New Mars Forums

If I was an astronaut, I'd be mortified that the Orion capsule has been in development for over a decade at this point, but they still don't know why the heat shield is not behaving as it should.  Given that Avcoat is a legacy technology with thoroughly proven flight heritage behind it, that strikes me as wrong on multiple levels.  Tinkering with a known working design that's done its job every single time, merely to save a buck or two, is unforgivable.  Avcoat wasn't designed to be cheap, it was designed to withstand a screaming reentry.  If you're that concerned about cost, then you'd never fly to space to begin with, let alone go to the moon.  Whoever made that decision should be flown on the first crewed mission, whether they have astronaut training or not.  Let's see how fast they make the correct design decisions when it's their rear end that gets BBQ'd.

I wonder how much time and money has been lost trying to save money while doing something that will never be cheap or easy.

SiC mesoporous membranes for sulfuric acid decomposition at high temperatures in the iodine–sulfur process

4 Materials to Consider for Heat Transfer Applications Involving Sulfuric Acid

Umax Advanced Ceramic - Silicon Carbide Cermaic Heat Exchangers

Sulfuric Acid Concentration Plant

A Laboratory-Scale Sulfuric Acid Decomposition Apparatus for Use in Hydrogen Production Cycles

Saint Gobain Performance Ceramics and Refractories - Hexoloy Silicon Carbide Ceramic Products for Shell and Tube Heat Exchangers

2006 DOE Hydrogen Program Review - Sulfur-Iodine Thermochemical Cycle

Did anybody else catch the power density of the chemical reactor core?

It's 75MW/m^3.

The AP-1000 nuclear reactor design is 109.7MW/m^3.

That means the power density of the Sulfuric acid chemical reactor pressure vessel approaches that of an advanced nuclear reactor design.

If we can't make that work, then 700Wh/L / 0.7MWh/m^3 Lithium-ion battery energy density is far too poor to even bother with.

Sulfuric acid is 1,840kg/m^3 at room temperature, so our chemical reactant stores 23,000MJ/m^3 (12.5MJ/kg * 1,840kg/m^3) or 6.389MWh of thermal power per cubic meter of reactant volume.  Even if we're only 50% efficient at turning that thermal power into electricity, that's still 4.5X better than the latest and greatest Lithium-ion batteries.  Battery manufacturers would give up almost any amount of money for a 4.5X volumetric energy density improvement.  The batteries could get even heavier but EV manufacturers wouldn't care if you could simply get rid of the ridiculously high volume occupied by all types of electrochemical batteries, in comparison to gasoline.  The volume consumed by a battery is its own form of inefficiency, due to all the packaging materials required to enclose the battery, as most of the battery pack is not active material, it's packaging materials.

36,300,000,000,000Wh / 3,194,500Wh/m^3 (50% thermal efficiency) = 11,363,281m^3

36,300,000,000,000Wh / 700,000Wh/m^3 (Lithium-ion batteries) = 51,857,143m^3

201,600,000,000kg per year / 1,840kg = 109,565,217m^3

California only represents about 7.18% of the total annual US electric energy consumption, but they need about 9.64% of the total annual Sulfuric acid supply to achieve 100% "green energy" consumption, according to them.

Total global Lithium production was 180,000t in 2023, as opposed to 201,600,000t of Sulfuric acid.

Are we going to scale that up multiple orders of magnitude to meet demand?

Obviously not.

Why, then, is everybody acting as if we are, when anyone who can count knows that is not going to happen in the next 20 years?

The process of opening a new mine is about as fast as the process of approving and building a new nuclear reactor.

Alternatively, we're going to create a miracle battery with 5X greater energy density, so that Lithium production doesn't falter and the battery can store as much energy as a reversible oxidation reaction.  We're going to invent some brand new electrochemical battery tech to supply the energy required, because otherwise there's not enough metal production to implement the solution.  We also make 100,000t of Sodium metal, annually.  I'm not so sure that's gonna scale up quickly, either, and because energy density is lower than Lithium, of course we'll need evern more metal to work with.

If the large ship will be made from steel, which to my knowledge is completely unaffected by UV light, then how about using UV-C laser equipped robots set to "kill mode" after all the humans leave the room?

Given minimal furnishings, a robot could cover every square inch of a room to keep the nasties at bay.  We could do the same thing with ventilation ducting to tamp down on mold.  A small robot crawls around in the ventilation ducts and blasts the surfaces clean with UV-C lasers.  We'd have UV-C lasers permanently mounted to evap coils so that the humidity doesn't breed mold and bacteria.

