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Nobuo KIMURA1*, Yasuzumi FUJIMORI1, Hajime YASUI1, Hiroyuki MIZUTA1,
Tomoki ABE1, Shinji ADACHI1 and Yuki TAKAHASHI2

1Faculty of Fisheries Sciences, Hokkaido University
*3-1-1 Minato, Hakodate, Hokkaido, 041-8611, Japan, kimura@fish.hokudai.ac.jp
2Graduate School of Fisheries Sciences, Hokkaido University

ABSTRACT

This study described the development of elemental techniques about the bio-farming system for valuable northern type mega benthos using natural energy. Recently, there are strong needs for the construction of eco-friendly aquaculture and sustainable production system on the fishery sector. To construct the farming system without depending on fossil fuel-derived energies such as electricity, we have studied self-reliant bio-farming system using renewable energy; wind power, solar power, etc. Considering that the farming system on the land, water lifting, regulating water temperature and circulation use lots of electricity, we took the alternative route. To promote efficient construction of the bio-farming system, some great elemental technologies were studied as follows: 1. Water lifting system using wind and solar energy, 2. Anti-freezing system by use of geo-thermal energy, 3. Regulating water temperature by use of groundwater, and 4. Order-made farming by natural energy.

Further, we explained the other plan related to bio-farming proceeding in Hakodate, Hokkaido using current energy: 5. Marine energy utilization for comprehensive bio-farming system based on geographical conditions.

Keywords: natural energy, bio-farming system, eco-friendly aquaculture, CFD

INTRODUCTION

In Hakodate, Hokkaido, Japan, a project called "Hakodate Marine Bio Industrial Cluster" is being conducted from 2009 with financial support from the Ministry of Education, Culture, Sports, Science and Technology, Japan, in collaboration with the academia, industries, and local government. The project shown in Fig. 1 is a conceptual diagram of "the intellectual cluster initiation business (The global base upbringing type)". On the basic concept which considers the sea as one production system, the project consists of four themes: (1) measurement and prediction of marine environment, (2) sustainable production of mega-benthos, (3) detection of highly functional materials and effective utilization and (4) brand creation to open new market. Each theme is comprehensively connected and we take charge of the 2nd theme entitled "Autonomous `green bio-farming' of the northern mega-benthos containing high value added products".

Further, the study is divided into two main subjects: (1) lifecycle manipulation of northern mega-benthos and the creation of highly functional seedlings, and (2) establishment of sea-based green cultivation factories. To construct the bio-farming system without depending on fossil fuel-derived energies, we have studied independent type of farming system by the efficient use of natural energy. An image of the bio-farming system is shown in Fig. 2. We try to develop these elements of the farming system supplied by natural energy (Kimura, 2012). A simulation technology using by CFD (Computational fluid dynamics) is indispensable for the development of this farming system.

Development of elemental technology of the bio-farming system

To construct the self-reliant bio-farming system by employing natural energy, we have studied some important elemental technologies as follows.

Water lifting system using wind and solar energy

We focused on Savonius rotor and multiple-bladed rotor. An image of the water lifting system based on the Savonius rotor is shown in Fig. 3. Although there are lots of wind rotors, the main reason that we chose this type of rotor are simple construction, easy maintenanceand big torque in the condition with weak wind speed. Further, it is easy to repair even if the wind rotor will break down. As the rotor utilizes drag force of wind power, there is constructional disadvantage. Power efficiency is lower compared to the other rotors that use lift force, and tip speed ratio is restricted. However, it is suitable for sea water lifting system (of the bio-farming system) considering the operational stability of the mega-benthos farming system.

To construct an optimal design of the wind rotor, we carried out lots of simulations using computational fluid dynamics (CFD) analysis, and the design of the wind rotor that generated the largest torque by the wind was determined numerically (Yamashita et al., 2010). We carried out CFD analyses by the use of the fluid analysis software ANSYS CFX (CYBERNET Inc.). This numerical analysis solved Reynolds Averaged Navier-Stokes (RANS) equation using Finite Volume Method (FVM). In the calculation, we used tetrahedral mesh. In addition, a sliding mesh model was used for the interface between rotating and static domains. The Shear Stress Transport (SST) model is employed as the turbulent flow model. As an example, calculation domain and boundary condition of the simulation is shown in Fig. 4, and streamline around the wind rotor numerically estimated by CFD is shown in Fig. 5.

