Why Solar: Fertilizer and fuel

  • Thu May 25th, 2017 12:30am
  • Life

Anhydrous ammonia is a fertilizer in common use around the world; in 2014 some 176 million tonnes was produced, 88 per cent of which is used for crop production.

Here in Alberta, spring brings the sight of the long white tanks towed behind cultivators as grain farmers prep their fields for planting. Large storage tanks dot the rural landscape to provide nurse trucks with product.

Anhydrous means without water and the fertilizers chemical formula is NH3, three atoms of hydrogen bonded to one of nitrogen. It is these atoms of hydrogen that has inspired science as a medium of power since it was identified by Claude Louis Berthollet 230-odd years ago. However, with only one third the energy density of diesel fuel, fertilizer is the preferred use.

Noteworthy attempts for use of ammonia as a motive fuel go back as far as 1870 in a street car in New Orleans, and 36 years ago a Canadian company converted a Chevy Impala to run on ammonia.

With its high hydrogen content, and lack of any carbon, NH3 proffers a means for uncomplicated transport of hydrogen. Normally H2 has to be either highly pressurized, or stored as a cryogenic liquid at -423 F. However when it comes to use as a fuel, both means of storage have range and ease of handling issues. These issues make it difficult for hydrogen to compete with the current use of petroleum products. Considering the range a tank of petrol gives a vehicle, that convenience becomes almost unbeatable.

However with carbon taxes and global warming concerns, the current concerns with petroleum are ever present. Pure hydrogen when used as a fuel provides an answer to contemporary environmental problems, but the safe and convenient transport in a vehicle quandary needs to be addressed.

Enter CSIRO; the Commonwealth Scientific and Industrial Research Organization, in Australia, is developing a “metallic membrane” that will convert ammonia into “high-purity hydrogen.” This conversion process of high-purity hydrogen is perfect for use in vehicles as anhydrous ammonia can be transported in low pressure tanks due to its low vapour pressure of 93 psi at 60 F, (641 kPa).

To convert the “hydrogen/ ammonia mix” the scientists force a pressurized stream of NH3 through this metallic membrane which permits the smaller hydrogen molecules through but stops the nitrogen molecule.

This solution for harvesting the ecologically friendly hydrogen for use in fuel cells or combustion engines provides an answer to the handling and transportation conundrum. Infrastructure is already in place for production, storage and handling, of ammonia, although a major increase in production is required.

Australia plans on becoming a major hydrogen producer, supplying the world as it transitions from a fossil fuel economy.

As anhydrous ammonia is produced from ambient air with its 78 per cent nitrogen content and natural gas as the main source for the hydrogen, it is easy to see that Alberta industry would also benefit from this need for hydrogen as an alternative.

Why should Australia have all the fun?

Find Lorne Oja at lorne@solartechnical.ca


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