Written by Tom Baxter

Visiting Professor of Chemical and Process Engineering, University of Strathclyde

Honorary Senior Lecturer, Chemical Engineering, University of Aberdeen

The EU recently produced a highly significant report addressing its strategy for delivering net zero carbon emissions by 2050 – Powering a climate-neutral economy: An EU Strategy for Energy System Integration. The strategy tackles greenhouse gas emissions by reducing the amount of energy consumed by buildings and industry, while converting many appliances that rely on fossil fuels to electrical alternatives – batteries and heat pumps. Hydrogen has a place in the EU strategy when energy efficiency and electrification are not feasible or cost effective.

A large number of organisations are touting the ‘hydrogen economy’ as key to net zero. This is typified by a recent Telegraph article: “The hydrogen revolution is a marvellous chance for Britain, if it does not throw away the prize.” Much of my 45-year career in industry and academia has been spent studying energy efficiency and power production and supply. I believe that hydrogen has a limited role in decarbonisation, and that businesses with a vested interest in promoting hydrogen are doing so at the expense of British consumers.

Hydrogen production

Hydrogen has, on the face of it, much appeal. It provides carbon-free power and heat with a by-product of water. Hydrogen can also be delivered via the existing natural gas infrastructure and stored for use when renewable wind and solar is limited, thus acting as a buffer for daily and seasonal weather-power demand variations.

It is, though, important to recognise that hydrogen, unlike natural gas, does not exist in nature – it has to be manufactured, and that requires energy. Today hydrogen is made from fossil fuel reforming. The reforming process requires a significant amount of heat and power to convert the fossil fuel into hydrogen and CO₂. To abate CO₂ production, a carbon capture and storage system (CCS) is required.

A much-touted alternative to reforming is electrolysis; here, water is cleaved into its constituent parts, hydrogen and oxygen. The cleaving process needs electrical power, and if the electrical energy comes from renewables then electrolysis delivers green, carbon-free hydrogen. However, electrolysis costs much more than reforming, so fossil-derived hydrogen with CCS will be the main route for hydrogen until electrolysis becomes cost competitive. That could be a decade or more according to the EU, and perhaps longer if natural gas prices remain low.

Hydrogen replacing natural gas

A key role proposed by the proponents of hydrogen is as a replacement of natural gas for domestic and industrial use. The UK Government’s DUKES (Digest of UK Energy Statistics) database shows the UK’s natural gas users; these would be the candidates for a natural gas to hydrogen changeout.

Domestic energy use

It is clear that the largest gas user is the domestic household. Not only that, a large portion of the natural gas used for electrical power generation is used by household electrical demand. Hence, households are the UK’s largest consumer of heat and power. Therefore, if we approach the domestic household from an energy efficiency standpoint, making households carbon neutral (no net consumer of power) would be a huge contribution to net zero.

There are no technical barriers to the carbon neutral household. It requires a combination of insulation, heat pumps, solar panels, batteries, thermal storage, and controlled ventilation. The net zero house needs no hydrogen and requires little or no upgrades to gas or electricity grids because so little electricity needs to be supplied. In cold snaps the heat pump may need to be assisted from some electrical import. Conversely, there will be times when the net zero house can deliver energy back into the grid.

Of course, the net zero house costs money, but so does the energy for hydrogen synthesis, the hydrogen synthesis plant, and hydrogen storage and distribution systems. The net zero house will outlive its owner, providing benefits for generations – a huge social and environmental positive.

The EU report repeatedly mentions the benefits of heat pumps. A heat pump requires around a quarter of the power compared to hydrogen or natural gas to heat a household, an office or a low temperature industrial process. By deploying heat pumps there is a knock-on huge benefit: the power supply side is a quarter the size of that required for producing hydrogen. Conventional cost-benefit analysis for heat pumps rarely accounts for that. It is interesting that Centrica have recently come out in support of the heat pump on cost grounds.

Electricity generation

The next largest UK gas consumer is electricity generation. Reducing gas consumption and CO₂ footprint here is clearly a role for energy efficiency and renewables: consume less power and generate electricity from carbon-free renewables – wind, solar, hydro, biofuels and geothermal. Why not use hydrogen to generate electricity using green hydrogen from electrolysis? Like renewables that would be green electricity, but would using hydrogen in a power station make sense?

