The role of hydrogen in our future energy supply: benefits and limitations of a green challenge
20 December 2023
In nature it powers the stars; on Earth it represents one of the most promising energy carriers for the future. Hydrogen is now considered a strategic ally for decarbonisation, in line with the objectives of the Green Deal and the Net Zero emissions target by 2050. It is a colourless, odourless and extremely abundant gas on Earth, capable of storing and transporting clean energy.
We’re talking about hydrogen; a colourless, odourless gas, and one of the lightest and most abundant elements that make up matter.
We’ve often talked about it as part of Battery Weekly, the LIVE weekly Flash Battery programme which, every Monday at 6pm, dives into the latest news related to batteries, electrification and energy through the opinions of three industry experts: the CEO and CTO of Flash Battery, Marco Righi and Alan Pastorelli, and the President of eV Now!, Daniele Invernizzi.
Let’s take a closer look at the role of hydrogen as an energy carrier and a key resource for tackling the climate crisis. In this article, we analyse the benefits, infrastructure barriers and opportunities linked to the spread of Power-to-X technologies.
Hydrogen is one of the simplest and most abundant elements on the planet and within the solar system, making up around 90% of the visible universe, mainly in its gaseous form.
The characteristic that makes it a real alternative clean fuel is that, when combined with oxygen during combustion, it produces only water vapour as a waste product. Indeed, it is the only fuel, whether it is used in heat engines or fuel cells, that doesn’t produce polluting emissions, but simply water. This is the major difference between hydrogen and hydrocarbons which, being made up of hydrogen and carbon, release carbon dioxide and other gases that are harmful to human health and the environment when combined with oxygen during use.
However, on Earth this element is rarely available in nature in its free and molecular state (H2) because it is found almost exclusively in combination with other chemical elements, for example, in water (H20) or in hydrocarbons, comprising hydrogen and carbon (e.g. methane, CH4). Furthermore, given that hydrogen gas is highly reactive on contact with air, it is difficult to find natural sources of pure hydrogen on the Earth’s surface.
To obtain hydrogen, it must be extracted from the elements it is combined with, investing energy in the separation process. Since it is not freely available in nature, hydrogen is not a primary source but an energy carrier, able to store energy and release it when needed.
Although hydrogen is considered clean energy at its point of use, its production is not without impacts on the environment. There are currently several ways of producing hydrogen, but they don’t all have the same environmental impact, with some producing more emissions than the others.
Although hydrogen is an invisible gas, the different production technologies are identified by a colour code. This convention classifies their environmental impact and specific Carbon Intensity.
Today, there are 4 main colours associated with hydrogen, based on the production process used:
White hydrogen
So-called white hydrogen, or natural hydrogen, is found in deposits deep within the Earth’s crust and is also known as geologic hydrogen. Although potential reserves exist, economically accessible sources are not sufficient to meet global demand. Its environmental impact is not zero either: it derives from extraction methods (drilling) that are often invasive and costly.
Grey hydrogen
Grey hydrogen is obtained via steam methane reforming (SMR) or the steam reforming of other hydrocarbons. This process uses the reaction between steam and methane at very high temperatures to produce hydrogen. Currently, this method is used to produce around 48% of global hydrogen supplies. The chemical reaction involved generates carbon dioxide (CO2) as waste product, releasing on average more than 9 kg of CO2 into the atmosphere for each kg of hydrogen produced.
There is a similar production process starting from other fossil fuels, such as coal, in the case of brown hydrogen. This a well-established and widespread process which, however, generates even higher levels of CO2 emissions; around 20 kg of CO2 for each kg of hydrogen produced.
Blue hydrogen
The production process for blue hydrogen (Blue Hydrogen) derives from Grey Hydrogen, but with one substantial difference. A significant share of the CO2 generated is captured and stored underground through CCS (Carbon Capture and Storage) technologies, preventing its release into the atmosphere.
