Elephant

By PlastcBusters

-Introduction to the challenge-

Since the 1970’s the worldwide 1problem of plastic pollution has been acknowledged by scientist1, just in 2015 has been estimated that the marine species affected by microplastics (plastic residuals with dimensions under 5 mm2) are around 680, against the 247 just fifteen years before3, with an exponential growth still going4.

As of today, the estimates for the quantities of plastic thrown into the oceans are still uncertain, as the quantification is not easy, but a study affirms that every year the quantity of plastic of any sort that reaches water is between 0.5 and 12.7 million tons5, which then stays afloat or is ingested by fish eaten even by us6,7.

Our project is to create a mean to clean the surface of the seas from all kinds of debris introduced by humans, as to eliminate both macro and micro plastics.

-Data analysis-

By analyzing the superficial current flow thanks to data furnished by NASA8, and after combining report from ESA9 and surveys10 from the Mediterranean Sea zone, lead us to select a zone near the coasts of Malta, where the density of microplastics is far higher than in most of the oceans.

-Overview-

To clean the surfaces, we thought of a small barge, 3 meters in width and 5 in length, made in fiberglass, which utilizes Archimedean screws to collect the most superficial part of the garbage,

The complete system is sustained by renewable energy resources and the ship is guided by a semi-autonomous navigation system, which requires little to no overview, except in particular stages of the operations.

The weight of the boat (around 5 tons) is supported by two buoyancy chambers put under the barge itself, that have as well the function of hull, allowing less drag.

We named our project “Elephant”, as its appearance resembles an elephant, with the three screws taking the part of the trunk and the tusks, and considering the pacific attitude of this creatures.

-Semi-autonomous Navigation-

Elephant will use data from the ESA maritime identification system, SAT-AIS11 to pre-establish a possible route to get from a starting point, collected by a GPS system on-board, to reach an established point through coordinates and the help of a gyrocompass, using a pre-trained neural network to predict the route that the nearby vessels could take.

To avoid errors or little ships (for example, fishermans’ boats) which could not be identified through the satellite system (with those vessels the neural network could have problems to predict the course that will be taken), a radar system is installed, connected to a computer that allows the boat to deviate if the obstacle is too close.

-Renewable resources-

To propel Elephant, 2 x 3.7kW independent electrical motors12 are mounted inside the lower part of the hull, controlled by the on-board computer and allowing the maneuvering of the ship, allowing the barge to reach up to 20 knots of speed.

To sustain the power request, the barge’s top is covered in solar panels, which, considering the annual mean solar irradiance in the Mediterranean Sea13 and the efficiency reached for solar energy conversion14 can furnish 5 kW of power, allowing a cruise speed of 14 knots.

The unused energy is collected inside Lithium-Ion batteries, reaching a total capacity of 40 kWh with a weight of 278 kg15, allowing the use of both the motors at full power for over 3 hours even without solar energy

-Trash collection-

The trash is collected through 3 Archimedean screws (1 meter of diameter, length of 1.5 m) put on the front of the deck, reaching up to 50 centimeters under the surface to collect most of the superficial plastic residuals in one go.

The screws, made in fiberglass, are covered in the upper part (not shown in the render for clarity) to avoid the possible falling of garbage back into the sea, and lead the collected trash altogether with some water to the deck, allowing the action of the filtering system.

• While the collection is in act, the motors spin at minimum power and a third motor, much less powerful, moves the screws at constant speed at around 1 rotation per second, collecting every minute around 3600 kg of water.

-Filtering-

Once the polluted water reaches the deck, a tilted plane allows it to slide to the end of the boat, bu before reaching it, a net with holes of around 5 millimeters allows the water and the microplastics to pass through it, dividing the bigger residual from the rest.

A few decimeters under the first filter, a second filter is positioned.

Here the water is divided from the microplastics using a 200 μm graphene filter16, eliminating most of the polluting microparticles, and then released back into the sea, as to allow maximum capacity for the vessel.

-Lifesaver-

To prevent the local fauna from harming itself by getting too close to the barge while in “collection mode”, a small sonic disturber is put under the boat, as to move away the fish in a nearby area17.

The soundwave used is middle frequency (800 Hz), as to be annoying but not dangerous, and is power outcome is small, to reduce as much as possible collateral damages to whales and other animals which are sensible to this kind of interference18.

-Cost and Feasibility-

The cost of the boat should be between 30k and 40k$, but as this is project is still in development and needs a lot of designing work, this is a raw estimation based on mean prices of the various components.

The major point of advantage is the low cost of maintenance, as one operator can control easily multiple boats, and the filters can easily last for days without any intervention to clean them (depending on the density of the patch of plastic), the solar panels require cleaning every 2 months19.

The major cost in maintenance are the batteries, which slowly lose capacity over time20, but as the boat is mainly used at low speed, these batteries can last for at least 1 year without a great loss of capacitance.

