Posted on

Smart fuel cells catalyzed by self-adjusting anodes improve water management

Hydrogen fuel cells are often regarded as a key element in the green energy transition. Their efficiency is double the thermochemical energy conversion of internal combustion engines. Hydrogen fuel cells convert the chemical energy of hydrogen and oxygen directly into electricity and water. Hence, water plays a central role in fuel cells. It supports ion transport and participates is product of the reaction itself. In an anion exchange membrane fuel cell (AEMFC), for the oxygen reduction reaction to take place, the water in the anode catalyst layer (ACL) must diffuse to the cathode catalyst layer (CCL). In summary, water management is required to remove water from the ACL for higher efficiency of hydrogen diffusion and to balance the water in the entire membrane electrode assembly (MEA).

Significant research efforts have been made to achieve conditions that is suitable for both the anode and cathode in AEMFC. Asymmetric humidification of reactant gases was proposed to be beneficial to achieve well equilibrated water balance between the two electrodes. At higher temperatures, excess anode water evaporates. It also causes deficiencies at the cathode which also requires water to function. To counteract this, a new system that controls the back pressure at the anode and cathode was introduced. However, external control mechanisms (active control) increase the complexity of the system control.

This is where a passive control system involving MEA modification comes into the picture. Moisture control in a fuel cells can be achieved by designing a suitable gas diffusion layer. Adopting different types of hydrophobic materials for the anode and hydrophilic for the cathode can improve overall fuel cell performance. Poly ethylene tetrafluoroethylene (PTFE) copolymer ion exchange membranes, such as Nafion™ have high water mobility. This property can help water back diffusion to avoid anode flooding while preventing dehydration of the cathode. Designing a gradient microstructure or ionomer content within the CCL could also be useful to improve cell performance and durability.

Recent research published in the journal Cell Reports Physical Science addresses these questions. The presented study was carried out to assess a multi-layer CCL design with the gradient capillary force which has a driving effect on water to solve the water balance problem of anodes in AEMFC. For the purpose of the study, platinum on carbon and platinum-ruthenium on carbon were selected as anode catalysts. Ruthenium increases the hydrogen oxidation reaction activity and possesses beneficial structural properties. Water management and performance of AEMFC would be influenced by the structure of the ACL.

Microstructure analysis of ACLs

ACLs composed of different layers of Pt/C and PtRu/C and a mixed version with a similar thickness of around 9-10 µm were analyzed with energy-dispersive X-ray spectroscopy (EDX).

Pt/C ACL had pores of less than 150 nm while PtRu/C catalysts pores ranged between 300-400 nm. The mixed ACL had a pore size <200 nm.

The researchers concluded that Pt/C and PtRu/C ACL had a stratified and gradient pore size distribution spanning across the anion exchange membrane and the gas diffusion layer. The mixed ACL, however, had a homogenous pore structure throughout the MEA.

Membrane electrode assembly using a polymer electrolyte membrane

Moisture adsorption and desorption behavior of ACLs

To investigate moisture adsorption and desorption, the change of the fuel cell’s moisture content was checked with regards to different levels of relative humidity.

It was observed that the moisture content level increased by up to 50% mass weight along with an increase in relative humidity from 20% to 80%.

With an extended equilibrium time for a relative humidity of 80%, the moisture content of Pt/PtRu and PtRu/Pt ACL began to decrease. This was evidence for the self-adjusting water management behavior.

Desorption at a relative humidity of 60% was done. The water content in ACL showed rapid adsorption and slow-release properties at each relative humidity setting.

Physical adjustment of water behavior was observed in PtRu/Pt ACLs. This was attributed to gradient nano-pores and promoted water transport when water was generated within the ACLs during the electrochemical reactions. It would facilitate fuel cells operation at high current density.

Fuel cell performance of ACLs

To assess the structural effect on water management during operation, fuel cell performance was investigated at different relative humidity and temperature levels.

With increasing relative humidity from 40% to 80%, an increase of the maximum power density was observed as well while the temperature remained constant at 50°C. This was due to higher ionic conductivity at high membrane hydration.

At relative humidity of 100%, a maximum power density of the Pt/PtRu MEA and the mixed MEA decreased, however. The inverted MEA version using PtRu/Pt an increase to 243 mW/cm2 was observed. This suggested that the moisture desorption ability of PtRu/Pt MEA promoted mass transfer during fuel cell operation.

