Global warming isn’t going away and the effects are becoming more visible. We aim to cut carbon-dioxide emissions by 60% within the next 30 years, limiting global warming to 2 oC, with the intention of being completely emission free by 2050. It sounds like a huge task, but could hydrogen be the clean fuel of the future, helping towards this goal?
Hydrogen is an abundant element but not freely available as a gas, because it likes to bind to other elements (e.g. reacting with oxygen to make water, H2O). When hydrogen is burned no carbon emissions are created and hydrogen is twice as energy efficient as fossil fuels. It is hoped that we will use hydrogen for ~1/5 of the total energy consumed by 2050, cutting carbon emissions by 6 billion tonnes compared to today. How can we make hydrogen if it is usually found as part of a compound (i.e. more than one element, H2O)? All of these methods involve splitting a compound into it’s basic elements to produce hydrogen:
- Steam reforming methane: this method produces carbon emissions but they’re ~25-35% lower than burning diesel (not the final product, but a good start!).
- Electrolysing water: produces pure hydrogen but is less efficient and more costly than steam reforming. It is possible to use this to convert surplus solar and wind energy to hydrogen.
- Converting natural gas to hydrogen: a research group at the University of Western Australia have developed a catalyst which can do just this. Carbon is created in the process but it’s captured as graphite and subsequently used in lithium-ion batteries.
- Using energy from the sun to split water (producing hydrogen): researchers at the University of Exeter have found a way of capturing hydrogen from water.
So now we have hydrogen, how do we store it? There are 3 main ways currently used to store hydrogen: (1) as a compressed gas (in high-pressure tanks), (2) as liquid (in tanks at -253oC!) or, (3) as a solid (absorbed into materials, or reacted with other elements). Currently, the storage of hydrogen is difficult and costly. There are global efforts attempting to improve efficiency and cost of production, storage, transportation and the use of hydrogen in applications from heating to transport. However, for hydrogen to be used in our everyday lives, this would require an overhaul of current energy systems (e.g. power grids, fuel stations, central heating etc.).
Over 30% of the UK’s emissions come from our heating network. How easy would it be to use hydrogen in the future? Traditional iron pipes are now being changed for polyethylene ones which can carry hydrogen. Keele University aims to test this process by mixing natural gas with hydrogen (up to 20%) and then using it in the campus heating network by spring 2019, beginning to reduce carbon emissions. A hydrogen mixture such as this would cut CO2 emissions by 6 million tonnes per year if used across the UK; the same as taking 2.7 million cars off the road. Research is underway to see if the current system could support more than a 20% mix.
Is hydrogen already being used? Japan is using the 2020 Tokyo Olympics to showcase their hydrogen developments. Japanese car manufacturers (like Toyota) are building hydrogen fuel cell vehicles, homes are fitted with fuel cell technology to provide electricity, and the building of power plants is underway to make hydrogen using renewable energy. The following is a short video from Toyota, detailing their hydrogen fuelled car, Mirai, and it explains the process very well.
What is a fuel cell? A fuel cell is a hydrogen-oxygen fuelled, proton-exchange membrane (PEM) fuel cell. Hold on. They have been used for various applications since 1955, including by NASA in the 1960’s for the Gemini project. A fuel cell is a device which generates electricity through chemical reactions (much like a standard battery, see our previous post detailing batteries here). The reaction combines hydrogen and oxygen to generate water and energy in the form of electricity. Yes, that’s right, a car powered by a hydrogen fuel cell will generate water, not carbon emissions. Pretty impressive. Here is a link to one of the most recent hydrogen fuel cell powered cars by Hyundai: Nexo.
Industry already uses 55 million tonnes of hydrogen per year as a feedstock, and in many cases hydrogen is a by-product of processes. Hydrogen fuel cells are better for emissions, range and charging time than electric cars, taking only a few minutes to fill and a few hundred miles (~500) before requiring refilling. The water generated by the fuel cells is actually clean enough to drink straight from the tailpipe, but I wouldn’t recommend it. If research can find solutions to the cost and difficulty of production and storage of hydrogen, this could be the fuel of the future, getting us around, heating our homes, providing energy but not contributing to global warming. Wouldn’t that be amazing?