The Yucatan coastline has been undergoing severe erosion for years. Some houses have already collapsed into the sea. In some parts of Cancun, the waves are encroaching so far that one meter of beach is being lost every six months. The hotel shown in the aerial photographs (Figure 1), located in Playa Del Carmen, is now deploying sandbags in front of its foundations to protect against the encroaching tides.
The situation is complex and is exacerbated by structures being built in the sea that affect conditions down current. The erosion threatens livelihoods and communities broadly surrounding Cancun and Mexico’s Yucatan Peninsula.
What’s causing the erosion? Dying reefs and the increasing strength of waves. A rise in sea temperature of more than 2º Celsius, as a result of global warming, can result in acidification and coral bleaching. Warmer temperatures are causing parts of the Mesoamerican Reef near Quintana Roo, Mexico, to be ravaged by what is known as ‘white syndrome,’ a disease capable of killing corals in fewer than 40 days, experts say.
To reverse the trend, CCell has spent months working on a pilot project comprising a full-scale reef in Telchac on the northern coast of the Yucatan. Three further pilot reef units are already installed in Cancun, with another two to follow.
CCell’s solution aims to halt or even reverse threatening tides by mimicking growth conditions of natural coral reefs. The reefs cause waves to break at sea and can neutralize up to 97 percent of a wave’s energy before it hits the shore. CCell-built reefs have the added benefit of porosity which can further reduce wave energy. The larger waves, which tend to remove sand from beaches, are broken up while the small waves that deposit sand onto beaches are allowed to pass through.
The science of fabricating reefs CCell creates coral reefs by using a safe electrical current to grow limestone rock from sea water around a steel frame. In nature, this process of accretion can take hundreds of years. By contrast, CCell’s electrolysis can develop a functional reef within a few months in the right environment, which can evolve into a mature coral reef within 36 months.
CCell’s electrolysis forms bulk on a steel structure by passing the low-voltage current between the structure and a small metal anode. At the anode, oxygen is generated, which is marginally beneficial for marine life. At the cathode, the pH rises which induces precipitation of dissolved salts in sea water on the steel surface. The rock formed is mainly aragonite (calcium carbonate) and brucite (magnesium hydroxide), which seals the steel structure and protects it from corrosion.
Soon, divers can attach corals grown in local hatcheries to the rock. Research has shown that these grow two to three times faster than normal because of the optimal conditions created by CCell.
For the electrolysis process to work correctly, the voltage supplied to the steel reef structure must be precisely controlled and varied over time between 1.2 and 6 volts. Any less and electrolysis cannot take place, and the rock being formed becomes spongy and less suitable for coral growth. This potential difference between the anodes and cathodes drives a precisely calculated current through the seawater between the electrodes. This is necessary to achieve the optimum electrolysis process to grow strong, sustainable rock deposits.
“Our ability to control the output voltage accurately and consistently has transformed our work and research,” said Dr. Will Bateman, CEO of CCell. “Each offshore installation has now become a live test site that we can remotely control. By implementing concepts that we were developing in the lab immediately in the field, we can also take field observations back to the lab to verify in a controlled environment.“
Maintaining precise electrode voltage is challenging for many reasons. One source of power is an innovative wave-energy converter, developed by CCell, which uses a sturdy paddle to drive a hydraulic system for producing electricity. The electrolysis control system must monitor and regulate this supply, which varies widely in voltage – from 35V to 70V – according to wave conditions. It must also allow for other factors, including seawater composition, water temperature and flow rate over the electrodes.
Precisely controlling the widely fluctuating renewal energy resources
The power delivery network (PDN) consists of a front-end conversion and regulation stage followed by a downstream point-of-load (PoL) regulation stage for the system’s monitoring and control electronics. Power is delivered via a cable from the wave-energy converters to the electrolysis system.
Each 2.2-meter length of reef requires approximately 50W of power, with a peak current of 10A. The system must be able to change its voltage and current delivery rapidly under ever-changing conditions.
To achieve this precision, CCell uses Vicor Corporation’s patented Factorized Power Architecture (FPA), which meets the project’s power delivery needs while achieving the high current density that allows CCell to minimize the size of the power system deployed in the ocean. The FPA incorporates a PRM (Pre-Regulation Module) buck-boost voltage regulator that operates over a wide input-voltage range with high efficiency and power density, and can be easily paralleled for higher power. It also uses a VTM (Voltage Transformation Module) current multiplier with a fast transient response.
“Vicor’s support was exceptional,” said Bateman. “For example, in the early stages of development, one of their engineers arrived on site fully-equipped to help us solve an issue related to EMI signals reaching the digital side of a Vicor module.”
Field experience with the Vicor modules
The pilot project in Cancun has now been running for over six months, with three reef units under trial plus a control unit. During this time, CCell has found that the Vicor modules have been instrumental in achieving the accuracy and reliability of the voltage and current control.
“Knowing exactly what energy you have put into each aspect of the reef is crucial to understanding the causal factors, and to support repeatability within tests,” said Bateman. “Across our full-scale first pilot in Cancun, we can now independently power each section of the reef and explore different power strategies.”
Cultivating underwater ecosystems using AI to attract more sea life to the reefs
Future innovations include loudspeakers to make ‘reef sounds’ that attract fish, and low-baud-rate cameras to monitor fish populations – backed by AI techniques to identify fish species and other objects. CCell is also designing an underwater electric plug that will allow additional sensors or electric lighting to be easily added.
CCell currently has 50 control units installed along 120 meters of reef, with wave attenuation targeted to approach 30 percent over the next year. The 120-meter reef may be extended, while the company has agreements to install a further 1km of reef along the Yucatan coast.
Research shows that globally wave energy is growing by 0.41 percent per year due to ocean warming. If reefs can be created that reduce the energy of waves by five to eight percent, it would be possible to revert the impact of recent climate change, restoring the near-shore wave climate to levels seen nearly 20 years ago. As a result, coastline erosion would be slowed or even reversed.