PRE2015 4 Groep5

Group members

Aniceta, N.M.F (0876672)
Boelsums, N.M (0964376)
Brandts, A (0895917)
Haenen, S.R.R (0889428)
Kuijpers, J.J.L (0838617)

Introduction

Abstract

Problem statement

The world needs to produce at least 50% more food to feed 9 billion people by 2050. But climate change could cut crop yields by more than 25%.^[1] With this in mind we need to look for novel solutions to the problem of insufficient food production. This solution will need to take the interests of users, society, and enterprise into account. Moreover, this solution needs to surpass the state of the art by employing cutting-edge technology.

Motivation

Nutrition is vital to sustaining life, and food security is important for political stability and human welfare. We want to address the problem of food availability due to its relevance: continuing population and consumption growth will mean that the global demand for food will increase for at least another 40 years.^[2]

Agriculture is an integral part of the European economy and society. It provides the basis for food, feed and non-food products to meet the demands of consumers and a wide range of industries.^[3] By designing a solution to the agricultural challenge we will need to take into account the needs of users: like consumers of food, society: the ecological impacts of our solution, and enterprise: the solution needs to be competitive in order to gain an economical advantage.

The agricultural industry is ever advancing, not only is the biological aspect of farming being researched, there are also improvements in automation,^[4] and we want to explore the automation of this industry. We want to develop a solution that allows for automation of food production beyond the state of the art, moreover the solution needs to be scalable.

Mariculture

Representation of a sea farm

Mariculture is a specialized branch of aquaculture involving the cultivation of marine organisms for food and other products in the open ocean, an enclosed section of the ocean, or in tanks, ponds or raceways which are filled with seawater. An example of the latter is the farming of marine fish, including finfish and shellfish like prawns, or oysters and seaweed in saltwater ponds.^[5]

In this section we will explore mariculture, and explain why we chose it as a solution to the problem previously stated. Mariculture encompasses a wide range of organisms, from the cultivation of water-based plants to the breeding of aquatic animals. For this project we will focus on the cultivation of aquatic plants, and in particular types of seaweed.

Commonly cultivated seaweed species

The total seaweed production features a lot of brown kelps. These weeds grow in cold water zones, they are long and have a leathery structure. They must be harvested before the water temperature rises to 21 degrees, otherwise the kelps will rot. Kombu (Laminaria Japonica) is used a lot in Japanese recipies for soups, as dried snacks, or in salads. Kombu is a dietary fiber and contains high levels of iodine. In China, 50% of the Laminaria production is meant for industrial purposes for its iodine, algin and mannitol. Due to this, laminaria are considered as one of the best renewable resources and it makes up for a major part of the maricultural sector. Japan has made effort to increase the production but due to its labour intensitive nature, the market is not expected to expand notably.^[6] Wakame (Undaria) is the type of kelp you will find in your misosoup. With a subtle sweet flavour and satin-like texture it is most suitable for human consumption. The weed is a rich source of omega-3 and helps burn fatty tissue. However, it is also in the top 100 of worst invasive species in cold waters, which is partly caused by aquaculture.^[7]

Gelidium amansii and Pterocladia are valuable red algae that can be found at shallow coasts. They can be used in salads and to make agar, a jelly-like substance that can be used for microbiological research and various industrial purposes.^[8] They have been cultured in Korea since the last century, but always on a small scale. There have been various attempts to farm the algae at sea, but the slow growth rate and required non-contaminated waters made it unattractive for commercial cultivation.^[9]

Nori or Zicai (Porphyra) are most famous for composing the sushi wraps. The red algae grow in cold and shallow waters in the intertidal zone. After growing in the sea for 50 days, the weeds can be harvested every 10-15 days. The Nori market is stable, the demand is not expected to grow or shrink in the coming years. In Japan, the annual production is valued at 1 billion US dollars.^[10]

Environment

Dead zones

Dead zones in oceans around the world.

