Ocean Farming Research Articles

High-performance solar water purification enabled by controlled water convection in integrated porous aerogel multistage distiller

The employment of solar multistage distillers possessing thermal localization and energy cycle properties for saltwater desalination exhibits significant potential in fulfilling the increasing worldwide need for freshwater. In order to prevent salt crystallization on evaporators, most evaporators, however, excessively boost brine exchanging in distiller while ignoring heat loss during water convection. Here, we introduce an interesting porous aerogel-based multistage distiller (PAMS) that effectively suppresses heat loss during saltwater exchanging by controlling the water absorption rate through pore structure devising. This allows us to optimize the balance between evaporation, water transport, and salt-crystallization resistance. Finally, PAMS can reach a remarkable evaporation rate of 5.93 kg m−2h−1 and a high water-collection rate of 4.03 kg m−2h−1 under one solar irradiation thanks to the adjustable balance. Besides, PAMS exhibits impressive long-term stable antibacterial properties, which enhances the anti-biofouling and increases its reliability as a source of freshwater for ocean farm.

Integrity and Safety Factors of Asymmetric Mooring Line Arrangement on Ocean Farm ITS

Integrity and Safety Factors of Asymmetric Mooring Line Arrangement on Ocean Farm ITS

The effects of light, rearing density, and fish size in culturing juvenile Lumpfish

AbstractObjectiveThere is an impetus for increasing Lumpfish Cyclopterus lumpus hatchery production and rearing efficiency due to the high demand for their usefulness as cleaner fish in salmonid ocean farming. One production bottleneck is the loss of juvenile fish due to aggressive behaviors, including cannibalism. Understanding which factors exacerbate Lumpfish aggression and providing mitigation guidelines to aquaculturists are warranted.MethodsTwo experiments were conducted for an 8‐week period in 2022 in 3‐L aquaria with different juvenile size‐classes (4 and 11 g) subjected to three rearing densities (40, 65, and 90 g/L) under different photoperiod regimes (12 h light : 12 h dark [113 lx]; 24 h light : 0 h dark [21 lx]; and 24 h light : 0 h dark [302 lx]), resulting in nine experimental treatments. Survival, growth, and aggression (occurrence and severity of caudal fin nipping) were evaluated.ResultFor 4‐g Lumpfish, light and density significantly affected growth (weight gain and specific growth rate), while an interaction between light and density significantly affected the occurrence of caudal fin nipping but not the degree of fin nipping or survival. None of the tested variables significantly affected 11‐g fish. Generally, a trend toward increased caudal fin nipping occurred in smaller fish (~45% occurrence in 4‐g fish vs. ~20% in 11‐g fish), indicating that cannibalism may be even greater when Lumpfish are smaller than 4 g but abates as the fish grow.ConclusionOur findings indicate that manipulation of lighting at rearing densities of up to 90 g/L can be used to control growth rates in small Lumpfish, often without resulting in increased fish aggression. For small (~4‐g) Lumpfish, constant low light intensity in combination with a low (40‐g/L) rearing density is recommended for reducing growth and caudal fin nipping. However, as Lumpfish grow, these variables are less effective at manipulating fish growth.

Small-scale low-tropic ocean farming and coastal rural landscapes: Why the logistics of seaweed matter? Insights from Ireland for collaborative planning

Kelps are part of large brown macroalgae species with a fundamental role in temperate to subpolar coastal marine ecosystems and their cultivation has been expanding as part of several efforts and countries' policies. This study explores the relevance of post-harvesting logistics planning involving marine operations of emerging seaweed-based supply chains including kelp species. In the Irish context, we explore the potential of collaboration among low-tropic ocean farming sectors regarding shared space and infrastructure in rural and remote landscapes. Based on empirical data and a novel methodological approach, a multi-method analysis was performed involving geographic information systems, mathematical modelling and qualitative content analysis. The results indicate large potential production and collaboration capacity if current licensed areas and existing infrastructure were integrated with kelp cultivation for further processing and distribution in 40 local supply hubs and 14 optimal locations for shared processing facilities. Moreover, the different transportation scenarios considered indicate that costs and greenhouse gas emissions could be minimised by reducing moisture content locally and with increased payload. Further linkages reveal uncertainties in the uses of alternative methods of preservation such as ensiling and a lack of attention to non-market values. For future valorisation in diverse commercial and non-commercial applications, seaweed farming and collaborative processing opportunities still need to be incorporated into societal discourses and futures envisioned by rural coastal communities, including the engagement of young generations in such transformation pathways.

