Saturday, 25 August 2012

Natural gas fuel cells – the natural green solution

I have been pondering the use of solar cells, wind generators and tidal generators for some time; each renewable energy source usually fails to produce sufficient energy when and where it’s needed. How can we store the energy produced when it’s in plentiful supply and use it later in peak demand time. The often rolled out solution is to pump water into a dam and use the stored water to generate electricity, this is known as pumped-storage electricity and accounts for 99% of bulk storage at the time of writing. This method assumes a lot of water is available which may not be true in Australia’s arid and semi-arid environment. Small renewable energy generators use batteries for base-line storage, but this is expensive and high maintenance.

A smarter way is to use the electricity produced to make the gasses hydrogen and oxygen from saline water using electrolysis, and store the hydrogen for later use. Saline water is easily obtained from the sea or saline aquifers. Hydrogen is notoriously difficult to store and pipe long distances as it tends to destroy the pipes and storage containers. Whereas oxygen is a by-product from this point of view there are many uses for oxygen.

There is a way to convert hydrogen into the easily transportable methane gas using just hydrogen, carbon dioxide and heat. The most promising method at the moment is the Sabatier process which produces methane and potable water. The Sabatier process has been touted as an efficient way of converting carbon dioxide to a useful product instead of trying to sequester it in a potentially dangerous manner.

Natural gas is mainly methane and has been used in Australia and other countries for more than 100 years. The gas is also produced from sewage treatment plants in copious amounts, and some livestock farms use the methane from animal manure to generate electricity for the farm.

The reticulation of natural gas predates electricity, is widespread in Australia and other developed countries and provides the necessary infrastructure for distribution. It can be argued that the reticulation of gas is safer than the reticulation of electricity based on the deaths and injuries caused by both.

Electricity generating fuel cells using natural gas have been in production and use around the world for several years, and an Australian firm ‘Ceramic Fuel Cells’ have produced a Solid Oxide Fuel Cell (SOFC) technology to generate efficient, low-emission electricity from widely available natural gas and renewable fuels. The domestic version, about the size of a washing machine, produces sufficient electricity for a large house and heat for 200 litres of hot water per day. The fuel cell can run for 10 days on one domestic gas cylinder if piped gas is not available.

Ausgrid is leading a $100 million Australian Government initiative called ‘Smart Grid Smart City’ across five sites in New South Wales to test alternative forms of electricity supply. Fuel cells powered by natural gas are being tested in this programme.

Fuel cells are expensive at the moment, but high demand tends to create cheaper more efficient cells as manufacturers compete for market share.

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