Calliban,

I read the article.  It's not telling you or I anything we don't already know.  Electricity is not some magical way to cheat basic physics.

I noticed that they referenced low and high entropy energy machines.  There's a reason I keeping calling photovoltaics, wind turbines, and electrochemical batteries "entropy machines".  They require an inordinate entropy change to take highly disordered matter, by using enormous amounts of energy input to transform them into highly ordered matter.  However superficially efficient they appear to the indoctrinated vs educated, they're factually the most highly ordered of all our machines, thus the most energy-intensive.  Anything that requires inordinate quantities of polysilicon, composites, Lithium, and Copper to function at all, is definitionally energy-intensive.  As of right now, almost none of that energy comes from other entropy machines, because entropy machines don't generate enough surplus energy to do that in an economical way.  Unless almost all of the energy to make them and power them comes from CO2-free sources, and no matter how else indoctrinated or malevolent people try to obscure basic physics, they are in fact using more input energy to create and operate them.  That is why they cost so much.  Almost all of the money sunk into them represents money paid for energy to make and operate them, not repairing or recycling them, since that is almost impossible.  Worse still, recycling them requires more energy than making a new entropy machine from scratch.

These entropy machines represent an energy treadmill.  They're a losing proposition if we zoom out far enough to stop fixating on the end result and start focusing on all the inputs required.  If you're going to predominantly use low energy density intermittent energy sources, then you need low embodied energy materials to construct machines that last a very long time, or eventually you run out of energy to sustain your way of life.  The implications are that stark and the results won't be pretty.

There's no magic or "wonderment" in this for people who don't have emotional or ideological investment into what the end result looks like.  It looks really bad from my perspective, because from an input energy and ecology standpoint, it is bad.  While I wish that wasn't the case, I can't flippantly ignore reality and hope that it changes to suit my beliefs about how it should work.  Maybe new inventions will come along to fix not-so-green energy's numerous and varied problems, but that's hoping for something that doesn't presently exist.  Hoping for change is not a valid engineering strategy for winning this energy and ecology battle.

That's why I spent so much time and effort explaining this so many different ways, whilst repeating things I thought shouldn't require so much repetition, but it looks like it's mostly fallen on deaf ears.  I want people to know why this strategy will fail before it finally does fail.  It's my hope, though perhaps a vain one at this point, if people who have more than a passing interest in science and technology truly cannot understand it, so that the same mistakes aren't repeated during the next incarnation of whatever follows.

You and I have both spent lots of time pointing out various more practical ways forward for these green energy concepts, that at least have some chance of working to the degree and at the scale required.  Perhaps some bright young person, much smarter than I'll ever be, will pick up what we're laying down, use what they know that we don't, and solve these problems in ways we never thought of.  That is my only desire.  I recognize that we have some significant and serious long-term issue with anthropogenic global warming, maybe more of one than we know, and that the problem requires real solutions that can be implemented in the hear and now, rather than some far off point in the future.  We'll only start to appreciate the unique nature and depth of the problem after we recognize the scope and scale of trying to replace hydrocarbon energy with anything else.  Our present dependence on it is starting to become a little scary.  We need realistic alternatives, but thus far there's no serious effort to pursue them.

Enough people will independently figure this out in their own way, sooner or later.  I just hope there's enough time left to pursue actual solutions after we're done mucking around with these non-solutions.

tahanson43206,

Norway's "energy", according to the graphs I posted, which I also found using Google, is 45% hydro, perhaps 5% wind turbines and photovoltaics by now, and 50% oil, gas, and coal.

Norway's "electricity", which is merely one form of "energy", is only half of their actual energy consumption.

If we're going to talk about "electricity" vs "energy", then let's use appropriate labels.

Norway is exporting their oil and gas to the rest of Europe.  Their government is then using the profits from oil and gas sales to fund their "green energy" projects.

It really doesn't matter what kind of shell games or word games we attempt to play with our "energy" consumption.  By definition, a global problem doesn't "go away" because you exported the source of the CO2 emissions elsewhere.

