20 ms·
Solar-driven water splitting at 13.8% solar-to-hydrogen efficiency
- tomas789 5y agoI did not investigate it properly but at first glance the efficiency is obtained via low current density of the electrolyser. That means high efficiency but low volume. That translates to more hardware needed to produce a unit of power. State of the art electrolyzers are run at 1000x current densities. That roughly means 1000x installation cost.
- tuetnsuppe 5y agoBefore people get too excited they might want consider the life time of the cell as indicated over a 10 hour test window.
- wiz21c 5y ago> high peak solar-to-fuel conversion does it mean there's a "mean solar-to-fuel conversion" to look for ?
- nanomonkey 5y agoTwo things are hardly ever spoken about when splitting water: The pure oxygen is just as useful of a product and can be used to gasify woody biomass, plastics and other waste streams into more useful fuel sources such as syngas, or liquid fuels using the fischer-tropsch process. It is also useful for medical processes. Second, natural gas lines can utilize something like 10% hydrogen...so we can store a large quantity in our existing infrastructure for use later that day, or in other locations.
- fulafel 5y agoNatural gas pipelines will have to ramp down with fossils though.
- api 5y agoSolves the energy storage problem. Just add tanks.
- NoblePublius 5y ago$2 trillion of tanks and $1 trillion of pipelines, just for North America. Meanwhile, electrical grids already exist.
- viburnum 5y agoThat’s cheap. USA spends $8 trillion on defense every ten years.
- ncmncm 5y agoAnd gets nothing for it.
- new_realist 5y agoElectrical grids don't store energy. If you wanted to store just 10% of the U.S. electrical generation from summer to winter using lithium-ion batteries, it would cost roughly $42 trillion dollars. Yes, trillion. Storing 10% of the U.S. daily needs for less time (say, one day) is a better story for batteries: only $115 billion. That's how un-scalable long-term battery storage is. Hydrogen is more so: you can store hydrogen in vast quantities in salt caverns, and move it around. Pumped hydro is best, but sites are limited. Compressed air is another solid contender.
- Weryj 5y agoHow's the gravity storage going, it looked really promising and simple.
- dragontamer 5y agoIf you count pumped hydro, gravity storage is the #1 storage of the USA. Turns out that pumping water up-hill and running generators when the water flows backwards is a very efficient energy storage mechanism.
- thinkcontext 5y ago
- r00fus 5y agoI assume there are also costs to store and deliver hydrogen fuel? I'd like to see an EROEI comparison of electric vs. hydrogen.
- meepmorp 5y agoMake ammonia out of it, easier to store and transport.
- toomuchtodo 5y agoThe closer you can get to both steel mills and pipelines, the better. Steel mills can use the hydrogen to replace metallurgical/coking coal, and the pipeline can accept ammonia for transport. Hydrogen is very hard on pipeline infra, unless mixed at low concentrations with a carrier gas.
- jsonne 5y agoIt also is how they power refrigeration in meat processing to keep the freezers cold. Seems like if you put it next to those manufacturing facilities to power the freezer trucks and facility itself you could save a significant amount of energy and reduce greenhouse gasses.
- jhloa2 5y agoProbably not as much as you'd think. Ammonia is used as a refrigerant in a closed-loop system. You'll eventually have some leaks and have to recharge the system, but the ammonia isn't a consumable item in this process.
- ncmncm 5y agoA steel mill will make its own hydrogen on demand from wired-in power off the continental grid. Likewise, international airports for LH2 aircraft. They will bank hydrogen synthesized when grid prices are lowest, in mid-day, when immediate power need is vastly outstripped by solar generating capacity.
- 5y ago
- NoblePublius 5y agothis will be used as an excuse to expand production of hydrogen made from carbon fuel on the basis that eventually the carbon will be made sustainably. Don’t fall for it.