Firstly, it would be very energy inefficient as significant energy losses occur at each transition – electricity to hydrogen, and hydrogen back to electricity. So that runs counter to energy efficiency at the core of a net zero transition. Because of the additional transition step, it would also be more costly. Furthermore, if hydrogen is synthesised from electrolysis it stands to reason that hydrogen per kilowatt hour will cost more than the electricity it was derived from. Move forward to a choice between hydrogen and electricity, where hydrogen costs more than electricity, and the heat pump, unlike today where electricity can cost four times as much as gas, becomes a very attractive option.

Energy storage

Hydrogen proponents like the UK Hydrogen and Fuel Cell Association say it makes sense because we can use surplus renewables, particularly wind in the UK, to make hydrogen and store it for times when renewable supply is weather curtailed. There are, though, other means for storing energy: batteries, thermal storage, phase change storage where renewable energy can be used to turn a solid into a liquid and the energy returned by changing the liquid back to a solid, biofuels where the liquid can be stored like oil, and hydro where energy is stored in elevated water. Furthermore, if we deliver on carbon neutral buildings and energy efficiency, where much less power is required, the need for energy storage is consequently minimised.

Renewable energy import/export from the continent would also be a feature for negating the need for hydrogen/energy storage. As would the steady provision of power from nuclear. Another means for minimising storage is managing supply and demand variations using a smart grid. My conclusion is that the storage issue can be addressed without the need for hydrogen.

Industrial energy use

The next largest natural gas user is ‘other industry’. Main consumers in this sector are the chemical industry, food and drink, mechanical engineering (car manufacture, etc) and mineral products. To reduce gas usage in industry, energy efficiency, electric heating and heat recovery are key. This will reduce the need for gas but there are some industrial processes which will be difficult to electrify, like cement and steel, and hydrogen may have a position here.

Commercial and public buildings energy use

‘Other final customers’ involves mainly heat for public administration buildings, factories and commercial office blocks. The discussion around net zero for households applies here too.

The upshot of the aforementioned options for decarbonising industry and domestic users means the case for hydrogen looks very weak. By embracing the EU strategy of energy efficiency and electrification, I can’t see a compelling case for hydrogen replacing natural gas for heat and power. Energy efficiency and electrification are superior long-term, cost-effective options for delivering net zero.

Transport

Turning attention to UK transport, it is the largest single source of CO₂ emissions. The UK Department of Transport report Decarbonising Transport – setting the challenge provides the following.

It clearly illustrates the importance of the passenger car. Options for decarbonising the passenger car are the hydrogen fuel cell electric vehicle (FCEV) or the battery electric vehicle (BEV). As recently reported by Volkswagen and Bloomberg, the FCEV is not favoured from cost and efficiency grounds; indeed, the hydrogen fuelled passenger car is not even mentioned in the EU report. The BEV passenger vehicle is the preferred option.

Hydrogen may be an option for long-distance heavy haulage, rail and shipping where battery size is limiting. However, biofuels look like a competing option here, and battery technology is moving apace delivering more compact systems. Who knows the future of aviation post Covid-19, but hydrogen is unlikely to be a contender. Here biofuels and hybrid battery systems look better suited.

So the upshot is, hydrogen can offer solutions for hard-to-abate parts of industry and the transport system. For the largest part of the power use side, electrification and energy efficiency look far more attractive.

Hydrogen bias

My finding is out of step with the hydrogen economy being touted by many as key to net zero in the UK. Why might that be? Perhaps the answer lies in the interests of big business. The UK All Parties Parliamentary Group of MPs and business organisations recently produced How the UK’s hydrogen sector can help support the UK’s economic recovery. This report presents a very positive spin on hydrogen and its associated benefits. However, since no other low-carbon alternatives are mentioned, the report lacks balance. It is also very biased towards use of hydrogen for domestic heating.

Considering the report sponsors, it is not surprising that hydrogen is viewed very favourably. The sponsors are businesses that have a vested interest in promoting hydrogen. Domestic gas boiler providers, gas network operators, and fossil fuel producers who know that for the foreseeable future, hydrogen will be fossil derived. Is the vested interest of business best for UK consumers?

Achieving net zero will require the wise use of a range of options. Consideration has to be given to associated downsides: recycling turbine blades and solar panels, nuclear waste, rare ore and metal extraction, land take, visual intrusion, etc. Decisions have to be evidence-based using a holistic, economic, environmental and societal sustainability analysis.