Ocean dead zones are areas with low oxygen levels and hardly any marine life. These areas are caused by agriculture fertilizers that increase the level of nitrogen and phosphorus, also known as eutriphication. The result is a rapid increase in phytoplankton, because they are 'build' from phosphorus and nitrogen. These algal blooms cause deadzones. The number of deadzones is increasing. As a result, the fertility of the marine life drops dramatically, and in more extreme cases, fish fall unconcious and then suffocate. Slow moving creatures on the seafloor are unable to escape. Seaweed is capable of uptaking both nitrogen and phosphorus and replacing it with oxygen. For this reason seaweed is also cultivated around fishfarms. Seaweed would be a cheap although perhaps slow solution in the reviving of dead zones.^[11]

Climate

Seaweed can assimilate a lot of CO₂ about 30 to 60 times the rate of land plants. But this will not solve the CO₂-problem, because the CO₂ will be released when the seaweed will be consumed. Seaweed only contributes indirectly to a better milieu. Because of the seaweed farms less forests will disappear for farmlands. This forest contributes to a net CO₂ storage. Seaweed can also be used for the production of biomethane and electricity. So the unsustainable fuels can be replaced, this results in less CO₂ pollution.

Locations

To determine the best location for a sea-farm we have to take into account several aspects. The temperature of the seawater should be the right temperature for seaweed. For example the best temperature for growing Eucheuma is 20-25 °Celsius, but there are also species that can grow in water of 10 °Celsius. So seaweed can grow in almost every ocean. The depth of the sea does not matter for the seaweed of farm, because we will only use species that grow from the surface downwards. But for the farm itself the depth does matter. Anchoring the farm is easier in a shallow area in the ocean. Commonly these areas are near the coast, an advantage of sea-farms which are near the costs is that the transport from farm to the secondary users is cheaper. Also building and maintaining the farm is easier if it is closer to the mainland. The dead zones are also located near the seashore, so the dead zones are an extra motivation of locating the sea-farms there. A disadvantage are the shipping routes that are located in these areas. Thankfully, these routes are taken by most commercial ships. This leaves open spots near the coast where there are no passing ships and where the seaweedfarms could be located. Important shipping routes at the Dutch coast.^[12] With the sea levels rising due to climate change, and the seafarm's habit breaking waves, it would be beneficial to locate the farm nearby a shore that is threatened by rising sea levels.

Nutrition

From a nutritional standpoint, the main properties of seaweeds that distinguish them from higher plants are their high mineral and dietary fibre contents. The high iron and magnesium contents are of particular nutritional interest due to their metabolic or functional properties. In comparison with other sources of fibres, seaweeds contain a high proportion of soluble fibres, which exhibit original fermentation patterns in the large intestine. Red seaweeds have a high protein content, comparable to that of high-protein vegetables. Available data suggest that they have a unique amino acid pattern, complementary to that of most terrestrial vegetables.^[13] Edible brown and red seaweeds could be used as a food supplement to help meet the recommended daily adult intakes of some macrominerals and trace elements.^[14]

There might be some hesitance in the use of seaweed for human nutrition, but the seaweeds which are used as biological filters and food material for farmed animals could easily be included in the human food value chain by this route.^[15]^[16]

As seaweed accumulates important substances from the surrounding water, it does not only accumulate the desired minerals and trace metals but it also accumulates undesirable metals and heavy metals from the surrounding environment.^[17] This can be exploited, and seaweed can be used as a biofilter, but if the goal is nutrition it is important to not let seaweed grow in polluted water.

Seaweeds are known for their richness in polysaccharides, minerals and certain vitamins,^[18] but they also contain bioactive substances like polysaccharides, proteins, lipids and polyphenols, with antibacterial, antiviral and anti-fungal properties, as well as many others.^[19] This gives seaweed great potential as a supplement in functional food or for the extraction of compounds. Proteins, peptides and amino acids from seaweed have shown positive bioactive effects in the treatment of diabetes and cancer, and the prevention of vascular diseases. The amino acid profile of some seaweed species is similar to that of animal foods. Extracts of valuable amino acids for feed supplement could be of potential because essential amino acids cannot be replaced by other compounds.^[17]