At a temperature of 60°C and 100% relative humidity, the maximum power density of PtRu/Pt reached 252 mW/cm2.

A durability test was conducted for PtRu/Pt MEA. It showed that after continuous operation for more than 16 hours at 100 mA/cm2 the voltage drop was <4%.

Conclusion

It became clear from the tests that the PtRu/Pt anode catalyst layer with its homogenous layer had a better self-adjustment capability for fuel cell water management. The gradient nanopore structure of the catalyst layer made it possible to transport water through the capillary effect. Excess water at the anode could either be transported towards the cathode where it would be used for reaction or towards the gas diffusion layer for its removal prevented flooding. Moreover, this catalyst layer made from PtRu/Pt showed better performance abilities too.

At Frontis Energy we think that this could resolve the issues faced with water management in the fuel cells. Since it is a passive control system that involves modifying the design of the fuel cells internally, intricate external systems could be replaced or complemented. The study certainly helps future fuel cell automation as an interesting new aspect of fuel cell design was discovered that could make them smarter.

Reference: Self-adjusting anode catalyst layer for smart water management in anion exchange membrane fuel cells, Cell Reports Physical Science, Volume 2, Issue 3, 24 March 2021, 100377

Posted on

Highly durable platinum-palladium-based alloy electrocatalyst for PEM fuel cells

To decrease the consumption of fossil fuel-derived energy for transportation, proton exchange membrane fuel cells (PEMFCs) are one of the most promising clean power sources. Their performance, however, strongly depends on the efficiency and durability of the electrocatalyst used for the hydrogen and oxygen reactions occurring at the electrodes. Noble metals such as platinum and gold are still considered as the most efficient catalysts. At the same time, their high cost and scarcity are major road blocks for scale commercialization of these energy devices.

Various solutions of catalyst design are intensively investigated in order to make this technology economically successful. Searching for high catalyst activity and durability for fuel cells is in focus of current research and development. To date, state-of-the-art electrocatalysts are based on carbon materials with varying platinum loadings.

Ultra-high active platinum group metal (PGM) alloy catalyst

Although, recent research reported ultra-high activity of some metal alloy catalysts, problems still remain. Some of these issues are related to utilization of high atomic percentages of PGM (sometimes up to 75% Pt), poor durability and performance under industrial conditions. In search for new solutions, researchers of the State University of New York at Binghamton, USA, and their collaborators reported a new design in journal Nature Communication: a highly-durable alloy catalyst was obtained by alloying platinum and palladium at less than 50% with 3d-transition metals (Cu, Ni or Co) in ternary compositions.

They addressed the problem of severe de-alloying of conventional alloy catalysts under the operating conditions, resulting in declining performance. For the first time, dynamic re-alloying as a way to self-healing catalysts under realistic operating conditions has been demonstrated to improve fuel cell durability.

Alloy combination and composition

The wet-chemical method was used for synthesis of Pt20PdnCu80−n alloy nanoparticles with the desired platinum, palladium and copper percentages. The selected set of ternary alloy nanoparticles with tunable alloy combinations and compositions, contained a total content of platinum and palladium of less than 50%, keeping it lower than current PGM-based alloy catalysts. The incorporation of palladium into platinum nanomaterials enabled a lower degree of de-alloying and therefore better stability. Additionally, palladium is a good metal partner to platinum due to their catalytic synergy and their resistance to acid corrosion.

To reduce the need for platinum and palladium core catalysts, a third, non-noble transition metal played a central role in the catalytic synergy of alloying formation. Non-noble metals such as copper, cobalt, nickel or similar were used. The platinum-palladium alloy with base metals allowed the researchers to fine tune the thermodynamic stability of the catalysts.

Morphology and phase structure

The thermochemical treatment of carbon-supported nanoparticles was crucial for the structural optimization. The metal atoms in the catalytic nanoparticles were loosely packed with an expanded lattice constant. The oxidative and reductive treatments of the platinum-palladium alloy (PGM <50%) allowed a thermodynamically stable state in terms of alloying, re-alloying and lattice strains. The re-alloying process not only homogenized the inhomogeneous composition by inter-diffusion upon calcination of nanoparticles, but also provided an effective pathway for self-healing following de-alloying.