- Animats 5y agoLithium iron phosphate batteries have about 95% round trip efficiency. Some manufacturers say 98%. AC-DC-AC conversion is around 98%-99% efficiency now. So batteries are way ahead on efficiency. Tesla is switching from lithium-ion to lithium iron phosphate for fixed battery installations.[1] The energy per unit weight is somewhat lower, but that doesn't matter much for fixed installations. The safety is better, too - lithium iron phosphate batteries don't have the thermal runaway problem. BYD, which is the biggest producer of batteries in the world, sells shipping container sized lithium iron phosphate sized battery packs for large scale solar backup. [1] https://www.utilitydive.com/news/tesla-shifts-battery-chemistry-for-utility-scale-storage-megawall/600315/ https://www.utilitydive.com/news/tesla-shifts-battery-chemis...
- beerandt 5y ago>So batteries are way ahead on efficiency. Conversion efficiency is a different thing than storage efficiency or transmission efficiency. Unless your gas tank is leaking, it's efficiency as a portable energy storage device approaches 100%, especially for modern vapor sealed vehicles.
- xorcist 5y agoSolar cells are inefficient, and we should just get power off batteries instead? That's not an argument for anything, and doesn't have anything to do with the article.
- dragontamer 5y agoElectricity-to-electricity efficiency should not be compared with solar-to-electricity efficiency. The typical solar panel is maybe 25% efficient or less. The typical steam engine is maybe 50% efficient. Once things are in the form of electricity, we have a large variety of options for efficient transport and storage. But sometimes electricity isn't useful. Li-Ion will never be light enough for a serious airplane for example, while hydrogen _IS_ light enough for an airplane. (But maybe too volumetric, as every practical H2 airplane engine relies upon high-pressure storage or even cryogenics to keep H2 at a small enough volume). EDIT: If we think of it as chemistry... perhaps we can make liquid fuels out of H2 like coal liquefaction turns one fuel source into another. After all, classical fuels are nothing more than carbon + hydrogen + energy... and H2 is a very efficient form of storing energy for that reaction. Or maybe we learn to just use H2 directly? There are fuel cells and engines running on H2 today, but I'm always worried about the volume of H2 (requiring either compression or cyrogenics before you reach practicality).
- fuddle 5y agoCan someone please ELI5?
- dragontamer 5y agoThe abstract looks simple enough? They played with some chemicals / catalysts, and have demonstrated a prototype where they made a "Solar Panel" that turns water (H2O) into 2H2 + O2... aka Hydrogen + Oxygen. The measured efficiency was 13.8%, less efficient than an electric solar panel (20% to 25% efficiency), but possibly the most efficient solar -> hydrogen design discussed so far. Consider a 25% efficient solar panel -> 50% electrical efficiency to convert H2O into H2 + O2 == 12.5% total efficiency (and a 25% efficient solar panel is a high-end panel). So this design discussed is probably better than the status quo. ------------- There are internet flame wars over the future of energy and energy storage. Lithium Ion batteries are one form. Hydrogen is being proposed as a fuel of the future (with Japan showing off Hydrogen torches all over the Olympics earlier this year, as a lot of Japanese companies are pushing Hydrogen as a future fuel)
- jhgb 5y agoSome people didn't like that you could combine bog-standard 20% efficient photovoltaic panels with bog-standard 75% efficient electrolyzers to reach 15% efficiency of conversion of sunlight to hydrogen, and came up with a specialized single-step device...that is only 14% efficient. ;)
- solarkraft 5y agoCongratulations on the advancement, but wow, that's still pretty bad. The only way this would become popular would be through being super cheap.
