A recent study by the School of Earth and Ocean Sciences, University of Victoria [48.5°N, 123.3°W] explores an novel energy solution against climate change: combining ocean thermal energy conversion (OTEC), which provides clean electricity, through the oceans’ natural differences in temperature, to generate sustainable energy, with direct air carbon capture and storage (DACCS), which removes CO2 from the air. Liquid DACCS pass the air through a chemical solution while solid DACCS captures CO2 on the surface of a filter covered in a recyclable chemical agent, where it then forms a compound, which is heated to release the CO2.
How OTEC Works
OTEC makes use of the temperature difference between warm surface waters and cold deep waters to generate electricity. You can find more information here, but the process involves:
- Pumping Warm Surface Water: Heat from surface water vapourises a working fluid (e.g., ammonia) in a heat exchanger.
- Generating Electricity: The vapour drives a turbine connected to a generator.
- Cooling with Deep Water: Cold water pumped from depths of around 1,000 metres condenses the working fluid back to liquid form, completing the cycle.
The system requires a temperature gradient of at least 18–20°C to operate efficiently.
OTEC and DACCS: A Powerful Combination
DACCS captures CO₂ directly from the air, liquefies it, and injects it into deep-sea geological formations for permanent storage. The study explores two scenarios:
- Low Mitigation (ODLMit): OTEC powers the entire DACCS process, reducing emissions by 471 gigatonnes (Gt) of CO₂ by 2100.
- High Mitigation (ODHMit): OTEC powers only the electrical component, with additional natural gas energy sequestered. This scenario removes 2,446 Gt of CO₂ over the same period.
Key Findings
- Massive Emission Reductions:
- ODHMit cuts net emissions by 278 parts per million (ppm), significantly slowing global warming.
- OTEC-DACCS deployment could lower global surface air temperatures by up to 1.2°C compared to a business-as-usual scenario.
- Sustainable Energy Production:
- OTEC provides up to 3 terawatts (TW) of clean energy annually without disrupting ocean ecosystems.
- The levelised cost of electricity (LCOE) for OTEC is competitive with coal power, ranging from $0.04 to $0.24 per kWh.
- Economic and Environmental Benefits:
- Repurposing decommissioned oil and gas platforms for OTEC plants reduces costs and speeds up deployment.
- Enhanced vertical mixing from OTEC strengthens ocean currents like the Atlantic Meridional Overturning Circulation, mitigating climate impacts.
Why This Matters
The innovative pairing of OTEC and DACCS demonstrates how marine-based solutions can address climate change at scale. Unlike nature-based approaches, which are limited by land availability, this strategy taps into the vast, underutilised thermal energy of the oceans.
This study goes beyond conventional discussions about OTEC by demonstrating its role as a climate mitigation powerhouse. By directly integrating OTEC with DACCS, it reimagines how renewable energy systems can simultaneously provide clean electricity and remove carbon from the atmosphere. Moreover, the innovative reuse of decommissioned oil and gas platforms for OTEC plants presents a practical, cost-effective pathway to scale deployment, making this approach uniquely positioned to accelerate the global transition to net zero.
A Vision for the Future
This research underscores the potential of ocean energy systems to transform climate mitigation efforts. By investing in technologies like OTEC and DACCS, we can unlock a future of cleaner air, stable climates, and sustainable energy—turning the vast power of our oceans into a global asset.
Source
Mitigating Anthropogenic Climate Change with Aqueous Green Energy, Scientific Reports, 2023-05
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