Clark01

You can do this at very low % of hydrogen- a few % at most, and the rest of the gas is methane. They've done this "hydrogen sweetening" successfully in the UK. But as soon as you get to a higher % of hydrogen, you have big problems with metal embrittlement and leakage. Which means you need to rebuild the infrastructure with different materials.

A real-world, in-practice fuel cell in a moving vehicle is only 30% efficient. Maybe slightly more, but basically the same as an internal combustion engine. That sucks, and makes Everything Hard. This article gives a bit of info (yes, its hardly impartial, but there's plenty of others.) Fuel cell proponents often get tricky and claim high efficiencies, but they are either for fuel cells operating at very high temperatures, which may work in a stationary application but doesn't in a vehicle. Or they are claiming utilisation of the waste heat from the fuel cell, which again, in a vehicle isn't realistic. Cryogenic hydrogen is difficult for lots of reasons- its damn expensive (in energy terms, and thus also cost) to compress to that level. And when stored, you end up with significant wastage through boil-off. This is why a great deal of vehicular "hydrogen" work these days is looking at other carries for the H+, such as ammonia. Yes, the Mirai exists. But it is crazy expensive (again, its an EV + a fuel cell + a storage tank + hydrogen safety gubbins). The volumetric "efficiency" of the car is nothing like an EV (damn tanks), and there's only one place in Australia you can refill it. I

Well... quoting range on cars is standardised. Across the world, using the WLTP cycle. The identical cycle is used for EVs and dyno-burners. And aero drag goes up exponentially (actually, its a cube-law-thing!) for all vehicles. 😀 In the WLTP cycle applicable here they go up to 131km/h. A variety of speeds & durations are used through the test, and you can argue whether this is "realistic", but it is standardised, and does allow like-for-like comparisons. I just don't really buy the "long range" argument when plenty of EVs today approach 500km of range, at speed. Sure, there are edge cases of farmers and others who drive long distances, at speed, where there's no infrastructure, and they have a heavy load. Great, these guys can continue to use fossil-fuel cars. But the average daily distance a car drives in Australia is something like 60km. There is a huge number of vehicle use cases where EVs make sense today, albeit their economics are still a challenge. The top selling new car in Australia is the Toyota Hilux. Number 2 is the Ford Ranger. These aren't $26k vehicles. They're $50k+ vehicles. I think it reasonable to say that many American vehicles are used similarly to how we do in Australia. The Rivian R1T, the F150 Lightning, etc, are EVs that all have high GCMs, long range at high speed. The clincher is they will cost over $100k in Australia. But time will change that. In the meantime, there's plenty of families who have two cars, and an EV makes an easy replacement for the "runabout". I think I'm trying to say that this world is changing very quickly. Long distance at heavy loads is hard. Flying a plane long distance at high speed as an EV is hard. Energy density is a thing! But these are edge cases. There's a whole lot of cases in the middle that make sense, and we're going to see huge change here over the next few years.

Indeed. Fully agree with this definition of "baseload". The difference is that in much of the political, and somewhat media, debate, the statement is we need more baseload. And the reality is the opposite. The last thing we need is a generator than can't ramp down below a certain point. This is one of the key challenges to the coal fleet- they can't ramp any lower, and, as you say, market prices end up negative- the coal generators have to pay to remain connected. That's not a long-term sustainable solution. Its hard to respond to this without seeing data. But the AEMO dashboard publishes the energy mix in real time. Right now coal is meeting 49% of total demand across the east coast. And I can't recall seeing a time where renewables has been 1% of national electricity market (NEM) demand for...years. I'm being deliberate in referring to the "NEM".. That's the whole idea of an electricity "grid"- it provides geographical diversity, so that the places its not sunny, you can import solar from where it is sunny. Before solar and wind, we did the same with coal, gas and hydro- importing hydro from the snowy into QLD at times of peak demand (a hot afternoon in Brisbane). Cherry picking a particular city or geography and saying "this area isn't operating on renewables because it isn't sunny or windy right now, and so renewables can't work" is just that- cherry picking. It misses the entire complex mesh that is a modern electricity system. This is the pessimistic way of representing the situation. An alternative portrayal would be to say that "If you build enough renewables to meet our maximum demand, then there will be many periods where we have excess, and thus very low price (free, possibly even negative price) energy". That "free" energy can be used for all sorts of thing- making hydrogen, desalinating water, soaking up CO2, making synthetic fuels, etc. The reality is there's a hell of a lot of renewables still to be built, (AEMO provide very clear forecasts). As we do that, we will have periods, like SA last weekend, where there are areas with excess generation capacity. Historically people curtailed (turned off) generators during these times. But even then, the plant keeps getting built, so the economics work. And today, plenty of industries are realising that if they can be flexible in their demand, we can soak up the excess supply to make the sorts of things I reference above. A domestic version of this we see in household pricing- you refer to off-peak hot water control, which was designed to soak up excess capacity in the middle of the night (to keep boilers warm). Today we see the same thing happening in the middle of the day- there are tariffs that have lower prices in the middle of the day, to encourage people to turn things on when we have excess solar. This has been a long-held fear, but its just not true today. Literally today, AEMO have declared we'll be ok, although there's some risk of "extreme events". That's always been the case. And the risk is actually because of coal units that have been lost- Callide had a fire, Yallourn had some flooding issues, and a bunch of gas is offline.

