Wednesday, July 24, 2013

Solar methanol and the third industrial revolution

However, the tantalising promise of methanol is that it can be used as a fuel in a fuel cell. Fuel cells can operate at an efficiency of 80 per cent, as against gas-fired steam turbines of 50 per cent, and coal-fired steam turbines of 40 per cent. These are best practice numbers; many Chinese coal-fired steam turbines are much less efficient than 40 per cent.The Hydrogen Economy has often been touted as the next big energy source. However, due to the prohibitive cost of its infrastructure, hydrogen has gone out of favour. Fairly recently, Professor George Olah, Nobel Laureate, has proposed using methanol (think methylated spirits). Methanol is a liquid at room temperature, it can be used in the pre-existing gasoline infrastructure and, unlike LNG, it can be transported by ordinary oil tanker.
Because the fuel cell stack can be located close to the consumer, the 20 per cent “cogenerated” waste heat can be ducted to the consumer (for space heating) along with the electricity, resulting in 100 per cent fuel efficiency.
The ideal fuel cell for methanol will consume the methanol directly and not need a (steam reformation) unit at its front end to preconvert the methanol into hydrogen and carbon dioxide.
Up to now, two fuel cell types seem to have emerged from the scrum, the solid polymer and the solid oxide. Both of these have crippling disadvantages.
Firstly, the solid polymer cell. The proton-exchange “nafion” polymer membrane fuel cell uses platinum. End of story! Also, platinum catalysts are prima donnas. They hate carbon dioxide. Even the tiniest amount of carbon dioxide that escapes the hydrogen scrubber will convert to carbon monoxide and “poison” the platinum. Methanol will “cross over” the electrolyte and combine with the oxygen directly, without forming an external circuit. This greatly reduces the output current.
Secondly, the Solid Oxide Cell (SOFC). The SOFC operates at 1000°C, continuously. It can use methanol, but it is so costly!
However … a couple of days ago, a South Korean research team at the Ulsan National Institute of Science and Technology has disclosed a cheap, iodine coated graphene-based direct methanol fuel cell. They have reported that this fuel cell generates 33% more current than platinum, is unaffected by carbon monoxide, and does not display “methanol cross-over”. If it can be commercialised, this fuel cell could be the holy grail that will usher in Olah’s “Methanol Economy.”
Traditionally, methanol has been produced by the steam reformation of natural gas. However, there is another pathway. If carbon dioxide and hydrogen are processed in the presence of a copper/zinc oxide/ alumina catalyst, the result is satisfactory levels of methanol and water.

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