Nowadays, most of the energy we use comes from fossil fuels such as oil, natural gas and coal. Fossil fuels are non-renewable and will eventually run out because we are using them much faster than they can be restored within the earth. Furthermore fossil fuel use has tremendous impact on the world ecology and global climate. Burning fossil fuels generates greenhouse gases and relying on them for energy generation is unsustainable. Hence the need to find more renewable, sustainable ways of generating energy.