Wasteshark
Plenty of trash can be found in the beautiful quays of Leiden and many other cities. Not just in the Netherlands, but around the world. The trash can stay in the water a long time before it is collected, or be transported with the flow towards the sea. In all cases trash can release or degrade into (more) harmful substances. There is a great difficulty to remove such trash from the water. Removing the waste is currently done periodically by large boats, from the quay, or collected mechanically at specific points like water treatment plants. Each has great disadvantages. Boats are large and require a lot of fuel. From the side of the water it can be hard to reach all trash. The mechanical collection is fixed in place. What all suffer from is also the long periods in between collection. During this period the trash can have all manner of short and long term effects.
The waste shark should make collecting trash in the water easier. As a small specialised craft if should be energy efficient, operate more frequently and be able to target trash more effectively. Makerspace Leiden has decided to pool their expertise in creating a wasteshark. The ultimate goal is to garner good PR for Makerspace Leiden by showing off the Makerspace expertise and inspiring to reducing a growing problem.
The wasteshark is in essence a small water drone with a trash collection system. This can be implemented by dragging a net, cage or a small conveyor system to deposit trash in a collector. It can be environmentally friendly with rechargeable batteries.
The complexity of the waste shark can go from relatively simple to extreme. A few comparisons below.
Inhoud
The original idea of the wasteshark is a fully autonomous water drone. It can detect and collect trash without intervention. Although unclear from the initial idea, it seems evident it needs to recognise moving water traffic and handle accordingly (and in actual fact - colregs require significantly more of a vessel; including keeping watch by all available means).
Finally it needs a way to deposit collected trash.
Some of the navigation hardware seems available by one of the Makerspacers in the form of LIDAR equipment. The complexity can be further reduced if advanced software from existing companies can be used.
Other ways to reduce complexity is for the drone to be semi autonomous. Part of the navigation is controlled by an operator via a remote control. The introduction of an active operator also makes it easier to empty the drone when full.
A final option would be to give it relatively little meaningful control or steering; but instead let it to some extent follow the surface current/wind just above the water; as it then automatically ends up with the same trash that it wants to collect.
Trash collection style
Trash can be stored in or out of the water. Two ideas where the inspiration came from showed one with a cage under the water, the other a conveyor with a cage above the water line. The cage (or net) under the water line greatly simplifies the idea. However, water has a great resistance. As the uneven trash is collected it will reduce energy efficiency. Furthermore; as most trash that is realistic to `catch' without full trawling will be positively buoyant - a half submerged net will be self limiting.
A conveyor, belt or other method to lift the trash out of the water will alleviate this problem, at the cost of a bit more complexity and more points of failure. It does however address the surface failure mode of a net.
Trash deposit style
Depositing the trash can be automated or manual. Automated introduces much more complexity. The drone might require removal from the water, or automated mechanisms to gather the trash. Easiest is if the trash collector is easily accessible, it can be lifted and emptied like garbage trucks do with garbage cans. Manual can be as easy as shaking the drone above a bag.
If a conveyor belt or similar is used; trash may be deposited in a bun or some similar scuppering arrangement to get rid of excess water.
Removal from the water
The drone should be removable from the water in all cases. Anti fouling and maintenance are required. Trash removal might require removal from the water as well. Quays within the city often have high walls and depending on the location few easily accessible areas. A lift in the water is quite complex. A ring where a pole with a hook can connect is easy.
Writers preference
If good software and hardware are available, I would prefer a nearly autonomous drone. It would do it’s duty and give a ping to the operator when full with trash, battery low or other special circumstances. It can then be serviced, after which it can return to do it’s duty or be stored. The operator can also request the drone to return if required, as well as take control of the movement
It should be energy efficient, lifting the trash from the water. It would need a large trash container for longer trips on the water and have a slow speed. This assures long operating times and a large area cleaned per use.
Automated removal of trash or removal from the water would make the drone overly complex for little extra value, unless a fully autonomous drone is created that can operate for days, weeks or even months at a time.
A semi autonomous drone is preferred when fully autonomous isn’t available. The higher dependency on the operator means sacrificing some of the efficacy of the drone. An operator is more likely to get fatigued or bored, which ends a cleaning session at an earlier time. A faster drone will keep the drone effective and reduce fatigue of the operator, sacrificing some energy efficiency. The energy efficiency is a lower priority thanks to the smaller sessions. Lifting trash out if the water is also less of an issue, resulting in a less complex build.
General notes on the build
A catamaran form looks like the best design. It is used by both companies for probably more reasons than we can easily guess. Stability and a ‘natural’ collection area come to mind. It also offers place for two propellers. The blades can spin slower for higher efficiency and can be used for higher manoeuvrability, like spinning in place. It also isn’t dependent on water pressure against a blade, making it the safer choice. It does require two propellers with corresponding engines. The catamaran design can be made bottom heavy by adding the batteries to the hulls in the water.
We could possibly improve the design of the other two options. Robot vacuum cleaners use a small rotating brush to move dirt from the edge to the collector. This can be applied to the waste shark. At the cost of extra drag, you can more easily catch trash against Quays, boats or other places where you can’t use the main collection point by just floating over the trash. Doing so with a small water flow (as opposed to an actual brush) may be simplest; and alleviates the need for an extra pump or motor.