Norway's 2021 "Energy" Consumption by Source, according to the EIA
Coal - 3.1% / 27,996TJ
Oil - 36.1% / 327,565TJ
Natural Gas - 3.8% / 34,951TJ
Heating - 2.6% / 23,367TJ
Biofuels and Waste Burning - 6.9% / 67,729TJ
Electricity - 47.5% / 431,967TJ

446,657TJ (124,071GWh / 124,071,385,414,890Wh) - Norway's burning of something other than Hydrogen, for "energy"

3,722,178,784kg / 3,722,179t of Hydrogen required to replace coal / oil / gas, at 33,333Wh/kg

They're creating capacity to generate 40,000t of "green Hydrogen", whatever that is, per year.

Norway requires 93 more plants of the same size to replace all that coal, oil, and gas they're presently consuming to create "energy".

154,470,419,536,000Wh <- That is how many Watt-hours of "electricity" Hysata's 95%+ efficient reverse fuel cell requires to replace Norway's coal, oil, and gas consumption, which is most definitely part of their "energy" consumption.

119,990,833,299,736Wh <- That is how many Watt-hours of "electricity" Norway produced from all "energy" sources, green or otherwise.

Economy of Norway

SpaceNut,

I'm not sure what you're trying to point out here.

You can purchase a PT-6A engine right now from Pratt & Whitney if you have the money.  It's an off the shelf item by that definition.  If you think you can bolt it onto any existing plane and go flying, then you're mistaken.  The mere fact that you can lay down cash and walk out with a product means very little.  There's clearly a lot of engineering work that goes into making sure that the plane in question can use said engine, as-installed.  Merely being able to purchase a PT-6A tells me very little about the suitability of the engine for the plane it's bolted to, nor what a plane with that engine installed might be able to do.

Calliban,

They're building a commercial electric power plant in Odessa, Texas.

Once you prove that a gas turbine technology works, we have people in America, China, Europe, India, and Russia, who all know how to make the parts and implement the technology.

NREL / NETL / US DoE and various other national labs sunk a considerable chunk of money into basic development and testing of the gas turbine, supersonic CO2 compressors, and the high temperature diffusion bonded printed circuit heat exchangers, which the UK provided the expertise and hardware for.  Those heat exchangers are approximately 1/8th the size and weight of more conventional tube-based heat exchangers.

Allison, Baker Hughes, Barber-Nichols, General Electric, Saudi Aramco, Toshiba, and a bunch of other players in the energy industry invested serious money and engineering expertise (all told, over a billion dollars, so about equal to the US government's contribution) into the project at various stages, and now we get to reap the rewards of that tightly focused investment into a technology that we know, beyond any shadow of a doubt, actually works.  If it didn't work, or was thought to be a marginal improvement, or questionable value proposition, then we wouldn't have pilot plants and full scale commercial electric power generation facilities, based upon Brayton cycle sCO2 gas turbines, popping up around the US, Canada, Europe, and now China, India, and the Middle East.

sCO2 and supersonic CO2 compressors (referred to as "rampressors" or "RamGen" by Ingersoll-Rand), are the latest applications of well-established gas turbine engine technology.  In the coming decade, sCO2 and RamGen will become cornerstone technologies for reliable green energy technology, transport, and industry.  We're still in the early days of deploying this technology, but it will have profound implications, because it is significantly better than what it replaces in ways that matter.  Rather than throwing our hands up in the air or pretending that there are no major issues with electronics-based energy technologies, we should continue pursuing technologies that can actually work at the scale we need them to work at, in order to make a meaningful difference.

It looks like the Chinese are in the process of testing sCO2 gas turbines as well:

Shouhang and EDF to Test s-CO2 Cycle in Concentrated Solar Power

tahanson43206,

I don't have "wild enthusiasm" for much of anything.  I do look for things that work well, or at least to the degree required, which are critical aspects of providing the things society wants or expects.  On-demand energy is one of the things society wants and expects, so then I go looking for technologies that provide that in better ways than what we currently have or use.  I'm not sure how or why you or others think real money hasn't already been devoted to developing sCO2 turbines, but your beliefs about this are also entirely irrelevant to plainly observable objective reality.

STEP Demo pilot plant makes new breakthrough for sCO2 power generation

SwRI, GTI Energy, GE celebrate mechanical completion of $155 million supercritical CO2 pilot plant

Novel Gas Power Plant With No Air Emissions Set in Texas

All the people who need to be convinced, and those would be the people who have invested their money, have already been convinced.

The Odessa Supercritical CO2 Power Plant is coming online in 2026.

