From concept to lab bench —
the V-ACCESS journey

The project started with a fundamental question: for which vessels does a hybrid energy storage system actually make sense? The team ran a quantitative screening of seven vessel typologies, weighing factors like power demand variability, port dwell time, mission profile, and fuel consumption patterns. Three emerged as priority case studies: the electric ferry (high predictable power demand, short hops), the offshore support vessel with active heave compensation (OSV-AHC, extreme power spikes during crane operations), and the stern trawler (mixed mission profiles from harbour to offshore, diesel-heavy). Deliverable D1.1 catalogued all seven; D1.2 developed a full preliminary HESS design and sizing for each of the three, including lifetime, weight, volume and emission benefit quantification. Target: ≥2 use cases. Actual: 7 identified, 3 fully designed.

Before any power electronics could be tested, V-ACCESS needed to answer a harder question: are supercapacitors and SMES physically and normatively compatible with the marine environment? WP2 tackled this head-on. D2.1 produced full environmental specifications (vibration, shock, temperature, humidity, EMC). D2.2 defined the naval architecture integration requirements. D2.3 — the centrepiece — built a complete virtual prototype of the test-case ferry in Cadmatic software, including structural integration layouts for both SC and SMES modules, and ran a compliance assessment against RINA, DNV and ABS class rules across five categories: vibration, acoustics, mechanical, electrical/EMC, and fire safety. The consortium's conclusion, quoted directly: "both solutions proved to be perfectly suitable for deployment on board the test-case ferry."

Before putting anything on a physical bench, UniGE built a real-time digital twin of the entire system at its ShIL laboratory. The platform: an OPAL-RT OP4512 real-time simulator running at a 210 nanosecond time step, paired with an Imperix B-Box RCP 3.0 hardware controller. Five components were integrated simultaneously in this Controller Hardware-in-the-Loop (CHIL) environment: battery ESS (BESS), supercapacitor ESS (SCESS), SMES ESS (SMESS), bidirectional DC/DC power converters, and a dynamic vessel load profile. Simulation results were cross-checked against manufacturer datasheets from SKT (supercapacitors) and ASG (SMES). SC converters showed efficiency above 95%; SMES converters around 90% — both consistent with literature. The CHIL environment validated control strategies, identified tuning needs, and gave the team confidence to proceed to the physical lab. Target: ≥4 components in simulation. Achieved: 5.

Parallel to simulation, WP3 designed the full DC power system architecture for all three case study vessels. The electric ferry requires 2 MW; the offshore support vessel 3 MW for dynamic positioning; the stern trawler up to 4 MW peak during trawling operations. All designs comply with IEEE Std. 1709, the reference standard for DC marine power systems (1–35 kV range). D3.1 documented power flows, bus bar sizing, cable parameters and protection schemes. The lab demonstrator at ETEF was subsequently built around a 1050 V nominal DC bus — representative of the ferry case study — capable of running all key experiments. Voltage deviations during 100 kW load steps remained well within IEEE Std. 1709 limits in both simulation (D3.1) and laboratory testing (D3.5).

An integrated techno-economic and environmental assessment of hybrid energy storage systems (HESS), combining battery energy storage systems with supercapacitors or superconducting magnetic energy storage, compared to conventional battery-only solutions, was carried out to quantify efficiency improvements and life cycle impact on climate change in marine applications. In all cases, the reference configuration consists of a stand-alone battery system, while hybrid configurations integrate auxiliary storage to manage peak power and reduce battery stress. The analysis covers three representative case studies — an electric ferry, an offshore support vessel with active heave compensation, and a trawler. The results show that hybridization, particularly with supercapacitors, consistently reduces climate change impacts due to lower operational energy losses, with reductions of about 13% for the electric ferry, up to 17% for the offshore vessel, and up to 31% for the trawler. Full results in D4.2 and D4.3.

With simulation complete and physical testing beginning, WP4 conducted a formal Technology Readiness Level (TRL) assessment. Supercapacitor HESS: confirmed at TRL 5 — technology validated in a relevant environment. This is a meaningful milestone: TRL 5 means the system works not just in a lab, but in conditions representative of real deployment. SMES HESS: also confirmed at TRL 5 — technology validated in a relevant environment — following the completion of laboratory testing at ETEF. The assessment is published in D4.4 and provides the maritime industry with a transparent maturity map for both technologies.

Supercapacitors store large amounts of energy at high voltages; SMES coils operate at cryogenic temperatures with powerful magnetic fields. Before regulators can accept these technologies on commercial vessels, every plausible hazard must be mapped, assessed and mitigated. WP5 completed a full HAZID (Hazard Identification) analysis in close collaboration with RINA, DNV and ABS. Hazards were systematically identified, ranked by likelihood and consequence, and assigned mitigation measures. The results cover electrical, thermal, mechanical, cryogenic and EMC hazard categories. D5.3 documents the complete analysis and has been shared with maritime regulatory bodies as a reference document for future class rule development. Zero open high-severity hazards.

Even with a validated, safe system, commercial deployment is impossible without regulatory acceptance. V-ACCESS systematically compared existing maritime energy storage standards — originally written for batteries — against the specific characteristics of supercapacitors and SMES. The gaps are real and significant: more than eight distinct areas where current rules provide no adequate coverage. These span thermal management during fast charge/discharge cycles, cryogenic handling procedures for SMES, dynamic response requirements beyond what battery standards consider, and electromagnetic compatibility in dense marine electrical environments. D5.4 documents each gap with a proposed regulatory approach. The findings have been formally submitted to RINA, DNV and ABS, and are expected to inform the next revision cycle of their energy storage class rules.

The ETEF (Electric TEst Facility) in Trieste — operated by UniTS — became the stage for the physical verification of everything the project had designed and simulated. The 1050 V-zonal DC grid demonstrator was separately subjected to load steps of 20 kW, 50 kW and 100 kW. The supercapacitor HESS responded correctly at all power levels: peak power fully shaved, voltage transients within IEEE Std. 1709 limits, dynamic response matching CHIL predictions. The SMES system also ensured 20 kW–50 kW–100 kW power delivery, while the time duration depends on the automation intrinsic delay in configuring the subsystems. HESS and SMES demonstrated therefore their capability in feeding the onboard loads in the designed tests. Full results in D3.5.

V-ACCESS was never just about proving a technology — it was about creating the knowledge base and the people who will deploy it. D5.5 delivers a comprehensive training handbook structured as a 2-day equivalent course. It works at three levels simultaneously: theoretical (physics of supercapacitors and SMES, power electronics, system integration), practical (computer simulation exercises students can run on their own machines), and operational (what vessel crew and port engineers need to know for safe operation and maintenance). The handbook is designed to be adopted by maritime engineering programmes, shipyards, and classification society training arms. Meanwhile, the PSC has managed the entire project through a significant disruption — the M26 transport accident — navigating the Amendment AMD-01 process and keeping all partners aligned. The project is on track for a complete wrap-up at M40.