Single face-centered cubic type structures were observed in Pt20PdnCu80–n nanoparticles (n = 20, 40, 60, 80) nanoalloys. Copper-doping of platinum-palladium alloys reduced the lattice constant effectively, as shown by high energy X-ray diffraction. Maximized compressive strain and maximized activity of the Pt20Pd20Cu60 catalyst confirmed strong correlation between the lattice constants and the oxygen reduction activity.

The researchers demonstrated that the thermodynamically-stable Pt20Pd20Cu60/C catalyst exhibited not only the largest compressive strain after 20,000 cycles, but also high activity and high durability. The discovery that the alloy catalyst remains alloyed under fuel cell operating condition is in sharp contrast to the fully de-alloyed or phase-segregated platinum skin or platinum shell catalysts reported in almost all current literature.

The significance in understanding of the thermodynamic stability of the catalyst system is a potential paradigm shift of design, preparation, and processing of alloy electrocatalysts.

(Photo: Pixabay)

 

Posted on

Rechargeable PEM fuel cell with hydrogen storage polymer

Energy-converting devices such as fuel cells are among the most efficient and clean alternative energy-producing sources. They have the potential to replace fossil-fuel-based power generators. More specifically, proton exchange membrane fuel cells (PEMFCs) are promising energy conversion devices for residential, transportation and portable applications owing to their high power density and efficiency at low operating temperatures (ca. 60–80 °C). For the complete approach, with electrolytic hydrogen renewable sources, PEM fuel cells can become one of the cleanest energy carriers. This is because water is the final product of such energy conversion systems. Currently, Nafion™ membranes are regularly used as hydrogen barriers in these fuel cells.

A Proton exchange membrane

Sufficient hydrogen gas supply is crucial for practical application of the PEMFC systems. Currently, expensive high-pressure tanks (70 MPa) are state-of-the-art for hydrogen storage. Besides cost, there are other drawbacks such as portability and safety. In order to address these issues, alternative hydrogen storage materials have been extensively investigated. For example, metal hydrides and organic hydride materials, can fix and release hydrogen via covalent bonding.

Now, Dr. Junpei Miyake and colleagues of the University of Yamanashi, Japan, have proposed an “all-polymer” rechargeable PEMFC system (RCFC). The work has been published in Nature Communications Chemistry. Their strategy was to apply a hydrogen-storage polymer (HSP) sheet (a solid-state organic hydride) as a hydrogen-storage medium inside the fuel cell. With this approach, the issues like toxicity, flammability and volatility as well as concerns related to other components such as the fuel reservoir, feed pump and vaporizer were solved. The HSP structure is based on fluorenol/fluorenone groups that take over hydrogen-storage functionality.

In order to test the performance of their HSP-based rechargeable fuel cell, the scientists attached the HSP sheet of the membrane electrode to the catalyst layer of the anode. At the same time, the cathode side was operated as in a regular PEMFC. The researchers reported that an iridium catalyst has been applied to the inside of the HSP sheet to improve the hydrogen-releasing and fixing processes.

Fuel cell operation, cycle performance and durability were tested using cycles of 6 periodic steps. At first, hydrogen was infused into HSP sheet for 2 h, followed by nitrogen gas flushing to remove hydrogen from the anode. Then, heating of the cell up to 80°C to initiated hydrogen release from the HSP sheet. Together with oxygen gas supplied to the cathode side the fuel cell produced constant electrical current.

The team demonstrated that their HSP sheet released 20%, 33%, 51%, or 96% of the total fixed hydrogen gas in 20, 30, 60, or 360 min, respectively. The temperature was 80°C in the presence of the iridium catalyst. Also, the iridium catalyst could absorb up to 58 mol% hydrogen, which was considerably lower than that stored in the HSP. The maximum operation time was approximately 10.2 s / mgHSP (ca. 509 s for 50 mg of HSP) at a constant current density of 1 mA / cm2. The RCFCs reached cycleability of least 50 cycles. In addition, the utilization of a gas impermeable sulfonated poly-phenylene membrane (SPP-QP, another type of PEM) turned out to be a good strategy to enhance the opration time of the RCFC.

The advantageous features of the reported RCFC system include better safety, easier handling and lower weight. These are perfect for example in mobile application such as fuel cell vehicles. However, for the improvement of the RCFC performance, hydrogen storage capacity and kinetics (H2-releasing/fixing reactions) as well as catalyst stability need further improvements.

