Researchers: Recycle CO2 in Floating Methanol Power Plants

Huge floating solar, methanol islands on the ocean could produce enough energy to enable CO2-neutral global freight traffic, says a group of researchers.

The idea comes from researchers from ETH Zurich, the Paul Scherrer Institute, Empa, the Universities of Zurich and Bern and the Norwegian University of Science and Technology.

The islands could be set up in the middle of the ocean to use hydrogen produced from solar energy (and water) and convert it into methanol using CO2 extracted from the seawater. Liquid methanol and gaseous methane could then be produced from carbon dioxide and hydrogen. 

There are already large-scale power-to-gas plants that convert hydrogen and CO2 into fuel. The question therefore arises: why go to sea with it? Why not, as existing plants do, extract CO2 from the air? The researchers estimate that the space required for a worldwide supply of fuel would be enormous. "An area of around 170,000 square kilometers would be needed to produce the annual demand for global freight transport," explains Andreas Borgschulte of Empa's Advanced Analytical Technologies lab. This could best be achieved by solar power systems at sea. CO2 can also be extracted from the air at sea, but an attractive alternative would be to use the roughly 125 times higher CO2 concentration of seawater.

In existing plants, the CO2 extracted from the atmosphere is mostly used to produce methane, which would also be possible on the solar islands. However, the researchers believe liquid fuel would be easier to transport. Additionally, methanol can be used as a fuel and also to manufacture other chemical products, such as precursors for polymer production. The possibilities for its use (and the profits that can be achieved with it) are therefore much greater.

The researchers estimate that the construction of a methanol island at sea would cost around $90 million. It would consist of around 70 photovoltaic islands with a diameter of around 100 square meters and a ship with the electrolysis and synthesis plants, giving a total area of around 550,000 square meters. 170,000 such islands would be needed to recycle as much CO2 as is currently emitted.