Solar Lily to power undersea station

Oregon Department of Transportation / CC BY ( 16.03.2020: added mast, camera, number of devices and additional data line) Solar power and an undersea habitat does not seem to fit each other. But in 2012 I had the idea of a device that opens its harvesters only if the conditions are appropriate just like a hibiscus blossom at dawn. I called it a Solar Lily.

A bionic shape for harvesting solar energy

Solar LilyOur Solar Lily is folded together on the bottom of the sea. In its center is a buoy surrounded by solar panels. The whole set is held on the seafloor with a reinforced cable ending in a winch that is mounted on a block of ballast. When the sun is up, the waves low and the wind weak it’s time to wake up. The winch releases the cable and the Solar Lily starts to rise (lifted by the center buoy). Small buoys on the end of each solar panel are reaching surface first and make the panel tips drift away from the center, while the buoy is still under water and rising. When the buoy reaches surface the panels lay flat on the water, move gently with the waves and immediately start to generate energy that is transmitted to the habitat by the cable.

If one of the alert conditions appear, the winch starts to drag the buoy down again. The swimmers on the ends of the panels approach the center and folding around it while the buoy is lowered .

On the seafloor the Solar Lily then waits for its next assignment. There it will not be exposed to the forces of waves and winds. Currents will make it lean like kelp, while the surfaces of the solar panels are secured by being folded with their faces to the center, where they protect each other.

Solar Lily

To be discussed

The possible size of the panels has still to be discussed as well as the ideal shape of the ‘flower’: do the corners have to be empty or is there a way to design them in a folding triangle shape similar to Origami.

How much loss of energy will appear while transporting energy from the panel to the winch and from there to the storage bank inside the habitat. To calculate the necessary length of the cable we have to sum up the following parameters:

  1. Depth (surface to seafloor)
  2. The amplitudes of tides and waves.
  3. Drift Scope (might also result from step 2)
  4. Safety Distance (winch to habitat)
  5. Handling Bonus inside the Habitat

A depth of 20 m might end up in a cable length of 60 m after all. Maybe the loss of energy is that high that it rules out the whole concept for being not effective enough for example if the winch uses all the energy that the Solar Lily is producing. That would truly be self-sufficient 🙁

How many Solar Lilies do we need? If the panel size is not enough we can increase the number of lilies around the habitat.

How can we store the energy inside the habitat? How can we maintain the winches, when they are exposed to salt water 24/7? Would the angle of the solar panels on the surface towards the sun be appropriate? And is the whole system feasible at all compared to other alternatives or at least in combination with other solutions?

Can we use waste air from the habitat to fill the buoy on the seafloor to ascend, while releasing the air on the surface would let it sink again in order to save energy from the winch?

Controlling the Solar Lily

If all these questions lead to a positive end result we can finally think of implementing the set to the IT system, that measures the alert conditions and decides by itself if and when the Solar Lilies are risen or lowered. Again: the conditions would be a) time of the day, b) wave height, c) wind speed, d) are the winches clear of personnel, e) are there reported damages on the equipment, f) is the emergence area clear (boats, swimmers, drift items). If these conditions allow operation of the winches the IT system would be free to decide whether operating or not. Maybe a request of confirmation should be considered.

Additional functions

  • a mast in the middle of the buoy with a camera to monitor the devices condition on the surface. There has to be an additional data line to the surface next to the holding cable.
  • additional GSM receiver to support/backup telemetry or telecommunication
  • a weather station to measure environmental conditions.
  • mirror reflectors would not only mark the lilies position but also the station’s

Image credits: Oregon Department of Transportation / CC BY (, available on Wikimedia Commons

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5 Replies to “Solar Lily to power undersea station”

  1. Great idea! I imagine a sub-sea station with four Solar Lilies, one at each corner. They are attached to arms, in order to avoid collisions when surfaced. I am too lazy to draw a sketch, but look at these quad-copter drones and you know what I mean.