The model of water lifting system was constructed at Nanaehama, Hokkaido University as shown in Fig. 6 to conduct verification. As shown in Fig. 3, sea water is directly pumping up from sea surface below about 3.0 m to water storage tank, and naturally pours sea water into the farming tank.

We adopted a piston pump for water lifting. From a result of performance test for water lifting pump, we tested the relationship between driving force and resistance pump, and found the system which was designed to start water lifting over wind speed of 3.0 m/s. Further, to improve the dynamic lifting characteristics, we developed a new type of vertical axis rotor for water lifting (Takahashi et al., 2011). The rotor unit is composed of the outer and inner rotors; the gyromill rotor with three wings outside and the Savonius rotor inside. We also optimized motive performance of the hybrid-type rotor by using CFD analysis. Streamline around the wind rotor numerically estimated by CFD is shown in Fig. 7, and view of half size model of the wind rotor under verification test is shown in Fig. 8.

Considering further efficiency, we changed water lifting system from direct lifting to storage system by the use of electric generator. Multipolar generator with pole numbers 32 (SKY-HR250, Output 0.3kW/300rpm) is adopted.

As natural environment is unstable and electrical capacity generated by wind power is generally restricted, we have to make pouring water and circulation in farming tank more efficient. To aim smooth circulation of sea water stored in tank, we estimate the flow in tank at various conditions of pouring water, drain, and aeration. On the numerical simulation, we utilized the fluid analysis software ANSYS Fluent 14.5 (CYBERNET Inc.). Schematic of the farming tank for sturgeon is shown in Fig. 9. The tank has a diameter of 3.0m, hose pipe and drainpipe have diameter of 0.04m, and each volume of flow is 50L/min. Speed of aeration is 0.5m/s. Depth of water in the tank is about 1.0m. An example of the simulation of farming tank flow with aeration is shown in Fig. 10.

Anti-freezing system by use of geo-thermal

Hakodate area is located in fairy north so we have to take countermeasures for anti-freezing of the water lifting system. Similar to temperature regulation of water, anti-freezing of water lifting system in winter season requires lots of electricity.

Sea water is generally frozen at -1.8 degrees Celsius. Once sea water in the suction pipe or diaphram pump in the pumping room is frozen, there is serious damage for the water lifting system. To avoid such condition, we have to keep temperature in the pumping room over frozen point of sea water. Then we focus on geo-thermal utilization. By the use of heat transfer pipe, we try to keep temperature in the pump room and not to freeze sea water. An image of the anti-freezing system utilized heat transfer pipe is shown in Fig. 11. A view of anti-freezing system used heat transfer pipe equipped for the multiple-bladed rotor is shown in Fig. 12. The heat transfer pipe used in the verification tests was developed by a local company in Hakodate. The heat transfer pipe has the characteristics of operating fluid adapting for external temperature. To clarify the effect of the heat transfer pipe, one heat transfer pipe was installed in the anti-freezing system.

A change in air and underground temperature were monitored from February 28 to March 13, 2012. As shown in Fig. 13, temperature at 2.0m underground is fairly steady with about 3oC. And temperature at radiation part of the heat pipe is higher 4-5 degrees than outer temperature at cold morning.

As a result of the monitoring, the anti-freezing system was operating appropriately, however thermal capacity of a heat transfer pipe was insufficient to keep proper temperature in the pumping room. Thus, it is indicated that the anti-freezing system gives beneficial effect to the northern farming system for according to install a number of heat transfer pipes.

Regulating water temperature by use of groundwater

Regulation of water temperature is very important for bio-farming, since the range of suitable water temperature of mega-benthos is ordinarily narrow. The regulation equipment requires lots of electric power, because bio-farming uses a large volume of water, and there is large difference in temperature between summer and winter in Hokkaido, Japan. To regulate water temperature in farming tank by use ofnatural energy, we paid attention to utilization of groundwater. Temperature of groundwater is stable in about 13-14oC throughout the year in Hakodate area, and it is suitable for farming of northern mega-benthos. An image of farming tank regulated water temperature by use of groundwater is shown in Fig. 14. To make efficient use of groundwater, we have to take measures for changing of water temperature under the transfer process to farming tank. Therefore, a model of farming tank with equipment to regulate water temperature by use of groundwater was made. Transfer pipes above the ground 14.3m in length used vacuum insulating structure, and the pipes in the other part 16.5m in length were buried. An image of the model farming tank regulated water temperature by use of groundwater is shown in Fig. 15. View of simple structure of SUS radiator to regulate water temperature is shown in Fig. 16.

