Huge arrays of solar panels floating in calm seas near the equator could provide unlimited solar energy for the densely populated countries of Southeast Asia and West Africa.
Our new research shows that marine solar energy can generate around 35,000 kWh of solar energy per year in Indonesia alone, which is equivalent to current global electricity production (30,000 TWh per year).
And while most of the world's oceans experience storms, some areas at the equator are relatively calm and peaceful. Therefore, relatively inexpensive engineering structures may be sufficient to protect floating marine solar arrays.
Our high-resolution global heat maps show that the Indonesian islands off the coast of Nigeria and equatorial West Africa have the greatest potential for ocean-floating solar panels.
Solar energy has been regulated since the middle of this century
According to current trends, the global economy will be largely decarbonized and electrified by 2050, powered by massive amounts of solar and wind energy.
About 70 square kilometers of solar panels can meet all the energy needs of a million rich people in a carbon-free economy. Panels can be placed on roofs, in dry areas, on farms or floating in bodies of water.
But in densely populated countries like Nigeria and Indonesia, space to collect solar energy will be limited.
Their tropical location also means that wind sources are rare in so-called "calm" latitudes. Fortunately, these countries - and their neighbors - can effectively harness the boundless energy of solar panels floating in calm equatorial seas.
Floating solar panels can also be placed in inland lakes and reservoirs. Domestic solar flotation has great potential and is already developing rapidly.
Our newly published work surveyed the world's oceans to find areas that had not experienced large waves or strong winds in the past 40 years. Floating solar panels in such a region do not require robust and expensive engineering protection.
Areas with waves higher than 6 meters or winds of less than 15 meters per second can generate one million TWh per year. That's five times more energy than is needed for a completely carbon-free global economy that supports 10 billion wealthy people each year.
Most of the good sites are near the equator, in and around Indonesia and West Equatorial Africa. It is an area with high population growth and high ecological value. Offshore solar panels can help resolve land use conflicts.
Indonesia has great solar energy potential
Indonesia is a country with a high population density, especially on the islands of Java, Bali and Sumatra. By the middle of this century, Indonesia's population could exceed 315 million people.
Fortunately, Indonesia has great potential for solar energy, as well as great potential for hydroelectric storage with pumped storage for solar energy overnight.
Around 25,000 square kilometers of solar panels will be needed to sustain a wealthy Indonesia after completely decarbonizing its solar-powered economy.
Indonesia has the potential to deploy large numbers of solar panels in calm inland seas. The region has a seascape of 140,000 square kilometers that has never been hit by a wave of more than 4m - even with strong winds of 10m per second - in the last 40 years.
Indonesia's sea area of 6.4 million square kilometers is 200 times larger than needed if all of Indonesia's future energy needs are met by offshore floating solar panels.
The future of solar energy is floating in the ocean
Most of the world's seascapes have waves over 10 meters high and wind speeds greater than 20 meters per second. Several companies are working to engineer the shelters to make floating marine panels storm-resistant. In contrast, the favorable marine environment along the equator requires stronger and more expensive protection.
The most suitable areas are concentrated between 5 and 12 degrees latitude, mainly in the Indonesian archipelago and in the Gulf of Guinea near Nigeria. This region has low wind generation potential, high population density, rapid growth (both in population and energy consumption), and a very, very large ecosystem that does not need to be restored for solar power generation. Tropical storms rarely affect equatorial regions.
The marine floating solar industry is still in its infancy. Offshore solar panels have disadvantages compared to onshore panels, including salt corrosion and ocean pollution. Shallow waters are preferred for anchoring panels to the seabed. And great care must be taken to minimize damage to the marine environment and fisheries. Global warming can also change wind and wave patterns.
Despite these challenges, we believe that floating offshore panels will become an important component of the energy mix for countries with access to calm equatorial seas. By mid-century, around one billion people in these countries will depend primarily on solar energy, leading to the fastest energy transition in history. 
Andrew Blakers , Professor of Mechanical Engineering, Australian National University and David Fernando Silalahi, PhD, School of Engineering, Australian National University
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