- tombert 5y agoI am speaking completely out of ignorance on this, so someone with a bit more familiarity with both physics and chemistry might be able to clarify. ------ From what I understand, one of the biggest issues with trying to replace commercial cross-country jets [1] with electric alternatives is due to the fact that there isn't enough energy density in a battery to make that possible, and as a result, airplanes are a huge polluter towards climate change. Would it make more sense to try and make hydrogen jets, at least if we can make the hydrogen relatively efficiently? [1] I know jets really only make sense with fuel, replace "jet" with "big airplane"
- Manuel_D 5y agoShort answer: yes, hydrogen jets are probably the future. Electrochemical batteries fundamentally lack the required mass to energy ratio necessary for air travel. But there's a lot of challenges to actually powering an aircraft via hydrogen, and it's probably not going to happen for a while. The long answer: * The question is moot until we have widespread decarbonization of the energy grid. Currently, our hydrogen mostly comes from steam reformation - splitting methane, CH4, into 2H2 + CO - which emits carbon dioxide. Once our electrical production is carbon-free, then we can think of producing hydrogen and powering vehicles with that. Electrolysis can serve as a carbon-free source of hydrogen, if the electricity is produced from a carbon-free source. There are more efficient forms of hydrogen production, like thermochemical hydrogen production with heat provided by nuclear reactors. * Once carbon-free hydrogen production becomes available, then there's the question of building hydrogen powered vehicles. Hydrogen is the most energy dense fuel by unit of mass, except for nuclear fuels, but it's about half the energy density by unit of volume compared to hydrocarbons. Substituting fossil fuels with hydrogen is probably more feasible in container ships than aircraft. Hydrogen containment, be it pressurized or liquid-cryogenic, scales better at higher capacities as there is a better volume to surface-area ratio. Aircraft wings (long and skinny) are basically the worst shape for hydrogen containment. Past examples of hydrogen powered aircraft stored it in the fuselage [1], which would sacrifice cargo and passenger space. * Lastly, for aircraft there's also the question of making engines that don't produce greenhouse gases. High-temperature hydrogen gas turbines will also produce nitrous oxides, which are greenhouse gases. This can be mitigated by running turbines at lower temperatures, but that reduces efficiency. There's also the idea of using hydrogen fuel cells to produce electricity to run turbines, but fuel cells and electrical motors don't have as good power to weight ratios as combustion turbines. I'm much more optimistic about converting maritime transport to hydrogen fuels than aircraft. That said, the military is very interested in hydrogen planes. One of the limiting factors in modern naval warfare is fuel to fly planes. With hydrogen powered planes, a carrier could produce hydrogen with its nuclear reactors giving carriers an effectively unlimited source of aviation fuel. If they figure it out, hopefully the tech propagates to civil air transport. 1. https://en.wikipedia.org/wiki/Tupolev_Tu-155 https://en.wikipedia.org/wiki/Tupolev_Tu-155
- zz865 5y agoOne big electricity storage problem is seasonal - eg cold sunless winters. Eg batteries are great for daytime charging your car - but they aren't great for storing up a whole summer's worth of energy to burn in the winter. Hydrogen could do that.
- bryanlarsen 5y agoA 3x overbuild of solar+wind in an optimal mix, along with a continental grid and 3 hours worth of batteries is all you need for 99.99% reliability over an entire year. https://www.nature.com/articles/s41467-021-26355-z https://www.nature.com/articles/s41467-021-26355-z
- ncmncm 5y agoYou probably want a 6x overbuild to account for round-trip losses in your storage system. Cost of storage falls very fast as your efficiency requirements are relaxed, which becomes attractive as raw generating cost plummets.
- kolinko 5y agoAccording to the paper you cited, such setup in Germany would cause 100-500 hours of blackouts each year.
- bryanlarsen 5y ago"continent wide grid" is a key requirement.
- VygmraMGVl 5y agoPg&e has performed similarly over the past 10 years, averaged across California.
- pensatoio 5y agoor... we could use space rocks to heat water. just saying.
- 5y ago
- bhewes 5y agoCool on the way to sustainable liquid fuels.
- eatbitseveryday 5y agoWe see the value in fuels like diesel being highly energy-dense. If we used the sun to create fuel like hydrogen or electricity, what is against simply creating (purified in some sense) man-made diesel and continue to use combustion engines? We would not be contributing to the overall contribution of greehouse gases. Some arguments are diesel and friends are safer in storage and transportation than hydrogen.
