Ocean Thermal Energy for Abatement of Global CO2 Emissions

C.B. Panchal
E3Tec,
United States

Keywords: OTEC, renewable energy, CO2 abatement

Summary:

In the past two centuries, fossil fuel supplied by coal, petroleum and natural gas has played a key role in establishing the modern world economy. When the global demand for electricity increased from 8.3 million GWh in 1980 to 22.7 million GWh in 2012, the resulting annual CO2 emission increased from 5.5 to 13.3 billion tonnes. Today, the global demand for energy-intensive products, such as ammonia and plastics, is also expanding with the growing population and improved standards of living in emerging markets. The impact of rising CO2 levels on climate change is now taken seriously, as demonstrated by the COP21 meeting in Paris, which has stimulated global action to reduce CO2 emission. Considering the magnitude of the issue, these efforts will be required to stabilize and then reduce CO2 levels in the atmosphere. There are global movements to reduce emission of green-house gases (GHGs) and Ocean Thermal Energy Conversion (OTEC) potentially could make a significant contribution towards reducing global emissions. The world’s oceans are the largest collectors and storage of solar energy and have an enormous potential both to supply growing worldwide energy demands, as well as provide commodity products like ammonia and fresh water. Significant technical progress has been made on OTEC and the major technical barriers have been removed by a multi-year development between 1970’s and 1990’s. Despite these significant developments, not a single commercial OTEC plant was installed and the U.S. as well as world’s OTEC program diminished in early 1990’s as a consequence of low fossil energy costs. Today, global energy, environment, and economic settings have drastically changed: uncertain future energy costs; increased energy demands from emerging economies; awareness of the impacts of green-houses gas (GHG) emissions; and recognition of the “Energy-Water Nexus.” Water scarcity is being recognized to support production of alternate energy sources, such as fracking for oil and gas production as well as production of biobased fuels. Recently, commercialization of the OTEC technology is being actively pursued by private organizations with the focus on the island states. This study focuses on the path forward to global implementation of OTEC technology based on five-step visionary goals: a) Global displacement of petroleum based power generation in the island states; b) OTEC plantships for at-sea production of ammonia to displace coal-based ammonia production; c) Desalinated water production for regions with critical shortages of potable water; d) Conversion of captured CO2 from coastal regions to methanol using OTEC produced hydrogen; and e) At-sea production of ammonia as a hydrogen carrier. C-footprint analysis is performed to demonstrate CO2 abatement potentials by displacement of carbon-based power generation and production of commodity products. The technology status is presented and risk-management matrix (RMM) is evaluated for implementing the OTEC technology for achieving the five-step visionary goals.