Mixing hydrogen and natural gas to heat homes

世界需要离开它的大部分煤炭、石油和gas in the ground between now and 2050, if we’re to stand any chance of keeping climate change to within a 1.5 degrees Celsius level of average warming. And that includes the UK. But according to a 2021 survey by the UK Department for Business Energy & Industrial Strategy, 77% of respondents said they use gas central heating. How do we cut our carbon footprint while not leaving three quarters of the country out in the cold? One answer might be to send something different down the pipelines: hydrogen. When this burns, it releases only water as a waste product. As a first step, if we replaced some of the natural gas - or methane - with hydrogen, assuming that people’s appliances worked satisfactorily, we could cut the carbon footprint of the process without having to change anything else. One company has tried this recently - in a small scale way - with Keele University and they announced the results this week, as Angie Needle explained to Chris Smith...

Angie - I'm Dr. Angie Needle. I'm the Strategy Director at Cadent. Cadent is a gas network provider, so we deliver natural gas to 11 million homes and businesses across the UK in those yellow pipes that you see. In this instance, we were exploring how we can introduce a proportion of hydrogen into the existing natural gas network, so that we can reduce the carbon emissions of the energy that's used in people's homes.

Chris - Why can't we just put hydrogen down those pipes rather than natural gas? Because if one looks back in history - before we were using natural gas, we were using town gas, or coal gas, and that contained a lot of hydrogen. So were we not already kind of familiar with how this works anyway?

Angie - Yeah, I would agree that that is true. Town gas had up to 50% hydrogen in it. The bits of our gas network will have seen this before, but it's the end-user appliances - the boilers and the cookers and the fires - that haven't. And so what we want to be sure of is that when we start introducing hydrogen and people are using a lower carbon gas, that the experience in the home is exactly the same. And that's what this project is looking at - making sure that when we introduce small amounts of hydrogen, it makes no difference to the appliances and they can continue as normal.

Chris - Where did you do it?

Angie - So Keele University has got its own gas network - it owns it itself. And so we got together with Keele on their campus, which has about 100 domestic buildings of all different shapes and sizes, some which lecturers and whatnot live in, and some which are privately owned, and about 30 University buildings. And so we built a compound there - we made the hydrogen on the site - and we blended it through what we call a Grid Entry Unit, a new piece of kit, into their gas network. This had never been done before and was massively successful, because nobody knew any different. The consumer experience was - "We didn't even know this was happening. We couldn't see any changes."

Chris - How much hydrogen were you adding to the gas supply?

Angie - We added up to 20%, and that's quite important because most of the cookers and fires and things that are out there today can take up to about 23% in the way that they're built and tested. 20% allows about a 7% carbon emission saving.

克里斯,氢admixtu很容易做到这一点re? To put it into the gas supply?

Angie - Largely all we do is to take a bit of the gas out - the natural gas - blend in the hydrogen, make sure it's mixed up really well, and put it back into the gas. The main challenge is actually having enough hydrogen and making sure we can have low carbon hydrogen to put into the gas network. But the first-of-their-kind equipment that we developed, we can see that you can scale and replicate quite easily. So you can start putting in hydrogen at different places in our gas network.

Chris - In practical terms, were we to start doing this across the country, how much energy is actually being provided by the same volume of gas? Is hydrogen as energy dense as natural gas? In other words, are people going to have to burn more of it to get the same bang for their buck?

Angie - Hydrogen has actually got a huge amount of energy content in it, but it takes up quite a lot of space. It's quite a light molecule. So what happens is that 20% hydrogen by volume is actually only 7% by energy. We're working at the moment to make sure that the existing pressures that are on our pipes can take the extra flow, if you like, of hydrogen. So you need to use a bit more hydrogen to get to the same calories, or energy, as you get today with methane, but the most important thing is hydrogen doesn't produce any carbon dioxide.

Chris - So you would regard the present situation then as a stepping stone towards the full-on 100% hydrogen energy economy?

Angie - In parts, yes, a 20% blend helps us get the infrastructure and the hydrogen production going. We need lots of hydrogen to get to net zero, almost regardless of what it's used for, and in the UK we don't make much today, so we need to get production going. But I think there will ultimately be a blend of different uses of energy in the future - renewable electricity and hydrogen. And regarding consumers, we need to help them understand whether their home is suitable for electric solutions or whether it's suitable for hydrogen, so that there is choice. Choice is good, because if we put all our eggs in the same basket when it comes to energy, we tend to find that each one has limitations that need the other to balance it out. So I'm very much supportive of having choice, but also that we help consumers make that choice.