RIASSUNTO
ABSTRACT
Offshore aquaculture structures such as kelp farm are exposed to environmental loads including winds, waves and currents. A proper design of main components and mooring system, making the structure have sufficient strength capacity withstand the ultimate, accidental and fatigue loads. Additionally, structural integrity is also important to avoid damage and economic loss. To investigate the dynamic response of a horizontal kelp farm in waves and current, experiments have been performed on a submodel of kelp farm. A horizontal textile sheet with simplified mooring was tested in a towing tank with various environmental conditions. The tests showed that the textile experience a parachute effect if the current or current and waves are above a critical sea state. This results can be used as input to the design of mooring system of kelp farm.
INTRODUCTION
The total worldwide energy consumption is the estimated 471.8 EJ in 2004, and it is expected to rise nearly 50% from 2018 to 2050 (EIA, 2019). This is one of the grand challenges facing our planet today. As of today, approximately 85% of the energy is derived from the fossil fuels, i.e. coal, oil and natural gas. Fossil fuels are non-renewable resources, limited in supply and will be depleted one day. The rising energy demand and limited non-renewable natural resources request the industry to shift the energy supply from fossil fuels to renewable energies. Renewable energies are energies generated from natural resources such as sunlight, wind, waves, tides, etc. but also from industrial or urban waste and biomass. Biomass energy, although releasing CO2, is still acknowledged as one of the most promising source of renewable energy. The technology is based on converting biomass material (plants and animal waste) into energy (i.e. heat, electricity and/or chemicals, like methane gas, butanol, etc.) (CORDIS, 2019).
Kelp grows at a high rate, and decays quite efficiently. Kelp can yield methane and sugars that can be converted to ethanol. Large open-ocean kelp farms were proposed to serve as a source of renewable energy (Christiansen, 2008). Unlike some biofuels such as corn ethanol, kelp energy avoids ‘food versus fuel’ issues and does not require freshwater irrigation. Kombu - several Pacific species of kelp, is a very common and important ingredient in east-Asian cuisines. Figure 1 illustrates a seaweed form in Fujian, China.