kbd512 is a member of the NewMars forum who frequently contributes long posts which are rich with detail, and show careful thought in preparation. In the post below, kbd512 looks at a variety of options for human beings to address climate change, and offers recommendations based upon various factors.
Readers of luf.org should be aware that kbd512 posts on a variety of topics, some of which might be offensive. The post below confines itself to physics, economics and technical fields, so should be acceptable in this setting.
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I take no issue with the various attempts to use the Sabatier reaction to produce CH4 for rocket fuel and energy storage, but thus far the R&D efforts to do that seem pretty lack-luster. Efficient CH4 synthesis is nowhere near as advanced as water electrolysis technology used to produce H2 and substantially more complicated in operation, as the infographic SpaceNut reproduced in Post #80 illustrates. We already have multi-megawatt reverse fuel cell H2 production plants in operation around the world in every climate imaginable and they fit inside half-length CONEX boxes. They’ve been in operation for many years now and function reliably for many tens of thousands of hours without significant maintenance, or any maintenance at all in most cases, using intermittent solar and wind energy. Oddly enough, that was how they were designed to be used from the outset and probably why they work so well. None of that should be taken to mean that we shouldn’t perfect Sabatier reactor technology to add to our suite of Mars survival tools, but it’s clearly going to be an uphill-all-the-way battle. No doubt Louis will take issue with my assessment, but I’ve yet to see any compact and lightweight industrial scale (multi-MW) Sabatier reactors in operation here on Earth. That should be an indicator that there’s no other demonstrated use case for such technology (industrial scale CH4 synthesis, not the Sabatier reaction), unlike water electrolysis. As long as we have so much gas coming out of the ground that we have to flare it off every time we drill a well, that’s unlikely to change until governments / academia / venture capitalists decide to develop it for Carbon-neutral fuels or making rocket fuel on Mars.
In any event, regenerative fuel cells reacting O2/H2 still outperform batteries on energy density by at least an order of magnitude and fuel cells as a general technology class are right up there with the most highly refined gas turbine designs in existence in terms of mean time between failures- something that no conventional battery technology has ever demonstrated. I’ve never seen a gas turbine spool up to 100% of its rated power in less than 5 seconds, nor am I aware of any that operate most efficiently at less than maximum rated power (not the same thing as burning less fuel at significantly reduced power output; those aerodynamics and thermodynamics issues are a real PITA). The consumable replacement parts for fuel cells are also very lightweight and compact, mostly limited to seals and membranes that can be quickly replaced by unskilled laborers using hand tools. As an added bonus, especially given the dearth of gas stations on Mars, the fuel efficiency of a prototypical fuel cell also happens to be roughly double that of a gas turbine. Apart from the wildly disproportionate energy density advantage provided by nuclear fission, until we can combine all of those highly desirable characteristics into a battery design, a regenerative fuel cell is the most likely candidate for conventional backup power on the scale of 100’s of kW’s or less. IIRC, until your power output requirement is in the multi-MW range, no reliable combustion engines (non-race-car engines) compete in terms of power-to-weight with fuel cells (I believe the US Army determined that not even their 1MW output AGT-1500’s that power their M1 tanks could compete with fuel cells in the PWR department). Since the same units that perform the O2/H2 separating would also provide the power, we’re unlikely to produce lower-mass alternatives.
Anyway, my $0.02 on that DIY CO2 capture idea for our fellow Earthlings:
So far as I know, pure Hydrogen is the only practical clean fuel with the energy density required for every conceivable use from generators to cars to rockets and pure LNH3 is the only practical way to transport or store that fuel at ambient temperatures, feasible pressures, and with volumetric Hydrogen density approaching traditional liquid hydrocarbon fuels. In the transition period, we certainly can and should experiment with cleaner alternative fuels such as methane and propane. Since nobody has explained to me how slowing the rate of atmospheric CO2 increase is doing anything except exacerbating the global warming problem at a slower rate, my presumption is that we actually have to stop emitting CO2 at some point- the sooner, the better according to the science. There’s no other realistic alternative if that’s our goal. After 30+ years of concerted global effort invested into every conceivable leap-ahead battery technology, miraculous new battery technologies have yet to materialize. The dramatic cost decrease associated with Lithium-ion batteries has merely resulted in a vehicle battery that cost as much as a complete gasoline powered car, none-too-impressive in my book. As such, it’s obvious to me that Hydrogen really is that hard to beat. All arguments about the efficiency of batteries is academic in the face of current technological reality. We don’t make enough of them to reduce manufacturing costs to the point where they’re cost-competitive with combustion engines, we don’t recycle them, and they’re absurdly expensive for the paltry energy storage they provide. Assuming we do come up with a Lithium-ion replacement, it’ll be at least another 10 years before we’ve industrialized that new technology and probably another 30 years before its cost comes down to the point that the masses can afford to use it in a significant way, such as powering the vehicle they use to drive to work.
