The proposed Black Sea Submarine Cable would create a new electricity connection across the Black Sea, strengthening energy connectivity between Georgia and Europe.
But moving a project of this scale from feasibility studies towards construction requires a sequence of increasingly detailed engineering decisions — from determining transmission capacity and cable technology to mapping the seabed, identifying geological hazards and securing access to a highly specialised global supply chain.
CESI, an Italian multinational group that provides clients with services in innovation, digitalisation, testing, engineering and consulting, has been involved in the technical development of the project, including the feasibility study that assessed different transmission configurations. The company is also supporting the design, procurement and supervision of the seabed surveys that will provide more detailed information for the next stages of route and cable engineering.
renewables.GE spoke with Alessandro Crippa, HV Equipment and Services Product Leader at CESI Consulting, about the engineering behind the proposed interconnector and what needs to happen before the project can move from feasibility towards execution.
Why 1,300 MW?
renewables.GE: CESI’s feasibility study examined possible transfer capacities of 1,000 MW, 1,300 MW and 1,500 MW. Why did the study identify 1,300 MW as the preferred capacity for the proposed interconnection?
Alessandro Crippa: The feasibility study assessed different transfer capacities from both a power-system and a technical implementation perspective.
While all evaluated ratings were technically feasible, the 1,300 MW option emerged as the best balance between transfer capability, overall project complexity and the practical constraints associated with manufacturing, transporting and installing ultra-long submarine HVDC cables in the Black Sea.
The study also confirmed a high utilisation potential of the interconnection across different future scenarios.
Why the Project Uses HVDC
renewables.GE: What are the main technical reasons for using a 525 kV high-voltage direct-current system for a connection of this length?
Alessandro Crippa: At approximately 1,100 km in length, the Black Sea interconnection is well beyond the practical range where HVAC technology would remain efficient.
HVDC avoids the charging-current limitations associated with long AC submarine cables and significantly reduces transmission losses over such distances.
The selected ±525 kV voltage level allows a large transfer capability while limiting current levels, conductor size and overall cable losses.
In addition, Voltage Source Converter technology, selected for the project, offers strong controllability of power flows, support to interconnected grids and a proven technical solution for modern long-distance submarine interconnections.
Engineering at More Than 2,000 Metres Depth
renewables.GE: Parts of the proposed route cross water more than 2,000 metres deep. What engineering and installation challenges distinguish the Black Sea project from more conventional submarine interconnectors?
Alessandro Crippa: The project enters a category of very deep-water submarine power transmission.
Water depths of around 2,200 metres require cable designs capable of withstanding very high installation tensions during laying operations.
They also require highly specialised installation vessels, deep-water engineering expertise and careful route optimisation to limit possible criticalities caused by seabed slopes and complex seabed morphology.
The availability of vessels and contractors capable of operating at these depths is also more limited than for conventional interconnectors installed in shallower waters.
The feasibility study nevertheless confirmed the technological feasibility of such a system using currently available industry solutions.
Choosing the Cable Technology
renewables.GE: The feasibility study considered different cable technologies, including mass-impregnated and cross-linked polyethylene insulation. What factors will determine the final cable technology?
Alessandro Crippa: Both Mass Impregnated Non-Draining and XLPE technologies were considered technically viable.
The final selection will depend on the solutions proposed by manufacturers during procurement, their demonstrated performance at the required voltage level and water depth, manufacturing capability, installation methodology, reliability record and overall project risk profile.
The availability of qualified suppliers and their experience with very deep-water applications will also be an important consideration.
What the Seabed Surveys Need to Establish
renewables.GE: CESI is now supporting the design, procurement and supervision of the Black Sea seabed surveys. What must the geophysical and geotechnical investigations establish before the cable route and design can be refined?
Alessandro Crippa: The investigations must provide sufficiently detailed information on seabed morphology, geology and geotechnical properties along the corridor.
This includes seabed bathymetry, sediment characteristics, slopes, geohazards, obstacles, existing infrastructure and burial conditions.
The information will enable optimisation of the final cable route, refinement of cable spacing, identification of crossing requirements and definition of appropriate installation and protection measures.
renewables.GE: How can seabed conditions, submarine slopes, geological hazards or human-made objects affect route selection and cable-protection requirements?
Alessandro Crippa: These factors influence both the route itself and the level of protection required for long-term system reliability.
Steep slopes, submarine canyons, fluid escape features or unstable sediments can increase installation difficulty and long-term mechanical risks.
Human-made features such as pipelines, telecommunications cables, military areas, anchorage zones, wrecks and offshore energy infrastructure may require route deviations, controlled crossings or additional protective measures.
The feasibility study identified such features and incorporated them into the routing process from the earliest stages.
A Limited Global Supply Chain
renewables.GE: The feasibility study identified a limited international supply chain for producing and installing very long, deep-water HVDC cables. How significant is this constraint, and when would the project need to engage manufacturers and specialist installation companies?
Alessandro Crippa: This is one of the most important implementation risks for projects of this scale.
Only a limited number of manufacturers and installation contractors worldwide have the technical capability and production capacity required for ultra-long, deep-water HVDC systems.
Early market engagement is therefore essential to validate technical assumptions, understand capacity constraints and align project scheduling with future manufacturing and installation windows.
Testing the Project Against Different Futures
renewables.GE: How do the power-system studies assess whether electricity flows across the cable would remain technically and economically viable under different generation, demand and market scenarios?
Alessandro Crippa: The studies evaluate multiple future scenarios using detailed market and power-system models.
The objective is not to predict a single future outcome but to test project robustness under a broad range of conditions.
Market simulations are used to estimate the utilisation of the interconnection, while network studies assess load flows, security under contingencies and dynamic performance of the interconnected systems.
The overall approach verifies that the project remains operationally sound and capable of providing value across a range of future developments.
What the Seabed Survey Could Change
renewables.GE: Which assumptions or design elements from the original feasibility study are most likely to require refinement as the seabed survey and subsequent studies provide more detailed information?
Alessandro Crippa: The most likely refinements concern the precise route alignment, cable protection strategy, burial requirements, crossing designs and the final spacing between parallel cable systems.
The seabed surveys will provide significantly higher-resolution information on bathymetry, soil conditions, seabed morphology and potential geohazards, allowing the route engineering and cable design to be optimised in greater detail.
Environmental mitigation measures and installation methodologies may also be adjusted as additional site-specific information becomes available.
Such refinements are a normal and expected step in the progression from feasibility-level engineering to project development.
From Feasibility Towards Construction
renewables.GE: From an engineering perspective, what are the most important technical milestones that would demonstrate that the project is progressing from feasibility towards implementation?
Alessandro Crippa: From an engineering perspective, the key milestones include the completion of geophysical and geotechnical seabed investigations, the confirmation of a technically optimised cable route, the completion of environmental and permitting activities, and the execution of the Front-End Engineering Design phase.
These activities progressively reduce technical uncertainty and enable more accurate cost and schedule estimates.
Subsequent milestones include the procurement of the main project components, the completion of detailed design and the award of major delivery contracts.
Together, these steps demonstrate the transition from a feasibility concept to a project that is ready for execution and construction.
Source note: Interview with Alessandro Crippa, HV Equipment and Services Product Leader at CESI Consulting. Responses were provided to renewables.GE through CESI’s Communications and External Relations team.