Lambertseter swimming pool in Oslo one Saturday evening: A small submarine-like vehicle, some tens of centimetres long, glides down into the water, turns around, and slowly floats back up.
Researchers at OsloMet have finally managed to make it move in the way they want it to, after many failed attempts.
They have made adjustments and adaptations after each attempt until it finally submerged and surfaced from the water successfully.
Consumes very little energy
The small vehicle is known as a miniature underwater glider (MUG).
‘Underwater gliders move using very little energy. They can therefore operate for a very long time before they have to be recharged; they can monitor the environment and collect a lot of data,’ says research assistant at OsloMet, Ivar Bjørgo Saksvik.
He is testing the solution alongside PhD research fellow, Moustafa Elkolali, research assistant Erik Tobias Sollesnes, staff engineer Ahmed Al-Tawil and professor Alex Alcocer.
Associate professor Alfredo Carella, professor Vahid Hassani, and head engineer Rune Orderløkken are also on board, and many electrical engineering students and European Project Semester students have also contributed.
Deployed and retrieved by drones
Out in the ocean, the underwater gliders are to be deployed and subsequently retrieved by drones. The batteries are charged on unmanned surface vessels using electricity from solar panels.
Testing the buoyancy
The buoyancy system, which makes the glider submerge and surface, is being tested at Lambertseter swimming pool.
The glider has a flexible bladder that can expand and contract. When the bladder expands or contracts, the volume changes so that the glider becomes heavier and sinks, or becomes lighter than water and surfaces.
‘We use a mobile phone app to communicate with the underwater glider; it can activate the system and send different pumping intervals to test the bladder,’ Saksvik explains.
‘When the time comes to test it in the sea, we will use a low power cellular modem. The launch of the new low power cellular modems from Nordic Semiconductor allows us to connect the glider to the “Internet Of Things” out in the ocean.'
In the next round of testing, the researchers are going to try to find out how much oil is pumped to the underwater glider’s bladder, to make it easier to steer the buoyancy.
Reduces costs and risks
A system of underwater gliders, drones and autonomous surface vessels can reduce costs and the risks associated with deploying people far out in the ocean in remote areas, by removing the need for large manned vessels.
Researchers have also identified unmet needs for underwater gliders that can monitor and map fjords and coastal areas.
There is cellular coverage along almost the whole Norwegian coast and in almost all the fjords, which allows the small underwater glider to communicate when it surfaces and transfer data and its GPS position.
Can be equipped with important measuring instruments
The OsloMet researchers cooperate with other academic groups, e.g. Norwegian Polar Institute, and NTNU where an autonomous drone, drones, more precisely Unmanned Aerial Vehicle (UAV), is being developed that can be deployed to retrieve the underwater glider.
They are also cooperating with the German company TriOs Mess- Und Datentechnik, which is developing an optical fluorometer that measures chlorophyll, among other things, and can map toxic algal blooms, and they are experts on optical underwater sensors.
Instruments can also be used to measure whether there is enough oxygen in the water for fish and animals to survive, and whether for instance the CO2 level in the ocean is too high.
Furthermore, an instrument can be added to the glider enabling it to find oil spills through UV radiation (fluorescence).
‘This gives us a good overview of the condition of the water quality from the surface right down to the seabed,’ says Saksvik.
‘We have developed the underwater glider to easily be able to change instruments as needed.’
The researchers have noted that measures are increasingly being implemented to conserve marine ecosystems in the fjords and along the coast. The OsloMet researchers’ research project, OASYS, could prove useful in that context.