Boundaries for a global resilient energy transition

Abstract

This article discusses the challenges to a resilient energy transition. The power shortage in the Iberian Peninsula in 2025 illustrates the limitations of a resilient energy sector. To the best of our knowledge, the reason for the collapse of the Spanish electric grid has not been identified as a single system failure but was likely caused by a cascade of events that led to the instability of the grid (frequency) and the shutdown. Fortunately, the grid was restored within a day. A prolonged shortage could have had a massive impact, compromising the food supply, fresh-water supply and critical infrastructure (i.e. hospitals) for 60 million citizens since off-grid energy storage only covers short periods. Broader implementation of large energy storage could have been the key to stabilising the electric grids and preventing a shutdown. Hydrogen is promising for large energy storage to improve the safe operation/implementation of renewable energies/UNSDG7 (PV/solar/wind/hydropower) and may prevent a variation in power supply and grid stability. Considering the required scale-up for the infrastructure (UNSDG9 + 12) along with the essential role of academia/education (UNSDG4) as the fundamental keys for sustainability, these factors are limiting, and the requirements to enable a fast energy transition are alarming. Data on energy consumption and GHG emissions discussed here are exemplary for selected European countries (France/Germany/Portugal/Spain/Sweden/UK) and neighbouring Morocco/Africa. The countries’ strategies for the energy transition take into account different geographical/topological/natural/climatic limitations and opportunities. We have learnt from this blackout and previous events that the number and capacities/connectivity to neighbouring countries are crucial for blackout prevention and that implemented energy storage is important to stabilise the electric grid but remains insufficient for net-zero based on renewable energies. Islands, countries with large coastal regions or isolated countries (mountains) with limited connectivity to neighbouring grids are more sensitive to blackouts. National strategies need to consider the societal/industrial requirements to enable a net-zero transition. The assessment targets defossilisation for energy supply/transport, the requirements for the energy sector and large energy storage facilities (i.e. H₂ storage) and national infrastructures for its realisation. The goal of net-zero-by-2050 is challenged by natural resources, and delays are due to the limited infrastructure/workforce in the STEM field provided by the respective national education and academic sectors.

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Green foundation

1. The energy transition (SDG7/13) faces challenges towards a global resilient energy sector based on renewable energies. Critical aspects cover the variation of energy production with renewable energies which affects the electric grid stability and decentralised energy storage systems capable to store energy in the TWh-range to stabilise national grids and to cover electricity production gaps. We discuss the requirements for the implementation of H₂−/CCUS-based large scale energy storage systems coupled with renewable energies.

2. The critical parameters for the energy transition are limited by natural resources (SDG12), the available infrastructure (SDG9) and the workforce provided by the academic/education sector (SDG4).

3. The global concerns related to the energy transition, the negative impact on environment and climate change require actions to be taken by academia, industries, policy-makers, regulatory-entities and governments to sustain a healthy environment for all (SDG3/13–16).

Introduction

The future of modern societies relies on renewable resources as an alternative to fossil energy. To meet this goal, critical actions are needed, such as alternative energy storage solutions based on renewable resources with low CO₂ emissions.^1–6 There is no simple single answer to tackle this challenge, but it requires a portfolio of solutions well adapted to specific regional demands. For example, Portugal, Spain and Morocco are in prominent geographical situations to take advantage of energy harvesting through wind power, solar power, osmosis power plants, hydropower, tidal power stations or waste heat harvesting to produce electricity in large amounts. All these modern sustainable technologies have a single major obstacle and limitation in common: the current state-of-the-art technologies in use are not yet suitable to store large amounts of electrical energy. A remaining bottleneck for the long-term integration of renewable energies into the electrical grid is maintaining grid stability due to the variability in electricity production associated with the above-mentioned technologies. This aspect might have been involved to a certain extent in the national power shortage in Spain in April 2025; however, the cause of the system failure is not yet fully clarified. Spain is the European leader in harvesting renewable energies, with more than 50% of its national electricity mix coming from renewable sources. Its Iberian neighbour, Portugal, also covers a large part of the electricity consumption through renewable energies, and both countries have comparable, limited energy-intensive heavy industries that could consume a high energy surplus on sunny or windy days. Likewise, the large share of renewables in the energy mix may impact the electric grid with a deficit in relation to the demands. In both scenarios, it is very important to compensate for the variation (excess/deficit) through the connectivity of the continental electric grid. In the case of the Iberian Peninsula, the cross-border connectivity to the rest of Europe reached a capacity of 2%, which is significantly below the target of 10% for 2025 and 15% for 2030.⁷ In other words, the crucial cross-border connectivity to stabilise the national grid needs to be increased at least five times to fulfil the target for 2025. This is important to stabilise the baseload and frequency of the electric grid, prevent large fluctuations, and guarantee the supply for the total energy consumption.⁸ Complementary stabilisation can be achieved through battery storage systems (BESS), which may consist of metal- and gas-based energy storage, such as hydrogen or methane, for example. Both BESS approaches have advantages and disadvantages, as discussed below in this article and in related articles.^1,9,10