The Design Discussion of a Self-Powered Automatic Identification System Sensor

In recent years, many vessels have utilized Automatic Identification Systems (AIS) to process marine positioning and navigation; the system employs GPS to position and transmits signals through ultra-high frequency wireless communication, which can deliver the signals to a broader range. However, due to the high power-consumption character of AIS, it is necessary to consider an appropriate power supply to support the system. In other words, AIS is suitable for various application fields, but the power supply issue remains unresolved in different Internet of Things (IoT) equipment, such as marine movement or land activity positioning. This article proposes a sensor designed with a self-powered AIS, and the primary functions are: 1. Available for customizing the signal sending time intervals based on the site needs; 2. A panic button is designed in the system for activating AIS signal transmission; 3. The equipment stores electricity in solar panels to improve the power consumption issue of AIS; 4. The g-sensor installed in the equipment detects and judges AIS motion and wobble to position the vessel. The AIS equipment presented in this research mainly applies to positioning marine and mountain activities or ocean farming. Due to the lack of power supply in the applications mentioned above, if AIS cannot deliver signals for a long time, the equipment will influence the power issue of other detectors in the entire design. Therefore, this study discusses a design combined with a self-powered AIS detector, allowing the AIS equipment to operate for a year and be suitable for various applications. This design can resolve the lack of mobile communication issues on the sea or in the mountain.

Elucidation and quantification health-promoting phenolic compounds, antioxidant properties and sugar levels of ultrasound assisted extraction, aroma compositions and amino acids profiles of macroalgae, Laurencia papillosa

Currently, sustainability is one of the most critical issues confronting society today. The growing of macroalgae in ocean farms appears more sustainable than agriculture on land due to it does not require any fresh water, chemical fertiliser, or soil. Macroalgae have been shown to be a sustainable marine source of amino acids, novel bioactive phenolic and aroma compounds that can be exploitation in food, cosmetic, nutraceuticals, pharmacological applications. Despite starting the huge cultivation of macroalgae in world, bioactive compounds in the edible macroalgae have not been well characterized. Ultrasound assisted extraction (UAE) and conventional extraction (CE) techniques were compared and red macroalgae, L. papillosa extracts were characterized. The highest amount of amino acid was glutamic acid (GLU) and composed of 35% was essential amino acids. UAE at 10% amplitude for 15 min showed significantly highest (p < 0.05) phenolic (212.03±3.03 mg gallic acid equivalent/100 g) as well as antioxidant activity determined by DPPH (105.69±3.02 µmol Trolox/100 g), ABTS (238.69±2.23 µmol Trolox/100 g) radical assay and FRAP value (72.47±3.13 µmol Trolox/100 g) when in comparison with CE. Furthermore, bioactive compounds in extracts were indicated as phlorotannins, flavonoids, phenolic acids and other polyphenols using liquid chromatography coupled to diode array detection and electrospray ionisation tandem mass spectrometry (LC-DAD-ESI-MS/MS). This result confirmed higher antioxidant capacity detected with the UAE. A total of 46 volatile organic compounds were identified and quantified by GC-FID/MS with HS-SPME system. This study emerges as first report to novel extraction method used and deeply characterization of L papillosa. The results seem that significant potential application in the functional food, active packaging and nutraceuticals industry.

