Letteratura scientifica selezionata sul tema "Semi-commercial farmers"

Maize constitute dominant food crop in upland semi-arid region of East Nusa Tenggara (ENT) and as a main staple for majority of rural farmers. This paper examines Provincial Government programs to increase maize production and to reform maize production orientation. Data and information being used from the recent program: “Maize Planting, Cattle Harvest (MPCH)”. The survey was conducted in all villages in Districts of Timor and Sumba Island as pilot project. The study showed that: 1). Maize farmers keen to change production orientation from subsistence to semi and fully commercial as long as there are surplus production and better access to the market, 2). Average maize productivity of farmers under program (5 – 8 ton/ha) higher than traditional practices (1 – 2 ton/ha), 3). Most farmers under the program have access to have own cattle 1- 2 head/household from surplus production of maize sold with contract price IDR 3,200/kg. This result implies that incorporated farmer into the market from the beginning of the program, technical assistance to apply appropriate innovations, organized farmers groups to enhance business scale and government support to minimize production cost lead farmers to adopt new innovation, increase maize production and change maize production orientation (commercial).

Indigenous technical knowledge (ITK) are based on the experiences of the local people being passed on from one generation to next and has been used for management of pest since ancient times. A study was conducted to collect and document the ITK and their application in pest management from indigenous communities in western mid hill of Nepal. A total sample size of seventy-five respondents from the indigenous communities of Magar, Gurung, and Newar in Tanahun, Lamjung and Kaski districts of Nepal were interviewed with a semi structured questionnaire. The study revealed that subsistence farmers and semi commercial farmers usually made the most use of ITK while commercial farmers rarely used such indigenous knowledge. Use of ITK was highest (85%) by the subsistence farmers, followed by semi-commercial farmers (60%), and lowest (10%) by commercial farmers in pest management. The transfer of ITK was mostly found to be through past generations. The indigenous technological knowledge being applied in pest management should be documented, promoted, and encouraged in combination with scientific knowledge among the farming communities. SAARC J. Agri., 18(1): 251-261 (2020)

A survey was undertaken to examine the accessibility of aqua-drugs and their applications in the semi-intensive aquaculture farms in Patuakhali district. A total of 83 stakeholders were selected and data gathered from aqua-medicine stores, representatives of different pharmaceuticals and semi-intensive aqua-farms owners via questionnaire interviews. PRA tools like focused group discussion, cross-checking, and key informant interviews were also used. Results show that 78% of farmers conduct polyculture and rest executes monoculture. Among the total fish farmer majority, 38% used lime for pond preparation and water quality management and potash used by 44% farmer as a disinfectant. For increasing dissolve-oxygen Oxy-rich (26%) was vastly used while 28% of farmers don’t use any oxygen supplier in their pond. However, 14% of farmers use commercial Megavit-Aqua growth promoters and 14% farmer used probiotics. For disease control, 52% and 14% of farmers use Renamycin and Renamox respectively due to its easy availability and affordability compared to probiotics. Several issues have been reported due to improper use of aquatic medications, such as lack of information about chemical use, sufficient dosage, form of application and indiscriminate use of antibiotics. This research result will help the policymaker to understand the requirement of fishers for healthy and sustainable aquaculture practices.

Institutional changes in Benin have brought to light farmers' demand for varieties better suited to local growing conditions than existing ones. In response, we initiated a participatory cotton breeding experiment in 1996 to evaluate the relevance of such a methodology for the improvement of a commercial crop grown under rain-fed, semi-intensive cropping systems. This paper compares the performance of the first four mass-selection cycles, implemented by three farmer-breeders (F-B) and one formal breeder, with the original population and two commercial controls over three sites and two years. First results show that genetic changes occurred in all the F-B populations. The highest yielding F-B population (Savalou) was also more exuberant and later maturing than the others. Within the relatively narrow range of environments considered in the trial, there is no evidence that decentralized breeding results in better local adaptation. In Benin, participatory cotton breeding may be considered as complementary to formal on-station breeding and useful for enlarging the genetic variability offered to the farmers. Although the farmers want the approach to be scaled-up, its sustainability relies on a formal partnership between research and farmers institutions.