On April 28, 2025, the energy production in Spain reached 32 GW to cover a demand of 25 GW, while more than half was provided by solar power¹¹ and further complemented by wind power. A surplus might increase the frequency of the electric grid, and a preventive measure would be a reduction of the energy production or a disconnection of the energy supply. Interestingly, the Spanish energy production was already above 35 GW in the same year (i.e., 23–24/04/2025) with a similar high share of renewable energies in the energy mix. Therefore, an overproduction of electricity cannot be the single cause of the problem. However, around noon, grid oscillations were observed, and deviations from the standard 50 Hz frequency were recorded across the European network in the next thirty minutes in several countries. In the same timeframe, malfunctions in grid stations were observed, which subsequently resulted in a decrease in the frequency (<49 Hz), a drop in the supplied energy (>15 GW), and disconnection of regional power stations and the European grid. This frequency drop subsequently led to a supply drop from 32 GW to 17 GW, which was insufficient to cover the demands of 25 GW; consequently, it led to a system shutdown to prevent further damage to the grid. The initial energy surplus of 7 GW, later rising to 15 GW in total, vanished instantly and resulted in a deficit of 8 GW, with a demand of 25 GW. The large surplus could not be stored, nor could the deficit in the GW-range be compensated with the available battery energy storage system (BESS) of 20 MW (ref. 12) connected to the national grid. This would require BESS capacities in the GW range with approx. 10% (3.5 GW) of the maximum peak power of 35 GW to secure the total final consumption (TFC).⁸ After the blackout, it was communicated that Spain would increase the BESS capacities from approximately 20 MW to 2.5–3.5 GW (2029–2030) to support the grid stability.^13,14 It remains unclear why the solar and wind power parks in the GW range were operated for years with insufficient BESS units. This strongly indicates that the system shutdown initiated by frequency fluctuation was caused by the large gap in BESS capacities, which are to be installed over the next few years.

The role of battery energy storage systems (BESS) for grid and off-grid applications