Mooring Analysis of Ocean FarmITS (OFITS)

Ocean Farm ITS (OFITS) is a pilot project of offshore aquaculture designed by Institut Teknologi Sepuluh Nopember (ITS) which will be installed at Sidoasri Beach, Malang Districts. OFITS structure is an integration of fish cages with ecotourism facilities. This paper describes the mooring analysis for OFITS installation. The mooring configuration uses a rectangle grid consisting of 4 mooring buoys, 8 top inner mooring grids, and 14 mooring lines arranged symmetrically. The mooring line uses a type of nylon line with a size of 42 mm in diameter and 70 m in length. Five mooring lines on the front side and two mooring lines on the back side secure the moored buoy to the seafloor. The maximum capacity of buoy is 3 tons. The anchor for mooring uses an anchor with a weight of 0.25 tons for each anchor. The purpose of this analysis is to obtain the maximum tension of the mooring rope at OFITS based on extreme environmental loads. This analysis uses the time domain analysis method.

Chromosome-Level Genome Assembly of the Blue Mussel Mytilus chilensis Reveals Molecular Signatures Facing the Marine Environment.

The blue mussel Mytilus chilensis is an endemic and key socioeconomic species inhabiting the southern coast of Chile. This bivalve species supports a booming aquaculture industry, which entirely relies on artificially collected seeds from natural beds that are translocated to diverse physical-chemical ocean farming conditions. Furthermore, mussel production is threatened by a broad range of microorganisms, pollution, and environmental stressors that eventually impact its survival and growth. Herein, understanding the genomic basis of the local adaption is pivotal to developing sustainable shellfish aquaculture. We present a high-quality reference genome of M. chilensis, which is the first chromosome-level genome for a Mytilidae member in South America. The assembled genome size was 1.93 Gb, with a contig N50 of 134 Mb. Through Hi-C proximity ligation, 11,868 contigs were clustered, ordered, and assembled into 14 chromosomes in congruence with the karyological evidence. The M. chilensis genome comprises 34,530 genes and 4795 non-coding RNAs. A total of 57% of the genome contains repetitive sequences with predominancy of LTR-retrotransposons and unknown elements. Comparative genome analysis of M. chilensis and M. coruscus was conducted, revealing genic rearrangements distributed into the whole genome. Notably, transposable Steamer-like elements associated with horizontal transmissible cancer were explored in reference genomes, suggesting putative relationships at the chromosome level in Bivalvia. Genome expression analysis was also conducted, showing putative genomic differences between two ecologically different mussel populations. The evidence suggests that local genome adaptation and physiological plasticity can be analyzed to develop sustainable mussel production. The genome of M. chilensis provides pivotal molecular knowledge for the Mytilus complex.

Hypoxia stress induces hepatic antioxidant activity and apoptosis, but stimulates immune response and immune-related gene expression in black rockfish Sebastes schlegelii