Well, where does that leave us?:
My plan is to centralize CO2 emissions sources and then collect the byproduct CO2 using purpose-built industrial scale machinery optimized to process the CO2 produced by Haber-Bosch plants into pure Carbon powder using a single-step EUV process. Those plants would be used to create the transportable / storable LNH3 fuel required to power everything else and to provide the precursor material to CNT, which is necessary to fabricate lightweight / high-strength structures for everything from I-beams to aerospace transport vehicles. The most logical place to end our near total reliance on Earth’s finite stores of hydrocarbon fuels is as near to the source as is practical using technology we already have, rather than technology we wish we had.
We don’t have anything remotely resembling like-kind replacements for Hydrogen-rich fuels or plastics, so production of gas and oil is still required. I don’t see that changing in the near future, even though we should continue to develop the technology required to synthesize fuels and plastics from atmospheric gases and water. The fundamental difference between what we’re currently doing with gas and oil and what I’m proposing is that we truly “consume” every part of those hydrocarbon molecules we extract to transform them into cleaner fuels and structural fabrication materials at the same time. That must occur at the refinery. It’s not practical to attach a CO2 collector to every tailpipe.
There are three practical ways to “do more with less”:
The first is making moving objects lighter to reduce the power required to move them. CNT fiber is some of the lightest and toughest stuff that we actually know how to mass produce. However, it requires high purity Carbon and very tightly controlled manufacturing processes to achieve mechanical properties that make it superior to plain Carbon Fiber. Unfortunately, it also requires a much cheaper source of Carbon than baking Carbon-containing compounds in very high temperature ovens or digging it out of the ground and removing the impurities. Both of those processes are extremely energy-intensive and thus very costly, ultimately impractical for supplying the quantity of Carbon required to replace the Iron and Aluminum used in today’s vehicle structures. The only practical and “already paid for” source of Carbon that I’m aware of is derived from combustion.
Simply collecting CO2 is not sufficient to produce income. After the CO2 has been collected, you need to do something useful with it. You’re not going to sell CO2 to anyone, as anyone who needs CO2 already gets it from somewhere else as a commodity product. The equipment required to separate Carbon from CO2 is not compact or cheap or simple to operate. Nobody I know makes their own home brew Carbon Fiber, either. It’s the sort of thing we need corporations, maybe even governments, to implement at a scale that would make the CNT product an affordable fabrication material. I just don’t see how individuals are going to separate the Carbon or grow the tubes in their garages, even though it’s possible to do it. The videos you see on YouTube where people are growing tiny quantities of their own CNT most likely don’t have the equipment required to guarantee quality control of their product unless they’re working for a corporation that has already invested millions in terms of education, training, and equipment. Apart from the energy required to split CO2, quality control is where most of that capital would be invested. The university labs have equipment that most amateurs couldn’t even begin to afford. Massive throughput is required to make Iron and Aluminum refining a profitable endeavor and that’s what I’m trying to replace at a significant scale.
The second is to increase the efficiency of the engines that power those moving objects. Until those batteries with order-of-magnitude improvement in energy density arrive, that would mean fuel cells. It’s certainly possible to fabricate fuel cells in small machine shops, even if the knowledge to do that is somewhat specialized. In both construction and operation, they’re much simpler than combustion engines, with very few moving parts. The catalysts and permeable membrane materials are where most of the cost comes in, but cheaper catalysts certainly would work for generators and motor vehicles. Mass production and quality control would put a serious damper on home workshop efforts. An engine factory that cranks out engines by the hundreds of thousands is the most likely candidate for mass production. Since nobody casts their own engine cases or forges their own crankshafts, either, it’s improbable that they’ll be machining their own plates, even though anyone with a CNC mill certainly could do it for the price of the mill, knowledge required to use it, and the Aluminum or Carbon for the plates. I could definitely see servicing performed by small shops or DIY’ers with a modicum of knowledge, much as they already do with combustion engines.
The third way is to stop treating things that should be durable goods as disposable products. Most people think of cars as disposable products these days, but the energy and labor that went into making them is considerable and one of the best ways to reduce CO2 emissions is to stop treating so much of the material and machining efforts as disposable artifacts of modern society. This is almost entirely down to the personal behavior of the consumer. The reason we have so many disposable products is that consumers chose to purchase those cheaper disposable products instead of more durable but more costly products. If there wasn’t a market for such products, then nobody would make them.
Do you really need a brand new car every 3 years, or is the vehicle you have something you intend to keep serviceable as long as you can?
If you knew that 2/3rds of everything we make would end up rotting or rusting away in a landfill, where it’s not serving anyone, would that change how you treat what you own and what you choose to buy?
Are you wiling to pay more for something that lasts 20 years vs 2 years and if so, how much more?
Everyone will have different answers to those questions, but when customers start voting with their wallets the manufacturers tend to pick up on that fairly quickly.
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