temperature difference for oceanic thermal energy extraction was observed. Examining all points in the deep areas shows that the water temperature reaches 6.5 to 7 ° C at 200 m depth, and at lower depths there is no significant change in water depth. Therefore, the OTEC needs to check the water temperature in the upper layers of water. The findings show that ocean thermal energy can be extracted only from the southern basin during July and September, so that the eastern part of the southern basin has the highest coefficient for thermal energy extraction. Daily monitoring of the vertical variations of water temperature in these months shows that in the best conditions of the southern basin, it is possible to obtain the ocean thermal energy with a minimum temperature of difference 20°C, 64 days a year, and only Sardar, Shahdeniz, Ganeshli and Azeri fields have the possibility of obtaining this energy for 54, 34, 31 and 31 days of the year, respectively.