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from the the-Hindenberg-steam-engine-crossbreed dept.
‘They said we were eccentrics’: the UK team developing clean aviation fuel:
“Anyone passing would have wondered why these people were staring at a pipe and whooping and laughing,” says Bobby Sethi, associate professor of gas turbine combustion at Cranfield University. “But we were almost certainly the only people in the world right then burning anything without producing CO2.”
[...] “We were able to demonstrate successful ignition and safe combustion of pure hydrogen and air at high temperature and pressure – producing no carbon emissions,” he says. Even if, he adds, the passing layperson would have only seen a pipe and some steam.
[...] Sethi recalls the scepticism of even five years ago, when he was pursuing funding for the hydrogen research project, known as Enable H2: “They said we were eccentrics. Now they’re queueing up to be on our advisory board.”
There are broadly three strands of work that the aviation industry is frantically investigating for an environmentally acceptable future. One is to create greener fuels for the large aircraft currently in service. A second is electric flight, which appears feasible for smaller aircraft and short-haul hops. And a third is hydrogen.
Two projects pioneered at Cranfield are using hydrogen in the form of fuel cells to power electric motors and propel planes: ZeroAvia flew a six-seater from here last September, and hopes to scale up the technology for commercial short-haul flights in the coming decades. Another, Project Fresson, is planning to use fuel cells for a green, short-hop passenger service around the Orkney islands as soon as 2023.
But the ambitions for direct combustion of hydrogen are on a bigger scale; whether a radically different plane and propulsion system could replace the modern, paraffin-fuelled passenger jet. Which is where Sethi’s research comes in.
Nothing yet in the sheds looks anything like a plane. The rig here is a unique facility, Sethi says, assembled to show that hydrogen can be clean, safe and efficient for aviation, and produce data showing the optimum temperature and pressure to minimise other harmful emissions such as nitrogen oxides or NOx, a family of highly poisonous gases.
Not the only scientists looking for controlled ignition of hydrogen. What's described still seems a long way away from something that produces thrust, which is the ultimate need. However, technology usually advances in small steps, and that's fine as long as there's an ultimately reachable goal.
(Score: 4, Insightful) by ElizabethGreene on Friday August 20 2021, @03:48PM (8 children)
Raise a skeptical eyebrow whenever someone calls hydrogen "green". 96% of hydrogen is manufactured by steam reformation of fossil fuel. It's critically important to understand what is greenwashing that makes people feel good vs. what actually has an impact. Without a sea change in hydrogen production it is firmly in the greenwashing camp.
It is possible to make it via electrolysis or photoelectrochemical processes and it's possible to get the energy to do those things from clean/renewable sources. Until that happens burning or fuel cell electricity from hydrogen will produce more CO2, not less.
(Score: 2) by Sourcery42 on Friday August 20 2021, @04:47PM (4 children)
You are absolutely right. There's no CO2 in the tailpipe of the mobile source, but there's an enormous tailpipe on the traditional SMR plant.
There is electrolysis, but it takes a tremendous amount of energy to convince water vapor to split apart. That's why we reform hydrocarbons into hydrogen rather than splitting water via electrolysis. Hydrogen has pretty terrible energy density per unit volume too. It is just hard to get excited about it as a transportation fuel. However, I can envision it serving a role as something more like a battery. Generate hydrogen with excess solar/wind/nuclear energy when there is a surplus. Burn it or put it through a fuel cell to generate electricity when the sun goes down or the wind stops blowing. Hydrogen takes on the role of the peaking plant today. It could be viable until we find a good way to make cheap, massive batteries.
One thing that becomes clear as you look into the details of green energy is that there is going to have to me truly massive investment to meet aggressive carbon goals with the tech we have now. Someone is going to bear that cost of capital. I grit my teeth when I read articles in business journals predicting energy is nearly free in the not too distant future because it is all green/renewable.
(Score: 2) by ElizabethGreene on Friday August 20 2021, @09:31PM (3 children)
I'm optimistic about a significant drop in energy prices IFF we can sort out and scale out orbital solar power.
There are two caveats to that.
1. I can be a Pollyanna about the rate of technical progress.
2. Only a blithering imbecile would believe that big energy, a multi-trillion dollar industry, is going to take that kind of innovation without fighting back. They have lots of experience doing it to discredit climate change. This will be that 2.0.
(Score: 2) by Immerman on Friday August 20 2021, @10:43PM
Sadly I smell a lot of "if" on this plan.
Currently we have no proposed way to build orbital solar plants that aren't far more expensive per kWh than ground-based alternatives. Even worse, despite decades of research we currently have no technology to get any such energy to the ground even from LEO without truly stupendous transmission losses.
We could sort of sidestep those issues with relatively cheap huge orbital mylar reflectors that simply keep ground-based solar fields illuminated 24/7. That also slightly mitigates the "orbital death ray" potential, since even from LEO the smallest bright spot that could be reflected onto the Earth would be about 3 miles across, up to about 200 miles across from geostationary.
