Dan standing next to a cloud brightening machine
Dan Virah-Sawmy and a cloud brightening machine aboard a boat on the Great Barrier Reef

6 July 2023

By Sarah Wilson

Imagine shading the waters of the Great Barrier Reef by enhancing the cloud cover above it. Sounds like science fiction, right? In a world first implementation project, a team of experts is demonstrating a novel technique in an attempt to cool down the Great Barrier Reef and mitigate the effect of climate change. PhD student and ANU Three Minute Thesis finalist, 2023, Dan Virah-Sawmy, explains ‘cloud brightening’ and how his research is helping buy time for the planet’s largest living structure.

“Any sufficiently advanced technology is indistinguishable from magic.” This quote, by science fiction author Arthur C. Clarke, danced around my head as I listened to Dan chat about his compelling PhD project.

Originally from Mauritius, an island off the south east coast of Madagascar, Dan arrived in Australia 2018 to study an undergraduate degree in mechatronics engineering at Deakin University in Geelong, Victoria. In 2022 after completing his degree he accepted an offer to begin a PhD project looking at renewable energy solutions for the Great Barrier Reef, based within the Battery Storage and Grid Integration Program at ANU.

“When I was at high school, I didn’t want to go to university,” said Dan. “I wanted to be a pilot but I have heart arrhythmia, so that put an end to that. My second option was university. I knew I wanted to go overseas, but not to Europe or North America. I decided to come to Australia to study engineering.

Dan recently won the College of Engineering, Computing and Cybernetics’s Three Minute Thesis challenge, also taking out the People’s Choice Award from the audience vote for his enchanting tale on clean energy solutions for the Great Barrier Reef.

It is no exaggeration to say that the reef is facing catastrophic decline. Since 2016 the reef has experienced three mass coral bleaching events in five years due to high sea temperatures caused by climate change. World Heritage Listed, the reef is one of the seven natural wonders of the world. It is the size of Italy and contains the world’s most extensive coral reef ecosystem that is home to 3,000 individual reefs, 1000 islands, 1600 fish species 240 bird species, 6,000 mollusc species and 600 coral species. Incredibly rich in biodiversity, the importance of the Great Barrier Reef cannot be overstated.

The benefits of the reef are not only environmental, it is also of tremendous importance economically, contributing more than six billion dollars a year through tourism and fishing and supporting an estimated 64,000 jobs in Australia.

Dan’s PhD project is part of the Reef Restoration & Adaptation Program – a collaboration of Australia’s leading experts who are creating a suite of innovative and targeted measures to help preserve and restore the reef, with expertise in ecology, water and land management, engineering, innovation and social sciences.

One of the subprograms is investigating technologies to cool and shade the reef to prevent or reduce bleaching stress on coral reefs by reducing the amount of sunlight reaching the reef. Cooling by cloud brightening is the project Dan is working on, specifically looking at ways to use renewable energy to power the cloud brightening technology.

“Cloud brightening could potentially protect the entire Great Barrier Reef from coral bleaching in a relatively cost-effective way, buying precious time for longer-term climate change mitigation to lower the stress on this irreplaceable ecosystem,” said Dr Harrison, Dan’s co supervisor from Southern Cross University.

Cloud bright technology essentially consists of machines that spray a fine mist of sea water into low lying clouds. The water evaporates off leaving nano-sized sea salt crystals, or aerosols, that combine with the clouds and brighten them, deflecting sunlight away from the reef’s waters, helping to cool it.

As luck would have it, conditions on the Great Barrier Reef are just right for this approach to work and early results are showing promise. Shading the reef does however require a large logistical effort and whilst there has been a lot of theory carried out over the past 30 years this is a world-first implementation.

Dan has been investigating ways to provide clean energy and storage, to power the sea spray machines and replace diesel generators. Dan researched solar, wind, wave, tidal and ocean thermal energy and the impact these forms of renewable energy could have upon the reef’s delicate ecosystem. 

“We cannot explicitly say what would be the environmental impact of renewable energy deployment on the reef, however, the literature does warn us and provides advice,” says Dan.

“Wind turbines, for example could have a dramatic effect on birds. Wave, tidal and ocean thermal are not readily available on the reef and the technologies are not sufficiently mature.

“Solar energy was found to be the safest technology but it needs to be supplemented with some form of energy storage for increased reliability,” said Dan.

To shade the entire reef, Dan is working on the premise of a network of approximately 800 machines. The machines would operate several hours per day during Australia’s summer, January to March, when the sea temperatures are the highest. The machines could be installed on boats or barges, equipped with high efficiency solar panels.

The specific challenges inherent in this project include remoteness, with the reef located approximately 50 to 100 km from shore, limited space and a fragile ecosystem. The amount of weight that the barges can support is limited which means that a system solely reliant on batteries was not feasible. And due to remoteness and fragility of the reef, laying cables is not an option.

To complement the production of solar energy, was the need to find some form of storage. “Batteries weigh too much on boats and barges,” said Dan. “Hydrogen as energy storage reduces weight on the boat.” Dan’s comparative research revealed hydrogen to be the number one choice for energy storage.

“The challenge with hydrogen production is how to produce it cleanly,” said Dan. “Currently 96 per cent of hydrogen is produced from fossil fuels. We aim to produce clean hydrogen only, using electrolysis, either onshore or offshore and store it as a compressed gas. There are limitations however, hydrogen production has a high energy loss rate (as much at 85 per cent). The efficiency of electrolysers is in the range of 60 – 80 per cent and the efficiency of hydrogen fuel cells are in the range of 40 – 60 per cent.

The broader applications of hydrogen production, and what that could mean for Australia’s electricity grids are something that supervisor Dr Bjorn Sturmberg is interested in learning more about.

In a warming world cloud brightening is sure to be of interest on a global scale, possibly with many applications. On the Great Barrier Reef, if the technology is implemented, it would be a temporary protective measure to help build the resilience of this important ecosystem.

Meanwhile, further south on Australia’s mainland, Dan is content with his life in Canberra. “ANU campus life is very multicultural. I have friends from around the world; Mexico, Brazil, Portugal. I am also enjoying the ANU environment, the wildlife, the ducks and possums. ANU has charm, it is so beautiful and lively walking on campus,” said Dan.

As the winner of our College round, Dan will go on to represent CECC in the ANU 3MT final in Llewellyn Hall on 27 July. Book tickets to join in person or register to watch the livestream. The winner of the #ANU3MT final will then compete in the Asia Pacific final, held at the University of Queensland.  He will now represent the College in the University finals later this month.

Dan’s ANU supervisors are Dr Bjorn Sturmberg, Battery Storage and Grid Integration Program, and Dr Fiona Beck, School of Engineering.