Smallholder livestock farmers across Sub-Saharan Africa are racing against time to find cheaper, nutritious, and sustainable feed alternatives to the more pronounced and expensive commercial concentrates amidst the increasing global demand for livestock products. Lately, many prominent feed conservation technologies have been developed, with a notable example being the sweetpotato silage technology that turns wasted sweetpotato components into a palatable and nutritious livestock feed. However, despite the potential benefits associated with these technologies, the level of demand and acceptance among smallholder farmers remains largely unknown. Thus, this paper assesses the farmer demand and willingness-to-pay (WTP) for sweetpotato silage-based diet as pig feed by smallholder farmers in Uganda. The information for the study was collected through secondary data review and semi-structured interviews to assess farmer WTP. The 256 semi-structured interviews were randomly drawn from 16 purposive clusters formed at a radius of 3 km around 16 farmers piloting sweetpotato silage-based diets for pig feed. The results show that pig farming is mainly the responsibility of women, with farmers’ mean willingness-to-pay price amounting to 0.20 USD per kilogram of sweetpotato silage-based diet. At the mean price, the annual demand for silage was estimated at 17,679 tons, with a market potential of approximately 3.59 million USD. The study concludes that, at the mean willingness-to-pay price, there is a substantial market potential that can be exploited by small and medium-sized enterprises (SMEs) venturing in the livestock feed industry.

Policy of providing chemical fertilizers at low prices through the subsidies continue to increase every year, causing inefficient use of fertilizers by farmers and in turn lower the productivity of the land. The study was conducted in the province of West Java and Central Java in 2012, aims to (1) evaluate the costs and revenues of non commercial organic fertilizer and (2) analyzing farm income and the factors that affect rice production. Total farmer respondents interviewed 60 farmers with 30 farmers who earn program Organic Fertilizer Processing Unit (UPPO) and 30 farmers who do not follow the program UPPO. To determine the effect of the use of organic fertilizers used in rice cultivation model of linear production function CobbDouglas and financial analysis or benefit cost ratio (B/C). The results showed good organic fertilizer production enterprises in the form of solid or liquid organic fertilizer is quite profitable. Farmers earn net income of Rp. 83-112 per kg of organic fertilizer in 6 weeks. The amount of chemical fertilizers used on semi-organic rice farming is reduced by approximately 50% of the amount of chemical fertilizers used in nonorganic farming. The use of labor in semi-rice organic farming is higher than nonorganic farming, especially at the stage of cultivation and weeding. R/C ratio of semiorganic rice farming is greater than non-organic rice which indicates that the semiorganic rice farming more profitable financially.

Stock theft is among the major challenges faced by livestock farmers in South Africa. It has severe consequences especially for smallholder farmers, who collectively own a large share of the South African livestock herds but individually keep small herds. In recent years, technological improvements and innovations have made it possible to track livestock movements by using GPS animal tracking devices. Low-cost GPS has been developed and used elsewhere and in the local commercial sector. Given the well-known role of extension, i.e. information and technology dissemination, the possibility that smallholders adopt GPS animal tracking devices should be evaluated. However, very few studies have made a case for using this technology in curbing stock theft among smallholder farmers. This review therefore addresses the likelihood that smallholder livestock farmers in South Africa adopt GPS animal tracking devices to mitigate the impact of stock theft. Using a semi-systematic and a snowball literature review approach, we consulted and reviewed the relevant literature and official statistics relating to stock theft and smallholder livestock farming. Results from the reviewed literature suggest that the likelihood of GPS animal tracking device adoption by smallholders will depend on a) the awareness about the devices and how they work, b) the acuteness of stock theft for a farmer and how livestock contributes the farmer’s livelihood, and c) the income level, access to mobile phones and risk behaviour of farmers. Our literature findings identify areas for future research and may help agricultural extension personnel with future research topics.