State of the art

Currently, mariculture is not a high-tech affair. Most of mariculture involves manual labor, and in part mariculture is practiced in a non-industrial setting, however we want to focus on industrial mariculture. In shallow-water mariculture the lines to where the seaweed is attached are handled manually, and the shallow waters are traversed by foot. For mariculture out on open waters ships are used to get to the farms. For mariculture further off from the shore farmers might make use of cranes to pick up lines and gather crops, this however still involves direct human labor, and sometimes physical labor to pull in lines. For aquaculture — 'indoor' mariculture, in a controlled pond or other body of water — there exist technologies like smart sensors and smart filtration systems. These technologies however are not applicable to offshore mariculture, as it is a rather different environment from the controlled ponds for which these technologies are manufactured.

Our solution to mariculture goes beyond the state of the art, and we envision it has benefits for user, society and enterprise compared to current technologies.

Benefits and drawbacks

Benefits

Income, employment and foreign exchange (import/export).
Pond-farms can make use of otherwise infertile and underutilized land.
Large-scale farms influence coastal water movement, causing enhanced sedimentation and better protection of the coastal areas from erosion.
Introduction of seaweed culture rafts, ropes, anchors, etc. can increase the surface area of substrate, which may enhance production of other marine organisms in a similar way to what artificial reefs have been shown to do.
Seaweed culture mostly relies on a natural nutrient supply.
Seaweed farms offer shelter for other animals, increasing the biodiversity.
The area below seaweed farms can be used for invertebrate farming such as sea cucumbers.
Seaweed farms may be placed further offshore to better utilize offshore resources.
Seaweed farms are mostly submerged, except for some buoys, so they are not visually distracting.

Drawbacks

Conflicts with other users of the coastal zone.
Concerns over potential environmental impacts.
Large surface area required for viable seaweed culture.
Site preparation may involve removal of native animals, plants and destroying the natural environment (e.g. removing rocks) which may damage the local ecosystem.
Routine management can result in damage through trampling and accidental damage of the local ecosystem.
Physical shading of an area can occur. The effects of this have not been well-studied.
Intensive farming may require additional fertilization. This has yet unknown effects on the local ecological system.
Large farms and intensive farming may cause deceases to spread more rapidly, causing production loss and other negative effects for the ecology.
Intensive farming may reduce the nutrient levels of coastal waters, making it harder for other organisms to survive.

Types of farms

Anchored

Anchored farms are static to a certain extent, seeing as they only slightly deviate from their positions due to ocean waves and currents. These anchored farms can provide protection to coastal areas were they to be anchored close to the shore. This wave-breaking property is due to the seaweed absorbing part of the energy carried by ocean waves. If the farms were to be anchored furthered away from the shore one needs to take into account the depth of the seafloor. Moreover, anchoring could potentially disturb life on the seafloor. Anchored farms are universally employed in the maricultural industry.

Drifting

Drifting farms would constitute a more advanced technology. Free-drifting farms are a liability and potentially a hazard of not attended to. Despite the dangers drifting farms could still be used, and might have benefits over anchored farms. Drifting farms can move with the ocean currents, or make use of wind power to passively drift. However, a freely drifting farm would not have any benefit over an anchored one. The main focus of a drifting farm would be to make it drift smartly — that means that it should be aware of its environment and have actuators to be able to actively move. A smartly drifting farm would be able to autonomously traverse the ocean in order to find optimal spots, for instance a nutrient-rich patch of the ocean, or a location with optimal sunlight.

The drifting farm is a design challenge that we will not take on in our design, however future farms might make use of migratory techniques.

