The need to invest in renewable energy is a fact. The consumption of fossil fuels is a million of times faster than the rate of natural production. Hydrogen is one of the candidates as a renewable energy carrier in the future: its energy density is three times greater than that of fossil fuels and it exists in large quantities in nature (water being the main source). The challenge is, however, to store it in an energy efficient and compact way. Andreas Züttel, head of the “Hydrogen & Energy” Division at Swiss Federal Laboratories for materials Science and Tecnology (EMPA), and president of the Swiss Association for Hydrogen “HYDROPOLE”, participated in the "International Symposium on Energy, Environment and Sustainability", organized at the UAB in occasion of the tenth anniversary of MATGAS, where UABDivulga had the chance to interview him.
How does hydrogen give energy?
By oxidation with oxygen from air. Hydrogen is an energy carrier and it has the advantage that it exhibits the largest energy density of all materials we know today with combustion, three times more than fossil fuels!
Water contains Hydrogen and there is plenty of it on our planet. Why are we not already using water as a renewable source of energy?
Water is the carrier of hydrogen. We have to invest energy to split water by electrolysis and then store the hydrogen. Afterwards, by burning the hydrogen we get the energy back and we have water again. In that sense, it is one of the few possibilities to generate completely green fuel. But you need an electrolyser to do it. And the storage.
And storage is a problem...
The difficulty with hydrogen is that it is a light element and due to its physical properties it is difficult to store. We know how to produce hydrogen efficiently, with more than 80% of efficiency but we deal with a big challenge to store it in an energy efficient and in a compact way.
You propose to store hydrogen in metal hydrides, but how do they work?
We bind hydrogen to metals to form metal hydrides and there are basically two kinds of metal hydrides: the purely metallic hydrides, that release hydrogen when we heat them up or by lowering the pressure, and the complex hydrides that could directly be brought into a special fuel cell where the complex hydride is oxidised.
You also talk about producing synthetic fuels.
The idea is to use hydrogen to reduce CO2 to hydrocarbons and then produce something like synthetic fossil fuels, that is liquid hydrocarbons. This would be a possibility to remove CO2 from the atmosphere again and on one side use it as a fuel, but we could also in excess produce oil and put it in the ground and fill up the oil fields again.
And would that be a good way to reduce atmospheric CO2?
One of the big problems is that CO2 will continue to increase even more that it did in the past and the only way we can get rid of the CO2 in the atmosphere is to capture it and store it somewhere. If we store CO2 directly, then it is lost, we cannot use it anymore, but if we produce a kind of synthetic fuel, the next generation could use it. Synthetic hydrocarbons can be treated exactly as fossil fuels. They are easy to store in barrels and the do not require a major change on the distribution infrastructure nor on the consumption side.
So they would also release CO2.
Of course, that’s why they have this large energy density, the oxidation of carbon is delivering about half of the energy in hydrocarbons.
But then, this way, we couldn’t reduce the CO2 atmospheric...
Yes, if we produce more that is consumed, then we can reduce CO2 and fill up the oil fields again or store it somewhere else. But of course the most important is to reabsorb the CO2 we produce to close the cycle and then, if in the future we have sufficient renewable energy, we can also produce synthetic fuel for the future.
You also propose ammonia as a carrier of renewable energy.
NH3 has similar energy density as fossil fuels, but it is much more difficult to use: ammonia is a poison. There are two possibilities: combust ammonia directly, with the disadvantage that we’ll probably get nitrogen oxides, which are not good for the environment, or to split the ammonia into nitrogen and hydrogen.
And nitrogen oxide has greenhouse effect...
Yes, it has a greenhouse effect, but even worse, it oxidises the lungs and provokes the acid rain that harms plants...
Ammonia has been largely and for a long time used and its reaction with hydrogen is well known. What is new here?
What is new is to bind it with a magnesium salt to make a compound and convert it into a solid and then it is much less dangerous. From the compound we can release the ammonia again.
Why so much research into renewable energies?
It’s only a matter of time that we have not enough fossil fuels any more. We use them a million times faster than they are naturally produced. From what we know we have already consumed half of the fossil fuel resources and now China and India, half of the world’s population, are starting to industrialize, so the demand for fossil fuels is likely to increase worldwide. Only renewable energy, especially solar energy, can cover future demand.
Could you state a date for the end of fossil fuels?
The problem is not the moment when the fossil fuels are sold out but the moment when we are not getting as much as we need anymore and this will take place already in the next years.
Who will be more affected by this problem?
Those who are able to substitute, for example to produce warm water from solar light, instead of fossil oil or electricity, will more easily adapt to renewal energies. And those who stick to the old system will suffer a lot. But it needs investment, that means, the conversion is much easier as long as we have fossil fuels available and very difficult if we wait until we have a reduced availability of fuels.
How much investment are we talking about?
I calculated, five years ago, for Switzerland, that converting the whole country to renewable energy would have required 30% of the annual income of each citizen. Today it’s already a whole annual income we would have to invest. And if we wait a few more years, it will be so much that we will not be able to afford it.
So do you think it is possible to move from fossil fuels to renewable energies entirely?
Yes of course! There is no other option. And we have to do it as fast as possible. If we wait too long, until we suffer from a lack of energy carriers or fossil fuels, we’ll have no choice anymore. Then, the only choice is to reduce the population and this would be horrible. We’ve known about the problem for 40 years and it is very selfish not to react and try to continue. The next generation will have no choice anymore.
So do you think our children will see it?
I think we will see it if we don’t install now the systems which allow us to really reduce the combustion of fossil fuels! The problem is that we are always listening to the politicians and to the oil producers and they will not tell us about the problem. The former resident of Shell mentioned once that resources at Shell were overestimated by 20 % and overnight the stocks broke by 30% and he was fired.
What would be, then, the way to follow: to reduce the energy demand, to use renewable energies, and generate sinks for atmospheric CO2?
Yes, but most importantly now is to build the installations to secure energy from renewable sources and then we can continue with all the work for the reduction of CO2, etc. But if we don’t have energy available anymore, we will have a major problem.
B.11870-2012 ISSN: 2014-6388