- maxerickson 5y agoProbably makes more sense to do compressed or liquid methane for ground vehicles. Easier to synthesize and cleaner burning.
- mr_toad 5y ago> what is against simply creating (purified in some sense) man-made diesel and continue to use combustion engines? Mostly it’s just economics. Either the costs need to come down, or oil prices need to rise. The way oil prices are headed, that might not take long.
- kumarvvr 5y agoThe more complex the chemistry, the less economically viable. Hydrogen is just H2. Diesel is a complex hydrocarbon. A viable future, would be a highly distributed network of hydrogen stations, with Hydrogen generated from solar energy, with enough reserve capacity to act as a base load plant. Extracting energy from hydrogen is a well understood process.
- mountainboy 5y agoso how would a person go about making one of these for use at home?
- lysp 5y agoThere are videos on youtube with various home-made h2 generators/splitters. The issue with doing something useful with it is compression and storage. While compression is easy, purification is an issue. With certain lower percentages of purity (from very rough memory under 92%, but could be in the 99s) it becomes an explosion risk.
- jp0d 5y agoThis is not too bad. I'd prefer hydrogen fuel cells over massive toxic batteries that we're going to have to dispose safely in a few years, from all those used Teslas! I don't know about other countries, but most of the electricity generated here in Australia is from Coal and Natural gas. That's an unfortunate fact. I don't see any reason to buy an electric car until that changes. In the meantime if the solar driven hydrogen production efficiency increases then we can have an even cleaner future.
- MaKey 5y agoWhat is toxic about lithium-ion batteries? After their life in a car they can still be used for stationary energy storage and can be nearly fully recycled afterwards.
- jiveturkey 5y agoA google search tells me there are far more efficient processes available, one almost at 25% efficiency. None of them commercially viable yet.
- woranl 5y agoPeople often say how battery cars are more efficient than fuel cell cars, and we should focus our resources to the former. Some even called fuel cell cars dumb. This is short sighted in my opinion. If fuel cell cars are more popular, it encourages more green hydrogen production and investment. Once there are more green hydrogen, then we can truly decarbonize the chemical and industrial sectors. There are so many industrial processes requiring hydrogen as a reactant. Fuel cell cars can be a catalyst to decarbonize sectors well beyond the auto industry.
- laserbeam 5y agoAnyone who says thay one is better than the other completely misses the fact that we have enough researchers on this planet to work on both. You never know what applications will make sense for each of the techs.
- mlindner 5y agoPeople are usually talking about being against having tax payer subsides for hydrogen powered consumer vehicles being inexplicably higher than those for battery powered vehicles.
- jillesvangurp 5y agoThe challenge is cost of energy production, which translates directly into cost per mile when it comes to hydrogen powered vehicles. That matters because when the choice is pay 1x or 3-5x per mile, it's going to be an easy choice for most and hydrogen is going to lose every time. Hydrogen is simply too expensive per mile relative to other options. That's why battery EVs are so popular; they are clearly cheaper to drive per mile. Especially if you charge them cheaply from your own solar panels, using off peak grid rates, etc. You are basically driving almost for free. In some cases grid operators literally pay consumers to plug their cars in so they can offload excess energy. It's cheaper than shutting down gas powered peaker plants and having to restart them a few hours later. The article is interesting because it proposes a way that gets production to less than 2x the efficiency difference relative to using solar panels to generate energy in terms of efficiencies (12-15% vs 20-25%). That's impressive. However, it says nothing about the cost of hydrogen because this is an academic article and not an actual product. However it suggests an improvement. For reference, producing hydrogen from wind energy would use about 3-4x the kwh in generated electricity to produce 1kwh of hydrogen. That's not bad. But even (wrongly) assuming all of that would be converted to motion, that would be about a 3x cost per mile difference already vs. just putting the wind energy straight in your battery. Burning hydrogen has inherent inefficiencies (you produce heat and noise) similar to burning other fuels (20-30% efficiency would be pretty good). And even fuel cells are not that efficient; 60% efficiency is pretty good apparently. And if you are using hydrogen for fueling vehicles, what matters is the cost per mile. So, on top of the production that would be another loss of about 1.5 - 5x on top of the production