The relevance of farmyard animal development activities is debatable. Is there a middle course that can be followed between free-ranging systems, where animals have to fend for themselves, and large-scale commercial units? From a technical point of view there are many possibilities for increasing production in free-ranging or semi-commercial farmyard animal keeping in developing countries. The inputs required and the increase in production mean that farmers will have to become more market-oriented, and to compete with other small farmers and large-scale operators. It is of the utmost importance that the socio-economic setting for farmyard animal interventions is properly understood and appreciated.

The rural scenario in India is undergoing a rapid change, from the traditional concept of farming as a subsistence activity into a vibrant, commercial, economic venture enabling the farmers to live in dignity and prosperity. During the past four decades, the annual output of eggs has gone up by over eight times, and hence the marketing of poultry is the fast-growing industry. The development of farming has been given priority to help small rural farmers in the unorganized sector. It is also planned to ensure easy access to all necessary facilities, including inputs, credit and marketing. Hence, a study of the poultry industry and its commercial viability is of particular importance. Poultry farming is undertaken by thousands of rural as well as semi-urban masses. Poultry farming with low capital investment generates employment opportunities for rural and semi-urban people. With the new occupation and employment generation, the standard of living has considerably created a social impact.

Soil management practices determine the long term productivity of soil. A comparative study of commercial organic and conventional vegetable farming systems was carried out to find out impact of different farming systems on soil properties. This study was executed in Kathmandu valley (Kathmandu, Bhaktapur and Lalitpur districts) among 30 organic and 30 conventional commercial vegetable farmers. Semi-structured questionnaire survey and soil physical and chemical analysis were performed to gather the required information. Results showed that bulk soil pH was significantly higher in the organic field than in the conventional field. Soil organic matter and available soil potassium were significantly higher in amount in the organic farm than in the conventional farm. Total soil nitrogen content and available soil nitrogen content were significantly higher in amount in the conventional farm than in the organic farm. Conventional farmers were applied significantly higher amount of chicken manure and biozyme as compared to organic farmers. Organic farmers applied significantly higher amount of urban compost and bone meal as compared to conventional farmers. Farmers perceived productivity was increasing in trend in the organic farms whereas it was declining in the conventional farms.DOI: http://dx.doi.org/10.3126/njst.v15i1.12005 Nepal Journal of Science and TechnologyVol. 15, No.1 (2014) 13-22

An exploration of the creation and use of farmers' commonly used "rules of thumb" is required to conceptualize farmers' decision making processes. While farmers face complex situations, particularly when subsistence is an issue, they do appear to use simple rules in their decision making. To date inadequate attention has been given to understanding their reasoning processes in creating the rules, so this study traces the origins of farmers' beliefs, and extracts the decisive and dynamic elements in their decision making systems to provide this understanding. The analysis was structured by using a model based on the Theory of Planned Behaviour (TPB). Modifications included recognizing a bargaining process (BP) and other decision stimuli to represent socio-cultural influences and sources of perception, respectively. Two analyses based on the Personal Construct Theory (PCT) and the Ethnographic Decision Tree Modelling (EDTM) were also applied to help elaborate the farmers' cognitive process and actual decision criteria. The method involved interviews in two villages in Lamongan Regency in East Java Province of Indonesia, where the farmers adopted an improved paddy-prawn system ("pandu"). The results highlighted that farmers use rational strategies, and that socio-cultural factors influence decision making. This was represented by interactions between the farmers' perceptions, their bargaining effort, and various background factors. The TPB model revealed that the farmers' perceptions about the potential of "pandu", and the interaction with their "significant others", influenced their intention to adopt "pandu". The farmers appeared to prefer a steady income and familiar practices at the same time as obtaining new information, mainly from their peers. When "pandu" failed to show sufficiently profitable results, most farmers decided to ignore or discontinue "pandu". This became the biggest disincentive to a wide and sustainable adoption. However, the PCT analysis showed that part of this problem also stemmed from the farmers' lack of resources and knowledge. The farmers' restrictive conditions also led them to seek socio-cultural and practical support for their actions. This was highlighted by a bargaining process (BP) that integrated what the farmers had learned, and believed, into their adoption behaviour. The BP also captured the farmers' communication strategies when dealing with "pandu" as its adoption affected resource allocation within the family and required cooperation with neighbours. The PCT and EDTM analyses also confirmed how the BP accommodated different sets of decision criteria to form different adoption behaviours. Such a process indicated the importance of considering the adoption decision and the relevant changes resulting from the farmers' cognition. This provided a more dynamic and realistic description of the farmers' decision-making process than has previously been attempted. Overall, the results suggested that semi-commercial farmers need to know, and confirm, that a new technology is significantly superior to the existing system, and can provide a secure income. The introduction of a new technology should use a participatory approach allowing negotiation, conflict mitigation and the creation of consensus among the relevant parties. This can be supported through better access to knowledge, information and financing. A specific and well-targeted policy intervention may also be needed to accommodate the diversity in the farmers' ways of learning and making decisions. Ways to improve the current analytical approaches are also suggested.

