We hear about it more and more. Hydrogen. The fuel of the future. The hydrogen economy. But what is it and why are people getting excited?
When we think about it, fuels have been very useful ever since fire was invented. They burn and release large quantities of heat on demand. We can move them to where we want to use them fairly easily. Much of our technological progress has been achieved with the help of fuels. Since the industrial revolution the bulk of fuels used have been fossil carbon-based fuels: coal, oil and natural gas. When these carbon-based fuels burn they release carbon dioxide. But unlike burning wood in the past, the carbon from the carbon dioxide entering the atmosphere is from millions of years ago when the earth was a very different place. So by releasing huge quantities of fossil carbon into our atmosphere we have changed its composition, and done so in an extraordinarily short space of time – a sort of destabilizing hammer blow to our atmosphere.
So the search has been on for fuels that don’t release carbon dioxide into the air.
One fuel that doesn’t release carbon dioxide is hydrogen. When hydrogen burns in air it releases water only. The problem is that there is not much naturally occurring hydrogen gas on the planet for us to tap into. But there are lots of compounds that contain hydrogen. The most obvious one is water. Water is made from two hydrogen atoms and one oxygen atom bound together. Splitting water is most easily done by electrolysis, when we pass electricity into a vat of water and collect the gases bubbling off the electrodes (one being hydrogen gas and the other being oxygen). We need to provide a larger quantity of electricity than we get heat out when it is burnt. So hydrogen is a very useful carrier of energy, but it is not the source of energy. For the source of energy we must look to electricity. And it would defeat the point if we generated electricity for clean hydrogen from burning fossil fuels. So we must use an electricity source that does not emit carbon dioxide such as renewable energy.
The Climate Change Committee (CCC) produced a Sixth Carbon Budget including a projection on the growth of hydrogen as a fuel. It is copied here because it shows the expected ramp-up in hydrogen supply to meet the needs of the UK. The presentation from which it comes is worth a quick look if you are interested in hydrogen.
So it looks like the hydrogen economy will really start to be noticed in about 2025 and is projected to accelerate through the 2030s. So much so that our ability to produce it using low carbon electricity via electrolysis will need to be supplemented by other means.
To compare burning hydrogen for domestic heating with using a heat pump for domestic heating click here. This is an educational resource that can be copied and adapted by teachers and anyone else interested in the science.