LETTERS FROM THE LAB #005

written by Michael Dicker, CTO at Actuation Lab

Michael Dicker standing by a very large valve

 

The Surprising Lesson we can Learn from Nature about Where and How to use Hydrogen in our Net-Zero Future

 

 

So, what do you all think of hydrogen? In the circles I tread, there seems to be no more controversial topic than whether hydrogen is or isn’t a sensible part of the technology we need to help deliver our net-zero future.

Having recently received funding to explore new leak-free valves for hydrogen, the Actuation Lab team has had the opportunity to have a detailed look at the many hydrogen-related projects currently underway in the UK. This investigation into hydrogen has included a visit to DNV Spadeadam to see progress towards building the impressive FutureGrid test facility, as well as seeing inside the outwardly less impressive (it was just like visiting any old house) Hy Street development, part of the H21 project.

As a result of this wide exposure to hydrogen projects, everyone that we meet seems to ask us, “what’s going to happen with hydrogen?”
So I wanted to have a go at answering that question as best I can from the view of what we have seen in the world of hydrogen lately, and to add a unique and unexpected bio-inspired perspective.

Hydrogen – The Basics

The first thing you should know if you are new to hydrogen, is that the poor efficiency of any hydrogen generation and use means that for most applications, the direct use of renewable electricity will be a more competitive solution than the use of hydrogen.

For example, if you were to take the electricity from a wind turbine, use it to generate hydrogen in an electrolyser, transport it to your home, and burn it in your boiler to keep you warm, the amount of heat you will get at the end of this process will be just 1/6th the amount of heat you would get if you took that same electricity and used it to power a heat pump in your home.

This is best captured by Michael Liebreich and his Hydrogen Ladder, which shows (Figure 1) that hydrogen makes little sense for things like fuelling our cars, a use which sits at the bottom of this ladder.

 

Michael Liebreich’s Hydrogen Ladder: classes going down from A (green) to G (red). In class A:Fertiliser, Hydrogenation, Methanol, Hydrocracking, Desulphurisation. In class B: Shipping*, Off-road vehicles, Steel, Chemical feedstock, Long-term storage. In class C: Long-haul aviation*, Coastal and river vessels, Remote trains, Vintage vehicles*, Local CO2 remediation. In class D: Medium-haul aviation*, Long distance trucks and coaches, High-temperature industrial heat. In class E: Short-haul aviation, Local ferries, Commercial heating, Island grids, Clean power imports, UPS. In class F: Light aviation, Rural trains, Regional trucks, Mid/Low-temperature industrial heat, Domestic heating. In class G: Metro trains and buses, H2FC cars, Urban delivery, 2- and 3-wheelers, Bulk e-fuels, Power-system balancing. An asterisk means via ammonia or e-fuel rather than H2 gas or liquid. Source: Liebreich Associates (concept credit: Adrian Hiel / Energy Cities)

Figure 1 Michael Liebreich’s Hydrogen Ladder

 

However, there are enough things at the top of the ladder for which hydrogen can be used competitively to make green hydrogen (hydrogen produced with renewable energy) worth pursuing as part of our net-zero future. For example, simply replacing the grey (polluting) hydrogen used in fertiliser production today would cut global CO2 emissions by 2%. If we could use hydrogen to decarbonise steel production, CO2 could be cut by a further 9%!

While the Hydrogen Ladder is a generally excellent guide for evaluating potential uses of hydrogen, I would caution against assuming there is no place for hydrogen lower down the ladder. In our experience of applying new technologies into old industries, we find that people will look for the easiest solution, even if your new solution is “better”.

What this means as a hydrogen example is that while heat pumps will be the most obvious and cheapest to run choice for home heating (and mandated in new builds as a result), if your boiler were to die in the next few years, you may still choose the easier option of a quick hydrogen ready gas boiler replacement, than the “better”, but harder, installation of a heat pump.

The Role for a Green Gas Grid

With this reluctance to change being considered, and with many industrial gas uses in mind, we have seen a huge amount of time, effort and money being put into testing and preparing the UK gas transmission network for hydrogen.

