Hydrogen: can we overcome its limitations?

  • 10 February 2021
  • Environment, Technology
  • Colin Matthews

First, let’s set the scene. In the UK 25% of carbon is generated from electricity production, 25% from transport and 50% from heat (industrial and domestic).

Recently there has been significant progress with decarbonising electricity production, within the current demand profile, using low carbon solutions. Transport is making great strides in a multi-faceted portfolio that includes low carbon traditional fuels (through low level biofuel addition), liquid and gaseous biofuels, and electrification along with future developments of advanced biofuels and hydrogen fuel cells.

However, when it comes to heat there has been very little progress other than to state that electrification andhydrogen will provide the panacea required, without much detailed thought on how that will happen.

Ground source heat pumps work very well with reasonable ambient temperatures but when the temperatures drop, particularly in winter, they are much less efficient than in warmer climates. As a result, they will not be an obvious solution for a lot of domestic applications. Cooking will also need to switch from natural gas to electricity. Consequently, the electrical demand from heat will need to be met with new electricity generation as the current capability cannot meet the ever-growing demand.

Hydrogen is also proposed as a solution for domestic heating, but this has its own challenges. Namely that at standard room temperature and pressure it has one third the calorific value of natural gas. This means that you need to burn three times as much for the same heat output. That produces challenges for the gas transmission system in delivering those volumes, as well as for the size of boiler in the house. In addition, hydrogen being the smallest molecule, is very good at escaping through substrates and any gaps with resultant issues including embrittlement in steel, if the concentrations of hydrogen are high enough. Hence hydrogen storage vessels are made of strong carbon fibre with a polymer liner called Type IV, and are expensive in comparison to Compressed Natural Gas storage tanks. And all this is before we consider how the hydrogen is produced in a low carbon manner. The UK has some fantastic engineers capable of rising to the challenge and overcoming problems, but only if they are presented with the correct factual issues that need addressing.

Manufacturing and then transporting hydrogen raises some serious challenges that have not yet emerged at the forefront of hydrogen developments. The focus is always on the applicable use of hydrogen and its low carbon outcome, without addressing the issues of its production via a low carbon route.

To make hydrogen by electrolysis takes significant electrical energy – four times the resultant energy in the hydrogen when used in a fuel cell vehicle. Then there is the consideration of the amount of deionised water needed and the energy required to produce that. If renewable electricity is being used, then it is also important to ensure that the carbon saved from the renewable electricity is attributed directly to hydrogen and has not already been given up for general electricity grid carbon reduction. Renewable electricity is being sold to customers, without the carbon saving attached to it, and the customers think they are reducing carbon when in fact the carbon has already been attributed to the lowering of the overall electricity grid. We need proper carbon accounting and the carbon saving to follow the product to its end use, which will help to prevent double counting and misinformation.

When considering hydrogen from Steam Methane Reformation with carbon capture and storage, the same principles apply. Where is the renewable energy coming from to power the system? The carbon dioxide produced has to be captured and pressurised to 5 atmospheres below 30° C in order to liquefy it to pump offshore into old oil and gas wells. At 1 mile underground the temperature is between 80 to 100° C which will re-gasify the carbon dioxide creating increased pressure making further additions harder.

Once made, the hydrogen needs to be delivered to the point of use. In the case of fuel cell use the hydrogen has to have a purity of 99.99% and extremely low moisture content. Therefore, if it is pumped through the gas pipe network it will need to be re-purified at the filling station to meet the required specification, adding to both cost and energy use. Furthermore, transportation by road tanker is costly as there is only around 6 metric tonnes of hydrogen per tanker compared to 26 metric tonnes diesel. Trying to produce the volumes on a forecourt from scratch given the demand profile will not be possible given site land constraints (you do not see petrol refineries on forecourts!)

Finally, and perhaps of most concern, if pressurised hydrogen escapes through a crack it can self ignite. There is much to be overcome in order for hydrogen to fulfil its potential.          

If you enjoyed this blog post, and would like to learn more about hydrogen energy and net zero, register for our free online event "Will Hydrogen Technologies get us to Net Zero?" on Wednesday 24th Feburary here

Colin Matthews is managing direct of JouleVert Ltd. Colin has been involved in alternative fuels and powertrains for over 20 years, and advises technology providers, government and fleets on pragmatic solutions that deliver carbon dioxide reductions today.