Continue your disbelief, or don't.  I really don't care.  It has no bearing on reality.  This is happening right now.  All those pictures you see of the facilities from the links I provided were built here in Texas (San Antonio, La Porte, Odessa is still under construction).  They're not internet hoaxes.  You can see overhead Google imagery of them.  No belief in what I write is required.

tahanson43206,

sCO2 technology was developed, specifically because it was more competitive than steam or existing gas turbine engine technology.  There is no such thing as a 50% efficient 10MWe conventional gas turbine, let alone a 50% efficient 250kWe conventional gas turbine.  There is most definitely no such thing as a 300MWe steam turbine the size of an office desk.

sCO2 has the backing of NREL (National Renewable Energy Laboratory), NETL (National Energy Technology Laboratory), US DoE, SWRI (SouthWest Research Institute), General Electric, Toshiba, Barber-Nichols (the people who gave us the RS-25 turbopumps, amongst other things), Ingersoll-Rand (the people who gave us supersonic inlet velocity CO2 compressors that reduce the size of coal power plant CO2 scrubbers from a house to a 20ft transport container), Allison (the people who make the transmission gearboxes for large trucks, as well as gas turbine engines), and a number of universities around the country, and in Europe.  The renewable energy people are mostly oblivious to this because they think absolutely everything is about electricity and its magical efficiency.

There is an operational commercial electric power pilot plant here in Texas, not too far from Houston.  Results from the pilot plant have been so good that they're already building a full-scale 300MWe power plant.  The technology is real, it's actively being used and developed in the real world, and it has major financial and efficiency implications for natural gas power plants, because it does scale so well, because it is so compact compared to competing options, and because it really does work.

20 years ago, we lacked the simulation technology to understand enough about how CO2 flow through the turbine differs from steam or hot effluent gases from combustion to accurately model how such an engine might produce better results than conventional gas turbine technology that existed at that time.  Today, we have that understanding from conducting the basic research required with computing tech that came along about 15 years ago.  We have worked out how to get 100,000 operating hours out of the hot components, to include the power turbine, turbine casing, piping, and the heat exchangers.

The end result is a scalable technology that produces a high level of efficiency across multiple turbine sizes.  In conventional gas turbines, they become considerably more efficient as they're scaled up in size.  This limits the number and types of applications where they make economic sense.  This is why you don't see very many aircraft gas turbine engines below about 550hp.  Smaller turbines have existed for many decades now, but even the most modern ones have fuel efficiency figures that are horrific, even at altitude.  That was the entire reason that so many decades were spent trying to develop small / light / reliable diesel engines for light aircraft.  Diesels were fairly efficient over a very wide range of throttle settings and operating altitudes.

I don't expect sCO2 engines to replace conventional gas turbines in aircraft, but they have real potential for powering ships and heavy motorized vehicles such as the M1 Abrams main battle tanks.  The fuel efficiency improvement over the 1MW output AGT-1500 that presently powers the M1 Abrams would be truly remarkable.

Ships the size of aircraft carriers could have removable engine components that would fit through standard hatches used by personnel.  You'd still need a hand crane or "cherry picker" to move it, because steel is very heavy, but the engine itself would be so tiny that a complete power turbine and its casing would fit through the same hatches that personnel go through to reach the main spaces (engine room, fire room) of a ship.  No other engine technology allows you to do that.  Conventional LM2500 marine gas turbine engines are the size of 40ft transport containers.  Steam turbines become massive non-removable integral parts of a ship's structure at the output level demanded by an aircraft carrier.  If you wreck one, then you have to cut it out of the ship while the ship is laid up in a dry dock.  Whenever reactors are involved, there's even more complexity added to the steam turbine repair or replacement job.  sCO2 makes that a parts swap job that can take place while the ship is underway.  It's hard to express what kind of technological windfall this will be for military and commercial shipping.

The same radical increase in power density applies to Wright Electric's aircraft electric motors.  2MWe / 200kg electric motors to provide ship's power, that can also be installed or carted off the ship using a cherry picker.  Wright Electric says their motors scaled between 500kWe and 4MWe.  Even if it never powers an aircraft, it has obvious applications aboard a ship, to radically reduce space claims.  This is another technological windfall.  Generators can be placed where you need them aboard ship, because all the parts involved might weigh less than a computer server rack, for example.  That means a gun mount no longer needs a bunch of electrical cables or hydraulics routed to it.  Every major combat system can have its own self-contained power supply to provide primary or backup power.  When the system is in operation, it can rapidly spin up its own power turbine to provide electricity, but ship's power doesn't need to constantly supply power through Copper cables thicker than your thumb, most of which is entirely wasted because it's not used most of the time, to ensure that power is always available when required.

