What are Ballast-Free Ship Designs?

Global shipping moves around 80 per cent of all the cargo and essential commodities worldwide and is the backbone of the international logistics chain.

The majority of this cargo is carried by cargo ships, which have ballast tanks at the bottom. These tanks are filled with seawater at the starting port where the empty vessels sail to maintain balanced navigation; when the ship arrives at the destination port, the water in the ballast tank is discharged.

This traditional conception of cargo water tanks has two major drawbacks:

• the empty ship sailing increases the weight of the ballast tank filled with ocean water, which increases the energy consumption of the ship;
• the seawater loaded in the water tank is discharged, causing marine pollution.

There are about 10 billion tons of cargo water carried by vessels worldwide. Ballast water discharge from vessels on transnational passages has caused the eruption of alien organisms and has been listed as one of the four major hazards of the ocean by the Global Environmental Protection Fund (GEF). At present, Ship owners, business directors, etc., rely on ballast water treatment, similar to heating, electrolysis, and UV treatment.

The United States has espoused several measures, like ballast water relief and retention of operation freights on board. Still, these ballast water treatment technologies aren’t only time-consuming and labour-intensive but also increase operating costs and ultimately reduce owner profit. The International Maritime Organization (IMO) estimates that ballast water discharges harbour billions of organisms daily, posing a significant threat to biodiversity.

Considering all of this, a race has begun worldwide to find a cost-effective solution to this great engineering problem.

Here, we take a deep dive into the captivating prospects of Ballast-free ships. This revolutionary idea will surely change the norm of ship construction and usher in a new era in the maritime sector. Ballast-laden ships have been the norm since the late 19th century, and until the late 2000s, the problem of ballast water discharge was not recognised.

The Adverse Effects of Ballast Water Discharge

The issue of invasive species through ballast water discharge is a significant concern for marine biologists and conservationists. Microscopic organisms like plankton, along with more giant creatures like fish larvae and crustaceans, can be inadvertently transported in ballast tanks.

When released in foreign ports, these organisms can establish themselves in new environments, disrupting the delicate balance of native ecosystems. Invasive species can out-compete native species for food and resources, alter food webs, and even introduce diseases.

In response to the growing threat of invasive species, the International Maritime Organization (IMO) adopted the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BWM Convention) in 2004.

This convention sets standards for ballast water treatment, requiring ships to either exchange ballast water at sea or treat it with an approved system to kill or remove organisms.

While the BWM Convention represents a significant step forward, it has limitations. Ballast water treatment systems can be complex and expensive to maintain, adding operational costs for shipping companies. Additionally, the effectiveness of these systems can vary depending on factors like water quality and organism types.

Furthermore, the mid-ocean exchange process mandated by the convention can be time-consuming and increase fuel consumption, impacting both economic and environmental sustainability.

Introduction to the Concept of Ballast-Free Ships (BFS)

Ballast-free ships offer a revolutionary solution to our problem at hand. This particular concept was independently pitched by the University of Michigan, Daewoo Shipbuilding and Marine Engineering and Shipbuilding Research Center of Japan( SRCJ).

All of them pitched various ideas and different solutions for the Removal of conventional ballast tanks. Let us take a look at a few approaches:-

Flow-through Ballast Trunks: One approach utilizes a system of longitudinal structures called ballast trunks. These ingenious trunks run along the bottom of the ship, essentially becoming an extension of the hull. In loaded conditions, the trunks remain empty, offering minimal resistance to water flow. However, seawater is strategically allowed to flood the trunks during ballast voyages through controlled inlets and outlets.

This flooding adjusts the ship’s draft and ensures stability. The design often incorporates a pressure differential between the bow (front) and stern (rear) of the ship, creating a continuous seawater flow within the ballast trunks.

This continuous flow helps to minimise the risk of invasive species establishing themselves within the system. However, challenges remain in optimizing the flow rate and pressure differentials to ensure adequate stability across various sea conditions and cargo loads. Additionally, the structural integrity of the ballast trunks under stress requires careful consideration during design and material selection.

Hull Form Optimization: Another captivating approach leverages the inherent buoyancy of the ship itself. Naval architects can meticulously design the hull form to achieve the desired draft in ballast conditions.

This can involve strategic variations in the hull shape, such as a wider beam or a more U-shaped hull section. These modifications can increase the underwater volume of the empty ship, providing the necessary buoyancy without ballast water. Furthermore, computational fluid dynamics (CFD) simulations can be employed to optimize the hull form for minimal drag and improved fuel efficiency.

However, this approach might not be universally applicable to all ship types, particularly those requiring significant variations in draft depending on cargo load. The competing design teams created two particular hull forms. First, the Monomoran hull design provides a rearwardly open recess at the bottom of the ship, which is shaped like an inverted front and rear flapper.

This type of ship allows the ship to produce a larger water gauge at light or no load. However, the disadvantage of this scheme is that the area of the hull contacting seawater is greatly expanded compared with the conventional ship type, and the length of the ship’s side is increased.

The second is the V-shaped hull proposed by a Japanese research institute. The most prominent feature of the non-ballasted tank super large tanker (VLCC) design is the hull of the lower part of the ship is more slender, and the bottom of the ship presents a V-shaped shape that protrudes downwards, which makes the draught of the non-ballasted tanks sufficient to support the weight of the ship when it is empty.

Shipbuilding experts initially selected two designs for non-ballasted tanks. The main purpose of the first non-ballasted tank hull design codenamed “Best” is to design a non-ballasted tank vessel that is built on a waterless, deep, restricted waterway, such as the Persian Gulf.

Its hull type is 35 m deep, with a maximum width of 56 m, a full load of 27 m, and a cargo capacity exceeding 300,000 t.

Experts said that the second non-ballasted water hull design, codenamed “Malacca,” is being developed to build ships suitable for sailing from the Persian Gulf through the Straits of Malacca to China, Japan, and South Korea in the Far East. Its hull has a maximum width of 79 m, a depth of 30 m, a full load of 21 m, and a cargo capacity of 280,000 t.

Both hull forms underwent rigorous testing in simulation and live testing, which gave very valuable insights into hull optimization and made it economically possible to produce such designs.

Variable Buoyancy Chambers

• This approach uses strategically placed compartments within the hull that can be filled with air or water to achieve the desired level of buoyancy.
• Imagine compartments functioning like air pockets in a life vest.
• This method offers greater flexibility in draft control compared to longitudinal trunks.
• A fully loaded ship might require some chambers to be flooded for stability, while an empty ship could utilize air-filled chambers for optimal fuel efficiency.
• Advantages: High degree of flexibility in draft control, potentially improved fuel efficiency.
• Disadvantages: Increased complexity in design and construction may require additional piping and control systems.

Conclusion

This revolutionary concept offers to change the Ship construction industry. Regulatory frameworks that are already established will need to change to accommodate this new class of ships. For instance, the optimized hull designs of ballast-free ships can lead to significant reductions in fuel consumption, directly impacting the maritime industry’s carbon footprint. However, challenges remain, such as the need for further cost reduction and infrastructure development to support these innovative vessels.

Nonetheless, the evolution towards ballast-free ships represents a promising path towards a greener and more sustainable maritime future – one that balances environmental stewardship with economic viability on the high seas.

You might also like to read-

• A Guide To Ballast Tanks On Ships
• Ballast Water Treatment System – A Boon For Many, A Menace For Some
• 10 Important Points to Comply With Ballast Water Convention
• How Ballast Water Treatment System Works?
• A Detailed Explanation on How to Operate a Ship’s Ballast System