Byjnikola
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Challenge
Spook Louw Aug 08, 2022
Can we come up with an alternative, more feasible, design for harnessing tidal energy?
Image credit: Energy People
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Can we envision an alternative design to harness tidal energy?
Currently, we have three methods for harnessing tidal energy:
- Tidal streams
- Barrages
- Tidal lagoons
We realize that tidal energy has massive potential, but we are struggling to move past the current limitations in harnessing it.
The limitations of currently available methods:
- Tidal energy power plants are extremely expensive to construct.
- Harnessing tidal energy tends to have a negative impact on marine life.
- Tidal energy outputs is dependent on the tides, not constant.
Can we envision a different method of harnessing tidal energy that eliminates some of the limitations of currently available methods?
2
Creative contributions
A mesh of floating energy generating baloons that contain mechanical beads
I imagine a system something like this. Let me break down the idea. Look at the labels in the sketch below:
- The green bulb-like structure is a 'floating' or 'patially-submerged' balloon.
- The red dots inside the green bulbs represent 'beads'.
- The blue thread represents a conducting wire that is sufficiently branched to hold the balloons in the terminal ends of the branches.
Here, the idea is to convert the kinetic and static energy produced by the collision of the beads inside the balloon containers into electrical energy and collect the electrical energy through the wires into a central energy storing device such as a battery. Since the water in sea/oceans is constantly moving on the shores, the tides will perpetually move the balloons in a random motion. The beads inside the balloons will constantly keep on colliding with each other and hence generate energy. If this can be converted into electricity, we can have a constant source of energy in virtually all shores of the world.
This is a hypothetical concept and I would love to hear from someone with engineering background to see if it even makes sense.
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Underwater elevator
R
I imagine an elevator underwater, just below the surface.
It moves up 1 meter when the water level rises, by being slightly lighter than the water volume it displaces.
It moves down 1 meter when the water level decreases, and the mass of the object generates a greater force when it comes down.
By calculating the properties of the object, it could be engineered to stay at a certain depth.
I would dig a very deep hole, place a lot of objects calibrated for different depth ranges, like a vertebral column, and then use the force they generate when tide is lowering to generate electric current.
The generator could be on the surface, and it could be connected to several elevators like this, to minimize maintainance costs.
It could also act as a battery, when the elevator is high, the cable that connects it with the pulley system and with the generator could be stopped, and when energy is needed, it could be allowed to be lowered, resulting in a more consistent energy output.
It could be built entirely on land and just lowered into a hole, or dumped where the water is deep enough and it would settle by itself into place. The only things that needs installing are the pulley system and the generator, and if we're near the shore, those could be installed on land. If we're not near the shore, we would need a floating platform that would support the entire structure.
I'd just do the entire installation somewhere near the shore on land, and then dig a ditch from the sea to the elevator so that the water communicates with the hole I made for the instalation. This way I would still have the option to close the ditch and drain the well.
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Spook Louw2 years ago
This sounds like an excellent idea. It would be a lot cheaper than building an entire plant offshore, and it would have less of an impact on the marine ecosystems.
How large would such a system need to be in order to generate a return on energy that would make it worthwhile?
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R
Razvan2 years ago
Spook Louw Considering the tide range is 1 meter, and that the water level raises and decreases once per day, I'd estimate it would need to displace around 1,440.00 cubic meters of water to generate 216 kwh per month, enough for a basic level.
To answer your question on how large it would need to be: 10 cubes with the side of 5.25 meters would sum up to approx. 1,440.00 m3.
And a gear/pulley system to translate the slow liniar motion into rotation for a small 300w low rpm motor.
After doing the math it becomes clear to me that this method is best for waves and not tides, because the height difference caused by the waves would sum up to a lot more in a single day.
And considering the wave form, it's probably better that the object would be shorter on the axis that goes from the shore to the sea, and bigger on the axis parallel to the shore. So, instead of an elevator design it's probably simpler to just have a narrow object that is as big as possible and you get to make it heavy enough to just touch the surface of the water. The heavier the better, because it generates energy when it goes down.
If it's for waves, the system doesn't have to be this large. It could be X times smaller, where X is the ratio between the number of waves per day and number of tides per day. I would imagine there are at least 5 waves per minute, resulting in a ratio of 7200.
Which would be 0.2 cubic meters if the waves are causing a height difference of 1 meter between their high point and their low point.
Note: I assumed the system would generate electricity when the object descends as well as when the object rises.
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Spook Louw2 years ago
Razvan Thank you for your detailed, well-thought-out input. From what you have said, I see no reason that such a system shouldn't be feasible. Of course, waves are less consistent than tides, which is why the original challenge focused on tides, but this seems to be an effective solution nonetheless.
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Add your creative contribution
General comments
Shubhankar Kulkarni2 years ago
Another limitation of the currently available methods is that they are close to the shore and any construction/ machinery there will hamper the tourism, scenic beauty of the place.
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