Ooh. And don't even start me on "baseload". Its such nonsense. A term power system engineers used, that was misused for political purposes. We DO NOT need more "baseload". The Australian Energy Market Operator, the people who run our energy system, make this very clear in documents like this one - what we need is more flexible generation, that can follow changes in net demand. Yes, in an old world we needed baseload. But that world doesn't exist today due to massive changes in our demand (think- things like air conditioners which double demand just a few days of the year) and supply (intermittent solar and wind). There was a period last weekend where South Australia had 135% of its demand met by wind and solar alone. The excess energy was mostly exported to Victoria. Over a 48 hour period wind and solar met 108% of demand, and over a 93 hour period they met 100% of demand. Sure, there's very major challenges to operating a power system with so much wind and solar, and SA relies on interconnection to other states to keep things reliable. But don't mistake "its hard" to "its impossible".

For a bunch of technology-types, there's some pretty, err, fascinating reading here! I'll try to put the climate-science debate aside. But to say- in what other area of science, when 98% of the science experts in the field say something is happening, do we say (with imagined authority!) "Oh they must be wrong". Have a look at the climate skeptics regularly referenced in the Murdoch Press. Its the same 2-3 people all the time. And none of them are climate scientists- mostly they're geologists. This little YouTube video explains the issue well. Climate change is real, and we have to do something about it. That's hard. And fossil fuels are very energy dense. Which is hard to replace. There's nothing new about hydrogen. We're in at least the third hydrogen hype cycle I've seen. Have a read of the book "They Hype About Hydrogen", written in 2004. There's even been hydrogen aircraft- see the TU155 for example. Today, governments around the world (including Australia) are funding lots of work targeting "green" hydrogen at $2/kg. They hope we'll get there by 2030. Changing units around, that works out at ~$16/GJ. The last 12 months, natural gas has been around $5-$8/GJ. Hmm. Tough market for hydrogen at $2/kg! And the $2 price doesn't include storage or transport costs associated with hydrogen. It is far less energy dense than natural gas- so you need around 3-4x the storage. And it makes a lot of pipe materials brittle. Not to mention it burns colourlessly, is hideously explosive, etc, so HSE costs are far greater. All in all, for hydrogen to compete against natural gas, something will need to change the economics dramatically, even at our hoped-for goal of $2. That something is either legislation, or a carbon price. Good luck with that! Additional thoughts: I've plenty of experience trying to burn hydrogen in a reciprocating engine. It works. Kind of. They did it in WWII. JCB are doing it now in tractors. There's been lots of research in Australia on it. But the engines don't last very long. Due to how easy it is to get the hydrogen to burn, its very difficult to precisely control ignition timing. So you end up with a lot of knock, and the engine wears out. There's also issues with lubrication, etc. Fuel cell vehicles need a large battery, as fuel cells can't ramp up/down in power output very quickly- so you need a battery as a buffer. So in practice, a fuel-cell EV is actually an electric vehicle, plus a hydrogen tank and fuel cell. I'm not a smart man, but that makes the economics of FCEV vs EV pretty clear.. For passenger cars, this talk of EV and range issues is nonsense in 2021. There are plenty of EVs that have >500km range. Some you can buy today in Australia. The latest Hyundai EV, the Ioniq 5, has a range of 480km, and can recharge from 10-80% in 18 minutes. Show me a petrol car journey where someone drives 480km and doesn't stop for at least 18 minutes... Sure, to get that sort of recharge rate you need the latest EVs and the latest standard chargers. And there's not many of these in Australia. But the technology can do it, and it exists at scale already. Just not here. Sigh. Sure, the Ioniq 5 is not a cheap car, at around $72k in Australia. But you can buy an MG ZS today in Australia for $40k, with close to 300km of range. The direction of this industry is clear. The talk that EVs can't tow is, again, old fashioned nonsense. The Rivian R1T (announced for Australia, available in the US) and Hummer (about to be released in US) have towing capacities in excess of 3500kg. Their range unladen is 500km. Someone has already towed a large car across the US using a Rivian. Yes, it was a bit of a PITA, but it is doable. Average car changeover time in Australia is 8 years, which makes things slower here.. Electric short-journey buses are happening in large numbers in the US and China. The economics work for shorthaul. EVs work, and will be everywhere in passenger cars, even in our neolithic Australia, over coming years. I won't hold my breath for a hydrogen-powered truck. Or plane (beyond some research project). There's plenty of examples of electric short-trip aircraft. They make sense for training and what I think of as the "jet ski" model- go for a short buzz for sh*ts and giggles. Very low cost to operate. Bugger all noise. Fossil fuels are energy dense, and hard to replace. But we can address a lot of our climate challenges doing the easy stuff- convert the short-haul and passenger car fleets. That leaves lots of fossil fuel in the ground for long-haul transport. And we deal with those CO2 emissions some other way. -C

