Solar cells have become a common part of our daily lives, from massive energy farms to common appliances like outdoor lights and cell phone chargers. Now they’re going somewhere we didn’t expect solar cells to work, under the ocean.
If you are a person or machine working and collecting data underwater, maintaining clear lines of communication with the surface is pretty high on your list of necessities. Divers, manned submarines and autonomous robots working in the world’s oceans collect all kinds of useful information about underwater activities, including the migration of animal populations and changing environmental conditions.
Bringing this information to the surface where scientists can use it has proven difficult. Often satellite communication networks are required and sometimes information cannot be transmitted until the person or craft clears the surface, or long communication cables up to the surface are required . Indeed, there is a need for reliable, high-bandwidth wireless communication systems capable of operating underwater.
A recent study by scientists from Zhejiang University and the Engineering Research Center of Ocean Sensing Technology and Equipment in China, published in the journal Optical lettersexplores the potential of solar cell arrays to act as wireless underwater communication networks.
Traditionally, information is transmitted wirelessly through water in two ways. Radio waves have the advantage of longer wavelengths, but they don’t travel very well through water. Traversing the aqueous medium requires higher power and has excessively high latency. Optical communication is better in these respects but has its own limitations.
Picking up an optical signal requires precise alignments between the transmitting and receiving units, which is difficult to achieve and maintain over long distances under the ocean. As such, wireless optical networks are limited by distance, you can only send a signal reliably so far.
Scientists have turned to solar cells as a potential solution to this problem. Solar cells are designed to sense light from a relatively large area and convert that light into electricity. However, previous attempts to use solar cells for communication have themselves run into problems, as the technology was intended for energy harvesting, not communications.
The Zhejiang University team used a modified configuration consisting of a 3-by-3 array of solar cells. This array had a detection area of 3.4 square centimeters. They placed the detector at the end of a seven-meter water tank, in front of a transmitter. The signal path was extended using a series of mirrors, so the total length the signal traveled was 35 meters.
The experiments achieved a bandwidth of 20 decibels at 63.4 megahertz, a vast improvement over previous optical systems. It is also free from the latency issues found in non-optical communication networks and uses significantly less power. Moreover, the bandwidth increases with the size of the network of detectors. If implemented in the real world, connected solar cells could make for much larger receivers, further improving data retrieval and bandwidth.
This form of wireless underwater communication also has other advantages. Unlike other emerging technologies, solar cells are already in use around the world. Their use for this application would not require the creation of new factories or the development of new manufacturing protocols. Solar cells can be acquired from already established commercial sources.
Also, using solar cells for data collection does not prevent them from performing the job for which they were designed. Although the solar cells are not currently collecting information, they could continue to collect sunlight – although this may be limited by the amount of light present at depth – to power the system. Depending on how the system is implemented, wireless underwater communication could potentially be entirely energy neutral.
If we can find a way to deploy a large-scale wireless system, we might finally be able to stop sharks from trying to eat the internet.