Last week’s article on The Fifth Estate arguing that hydrogen for homes is a terrible idea needs correcting. Green hydrogen has a firm place in a zero carbon future.
Its author, Gabriel Levy, is confining his argument against hydrogen to its domestic use. It will still be widely used by 2050 in industry and transport. He’s right that the Leeds H21 project does rely on steam reforming of fossil gas methane (water and methane producing hydrogen and carbon dioxide) and so the carbon dioxide will have to be piped into a salt cavern underground. This is not yet a proven technology.
But there is a place for green hydrogen in a zero carbon future. In homes too. To find out why and how let’s look at the general market first and then at the market for home use.
Countries around the world, including in Latin America, are vying to obtain a slice of the market for green hydrogen. The EU and China are well in this race, with the EU in the lead.
As Levy points out, there are two crucial tests which green hydrogen has to pass: the first is that it must be truly green, and not be a route to keep the fossil fuel industry limping on past its sell by date, sneaking in blue or grey hydrogen to keep up with market demand. The second is price.
Is it green?
Green hydrogen is produced by proton exchange membrane electrolysis from renewable electricity generators, when the electricity is not needed at that point in time for anything else. It is a form of energy storage, to be used when required.
Combining hydrogen from different sources in the gas network will inevitably happen during any transition to a renewable gas future, as sufficient renewable energy supply ramps up. But once we reach the point when we would supply all gas from renewable sources, steam-reformed hydrogen should and will be phased out.
When the wind blows at night there is less demand for electricity. Making this currently “free” electricity produce hydrogen, which can be sold for a good price, is a perfect use for it.
The price test
But will the price it can fetch cover the costs of production? Green hydrogen must be competitive and affordable.
The recent report by BNP Paribas on green hydrogen, net zero and the future of the EU Emissions Trading Scheme, calculates that to meet the European Commission’s vision for green hydrogen to be a key player at the end of this decade, 70 GW of electrolysers will be needed, and investment of €391 billion (AU$639 billion).
To be competitive with grey hydrogen, they estimate this implies a trading carbon price of at least €79 (AU$129 billion), a tonne, depending on costs in the supply chain.
Reaching this figure for pricing carbon will mean concerted and collective legislative efforts around the world to tackle climate change and price out fossil fuels.
Is this possible? Given the economic shock to the EU-ETS from COVID, carbon’s price has held up remarkably well. From a low of €14.3/t (AU$23.4) in the early stages of the lockdowns across the EU it went to a near-record all-time high of €30.3/t (AU$49.5) in June, and has held at pre-COVID levels ever since.
Put simply: the pandemic has strengthened the case for renewables and a zero carbon future, and this section of the economy remains a strong.
Since confirmation that Joe Biden is the new president-elect of the US, and since he will rejoin the Paris climate accord by executive decree in the first days of his presidency, shares in renewable energy companies have risen in anticipation of the investment this will unleash.
So, yes, it is perfectly possible.
Using hydrogen to store renewable energy is called Power-to-Gas (P2G). It has been proven for a number of years in real conditions in Germany by a consortium led by ITM, to supply power to the electricity grid and to the gas grid when required as a form of grid balancing.
Professor Marcus Newborough, development director at market-leader ITM Power, notes the advantages of P2G as being its ability to:
- respond to an instruction from the grid operator to charge up or absorb electricity
- hold on to the stored energy for a significant period without incurring energy losses
- discharge energy on demand at a desired rate
- be scaled up in number or capacity as we head towards a much more renewable electricity system
He says: “Clearly the economics of P2G are a function of such balancing services payments from the grid operator and the electricity tariff, but in addition P2G offers a greening agent to the gas grid operator in the form of injecting hydrogen at low concentrations into natural gas.
“So, the economics are also a function of the value placed on greening up the gas grid. By analogy we have seen in recent years in France, Germany and the UK feed-in tariffs for injecting bio-methane into the gas grid as a greening agent and these have been up to four times the value of a kWh of natural gas.
“The economic case therefore depends on a combination of value propositions and costs (providing services to the electricity grid, the electricity tariff paid, the value of green gas for the gas grid and the capital cost of the plant).”
Domestic use of hydrogen
Levy argues that we don’t need gas to heat houses. In the UK no new houses are being built that are connected to the gas grid. But 23 million or 84 per cent of homes are already connected to the gas network. Right now, about two-thirds of residential and commercial energy consumption is met by natural gas.
