In light of impending seismic activity, rising sea levels, and intensifying storms caused by climate change, movable seawall technology has emerged as a pivotal solution. Its adaptability and effectiveness make it a focal point of interest in disaster preparedness strategies worldwide.

Now, a team of researchers from the Tokyo Institute of Technology has introduced an innovative concept: the Self-Powered Movable Seawall System (SMS). This system harnesses microtidal energy to operate its gates autonomously.  

Such a design represents a significant leap forward in sustainable coastal defence strategies, offering both resilience and environmental responsibility in the face of mounting natural threats, according to researchers. 

The details regarding the team’s innovation were published in the journal Renewable Energy

Innovative solution

Japan, boasting more than 2,780 fishing ports and 993 commercial and industrial ports, is confronted with the formidable task of protecting these vital coastal assets against the devastating impacts of tsunamis. 

A potential remedy is found in a movable barrier system, where seafloor gates rise to shield ports from tsunamis, storm surges, and high waves. Yet, in natural disasters, power outages can hamper the operation of these gates.

Furthermore, Japan’s extensive coastline, while offering vast potential for renewable energy generation, faces limitations due to relatively small tidal ranges. Traditional tidal power methods are deemed impractical on a large scale.  

Self-elevating seawall gate rises from storage, creating a sea-level difference that powers turbines for electricity generation. Image: Hiroshi Takagi.

However, the innovative SMS system capitalises on microtidal amplitudes, ranging from 10cm to 150cm during spring tides. This system features a network of gates, each spaced 30cm apart to ensure smooth operation independently.

Within these gaps, small turbines are installed for power generation. Strategically positioned with one turbine per 50cm vertically, these turbines maximise energy extraction from the ocean’s kinetic energy, offering a sustainable solution tailored to Japan’s unique coastal conditions, according to the team. 

“To our knowledge, there is yet no system in the world that uses movable seawalls to generate electricity and then uses that electricity to operate the system itself. In this sense, SMS is a completely new concept,” said Professor Hiroshi Takagi from Tokyo Institute of Technology in a statement

Thorough tests 

In assessing 56 Japanese ports, researchers evaluated the SMS system’s viability, operating it for eight hours daily to gauge its capacity to generate electricity for repositioning gates post-tsunami alerts, factoring in the buoyant force of floating gates. Results showed nine ports as highly feasible, 14 feasible, and 33 unfeasible due to limited energy potential. 

Notably, 20 viable sites were pinpointed along Japan’s western coast, confronting the Nankai Trough’s seismic risks. These locations present promising prospects for safeguarding vulnerable ports and hinterlands.

Specifically, Himeji and Fukuyama’s ports emerged as examples of favourable energy surplus generators, nestled in the Seto Inland Sea, bolstering industrial resilience against calamities. 

Beyond tsunami defence, researchers point out that this approach integrates renewable energy utilisation with disaster preparedness, accentuating its multifaceted benefits for critical infrastructure protection and emergency power provision. “Our findings outline a synergistic system between disaster prevention and the use of renewable energy,” said Takagi in a statement.  

Despite recognising technical obstacles and regulatory constraints, researchers hope the SMS system could provide a viable safeguard system for ports, fortifying them against natural calamities, escalating sea levels, and severe coastal flooding.

“If the technology of the proposed movable tsunami barrier, under the harsh disaster conditions in Japan, can be firmly established through this research, there is no doubt that a day will come when this technology can be exported and deployed overseas as a groundbreaking disaster prevention technology,” said Takagi.