While network owners obviously have an interest in ensuring a continued role for their expensive assets (just this March investors led by Macquarie took a 60% stake in the UK’s high-pressure gas transmission network at a value of £9.6 billion), this doesn’t mean we shouldn’t take advantage of this interest to meet our net-zero goals, or that there aren’t also some real benefits to maintaining a gas grid, and the inherent energy storage it provides, for its ability to increase flexibility and resilience in our future net-zero energy network.

The Institute of Gas Engineers recently released a policy paper that makes the case for maintaining a gas network in the UK in the name of system resilience and cost, which references work by the Energy Networks Association that suggests maintaining a green gas grid over full electrification could save users £13 billion a year by 2050.

But how can the inefficient solution, the use of green hydrogen, be better and cheaper than the direct use of green electricity? Surely there aren’t any examples where we maintain an inefficient energy solution for what is effectively just extra convenience?

A Biomimetic Energy System

Well, as it turns out there is an example of this that you are far closer to than you could ever imagine, and that’s how we power our own bodies.

Our muscles have two modes of operation: aerobic (with oxygen) and anaerobic (without oxygen). If we need to rapidly exert energy (think running away from some prehistoric monster – a beast from the East perhaps?), then we can draw upon a rapid burst of anaerobic power for a short period of time. Humans can deliver ~5x more power anaerobically than aerobically through the cardiovascular system (Figure 2), but this anaerobic energy is only 5.5% as efficient!

 

Graph representing Mechanical Output Power (in kW) over Time (in minutes). Theoretical aerobic power output starts at zero, reaches about 0.25 kW at 1 minute, levels off at about 0.3 kW at 2 minutes and remains stable until 100 minutes (edge of graph). Theoretical anaerobic power output start at the top of the chart (over 1.5 kW after only 0.3 minutes), goes down to about 0.7 kW at 1 minute, reaches around 0.45 kW at 2 minutes and slowly rejoins the other curve at about 0.3 kW at 100 minutes. Recorded power output for various activities (cycling, handcranking and rowing) are represented by points on the graph, roughly 1.4 kW at 0.1 minute, 0.95 kW at 0.3 minutes, then hugging the Theoretical Anaerobic power output curve.

Figure 2 Human recorded and theoretical mechanical power output over time, where time is the duration over which a given constant output can be maintained (Wilke 1960)

 

Why do we have this alternate anaerobic energy pathway if it is so inefficient? Because to deliver that required power for the rare moment we need to escape from predators, we would have to carry around 18 hearts and 36 lungs, which would need to be maintained while being largely unused.

Attempting to completely electrify our energy system in the UK with renewables while still maintaining the same level of system resilience such that we can deal with extreme events (think the “Beast from the East” cold snap) is like investing in your 18 hearts and 36 lungs. A better way might be to model our energy systems on our own bodies, which use typically 90% of their energy through efficient aerobic processes (electrification) but maintain a convenient, yet inefficient store of rapidly deployable energy (a green gas network).

The UK gas network, and the fuel within it, is better thought of as an energy store with rapid deployment than a system for distributing power for continuous use, and this is where a large part of its value lies. In fact, it’s estimated that replacing the storage capacity offered by the gas grid with batteries would cost £1 trillion!

So, what next?

So, with a bio-inspired model, I do believe there is a strong case for investing in a hydrogen grid. However, our research at Actuation Lab has shown that if we are going to fulfil this plan, we must make sure it doesn’t leak.

While we think a lot about the damage burning fuels is doing to our climate, you might be surprised to hear that 30%-50% of global warming results from the release, not combustion, of gases. Even if a future gas grid is to carry hydrogen that burns without producing global warming CO2, leaking hydrogen and its resulting reaction with different elements in the atmosphere will still lead to warming.

In fact, it is thought that the influence of hydrogen in the atmosphere will be around 11x worse than CO2. As a result, if we are going to maintain a gas grid, it’s critical that we invest to eliminate leaks. This is what we are working on at Actuation Lab with our Dragonfly Valve, eliminating the seals that so often fail on current valve designs, and in doing so, eliminating the leaks that result as well.

Back