Hydrogen as an energy supply
When it comes to storing energy, it need not be stored as electricity, although advances in battery technology mean that is becoming more practical, as we’ll hear later in the programme when we talk about the rising trend towards installing domestic batteries to power our homes. One alternative, attractive energy storage solution is hydrogen. It’s easy to make: you pass the electricity generated from a renewable source into water and use the electrical energy to split the water into hydrogen and oxygen. The hydrogen you can send down pipes, or feed into devices called fuel cells that reverse that reaction and return electricity and water. Physicist Dave Ansell is one of the world’s best science demo developers, so we asked him to show Harry Lewis how this works…
Harry - So Dave, what have we got? What's in front of us?
Dave - I've got two wires, which will be coming from the solar panels effectively. And they're basically just connected to two more wires in some water.
Harry - This is electrolysis, isn't it? That's what we are going to be carrying out?
Dave - Yes. So, what we're doing is we're passing electricity through water. Effectively the way electricity passes through a liquid like water is you actually get ions moving. So you get positive H ions moving one way and negative OH minus ions going the other way. And when the ions reach the negative electrode, which they're attracted to, they will form hydrogen gas. And when the OH minus ions reach the positive electrode they'll form oxygen gas.
Harry - So if we hit the switch on that, are we gonna start that current up or provide that voltage?
Dave - Yeah. We'll hit the switch. And if you look closely...
Harry - Bubbles off both sides.
Dave - Yep. So you can see there's more bubbles being created on the hydrogen side than the oxygen side, because water's H 2 O so you get twice as much hydrogen as oxygen.
Harry - How do we actually know that we have hydrogen and oxygen?
Dave - I'm going to add some soap to the water, which will hopefully mean the bubbles will be more stable and we can mix that in, but we will have to wait for a bit and hopefully collect a pile of bubbles filled with hydrogen and/or oxygen.
Harry - Whilst we've got a little bit of time because the bubbles are forming in our soapy mixture. What would we then use that for?
Dave - So one thing you can actually do in fact with this demo is if you leave the electrodes in there, you can plug it into a volt meter and it will generate a voltage. It's not very stable here. It's not a very good system because you lose the gas, which is stuck onto the wires. But if you can build a proper fuel cell, you can basically produce a battery, which you can recharge by adding hydrogen and oxygen.
Harry - Right. Interesting. And if you weren't to make a fuel cell, is there any other way that we could make use of this hydrogen?
Dave - Well, the simplest thing would be to just burn it so you can put it into the pipes and supplement your natural gas with something more environmentally friendly. However, that seems to me to be a bit of a waste, because there are all sorts of things which you do first, which need hydrogen. Making fertiliser, which is a big issue at the moment, consists of nitrogen gas and hydrogen, which you react together at high pressure to create ammonia. People are talking about smelting iron, using hydrogen instead of carbon, which again would decarbonise another industry.
Harry - So we're bubbled up. Does that mean we're ready to go? What do we do now?
Dave - Light a match.
Harry - Oh that was so much louder than I expected. That was good. Wasn't it?
Dave - That was good. And a squeaky pop, as you learned in school, hydrogen produces a squeaky pop.
Harry - Hydrogen did produce a squeaky pop.
Dave - So that pop has obviously released a load of energy, which we've stored by electrolysing the water. And obviously that's the energy which you then get back in a fuel cell or by burning the hydrogen, which we just did.