inefficiencies. The fantasy of hydrogen in cars and trucks is that it is needed and that the cost doesn't matter. The reality is that there are battery equipped vehicles in almost every weight and vehicle class being produced already with pretty awesome cost per mile that are going to be pretty hard to compete with using hydrogen. It's a no-brainer choice already for a lot of drivers and fleet operators. Sure, their range is not always that impressive. But at about 3-5x the cost per mile difference that's an inconvenience that can be worked with. The other fantasy is that hydrogen is carbon neutral. The vast majority of hydrogen produced is grey hydrogen. If you want to save some carbon, fuel your car using methane instead of hydrogen. You'll produce a lot of co2 but a lot less than when you use that methane to produce hydrogen which you then burn or use in a fuel cell. That's the sad status quo of hydrogen on the road right now. What little there is neither green, efficient, or cheap. Making it green will raise the prices. Making it less inefficient is going to be a long battle, and until that is done, it will be inherently more expensive. Green hydrogen when production of that is going to be more meaningful is still going to be useful elsewhere (aviation, shipping, heavy industries). And with wind and solar intermittency that basically means there are going to be surplusses (rather than shortages) because people will over provision to compensate. Hydrogen is a great way to use such excess energy. There's going to be plenty of demand for it. Just not on the road.
- rdevsrex 5y agoI don't get why people are acting like it's an either or scenario. That said, one pro for hydrogen, is should be easily burnable in the current natural gas plants, which should easily cover off peak times without the need for batteries. Another thing. I think we should question any plan that requires more mass mineral extraction than necessary. It's not as if mining is an environmentally neutral thing, and there is more to restoring our planet that just getting surviving climate change.
- diordiderot 5y agoThe UK is going to mix hydrogen and natural gas through the current infrastructure. They're currently building dozens of hydrogen plants and each one that comes online will increase the hydrogen until it's 100%. Really brilliant as the UK will be way ahead in global production. There's a good YouTube video explainer, search "just have a think blue hydrogen" Here's government link https://www.gov.uk/government/news/uk-government-launches-plan-for-a-world-leading-hydrogen-economy https://www.gov.uk/government/news/uk-government-launches-pl...
- ncmncm 5y agoStupendously massive production capacity of H2 will be needed for every plausible climate disaster mitigation scenario. If you want to synthesize CH4 or other hydrocarbons from captured CO2, or to synthesize NH3 for fertilizer, or for fuel, or for storage, you need H2 first. To fuel aircraft efficiently, you want a great deal of LH2. Anywhere LH2 aircraft fly, kerosene-fueled aircraft will be simply unable to compete. That will start on major international routes, with airports synthesizing LH2 on demand from grid power, banking it when spot price is lowest. The only thing that will save carriers loaded up with kerosene craft is the limit on how fast the LH2 aircraft can be manufactured. Carbon-neutral steel production will depend on really huge amounts of H2, in place of coal or natural gas. Existing fertilizer production lines can inject H2 with the natural gas, and increase its fraction as more becomes available. At some point, as the carbon fraction decreases, electric heating will become more economical than burning injected gas for heat. Ultimately, improving catalysts will make the whole process more efficient than ever. NH3 made with green hydrogen is a likely fuel for retrofitted long-distance shipping, where ships need only new fuel tanks and plumbing to switch over. Probably legislation will be needed to drive this change fast enough. Cars with high-pressure H2 tanks are beginning to be practical, and are much lighter and cheaper to make than lithium-battery cars. When the car is lighter, the motor and drive train can be lighter too, and it takes less energy to accelerate them. In the short term, though, batteries are clearly winning. It is hard to be sure which will win, long term, but batteries have a huge first-mover advantage. You can burn H2 directly in a natural-gas plant, or mixed into natural gas. So, as H2 production capacity grows, an increasing fraction of gas input to these systems will be H2. Ultimately, fuel cells driven from pure H2 will start to take over as prices of improved catalysts fall. For utility-scale storage, bulk underground H2 is a much simpler and more reliable proposition than millions of battery cells, even though round-trip efficiency is poor. As top-line generating cost plummets, efficiency matters less. All the hottest storage systems (iron-air, hydrogen) are low roundtrip-efficiency.