Tasks to be carried out on farms

Primary tasks

Harvesting — this is the main focus of a farm, to bring in the crop
Seeding — after harvesting new plants need to be placed
Cleaning — plants need to be cleaned ever once in a while in order to remove barnacles and pathogens

Secondary tasks

Checking the quality of the plants — regularly checking the quality of the plants will let you predict the quality and quantity of the total harvest
Removing corrupt plants — bad plants need to be removed, especially the sick plants before other plants get infected

Stakeholders

User

Seaweed farmers

Seaweed farmers are the primary users of this technology. Their main interest is related to livelihood. The farmers will use this technology to make a living, and produce seaweed to sell. The technology allows them to produce more seaweed than ever before due to its efficiency. Moreover there will be health benefits for the farmers, as the strenuous physical labor will be performed by machines. Due to the scalability of this technology farmers will be able to grow their farms, and with economies of scale keep increasing their profits. Not every seaweed farmer is the same, however, and farmers with a lot of capital available will be able to invest in the farms and outcompete their competitors with less capital. This inequality divides the group of seaweed farmers in two, and this might give rise to a conflict of interest. However, farmers with less capital available will still be able to sell their seaweed as being more humane, which might encourage certain groups of customers. For the seaweed farmers in general we foresee a net positive.

Food industry

Due to an increased production of seaweed there will be an increase of available seaweed protein and nutrients from seaweed. As outlined in the section on nutrition seaweed contains a lot of nutritional substances. Having more of these substances available from a sustainable source like seaweed farming will allow the food industry to source from a more diverse pool of nutrients. We especially foresee seaweed-based nutrients be cheap due to the economies of scale. The seaweed can be sold directly, or it can be processed. Seaweed can also be used as animal feed.

Consumers

Consumers will benefit from this technology for several reasons. Firstly the cost reduction will aid consumers as they will have more left to spend. Protein from animals requires more resources, and hence is more expensive than plant-based protein.^[20] Secondly plant-based protein has health benefits compared to animal protein.^[21] This health benefit does not just depend on having consumers shifting their diet, but seaweed can act as a protein source in processed foods. Finally there is the introduction of seaweed protein and nutrients in general, as outlined in the section on nutrition seaweed contains a lot of nutritional substances. Having more of these substances available from a sustainable source like seaweed farming will give consumers more choice and empower them in following a diet of their choice.

Seafarers

Seafarers will have to navigate around the seaweed farms, and recreational boating will not be possible next to seaweed farms. The positions of the seaweed farms should be chosen such that they do not interfere with commercial shipping routes. If the positioning of the farms isn't handled correctly seafarers might be negatively effected by this technology.

Inhabitants of coastal regions

This technology would introduce more seaweed farms. These farms can provide protection to coastal areas were they to be anchored close to the shore. The seaweed absorbing part of the energy carried by ocean waves gives it a wave-breaking property. This would mean that inhabitants of coastal regions will be offered more protection than just using levees without these farms. So these inhabitants could indirectly profit from this technology.

Scientists

The farms will be equipped with an assortment of sensors. The sensors will be used to assess the quality of the water in order to make meaningful statements about the seaweed on the farm. The information gathered by the sensors can be used for more purposes than just those in the direct interest of the farm. The data gathered can be shared with scientists, or could be fully openly shared. These datasets can be valuable for science and oceanographic research.

Society

Environment

As outlined in the section on environment above, this technology benefits the environment. Currently the production of food for animals that are raised for human consumption is very costly on the environment.^[20] These environmental benefits have a positive impact on society in general. However, due to the robots on the farm wildlife might be disturbed,^[22] this introduces a trade-off, the farm has to forfeit some efficiency or speed in order to not harm the environment. If the technology is implemented without regard to the environment it could turn out to be a USE nightmare.

Government

Partly due to the environmental benefits, and the added economical value the government might be interested in this technology. The development and deployment of this technology could be supported by governmental agencies in the form of grants and subsidies. Supporting this technology could reinvigorate the dead zones as described in the applicable section on dead zones. Combating these dead zones could benefit the ecology and benefit the conventional fishing industry. The environmental benefits could also spur tourism owing to cleaner and safer oceans. This technology could (indirectly) positively impact a nation's (or region's) GDP, so governments will have interest in supporting this technology.