To enable a resilient electric grid and energy storage, several parameters and aspects should be considered in terms of sustainability and resilience for the current developments and the future.^15,16 The following aspects should be considered: the UN Sustainable Development Goals (SDG)^1,2 SDG7 (clean energy), SDG9 (industrial infrastructure), SDG11 (public infrastructure) SDG12 (resources) and SDG13 (climate change), along with SDG3 (health) and SDG14–15 (environment). The technologies discussed in this perspective article also respect the Principles of Green Chemistry (PGC)^16–19 in regards to waste prevention (PGC1), high efficiency on a molecular/atomic level (PGC2), safety (PGC3–5), and energy efficiency (PGC6–7) based on a small portfolio of energy carriers (PCG8), which can be efficiently used with thermo- or electrocatalysts (PGC9) for electrochemical energy storage in a hydrogen and carbon-based circular economy (PGC10) with controlled and monitored pollution prevention (PGC11). Among these aspects, the implementation of decentralised battery energy storage systems (BESS) with high capacities in the MWh range is crucial to prevent blackouts owing to the over-/underproduction or over-/under-consumption of electricity since the electrical grid itself cannot store large amounts of electricity.¹ This is also the reason why wind parks are often standing still, owing to the lack of storage capacity and the limited grid stability. Consequently, the electric grid operators pay significant compensations to the wind park owners to turn off the wind turbines (UK: 2022; £215M), and spent £717M for gas turbine operation to compensate for the power deficit.¹ Such measures of power deficit compensation must be improved to enable the use of renewable energies and reduce the use and costs of fossil-driven gas turbines (UK: so far £500M in 2025 and estimated £8Bn until 2030).²⁰ It shows that renewable energies are not yet fully integrated into the national grid, and conventional gas turbines are still crucial for grid stabilisation. In this regard, classical electricity storage systems based on metals and electrolytes (lithium batteries; i.e. 265 Wh kg⁻¹) are not suitable owing to their low energy density and the use of limited critical raw materials (CRM) owing to the large amount of electricity produced by just a single wind turbine (2.5–3 MW) per day (up to 16 000 kWh day⁻¹). One may argue that metal-based BESS are feasible and there are convenient lithium-ion-based BESS facilities already installed in the GW-range, i.e., California with >13 GW.²¹ However, in 2024, the annual energy demand in this US state reached 251.9 TWh (terawatt-hours), on average, 690 GWh per day.²² This actually underscores that the scale-up of BESS facilities just started and the capacities are still significantly below the conservative 10% of requirements to secure the TFC.⁸ To ensure a resilient grid stability in the future based on renewable energies, California would need to scale up its BESS capacity multiple times⁸ and it is years away from reaching a more resilient electric grid. In other words, so far, the US state has managed to achieve a small share in implementing a resilient BESS infrastructure. This scale-up of BESS with metal-based batteries would require geological resources and a workforce, which are limited and hardly available right away for California, and even less on a global scale. Note that the global annual lithium carbonate production was 180 kt in 2023,²³ and to build a lithium-based BESS, one needs 62 kg of lithium per 100 kWh pack (e.g., Tesla specifications),¹i.e., 62 [kt/GWh]. Therefore, the annual global production is not sufficient to cover the demands on a global scale, or in several countries with a TFC of California. The same holds true for the countries addressed in this perspective article (installed/planned) BESS capacities: France 1.7 GW, Germany 14.5 GW, Morocco 1.6 GWh (planned), Portugal 1 GW (2030), Spain 22.5 GW (2030), Sweden 610 MW (>6 GW, 2030), UK 4.4 GW (planned >95 GW)). Thus, to avoid resource-driven geopolitical conflicts on critical raw materials, including metals required for metal-based batteries for national electric grid stabilisation, each country requires a diverse portfolio for BESS solutions rather than a single solution with one type of BESS. Note that for off-grid and individual domestic energy storage, lithium-based BESS will likely remain the state-of-the-art solution for several years. Another limiting factor of lithium-based BESS devices is the limited operation temperature range for charge and discharge cycles, which allows safe operation only between −10 °C and 40 °C.²⁴ Thus, depending on the geographical location and the temperature peaks in summer and winter, the metal-based BESS devices are not sufficiently resilient and the battery management system shuts down to avoid irreparable damage if the temperature is too low or too high. To achieve a resilient system, this aspect must be considered for design and implementation in the grid and the environment.^15,25 In general, the individual solutions are strongly dependent on the geographical, topological and climatic circumstances, and differ for each country to a certain extent.

As a consequence of the limitations of metal-based BESS facilities, the energy sector needs to implement high-capacity carbon-neutral energy storage facilities that are complementary to the already installed metal-based BESS facilities, such as hydrogen storage systems (33 kWh kg⁻¹) coupled with wind power and water electrolysers. This is even more important for regions with quite cold and very hot seasons that may lead to the malfunctioning of the BESS devices. Carbon Capture, Utilisation, and Storage (CCUS) offers promising measures in this direction, particularly for storing surplus energy harvested from sources such as wind power. This can be achieved through the production of energy- and hydrogen-rich carrier molecules such as biomethane (25 wt% H₂) and green methanol (12.5 wt% H₂) in a closed CO₂-neutral cycle as interesting measures in this direction.^1,3,9,26,27 In addition, green ammonia (NH₃, 16.7 wt% H₂) could be considered for certain energy storage applications.¹⁰ Green ammonia has an important role as a hydrogen carrier, due to its advantageous thermodynamic properties when compared with pure hydrogen. (The thermochemical transformation between NH₃ and H₂ is defined by the following chemical equation: N₂ + 3H₂ → 2NH₃; Haber Bosch process.) Thus, hydrogen storage, along with renewable hydrogen-rich molecules, will substitute fossil fuels for energy storage in the long run. Despite the average costs for green hydrogen (6.61€ per kg) produced from renewable energy being higher than the costs for grey and blue hydrogen (3.76 and 4.41€ per kg, respectively), the break-even prices for certain sub-categories of the transport sector (<5.8€ per kg for trucks), for example, are reachable through up-scaling over time.²⁸ Thus, hydrogen becomes more competitive and suitable to avoid further delays in the energy transition.

