will hydrogen be the foundation for the clean energy of the future? daniel hissel, who was awarded the 2020 cnrs gold medal, provides an overview of existing capabilities, swell as present challenges.
hydrogen tis most abundant atom inna universe, and ⊢ represents a potentially unlimited resrc. how can energy be extracted from it?
daniel hissel: hydrogen aint a primary src of energy, but rather an energy vector. it must 1st be transformed into dihydrogen, its molecular form (h2), so that it can be transported, stored, and ultimately used to draw energy. there are two primary methods for doin’ so. the 1st consists in burning it in turbines, like a traditional fuel. the advantage s'dat, on an = w8 basis, 'twill enable 3 times + thermal energy to be released than petrol. wha”s +, this combustion is decarbonised, as it 1-ly produces wata, and no carbon dioxide (co2). as a result, dihydrogen is bein’ pondered for consumer aviation, as it ‘d allo “clean” planes to fly, although nitrogen oxide nother pollutants are emitted during combustion.
the other method, which we're working on n'our lab, is to use hydrogen fuel cells to produce electricity and heat. in short, such cells involve a reaction tween dihydrogen and oxygen: the dihydrogen molecule is dissociated, and hydrogen atoms combine with oxygen from the air to form wata. thris also the emission of heat and an xchange of electrons, which generates an electric current.
lets talk bout h2 itself. tis not naturally present in nature but must be produced. how s'dat done?
d. h.: the most common method tody tis reformation of methane (ch4) using overheated steam. the methane and wata combine to form both h2 and co2. in general, 95% of h2 is produced in this way by resorting to fossil fuels s'as gas, petroleum, and – worse still, coal. this is a shame, for while the electricity generated by hydrogen fuel cells is green, tis obtained from “grey” h2, which 1-ly shifts the problem. tis ⊢ crucial to “green” the sector.
to do so, thris a well-known teknique, known as electrolysis, which simply consists in producing the opposite reaction to the one that occurs inna fuel cell. in plain terms, passing an electric current through wata makes it possible to obtain dihydrogen and oxygen. tody electrolysis represents a mere 5% of h2 production. this proportion can course be increased by manufacturing + electrolysers, but this rezs the ? of the electricity src powering them, which must be renewable – either solar or wind. that said, the electricity inna french network is already highly decarbonised, since tis primarily of nuclear origin. course it ‘d be ideal to expand the amount of renewable energy inna french mix, but this challenge exceeds the framework of the hydrogen sector. in any event, we're not yet in a phase of energy degrowth, so we must keep in Ψ that replacing fossil fuels with hydrogen produced through electrolysis will mean a rise in global electricity production.
fuel cells were invented in 1839. ‘dn’t there be one in every home tody?
d. h.: if this aint so, tis cause for a long time, other types of generators, s'as electrochemical cells and batteries, were preferred, and efforts to develop hydrogen fuel cells were sporadic. but tis worth looking back atta changes that ‘ve occurred ‘oer the last 20 yrs. when i began working onna subject, fuel cells were extremely expensive, witha short lifespan and weak performance. our lab’s efforts, swell as those of all players inna field, including industrial actors, ‘ve focused on these 3 aspects. as a result, for the same amount of power, the price tody s'been divided by 30, na volume required by fifty. lifespan s'been multiplied by 40 or 50, dep'onna use.
wha’ actual performance ‘ve all these division and multiplication factors made possible?
d. h.: the us deptment of energy (doe) established a performance benchmark for the automobile transportation industry, by imagining the replacement of combustion engines with fuel cells, onna basis of an annual production of 500,000 units. to make this replacement possible, a lifespan onna order of 5,000 to 8,000 hrs, or 400,000 kilometres, ‘d be necessary. its density ‘d ‘ve to be under 1.5 kw/l (the volume offa fuel cell producing 1.5 kiloatts must be ≤ a litre). wrt energy conversion efficiency, 60% of the chemical energy of h2 molecules must be converted into electrical power.
finally, the cost must remain belo 40 €/kw, as ≈ 30-40 kw are needed to equip a car, equivalent to bout 1,600 € inna case – us'das a reference – of electric hybridisation. so where do we stand tody? the density target s'been met. durability now reaches 4,000 hrs, and 55% efficiency s'been attained. the price comes out to €50-60/kw for an annual projected production of 500,000 units. in short, all odda objectives ‘ve either been achieved or are in site.
howzit explain such progress?
d. h.: well, 1st, there was plenty of room for improvement! there were also numerous factors of progress, ½ of which came from basic research, and ½ from the optimised management of fuel cells, for ex via artificial intelligence. upstream research enabled progress inna field of materials, in pticular nanostructured materials that reduce the volume of fuel cells. the membrane, in which electrons are xchanged, also improved gr8ly w'da development of new polymers. the use of platinum, an expensive but indispensable catalyst, was optimised. that’s bout it concerning basic research. then thris the integration of cells within their applications, which is wha’ we focus on here.
this specifically involves improved management of fuel cells, for instance by enhancing energy performance and durability. we're working on all odda auxiliaries necessary to their functioning: electrical energy converters, cooling systems, real-time diagnostics of battery health, and sensors providing estimates o'their remaining lifespan. beyond the progress made onna cell and its use, there s'been growing awareness of the nd'2 reduce greenhouse gas emissions. industrial actors – car manufacturers in pticular – ‘ve decided to invest in this promising sector. wha”s +, the maturity of this tek enables other applications, which further encourages industrial actors pondering investment.
