'Wrong side of history' | Wake up to the hype around green hydrogen for heating

Governments around the world are developing strategies and suites of policies to support their climate change mitigating ‘net-zero’ ambitions. Of course, more recently, linked to the terrible Russian war against Ukraine, policymakers are also looking to limit exposure to fossil fuel imports and the risks they pose.

And while climate change demands an emergency response, there is a risk that going too fast, without evidence-backed decisions, will actually undermine efforts to decarbonise.

"Modest role"

To reach net zero, practically all fossil-fuel combustion needs to be replaced.

For buildings, heat pumps are a clear winning technology, extracting the majority of their heat output from outside air, ground or water. Even in cold temperatures, heat pumps can be powered using increasingly cost-effective, renewable electricity.

The proponents of unchecked hydrogen use are on the wrong side of the evidence, and history. They ended up there because of money — or more specifically, sunk assets, which are now under threat as the world attempts to move away from fossil fuels and its associated infrastructure. The use of hydrogen made from natural gas with carbon capture and storage (CCS) could keep gas flowing through infrastructure that would otherwise be stranded, and maintain the need for oil and gas development and processing facilities through which hydrogen can be produced.

Hydrogen is being promoted through a powerful international, political and media machine, associated with the incumbent fossil fuel industry, and it is lobbying governments around the world.

There are two potential impacts of such lobbying.

Firstly, there could be direct impacts on policy, with governments offering financial and regulatory support for investments in hydrogen, in spite of evidence suggesting this may be a poor use of funds. Indeed we are already seeing this.

Pumping up the pressure

On the face of it, for countries such as the UK and the Netherlands, with well-developed and highly interconnected gas systems, it makes sense to consider the existing system and ask whether it be used in a zero-carbon world. The simplicity of ‘greening the gas’ or the idea of a ‘drop-in replacement’ is also an extremely effective lobbying and sales line.

In some respects, hydrogen does have some extremely valuable characteristics for clean energy systems. Firstly, it can be stored indefinitely (although the very small molecules make it prone to leaking out of most containers), which in a world of variable renewable energy is potentially attractive for long-term or transportable storage. Secondly, like fossil gas, it can be burned to produce heat or electricity; or used in fuel cells (producing heat and electricity at once). It can also be produced through the electrolysis of water, powered by increasingly cheap renewable electricity.

Yet just because you can do something, it doesn’t mean you should. And this is patently true for the idea of widespread hydrogen use. In the same way that champagne is reserved for special occasions, hydrogen is a premium product with specific value.

Even a cursory look at the basic technical details show hydrogen as a very expensive and environmentally unattractive solution for the heating and much of the transport sector.

Not a source of energy

A common misunderstanding is that hydrogen is itself a source of energy. It is not. It is solely a vector or energy carrier: a means of storing and transporting energy. Hydrogen gas does not exist in a state where it can be extracted from the environment in useful quantities, but it must be created, which is energy intensive and costly.

Enter 'blue hydrogen', a term that refers to hydrogen produced from fossil gas with (some) greenhouse gas emissions captured in the production process and in theory stored so that they have no impact on the climate.

With fossil gas prices skyrocketing to record highs, and the entire European continent aiming to rapidly reduce its exposure to Russian gas imports, blue hydrogen has rapidly gone out of fashion. Although you won’t hear that mentioned by many industrial hydrogen proponents.

Much of the hydrogen push has silently pivoted towards 'green' hydrogen, created from water using green electricity. While on the face of it, a move from fossil fuel-derived hydrogen to renewably produced hydrogen might appear to be a good thing, the reality is that burning green hydrogen at scale seems even less plausible than burning blue hydrogen. The energy content of green hydrogen comes from electricity and the production process involves significant energy efficiency losses.

The electricity could be used directly in 100% efficient electric heaters or even more efficient heat pumps which use electricity to extract heat from the environment. Heat pumps operate with an effective efficiency of over 300%, with each unit of electricity going in, resulting in three units of useful heat.

These conversion efficiencies are a basic element of energy economics, and are the nub of the green hydrogen debate.

Energy conversion basics

All energy conversion processes result in losses, meaning you get less useful energy out compared to the amount you put in. For example, a power station burning gas may be around 60% efficient with 40% of the energy lost as heat.

Fundamentally, the hydrogen pathway for heating (all the way from electricity generation to burning it in a boiler) has much greater energy losses than direct electric route. It therefore requires far more primary energy (about 6 times more) than using a heat pump to deliver the same amount of heat, leading to much higher costs.

The biggest energy loss associated with green hydrogen use is in the process of electrolysis, or splitting water molecules to produce the hydrogen in the first place.

Blue hydrogen was, at least before the gas price explosion, potentially cost effective compared to widespread use of heat pumps in various independent pieces of analysis, albeit under less stretching greenhouse gas reduction targets.

The graphic above spells this out. The first route (shown on the left) shows transmission of the electricity to a consumer where it powers a heat pump. As heat pumps use electricity to heat a building from the environment that results in around three (or more) units of heat for every unit of electricity consumed, they have an effective 300% efficiency (known as the “coefficient of performance” or COP, which is in this case three). While some losses occur in the transportation of electricity, the overall effect is that 100 units of electricity results in about 270 units of heat reaching the consumer. This is an amazing energy uplift when you consider the value of clean electricity and that over two thirds of the useful heat is coming from an inexhaustible renewable source.

The second route (centre) uses a simple electric space heater, powered by green electricity. There are small losses in electricity transportation, but most of the 90 kWh of electricity reaching the heater is converted into useful heat, yielding about 86 kWh.

The third route on the right shows the generation of green hydrogen which is burnt in a boiler for heating. Significant losses occur in the conversion of electricity to hydrogen. But further losses occur as energy is used to store the hydrogen and transport it to buildings and also when the hydrogen is burnt in boilers. 100 units in at the start of the process leads to 46 out in this pathway. Comparing the left hand and right hand routes, the heat pump route delivers about six times more heat than a green hydrogen boiler for the same amount of electricity generation.

This six times difference is the stark reality of using hydrogen for heating compared to heat pumps.

Perhaps it is not quite that simple

Now, you might be thinking, OK that’s great in theory, but you don’t always have renewable electricity being generated when you need your heat pump running and so you will not be able to get that efficiency all of the time.

It’s also important to bear in mind that heat pumps perform less well when it is colder with a performance of possibly 150% (a coefficient of performance of 1.5). But even in that case, the heat pump would still generate three times more heat per unit of electricity than green hydrogen. Using a heat pump will therefore always be more efficient and require less primary energy than burning green hydrogen for the same amount of heat.

Need for speed

Clearly the climate is changing and atmospheric greenhouse gas concentrations continue to increase. Slow progress thus far means that the world needs to decarbonise as quickly as possible. Any delay to decarbonising heating or transport, such large chunks of current emissions, could be disastrous. We obviously also need to wean ourselves off increasingly expensive fossil fuels.

Taking the hydrogen-for-heating route would not just cost much more but would take longer to achieve, requiring so much more primary energy. This idea is unlikely to ever get beyond limited trials.

Amidst the hype, citizens are become increasingly confused about future heating technologies. All of this leads to climate delay and continued exposure to fossil fuels.

But when decision-makers are faced with the real-world cost implications of hydrogen for heat, the role of electrification and energy efficiency will eventually be realised. Yet this may be too late.

Decarbonising heat will be hard enough. And when speed is everything, there is no time for the hydrogen distraction.