Enterprise

Seaweed farm owners

Seaweed farm owners are one of the largest stakeholders as enterprise entities. This technology will enable seaweed farm owners to scale their business and improve profits. The automated nature of the technology allows for increased productivity and enhanced crop security, due to 24/7 availability of the robots and constant maintenance. There is a possibility of an 'inconsiderate' implementation of the seaweed farms, in this scenario a business would optimize for profit only and would not take other stakeholders into account, this mostly impacts the environment (as outlined in the Society section). While marine life would be disturbed, pollution wouldn't be much of a problem, because polluting the direct environment of the farm would negatively impact the quality of the seaweed.

Food industry

As outlined in the user subsection, the food industry will be able to source more diverse nutritional substances. This increase is supply will be a benefit for the food industry.

Culinary industry

The technology would lead to seaweed being more ubiquitously available. This, aside from being used for processed foods, might lead to a shift in dietary preferences. Even if the dietary shift does not take place, access to cheaper seaweed might be an incentive for the culinary industry to innovate. There are many dishes that include seaweed, and there are many left to be discovered. This is not so much a direct benefit, nor is it a contrapositive. This poses a possible challenge for gastronomical innovation.

Subsidized environmental efforts

With the evident environmental benefits of the technology in mind there might be subsidies available for those who implement it. This might be an incentive that could kick-start the automated seaweed industry. These subsidies could give enterprises an edge compared to conventional agriculture or otherwise low-tech aquaculture.

Ethical analysis

Utilitarian analysis

	Using the technology	Using the technology irresponsibly	Not using the technology
Environment and wildlife	+ +	– –	○
Farm owners	+	+ +	○
Manual labor jobs (non-technical)	–	–	+
Maintenance jobs (technical)	+	+	–
Commercial shipping & casual boating	○	–	○
Oceanography	+	○	○
Food industry	+	+	○
Consumers	+	+	○
Inhabitants of coastal areas	+	○	–
Total:	7+	1+	1–

The aspects are rated from very positive (+ +) to very negative (– –).

From the table we can see that using the technology has the most utility. This is because of its benefits described in the stakeholders section. Using the technology irresponsible — without regard for the environment or other stakeholders — has a bit of positive utility, but this mostly stems from the benefit the farm owner has. Not using the technology has some negative utility, this sis surprising since we would expect the utility to be neutral. The negative utility comes from the inhabitants of coastal regions being unprotected and thus being more susceptible to danger.

Maritime robotics

In this section we will give an overview of maritime robots and their relevant technologies.

Types of robots

Maritime robots can be classified into several categories:

Buoy: this robot floats at one spot on the surface. It is mainly used for acquiring data by using sensors attach to the buoy. It can function as an energy generator by using solar panels, also, it can be used as a relay station for communications by attaching a satellite dish.
Traveler: this robot can actively move across the water's surface by using some way of propulsion. It can be similar to the sensor buoy in its functions.
Underwater Airplane: similar to an airplane, only instead of like flying through the air it moves through water according to the same principles of fluid dynamics. Can be tricky to maneuver because it cannot stop as quickly as other types of robots. This is one of the fastest underwater robots.
Diving Box: this robot can move in any direction and float in midwater. However, it is very energy inefficient. Moves up and down based on the principles of buoyancy.
Etcetera: robots that don't belong to the other categories.

Locomotion

A passive ocean drifter and a high-speed jet-propelled vessel.

There are several ways for maritime robots to traverse the oceans:

Jet propulsion — water is taken in and propelled out at high speed, using a directed nozzle makes this very maneuverable.
Ocean current — passively drifting along the ocean current.
Propeller — a classic ship's screw to propel forwards and backwards.
Undulation — moving the body like a fish does.
Wind — using the power of the wind to sail.

Some types of propulsion are passive, such as using the ocean currents and moving by wind power; this is very energy efficient, however. For more speed one would use jet propulsion or propellers.

Sensing

Sonar can be used for bathymetry, measuring the depth of the ocean floor.

There are many types of sensors and things to sense.

