New System Means Methanol Suitable for Submarines

Air-independent propulsion (AIP) represents a technological breakthrough for conventional submarines, but there are limitations to the hydrogen-based fuel cells typically used, and SENER of Spain is working on a project that will see methanol used to generate the hydrogen needed rather than having to store it on board.

In addition to diesel generators that require exterior air for combustion, submarines with an AIP system use energy sources that do not require surface air such as fuel cells. This allows them to be submerged without being detected for much longer than diesel electrical submarines which have to emerge to the surface and operate with a snorkel when their batteries need recharging.

Fuel cell systems currently being used allow the submarines to generate their energy needs from hydrogen and oxygen. However, the hydrogen is stored in heavy bulky cylinders which have a big impact on weight and internal space. 

To solve this problem, and given that the general market trend is to build ever larger submarines, SENER has partnered with ThyssenKrupp Marine Systems to develop an AIP based on a methanol reforming process that allows the hydrogen to be produced on board.

The team has developed a system that Sener says has excellent commercial potential in the submarines market. A key component of the new technology is a CO₂ dissolver for the exhaust gases.

SENER has designed a system that releases the gases outside the submarine, while ensuring that the boat’s acoustic signature is not detectable at a certain distance. To achieve this, SENER has succeeded in dissolving these gases (approximately 98 percent CO₂ and two percent O₂) in sea water by suctioning directly from the submarine at the same pressure as the depth at which the vessel is located. 

In the process’s toughest conditions, SENER achieves a maximum bubble size of 200 μm at a depth of 18m for warm waters. The CO₂ dissolution unit is in the process of being patented in Europe.