Green hydrogen
Green Hydrogen represents the highest level of sustainability. It is obtained through electrolysis, a process that uses electricity to split water (H2O) into hydrogen and oxygen. The core of the system is the electrolyser (electrolyzer technology): when powered exclusively by renewable sources, it guarantees total zero-emission hydrogen production.
Today, green hydrogen is considered a real option for decarbonisation and, in particular, given its significant potential and reduced environmental impact of its combustion, it has been identified by the European Union as a key element towards the reduction of CO2 emissions by 2050 as set out by the European Green Deal. In this regard, the EU, which is very focused on the path towards Net Zero (indeed, in 2022 the EU battery regulation was introduced ), has presented an ad-hoc strategy to encourage the use of green hydrogen in all Member States, with the aim of accelerating the production of green hydrogen from renewables.
According to the latest International Energy Agency (IEA) report, today around 75 million tonnes of hydrogen are consumed every year in the European Union, representing 2% of the total energy mix. However, it is important to underline that around 95% of production of this hydrogen is obtained via fossil fuels.
Therefore, encouraging the exclusive use of green hydrogen produced from renewable energy could make a significant contribution to reducing air emissions, positively influencing the path towards carbon neutrality by 2050, especially in Hard-to-Abate sectors.
…but there are still some problems to overcome: the cons of green hydrogen
Hydrogen is a highly reactive and flammable gas, properties that require care and controls during production, storage and transport.
At present, the lack of a widespread distribution infrastructure is slowing the large-scale adoption of this technology. During a transitional phase, this issue can be addressed by using existing connections and prioritising hydrogen use close to production sites. In the long term, however, responding effectively to market demand will require the development of a dedicated, cross-border transport network, as outlined in the vision of the European Hydrogen Backbone.
The price factor cannot be overlooked either: using hydrogen requires complex and costly systems. Facilities for producing green hydrogen are still not economically competitive (high capex) compared with traditional plants, discouraging the adoption of a greener production process.
Moving on to the technical aspects, hydrogen’s main limitation today lies in its low efficiency. This deficit is clearly represented by Round-Trip Efficiency, a parameter showing how the full energy cycle involves major losses: from production to storage and transport, through to final conversion back into usable energy.
If we imagine a line where the extremes represent environmental impact and energy efficiency, we find fossil fuels at one end (high impact, low efficiency) and renewable electricity with direct use or battery storage at the other (low impact, high efficiency). Hydrogen is located somewhere in the middle, representing a compromise between low environmental impact and low efficiency. In the case of green hydrogen obtained from sustainable energy sources, given its low environmental impact, it is positioned closer to renewable electricity.
Graph representing the efficiency and impact of various energy sources
“Renewable energy, such as that generated by solar panels and wind farms, isn’t without costs, especially in the technology production stage. Until we are completely self-sufficient through renewables, it is therefore vital to use them wisely and responsibly, avoiding waste and maximising energy efficiency. So, using green hydrogen in those sectors where batteries could meet demand is not currently the ideal solution.”
The low efficiency of hydrogen as an energy carrier is a central issue for the mobility sector, directly affecting its large-scale adoption. Looking at the Well-to-Wheel cycle, the overall energy efficiency of the hydrogen supply chain is significantly lower than more established alternatives such as battery electric vehicles (BEV).
When powered by battery, vehicles directly use the electrical energy derived from the battery. On the other hand, when hydrogen is used as the carrier, it is not used directly because it first needs to be converted into electrical energy to power the engine.
This technology, which produces electricity using hydrogen gas to power an electric motor, is based on fuel cells and is used in FCEV (Fuel Cell Electric Vehicles). In this process, energy is converted twice: first to produce hydrogen and then to produce electrical energy. With each step, there are efficiency losses: during hydrogen production via electrolysis, then during storage and transport, and finally when hydrogen is converted into electricity to power the motor.
