Hydrogen gas made via the electrolysis of water using surplus renewable electricity can be stored then used when needed for power production, heating, industry and in vehicles. It’s an ideal multi-purpose fuel; it only produces water, and some NO x , when burnt in air or used in a fuel cell to re-generate electricity. And now this power to gas (P2G) approach is becoming cheaper.

Perhaps the most exciting prospect is that P2G offers a way to balance variable renewables. Indeed, it turns their variability into a solution rather than a problem. In order to meet demand most of the time, at non-peak demand times a power system based on renewables would be likely to have substantial overcapacity, so that there would be surplus renewables output. If that can be converted to storable hydrogen, it can be used to generate power later, when renewable supplies are low and power demand high. Since there could be a lot of this hydrogen, some of it could also offset fossil gas use, by being injected into the gas grid, possibly after conversion into methane. In addition, some of the hydrogen or methane could be used as a vehicle fuel. It all sounds wonderful, but is P2G really viable at scale? A recent report on green heating options from the UK’s Climate Change Committee (CCC) was unconvinced, but there are other views.

A study for the UK’s Department for Business, Energy and Industrial Strategy (BEIS) by Northern Gas Networks (NGN) and UK hydrogen pioneer ITM Power says that large scale power-to-gas conversion could integrate with current gas networks, with hydrogen being storable at scale and suited to injection into the gas network. The study examined the potential for the deployment of storage capacity, at 50 MW and above, within the boundaries of NGN’s distribution network, and the use of the hydrogen in the network.

After accounting for seasonal variations in gas demand and the amount of hydrogen that would be able to be produced and blended with natural gas, the report concluded that a large part of the existing NGN grid could be supplied via P2G conversion. Specifically, it identified four potential sites for P2G units, with NGN’s existing InTEGReL (Integrated Transport Electricity and Gas Research Laboratory) site in Gateshead highlighted as the best location for a first-of-its-kind large-scale demonstration plant of 50-100 MW. ITM claimed that the system could use renewable power to produce low carbon hydrogen that could then be blended with natural gas to provide greener gas to over 243,000 domestic and industrial customers in the region, while also providing hydrogen to a local hydrogen refueling station.

Mark Horsley, NGN’s CEO, said: “Power-to-gas technology has the potential to answer some of our key energy storage challenges because of the gas network’s sheer size and flexibility. This study has delivered some compelling results and insight into how a whole systems approach and green hydrogen can facilitate decarbonisation across all energy vectors.”

Costing the future

What about the cost? At present most hydrogen is produced using high-temperature steam reformation of fossil methane (SMR) and it’s usually said this is far cheaper than the electrolytic route, which is seen as less efficient, with maybe 50% conversion losses. For example, French company Engie, which is looking to shift to green hydrogen production and distribution, says steam reforming of hydrocarbons, which accounts for 95% of hydrogen produced today, costs about €2/kg, compared to €6/kg for electrolysis.

However, as electrolysis technology improves, the situation may change. Last year Chris Goodall estimated that, at then common power and electrolyser prices, hydrogen made from surplus renewable electricity was almost at the same price as hydrogen made via steam reforming of fossil methane. That looked a little optimistic at that stage, but perhaps not if you include the significant cost of carbon capture and storage (CCS) to make the latter route less carbon intense.

Certainly, as green power prices fall and electrolysers become cheaper and more efficient, the relative advantage of using electrolysis will improve; increasingly so as surplus renewable output becomes more available – it’s in effect free and would be wasted otherwise. Progress does seem to be underway, with the advent of high efficiency cells.

Perhaps the most exciting prospect is that P2G offers a way to balance variable renewables. Indeed, it turns their variability into a solution rather than a problem. Dave Elliott

ITM Power claims that its PEM cell has an overall efficiency, with heat recovery, of 86% and it has been winning orders for its technology in Germany, as well as the UK. ITM clearly sees this as the way ahead and it’s not alone. A recent academic overview presents some favourable conclusions. Looking at experience with pressurized solid oxide cells with internal methanization, some of which have recently returned good experimental results, it claims, on the basis of its system modeling, that “electricity can be stored as synthetic natural gas with an energy efficiency of 89%”, and that “the gas to electricity efficiency is equally high, resulting in a round-trip storage efficiency of 80% (DC-to-DC)”.

So, despite the CCC’s reservations, P2G does look promising. Some say that, with renewable costs falling, we may reach the point where P2G becomes fully competitive. A recent study for Greenpeace Energy by Berlin-based Energy Brainpool claimed that hydrogen from surplus renewables will be cheaper than gas in the 2030s. It cites the International Energy Agency view that natural gas prices are set to rise steadily until the 2040s, from €0.017/kWh in 2020 to €0.032/kWh by 2030 and €0.041/kWh by 2040. By contrast, IEA analysts forecast that production costs for hydrogen generated by wind power are set to fall from “about €0.18/kWh” to €0.13/kWh by 2020, to €0.12/kWh by 2030, and to between €0.021/kWh and €0.032/kWh by 2040.

Fuelling the options

As I have noted in earlier posts, there are other approaches. For example, the Leeds H21 100% hydrogen heating project is getting some support. But it is focused on SMR using fossil gas with CCS — P2G has been relegated to a possible longer-term option. However, the case for P2G is building up, not least since, unlike the H21 plan, it doesn’t need costly and uncertain CCS, and can deliver fully carbon-neutral hydrogen.

P2G and its derivatives are becoming quite well established on the European continent, led by Germany with, as German Energy Agency DENA notes, 20 or so hydrogen/methane projects for grid-balancing, vehicle fuel production and gas mains injection. There are videos promoting the Falkenhagen project from UTV and E.ON. Amongst many other projects across Europe, Austria is exploring novel ideas including a range of end uses, such as steel production.

Clearly, there is a lot happening in this field, and novel improved technologies may also be on the way. The focus during the initial phase has been on options with high added-value, vehicle fuel production inevitably being one, with German car companies much in evidence. But the wider potential for P2G is now also being explored. It’s still mostly in its infancy around the world, but DENA says that Germany is looking to have 1 GW of P2G capacity by 2022 and, as the technology develops and costs fall, the idea seems certain to spread.

How far remains to be seen. As I reported in an earlier post, the UK Policy Exchange was a little unsure, but did say that electrolysis “has the potential to achieve far greater cost reductions than other technologies”. And a new report from The Oxford Institute for Energy Studies notes that there are now about 50 pioneering P2G projects around the EU, though most of them are small — under 10 MW. The institute says it will take concerted government action to make P2G happen on a wide scale. The UK’s ITM is one of the leaders. Maybe we should capitalize on that.