In addition to the aspects of BESS discussed above, one needs to consider the underlying aspects to enable a stable grid as part of the energy storage technology, independent of conventional metal-based batteries, hydropower or other renewable energies coupled with hydrogen storage to stabilise the grid. In particular, for a better integration of BESS and renewable energies, this requires automated energy monitoring regarding production and consumption, and a battery management system to avoid failures caused by deep discharges or overcharging, seasonal variation (i.e., PV) of the corresponding battery connected to renewable energy production and consumption.^24,29–32 These aspects, as part of grid-enhanced technologies (GET),^{30,31,33–35} are important to consider as additional hardware and software infrastructure for national and micro-grids,^{30,31,33–40} off-grid and e-mobility^29,33,41 and other applications in general for long and short-term energy storage.^{8,31,38,42–44} This applies to classical metal-based BESS systems and also to the integration of hydrogen/LOHC-based BESS coupled with electrolysers and fuel cell-coupled or renewable energies.^{35,36,38,45,46} Thus, a corresponding infrastructure for digital monitoring and management must be further developed and implemented in parallel, equally for centralised and decentralised grid and battery management, which must be resilient also in terms of the cybersecurity of power systems^30,37,44 to avoid malfunction caused by cyber attacks, and transmission delays due to the limited capacities of centralised web servers. With this underlying infrastructure in place, renewable energies and BESS will be enabled for a resilient integration into the grids, and overcharging or deep discharges leading to grid instability can be avoided. Thus, these operating technologies are equally as important as high-capacity energy storage systems for a resilient grid connected to renewable energies.

Discussion

Greenhouse gas emissions (GHG)

For the energy transition one needs to consider the demands of a society that is still largely based in total on CO₂-emitting technologies with significant greenhouse gas (GHG) emissions for the respective countries and per capita (Fig. 1). Note that the GHG emissions (CO₂-equivalents) also include the shares of the greenhouse gases methane, nitrous oxide and fluorinated gases (F-gases), with carbon dioxide as major contributor (Fig. 2).⁴⁷ Albeit the global GHG emissions increased by >60% between 1990 and 2023, one needs to consider that on the one hand, the growth of the global population increased by >50% in the same timeframe, and on the other hand, the global standard of living improved and became more energy intensive, as indicated by the significant emission growth of the energy, industrial and transportation sectors (all >70%). This is also reflected in the ongoing globalisation and the related GHG emissions for the transportation of goods, commodities and passengers (including shipping and aviation).

Fig. 1 (Top left) Selected greenhouse gas emissions (GHG, megatons of CO₂ equivalents). (Top right) GHG emissions per capita. (Bottom) Change in GHG emissions. PT = Portugal, DE = Germany, SE = Sweden, FR = France incl. Monaco, ES = Spain incl. Andorra, MO = Morocco. Data derived from the Climate Action Progress Report 2023 of the European Commission and the JRC Science for Policy Report GHG Emissions of all World Countries, 2024.^47,48

Fig. 2 Shares of GHG emissions. Data derived from the Climate Action Progress Report 2023 of the European Commission and the JRC Science for Policy Report GHG Emissions of all World Countries 2024.^47,48

The global emissions per capita remained roughly stable between 1990 and 2023, and in the EU and the selected countries, the GHG emissions improved to a different extent.⁴⁷ The less intensive reduction of the GHG emissions in Portugal is related to the significant growth of the transport sector (GHG + 62%) as a consequence of the significant economic growth and improvement of the standard of living of the country in the same timeframe. Notably, despite the successful economic growth, the GHG emissions of Portugal remained significantly below the global and EU average in 1990 and 2023. In contrast, the European average per capita and more industrialised countries like France, Germany, Sweden and the UK were above the global average in 1990 but significantly reduced the GHG emissions per capita (47%–49%). Nonetheless, Germany, the industrialised powerhouse (8.8 t CO₂-eq. per year per capita), remains above the global average (6.5 t CO₂-eq. per year per capita). Spain also reduced the emissions per capita (−18%) and its current GHG emissions (6.2 t CO₂-eq. per year) are slightly below the global average per capita.