Of course, if you presume that orbital solar becomes the primary source of energy you're still talking an average of around 465GW of total solar energy - focus all of that onto the same 3-mile circle and you're talking about 25kW/m^2, or roughly 25x the energy density of tropical noon sunlight. I'm not sure that's enough to burn down buildings, but I'm sure it would rapidly destroy crops.
(Score: 0) by Anonymous Coward on Saturday August 21 2021, @06:16AM (1 child)
Orbital solar is already dead. [wordpress.com] Modern solar panels are more space and cost efficient than orbital power receivers. Even if the satellites were free, ground based solar would still be cheaper and take up less space. The only way space based power can compete now is to increase the flux density to dangerous levels, injuring or killing anything that gets too close to the ground stations.
(Score: 2) by Immerman on Saturday August 21 2021, @10:04PM
Orbital solar is more valuable for solving the storage problem - ground-solar generates near-zero power form most of the day (night), including those times when energy consumption is highest, and can be offline for weeks at a time if the weather is particularly uncooperative. The problem orbital solar really solves is eliminating the need for storage, since it can generate power 24/7, and clouds are transparent to properly tuned microwave power transmission. Even then though, there's a lot of storage systems far cheaper than an orbital solar array.
Orbital sunlight concentration might have interesting potential though - giant utra-thin mylar mirrors could be vastly cheaper than solar power stations, and refocus sunlight on ground-based solar plants throughout the night. By maintaining noon-time illumination levels 24 hours a day you'd be pushing 5x the daily energy production, without any "dead times". Assuming a large swarm in low orbit serving sites around the world, you could potentially even selectively re-target a protion of the redirected sunlight from areas passing through the low-demand part of the daily curve, to those currently experiencing high demand. You could probably even increase light levels to a few times natural noon-time levels without presenting an immediate survival hazard to anyone in the area. Though even just sustained noon-time levels would likely make the area unpleasant enough that almost nothing would live there. Though I suppose polar regions might flourish - you could create "islands" that never suffered the winter loss of sunlight, maybe even seeing an increase to compensate for the surrounding cold. Come to think of it, you could probably do something similar to create oases of optimal year-round growing seasons anywhere on Earth.
(Score: 2) by Immerman on Friday August 20 2021, @10:17PM (2 children)
Hydrogen is exactly as green an energy storage medium as batteries - which is to say it depends entirely on where the energy is coming from.
Steam reformation is currently the dominant way to produce hydrogen, just as fossil-fuel power plants are the dominant way to charge batteries. In and of themselves, neither technology does anything to combat climate change.
That said... you are absolutely right that much of the hydrogen push has been heavily backed by the fossil fuel industry as a way to remain relevant by greenwashing an inefficient derivative product. But you could make a similar argument that EVs greenwash the fact that your car is still powered by burning fossil fuels. Though at least the power plants tend to do so more cleanly and efficiently than car engines - though electric transmission losses eat a lot of those gains.
Ultimately, neither technology is inherently green. Instead they shift the dynamic from end-users generating CO2, to the infrastructure generating CO2, so that your 10 year old electric or hydrogen car will "magically" become greener as the infrastructure is updated.
It worth mentioning too that, whether you're generating hydrogen or electricity, the current production capacity is only just adequate to existing consumption, and we'll need to add new production to supply the demand for transportation. Electricity currently has a slight advantage, with solar electricity actually being slightly cheaper than coal-generated, but supposedly water-electrolysis hydrogen is already only very slightly more expensive per-unit than steam-reformed, though the electrolysis plants themselves are still more expensive.
(Score: 0) by Anonymous Coward on Saturday August 21 2021, @06:33AM (1 child)
Even ignoring distribution costs, internal combustion engines are only around 20% efficient. Even including distribution costs, BEVs are about 40% efficient. Assuming that all hydrogen is produced by electrolysis the BEVs would only need half the increase in electricity production of hydrogen powered cars. That is more than a slight advantage.
(Score: 2) by Immerman on Saturday August 21 2021, @09:18PM
There's also fuel cells, which can be considerably more efficienct than ICEs. But yes, it seems like hydrogen is going to be less energy efficient than batteries unless some other major advance comes along.
*However* it's much greater potential energy density that could make it a better option is specific cases. Probably not for passenger cars, assuming enough batteries can be made. Different compromises for different use cases. Existing batteries are physically incapable of storing energy densely enough for long-haul aircraft, shipping, trucking, etc., so it makes no sense to compare against them in those applications.
Existing batteries also still require a whole lot of elements whose production is going to be a major bottleneck in dramatically expanding the EV and solar/wind energy storage markets. Hydrogen doesn't share those resource bottlenecks, and can still be a huge improvement over fossils fuels.