Posted on

Reverse electrodialysis using Nafion™ membranes to produce renewable energy

In the order to address the global need for renewable and clean energy sources, salinity-gradient energy harvested by reverse electrodialysis (RED) is attracting significant interest in recent years. In addition, brine solution coming from seawater desalination is currently considered as a waste; however thanks to its high salinity it can be exploited as a valuable resource to feed RED. RED is an engineered adaptation of nature’s osmotic energy production where ions flow pass the cell membrane in order to produce the universal biological currency ATP. This energy is also harvested by the RED technology.

Now, more than ever there is need for sustainable and environmentally friendly technological solutions in order to keep up with ever growing demand for clean water and energy. The traditional linear way “produce and throw away” does no longer serve the society anymore and the new approach of circular economy has take a place, where any waste can be considered as a valuable resource for another process. In this respect, reverse electrodialysis is a promising electromembrane-based technology to generate power from concentrated solutions by harvesting the Gibbs free energy of mixing the solutions with different salinity. In particular, brine solutions produced in desalination plants, which is currently considered as a waste, can be used as concentrated streams in RED stack.

Avci et al. of the University of Calabria, Italy, have recently published their solution for brine disposal using RED-stack. They have realized that in order to maximize generated power, the high permselectivity and ion conductivity of membrane components in RED are essential. Although Nafion™ membranes are among the most prominent commercial cation exchange membrane solutions for electrochemical applications, no study has been done in its utilization toward RED processes. This was the first reported RED stack using Nafion™ membranes.

A typical RED unit is similar to an electrodialysis (ED) unit, which is a commercialized technology. ED uses a feed solution and the electrical energy, while producing concentrate and dilute, separately. On the other side, RED uses concentrated and dilute solutions that are mixed together in a controlled manner in order to produce spontaneously electrical energy. In a RED stack, repeating cells comprised of alternating cation and anion exchange membranes that are selective for anions and cations. The salinity gradient over each ion exchange membrane creates a voltage difference which is the driving force for the process. The ion exchange membranes are one of the most important components of a RED stack.

The performance of Nafion™ membranes (Nafion™ 117 and Nafion™ 115) have been evaluated under a high salinity gradient conditions for the possible application in RED. In order to simulate the natural environments of RED operation, NaCl solution as well as multicomponent NaCl + MgCl2 have been tested.

Gross power density under high salinity gradient and the effect of Mg2+ on the efficiency in energy conversion have been evaluated in single cell RED using Nafion™ 117, Nafion™ 115, CMX and Fuji-CEM-80050 as cation exchange membranes. Two commercial cation exchange membranes – CMX and Fuji-CEM 80050, frequently used for RED applications, have served as benchmark.

The results show that under the condition of 0.5 M / 4.0 M NaCl solutions, the highest Pd,max was achieved using Nafion™ membrane. This result is attributed to their outstanding permselectivity compared to other CEMs. In the presence of Mg2+ ions, Pd,max reduction of 17 and 20% for Nafion™ 115 and Nafion™ 117 were recorded, respectively. Both membranes maintained their low resistance; however a loss in permselectivity was measured under this condition. Even though, it was reported that Nafion™ membranes outperformed other commercial membranes such as CMX and Fuji-CEM-80050 for RED application.

(Photo: Wikipedia)

Posted on

Promising hydrophilic membranes with fast and selective ion transport for energy devices

In addition to well-established Nafion™ membranes which are currently the best trade-off between high-performance and cost in proton exchange fuel cells (PEM), methanol fuel cells, electrolysis cells etc. As our energy resources are diversifying, there is a growing demand for efficient and selective ion-transport membranes for energy storage devices such as flow batteries.

A Sumitomo Electric flow battery for energy storage of a solar PV plant. (Photo: Sumitomo Electric Co.)

Redox flow batteries – the energy storage breakthrough

The high demand for a reliable and cost-effective energy storage systems is reflected in the increased diversity of technologies for energy storage. Among different electrochemical storage systems, one of the most promising candidates are redox-flow batteries (RFBs). They could meet large-scale energy storage requirements scoring in high efficiency, low scale-up cost, long charge/discharge cycle life, and independent energy storage and power generation capacity.

Since this technology is still young, the development of commercially and economically viable systems demands:

  • improvement of the core components e.g. membranes with special properties,
  • improvement of energy efficiency
  • reduction in overall cost system.

