bioWAVE(TM) is intended for use at 40-45m depth and is anchored to the sea floor. The bulky parts you can see on the picture are floats which allow the structure to move back and forth with the current. As the waves make the surface move up and down, the current under the surface has a back and forth movement which the floats follow. That oscillation is mechanical energy which is converted to electric energy via a hydraulic system. The movement is used to put fluids under pressure, that pressure is used to spin a generator which then produces electricity. Just for a scale, one bioWAVE(TM) unit should produce 250kW, an average wind turbine produces 5MW.
Now we've all seen (if not experienced) how mighty the sea can be: tremendous forces are at play and you gotta have a bit of respect for that if you intend to survive in such an environment. So BioPower Systems who wanted to harness the power from ocean swells had to find a way to make their units robust enough for these operating conditions and they turned to Nature to find solutions.
Their champion: the bull kelp! Not very sexy, i agree, walking on kelp on the beach is not very tempting except for kids maybe... Anyway, bull kelp is very good at withstanding strong water movements. Here are a few interesting strategies the bull kelp uses and that inspired the bioWAVE(TM)'s design:
Strong root-like system called holdfast. The holdfasts are not called roots because they don't go deep in the ground but rather stay close to the surface creating many anchor points that redistribute vertical and lateral forces.
- Buoyancy: the kelp has gas filled bladders that float and keep the kelp upright. From the bladders emerge blades that need to be close to the surface to absorb sunlight for photosynthesis.
- Kelp moves with the currents rather than resisting them. That way it can withstand very strong currents.
The three strategies mentioned above were reused in bioWAVE(TM) design as follows:
- Holdfast-like anchor system allows it to not drill deep in the ground, minimising cost and damage to the seafloor.
- Floats allow for buoyancy and movement with the sub surface currents.
- Flexibility of the kelp reproduced by using a swivel and pivot system allows the structure to rotate in the direction of the current. It also can lay down close to the seafloor when the current gets too strong, minimising the forces seen by the structure and the risk for damaging and 'uprooting' it
This post is based on an assignment i got in the Essentials of Biomimicry course and the feedback from instructor Zeynep Ahron.