Hydrogen-powered vehicles reach on average efficiency levels of between just 25% and 35%. For vehicles powered only by battery, on the other hand, the percentages are completely reversed: only a minimal part of the energy is lost during transport, before storage, arriving at an overall efficiency of as much as 90%.
Although the environmental benefits are almost the same, the use of green hydrogen for light road transport is less advantageous than electric power. The availability of a widespread charging network and the lower costs of charging make electrical charging cheaper than hydrogen refuelling. Electric vehicles can also benefit from the presence of established transport and distribution infrastructures, which still have to be set up in the case of hydrogen.
A further difficulty lies in the transport of hydrogen to refuelling stations to supply cars. Indeed, it is a difficult gas to handle due to its low energy density, which requires high-pressure compression (from 350 to 700 bar) for storage in sufficient quantities to refuel a vehicle.
Hydrogen and electric drive [1]
Hydrogen could play a fundamental role in the decarbonisation of Hard-to-Abate sectors, such as maritime transport, aviation and the transport of heavy goods over long distances. For these applications, battery electrification currently presents significant challenges: it would require excessively large and heavy battery packs, drastically reducing payload capacity.
Hydrogen, on the other hand, offers a more compact system and fast refuelling times. Thanks to its exceptional gravimetric energy density, it stands out as the ideal energy carrier for the Heavy-Duty sector, allowing heavy loads to be transported over long distances without compromise.
Furthermore, when the production of renewable energy leads to a surplus, another area of application where hydrogen could bring significant benefits is seasonal storage, thanks to its role as an energy carrier.
The exponential growth of electricity production from renewable sources, such as solar photovoltaics and wind power, brings with it the structural challenge of intermittency. This scenario creates the need to store excess energy generated during production peaks and make it available when demand exceeds supply. Here, a key technological distinction emerges: while daily fluctuations (short cycles) can be effectively managed using electrochemical batteries, balancing summer and winter requires Seasonal Energy Storage solutions. For this specific need, the only scalable route is underground hydrogen storage, technically known as Underground Hydrogen Storage (UHS). This technology makes it possible to store large volumes of energy produced in summer and release them during the winter months, covering the deficit caused by lower solar production.
Hydrogen is a real clean energy option and is considered a promising energy carrier for sustainable mobility in that it offers the possibility of zero emission vehicles and a solution for reducing the dependence on fossil fuels. However, despite its potential, there are still many challenges to overcome, including the reduction of production costs, the development of suitable infrastructures and resolution of the problems related to hydrogen storage and distribution.
It should be clarified that only green hydrogen, generated using clean energy from renewable sources (RES), guarantees real decarbonisation. Hydrogen produced from fossil fuels, despite its lower production costs, retains a high Carbon Footprint, negating much of the environmental benefit.
From a technological viewpoint, the low energy efficiency is a negative compared to batteries for some sectors. Therefore, it is vital to tackle the efficiency challenges of hydrogen to guarantee an effective and sustainable role of this technology in the future.
Furthermore, it is crucial to recognise that for hydrogen to play a more significant role in the transition towards more substantial energy, it is essential to improve the technology associated with fuel cells. Currently, fuel cells still face significant obstacles such as high costs, low efficiency and limited duration: all factors that negatively influence the overall usability of the hydrogen system.
IEA Net Zero Scenario 2050 [2]
Green hydrogen therefore stands out as a key energy carrier in the transition towards sustainability. Its wider adoption plays a fundamental role in the decarbonisation of Hard-to-Abate sectors, meaning energy-intensive industries that are difficult to electrify.
However, it will still represent a minority share of the energy mix we will be using by 2050, as also outlined by the ESA – European Space Agency report which, based on International Energy Agency data, shows hydrogen with a minimal percentage compared to other energy sources to be adopted in view of reaching Net Zero by 2050.
Bibliography
[1] Hydrogen and electric drive. Image taken from Volkswagen website on 03/12/23.
[2] IEA Net Zero Scenario 2050. Image taken from European Space Agency website on 20/12/23.