An exploration of the creation and use of farmers' commonly used "rules of thumb" is required to conceptualize farmers' decision making processes. While farmers face complex situations, particularly when subsistence is an issue, they do appear to use simple rules in their decision making. To date inadequate attention has been given to understanding their reasoning processes in creating the rules, so this study traces the origins of farmers' beliefs, and extracts the decisive and dynamic elements in their decision making systems to provide this understanding. The analysis was structured by using a model based on the Theory of Planned Behaviour (TPB). Modifications included recognizing a bargaining process (BP) and other decision stimuli to represent socio-cultural influences and sources of perception, respectively. Two analyses based on the Personal Construct Theory (PCT) and the Ethnographic Decision Tree Modelling (EDTM) were also applied to help elaborate the farmers' cognitive process and actual decision criteria. The method involved interviews in two villages in Lamongan Regency in East Java Province of Indonesia, where the farmers adopted an improved paddy-prawn system ("pandu"). The results highlighted that farmers use rational strategies, and that socio-cultural factors influence decision making. This was represented by interactions between the farmers' perceptions, their bargaining effort, and various background factors. The TPB model revealed that the farmers' perceptions about the potential of "pandu", and the interaction with their "significant others", influenced their intention to adopt "pandu". The farmers appeared to prefer a steady income and familiar practices at the same time as obtaining new information, mainly from their peers. When "pandu" failed to show sufficiently profitable results, most farmers decided to ignore or discontinue "pandu". This became the biggest disincentive to a wide and sustainable adoption. However, the PCT analysis showed that part of this problem also stemmed from the farmers' lack of resources and knowledge. The farmers' restrictive conditions also led them to seek socio-cultural and practical support for their actions. This was highlighted by a bargaining process (BP) that integrated what the farmers had learned, and believed, into their adoption behaviour. The BP also captured the farmers' communication strategies when dealing with "pandu" as its adoption affected resource allocation within the family and required cooperation with neighbours. The PCT and EDTM analyses also confirmed how the BP accommodated different sets of decision criteria to form different adoption behaviours. Such a process indicated the importance of considering the adoption decision and the relevant changes resulting from the farmers' cognition. This provided a more dynamic and realistic description of the farmers' decision-making process than has previously been attempted. Overall, the results suggested that semi-commercial farmers need to know, and confirm, that a new technology is significantly superior to the existing system, and can provide a secure income. The introduction of a new technology should use a participatory approach allowing negotiation, conflict mitigation and the creation of consensus among the relevant parties. This can be supported through better access to knowledge, information and financing. A specific and well-targeted policy intervention may also be needed to accommodate the diversity in the farmers' ways of learning and making decisions. Ways to improve the current analytical approaches are also suggested.

