Storing electricity? Some old solutions to this old problem are gaining momentum nowadays, thanks to recent improvements. Among these solutions, using electricity to obtain hydrogen and reconverting it later into energy or heat via fuel cells. The advantages are numerous: the possibility to store the excess production of electricity generated by renewable energy sources, to mix the hydrogen with natural gas (methane), to power electric vehicles… But there are as many challenges ahead if we want hydrogen to be a significant part of the future energy mix. Actions are under way. Let us discover them!
ParisTech Review – In today’s context of changing energy systems, the hydrogen and fuel cell industry is often cited. What exactly do these terms cover?
Hélène Pierre – Hydrogen is an element that has been used for decades by industry. Producing hydrogen, for instance, is quite simple: you just need water and electricity. In electrolysis of water with an electric current, the hydrogen and the oxygen molecules are separated.
The fuel cell technology enables us to operate the recombination process. Its principle was discovered in the 19th Century, but recent improvements have made it more relevant to today’s challenges. A fuel cell is a device that converts the chemical potential energy (the energy stored in molecular bonds) of the hydrogen gas (H2) into electrical energy. The fuel? Hydrogen gas and oxygen gas (02). The products of the reaction in the cell are water, electricity, and heat. In other words, the hydrogen and fuel cell industry proposes a solution to the problem of transforming and storing excess production of electricity from intermittent renewable energy sources, such as solar panels or wind turbines. That is why hydrogen is raising a lot of interest in the ongoing debate on energy transition.
The advantages of this technology are numerous. First of all, we can transform the unused renewable energies into hydrogen and store it for later use. In other words, it is equivalent to storing electricity over long periods of time – electricity which would otherwise have been lost. Secondly, no need to transform the hydrogen into electricity: it can used as a fuel or a source of heating, alone or combined with other gases such, for example, as methane natural gas. Thirdly, hydrogen encourages a territorial approach to energy production With renewable energies production is increasingly decentralized. It is consequently important to use them on a territorial scale and reduce the distance between production and consumption sites.
Given that hydrogen has already been used in industry for a long time now, how do you explain the upsurge in its attractiveness?
Techniques to obtain hydrogen by electrolysis have existed for a long time, notably alkaline technologies. But these technologies have evolved quite considerably, as is the case for hydrogen production with the introduction on the markets of Proton Exchange Membrane electrolysis. Extensive research and development in this area have accelerated the technologies, contributing to a sizeable drop in equipment costs. The objective is to obtain highly flexible electrolysis units, capable of instantly valorizing excess production of renewable energies. For this purpose, it must be possible, on one hand, to simply start and stop the units and, on the other hand, to have perfectly efficient units when operated at either full or low loads. This flexibility factor is important for the renewable energy markets, inasmuch as it allows for storing the production which is not consumed and therefore effectively reduces losses. The progress observed in electrolytic technologies holds great promise for the future, given that they are becoming increasingly efficient, from both technical and economic points of view. This clearly explains the renewed attractiveness of the hydrogen and fuel cell sector!
Fuel cell developed by CEA in 2006 for the automotive industry (©P. Stroppa/CEA)
What are the principal uses for hydrogen?
Apart from storing electricity, hydrogen can be valorized when mixed with methane natural gas. We are partners in the demonstrator GRHYD Project at Dunkirk (northern France), the objective of which is to explore the possibility of injecting hydrogen into the domestic gas distribution networks. This project will provide a new valorization for electricity produced via renewable energy sources. The aim is to assess the technical, economic and environmental relevance of this process called power to gas.
There are two aspects to the GHRYD project. On one hand, we study the feasibility of injecting hydrogen into the gas networks, with varying proportions (with up to 20% H2) to supply a new neighborhood with 200 lodgings, without needing to change either collective or private equipment. The aim is to make use of the excess renewable production of electricity, notably generated by wind turbines, through storing the energy as hydrogen and injecting this gas into the gas network, as and when needed. In doing so, we shall be able to study how the gas mix behaves in the distribution network, feeding a gas burning heat generator, and assessing the impact of possible variations. The objective is to be able to inject hydrogen in varying percentages, as a function of its availability, so as not to be required to produce hydrogen just to feed the network. We are therefore seeking to develop a flexible system at an acceptable cost.
On the other hand, the GHYD Project will allow us to test a compound fuel, with natural gas for vehicles (NGV) plus a proportion of hydrogen, from 6% to 20% max. In the long term, some fifty buses will be operated with this mixed gas fuel in Dunkirk and its surroundings. We aim here to study the behavior of the vehicles while valorizing the renewable energy sources. The advantage here is that the hydrogen will contribute to “greening” the fuel consumed. And if the hydrogen is produced from already “green” energy sources, this adds a renewable fraction, inasmuch as it will decrease overall CO2 emissions. Moreover, adding hydrogen improves the mixed fuel efficiency – as was observed during a previous project in Dunkirk, 2004-2009. There is no need to modify the NGV engines. In other words, the solution proposed is attractive, not only from an ecological but also an economic point of view.
