📄 agriculture

Role of seawater air conditioning for food security in hot coastal deserts

This paper demonstrates that Seawater Air Conditioning (SWAC) offers a cost-effective, low-carbon solution for year-round food production and storage in hot coastal deserts like the GCC, significantly reducing cooling costs compared to conventional energy-intensive systems and thereby enhancing regional food security.

Original authors: Julian David Hunt, Sa'd Abdel-Halim Shannak, Ricardo Ganem Leal, Kanhan Sanjivy, Mohammad Reza Nikoo, Michael Alan William Katz, Marcos Aurelio Vasconcelo Freitas, Logan Cochrane, Hylke E. Beck

Published 2026-07-06

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Julian David Hunt, Sa'd Abdel-Halim Shannak, Ricardo Ganem Leal, Kanhan Sanjivy, Mohammad Reza Nikoo, Michael Alan William Katz, Marcos Aurelio Vasconcelo Freitas, Logan Cochrane, Hylke E. Beck

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the Gulf countries (like Oman, Saudi Arabia, and Qatar) as a giant, high-tech kitchen sitting in the middle of a scorching desert. Right now, this kitchen is in trouble. It relies almost entirely on food being shipped in from far away, and it has very little space to store that food safely because the heat is so intense that grain rots and meat spoils quickly. To keep food cool, they currently use massive air conditioners that guzzle electricity and create a lot of pollution.

This paper proposes a clever, nature-powered solution: Seawater Air Conditioning (SWAC). Think of it as plugging the kitchen's air conditioner directly into the deep, icy ocean instead of the power grid.

Here is the simple breakdown of how it works and why the authors think it's a game-changer:

1. The "Deep Ocean Fridge"

The ocean isn't the same temperature everywhere. While the surface is boiling hot in the summer, the deep ocean (about 1,000 to 1,500 meters down) stays a constant, chilly 4°C to 7°C (39°F–45°F).

The Analogy: Imagine the ocean as a giant, natural refrigerator that never turns off.
The Mechanism: The authors suggest building a long pipe (like a giant straw) that goes out into the deep sea to suck up this cold water. This cold water is pumped to the shore, where it passes through a heat exchanger (like a radiator) to chill a separate loop of fresh water. This fresh, cold water is then sent to cool down greenhouses, grain silos, and fish farms.

2. Why Oman is the Perfect Spot

The paper focuses on Oman because it has a unique "geographical cheat code."

The Problem: In places like the Red Sea or the Persian Gulf, the water doesn't get deep enough quickly, or the deep water is too warm to be useful.
The Solution: Oman's coastline drops off very steeply into deep trenches. You can find that super-cold deep water just a few kilometers offshore. It's like having a deep freezer right in your backyard, whereas other countries have to drive 100 miles to find one.

3. The "Scale" Secret (The Big Pipe Theory)

The authors argue that the only reason this hasn't been done on a massive scale yet is that people were thinking too small.

The Analogy: Think of a garden hose. If you try to move a swimming pool's worth of water through a tiny hose, the pump has to work incredibly hard, and the water moves slowly. But if you switch to a massive, 5-meter-wide pipe (like a tunnel), the water flows easily, and the cost per drop of water drops dramatically.
The Claim: The paper calculates that if you build a huge system (cooling 2,000 Megawatts, enough for a massive food hub), the cost of cooling drops to a tiny fraction of what it costs to run a standard air conditioner.
- Standard AC: Costs about $29 to cool a unit of space.
- Huge SWAC System: Costs about $6.3 to cool the same space.
- Small SWAC System: Costs about $19.6.
- The takeaway: The bigger the system, the cheaper it gets, making it perfect for feeding a whole country.

4. What This Solves for Food Security

The paper claims this technology can fix three major problems for the Gulf:

Grain Storage: You can keep millions of tons of grain cool and dry for years without it rotting or getting eaten by bugs. This acts as a "national emergency pantry" that doesn't rely on foreign ships.
Year-Round Farming: Greenhouses can grow vegetables in the desert summer without melting, using the cold seawater to keep the temperature perfect.
Fish and Dairy: It allows for raising fish and cows in comfortable temperatures, which helps them grow faster and produce more milk, without needing expensive electric chillers.

5. The Catch and the Bonus

The Catch: Building the initial pipes and the plant is expensive and requires a lot of engineering. Also, dumping the now-warm water back into the ocean needs to be managed carefully so it doesn't hurt local sea life (though the authors suggest mixing it with surface water to fix this).
The Bonus: As the system cools the air, it pulls moisture out of it. This creates fresh water as a byproduct. The paper notes that while this water is great for watering plants in the greenhouses, it's too energy-intensive to be the main source of drinking water compared to desalination. It's a "free gift" of water, but not the main meal.

The Bottom Line

The authors conclude that by using the ocean's natural coldness, countries like Oman can stop relying so heavily on imported food. They can grow their own food and store their own grain safely, even in the hottest deserts, using a system that is cheaper to run and cleaner for the planet than the air conditioners they use today. It turns the ocean from a barrier into a lifeline for food security.