- habosa 5y agoA lot of the discussion here is around hydrogen fuel cells for cars and aviation. Which would be cool. But the real reason we need “green” hydrogen now is for making steel and cement: https://www.vox.com/energy-and-environment/2019/10/10/20904213/climate-change-steel-cement-industrial-heat-hydrogen-ccs https://www.vox.com/energy-and-environment/2019/10/10/209042...
- ncmncm 5y agoIt's a good point: can any imagined use of hydrogen for cars even begin to compete with all the other demands for it? They might always outbid the car owners. For aviation, LH2 has such fantabulous efficiencies that we can expect to see all serious air transport switched over by 2050 (providing civilization doesn't collapse first).
- mlindner 5y agoAviation won’t be using LH2. The volume required makes it not feasible. Not to mention the cooling requirements. Look at the volumetric energy density of it compared to other fuels.
- ncmncm 5y agoVolume is very cheap on board aircraft, so volumetric energy density doesn't matter. What costs is weight. On weight, LH2 clobbers everything, by a very long way. https://news.ycombinator.com/item?id=29206505 https://news.ycombinator.com/item?id=29206505
- twic 5y agoThat article shows a graph of cement cost increases from alternative energy use, and says: > As you can see, every low-carbon alternative raises costs more than 50 percent above baseline. The only ones that don’t raise it more than 100 percent are CCS (of the heat source only), blue hydrogen, or resistive electric in places with extremely cheap and plentiful carbon-free energy. > The alternative that climate hawks would most prefer, the carbon-free option that would work best for most applications, is green hydrogen. But that currently raises costs between 400 and 800 percent. Ouch. Green hydrogen is by far the most expensive option. 3-4 times more expensive than electric heat. That's the direct opposite of "the real reason we need “green” hydrogen now is for making [...] cement". This new work will hopefully make green hydrogen cheaper. But if you're using electricity to make that hydrogen, i don't think it can ever be cheaper than electric heating.
- twic 5y agoThe headline is "solar-driven water splitting", but they do this by building an photovoltaic cell and connecting it to an electrolyser, just like everyone already does. Moreover, the innovation here is that neither the solar cell nor the electrolyser require rare elements. As they say: > Sustainable water electrolysis requires that the anode and cathode catalysts are noble metal free and contain small amounts of other metals in order to lower system costs and facilitate recycling. As for efficiency: > The measured [solar-to-hydrogen] efficiency is improved compared to all previous electrolyzers driven by low-cost [perovskite solar cells] that used solely Earth-abundant electrocatalysts but lower compared to the highest performing perovskite/Si tandem devices that uses noble metal electrocatalysts, which reached an initial efficiency of 17% [solar-to-hydrogen]. So this setup is less efficient than what we already have. But it doesn't require rare elements.
- jakozaur 5y agoThe best way to understand hydrogen is Liebreich Hydrogen Ladder: https://www.rechargenews.com/energy-transition/liebreich-oil-sector-is-lobbying-for-inefficient-hydrogen-cars-because-it-wants-to-delay-electrification-/2-1-1033226 https://www.rechargenews.com/energy-transition/liebreich-oil... The best use cases for hydrogen are fertilser or in hydrocracking. We currently use primarily natural gas to produce hydrogen. Urban or commuter cars are one of the worst use case for hydrogen. Electricity and batteries are way better.