Is a full "hydrogen economy" possible?
There have been several episodes of “hydrogen economy” thinking over the last 100 years, with the central proposition being that hydrogen, as a fuel, could be at the centre of our energy mix. A prominent question of the past was: if oil was about to run out, could hydrogen take over as a prime transport fuel? This question has lingered since the 1970s, but hydrogen fuel cells as alternative vehicle propellants did not make the progress anticipated. Attention on alternatives to the internal combustion engine has switched to the real prospect now of a substantially electric vehicle fleet, despite oil not running out in the way then envisaged.
It is unlikely that we will ever have a full “hydrogen economy” but that should not mean that we throw hydrogen out entirely. Particularly in the context of climate change, it has a clear prospect of bridging the gaps in energy economy decarbonisation. This is aided by a number of circumstances not present in the 1970s, by the development of technological changes in energy generation, by our resolute failure so far to decarbonise heat and by the emergence of consequent concerns over energy use such as air quality.
The air quality issue, rising up the political agenda, seems to be very difficult to progress on present assumptions in transport, industry and heating. We are seeing the positive and welcome initial stages of a revolution in transport which will radically reduce the effect of vehicles on air quality in cities by electrifying our vehicle fleets and developing hydrogen solutions in larger vehicles. Progress in this transition should be faster than the government’s proposed phase-out of new internal combustion engine sales by 2040.
Tackling decarbonisation and air quality long term
We still have heavy loads of sulphur, nitrous oxides and particulates from old modes of energy production. Despite some progress, energy intensive industries continue to contribute to air pollution and the less harmful, but still significant production of particulates and NOx from the millions of gas boilers almost 90 per cent of us use as the main means of domestic heating. It is in these areas that hydrogen is perhaps now starting to become relevant. It is, after all, the cleanest fuel imaginable: burn hydrogen in oxygen and you’ve got water vapour as a by-product, and that is it. So we can and probably should tackle decarbonisation and air quality long-term in our heating economy by using hydrogen as one substitute for gas in our heating.
An alternative, of ripping out all our boilers and electrifying our heating has the disadvantage of having to do just that; junk an entire delivery system for heat and start again, perhaps with ground source or air source heat pumps. These solutions are only as low-carbon as the electricity they use, and would anyway lead to such a hike in demand for electricity, (heat representing 80 per cent of energy demand) that it would be difficult to envisage how it could be done. Perhaps it is better to focus then on substituting the methane that goes through the system with hydrogen, which, after all, used to be about 40 per cent of the content of original town gas.
It so happens that our gas distribution systems have now largely been “sleeved” with polyurethane pipes, making it suitable for carrying hydrogen molecules with little or no leakage. Once the transmission system was also updated all that you might need to do is to adjust the burner jets on the nation’s boilers. Even before that becomes necessary, injecting hydrogen into the current system to the limit of tolerance of present equipment (it is up to about 10 per cent of the mix, since you ask) would itself make considerable strides towards both decarbonisation and better air quality for the combustion process.
That sounds quite easy, and indeed there are a number of pilot experiments currently under way run by distribution companies doing just that within particular communities. But it isn’t easy. There are and will be problems of price (at the moment hydrogen is far more expensive per kWh of heat than natural gas is) and calorific value.
The overwhelming bulk of hydrogen produced at the moment is through the process of steam methane reformation, and the source fuel is natural gas; which doesn’t take us very much further along the decarbonisation road and worryingly, would tie us into continuing to import gas for the foreseeable future.
Electrolysis as an option
There is, of course, an alternative – electrolysis – the process simply of passing a current through water and hey presto, oxygen and hydrogen emerge. Hitherto electrolysis has largely been dismissed as a method of making large amounts of hydrogen because the electricity would need to be produced in equally large amounts to do it, which would involve relatively high-carbon processes to work and would place a substantial additional burden on generation of electricity for daily use.
However, with the emergence of a large load of variable power onto the system it may be that this “surplus” electricity is becoming available without additional power plants being required. That is, wind and solar do not produce when required, and often produce potentially a lot of electricity when not required. The current solution to preventing surplus power arriving on the system is to pay such plants not to produce, but this surplus power not needed by the electricity system could be harnessed, and would essentially be free. What would be needed at that point is the ability of plants to convert that electricity to hydrogen, which could either be stored for reconversion to power when needed, or drawn off for injection into the gas grid. This potentially produces a storage option which may be more efficient than current battery storage solutions.
It is possible to envisage, then, holistic renewable power plants that integrate power production, power storage and the production of hydrogen, predominantly for heat, all at the same time. Perhaps that is the way we should go with our next generations of wind and field solar, with the advantage that the more renewables that are installed, the more reliable and low-carbon the whole system becomes.
A big caveat remains that even then, the “surplus power” now utilised might not be sufficient to release all the hydrogen that would be needed to run a hydrogen heat economy, but we would have come a long way forward. Those techniques allied with the production of green gases, such as biomethane from anaerobic digestion of waste and organic residues, alongside a significant programme of building energy efficiency such as that recently announced by the Labour Party, could in my view do most of the heavy lifting in the decarbonisation of heat.
We would then have not a hydrogen economy as such, but one in which the role of hydrogen in aiding wellbeing through good air quality and effective decarbonisation through a heating revolution really would be centre stage.
Article originally appeared in the 15th June edition of the New Statesman.