Similar to Portugal, Morocco significantly improved the economic growth and standard of living in the country in the same timeframe and the GHG emissions per capita of Morocco have been significantly below the global average with 1.7 t (1990) and 2.8 t-CO₂-eq. per year (2023). The GHG emissions have the highest impacts on the energy industry and transportation sector; the latter still requires the most efforts for the prospective energy transition related to the current fossil-based technologies in use for transportation. The building, agriculture and waste sectors improved in the respective countries, and their shares play a minor role in comparison to the sectors mentioned above. Thus, the ongoing energy transition requires further efforts to implement technologies that enable the production and utilisation of renewable energies for electricity production and consumption through the national electric grids (energy sector), implementation of carbon capture technologies in CO₂-emitting industries (industrial sector), and energy storage systems suitable for mobility (transportation sector).

Energy consumption

To determine the possible complementary solutions and substitution of the respective technologies used in each sector, one needs to consider the levels of energy consumption (Table 1). For all countries except Sweden, the shares of fossil energies remain the major energy for the total final energy consumption (TFC) of >60%, while Sweden is already <25% (Table 1, entries 1 and 2). Note that for Sweden and France, a significant amount (25% and 40%, respectively) of the electrical energy mix is derived from nuclear power. The renewable energies complement the conventional energy consumption in Portugal and Germany with roughly a quarter, while in Sweden, the renewable energies already surpass the fossil energies by >100% (Table 1, entry 3). The largest shares of the TFC are covered by the transport and industry sector in all countries with >60% (Table 1, entries 4–6), while the residential and services (commercial and non-commercial) sectors are responsible for the rest of the TFC (Table 1). Note, the largest energy-consuming sectors are also still the largest fossil source consumers and therefore, the largest GHG emitters. To reach net-zero emissions in these countries, a decarbonisation of the energy, industrial, and transportation sectors is crucial; therefore, the fossil energy share of the TFC should be fully replaced by renewable energies (Table 1, entry 8). This implies that, for example, the renewable energy sector in Portugal needs to be tripled, and respectively quadrupled in France, Germany, Spain and the UK. In Sweden, the share still needs to be doubled if Sweden plans to retire the nuclear power plants; otherwise, an increase of approximately 50% would be sufficient to substitute fossil energies in that country. The share of nuclear power in France and the possible future retirement would require additional installations of renewable energies. For Morocco, the share of renewable energies in the energy mix is so far about 8%, and the major share (>90%) is fossil energies, but the geographical location is likewise promising to implement solar and wind power. The timeframe for the installation of the required renewable energy technologies (i.e., wind power, PV, water, tidal/wave power, osmosis) is difficult to estimate on such a large scale, but the limiting factors are diverse, including raw materials, automated production, construction, installation, workforce, and existing infrastructure. A bottleneck of the current national electric grids is that renewable energies require additional energy storage entities to guarantee grid stability for the baseload of the grid (vide supra); therefore, high-capacity energy storage systems are required. In this regard, it has been estimated that such energy storage systems should be able to store about 10% of the consumed electricity,⁸ and mobile energy storage systems for transportation will also be required. Therefore, one needs to consider at least 10% of the TFC for electric grid stability for prolonged periods with renewable energies as the exclusive source (Table 1, entry 9). For long-term energy storage on the TWh-scale, it would require the implementation of H₂-production and storage capacities in the megaton scale if metal-based batteries only take a minor share owing to the low energy storage capacity (Table 1; entry 10). These hydrogen production facilities would consequently need to be installed along with water purification and supply facilities to deliver pure water on the megaton scale, which is required to enhance the lifetime of the electrodes (Table 1, entry 11). The energy storage could be further improved through CCUS and DAC (direct air capture of CO₂) to enable energy storage in the form of methanol (CO₂ + 3H₂ ↔ CH₃OH + H₂O) and methane (CO₂ + 4H₂ ↔ CH₄ + 2H₂O; methanation; Sabatier reaction), for example. Likely, the coastal regions in the discussed countries are prominent for these facilities through combining renewable energy harvesting and water electrolysis.

