exchemist

I really don't think you can do that calculation. We do not know what the cost of hydrogen produced on this scale will be. That depends on such variables as the cost of electricity, which is notoriously variable and will change as the economy decarbonises, the efficiency of the technologies for hydrogen production, of which there are at least two: green hydrogen from electrolysis, and blue hydrogen from steam reforming of methane plus CCS, and the demand for hydrogen from the various applications that could potentially use it, some of which I listed in my previous post. So neither manufacturing cost nor supply and demand balance can be readily estimated - though I feel sure people investing in the business, like Shell, will have some models. As for the ships themselves, a lot may depend on whether they would burn hydrogen in a heat engine as today or whether a move to fuel cells proves feasible. None of the likely costs of these changes is yet known.

Like @studiot, I'm having some trouble following what you are saying. You can't "negotiate" with electrochemistry or physics. Do you mean "optimising", by reducing losses or something? Also there is nothing fundamental about any of the formulae in this thread so far. All we have covered is the arithmetic to work out a % efficiency, given certain measured inputs and outputs. I think you need to be a bit careful what is meant by efficiency in the context of charging and discharging a battery. I see that @studiot has used it to mean the efficiency with which a given electricity supply, as input to a charging system, results in actual charge entering the battery. So that's the efficiency of the charging process. However the figure of 80-90% I was quoting is the efficiency with which the battery itself stores charge, i.e. the amount of charge you get back out for the amount you put in. This is the charge/discharge efficiency. What is the formula you are referring to?

Just to clarify your point (1), where CO2 appears in a ranking by concentration in the atmosphere is irrelevant. What is relevant is the degree to which a gas absorbs IR radiation. The principal gases in the atmosphere (N2, O2, Ar,) do not absorb at all in the IR. They are transparent to it. Neither N2 nor O2 has a dipole in the molecule for the IR radiation to couple to, which is what one needs to get a molecule to absorb and vibrate. Ar is a monatomic gas, so there is nothing to vibrate and so it can't absorb at all in the IR region. The first gas on a list, in descending order of concentration, that has a dipole and can absorb in the IR is H2O, followed by CO2. So forget about CO2 being "near the bottom" of the list, at "only" 0.04% of the atmosphere. That tells you nothing of relevance in this context.

You flatter yourself.

I don't think that is right. The NASA link I provided seems clear that water in the atmosphere has a warming effect overall. The way I read the extract you supplied is that clouds mitigate the greenhouse warming due water vapour - and maybe prevent it running away. How do you come to the conclusion that water in the atmosphere - in all forms, vapour and clouds - has a net cooling effect?

I'm not sure what all these numbers tell us. The energy content is the same regardless of the fuel used. There is a certain efficiency limitation for the production of hydrogen, depending on how it is produced. Those numbers together tell us how much energy would be needed to fuel all these ships. The amount of hydrogen that one part of one company currently says it can produce is not really very relevant. So much depends on how much money the energy industry feels it can make out of supplying it and a lot of that will depend on what other (higher intrinsic value) applications there may also be for the fuel. In the case of hydrogen there are potential applications in domestic heating and as truck fuel. But in any case, I'm not sure that hydrogen is the right fuel to focus on, at least in the medium term. Hydrogen is currently not the most favoured future option for marine bunker fuel. Here is an article about the options from Bureau Veritas: https://marine-offshore.bureauveritas.com/insight/future-marine-fuels-pathways-decarbonization Decarbonisation will be a process, taking decades and most likely involving a number of intermediate steps. You will see that less carbon-rich hydrocarbons, and/or liquid biofuels, are likely to come into use first. Longer term, hydrogen is one possibility certainly, though not on any scale by 2030, while ammonia may well be preferred to hydrogen, due to the easier storage on board (you can liquefy it). Though to make the ammonia you presumably need the hydrogen anyway, so eventually a lot of it will no doubt be needed, one way or another. (You can make "blue" hydrogen from natural gas, if you capture and store the CO2 generated as a byproduct.) If you are really interested in this subject, there is information available on the internet from organisations such as the IMO and CIMAC (a forum for marine engine designers and builders that I used to attend, when I was still working for Shell).