Dissolved oxygen concentrations both in the open ocean and coast have been declining due to the interaction of global climate change and human activity. Fish have evolved different adaptative strategies to cope with possibly damage induced by hypoxic environments. Black rockfish as important economic fish widely reared in the offshore sea cage, whereas related physiological response subject to hypoxia stress remained unclear. In this study, hepatic anti-oxidant enzymes (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GSH-Px]), aminotransferase (AST) and alanine aminotransferase (ALT) activities, lipid peroxidation (LPO), malondialdehyde (MDA) and glutathione (GSH) content, immunological parameters and the expression of apoptosis (bax, bcl2, p53, caspase3, xiap) and immune-related genes (c3, il-1β, ccl25, saa, hap, isg15) of black rockfish were determined during hypoxia and reoxygenation to illustrate the underlying defense response mechanisms. Results showed that hypoxia stress remarkably increased hepatic LPO and MDA content, AST and ALT activity and proportion of pyknotic nucleus. Hepatic SOD, CAT and GSH-Px activity manifested similar results, whereas GSH levels significantly decreased under hypoxia stress. The apoptosis rate of hepatocyte increased during hypoxia stress and reoxygenation. Meanwhile, p53, caspase3, bax and xiap mRNAs and bax/bcl2 rations were significantly up-regulated under hypoxia stress. However, bcl2 mRNA was significantly down-regulated. Interestingly, hypoxia stress significantly increased NBT-positive cell percent, phagocytic index, respiratory burst and ACH50 activity, and lysozyme activity. The mRNA levels of c3, ilβ, ccl25, saa, hap and isg15 were significantly up-regulated in the liver, spleen and head-kidney under hypoxia stress. The above parameters recovered to normal status after reoxygenation for 24 h Thus, hypoxia stress impairs hepatic antioxidant capacity, induces oxidative damage and apoptosis via the xiap-p53-bax-bcl2 and the caspase-dependent pathways, but enhances host immunity by regulating nonspecific immune indices and related genes expression to maintain homeostasis in black rockfish. These findings will help fully understand the hypoxia tolerance mechanisms of black rockfish and provide more data for offshore open ocean farming.

Eisenia arborea (Areschoung) domestication and mariculture development on the Pacific coast of Baja California, México

Eisenia arborea (sensu Ecklonia arborea) is the kelp with the greatest latitudinal distribution on the Northeastern Pacific Coast. It is harvested in Mexico in small amounts for abalone farm fodder and occasionally exported to Asia for human consumption. Because the high-energy environment where it naturally grows limits its sustainable harvest, we explored the domestication and cultivation of this kelp on the west coast of Baja California, Mexico. The life history of E. arborea was completed in the laboratory following traditional methods for kelp cultivation. Gametophytes became reproductive approximately 50 days after spore release and sporophytes were visible to the naked eye after 80 days. When sporophytes reached 2–3 cm, they were transplanted to two sites on long-line systems: in an open bay (Todos Santos Bay) and in a shallow coastal lagoon (San Quintín Bay). At both sites, full differentiation occurred 6 to 8 months after deployment, with fertile blades occurring within a year. Once individuals reached maximum size, blades were harvested by pruning. Monthly, regrowth of pruned blades and new blade addition were measured. Pruned individuals reached the same weight as controls in three months. On the basis of these results, a seasonal seeding program was implemented at a third site where the presence of natural Eisenia is rare due to the lack of hard substrate but was hypothesized to provide appropriate conditions for kelp cultivation (Santa María Bay). Cultures were deployed at three different depths and growth was correlated with season, depth, and temperature. Only cultures seeded in winter developed successfully at this site. This study shows that the culture of E. arborea in a variety of ocean conditions is possible; however, site selection and seasonality are important considerations. Because E. arborea is perennial, it can be harvested periodically during the year thereby increasing yield, and because it is the warmest tolerant kelp species, it is an ideal target for ocean farming and commercial cultivation, considering climate change.

Exploratory environmental assessment of large-scale cultivation of seaweed used to reduce enteric methane emissions