Table 1 Total final energy consumption (TFC), shares and demands

Entry	TFC, shares and demands	Unit	Portugal	Germany	Sweden	France	Spain	UK	Morocco
Entries 1–7: Data derived from the International Energy Agency Energy Policy Country Reviews.^49–55 Where applicable: 1 MTOE (megaton of oil equivalents) = 11.63 TWh; 1 TOE = 11.63 MWh; 1 exajoule = 277.78 TWh. Entry 8: eq. of fossil energy; entry 9: calculated from the TFC based on the estimated 10% for the daily requirement for grid-stability,^8 entry 10: considers the energy density of hydrogen as 33.3 kWh kg^−1, entry 11: considers the minimum equivalent amount of water for the hydrogen amount required, entries 12 and 13: derived from the European Hydrogen Market Landscape,^28 entry 14: derived from entries 10 and 13, and entries 15–16 estimated from the typical annual capacity of a 100 MW PEM electrolyser to produce 15 kt per year of green hydrogen.^1 Entry 18: data derived from ref. 47.a Planned for 2030: 2–2.5 GW.^4b Planned for 2030: 10 GW.^4,56c Planned for 2030: 5 GW.^4
1	TFC	TWh	195	2640	333	1746	994	1268	190
2	Fossil energy	TWh	141	2112	80	1123	685	976	139
3	Renewable energies	TWh	51	491	172	226	160	203	15
4	Transport + industry combined share	TWh	136	1595	207	1060	666	761	127
5	Transport share	TWh	69	671	73	529	378	456	82
6	Industry share	TWh	67	924	133	531	288	304	45
7	Buildings share (residential and services)	TWh	59	1048	127	686	328	520	63
8	Increase in renewable energy for future requirements for total net zero	TWh	144	2149	161	1520	834	1065	175
9	10% storage capacity of the TFC	TWh	20	263	33	175	99	127	19
10	Annual green H2 demand-10% storage capacity of TFC (+transport sector)	Mt	0.59 (+2.1)	7.93 (+20.1)	1.00 (+2.2)	5.2 (+15.9)	3.0 (+11.4)	3.8 (+13.7)	0.6 (+2.5)
11	Water requirement (+transport sector)	Mt	5.3 (+18.9)	71.3 (+180.9)	9.0 (+19.8)	47.2 (+143.1)	26.9 (+102.6)	34.3 (+123.3)	5.1 (+22.2)
12	Total current H2 production capacity	Mt	0.12	1.98	0.22	0.92	0.76	0.63	0
13	Conventional H2 demand by country/end-use	Mt	0.11	1.38	0.16	0.54	0.57	0.47	0
14	Total future demand (convent. + 10% storage capacity of TFC); (+transport sector; sum)	Mt	0.70 (2.80)	9.31 (29.4)	1.16 (3.36)	5.79 (21.8)	3.55 (15.0)	4.28 (18.0)	0.6 (3.1)
15	Required water electrolyser capacity (ref. entry 10)	GW	3.9^a (+14.0)	52.9^b (+134.0)	6.7^c (+14.7)	34.7 (+106)	20.0 (+76.0)	25.3 (+91.3)	4.0 (16.7)
16	Total future demand: water electrolyser capacity (ref. entry 14; sum)	GW	4.7 (18.7)	62.0 (196.0)	7.7 (22.4)	38.6 (145.3)	23.7 (100.0)	28.5 (120.0)	4.0 (20.7)
17	Energy consumption per capita [MWh]	MWh	18.6	41.9	55.8	25.9	20.9	22.1	5.2
18	GHG emissions per capita [t CO2-eq]	t	5.2	8.2	4.8	5.8	6.2	5.5	2.8
19	GHG emissions per capita and MWh [kg CO2-eq per MWh]	kg MWh^−1	279	196	86	224	296	249	535

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In addition, one would need to consider the already existing hydrogen demands for conventional use in industries, such as the utilisation in the refining sector (58%), the Haber–Bosch process (25%) for fertilizer production, methanol (2%) and many other bulk chemicals (9%), which are still mainly fed by hydrogen produced from fossil sources (Table 1, entries 12 and 13). For the realisation of the production of the total future hydrogen demands through water electrolysers run by renewable energies, it requires the installation of several water electrolyser facilities in the GW range (Table 1, entries 15 and 16) in all countries. The major share in all countries would be required for the transportation sector and only a minor part for the electric grid and conventional hydrogen use. The annual operational electrolyser manufacturing capacity in Europe was approximately 5.4 GW per year in May 2024 and will likely reach 10.5 GW per year in 2026.²⁸