Meeting demands for redox flow batteries

Two research teams in the United Kingdom, one from Imperial College and the other from the University of Cambridge, pursued a new approach to design the next generation of microporous membrane materials for the redox-flow batteries. They recently published their data in the well renown journal Nature Materials. Well-defined narrow microporous channels together with hydrophilic functionality of the membranes enable fast transport of salt ions and high selectivity towards small organic molecules. The new membrane architecture is particularly valuable for aqueous organic flow batteries enabling high energy efficiency and high capacity retention. Importantly, the membranes have been prepared using roll-to-roll technology and mesoporous polyacrylonitrile low-cost support. Hence, these innovative membranes could be cost effective.

As the authors reported, the challenge for the new generation RFBs is development of low-cost hydrocarbon-based polymer membranes that features precise selectivity between ions and organic redox-active molecules. In addition, ion transport in these membranes depends on a formation of the interconnected water channels via microphase separation, which is considered a complex and difficult-to-control process on molecular level.

The new synthesis concept of ion-selective membranes is based on hydrophilic polymers of intrinsic microporosity (PIMs) that enable fast ion transport and high molecular selectivity. The structural diversity of PIMs can be controlled by monomer choice, polymerization reaction and post-synthetic modification, which further optimize these membranes for RFBs.

Two types of hydrophilic PIM have been developed and tested: PIMs derived from Tröger’s base and dibenzodioxin-based PIMs with hydrophilic and ionizable amidoxime groups.

The authors consider their approach innovative because of

  1. The application of PIMs to obtain rigid and contorted polymer chains resulting in sub-nanometre-sized cavities in microporous membranes;
  2. The introduction of hydrophilic functional groups forming interconnected water channels to optimize hydrophilicity and ion conductivity;
  3. The processing of the solution to produce a membrane of submicrometre thickness. This further reduces ion transport resistance and membrane production costs.

Ionic conductivity has been evaluated by the real-time experimental observations of water and ion uptake. The results suggest that water adsorption in the confined three-dimensional interconnected micropores leads to the formation of water-facilitated ionic channels, enabling fast transport of water and ions.

The selective ionic and molecular transport in PIM membranes was analyzed using concentration-driven dialysis diffusion tests. It was confirmed that new design of membranes effectively block large redox active molecules while enabling fast ion transport, which is crucial for the operation of organic RFBs.

In addition, long-term chemical stability, good electrochemical, thermal stability and good mechanical strength of the hydrophilic PIM membranes have been demonstrated.

Finally, it has been reported that the performance and stability tests of RFBs based on the new membranes, as well as of ion permeation rate and selectivity, are comparable to the performances based on a Nafion™ membranes as benchmark.

(Mima Varničić, 2020, photo: Wikipedia)

Posted on

Energy storage in Denmark

Denmark’s Electricity Portfolio

In our last post of our blog series about energy storage in Europe we focused on Italy. Now we move back north, to Denmark. Unsurprisingly, Denmark is known as a pioneer of wind energy. Relying almost exclusively on imported oil for its energy needs in the 1970s, renewable energy has grown to make up over half of electricity generated in the country. Denmark is targeting 100 percent renewable electricity by 2035, and 100 percent renewable energy in all sectors by 2050.

Electricity Production in Denmark (2016)

Proximity to both Scandinavia and mainland Europe makes exporting and importing power rather easy for the Danish system operator, Energinet.dk. This provides Denmark with the flexibility needed to achieve significant penetration of intermittent energy sources like wind while maintaining grid stability.

While the results to-date have been promising, getting to 100 percent renewable energy will still require a significant leap and the official policies that Denmark will use to guide this transition have yet to be delivered. However, there has been some indication at what the ultimate policies may look like. In their report Energy Scenarios for 2020, 2035 and 2050, the Danish Energy Agency outlined four different scenarios for becoming fossil-free by 2050 while meeting the 100 percent renewable electricity target of 2035. The scenarios, which are primarily built around deployment of wind energy or biomass, are:

  • Wind Scenario – wind as the primary energy source, along with solar PV, and combined heat and power. Massive electrification of the heat and transportation sectors.
  • Biomass Scenario – less wind deployment that in the wind scenario, with combined heat and power providing electricity and district heating. Transportation based on biofuels.
  • Bio+ Scenario – existing coal and gas generation replaced with bioenergy, 50% of electricity from wind. Heat from biomass and electricity (heat pumps).
  • Hydrogen Scenario – electricity from wind used to produce hydrogen through electrolysis. Hydrogen used as renewable energy storage medium, as well as  transportation fuel. Hydrogen scenario would require massive electrification of heat and transport sectors, while requiring wind deployment at faster rate than the wind scenario.