Animal husbandry contributes to roughly 15% of total anthropogenic GHG emissions, of which the majority originates from methane emissions associated with ruminant enteric fermentation. Recent studies have shown that methane emissions from ruminants can be heavily reduced (up to 90% reduction) by introducing the seaweed Asparagopsis taxiformis in the feed composition. The largest hurdle in implementing a wider use of the seaweed feed supplement is to scale up the production. Today most of the production is performed in extensive ocean farming systems. In the small coastal city Lysekil, located on the Swedish west coast, an initiative for a land-based seaweed production system is currently in progress. In this study, Life Cycle Assessment (LCA) methodology was applied to assess the environmental impact of this production system. The assessment included all important stages in the seaweed production system, from cradle to farmgate. The results showed that a large part of the assessed impacts were attributed to the salt (NaCl) sourcing needed to increase the salinity to achieve optimal growing conditions. In the default scenario, the salt input contributed to 48% of the total GHG emissions. The scenario analysis showed that lower emissions could be obtained by changing the salt source from rock salt, sourced in Denmark, to sea salt sourced by using evaporation ponds in France. Moreover, increasing the water recycling rate could reduce salt demand and consequently the environmental impact. The results also displayed a large thermal energy demand used to increase the temperature in the water to more fitting conditions. Despite this, the environmental impact from thermal energy was relatively low, causing 16% of the total GHG emissions. The reason for this was explained by the use of low-impact district heating, mostly reliant on the excess heat from the local oil refinery. The scenario analysis showed that choices regarding thermal energy source and allocation method significantly impacted the overall results of the assessment. Furthermore, we argue that although the environmental impact from the excess heat from the oil refinery displayed low impact, the seaweed farm should consider using other thermal energy sources, since it is difficult to foresee the impact of the excess heat from the petrochemical industry as its main products are being phased out in decarbonization and climate neutrality schemes. An alternative thermal energy source with promising results was electric heat pumps powered by wind. We concluded that LCA methodology could be an important tool to optimize production systems before they are brought into operation.

Repurposing face mask waste to construct floating photothermal evaporator for autonomous solar ocean farming

AbstractPlastic waste caused by the extensive usage of face masks during COVID‐19 pandemic has become a severe threat to natural environment and ecosystem. Herein, an eco‐friendly approach to repurpose face mask waste for clean water production via solar thermal evaporation is proposed. By taking advantage of its interwind structure, face mask holds the promise to be an ideal candidate material for constructing photothermal evaporator. In‐situ surface modifications are performed successively with polyvinyl alcohol and polypyrrole to improve its wettability and solar absorption (97%). The obtained face mask‐based evaporator achieves significantly enhanced solar efficiency (91.5%) and long‐term salt‐rejection stability. The harvested clean water befits plant growing to enable farming on sea surface. A floating photothermal evaporation prototype is then developed to demonstrate autonomous solar ocean farming, with plants successfully cultivated over time. As such, the proposed strategy provides a promising solution towards ecological sustainability by tapping multiple benefits.image

Predicting oxygen levels in Atlantic salmon (Salmo salar) sea cages

Dissolved oxygen (DO) concentration is an important factor affecting fish welfare and growth in Atlantic salmon sea cages. As an operational prediction tool, and to aid our understanding of how DO concentrations are affected by cage size, shape and design interacting with the fish biomass and environmental conditions, we have developed a mathematical model based on the advection-diffusion equation for 3D estimates of DO levels. The model requires input of farm geometry, ambient oxygen levels, current speed and direction, feeding rates, fish distribution and biomass statistics.The model has been tested for Salmar's Ocean Farm 1, a large production unit dimensioned for 1.5 million fish and designed for coping with exposed environmental conditions, and performs well in comparison with DO measurements, particularly at low to moderate current speeds. Although the model produces realistic outputs with the simple inputs that are available, detailed information about fish behaviour and current conditions within the cage is likely to improve model accuracy.In addition to being a useful tool for better monitoring of oxygen conditions in fish farms, the present model can, given the appropriate inputs, be used as a forecasting tool for predicting the risk of hypoxic conditions in cages, and to evaluate the risks of hypoxic conditions in new types of open, semi-closed or closed production systems.

Sustainable Large-Scale Aquaculture of the Northern Hemisphere Sea Lettuce, Ulva fenestrata, in an Off-Shore Seafarm

