Harnessing Nature's Power: Ocean Thermal Energy Conversion and Deep-Sea Water By-products

Introduction

In a world where renewable energy sources are becoming increasingly important, Ocean Thermal Energy Conversion (OTEC) stands out as a promising and largely untapped resource. This innovative technology leverages the temperature difference between warm surface water and cold deep-sea water to generate electricity. Additionally, OTEC offers a unique advantage - the utilization of deep-sea water by-products. In this blog, we will delve into the process of Ocean Thermal Energy Conversion and explore the various potential applications of deep-sea water.

In my previous blog post I explained a bit about the science behind the OTEC process, if you have not read it you can find it here. However, generally the process can be broken down into four main components.

1. Seawater Selection: The first step in OTEC involves carefully selecting suitable locations where there is a significant temperature gradient between surface water and deep-sea water. These areas are typically found in tropical regions where the surface water can reach temperatures of 25°C (77°F) or higher, and the deep water remains at around 5°C (41°F).
2. Cold Water Pipe: A key component of OTEC is the cold-water pipe, which extends from the ocean's surface to the depths where the cold water is located. This pipe allows for the transportation of the cold water required for the energy conversion process.
3. Energy Conversion: The heart of OTEC lies in the heat exchanger. Warm surface water is pumped through a heat exchanger, where it is used to vaporize a low-boiling-point fluid (often ammonia). This creates a high-pressure vapor which drives a turbine, generating electricity.
4. Condensation: After passing through the turbine, the vapor is condensed by cold deep-sea water. This transforms it back into a liquid state, ready to be reutilized in the process. 
   

 

Deep Sea Water by-products

The utilization of deep-sea water is a unique aspect of OTEC that sets it apart from other renewable energy sources. This cold, nutrient and mineral-rich water holds immense potential for various applications. I had the pleasure of visiting South Korea, particularly Gangwon province, Goseong-gun, Oho-ri. During my visit, I had the privilege of exploring one of the research facilities of the Korean Institute of Ships & Ocean Engineering (KRISO). They graciously shared with me the extensive research they have conducted over the years. OTEC in particular, had many applications and these include:

1.     Aquaculture:

Sea-cucumber Farming

Fish Farming

• Deep sea water is teeming with nutrients and minerals. It can be used to foster the growth of marine life such as fish, shrimp, and shellfish. This creates opportunities for sustainable aquaculture ventures.

2.     Desalination:

Fresh Water Production

 

Reverse Osmosis Unit

• The cold deep-sea water can be used for desalination purposes. By leveraging the temperature differential, OTEC can efficiently produce fresh water from seawater, addressing water scarcity issues in coastal regions.

3.     Sea-Water Air-Conditioning (SWAC):

Sea-Water Air-Conditioning System

Containerized closed-loop OTEC System

 

 

 

 

 

 

• Deep sea water can be employed for cooling applications, reducing the reliance on energy-intensive air conditioning systems. This is especially relevant in tropical regions with high cooling demands. 

4.     Agriculture:

Dr. Kim (KRISO) right and myself at Hydroponic Cafe

Hydroponic Wheel growing Lettuce

• The nutrient-rich properties of deep-sea water can be utilized for agricultural purposes. It can enhance soil fertility and promote the growth of crops, offering sustainable solutions for agriculture in coastal areas.

These are just four areas which deep-sea water can be used and these can even branch out to many other possibilities (e.g., cosmetics, salt production, etc.) Picture this, if KIRISO’s (in partnership with CMI/MCST) OTEC pilot project in the RMI is successful and we have proof of concept, the existing and future organizations/companies in the Marshall Islands can start incorporating the many benefits of deep-sea water into their production.

For example,

• MEC can use deep sea-water for cooling engines in the power-plant, aside from electricity production, which can be more efficient since the water is available at much cooler temperature,
• MWSC can start fresh water production using desalination,
• TOBOLAR can use deep-sea mineral too add into their cosmetic production line,
• CMI can focus on research and capacity building,
• MIMRA can conduct studies on deep-sea marine life,
• we can even start salt production and deep-sea salt is rich in nutrients and minerals, 
• and the list goes on.

Conclusion

Ocean Thermal Energy Conversion is a remarkable technology that holds great promise in the transition towards sustainable and renewable energy sources. Beyond its capacity to generate electricity, the utilization of deep-sea water byproducts adds a layer of versatility and ecological benefits. As research and development in OTEC continue, we may soon witness a significant expansion of this eco-friendly energy source, contributing to a more sustainable future for our planet.

Blog post by: Wayne Raymi Kijiner

Mr. Wayne Raymi Kijiner is an Electrical Engineer at Marshalls Energy Company in Majuro, Marshall Islands.