Several million people use gas not just to heat their homes but to cook on.
They prefer gas to electricity because it is more responsive. Persuading these people that they have to get rid of their perfectly good cookers and buy new electric ones is not going to happen easily, not to mention the ecological footprint of all these new appliances, and the ecological footprint of removing the existing gas infrastructure.
These are strong arguments for keeping and greening the gas infrastructure.
But hydrogen is not the only green gas
It faces competition from other forms of biogas or renewable methane.
Methane (CH4) is 7.857 times more dense than hydrogen. Natural gas carries 41.7 per cent less energy per unit of weight, so just over three (3.28) times as much volume of uncompressed hydrogen is needed to obtain the same amount of energy.
Therefore, the gas needs to be delivered at a higher pressure to compensate. Being a smaller molecule it can escape more easily through leaks, so the gas grid will need upgrading to cope.
But this happened before, in the 1960s, quite seamlessly, when the UK switched from what was called “town gas” (made from converting coal to coke) to “natural” gas from the North Sea oil and gas fields.
However, this conversion is unnecessary if bio-methane is used. The snag is, we can’t produce enough, sustainably. However, it can satisfy a reasonable proportion of domestic needs.
Amongst the potential competitors for meeting the gas demand renewably are anaerobic digestion and bio-synthetic gas (bio-syngas or bio-SNG). Waste from a city could produce enough of such a gas to meet one quarter of its domestic demand.
The technologies to support anaerobic digestion and BioSNG are tried and tested and low risk. It is two to three times more efficient to use organic waste for biogas than to burn it for electricity.
BioSNG is processed from biomass or waste organic matter using gasification, an intensive process but one which produces nearly as much energy from one tonne of feedstock as burning wood, and nearly three times more than using straw and burning waste, according to Britain’s National Grid.
Using waste for BioSNG also greatly reduces greenhouse gas emissions compared to landfill and energy recovery.
The advantages of renewable biogas from waste are that waste has a negative cost but can produce gas at a cost similar to that of fossil fuels. It supports more jobs and requires no changes to network infrastructure or appliances. Waste to BioSNG or biomethane are two or three times as efficient as waste to electricity.
It also ensures the long term future of the gas grid – avoiding decommissioning costs.
And these types of biogas are a local solution, producing minimal waste emissions. A plant can be located close to the communities it serves. However, BioSNG is still a nascent technology, with an as-yet-unproven route to market. Anaerobic digestion is not.
A pilot BioSNG project in Swindon has been beset by delays and cost overruns, but this is to be expected with a first-of-a-kind project.
In its infancy
According to Chris Clarke, director of asset management at Wales and West Utilities, “Biomethane is in its infancy and green gases in general are perhaps like solar was 10 to 15 years ago at that stage of development”.
Hydrogen and biomethane can be combined in the gas grid. It doesn’t have to be one or the other. My money is on the future of the gas grid being like this – some kind of a hybrid solution.
Hydrogen can be injected already into the gas grid up to a certain percentage to ‘top up’ natural gas, and indeed it is. It can be transported through a polyethylene pipe network and it offers a familiar service level to customers although existing gas appliances must be modified with a different type of valve.
This is not as expensive or ecologically burdensome as replacing the entire appliance.
The future of grey gas
There’s no doubt that the days of fossil gas or grey gas are numbered.
At the moment, we are already locked in to between three and 4°C global average temperature rise by around the end of the century, which is catastrophic, according to leading climate scientists like Sir David King.
All ports and docks are threatened by the consequent sea level rise. This has implications for the transportation of LNG and LPG by ship from, say, the USA or countries in the Middle East. If docks are flooded, fuel cannot be unloaded. Any city or region relying on this source of fuel for energy would find itself without power.
The same of course is potentially true for offshore wind. Turbines need to be installed in a way that accounts for a future sea level rise of at least two metres, or they will find themselves victim to the very enemy they are installed to protect against.
In short, taking into account the full life-cycle of fuel delivery infrastructure, locally produced biomethane and hydrogen will have to be a part of the renewable energy mix in a zero carbon scenario, for homes as well as transport and industry.
David Thorpe is the author of “One Planet” Cities and director of the One Planet Centre Community Interest Company in the UK.