Author: Abhinav Dubey, Ansruta Chatterjee, Radhe Krishna, Shahil Choudhary
Introduction — Hydrogen Energy
“Replacing traditional sources of energy with renewable energy is going to be a challenging task. However, by adding renewable energy to the grid and gradually increasing its contribution, we can realistically expect a future that is powered completely by green energy.” -Tulsi Tanti, Founder & Chairman, Suzlon Energy.
Energy resources are one of the most discussed agendas throughout. The aim is to improve access to energy, achieve advanced economic development, improve energy security and mitigate climate change. This has given rise to a global transition to renewable energy technologies to achieve sustainable growth. Traditional energy resources have contributed to one-third of global greenhouse gas emissions. It is essential to raise the standard of living by providing cleaner and more reliable electricity. Hydrogen as a fuel has turned out to be the most suitable both in terms of feasibility and accessibility. There has been a lot of research to optimise the utilisation techniques and storage techniques and bring them to the norm.
Now then, what exactly are Hydrogen Energy Storages (HES)?
In its simplest essence, it is the conversion of Electrical energy to Hydrogen (Power to gas or P2G) by electrolysis and then when needed back to electricity form (Gas to Power or G2P). The renewable energy is stored in hydrogen by the splitting of water into hydrogen and oxygen by use of electricity on a molecular level by using the process called electrolysis. Other production methods include creating hydrogen from the usage of fossil fuels. After the production, hydrogen functions as an energy carrier that can be used to supply energy wherever needed. It is most popularly stored as a compressed gas, but can also be liquified and stored as a cryogenic liquid. Recent research has led to the development of storage in liquid organic hydrogen carriers and ammonia, that act as molecular Hydrogen storage for long-distance transportation- a far more cost-effective method than shipping compressed gas, especially for longer distances spanning out over a 160km.
The major difference between batteries and HES lies in the fact that batteries are only capable of power-to-power usage whereas HES is capable of providing various usage vectors. HES also allows integration with the gas grid through pipeline injections, a direct link that batteries are unable to provide.
Currently, the most popular method of converting stored Hydrogen to Electrical Energy form is via Proton Exchange Membrane or Polymer Electrolyte Membrane (PEM) fuel cell as it is the most energy-efficient zero-emission method. PEM consists of a membrane between two cell plates containing gas channels. Hydrogen exists on one side of the membrane which reacts with the catalyst in the membrane, thereby effectively splitting it into protons and electrons. The protons then pass through the membrane and the flow of the residual electrons generates electricity. As fuel cells are very scale-able they can be used in all applications that need energy, ranging from mobile cell phones, cars, buses, and even in large heat and power plants. Fuel cells as a technology will be the next energy innovation step that will bring progress and prosperity to our societies, with as great an impact as the steam engine and the combustion engine have had.
Relying only on renewable energy also solves the threats of oil depletion and pollution in the present energy system. This also makes it possible for everybody to produce their own energy creating more political stability and benefits for all of us. But much has to be done before hydrogen is for real. The next sections deal with this.
Clean hydrogen is touted as the future fuel of the EU, promising to deliver an abundance of carbon-neutral energy by 2030. It will power long-haul freight vehicles, aeroplanes, steel production, and domestic heating, proponents say. But environmentalists are skeptical about these green virtues.
“We can’t tackle the climate crisis by consuming the same amount of energy and just burning different fuels. Energy savings, changing energy use, and electrification of as much heating, transport, and industry as possible, should be at the core of our energy plans,” said Silvia Pastorelli, climate and energy campaigner at Greenpeace.
How does HES work?
The electrolysers needed to split water into oxygen and hydrogen are few in number, and renewable electricity needed to power them is not yet abundant enough. The European Commission estimates between €180 billion and €470 billion will be needed before green hydrogen can make up 13–14% of the EU energy mix in 2050.
But things are moving fast with new hydrogen demonstration projects launching every day. Countries are drawing up strategies to build green hydrogen markets. Start-ups and researchers are working across the entire hydrogen value chain. A thermally compensated electrolyser model has been developed in Simulink and has proven, through a case study, to be able to accurately simulate hydrogen generation and storage systems. The developed model presents a key finding for the hydrogen industry as it does not only allow the investigation of hydrogen systems performance in a preinstallation scenario prior to embarking on the expensive capital investment but has also proven to be useful in transport scenarios. The developed model was found to be able to simulate operational installed hydrogen systems and assist in identifying their performance issues accurately.
An algorithm for modeling the impact of thermal transients, especially in alkaline electrolysers, on the overall hydrogen production has been developed. The prolonged thermal transients, associated with electrolysers fed by renewable energy sources, result in extended periods of time where the electrolyser does not produce hydrogen at its highest efficiency and thus resulting in an overall reduction in its hydrogen production. The typical effect of thermal transients on the electrolyser hydrogen production can be found by using the proposed algorithm, and a reduction in the cumulative hydrogen production was found to be in the range between 1 and 3%.
A new deterministic sizing methodology that offers a rapid initial sizing of renewable hydrogen energy storage systems has been given. The proposed method requires a very limited number of input data to offer an initial system size for a hybrid renewable hydrogen energy storage system (HRHES) very quickly, and thus it is useful at the very early initial design phase to assist in the early decision-making for system implementation. To develop this sizing model, a model has been developed for every single item in the proposed HRHES (the implemented renewable energy sources, the electrolyser, H2 storage, and fuel cell). These models were then integrated together.
A novel levelized cost model has been developed for investigating the financial competitiveness of hydrogen energy storage technology. It has been identified that hydrogen use as an energy storage mechanism achieves the most financial competitiveness when the by-product oxygen is utilised.
The use of hydrogen for energy storage is an effective solution to solve the intermittent energy issues associated with solar and wind energy. The main challenge associated with hydrogen implementation is related to its production and storage. Many hydrogen storage options have been proposed with the feasibility of different strategies depending on the demands of their target sectors. An ideal energy storage system would consist of an electrolyser that is powered by excess wind or solar electricity coupled with a hydrogen storage system. A fuel cell power generation system will utilise hydrogen to harvest and supply power when required.
Challenges to HES
We have many challenges when coming to the point of hydrogen and its applications if we consider India. The greatest challenge for hydrogen production, particularly from renewable resources, is providing hydrogen at a lower cost. For transportation fuel cells, hydrogen must be cost-competitive with conventional fuels and technologies on a per-mile basis. This means that the cost of hydrogen — regardless of the production technology — must be less than $4/ gallon of gasoline equivalent. To reduce overall hydrogen cost, research is focused on improving the efficiency and lifetime of hydrogen production technologies as well as reducing the cost of capital equipment, operations, and maintenance.
Conclusion
As energy sources like Solar, Wind, or even Hydro are gaining popularity, there is a greater need for seasonal storage as these sources can have large disparities in output from one season to another. While Hydrogen storage will be more expensive compared to other alternative sources, it is still a widely popular choice due to its ability to handle the fluctuations of energy input from such unsteady energy sources. It will bring forth an Era where there are no longer disparities in power supplied based on weather or location by effectively separating power from energy.
References:
https://energystorage.org/why-energy-storage/technologies/hydrogen-energy-storage/
https://energystorage.org/why-energy-storage/technologies/hydrogen-energy-storage/