Text in English
Cow size influences biological efficiency of individual animals, which influences herd composition and stock flow. This in turn influences the economic efficiency of the herd. This research followed the thread from animal size, to biological efficiency, to economic efficiency for beef cattle production under a typical production system in semi-arid South Africa. Cattle were grouped into three groups namely small, medium and large cattle, with mature weights of 300kg, 450kg and 600kg respectively. The net energy requirements of individual cattle were calculated for maintenance, growth, lactation and foetal production, for each of the three sizes. Growth rates, milk yield, reproduction rates, and management practices were assumed from existing research. Next the stock flow for a herd of small, medium and large cattle were calculated from the above. Income and expenses as commonly used in the research area were calculated from the stock flow. Gross profit above allocated costs were subsequently calculated for the three herds under the above-mentioned conditions. When assuming similar reproduction and growth rates for small, medium and large mature cattle, the following results were obtained: more heads of small cattle could be held on a set resource base, but the total live weight of a herd of large cattle that could be held on the same resource base was greater. This was mostly due to proportionately lower maintenance energy requirements in the herd of large cattle. In the simulation in this study, maintenance energy requirements for the herd of large cattle was 71.2%, compared to 72.0% for the herd of medium cattle and 73.1% for the herd of small cattle. Income from the herd of small cattle was the lowest, as less kilograms of beef were available to sell. Allocated costs for the herd of small cattle were the highest, due to a large number of expenses being charged per head of cattle. As a result, the herd of large cattle were more economically efficient than their smaller counterparts. Income above allocated costs for the herds of large, medium and small cattle were R1,182,865, R1,085,116 and R946,012 respectively. Larger cattle generally have a lower reproduction rate under similar conditions. No equation exists that directly links size to reproduction rates, especially considering the vast number of variables that influences reproduction rates. However, in the form of scenarios, it could be calculated that, given a reproduction rate of 80% for mature small cattle, when reproduction rates of large cattle were 24.7% lower than that of small cattle and the reproduction rates of medium cattle were 15.4% lower than that of small cattle, the large and medium herds became less profitable than the small herd. Smaller cattle mature faster than larger cattle which provides the opportunity for early breeding. When small cattle were bred early, at 15 months, at a calving rate of only 44.5% it was more profitable than when the same cows were bred at 24 months. When medium cattle were bred at 15 months, a calving rate of 37.0% was needed to be more profitable than when they were bred at 24 months. Even when the herd of small cattle were bred at 15 months with a reproduction rate of 100%, it could still not match the profitability of the herd of large cattle bred at 24 months given the reproduction rates of all other classes of animals were similar. When the herd of medium cattle were bred at 15 months, at a calving rate of 53.7%, it matched the profit of the herd of large cattle that were bred at 24 months, when the reproduction rates of other classes were equal. Scenarios were considered were feed intake was limited. When feed was limited to a specific amount, smaller cattle were more biologically efficient and cattle with potential for small mature sizes would grow to a larger size than cattle with potential for medium and large mature sizes. When feed was limited by a factor of the calculated energy requirements of small, medium and large cattle, large cattle were more effective. This is because large cattle use proportionately less energy for maintenance, which allows more energy to be allocated to growth, lactation and foetal production. When energy was limited to an amount per unit of metabolic weight, small cattle were more efficient than medium and larger cattle in the growth and production phases. Small, medium and large cattle were equally efficient (or inefficient) in the maintenance and lactation phases. Energy requirements of cattle in South Africa are commonly calculated using the Large Stock Unit (LSU). The LSU typically overestimates energy requirements for cattle, except in the lactation phase. When using the LSU to match small, medium or large cattle to a resource base, the LSU overestimates energy requirements of large cattle proportionately more than that of small and medium cattle. This is excluding the lactation phase, where energy requirements for all three sizes are underestimated and that of large cattle underestimated proportionately more. There are more considerations when matching cow size to managerial practices. A smaller body size is a natural adaptation to a semi-arid environment and this adaptation can be expressed in different ways. The number of animals on a resource base has implications on management practices. Having more heads of cattle on a resource base increases genetic variation of the herd, allowing for genetic progress to be made faster than in herd of fewer cattle.
Agriculture and  Animal Health
M.Sc. (Agriculture)