Thanks for the comments. Ian, your recent experience is particularly helpful. Can you give me any specifics on the compressed approach you took? How long were the two periods, how many hrs/day, and who'd you do it with? I'm unsure if there will be many Australian flight schools open to the idea, or who run such courses with a private focus (as opposed to a CPL-aimed route). Also nice to read your thoughts on the level of technology, which I agree strongly with. Once again, I understand the value and importance of airmanship and fundamental skills & experience. And the distraction risk provided by some tech farkles. But. Heck, my lawnmower is fuel injected now! Technology can further reduce risk, and make things significantly safer. I appreciate I likely have little choice with the type and age of aircraft I'll learn in. But its a bit like my daughter signing up for driving lessons, and an instructor turning up in a 1960s Holden with a three-speed non-synchro manual transmission, choke, and single-speed wipers. "You gotta learn how to handle a real gearbox and engine, and drive to the conditions".. Well, no. We reduced task loading and made things safer with the tech. If I wanted to learn on a vintage aircraft, and enjoy that experience for what it is, awesome. I like old cars. But to reduce the risk issues discussed in this thread, I'd prefer to take advantage of technology for most of my time. If it was possible. -C

Hi there, Long-time lurker, who's finally saved up the cash and time to start their journey to PPL. I've done plenty of reading, but looking for some up to date advice.. I'm certain I want to get to the PPL stage eventually, as my interest is in flying cross-country with wife and 2 kids. Eventually. That said, I suspect the majority of flying will be by myself. I'm a technologist at heart, and the idea of learning to fly in a fully analog, carbureted aircraft that is older than I am is something of an anathema. However I understand that the digital farkles have nothing to do with airmanship, etc. But aircraft with modern construction techniques, digital interfaces and control systems definitely attract me. Its just hard to swallow that that my <$1000 drone has better "avionics" than the plane I might be learning on. So to the questions! -I'm aware of the route RAAus licence then to RPT and PPL. I'm finding it hard to get estimates of the actual cost savings here, and any downsides of this path. The cost savings don't seem that significant? Its somewhat attractive because the RAAus aircraft seem more modern and affordable to purchase, and I could imagine myself flying them more even with my full PPL, simply because of lower hourly rates and more modern aircraft. Then just rent a VH aircraft for when with the family. But am I better to just "bite the bullet" and go the GA route, get my PPL, then go to RAAus? -This will only ever be a hobby for me. But I'm tempted by the "compressed" or "intensive" courses- there are schools in the USA that offer PPL in ~ 1 month full-time. Ignoring COVID dramas, they historically seem to be cost-competitive, and the aircraft are more modern. Has anyone gone this route? Do PPL in the USA, then transfer back to Australia? -Is there any similar form of "compressed" or "intensive" learning available in Australia, for people only interested in amateur flying? Ive seen mention of multiple-day training in places like Cowra, but not necessarily for total beginners? The larger flying school full-time courses are more aimed at CPL, and that's not what I'm looking for.. -Home is the Newcastle area. So if there's recommendations of places to go (to learn), or not go, I'd love to hear them. And again, I'm quite open (indeed, attracted by) more intensive options where I travel somewhere and bunk down for a month to focus on learning to fly.. Thanks, -C