You are for some reason not getting my point. Clouds are water in the atmosphere, but not all the water in the atmosphere is in the form of clouds. There is also water vapour.

This extract does not say that atmospheric water has a net cooling effect on the earth. What it says is clouds have a net cooling effect. As I understand it atmospheric water has a net warming effect, being a blend of IR absorption by vapour and the cooling effect of clouds. In fact, the extract you posted says without clouds the water vapour might lead to a runaway +ve feedback loop. The net effect of water in the atmosphere is described here: https://climate.nasa.gov/ask-nasa-climate/3143/steamy-relationships-how-atmospheric-water-vapor-supercharges-earths-greenhouse-effect/

Yes, as Ken Fabian and I have been saying, if you put more water vapour into the atmosphere, you don't change anything. To put this another way, the water in the atmosphere is, overall, in equilibrium with the vast excess of liquid water that is in the oceans. Evaporation and condensation and precipitation are occurring all the time. So the net effect of adding water vapour by burning a fuel containing hydrogen is that a tiny bit more rain falls at some point, thus correcting the imbalance that the extra water vapour introduces. HOWEVER, the equilibrium position is temperature dependent. So if a permanent, or long term, greenhouse gas increases the mean temperature a bit, then the equilibrium position shifts, in favour of more water vapour in the atmosphere, which warms it up more than the effect of just the greenhouse gas alone. In this way water vapour amplifies the effects of the permanent or long term greenhouse gases. At least, that's the way I understand the process (I'm not an atmospheric chemist).

No, because water vapour doesn't accumulate. It precipitates as rain. This is what is meant in @Ken Fabian's post above, which says water vapour does not itself cause a warming trend, although it amplifies any warming trend there may be due to persistent greenhouse gases.

Do you really think a millenium is the same as forever? You wouldn't be much good at geology.

I don't think your last para is entirely right. HFCs, which have been widely used to substitute for the ozone-depleting CFCs and HCFCs phased out under the Montreal Protocol, are actually very potent greenhouse gases. So now there is a drive to replace these too as refrigerant fluids, with things like ammonia, CO2 and hydrocarbons.

My understanding is that a modern Li ion battery has a charge/discharge efficiency of 80-90%. 75%, let alone 67%, seems low to me.

What sententious garbage. Freedom of speech does not require that you be free to talk crap wherever you like.

I'm terribly out of date I'm afraid, as I have not used a vacuum line since my university research, over 40 years ago. I recall being impressed with the mercury diffusion pump, though it was a bastard if any gas got past the liquid N2 trap and reacted with the mercury. I had some trouble with nitric oxide, if I remember correctly.

If you jerk a rope, you displace a portion of it upward from its lowest energy state, which means you put gravitational potential energy into a section of the medium (the rope). The portion of the medium that is displaced upward then travels, but the energy is still at all times in the medium, just not always in the same part of it. In the case of the photon, the energy is in the travelling disturbance in the electric and magnetic fields. You can certainly say the photon is the energetic occurrence, but the energy is still in the fields. Think what happens when a photon is absorbed by an electron in an atom. The changing electric field of the photon creates a forced oscillation in the electron (using classical language, more properly a "transition dipole moment") that moves it to a higher energy orbital. So it's the oscillating field that gives up energy to the electron. It's essentially the same as happens in the antenna of a radio receiver, but on a smaller scale.