Understanding household farming behavior among smallholders is an essential element of land-change studies inasmuch as a considerable portion of the world is dominated by land-users of this kind. Smallholders (peasants in some literature) are especially important within the tropical forests of Mexico, and the southern Yucatán peninsular region is no exception. This region, as elsewhere in the tropics, is characterized by underdeveloped markets and the consequent partial engagement of frontier farmers as market participants. Sparse exchange opportunities resulting from remoteness, low population density, and poorly developed infrastructure constrain these farmers to maintain a strong focus on consumption production, especially in terms of staple foods. Indeed, until the late 1960s, households in the region were totally subsistence-based and had virtually no experience with the agricultural market. Today, smallholder farmers retain consumption production, though a growing proportion also produce crops for sale. While this dual position in the market and in subsistence is an increasingly prevalent feature of smallholder farmers throughout the developing world, studies of deforestation commonly ascribe to them a wholly commercial orientation by employing profit-maximizing theoretical structures as a basis for econometrically modeling their land-use decisions (e.g. Chomitz and Gray 1996; Cropper, Griffiths, and Mani 1999; Cropper, Puri, and Griffiths 2001; Nelson, Harris, and Stone 2001; Nelson and Hellerstein 1997; Panayotou and Sungsuwan 1994; Pfaff 1999). In essence, the assertion of profit-maximization rests on the assumption that agents are fully engaged in markets, from which it follows that production, being strictly a function of farm technology and exogenously given input and output prices, is entirely independent of consumption and labor supply (Barnum and Squire 1979). This chapter explores the implications of relaxing the perfect-markets assumption for the modeling of semi-subsistence and commercial land-use decisions. By introducing variables measuring the consumption side of the colonist household, evidence is presented to suggest that, consistent with mixed or hybrid production themes (e.g. Singh, Squire, and Strauss 1986; Turner and Brush 1987), farmers operating in a context of thin product and/or labor markets do not exhibit behavior corresponding to that of a commercially oriented profit-maximizing farm.

After maize, the commercial cultivation of jalapeño chili (Capsicum annuum L.; henceforth, jalapeño or chili) is the most important land use in the southern Yucatán peninsular region in terms of the numbers of farmers engaged in the practice and the total area devoted to it. Chili surpasses all other land uses in the way that it ties the region to the national economy and the way that it has altered household economies and land use. Open-backed semi-trailers and large pick-up trucks crowd the paved roads of the region between October and the end of January laden with large bags of jalapeños taken on the way to central gathering areas and, ultimately, the central wholesale market in Mexico City (Fig. 10.1). The flow of chili at this time is so large that even the casual observer would have little problem concurring with Uc Reyes’s (1999: 4.24) claims that ‘su cultivo [chile] constituye la más importante fuente de ingreso para los productores hortícolas de la entidad, además es generador de empleos para los trabajadores del campo.’ (Its cultivation constitutes the most important source of income for horticultural producers, and generates jobs for field workers.) The spread of the jalapeño describes how farmers adopt new crops, change their agriculture, and ultimately change their livelihood. It also teaches how land covers—forest, savanna, and farm field—can travel a new trajectory over a relatively short period of time, changing not only the way a region or landscape looks but the way it is viewed (Gudeman 1978; Watts and Goodman 1997). These changes began in 1975 when colonizing farmers arrived from a traditional chili-growing zone—the Chiapas/Veracruz border—and introduced its commercial cultivation. After the first year they recruited national intermediaries or middlemen (in Spanish: coyote) to purchase and transport their product to the national market in Mexico City. Observing the success of the first jalapeño pioneers, other smallholders began to adopt the practice. Today, the south-central portion of the study region is called the zonas chileras (chile-growing zones); about 85 per cent of the smallholders there cultivate chili on as much as 7,500ha, usually on small plots, about 1.5ha on average (mean = 1.42 ha).