Agora Energiewende and DTU Management Engineering, have postulated that this scenario report does in fact show that transitioning the Danish energy sector to 100 percent renewables by 2050 is technically feasible under multiple pathways. However, Danish policy makers must decide before 2020 whether the energy system will evolve into a fuel-based biomass system, or electricity-based wind energy system (they must decided which of the four scenarios to pursue).

Energy Storage Facilities – Denmark

Regardless of which energy policy scenario Denmark decides to pursue, energy storage will be a central aspect of a successful energy transition. There are currently three EES facilities operating in Denmark, all of which are electro-chemical (batteries). A fourth EES facility – the HyBalance project – is currently under construction and will convert electricity produced by wind turbines to hydrogen through PEM electrolysis (proton exchange membrane).

Project Name

Technology Type

Capacity (kW)

Discharge (hrs)

Status

Service Use

RISO Syslab Redox Flow Battery Electro-chemical Flow Battery 15 8 Operational Renewables Capacity Firming
Vestas Lem Kær ESS Demo 1.2 MW Electro-chemical Lithium-ion Battery 1,200 0.25 Operational Frequency Regulation
Vestas Lem Kær ESS Demo 400 kW Electro-chemical Lithium-ion Battery 400 0.25 Operational Frequency Regulation
HyBalance Hydrogen Storage Hydrogen Power-to-Gas 1,250 Operational Renewables integration
BioCat Power-to-Gas Methane Storage Methane Power-to-Gas 1,000 Decommissioned Gas Grid Injection & Frequency Regulation

The HyBalance project is the pilot plant undertaking of Power2Hydrogen, a working group comprised of major industry players and academic research institutions aimed at demonstrating the large-scale potential for hydrogen from wind energy. The plant will produce up to 500 kg/day of hydrogen, used for transportation and grid balancing.

Worth noting is the decommissioned BioCat Power-to-Gas project, a pilot plant project which operated from 2014 to 2016 in Hvidovre, Denmark. The project, a joint collaboration between Electrochaea and several industry partners (funded by Energienet.dk), was a 1 MWe Power-to-Gas (methane) facility built to demonstrate the commercial capabilities of methane power-to-gas. The BioCat project was part of Electrochaea’s goal of reaching commercialization in late 2016, however, as of early 2017 no further updates have been given.

Energy Storage Market Outlook − Denmark

The energy storage market in Denmark will be most primed for growth should policy follow the Hydrogen Scenario, where massive amounts of hydrogen production will be needed to eliminate the use of fossil fuels across all sectors.

Renewable energy produced gases (hydrogen, methane) have the potential to balance the electricity grid in two primary ways: balancing supply and demand (“smart grid”), and balancing through physical storage. The smart grid, an intelligent electricity grid where production and consumption are administered centrally, presents significant opportunity for electrolysis technologies as short-term “buffer” storage (seconds to minutes). Bulk physical storage of renewable energy produced gases can act as a longer-term storage solution (hours, days, weeks, months) to help maintain flexibility in a fossil-free energy grid (The Danish Partnership for Hydrogen and Fuel Cells).

Without the hydrogen scenario, the potential for hydrogen-based energy storage in Denmark will be limited. In their 2016 report “potential of hydrogen in energy systems”, the Power2Hydrogen working group concluded that:

  • hydrogen electrolysers would not provide any significant upgrade on flexibility for renewables integration over today’s sufficiently flexible system, and;
  • by 2035, with the increased wind production, it was concluded that hydrogen electrolysers would in fact improve system flexibility, allowing for even more extensive penetration of wind energy in the system.

The potential for renewable energy produced gases in Demark is extremely high. There is a very distinct possibility that power-to-gas type of systems will be the linchpin of Denmark’s energy transition. While there appears to be little opportunity in the short-term, there will be extensive opportunity in the medium-to-long-term should the official energy transition policy focus on the hydrogen scenario, or a similar renewable gas based policy.

Read here our next post on the prospects for energy storage in Spain.

(Jon Martin, 2019)