The growing world population demands an increase in sustainable resources for biorefining. The opening of new farm grounds and the cultivation of extractive species, such as marine seaweeds, increases worldwide, aiming to provide renewable biomass for food and non-food applications. The potential for European large-scale open ocean farming of the commercial green seaweed crop Ulva is not yet fully realized. Here we conducted manipulative cultivation experiments in order to investigate the effects of hatchery temperature (10 and 15 °C), nutrient addition (PES and 3xPES) and swarmer density (500 and 10,000 swarmers ml−1) on the biomass yield and biochemical composition (fatty acid, protein, carbohydrate, pigment and phenolic content) of off-shore cultivated Ulva fenestrata in a Swedish seafarm. High seedling densities were optimal for the growth of this northern hemisphere crop strain and significantly increased the mean biomass yield by ~84% compared to low seedling densities. Variations of nutrients or changes in temperature levels during the hatchery phase were not necessary to increase the subsequent growth in an open-water seafarm, however effects of the factors on the thallus habitus (thallus length/width) were observed. We found no significant effect of the environmental factors applied in the hatchery on the total fatty acid or crude protein content in the off-shore cultivated Ulva. However, low seedling density and low temperature increased the total carbohydrate content and furthermore, high temperature in combination with high nutrient levels decreased the pigment content (chlorophyll a, b, carotenoids). Low temperature in combination with high nutrient levels increased the phenolic content. Our study confirms the successful and sustainable potential for large-scale off-shore cultivation of the Scandinavian crop U. fenestrata. We conclude that high seedling density in the hatchery is most important for increasing the total biomass yield of sea-farmed U. fenestrata, and that changing temperature or addition of nutrients overall does not have a large effect on the biochemical composition. To summarize, our study contributes novel insights into the large-scale off-shore cultivation potential of northern hemisphere U. fenestrata and underpins suitable pre-treatments during the hatchery phase of seedlings to facilitate a successful and cost-efficient large-scale rope cultivation.

Adaptive phyconomy for sustainable management of coastal ecoscapes in Indonesia

Adaptive phyconomy supports holistic, sustainable marine ecoscape development as a component of integrated coastal area management (ICAM). Phyconomy is the branch of applied phycology that comprises systems of art, science and technology applied to production systems that yield crops of algae. Through the macroalgae known as “seaweeds”, farmers turn seawater, sunshine, and effort into money. Adaptive marine phyconomy of tropical red seaweeds is an outstanding example of large-scale crop production that developed primarily from simple methods refined by farmers in the sea, but as of 2020 it is, still much more art than science. Phyconomy, ecoscape issues and market issues are intertwined in a way that demands holistic planning and management. Every phyconomy action is influenced not only by energy and materials issues, but also by issues among value chain stakeholder alliances. Ocean farming functions take place under conditions where environmental and socio-economic conditions are often uncertain, therefore adaptive approaches must be applied in a way that is resilient and sustainable. The present paper discusses how adaptive phyconomy art and science is being developed as a fundamental component of integrated coastal area management for sustainable marine ecoscape development in Indonesia.

Numerical modelling of hydrodynamic responses of Ocean Farm 1 in waves and current and validation against model test measurements

With the continuous growing of the aquaculture industry and increasingly limited fish farming sites at close to shore areas both in Norway and worldwide, there is a need to develop fish farms suitable for aquaculture production in typical offshore environments. For this purpose, SALMAR has developed and deployed the Ocean Farm 1 facility for offshore fish farming.The main purpose of this paper is to develop a reliable numerical model and investigate the motion responses of the Ocean Farm 1 structure in waves and current. The established numerical model consists of the Ocean Farm 1's frame structure (with rigidly-connected circular column components), the net and the mooring system. The hydrodynamic external loads and coefficients of the frame structure are obtained by using potential flow theory. The quadratic drag load on the individual circular columns of the frame structure is formulated by a given drag coefficient. The loads on the net are formulated by using the screen model, where the Reynold number dependent lift and drag forces are formulated as a function of the solidity ratio Sn of the net, relative inflow angle and velocity. The hydrodynamic loads on the mooring lines are formulated using the Morison's equation and the structural responses of the mooring lines are obtained using a nonlinear FE model.With the developed numerical model, time domain simulations are performed. The simulation results are firstly validated against measured data from the decay tests, current tests, and regular wave tests. After the validation, numerical simulations are performed in different irregular wave and current combined weather conditions and the obtained motion response of Ocean Farm 1 are discussed and compared with available measurement data.