    Why do you want to open and close the panels at all? A true flower blossom has to close for its own protection, because it cannot move down an dig into the ground. But the Solar Lily is safe when down at 20 meters depth. What is the the folding mechanism good for?

    By the way, there are many solar power calculators in the web. You can enter the geographical position, the size and inclination of the panels and the calculator outputs the statistics for electricity production over a year. But as a rule of thumb, say 100W per square meter.

    1. Hi Mike. Some years ago the administration of a city nearby sank an old coast guard ship to set a new dive spot on 30m depth. The ship was about 30m long and made of steel. It took only one winter and the ship was rolled over and changed its location by appr. 70m, where it was stopped by a rocky slope. I never expected that a current could be that powerful in that depth (the spot was badly chosen as well :-)). Now some years are gone and the ship even broke into several parts. So, whatever we build underwater should be protected as well as possible. By folding it, the panels would face each other and minimize the total surface. Additionally if they are able to swing and lean with the current, they should survive most weather conditions. Not to mentions potential technology killers like hungry turtles, curious octopus…
      You are right, they should be located around the habitat in a certain distance, so that they are unable to collide. There could be arms from the habitat or just moorings on each of them.
      I will check out the calculators. What do you think: a panel size of 2x1m, plus 2 wings each 50cm, with four panels per lily, makes about 16 sqm or about 1600 W. Does that seem realistic? Then we still have the loss by transferring the energy to the habitat.

  2. Maybe I am the wrong guy to ask for realism … when you assemble a Lily with a total of 16 square meters, and you put four Lilies onto your habitat, you end up with 6400 W. That’s probably enough to supply an air compressor for the SCUBA tanks of the aquanauts during sunshine, plus light and control system, plus battery charging for power supply at night.

    Most of the electrical losses do not occur in the cable between the panels and the batteries, but during charging of the batteries and (if required) the transformation from DC to 230V AC. If the habitat is supposed to be completely independent, you also need compressed air at 4 bar for the station, round the clock. In that case I am not sure whether 6400 W are enough.

    I did not expect a storm to be still that powerful at 20 meter depth. When the panel size is 1 by 2 meters, the square piece in the center is 1 by 1 meter. And 1 m² is the surface area the storm will attack, even when the Lily is closed. There will be very powerful forces to handle.

    How about connecting two 2×4 meter panels along the long edge? That would be really flat and could be secured against the station’s hull.

    1. 6400 W would be amazing! I agree, that probably it would not be enough for scuba tank compressors. That’s why I’m so curious about the Biocoil. This is the plan for a ‘Blended Atmosphere’: 1. We generate a certain percentage of oxygen by ourselves (via Biocoil or similar?); 2. We wash out the carbon dioxide with standard scrubbers; 3. We additionally use oxygen (!) tanks to blend the atmosphere we desire. Well, of course, this is the plan for the last stage.

      Another idea is not to fill scuba tanks with air, but to provide a steady flow of air, means to pump only as much air from the surface as we need. For example: depending to his physical activity a human being needs between 8 and 50 l/min. of air (the respiratory minute volume). This is the average rate used for scuba diving activities. But we are talking about a habitat with humidity, odours and maybe several other components. Therefore we have to use a certain ‘atmosphere exchange rate’ of about 0.5 or 0.8 per hour (in residential houses), which means: we should be able to change 50% or 80% of the complete habitat volume in one hour, multiplied with the ambient pressure. (I will investigate these data on Aquarius and Sealab) In our example: 20 sqm of habitat results in appr. 50 cbm of volume; multiplied with 3 bar (in 20m depth) results in 150 cbm, or 150.000 l/h and an output of 3 bar. We have to find out the electrical load for a compressor with these specifications.

      For the first missions (with short stays) it might be enough to have large compressed air tanks, refilled via hose from the surface vessel.

      (I will distil these options and add them to the subcategory breathing gas processing)

      I can not really imagine what you mean with securing the panels at the station’s hull. That would reduce the size of the panels drastically, or?

  3. It is great to have people on board with a much bigger knowledge. Thank you for your your expert contribution, Mike.

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