To evaluate the effect of the regulation, we carried out the monitoring about water temperature. As an example, in the winter season, the air temperature was about -6.0oC in the morning December 10, 2011. However temperature in groundwater tank is 13.3oC, and water temperature in the transfer pipe is same 13.3oC. In addition, water temperature of farming tank keeps about 12.2oC. Therefore the radiator efficiently converts heat of groundwater to water during the farming tank.

Another example during the summer season, the air temperature was about 27.6oC in the afternoon of August 12, 2013. On the other hand, temperature in groundwater tank is 14.0oC, and water temperature in the pipe is 14.6oC. Furthermore, water temperature of farming tank is kept at about 18.0oC, the radiator also converts efficiently heat of groundwater to water in farming tank.

As a result, regulation of water temperature by groundwater is very efficient for the bio-farming, especially in the region with large temperature variance. Further, as there is no change of water temperature under the transfer process from the groundwater tank to farming tank, vacuum insulating structure pipe is useful for the improvement of regulation of water temperature.

Order-made farming by natural energy

It is well known that contents including seaweed like viscous polysaccharides and/or fucoidan have strong pharmacological effect. There are lots of unused mega-benthos containing high value-added products in the surrounding sea area of Hokkaido, Japan. Detection and lifecycle manipulation of mega-benthos with highly functional materials are important for efficient utilization of unused mega-benthos.

Fig. 17 shows the content of fucoidan in seaweeds. The detail of growing environment of the northern mega-benthos has been studied by the laboratory experiment. As an example, a frame format and succession of development stage of Gagome ( Kjiellmaniella crassifolia Miyabe ) for change of growing environment is shown in Fig. 18.

As for the content of fucoidan derived from seaweeds, Gagome contains lots of fucoidan compared with other seaweeds, and especially bio farming (BF)-Gagome contains two times as much fucoidan as the natural Gagome. Note that BF-Gagome indicates the farmed Gagome by regulated growing environment, and optimum growing condition was experimentally estimated by culture in the laboratory.

According to control of growing environment like illumination, water temparature, flow speed of seawater and nutrients concentration in the farming tank, we have studied about the efficent farming of highly functional seedlings using natural energy. Fig. 19 shows a model of `order-made farming system', and Fig. 20 shows the control box and battery equipment of the farming system. The farming environment of four farming tanks (42L×4) are all controlled by using electricity generated by solar panels (1.05kW×1, 2.10kW×1) and a wind rotor (0.60kW). As shown in Fig. 19, illumination of the farming tanks is different by use of LED (Light Emitting Diode) light (Hamamatsu Photonics K.K); white, blue, green and white from right side. From the figure, difference of growing is clear by different illumination.

Using seedlings grown up to the stage D in Fig. 18 farmed with proper growing environment, large scale cultivation of BF-Gagome is possible to do in the coastal area in Hakodate.

Marine energy utilization for comprehensive bio-farming system based on geographical conditions

Finally, we explain the other plan proceeding in Hakodate, Hokkaido using current energy. This project is the next step in establishing the abovementioned bio-farming system. As a background, the Japanese government is promoting a development and utilization of marine energy, especially after the devastating earthquake occurred in eastern Japan in March, 2011. The main aim is to utilize marine energy as a commercial electric generation to diversify energy source. Considering commercial use of marine energy, growing in size of equipment is unavoidable. Then, we focus on current energy for bio-farming of the mega-benthos. The concept is `current energy utilization for sustainability of valuable fisheries based on geographical conditions'.

The Tsugaru Channel located in southern Hokkaido is an international strait and strong warm current is flowing from west to east. The sea area is a profitable fishing ground, and traffic of small fishing boats and merchant vessels is busy. Then, utilizable sea area of tidal current generation is restricted because of the relationship between fishery zone, traffic of vessels and geographical condition.