Thus, just to cover the conservative estimates for the 10% TFC shares of these countries with water electrolysers it would require more than ten years for the manufacture of the electrolysers (169.2 GW; sum of entry 16 in Table 1), and this shows a bottleneck in terms of manufacturing capacities for the European Union and other European countries, taking into account the targets for 2050 (adoption of a net-zero scenario). This also shows that an energy mix for mobile energy storage with metal-based batteries is necessary during the Energy Transition because additional facilities and capacities to feed the transportation sector with hydrogen (Table 1, entry 16) are not readily available in the near future for these countries or the EU and the whole of Europe or globally. Therefore, an energy mix will likely be inevitable for the transportation sector for a prolonged period of time. Last, but not least, the energy consumption and GHG emissions per capita (Table 1, entries 17–19) show a significant variation, which is related to the energy mix in the respective countries, but also related to the regional climate. The values for GHG per MWh per capita (entry 19, Table 1) show that the share of fossil energies is more pronounced for certain countries, and also the energy consumption per capita is higher owing to regional demands, such as heating.

Potential measures and further requirements

To overcome the limitations of grid stability, the countries require improvement of the cross-border connectivity, and the implementation of technologies to stabilise the grid frequency, thus compensating for excesses and deficits of power in local, regional and national grids. In this regard, energy storage through green H₂, green NH₃, CO₂-derived CH₄, and green CH₃OH comes into play. To enable this, for the manufacturing capacities of water electrolysers for the required hydrogen production, it is crucial to reduce costs and scale up the automated production of electrolysers, which is still limited in industries. More precisely, the hydrogen sector, in partnership with the renewable energy sector, needs to recruit more qualified workers for the production, installation, maintenance and operation of the water electrolysers, hydrogen storage facilities, water purification systems, fuel cells, and the whole infrastructure, including a hydrogen-fit national gas-grid (i.e., safety, leakage, pressure).⁶ In addition, as indicated above, the renewable energy sector (i.e., wind power, PV, osmosis or tidal/wave power, along with the BESS and GET infrastructures) will also need to extend the workforce to achieve the goals to substitute fossil energies with renewable energies as discussed above.

This upscaling of the infrastructure is a potential bottleneck since the education sector needs to increase the number of STEM students and vocational trainees in the respective fields to satisfy the future demands for the renewable energy sector (globally: 37.8M in 2030 and 43.4M in 2050) and parts of the hydrogen sector (globally: 2M),⁵⁷ with additional and similar demands along the supply chain. Note that these numbers are likely underestimated for a net-zero scenario since it considers that in 2030 and 2050, a large share of the total energy sector will work in the sub-share of fossil fuels (Fig. 3). Likewise, a net-zero scenario implies a significantly higher demand for the renewable energy sector and the hydrogen sector. Albeit, the total numbers of STEM students in, for example, Portugal, Germany, and Sweden are relatively high and well developed (a little below 1/3 of all enrolled students; equiv. to approx. 130k of 448k and 26k graduates per year in Portugal),^58,59 and only a share (i.e., engineering, chemistry, physics) would fit into the respective sectors. The specific demands are higher for the realisation of a timely implementation of a new infrastructure. Similarly, in Germany, with 2.9M enrolled students and 1M in the STEM field, yielding approximately 200k graduates per year for the German market, with about 500k vacant positions in the STEM field, and in 2022, 50k vacant positions were filled in the renewable energy sector only. The share of enrolled STEM students in Sweden in 2023 was 143k out of 383k. In Spain, the number of STEM students is roughly a quarter (23%) of all enrolled students, while in France, close to a third (29%), and in the UK, approximately 45%.^60,61 These numbers of enrolled students have been fairly stable with a sliding increase for over a decade also owing to the increasing number of female students in these fields.^62,63 However, not all STEM students will work in the corresponding sectors; thus, it will be challenging to upscale the current infrastructure to achieve the complete substitution of fossil energies by renewable energies (Table 1, entry 8) in a few years from now. To accelerate this progress, for the next decades, more STEM students and vocational trainees are required, and a further increase in the still underrepresented gender in the related STEM fields is needed. Moreover, it would require an increase in the budget in the educational sector, including the human resources budget, and also more perspectives already need to be indicated at the pre-university level in school through teachers and at home by the parents of the future students and employees. In this regard, more outreach activities at the universities must be implemented to enable a better promotion of the STEM subjects at schools and on campus. Additionally, the role of research centres, national laboratories, and research societies dedicated to applied research in these sectors needs to be emphasised. This applies not only to the countries discussed herein and their research infrastructure,⁶⁴ but to all countries globally. This will enable more collaboration between academia and the energy and industrial sectors for the faster development and implementation of the required technologies for the energy transition, and likewise the hands-on training of the required future employees in these fields on a national and international level through the collaborations of the above-mentioned R&D entities. In addition to the reinforcement of the educational sector, further measures for the realisation of the energy transition are required for the regulation and certification of these technologies, along with robust policies for implementation nationwide. The latter will also positively impact the socio-economic and societal developments for less developed regions and vulnerable communities with more limited access to modern infrastructure and access to clean energy in these countries and globally. The recent blackout in the Iberian Peninsula has demonstrated on a large scale the limited resilience of the energy system in a well-developed region of the planet, and the requirements for a resilient infrastructure based on The Proposed Ten Principles of Resilient Chemistry, which are of global relevance.¹⁵ The history of major blackouts in this century showed that such events may occur in developed regions (including Europe, North America, Australia), and also regions with more sensitive national infrastructure under development. Interestingly, independent of the region, one limiting factor played a role, in addition to energy storage systems, and this is apparently related to the limited number of neighbouring countries with cross-border connectivity. Thus, coastal countries, peninsulas, and islands are more sensitive and less resilient to such scenarios, and therefore, energy storage systems are important parts of the local resilient infrastructure, which still needs to be improved globally.

