Costel Ungureanu

Hydraulic transients induced by rapid changes in operating conditions represent a major challenge in the design and safe operation of offshore Firewater systems. During emergency events, such as fire pump start-up or rapid valve operations, pressure waves may propagate throughout the distribution network, generating water hammer effects capable of compromising the integrity and reliability of critical safety equipment. This study investigates the transient hydraulic response of an offshore Firewater ring-main system installed on a Floating Production Storage and Offloading (FPSO) unit using a detailed numerical model developed in PIPENET Transient. Three representative emergency operating scenarios were analysed, including fire pump start-up, deluge valve closure, and monitor valve closure. For each scenario, the hydraulic response of the original system configuration was compared with a modified pressure-protection arrangement involving relocation of the check valve immediately downstream of the fire-pump discharge flange and reduction of the pressure safety valve (PSV) set pressure from 17.5 barg to 16.5 barg. The simulations enabled the identification of critical pressure locations, evaluation of transient pressure propagation, and assessment of the effectiveness of the proposed mitigation strategy. The results demonstrate that the modified pressure-protection arrangement reduces the governing system-level pressure peaks and attenuates transient pressure oscillations under the investigated operating conditions. The proposed engineering methodology provides practical support for the design verification and optimization of offshore Firewater systems and contributes to improving the operational safety and reliability of safety-critical piping networks.

The rapid expansion of aquaculture has led to a substantial increase in the generation of organic waste, nutrient-rich effluents, and residual biomass, creating significant environmental challenges while simultaneously providing opportunities for resource recovery within the circular bioeconomy. Environmental biotechnology offers a broad range of solutions for transforming these waste streams into valuable products, including renewable energy, fertilisers, biochar, microbial biomass, and other bio-based resources. However, the practical implementation of these technologies in floating aquaculture systems remains fragmented due to the lack of integrated engineering approaches. This review critically analyses the current state-of-the-art in environmental biotechnology pathways for aquaculture waste valorisation, covering biological, physicochemical, and thermochemical technologies applicable to floating production systems. The assessment covers anaerobic digestion, composting, insect bioconversion, microalgae cultivation, integrated multi-trophic aquaculture, nutrient recovery, hydrothermal carbonisation, and pyrolysis, together with their technological maturity, offshore applicability, and contribution to circular resource recovery. Beyond reviewing existing technologies, this paper proposes the “Circular Floating Aquaculture Systems Engineering Integration Framework” (CFAS-EIF), a systems engineering concept that integrates floating production infrastructure, waste collection, resource recovery technologies, digital management, and circular value chains into a unified architecture. The framework illustrates how environmental biotechnology can be implemented through coordinated engineering integration, enabling the transition from waste management to resource valorisation in offshore aquaculture. The proposed framework provides researchers, engineers, and industry stakeholders with a comprehensive reference for designing next-generation aquaculture platforms that support sustainable resource management, climate change mitigation, and a circular bioeconomy.

Commercial refrigeration systems represent some of the largest energy consumers in supermarkets, and therefore particular attention needs to be paid to increasing energy efficiency to reduce overall energy consumption and meet climate goals by 2030. This study investigates the performance of a CO₂ (R744) commercial refrigeration system with evaporators operating alternately in dry and flooded modes. This operation is possible due to a particular adjustment using liquid sensors installed in the middle of both low-temperature (LT) and medium-temperature (MT) liquid separators, which transmit information to the controllers that regulate the compressor rack and evaporators, to switch from dry to flooded operation when the liquid level rises and vice versa when the level drops. The results show that the correct regulation of the system of 50% with 6K superheat operation and 50% with 3K superheat operation on MT evaporators, respectively, and 50% with 6K superheat operation and 50% with 4K superheat operation on LT evaporators leads to a reduction of energy consumption compared to 100% operation of all evaporators with 6K superheat by 6.9% per year for the compressor rack.