To utilize such a restricted fishery zone, we consider the location of artificial reefs. By appropriately setting the artificial reef in condition of restricted water depth, increased speed effect and rectification effect of tidal current can be obtained. An example of simulation of the current around the artificial reef located on sea bed is shown in Fig. 21. On the assumption that the equipment is located at the coastal areaoff Hakodate, we decided to calculate conditions as follows; calculation domain ; 150.0m in length×100.0m in width×25.0m in height, artificial reef ; 3.0m×40.0m×3.0m, current speed; 1.03m/s ( 2.0knots ), water depth; 25.0m. As shown in Fig. 21, current speed after the artificial reef increased about 25% compared with natural current, and there is also sea area with slight current over sea bed. Then, using the artificial reef, we can equip effective tidal current power generation and artificial fish reef at the same time. Further, we can take advantage of electric power to the bio-farming system. An image of a comprehensive self-reliant bio-farming system employing natural energy is shown in Fig. 22. Constructing the self-reliant bio-farming system close to the tidal power generating facility, the cost related to construction of infrastructure can be greatly reduced. Moreover, making use of tidal current power generation as a total farming system employed natural energy, we could produce a comprehensive bio-farming system of the northern mega-benthos based on regional advantage.

CONCLUSION

Based on the concept of eco-friendly aquaculture and sustainable production system on fishery, we have studied important elemental technologies to construct the self-reliant bio-farming system by employing natural energy. Considering safety and maintenance of the farming system by utilizing unstable natural energy, we preferentially used simple and steady technology rather than advanced technology. As a result of verification tests, we could confirm efficiency of the fundamental technologies related to water lifting, anti-freezing and regulating water temperature system by natural energy. An image of comprehensive self-reliant bio-farming system is shown in Fig. 23. This system is really eco-friendly farming system aiming at sustainable production.

REFERENCES

  • Yamashita, J., Fujimori, Y., Takahashi, Y., Yasui, H., and Kimura, N., 2010. Development of a wind pump system with Savonius Rotor using Computing Aided Engineering technique. Mathematical and Physical Fisheries Science, 8, 42-53.
  • Takahashi, Y., Fujimori, Y., Yasuma, H., Yasui, H., and Kimura, N., 2011. Motive performance of a new type of vertical axis rotor estimated by CFD analysis. Mathematical and Physical Fisheries Science, 9, 75-84.
  • Kimura, N., 2012. Activities of Fisheries Informatics at Fac. of Fisheries Sciences in Hokkaido Univ.: Utilization of CFD technique, Proceedings of 4th Joint Workshop Hokkaido University _ Korea Maritime University, 93-98.


Index of Images

  • Fig. 1 Hakodate Marine Bio Industrial Cluster.

    Fig. 1 Hakodate Marine Bio Industrial Cluster.

  • Fig. 2 An image of bio-farming system using natural energy.

    Fig. 2 An image of bio-farming system using natural energy.

  • Fig. 3 Water lifting system by wind power.

    Fig. 3 Water lifting system by wind power.

  • Fig. 4 Calculation domain in CFD, mesh: tetrahedral, element num.: 500,000, turbulent: SST model.

    Fig. 4 Calculation domain in CFD, mesh: tetrahedral, element num.: 500,000, turbulent: SST model.

  • Fig. 5 Streamline around the bach type Savonius rotor.

    Fig. 5 Streamline around the bach type Savonius rotor.

  • Fig. 6 View of the water lifting system at Nanaehama, Hokkaido University.

    Fig. 6 View of the water lifting system at Nanaehama, Hokkaido University.

  • Fig. 7 Streamline of the hybrid-type wind rotor.

    Fig. 7 Streamline of the hybrid-type wind rotor.

  • Fig. 8 View of the model of hybrid-type wind rotor.

    Fig. 8 View of the model of hybrid-type wind rotor.

  • Fig. 9 Schematic of the farming tank.

    Fig. 9 Schematic of the farming tank.

  • Fig. 10 An example of simulation of farming tank flow.

    Fig. 10 An example of simulation of farming tank flow.

  • Fig. 12 View of anti-freezing system used heat transfer pipe.

    Fig. 12 View of anti-freezing system used heat transfer pipe.

  • Fig. 13 Monitoring of temperature in pumping room and 2m underground.

    Fig. 13 Monitoring of temperature in pumping room and 2m underground.

  • Fig. 14 Farming tank regulated water temperature by use of groundwater.

    Fig. 14 Farming tank regulated water temperature by use of groundwater.

  • Fig. 15 View of farming tank regulated water temperature.

    Fig. 15 View of farming tank regulated water temperature.

  • Fig. 16 View of radiator for regulation of water temperature.

    Fig. 16 View of radiator for regulation of water temperature.

  • Fig. 17 Content of fucoidan in dry seaweeds.

    Fig. 17 Content of fucoidan in dry seaweeds.

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