Fig. 3 The figure is reproduced from ref. 57 under open access policies from IRENA and the ILO (2021), Renewable Energy and Jobs–Annual Review 2021, International Renewable Energy Agency, International Labour Organization, Abu Dhabi and Geneva, copyright 2021 (ISBN: 978-92-9260-364-9).

Conclusion and outlook

In summary, for a complete replacement of fossil fuels by renewable energies, the infrastructure for energy harvesting through renewable energy technologies requires a substantial scale-up of the current available infrastructure. It requires the implementation of large-scale energy storage facilities and cross-border connectivity, along with a resilient underlying infrastructure to enable robust energy storage management, and monitored energy production and consumption to ensure the electric grid stability for the conventional electricity-consuming sectors. The significant cost of running gas turbines while wind parks are standing still has shown the problem for many years, and such facilities should be used to produce hydrogen, likely coupled with DAC/CCUS to feed fuel cells and gas turbines, if necessary, during the Energy Transition. In addition to this, further capacities are required to enable a defossilisation of the transport sector, which is likewise one of the major remaining GHG emitters. Considering the total required energy storage capacities (10% of the TFC) for the electric grid stability, together with the transport sector, the annual amount of hydrogen and the electrolyser capacity are multiple times higher than the current hydrogen storage and total BESS capacities. Notably, conventional metal-based BESS facilities are currently not well-suited for large-scale global deployment due to the insufficient availability of geological resources and the limited manufacturing infrastructures. In addition, their operational temperature range represents a further constraint, particularly in very cold or hot regions. To enable a scale-up for a complete modernisation of the energy sector to resilient renewable energies, the major obstacles are related to the automated production of the technologies and the required qualified workforce to install, operate, and maintain the whole infrastructure. Therefore, countries need to educate significantly more STEM students and vocational trainees in the renewable energy and hydrogen sector to enable the scale-up of the infrastructure for the crucial energy transition, which is of utmost importance to prevent further collateral damage caused by GHG emissions and to preserve societies for future generations.

Author contributions

Concept: MHGP; data interpretation: all authors; writing – original draft: MHGP; and writing, review & editing: all authors.

Conflicts of interest

There are no conflicts to declare.

Data availability

All data included in this article is based on original data which is available through the cited literature in the references.

Acknowledgements

Authors thank FCT for the projects 2022.02069.PTDC (https://doi.org/10.54499/2022.02069.PTDC) and EXPL/QUI-QOR/1079/2021, (https://doi.org/10.54499/EXPL/QUI-QOR/1079/2021) at the Centro de Química Estrutural, the Deutsche Forschungsgemeinschaft (DFG 411475421), and the Centro de Química Estrutural/Institute of Molecular Sciences. The authors are grateful to the Instituto Politécnico de Lisboa for the IPL/IDI&CA2023/SMARTCAT_ISEL project. The COST Actions CYPHER (CA22151) and TransformERS (CA22156) are acknowledged for further support.

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