Acoustic Doppler current profiler — measures the speed and direction of ocean currents using the principle of “Doppler shift”.
Camera — for visual data, has a limited range.
Conductivity — together with temperature and depth information, a good estimate of the salinity may be determined.
GPS — find the position, only works above the surface of the water.
Hydrophone — listen for sounds in the water.
Oxygen — determine the oxygen levels of the water.
Pressure — determine the depth the robot is at.
Semipermeable membrane density — a passive sampling device used to monitor trace levels of organic contaminants. When placed in an aquatic environment, SPMDs accumulate hydrophobic organic compounds, such as polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), and organochlorine pesticides from the surrounding waters.
Sonar — is used to find and identify objects in water. It is also used to determine water depth (bathymetry. May disturb marine life.
Temperature — determine the temperature of the water.
pH — determine the acidity of the water.

Some of these things are very important for positioning, such as GPS for above-water devices, and sonar for longer range object detection. Other types of sensors could be implemented to gather data on the quality of the water — for instance the pH levels of the water could tell whether the seaweed is growing in a favorable environment. The other sensors can also be used for gathering general long-term data for use in science.

Communication

To allow an offshore farm to communicate with a land-based control station (or transmit data between the users/administrators and the farm) there are numerous conventional methods to employ. For instance satellite communication can be used to transmit and receive data. So for our sea-based machines to communicate they would need to have a part that is not submerged, or they would be required to surface to transmit data. We want to employ machines that can communicate while submerged, therefore we need to find a way to transmit data underwater.

There are two ways to transmit signals under water, using wired technology or wireless technology. A wired solution would require an umbilical cord or tether between two communicating nodes or hosts. This wired solution is quite reliable, and obvious if the device that needs to send or receive data needs to be tethered for other reasons such as the supply of power or for anchoring purposes. However, this wired solution has its drawbacks if a device does not need to be tethered — a tether could hinder its freedom of movement — or if the distance to communicate over is quite large. For our project, we want to make use of wireless communication.

Radio waves travel poorly through water, also, the propagation of radio waves gets worse at higher frequencies. So wireless communication using the radio waves — the conventional method above water— is not feasible for our farm. Further down the EM spectrum we will find visible light that could be used for sending optical signals. Optical wireless underwater communication is being researched.^[23] But optical waves are affected by scattering. Moreover, transmission of optical signals requires high precision in pointing the narrow laser beams.

Conventionally underwater communications are realized by using acoustic waves. Acoustic wave technology has been in development since the end of World War II. Underwater networking, using a modern network protocol layer stack has also been researched.^[24] One aspect to keep in mind when using acoustic communications is that it could disturb marine life,^[25] this is a drawback which should be taken into account when deploying an ocean farm.

Energy

The ocean offers several alternative options for energy generation.^[26] When a robot can use it's own energy on the sea, it is more autonomous. Options for Alternative ocean energy:

Tidal energy: generates energy from the currents caused by the tides. The flow makes a rotor or foil spin and the mechanical moition is then converted to electricity. Tidal energy is in development and taking steps to commercial viability.
Wave energy: generates electricity from the height difference in waves. Wave energy is well developped and applicable in many different settings.
Salinity gradient: fresh water and salt water mix at the mouts of rivers, where energy can be harnessed from the osmosis process. This technology is in an early development stage with small pilots taking place in Norway and the Netherlands. It is one of the largest renewable energy resources that has not yet been exploited.
Tidal Range: Uses the difference in sea level with the tides to generate electricity. Fills a barrier at high tide and discharges the water from one side to the other at low tide. It is essentially the same technology as with conventional hydropower.
Ocean thermal energy conversion:is a very consistent energy source and provides so called base-load power. The temperature differences between deep cold waters and shallow warm and tropical waters is exploited to run a heat engine.

Proposed design

Description

Standard Japanese Laminaria farm.