Succeeding phases of British economic growth prompted strikingly different imperatives for expansion, for natural resource exploitation, and for the social organization of extra-European production. In the eighteenth century, sugar, African slaves, and shipping in the Atlantic world provided one major dynamic of empire. But in the nineteenth century, antipodean settlement and trade, especially that resulting from expanding settler pastoral frontiers, was responsible for some of the most dramatic social and environmental transformations. Plantations occupied relatively little space in the new social geography of world production. By contrast, commercial pastoralism, which took root most energetically in the temperate and semi-arid regions of the newly conquered world, was land-hungry but relatively light in its demands for labour. The Spanish Empire based in Mexico can be considered a forerunner. By the 1580s, within fifty years of their introduction, there were an estimated 4.5 million merino sheep in the Mexican highlands. The livestock economy, incorporating cattle as well as sheep, spread northwards through Mexico to what became California by the eighteenth century. Settler intrusions followed in the vast landmasses of southern Latin America, southern Africa, Australia, and New Zealand. Australia was one of the last-invaded of these territories, and, in respect of the issues that we are exploring, was in some senses distinctive. Unlike Canada and South Africa, there was no long, slow period of trade and interaction with the indigenous population; like the Caribbean, the Aboriginal people were quickly displaced by disease and conquest. The relative scale of the pastoral economy was greater than in any other British colony. Supply of meat and dairy products to rapidly growing ports and urban centres was one priority for livestock farmers. Cattle ranching remained a major feature of livestock production in Australia. Bullock-carts, not dissimilar to South African ox-wagons, were essential for Australian transport up to the 1870s. But for well over a century, from the 1820s to the 1950s and beyond, sheep flooded the southern lands. Although mutton became a significant export from New Zealand and South America, wool was probably the major product of these pastoral hinterlands—and a key focus of production in Australia and South Africa. The growth in antipodean sheep numbers was staggering.

Abstract As floating wind farms move from pilot projects to commercial-scale installations they will move further offshore and into deeper water. There will be a requirement for offshore substations to deliver the electricity to shore, for which floating support structures will be the preferred solution. This paper describes the challenges and development of solutions for commercial-scale HVAC and HVDC floating offshore substations. Two different floating substation concepts have been developed. Layouts for the electrical and ancillary equipment were initially developed, to enable efficient packaging and structural efficiency for the topsides. By integrating the hull and topsides, the overall mass of the structure is minimised, benefitting stability and reducing hull size. Hydrodynamic analysis of the substructures was performed and structural code checks on the hull and topsides were carried out in Sesam. Mooring designs for each structure for 250m water depth have been developed and analysed in Orcaflex. It is likely that alternating current (HVAC) export to shore will be used for shorter transmission distances and direct current (HVDC) will be used for longer transmission distances. HVDC and HVAC floating substations will have quite different hull forms. The larger topsides footprint and greater mass of the HVDC conversion equipment make a conventional semi-submersible hull form efficient when allied to a stressed-skin topsides structure. The smaller footprint, lighter weight and differing requirements for protection from the elements of the HVAC topsides make this inefficient, so a deep draught semi-submersible with a hybrid topsides is the preferred solution. It is concluded that floating substations suitable for large, commercial-scale wind farms will be the chosen solution for anything other than shallow water or close to shore.

Offshore wind energy extraction has gathered momentum around the world due to its advantages over onshore wind farms at various fronts. The floating support system with vertical axis wind turbine might prove to be feasible concept in medium to deep waters. In this context, this paper addresses an investigation of hydrodynamic analysis of three column semi-submersible with Vertical Axis Wind Turbine (VAWT) in parked condition under regular and random waves. Free decay experiments were conducted for using scale model (1:75) in a laboratory wave basin at the Department of Ocean Engineering in Indian Institute of Technology Madras, India. Computational Fluid Dynamics (CFD) simulations were used to assess damping characteristics and validated with the experiments. Numerical simulations of hydrodynamic motion response of the floater were carried out using potential flow theory based commercial software (ANSYS AQWA). The damping values obtained from experiments were used in numerical simulations to obtain motion response and Response Amplitude Operator (RAO). The motion response obtained from the study was used to verify the suitability of the system for deployment in east and west coast of India.