But be careful. Notice Einstein spoke of wave-packets, not energy packets, in line with what I said previously. The light quantum refers to the observation that the energy in light is only transferrable in discrete portions, which he called quanta. That does not mean light is "made of" energy. E=mc² is the simplified version of a longer formula: E² = (mc²)² + p²c², in which p is the momentum of the entity in question. For an entity at rest relative to the observer, p=0 so it reduces to the familiar formula. However for a photon, this does not apply. On the contrary, for a photon, m=0, so the expression reduces to E=pc. (If you apply de Broglie' relation to that, by which p=h/λ, and use the fact that c=νλ, you get E=hν, Planck's well-known formula for the energy of a photon.) I agree "stuff" is not a precise term. What I was trying to say, in colloquial language, is that energy can't exist on its own, any more than momentum can, or electric charge. None of these is something you can isolate. You can't have a jug of momentum or a bottle of electric charge. They can only exist as properties of some physical system, by which I mean one or more material entities (whether QM or classical) or fields. A wave is a system that in general comprises a medium (which is physical, i.e "stuff"), physically disturbed from its equilibrium state, with the result that the disturbance propagates through the medium. To disturb it from its equilibrium state requires an energy input, so yes, a wave has energy in it. An EM wave is a bit of a special case in that the "medium" consists of electric and magnetic fields which oscillate. But fields are physical too: you can get a spark from the stored energy in an electric or magnetic field under the right conditions e.g. the pop you hear when the older type of electric train suddenly cuts off the current in mid-acceleration, due to the collapse of the magnetic field in the windings. The energy is a property of the field, not something in its own right. In summary both entities with mass and waves "have" energy, as a property, but this does not mean either of them "is" energy.

A photon is not, or should not be, described as a packet of energy. Energy is not stuff. It's just a property of a system, like momentum. A photon is not "made of" energy, it "has" energy - along with a number of other properties. A photon is sometimes described as a wave packet, https://en.wikipedia.org/wiki/Wave_packet , but not an energy packet. Systems that move (relative to others) and have energy will naturally carry that energy with them, so yes, that energy moves, but only as a result of belonging to the system that moves. To describe a photon as moving energy is not correct. Similarly a ball is a physical object - a system. It has mass as one property, and that mass is associated with a rest energy by E=mc². But the ball is not "composed of" mass, so it is not "composed of" energy either. It has both mass and energy, along with radius, colour, maybe spin, smell.......etc. All these are just properties of the ball. It is the ball that you toss in the air, not any one of these properties.

Thanks, very helpful. So, if I try to summarise, as it is impossible to evaluate all drug-drug combinations, knowledge of the mode of transport and mode of action of a drug is used to predict what interactions with other drugs might be expected, and priority is given to checking these combinations. And then, after introduction of the drug, there is a catch-up process, to flag any further interactions discovered in clinical practice. What seems still unclear is what requirements there are, if any, to check out potential interactions as part of the regulatory approval process.

More gibberish. I'm out.

What are you suggesting might have been “deep faked”, then?

As a chemist, I am conscious that a real physicist my pop up and shoot me down, but I think you have to start again with the system as it is after the interaction. Energies, potentials, momenta etc may have changed, so you have a new state, with a new Hamiltonian (a mathematical description of the total i.e. potential plus kinetic, energy of the system) in the Schrödinger equation. In many cases you can work out what this will be from the nature of the interaction, e.g. absorption of a photon by an electron in an atom. But you generally would need to solve the equation again, I think (except I suppose in very simple cases, like an elastic collision or something, where you may get away with just changing the phase.) The relationship between the two wave functions itself won't be probabilistic, since each is a defined mathematical expression. But each expression is a probability-based description of the system.

You can read about it here: https://bletchleypark.org.uk/our-story/bletchley-park-and-d-day/ Though what this has to do with moon landings, or secrets kept by the state. I don't know - unless you mean the Enigma-coded messages sent by the German military.

Is that entirely right? Surely even a single solution to Schrödinger's equation is still a "monochromatic" wave function, describing in effect a probability density over space, rather than a specific location at which the QM entity might be detected. In which case, "collapse" represents detection (or interaction) at a specific location, with a likelihood predicted statistically by the (single) solution (wave function).

Ah yes, the telltale "ya" makes its appearance: in my experience a sign of aggression as a substitute for rigour. Your penultimate paragraph reinforces this impression, being merely a rant against some imagined foes, rather than advancing a coherent argument. But the rest seems close to word salad. This stuff about 3 points on a graph is a clunky pseudo-mathematical way to say something simple, viz. that different parts of your body are at physically distinct locations. You then go on to say something that appears to be simply wrong, namely that sensation is experienced at all three parts of the body simultaneously, when it is a known fact that nerve impulses take time to travel. (By the way, "the proof is in the pudding" is nonsense. The expression is: "The proof of the pudding is in the eating".)