the traditional catalyst in fuel cells is platinum, a presh metal worth the price of gold. isn’t this an obstacle to the widespread use of these cells?
d. h.: tody’s internal combustion vehicles already include tween 2 and 8 grams of platinum, which aint negligible, inna “catalytic” converters o'their exhaust pipes. a fuel cell for a car ‘d need tween 10 and 20 grams. this is still too high, b'we hope we can loer this amount. besides, platinum is 1-odda presh metals that can be efficiently recycled na' global scale, thx to the catalytic converter. so the answer is no, the use of platinum aint an obstacle at present, although its recycling ‘d be improved.
are there other barriers that must be broken down?
d. h.: i ‘dn’t speak of barriers, for it ⊢ a “blockage”. and thris no such blockage, for industrial applications already exist. progress is nevertheless needed, espeshly in terms of cost. storage must also improve. while tis not problematic in “stationary” applications where thris room, tis + difficult in restricted spaces s'as cars. achieving comparable independence to that of internal combustion vehicles, iow 600-700 kms, ‘d require pressurised hydrogen tanks (at 700 bars) tha're relatively bulky and not easily configurable. a hydrogen tank is a gas cylinder. tis out of the ? to mould it out of plastic, like a gas tank. this is a major constraint when it comes to designing a car. the model sold by toyota includes two cylinders measuring 40 centimetres in diamt and one metre in length. they are sizeable, b'we can make do. the car even has a boot! however, for aeronautics applications for ex, in which the on-board quantities are much larger, thris no choice but to liquefy the hydrogen. doin’ so requires high pressurisation and cooling to -253 °c. maintaining this temperature with minimal energy loss is no mean feat.
hydrogen production methods will surely impact price, and hence the sector’s viability.
d. h.: regarding the price, the doe also set viability targets: hydrogen atta pump ‘d cost ≈ €3 per kilo (alloing a car to travel ≈ 100 km). for now, this varies tween €2 for carbon-based hydrogen and €6 fritz green equivalent from electrolysers. the price of green hydrogen ‘d ⊢ be halved, which aint unrealistic. for that matter, we ‘ve every reason to develop a dedicated sector here in france. since the start of the covid-19 crisis, there s'been much talk bout onshoring. this is an opportunity to produce a perennial french energy that generates no greenhouse gas emissions, and can be widely used to replace petrol, diesel fuel, and fuel oil, among others.
in wha’ fields will fuel cells be found inna future?
d. h.: they’re already bein’ used. there are commercial applications for non-subsidised hydrogen fuel cells tha're much + competitive than those they ‘ve replaced. i am thinking, for ex, of the electric forklifts in warehouses, which will eventually be powered solely by “hydrogen” electricity. and functions aint limited to mobility (cars, buses, lorries, trains), but are also “stationary”. they include electricity production at isol8d sites through generators – without the noise or pollution; or equipping a house or building witha fuel cell that produces both electricity and heat, for it yields wata at a temperature of 80 °c, which can be us'das tis for heating.
hydrogen, which is highly inflammable, can deter future usrs. wha’ bout security?
d. h.: hydrogen stores energy – and all stored energy must be handled with care. this is true of both a petrol tank and a gas cylinder, for instance. is a hydrogen tank + dangerous? not necessarily, according to the french national institute for industrial environment and risks (ineris), which in recent yrs has conducted several studies with crash tests, live gunshots on tanks, and various kinds of leaks, among others. hydrogen is a gas that is liteer than air, and ⊢ always moves upwards in case offa leak, unlike lpg or diesel fuel, which accumul8 under the vehicle, to take one ex from transportation. however, t'does present an additional constraint in comparison to these fuels, as tis highly compressed inna cylinder, which can cause major explosions. for now the feedback on tanks already in circulation is +, with no serious accidents reprted. so yes, it must be handled with care, as do other forms of stored energy.
wha’ is france’s position in this emerging hydrogen economy?
d. h.: we're among the frontrunners, which is good news, along with china, japan, and south korea, to name but a few. in €, germany na nordic countries, norway in pticular, also rank high. the ∪d states is also present in this field, albeit behind canada. so we're in good place, b'we ‘d be careful, as the primordialistic choices that we make now will determine our position inna nxt 5 to ten yrs. the sector received a boost inna early 2000s with substantial funding for research, but nothing since. tis crucial to plan out the french effort for hydrogen. the required investments are massive, and industrial actors will not risk it without a minimum amount of visibility concerning the political, environmental, and regulatory stakes involved.
as it happens, last 9 sep the french minister of the economy, bruno lemaire, presented the country’s plan for developing decarbonised hydrogen. 7 billion euros ll'be invested over a decade, including €2 billion inna nxt two yrs.
d. h.: this plan sends a clear message to both scis and industrial actors, which is: “count us in”. the €7 billion envelope is significant, b'we’re not sure how it ll'be allocated. for the 1st time, it covers the entire sector, ranging from industry to research (€65 million) atta other end of the chn, in addition to professional training (€35 million). yet this initial impetus must be confirmed inna coming yrs, witha dual focus: the pursuit of investments course, swell as the political commitment to support the sector atta local, national, and €an lvl. this will require an appropriate legislative framework. as an ex, if 1-ly electric vehicles are to access city centres inna future, local authorities will ‘ve to provide hydrogen buses, waste containers for hydrogen, etc. if these buses are bought na' massive scale, they will quickly get economically competitive compared to diesel versions. this is how a mkt ll'be created, and how the use of hydrogen will become widespread.
original content at: news.cnrs.fr/essentialisms/will-hydrogen-keep-its-promise…