Location Our own Dutch North Sea might just be to place to be. With an average temperature of 12 degrees,^[27] a former deadzone that is struggling with pollution from the many estuaries, and with a country that has always struggled with living beneath a rising sealevel, the seaweed farm has a lot to offer. When we also consider the busy shipping routes in the North Sea, Zeeland would be the most suitable area.
Farmed type of seaweed The HASP will farm the Laminaria seaweed species. Because of the high demand for it can not be fulfilled with the current techniques, and because it has a low impact on the environment.
System Design The entire farm will be modular to enhace repairabliity and be easy to expand. the modules will be modelled afet the traditional seawee farm. All modules square have a surface area that the harvesting robot can cover in 3 hours, after that it will have to return to the base station, located in the center of all the modules, to recharge and to dispense of the harvested seaweed.
Modular Our farem will consist out of square modules and a home base. The modules take the robot one battery charge - 3 hours- to harves. This way it can move efficiently around the farm. The modular construction improves the usability of the system. When one module breaks, it can easily be removed and repaired without creating disadvantage for the modules.

Automation

Seeding

Like at normal seafarming, the young seedlings will first be grown at land in a greenhouse in the summer, when the water is hot. Mid-November, when they have grown 10-15 cm, they need to be planted at the seafarm. The seedlings are attached to the vertical lines to grow out, with the upper plants receving more sunlight than the lower ones. Can one of our robots attcach the seeds to the ropes?

Control and hygiene

There are several diseases that could affect the seaweed, caused by bacteria or by the enviroment. These diseases can be recognized visually and envirmental factors can be measured. Sensors would be needed for: illumination (too much or too little light causes rot), fresh/salt water level and pollution. All diseases require different treatments. We could automate these treatments but the costs would not make up for the benefits. Therefore the system will alarm the farmer when the enviroment of the seaweed is turning hostile. This will be measured by light and osmotic sensors. When the recorded levels turn critical, the farmer is contacted so that he or she can check up on the seaweed.

Harm done by water grazers like fish can be minimized by placing the farm in deep waters, away from the coastal fish and the creatures on the seafloor.

Harvesting

Harvesting can be started in April. The plant grows faster in winter and slower in summer, with a rate of 1.1 cm per day in May. Making up for 2.5 meters a year. The plant can regenerate when it's been trimmed, but will grow slower. The normal age with this practice does not exceed 4 years. When the robot cuts off the seaweed it has to despense it. Returning to the homebase would be too time consuming so the harvested seaweed will be collected in a small container at the surface where the robot is located. Another option is a net that stays behind the robot, underwater.

Drying

It seems very inefficient to dry the seaweed in the open sea, it takes a lot of space and when one wave flushes over it, all the drying will have been for nothing. For that reason, seaweed must be taken to the mainland to dry. After it has been harvested, it must be stored for a short period, before it is transported. What amount of seaweed and for how long can it be stored without rotting?

Transport

When the seaweed is harvested from the lines, it is collected at the base station, when the farmer comes to collect it, the harvest is transported from the center of the system to the edge, so that the farmer can easily reach the seaweed.

Communication to mainland

Sensor readings about the enviroment are daily communicated to the farmer and perhaps the agencies that make use of the data. In case of critical levels of salinity, light or pollution, a warning is send out to the farmer so that he or she can check the seaweed on diseases.

Mapping tasks to robots

Energy

The PowerBuoy by OPT

With the climate crisis that humanity is facing, it would be highly unethical to use fossil fuels. Therefore, our farm will be powered on renewable energy sources. If system is capable of generating its own energy, it will be a lot more autonomous and low on maintenance. The most used renewable energy sources are wind and solar. However, the ocean offers many alternatives. Wave energy would be the most suitable for our design, because it does not require temperature differences, large surface areas, or specific locations. There are many different technologies for harnessing energy from the waves, ours must remain at one spot and be small. The powerbuoy developped by "Ocean power technologies" meets these requirements. The smallest version has a power capacity of 8400 Wh/Day at 80% availability.

Energy Requirements

The robot's motors use 27 kW/h but only move seperately, the robot can run for 3 hours after fully charging.
Communication:

Scalability

The farm will be expandable, consisting of square modules of ?*? meters for efficient charging anfd functioning of the robot. The seaweed will grow 2 meters beneath the surface to avoid over exposure to light. Vertical lines will be 5 meters long and 2 meters apart. To keep them straight, a weight of 400 grams will be attached to the ends of the lines. Young Laminaria seedings will be planted at 5 centimeters apart, making up for 100 plants per line.^[28]