As part of our Renewable Energy workshop today, I was asked why we can’t use the steam produced by the evaporation of liquid nitrogen to power a turbine and generate electricity. The short answer is economics –the amount of energy that would be produced by using liquid nitrogen to power a turbine would be less than was consumed to make the liquid nitrogen and keep it cold (it boils at -196 C). This is negative energy production, and doesn’t really make much sense, particularly in a world where we need to reduce our overall energy consumption. As such, when researching alternative methods of energy production, scientists need to consider the amount of energy that needs to be consumed for another form of energy to be produced.

If you think about it, you can trace all energy back to the sun. Energy can get changed to different forms, for example solar energy from the sun is converted to stored energy in food. When we eat food, we can then store this energy which is then expended by our bodies. Fossil fuels are a form of stored energy and were formed over millions of years from compressed organic matter, which would have required solar energy to grow. When we burn fossil fuels, we produce heat energy which we can convert into electrical energy which we use to power our homes and cars, among many other things. The energy that we use for electricity can be produced from renewable (including solar, hydroelectric and wind energy) and non-renewable sources (fossil fuels and uranium). Efficient sources allow for the generation of lots of energy with little energy input with few side products.

Our current sources of energy have advantages and disadvantages. Fossil fuels for example, can be used to generate lots of energy, but burning it produces carbon dioxide, a greenhouse gas which contributes to an enhanced greenhouse effect. Nuclear power can produce incredible amounts of energy from relatively small amounts of fuel, but there are big problems with disposing used radioactive fuel. Solar energy is a renewable source, but up until recently, the amount of energy produced was dwarfed by the amount of energy used in the manufacturing and maintenance of the equipment used to capture it.

Many people don’t think about the big picture when considering sources of energy. Electric cars don’t use petrol and don’t produce carbon dioxide, but if the battery in that car is charged using electricity that was produced by coal (I live in NSW, where 80% of electrical energy is produced from coal)– there is still carbon dioxide being produced, and so there is no real benefit. Hydrogen fuelled cars produce only water as a product, but the energy consumed in the production and storage of the hydrogen fuel again outweighs the amount that can be generated from it. Biofuels are renewable, but burning them produces carbon dioxide, just like the burning of fossil fuels.

There is a great deal of research into methods of producing energy sources like hydrogen to make them a more viable alternative – but there is still a long way to go. In the meantime, reducing energy consumption through cutting back on unnecessary car trips and turning off electronics that aren’t in use is a step in the right direction.

Bye for now!

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