(45b) Ocean Thermal Energy in the Gulf of Mexico for Coproduction of Desalinated Water and Green Ammonia As Hydrogen Carrier

The world’s oceans are the largest collectors and storage of the solar energy. Large scale deployment of Ocean Thermal Energy Conversion (OTEC) plants in tropical and subtropical regions will be a Bridge to 2050 Decarbonization goal. Deployment of large scale OTEC plantships can have positive impacts on ocean environment beside producing desalinated water and green ammonia as hydrogen carrier. This is specifically true for the Gulf of Mexico, which has been one of the favourable sites for OTEC plants. The critical aspect of large-scale OTEC plants in the Gulf of Mexico is to extract the energy from the surface seawater and discharge mixed seawater at an optimal depth. The extraction of thermal energy from the surface water and upwelling of deep-ocean cold water would reduce systematic rise of the surface seawater temperature of the Gulf of Mexico. This is a visionary and ambitious goal. However, in the recent years, surface temperature of the Gulf of Mexico has increased by 1-2°C, causing severe storms with unpredictable intensity, in addition to acidification of seawater. Large-scale OTEC plants will moderate rising of Gulf of Mexico seawater temperature, beside direct impact on the abatement of green-house gas emissions from the Gulf States. The Gulf of Mexico is a major producer of oil and natural gas with more than 1,700 oil platforms and rigs. At current production rate of about 1.6 million barrels per day, the oil reserve will start depleting in coming decades that will cause decommissioning of offshore oil platforms. The present assessment study focuses on the following key elements of large-scale deployment of OTEC plants in the Gulf of Mexico: a) production of ammonia as hydrogen carrier; b) freshwater production for the water-stressed Caribbean Island and Gulf States; c) conversion of captured carbon dioxide from the Gulf States to specialty and commodity chemicals, such as methanol, dimethyl ester and alkyl carbonates; and d) recovery and conversion of carbon dioxide from seawater. An analysis was performed for production of 3,000 tonnes per day of ammonia along with desalination of seawater to evaluate the techno-economic assessment (TEA) of satellite OTEC plantships by conversion of oil platforms to ammonia producing plants. The electric power to the ammonia synthesis process is supplied by floating OTEC plants. Emerging energy efficient ammonia synthesis processes enhances the overall techno-economic merits. Conversion of out-of-service oil platforms to OTEC plant significantly reduces the total-installed-cost (TIC) by taking the credit for costs associated with dismantling and disposal of oil platforms. The Technology Readiness Level (TRL) is at such a stage that such a satellite OTEC plantships can be deployed in foreseeable future with low techno-economic risks.