Are we to understand that it is possible to see vehicles running on either a methane gas-hydrogen mix or on pure hydrogen?
Indeed; many countries are now engaged in development along these lines. Fuel cells come in various power ratings, from small domestic appliances installed in homes to large industrial installations, ranging from 1 kW to 1 MW. They can easily be fitted in vehicles along with a compressed hydrogen tank. By transforming the hydrogen into electricity, the cell feeds the vehicle’s electric propulsion system. It is estimated that a fuel cell of this type would offer a range of between 300 to 500 km, i.e., far more than with an all-electric (battery driven) vehicle. Moreover, no major modifications are needed for the electric motor proper. Also, we can note numerous ongoing R&D studies into fuel cell technologies and onboard storage systems with a view to reducing the space taken up by the fuel cell in the limited volume of the vehicles, optimizing the attainable range and lowering the cost factors. The first fuel cell vehicles introduced to the market place have proved successful sales. Toyota, for example, have started mass-producing and selling its Mirai model.
So-called “stationary” fuel cells are being developed, designed for installation in private premises, supplying the homes with both heat and electricity in a technique called co-generation. Cells in this category can also be used to feed electric vehicles. In Japan, some 100,000 stationary fuel cell installations have been assembled and run directly in the natural gas network. This alone proves that the technology is developing well and can be installed rapidly.
Does this suggest that recharge and stationary fuel cells infrastructures need to be installed in service stations?
Again the answer is yes; today we stand at a special cross-roads in time. We shall need to build a charging infrastructure, with specific hydrogen service stations. A study carried out in Germany, in England and France has led to a roadmap of how the infrastructures would be deployed over the coming twenty years. In France, we have a consortium of actors working on this thematic (H2 Mobility France) who have taken the option to proceed by clusters. The policy would call for first installing local ad hoc service stations for captive hydrogen vehicle fleets (company-owned or by local authorities). This category of vehicle usually only travels for short distances and returns to the depot in the evening. It is therefore perfectly adapted to the infrastructure. The next steps would be to extend the network of stations, progressively covering the country completely.
You also mentioned co-generation…
Fuel cells supply electricity and heat with high efficiency levels, especially for the electricity. Stationary fuel cells – installed in residential areas and fed by natural gas from the existing gas distribution network – are already supplying households with heat and electric power. In urban areas, these natural gas (CH4) distribution networks (or with a CH4-H2 mix) will prove to be truly efficient energy supply tools. That is what the GHRYD Project is designed to demonstrate.
What are the challenges the industry must now face?
Regulatory aspects are essential, inasmuch as they serve to guarantee safe use of equipment, whatever the uses. For the time being, hydrogen is used almost exclusively by industrial sectors. Regulations were framed but were not adapted to fuel cells used to recharge a mobile phone or to run a vehicle. A general public use calls for adapted regulations both for stationary and mobile uses. However, the rules must be drafted in concertation with the actors in the field so as to assure a proper balance and not block development of the sector by excessive rigidity or complexity. That is why we are working, among others, with Ineris, the French National Competence Centre for Industrial Safety and Environmental Protection.
Another challenge is that related to costs, which today are far higher than those of existing systems. The objective assigned to the R&D studies also consists of optimizing equipment efficiency and decreasing their operational costs, or to put it differently, obtaining a better price/performance ratio. Industrializing electrolysis unit, thereby producing large quantities of hydrogen, will lower equipment costs and the final cost will go down more and more rapidly. In the last resort, the cost of producing hydrogen relates to the cost of generating electricity. We can safely forecast that, in the long term, a massive production of renewable source electricity will lower costs considerably.
Societal acceptance by the public at large will be a real challenge! There are many preconceived ideas about the level of risk associated with hydrogen. Improving user perception of realities here will be a major aspect of a breakthrough of hydrogen in the markets.
As you see it, the hydrogen and fuel cell industry has moved out of basic research. Is that so?
Yes, indeed! We are no longer in basic ‘blue-skies’ research, even if the R&D efforts continue and these are important. We observe the territorial deployment of the first commercial developments as, for example, in Japan, but also in some parts of Europe. Hydrogen is now mature in certain markets, while others are still effectively in their applied research phases and initial prototype set-ups. One highly advanced area of application can be seen at relay antennae for mobile telecom operator utilities. Some of these antennae are totally isolated. Now we are equipping them with back-up electric supplies that rely on fuel cell units, the latter now being cost effective compared with classic, liquid/gas fuelled electric generators. However, we still have to create a valid economic model, simply because the price for a fuel cell will never be as low as that for a gas burning unit! Studies still have to be carried out here to improve the competiveness of these fuel cell units. This will no doubt call for involvement and action by Government authorities in order to reach acceptable cost levels. The convergence between hydrogen and methane natural gas will help hydrogen to be affordable. Increased volumes of H2 gas produced and incentive territorial decisions to decentralize energy production will also enhance the prospects for the sector.
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