Comparative analysis of morphometric traits of farmed sugar kelp and skinny kelp, Saccharina spp., strains from the Northwest Atlantic

AbstractOur team has initiated a selective breeding program for regional strains of sugar kelp, Saccharina latissima, to improve the competitiveness of kelp farming in the United States. Within our breeding program, we also include an endemic putative species, Saccharina angustissima, locally referred to as skinny kelp. We crossed uniclonal gametophyte cultures derived from 37 wild‐collected blades representing five sugar kelp strains and one skinny kelp strain to produce 104 unique crosses. Each cross was outplanted on a near‐shore research farm located in the Gulf of Maine (GOM). After the first farming season, our results indicated that sugar kelp and skinny kelp were interfertile, and produced mature and reproductively viable sporophytes. Morphological traits of individual blades varied depending on the parental contribution (sugar vs. skinny), with significant differences found in progeny blade length, width, thickness, and in stipe length and diameter. Despite these differences, wet weight and blade density per plot showed no statistical differences regardless of the cross. Given their published genetic similarity and their interfertility shown here, S. angustissima and S. latissima may not be different species, and may each contribute genetic diversity to breeding programs aimed at meeting ocean farming and market needs.

Highly efficient biosynthesis of l-ornithine from mannitol by using recombinant Corynebacterium glutamicum

Mannitol is a promising six-carbon sugar alcohol that is widely found in macroalgae. The potential of mannitol as a renewable raw material is of interest due to the advantages of ocean farms. Herein, the biobased production of l-ornithine from mannitol was resoundingly demonstrated for the first time in engineered Corynebacterium glutamicum S9114 through the deletion of the mannitol repressor MtlR. By modulating the expression of mtlD and reinforcing the fructose metabolic pathway, we generated the strain MTL13 that produced 54.56 g/L of l-ornithine with a yield of 0.47 g/g on mannitol. These results illustrate the robust conversion from mannitol to l-ornithine using engineered Corynebacterium glutamicum, providing a reference for the biobased production of additional chemicals from mannitol.

Study on Mooring Design and Calculation Method of Ocean Farm Based on Time-Domain Potential Flow Theory

In order to calculate the mooring force of a new semi-submerged Ocean Farm quickly and accurately, based on the unsteady time-domain potential flow theory and combined the catenary model, the control equation of mooring cable is established, and the mooring force of the platform under the wave spectrum is calculated. First of all, based on the actual situation of the ocean environment and platform, the mooring design of the platform is carried out, and the failure analysis and sensitivity analysis of the single anchor chain by the time domain coupling method are adopted: including different water depth, cycle, pretension size, anchor chain layout direction and wind speed, etc. The analysis results confirm the reliability of anchoring method. Based on this, the mooring point location of the platform is determined, the force of each anchor chain in the anchoring process is calculated, and the mooring force and the number of mooring cables are obtained for each cable that satisfies the specification, the results of this paper can provide theoretical calculation methods for mooring setting and mooring force calculation of similar offshore platforms.

Optimal Predictive Maintenance Policy for an Ocean Wave Farm

The levelized cost of electricity for wave energy converters (WECs) is high and one important way to reduce this cost is to employ strategies that minimize the cost of maintenance of WECs in a wave farm. In this paper, an optimal maintenance strategy is proposed for a group of WECs, resulting in an adaptive scheduling of the time of repair, based on the state of the entire farm. The state-based maintenance strategy seeks to find an optimal tradeoff between the moderate revenue generated from a farm with some devices being in a deteriorated or failed state, and the high repair cost that typifies ocean wave farm maintenance practices. The formulation uses a Markov decision process approach to devise an optimal policy, which is based on the count of WECs in different operational states. The effectiveness of the proposed approach is computationally demonstrated on the maintenance of an ocean farm consisting of 30 WECs.