To allow the feasibility of the project, considering the capability of autonomy of Elephant, it could be used for on site research, by equipping it with various sensors, or, by increasing the power of the radar, as a control point for illegal maritime traffic, or just control over the normal traffic, for real time data.

A direct source of income could from the selling of the collected plastic, as the market of recycling is developing fast in the latest years, or from the direct selling of boats to cities on the seaside, as to allow them to keep the coastline clean from the plastic brought by the tides.

-Future Developments-

As Elephant utilizes many new technologies, there is great place for improvements.

With new technologies developed for the solar energy, bigger boats could be possible, making it able to collect larger quantities of garbage without the need to deposit it.

Better satellite data could improve the autonomy of the boats, leading to a reduction of the prices and the time necessary to operate.

Further development of the lithium-ion batteries could instead bring down the maintenance prices even more.

Neural Network, as it is still in its early stages of real development, could lead to a completely autonomous fleet of boats, able to clean and deposit at a rate otherwise impossible.

And moreover, this project could be a playground for all this new technologies, helping the research.

Sources

1 – F. Coleman, D.H.S. Wehle, “Plastic Pollution: A worldwide oceanic problem”, Parks, vol.9, no.1, pp.1 Apr.-Jun. 1984.

2 – Giuseppe Suaria, Carlo G. Avio, Annabella Mineo, Gwendolyn L. Lattin, Marcello G. Magaldi, Genuario Belmonte, Charles J. Moore, Francesco Regoli, Stefano Aliani, “The Mediterranean Plastic Soup: synthetic polymers in Mediterranean surface waters”, Scientific Reports, vol. 6, no. 37551, pp. 1 Nov. 2016.

3 – François Galgani, Christopher Kim Phan, Julia Reisser, “Plastic Pollution”, Frontiers in Marine Science, vol.4, pp.307, 2017.

4 – Autumn R. Iverson, “The United States requires effective federal policy to reduce marine plastic pollution”, Conservation Science and Practice, vol.1, no.6, 2019.

5 – Romain Tramoy, Johnny Gasperi, Rachid Dris, Laurent Colasse, Cédric Fisson, Sarah Sananed, Vincent Rocher, Bruno Tassin, “Assessment of the Plastic Inputs From the Seine Basin to the Sea Using Statistical and Field Approaches”, Frontiers in Marine Science, vol.6, 2019.

6 – Alezandra R. McGoran, Phillip R. Cowie, Paul F. Clark, James P. McEvoy, David Morritt, “Ingestion of plastic by fish: A comparison of Thames Estuary and Firth of Clyde populations”, Marine Pollution Bulletin, vol.137, pp.12-23 Dec. 2018.

7 – Jennifer E. Halstead, James A. Smith, Elizabeth A. Carter, Peter A, Lay, Emma L. Johnston, “Assessment tools for microplastics and natural fibres ingested by fish in an urbanised estusry”, Environmental Pollution, vol.234, pp.552.561, Mar. 2018.

8 – ESR. 2009. OSCAR third degree resolution ocean surface currents. Ver. 1. PO.DAAC, CA, USA. Dataset accessed 19 Oct. 2019 at https://doi.org/10.5067/OSCAR-03D01.

9 – http://www.esa.int/Enabling_Support/Space_Engineer...

10 – Giuseppe Suaria, Carlo G. Avio, Annabella Mineo, Gwendolyn L. Lattin, Marcello G. Magaldi, Genuario Belmonte, Charles J. Moore, Francesco Regoli, Stefano Aliani, “The Mediterranean Plastic Soup: synthetic polymers in Mediterranean surface waters”, Scientific Reports, vol. 6, no. 37551, pp. 2-4 Nov. 2016.

11 – https://artes.esa.int/sat-ais/overview

12 – https://oceanvolt.com/solutions/systems/ax-shaft-d...

13 – https://power.larc.nasa.gov/data-access-viewer/

14 – https://news.energysage.com/what-are-the-most-effi...

15 – https://www.torqeedo.com/en/technology-and-environ...

16 – https://www.dezeen.com/2018/03/04/graphene-water-f...

17 –University Of Liege. "Deep Sounds Scare Fish Away From Turbines That Could Kill Them." ScienceDaily. ScienceDaily, 16 May 2007.

18 –Brandon L. Southall, Kelly J. Benoit-Bird, Mark A. Moline, David Moretti. Quantifying deep-sea predator-prey dynamics: Implications of biological heterogeneity for beaked whale conservation. Journal of Applied Ecology, 2019; DOI: 10.1111/1365-2664.13334

19 – https://www.solaralliance.org/solar-panel-cleaning...

20 – Waldmann, T.; Wilka, M.; Kasper, M.; Fleischhammer, M.; Wohlfahrt-Mehrens, "Temperature dependent ageing mechanisms in Lithium-ion batteries – A Post-Mortem study". Journal of Power Sources. vol.262, pp.129–135, 2014.