Large-scale commercial exploitation of wave energy is certain to require the deployment of wave energy converters (WECs) in arrays, creating ‘WEC farms’. An understanding of the hydrodynamic interactions in such arrays is essential for determining optimum layouts of WECs, as well as calculating the area of ocean that the farms will require. It is equally important to consider the potential impact of wave farms on the local and distal wave climates and coastal processes; a poor understanding of the resulting environmental impact may hamper progress, as it would make planning consents more difficult to obtain. It is therefore clear that an understanding the interactions between WECs within a farm is vital for the continued development of the wave energy industry. To support WEC farm design, a range of different numerical models have been developed, with both wave phase-resolving and wave phase-averaging models now available. Phase-resolving methods are primarily based on potential flow models and include semi-analytical techniques, boundary element methods and methods involving the mild-slope equations. Phase-averaging methods are all based around spectral wave models, with supra-grid and sub-grid wave farm models available as alternative implementations. The aims, underlying principles, strengths, weaknesses and obtained results of the main numerical methods currently used for modelling wave energy converter arrays are described in this paper, using a common framework. This allows a qualitative comparative analysis of the different methods to be performed at the end of the paper. This includes consideration of the conditions under which the models may be applied, the output of the models and the relationship between array size and computational effort. Guidance for developers is also presented on the most suitable numerical method to use for given aspects of WEC farm design. For instance, certain models are more suitable for studying near-field effects, whilst others are preferable for investigating far-field effects of the WEC farms. Furthermore, the analysis presented in this paper identifies areas in which the numerical modelling of WEC arrays is relatively weak and thus highlights those in which future developments are required.

Pulse jet mixed (PJM) process vessels are being developed for storing, blending, and chemical processing of nuclear waste slurries at the Waste Treatment and Immobilization Plant (WTP) to be built at Hanford, Washington. These waste slurries exhibit variable process feed characteristics including Newtonian to non-Newtonian rheologies over a range of solids loadings. Waste feed to the WTP from the Hanford Tank Farms will be accomplished via the Waste Feed Delivery (WFD) system which includes million-gallon underground storage double-shell tanks (DSTs) with dual-opposed jet mixer pumps. Experience using WFD type jet mixer pumps to mobilize actual Hanford waste in DSTs may be used to establish design threshold criteria of interest to pulse jet mixed process vessel operation. This paper describes a method to evaluate the pulse jet mixed vessel capability to process waste based on information obtained during mobilizing and suspending waste by the WFD system jet mixer pumps in a DST. Calculations of jet velocity and wall shear stress in a specific pulse jet mixed process vessel were performed using a commercial computational fluid dynamics (CFD) code. The CFD-modelled process vessel consists of a 4.9-m- (16-ft-) diameter tank with a 2:1 semi-elliptical head, a single, 10-cm (4-in.) downward facing 60-degree conical nozzle, and a 0.61-m (24-in.) inside diameter PJM. The PJM is located at 70% of the vessel radius with the nozzle stand-off-distance 14 cm (6 in.) above the vessel head. The CFD modeled fluid velocity and wall shear stress can be used to estimate vessel waste-processing performance by comparison to available actual WFD system process data. Test data from the operation of jet mixer pumps in the 23-m (75-ft) diameter DSTs have demonstrated mobilization, solid particles in a sediment matrix were moved from their initial location, and suspension, mobilized solid particles were moved to a higher elevation in the vessel than their initial location, of waste solids. Jet mixer pumps were used in Hanford waste tank 241-AZ-101, and at least 95% of the 0.46-m (18-in.) deep sediment, with a shear strength of 1,500 to 4,200 Pa, was mobilized. Solids with a median particle size of 43 μm, 90th percentile of 94 μm, were suspended in tank 241-AZ-101 to at least 5.5 m (216 in.) above the vessel bottom. Analytical calculations for this jet mixer pump test were used to estimate the velocities and wall shear stress that mobilized and suspended the waste. These velocities and wall shear stresses provide design threshold criteria which are metrics for system performance that can be evaluated via testing. If the fluid motion in a specific pulse jet mixed process vessel meets or exceeds the fluid motion of the demonstrated performance in the WFD system, confidence is provided that that vessel will similarly mobilize and suspend those solids if they were within the WTP. The single PJM CFD-calculated jet velocity and wall shear stress compare favorably with the design threshold criterion estimated for the tank 241-AZ-101 process data. Therefore, for both mobilization and suspension, the performance data evaluated from the WFD system testing increases confidence that the performance of the pulse jet mixed process vessels will be sufficient to process that waste even if that waste is not fully characterized.