Technology Idea of the Week

This week: is there a future for methane fuel cells? Methane hydrates have featured quite a lot recently while I researched for my posts on Arctic natural resources and in Anson Mackay's lecture on the crysosphere. It seemed deserving as this weeks technology focus!

Fuel Cells - A very brief introduction! 

• Convert chemical energy into electricity by an oxidising reaction
• Require a constant fuel supply 
• The ideal fuel is hydrogen because it doesn't produce greenhouse gases but the technological challenges in its cost and storage mean this currently not viable (Steele, 1999, Nature)
• Currently, the best fuel options are hydrocarbons (methane) and alcohols (methanol).  

Methane Hydrates

• Methane hydrates (clathrate) are crystalline solids composed of a mixture of water and light natural gas (methane, carbon dioxide, ethane). They are found in the shallow lithosphere (<2000m deep) where the surface temperature is less than 0 °C (Kvenvolden, 1993, Review of Geophysics)
• There are substantial natural deposits of methane hydrates in deep ocean sediments, permafrost and under frozen lakes. It is estimated that the global volume of methane hydrate is 10¹⁵ to 10¹⁷ cubic metres of methane which represents 53% of all fossil fuels ((Demiras, 2010, Energy Conservation and Management). The distribution of organic carbon can be seen in the image below. 

Distribution of organic carbon on earth (excluding kerogen and bitumen).
Source: Demiras, 2010, Energy Convservation and Management)

Advantages of Methane Fuel Cells

• Substantial deposits - it is estimated that the global volume of methane hydrate is 10¹⁵ to 10¹⁷ cubic metres. Deposits are found in widespread geographical locations including US permafrost, Lake Baikal in Siberia and Arctic sediments. (Demiras, 2010, Energy Conservation and Management)
• Low carbon energy - methane is a less carbon intensive fuel than coal or oil: it produces approximately half the amount of CO2 than coal for equivalent volumes. This can be seen the equation below. Therefore using methane hydrates as an energy source could help reduce anthropogenic emissions of carbon dioxide which may contribute to the greenhouse effect. 

Top equation - the combustion of coal. Lower equation - the combustion of methane hydrate
Source: Demiras, 2010, Energy Convservation and Management)

The Challenging side of Methane Fuel Cells

• Location and access - finding the deposits requires high level seismic imaging, we do not have detailed enough resolution for some deposits. In addition the deposits often cross national boundaries or are in international territories. This raises a lot of geopolitical issues in terms of researching the site and rights over the resources. (Kvenvolden, 1993, Review of Geophysics)
• Extraction - the gas can expand 160 times its volume as it is brought to the surface and is de-pressurised. This can cause explosions and leaks of methane gas (CH4) which contributes to the greenhouse effect. We currently need to do further research into drilling technology to ensure safe extraction of methane hydrates. (Demiras, 2010, Energy Convservation and Management)

It is possible...

In March of 2013, a Japanese drilling company successfully produced gas from frozen methane hydrates from the ocean floor. For equal volumes, this deposit holds 164 times the energy of conventional gas (NewScientist, 2013). The deposit is in the Nankai trough and could be a game changer for Japan's energy supply. Investigation into methane hydrates was fast tracked by the Japanese government after the Fukushima nuclear power disaster. Here is a film of the methane hydrate extraction in Wellington by a team of German Scientists (the video is in English)! 

In conclusion, methane hydrates could be a really important step in meeting our energy needs over the next 100 years. The ultimate goal still remains as the production of commercially viable hydrogen fuel cells. 

Technology Idea of the Week

Technological developments help determine the future of energy sources so I have decided to introduce a new feature in my blog: Technological Idea of the Week! Some of the ideas maybe in the start up stage, some of them maybe more in the creative stage! This will help to examine some of the new players in the energy market alongside the giants such as oil and nuclear power.

The Solar Chimney 

For my first edition in this series I am going to look at a project that takes a new approach to solar and wind power. What is particularly unique about this project is the way it combines different renewable technologies to help improve reliability and maximise power production. 

Image Courtesy of Solar Innovations

The Solar Chimney has two key components: a array of solar cells and a chimney with a turbine at the top. Air is heated at the base by the solar cells and therefore decreases in density and rises up through the chimney. This creates an updraught of air which will propel the turbines at the top of the chimney generating electricity. This can be seen in the diagram below which also demonstrates how this could be attached to houses and utilise pre-existing chimneys.

Image Courtesy of Solar Innovations

This idea has been around since the beginning of the 20th century and an experimental one was constructed in 1982 but then taken down due to concerns over collapse (BBC News, 20th November 2013). However, this idea has suddenly been given life again due the backing of Per Lindstrand who aims to build a 1km (yes 1km) high tower! He is famous for being the first person to cross the Atlantic in a balloon and has funding for this project from the 1851 Royal Commission (The Engineer, 19th November 2013).

Over the last thirty years there has been a lot of research into modelling solar chimneys to try and estimate how effective they can be. The chimney height and turbine head design have the biggest impacts on the efficiency of the solar chimney (Hamdam, Renewable Energy, 2011). Comparison of existing solar chimneys in Spain and Australia have allowed testing of the models to access their validity but there is much more research needed to make sure we use the best design to maximise efficiency (Nizetic et al, Energy Journal, 2008).