Technical Summary: Role of Seawater Air Conditioning for Food Security in Hot Coastal Deserts

Problem Statement
Food security in the Gulf Cooperation Council (GCC) region, particularly in hot coastal deserts like Oman, is constrained by extreme ambient temperatures, scarce freshwater, and limited arable land. Current agricultural strategies rely heavily on food imports (with grain import dependency ratios exceeding 70%) and strategic grain storage capacity is critically low compared to global powers. Domestic production faces significant hurdles: traditional agriculture is limited by heat, while high-tech solutions (e.g., air-conditioned greenhouses and vertical farming) are energy-intensive, costly, and associated with substantial CO2 emissions. A primary bottleneck is the massive cooling load required for year-round controlled-environment agriculture, grain storage, cold chain logistics, and aquaculture. Conventional vapor-compression cooling systems exacerbate energy demand and peak loads, creating an economic and environmental burden that threatens regional food resilience.

Methodology
The study evaluates the techno-economic feasibility of Seawater Air Conditioning (SWAC) systems designed to power integrated food production and storage hubs. The methodology focuses on a case study in Oman, leveraging its unique geography where deep seawater (5–7°C) is accessible at depths of 1,000–1,250 meters near major coastal zones.

System Design: The proposed hub utilizes an offshore intake pipeline to draw deep seawater, which exchanges heat with a freshwater loop via heat exchangers. This chilled water serves multiple functions: cooling greenhouses, chilling milk and meat, controlling aquaculture tank temperatures, and maintaining low-temperature grain storage (down to 9°C) to prevent spoilage and pest infestation.
Scaling Analysis: The core of the analysis investigates economies of scale by modeling SWAC plants with cooling capacities ranging from 0.05 GWt to 5 GWt. A key technical innovation proposed is the transition from solid-wall High-Density Polyethylene (HDPE) pipes (limited to ~2.5 m diameter) to structured-wall HDPE pipes, which can reach 5 m diameters. This allows for significantly higher flow rates with reduced material usage and installation complexity.
Mathematical Modeling: The study employs governing equations to calculate cooling capacity ( $Q_{cooling}$ ), pumping power ( $P_{pump}$ ), and the Coefficient of Performance (COP). It utilizes the Darcy-Weisbach equation and Swamee-Jain friction factor for head loss calculations in the intake and outfall pipelines. The model assumes a 20% thermal loss across the system and a 23°C temperature differential between intake (5°C) and discharge (28°C).
Cost Estimation: Unit costs for pipelines, pumps, heat exchangers, and district cooling systems were estimated based on industry data and expert experience, extrapolating costs from existing small-scale projects (e.g., 45 MW) to large-scale food hubs (up to 2 GWt).

Key Results

Economies of Scale: The study demonstrates that increasing the cooling capacity from 0.05 GWt to 2 GWt yields substantial cost reductions. The levelized cost of cooling drops from 19.6 USD/MWht (at 50 MWt) to 6.3 USD/MWht (at 2 GWt). The most significant savings occur in the offshore pipeline component, where the cost per unit of cooling capacity decreases by a factor of 17 when scaling from 0.05 to 5 GWt, primarily due to the efficiency gains of larger diameter structured-wall pipes.
Comparative Cost Analysis: For a 2 GWt system, the levelized cost of cooling (6.27 USD/MWht) is approximately 4.6 times lower than using grid electricity with conventional air conditioning (28.95 USD/MWht). The investment cost for SWAC is 2.9 times lower, and electricity consumption is 7.1 times lower than the conventional alternative.
Environmental Impact: A 2 GWt SWAC plant is projected to reduce annual CO2 emissions from 1.44 million tons (conventional) to 0.21 million tons. The system achieves a COP of 25, significantly higher than the typical COP of 3.5 for conventional AC systems.
Water By-product: The condensation of humidity from air cooled by the SWAC system can generate approximately 42,285 m³ of water per day. However, the study notes this is a by-product, as the energy intensity for condensation (55 kWh/m³) is significantly higher than desalination (3 kWh/m³).

Significance and Claims
The paper posits that SWAC offers a transformative pathway to strengthen food security in the GCC by providing low-carbon, renewable cooling at a fraction of the cost of conventional systems. By enabling year-round controlled-environment agriculture, extending the shelf life of strategic grain reserves (up to 2–3 years), and supporting modern aquaculture, SWAC addresses the water-energy-food nexus.

The authors claim that while the initial infrastructure costs are substantial, the long-term operational savings and reduced carbon footprint make SWAC a viable solution for national food security strategies, specifically aligning with Oman's Vision 2040 and net-zero goals. The study emphasizes that the feasibility is highly dependent on site-specific bathymetry and the ability to utilize large-scale infrastructure (5 m diameter pipes) to maximize economies of scale.

Limitations and Modesty
The paper explicitly acknowledges that its cost estimates are pre-feasibility projections. It notes that no SWAC plant with a capacity exceeding 50 MW has been implemented to date, meaning the extrapolation of performance metrics (such as a COP of 25) from a 2.4 MWt pilot (Tetiaroa) to a 2 GWt food hub remains a source of uncertainty. The authors caution that future optimization must consider variable intake temperatures, pipeline lengths, and specific humidity control requirements for different agricultural sectors. They also highlight the need for environmental management strategies to mitigate potential impacts on marine ecosystems from the discharge of warmed seawater.