Hydrogen: What's it All About?

UCell’s Josh Bailey talks all things hydrogen and hints that it may not all be as dangerous as you may think…These days, with climate change and local air pollution filling our media, it’s easy to feel like we are losing control of our environment. Fortunately, there is, and has been for a while, a growing trend towards renewable energy deployment. In fact, off the back of the Paris Agreement in December 2015, there are more and more initiatives globally working towards a sustainable future [at the time of writing, the US President announced withdrawal from this agreement, however this process may take up to four years and is thought to perhaps promote tighter-knit collaboration of the other 194 countries involved].With this change of direction, there is a growing need for energy storage to capitalise on intermittent renewable sources, to smooth spikes and troughs and to allow for the sharing out of this new green power to everyone. Other than batteries and capacitors, fuel cells are quickly surging forward to offer a variety of advantages, from fuel flexibility, through high energy efficiency, to low emissions at the point of (very quiet!) use. So, what are they?Well, fuel cells are kind of a hybrid between batteries and combustion engines – they require a fuel and oxidant, but they don’t burn/combust anything. Instead, they house very safe, isolated electrochemical reactions that occur inside, generating electricity, heat and water. Yes, H2O is the by-product, no filthy nitrogen oxides (NOx), sulfur oxides (SOx) or that infamous CO2! This is exactly why hydrogen is proving to be an important part of the electrification of transport, reducing the harmful airborne substances found in all major cities at increasingly alarming quantities.Fuel cells, although originally invented back in 1839 by Sir William Grove (from Swansea), are not nearly as well-known as batteries. This is for a number of historic, technical and political reasons but this is starting to change with the advent of fuel cell electric vehicles (FCEVs) like the Toyota Mirai, Hyundai ix35 FCEV and Honda Clarity, to name the few already selling globally. There’s even a bus route (RV1) running in London between Covent Garden and Tower Gateway that is furnished with its very own hydrogen-powered fleet. Keep an eye out for it if you’re about the capital!So why is this technology not even more widespread? And wait, did you say “hydrogen”, isn’t that dangerous? Well the answer to the first question inevitably involves the public perception of the answer to the second, at least partly. The truth is, hydrogen can very much be dangerous, but so can gasoline, diesel, liquid petroleum gas, kerosene – you name it, fuels that we put in our cars and planes can cause problems if they’re not handled properly – they’re energy dense. This is the first point that I aim to explain to public audiences when talking about the advances towards a ‘hydrogen economy’ when working with UCell at events and festivals. Err… “what’s this UCell?” I hear you ask…UCell – UCL Fuel Cells, is a collaborative project promoting sustainable energy devices and research conducted at the Electrochemical Innovation Lab (EIL) at University College London (UCL). We have given talks and demonstrations at universities including Oxford and Cambridge, exhibited our 3 kW fuel cell stack at racing events and music festivals and have even recently been involved with the Royal Institution Christmas lectures and family day events. Find out more about us here.The second thing relating to safety that is worth considering is that we have got much better over the years at using pressurised vessels such as gas cylinders and coming up with sensible protocols regarding hazardous gas use. In fact, the Toyota Mirai houses two 700 bar (that’s approximately 700 times ambient pressure!) hydrogen gas cylinders which can be refilled in a matter of minutes! For more information about how Toyota Mirai maintains such high standards of safety, read this blog. We have also come a long way in terms of other storage methods, such as storing hydrogen as metal hydrides, yes that’s right, in solids! Work is continuing around the world to produce evermore energy-efficient and safe ways to store hydrogen as a solid.The added problem when dealing with hydrogen gas, as opposed to the other fuels, is that it has wide flammability/explosive limits, so there is a wider window, in terms of its concentration in air (4 – 75 %), in which it could catch light. However, the truth is that there are many reasons why you shouldn’t be so fearful. One of the main reasons is that hydrogen, being the lightest element in the universe, has a very high diffusivity. This means it very quickly diffuses (upwards), dropping below the lower limit, and doesn’t pool on the ground like say, petrol. It is only if this gas is trapped in an enclosure as it rises that it can potentially be a problem, albeit requiring some sort of ignition as well. To see what is rare for any type of vehicle, but how a gasoline and hydrogen vehicle compare when fuel escapes and is ignited, take a look here.Other issues that hydrogen has faced and continues to face include production, storage and distribution. For a start, it’s a bit of a chicken-egg situation when it comes to overhauling refuelling infrastructure – do you build expensive hydrogen fuelling stations first, or do you opt for a load of the cars first? They are co-dependent, but slowly but surely more and more stations are being opened in the UK, following in the footsteps of the US State of California as well as huge in-roads in Japan. Production has a long way to go before it is truly green; over 90% of hydrogen is “brown” and currently produced from fossil fuels, the majority from a process known as steam methane reforming. Although this is not going to provide the truly sustainable hydrogen economy that is envisioned, the current set-up is at least taking the products of combustion off our streets and localising them in power production plants. In fact, although slow at current, carbon capture and storage (CCS) methods, or carbon utilisation schemes can much more easily take advantage of this centralised production than if we continue burning petrol in our vehicles. What we hope to see in the future is an increase of using renewables, such as solar and wind, to produce “green” hydrogen and complete the loop to enable a truly sustainable hydrogen economy.So, although costs remain high, and public understanding the technology is in its infancy, the long-range (500+ km) and short refill time of FCEVs means there are likely to be part of our electrified transport future. And that doesn’t even touch on some of the advantages hydrogen and other fuels can play in unison with fuel cells when it comes to grid-scale storage, combined heat and power in the home and even portable power solutions!