Repurposing the world’s massive natural gas network to run on hydrogen could be facilitated by two new membrane technologies, according to Spanish start-up H2Site.

The company last month received $13 million in investment from headline names including Breakthrough Energy Ventures, Engie, and Equinor. The funding aims to accelerate the development of its advanced membrane reactor technology, which can facilitate the transport of hydrogen using larger molecules as well as the separation of high purity hydrogen from gas blends.

“While much focus is given to hydrogen generation cost reduction, less attention is given to reduction of hydrogen transport cost. Transporting hydrogen is a complex task, it being a small molecule that is difficult to contain. The current compression, storage, decompression, and transport solutions are both economically and environmentally inefficient”, says H2Site CEO, Andrés Galnares.

Recent research from Irena has indicated that repurposed pipelines will be between 65% and 94% less costly than building new hydrogen-specific pipelines, largely due to the reduced amount of excavation work that is required. For newer pipes, which are made mostly of steel, repurposing can be achieved in most cases through the addition of new valves to alter the operating pressure.

However, for many existing tanks and pipelines, storing such a small molecule, often at high pressure, can cause cracks that ultimately result in failure.

Then there’s the issue of hydrogen’s energy density; hydrogen has about 30% of the energy content of methane by volume. Transporting hydrogen that is compressed, or liquefied at extremely low temperatures, are among the concepts which are being explored, but it currently remains prohibitively expensive. H2Site has said that transporting hydrogen using such technologies could cost as much as three times the cost of hydrogen production itself.

Blending hydrogen into natural gas pipelines, up to around 30% of volume, H2Site believes that less corrosion will occur.

Used in existing natural gas pipelines that can carry a blend of up to 30% hydrogen, H2Site’s first innovation is a new way of deblending hydrogen on the demand side, using long-lasting double-skin inorganic membranes.

The company uses the ability to carry hydrogen on metals like palladium, which naturally forms a lattice which can absorb large amounts of hydrogen. At key temperature and pressure, the hydrogen will separate from the surface of palladium lattices and these can also be built into a membrane that only lets hydrogen through. The output is hydrogen of up to 99.9% purity extracted from a palladium membrane, which has been fed by a blend of between 5% and 30% hydrogen, mixed with natural gas.

One concern with this blending approach is the low volumetric energy density of hydrogen – 30% blending may only result in a 7% reduction in emissions from the gas that is delivered.

However, H2Site’s technology may be also applied to other types of transport. With hydrogen currently being transported as liquid ammonia and methanol, which are far easier to store at scale than gaseous hydrogen, there is a need to minimize the energy intensity and cost of converting hydrogen into a hydrogen-carrier and back again.

Ammonia is converted back into hydrogen through a process known as cracking, which is where H2Site has tweaked the operation of its palladium membranes. By altering temperatures and increasing the number of membranes, the company has demonstrated reactors that can be used to filter out 40 kilograms of hydrogen per day, with limited energy input.

It plans to scale this technology to commercial units that will be able to handle 200 kilograms of hydrogen from 500 kilograms of ammonia. Eventually, the company believes it will be able to get costs down to around $0.80 per kilogram of hydrogen.

H2Site already has three sites where the technology will be tested in the UK, Spain, and France, all working on slightly different areas of application. The latest round of funding will aim to increase its membrane manufacturing capabilities, operating a world unique membrane manufacturing plant in the North of Spain.

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