This study analyzes the feasibility of increasing the energy and economic efficiency of a residential heating and domestic hot water (DHW) preparation system with a solar-assisted air-to-water heat pump (AWHP), implemented in southeast Romania. The following options are evaluated from the sustainability point of view (energy, economic and CO₂ emissions): renovation of the building and modernization of the system by integrating an electric accumulator, increasing the capacity of photovoltaic panels (PV) and solar thermal collectors (STCs), and the option of replacing the AWHP with a ground-source heat pump (GSHP) with a vertical loop (GSHP-VL) and a GSHP with a horizontal loop (GSHP-HL). The energy performance of heating systems was simulated using GeoT*SOL software. The results show that by renovating a home, the energy requirement for heating decreased by about 58%; therefore, following the current financial rules applied to prosumers, the GSHP-VL system has the best energy performance (electricity consumption and solar coverage rate of this consumption), economic performance (investment recovery period and annual operating cost) and environmental performance (lowest CO₂ emissions) and that through a government program that promotes energy efficiency and the use of renewable energy sources in homes, capital costs can be reduced by (43–57)% in the case of systems with HP, PV and electric storage. This study shows that a 5 kW PV system combined with 5 kWh battery cannot cover the full heat demand of a medium-to-large house during the winter, and for full energy independence, a larger PV array paired with a higher-capacity battery is necessary. Generous government subsidies amounting to 50% can reduce the payback period for such investments from (11.26–14.68) years to (5.86–7.26) years.

This paper examines the current state of Romanian seaports from the perspective of their transformation into smart ports, using the SWOT model to identify the most suitable strategies. It highlights the strengths and weaknesses of existing infrastructure, as well as the opportunities and risks, to outline coherent and sustainable courses of action for future development. A SWOT analysis was conducted based on information collected from a questionnaire sent to members of the maritime port authority, directors, and staff from various departments of the analyzed ports, as well as direct interviews with experts from the three ports. This analysis served as the foundation for developing strategies aimed at accelerating digitization, improving operational efficiency, and reducing environmental impact. The identified strategies were subsequently ranked using the AHP method. The weights assigned to the ten strategies emphasize the relative importance and systemic influence of each one on the process of ports transforming into smart entities. This study makes a significant contribution to the emerging literature on the transformation of Romanian seaports into “smart ports” by approaching this process through the lens of sustainable port development.

This paper presents the local structural analysis of a steel foundation supporting the pumps of a potable water system installed on a 30,000 DWT Handymax bulk carrier. The aim is to evaluate the structural behaviour of the foundation under static and dynamic loads representative for shipboard service and to propose simple constructive improvements that enhance stiffness and vibration performance. The potable water system is briefly described, including design requirements, sizing of the pumps, hydrophore unit and heat exchanger. The support structure is modelled in 3D CAD and analysed using the finite element method in ANSYS Mechanical, considering the mass of the pump unit and excitation frequencies up to 60 Hz. Three foundation variants are investigated: the initial design, a stiffened version obtained by adding local reinforcements and an alternative closed-section frame using rectangular hollow profiles. For each model, deformations and equivalent von Mises stresses are evaluated and compared with the yield limit of steel S235JR and with serviceability criteria from Eurocode 3. The results show that the optimized foundation with rectangular hollow sections significantly reduces maximum deformations and improves dynamic behaviour, without exceeding allowable stress levels. Recommendations for monitoring, maintenance and vibration isolation using spring-type anti-vibration mounts are also formulated.

The anchoring installation is one of the most important deck systems, ensuring the safe temporary positioning of a ship in roads, coastal areas or inland waters. Although its configuration may differ from one vessel to another, the design and testing procedures are strongly standardised by the rules of classification societies. This paper presents an overview of the construction and operation of ship anchoring systems and describes the main requirements for testing anchor windlasses, chain stoppers, anchors and associated equipment. The methodology includes factory acceptance tests of the windlass, verification of the electrical drive according to IEC 60034-1, on-board commissioning and sea trial procedures. Particular attention is paid to the performance criteria requested by class rules, such as continuous pulling capacity, short-time overload, hoisting speed, braking capacity and structural integrity of the chain stopper. A practical example of testing a multi-purpose anchor-mooring windlass built by a Romanian manufacturer is discussed, highlighting the measurement of torque, temperatures, rotational speeds and brake performance. The paper underlines the role of proper planning, documentation and coordination between shipyard, equipment manufacturer, Owner and Classification Society to achieve a safe and reliable anchoring installation.

The maritime industry, a significant contributor to global carbon emissions, faces mounting pressure to transition toward sustainable operations through the integration of renewable energy technologies. This study offers a detailed comparative analysis of two solar-powered vessels, MS Tûranor PlanetSolar and Energy Observer, with a focus on their proven design principles, energy systems, and contributions to maritime decarbonization. MS Tûranor PlanetSolar, the first solar-powered vessel to circumnavigate the globe, features a solar-only design powered by 512 m² of photovoltaic panels and a 1,350 kWh lithium-ion battery system. This configuration allows for zero-emission operations but presents limitations in scalability and energy autonomy.In contrast, Energy Observer combines solar panels, wind turbines, and hydrogen fuel cells, showcasing a hybrid energy system capable of producing and storing hydrogen through onboard seawater electrolysis. This approach significantly extends its autonomy and operational versatility, making it more adaptable to diverse environmental conditions. The study evaluates the energy efficiency, environmental impact, and scalability of these vessels, highlighting their role as benchmarks for sustainable maritime engineering. By examining their real-world applications and limitations, the research underscores the importance of hybrid renewable energy systems and optimized designs in accelerating the decarbonization of global shipping. These findings provide critical insights for policymakers, engineers, and industry stakeholders seeking to promote sustainable practices within the maritime sector.

The maritime sector, responsible for approximately 2.5% of global carbon dioxide emissions, faces mounting pressure to implement sustainable practices in line with international decarbonization goals. Wind energy has emerged as a promising solution, with innovative applications being explored to enhance fuel efficiency and reduce emissions. This study undertakes a comparative evaluation of two vessels—Vindskip and Pyxis Ocean—that integrate wind power through distinct technological approaches. Vindskip utilizes an aerodynamic hull design, functioning as a large airfoil to harness wind energy directly for propulsion. This innovative concept has the potential to achieve fuel savings of up to 60% and greenhouse gas emission reductions of approximately 80%. In contrast, Pyxis Ocean employs a wind-assisted propulsion system, utilizing rigid OceanWings sails as a supplementary energy source. This retrofitting approach enables fuel consumption reductions of around 30%, offering a scalable and practical solution for existing vessels. The comparative analysis examines these vessels across critical performance metrics, in cluding energy efficiency, emissions reduction, scalability, and technological maturity. Vindskip exemplifies a forward-looking design for next-generation maritime operations, while Pyxis Ocean demonstrates the feasibility of integrating renewable energy technologies into current fleets. The findings highlight the complementary roles of innovative vessel designs and retrofitting solutions in advancing the maritime industry’s transition to ward a sustainable and low-emission future.

The research in this paper aims to analyze the perception and degree of involvement of employees from a Romanian shipyard in the process of preparing sustainability reports, with a focus on the integration of ESG criteria into organizational performance. The motivation for this study is to understand how directly productive employees within a shipyard see the usefulness of improving sustainability performance by integrating ESG criteria. To conduct this research, the authors used a survey-based analysis method, which was carried out using a questionnaire. This was sent online to target employees, and the defined hypotheses were validated based on the results obtained using IBM SPSS Statistics 22 statistical analysis software. The statistical results have shown that the employees in the analyzed departments perceive the importance of measuring, monitoring, and reporting sustainability performance in the company’s value chain. The originality of the work lies in the fact that this is the first study of its kind to be carried out within a shipyard in our country, with direct implications for the development of future sustainability reports.