As small as these things are, where you put the engines, electric generators, heat exchangers, and all other parts of the power and propulsion plant now becomes an option for ship designers.  They don't occupy huge amounts of space, don't significantly affect the weight and balance of a ship, and multiples of these units can be installed for redundancy.  For commercial shipping, that means you don't have stupid accidents from failures of ship's power causing container ships to crash into bridges, such as what happened in Baltimore, Maryland.  That means you don't need a diesel engine the size of a house.  The metal in the sCO2 turbine may be expensive relative to cast Iron, but it's not nearly as expensive as 100X more metal in a marine diesel engine, the machining requirements are reduced, and making engine components is now being done with 3D printing.  Both the total number of components and the overall complexity of them is radically reduced.  Mechanically, a sCO2 gas turbine is no more complex than an electric motor.

These sorts of changes are ones that actually matter at a macro level, because they save the most fuel.  Will we muck that up by simply building more, thus consuming more energy?  Almost certainly, but at least energy will be available as a result.  That said, sCO2 doesn't "only" help combustion engines, it helps solar thermal, nuclear thermal, and geothermal, all at the same time.

Supersonic Inlet Velocity CO2 compressors - economically capturing CO2 from coal and natural gas power plants by drastically reducing the input power to drive the turbomachinery, the waste heat generated by compression, and radically reducing the number of stages of compression from 10 to 12, down to 1 or 2.  This has applications for small gas turbine engines, because the rampressor can cram air, as well as CO2, into a very small space and use the shockwave to work with rather than against the turbine wheel.  High quality waste heat is generated that could be pumped right back into a molten salt using a heat exchanger.

Supercritical CO2 gas turbines - Provides a power output level independent (250kW to 300MW+), broad-spectrum increase in thermal efficiency with a simultaneous reduction in size and weight of the turbine components.  This replaces most gas turbine engines.

We need to figure out how to create supersonic supercritical CO2 compressors, or S3CO2 engines.  All conventional gas turbine engines use subsonic inlets, which is why you'll see 10+ compressor stages to suck air into the engine.  Imagine if we could do that with 2 stages, dump the waste heat into an auxiliary CO2 compressor that drives the main shaft, much like the turbocompounding engines that made 400mph piston engine airliners a reality after WWII, and we send a cooler / denser intake charge through to the hot section of the engine.  Dramatic power increases per unit size and weight are possible.

Oxy-Fuel combustion - reducing Carbon Monoxide, makes CO2 easier to capture because the combustion byproducts are nearly pure CO2, reduces thermal losses to heating up inert Nitrogen gas (outside of piston engine applications where that is helpful to increasing cylinder pressures), and increasing temperatures, thus providing greater thermal efficiency

10kW/kg to 20kW/kg electric motors with air cooling - making electric motor-generators compact and lightweight components of engines, rather than heavy and cumbersome devices that have to be cut out of the hull of a ship to get serviced, only moveable with large cranes and special semi-truck trailers with dozens of tires.

There is no singular technology that will enable an actual sustainable green energy transition.  Electronics and electrical devices play an important but overall minor role.  They are not central to any realistically sustainable path forward.  They've been over-hyped by people with techno fetishes which have resulted in one-dimensional thinking.  Every energy problem is a combustion engine, therefore every energy solution must be a purely electrical device of some kind.  Few of the people promoting them have any real understanding of how energy systems are presently used by society, nor why they were designed the way they were.  That is why there hasn't been any large scale transition.  That is why the wild increase in the production of photovoltaics, wind turbines, and batteries has failed to simply keep pace with the rate of increase of energy consumption.  Germany is a prime example of a large scale failure of photovoltaics, wind turbines, and electrochemical batteries to live up to their hype.  Their CO2 emissions level are exactly where they were when they started that project, and this excludes all the CO2 emissions to create all the electrical systems they've installed.  Anyone with basic math skills could predict what would and did happen, because Germany was and is a truly absurd place to put photovoltaics and wind turbines, but apparently even PhDs cannot do math when ideologically-held beliefs about technology are threatened by objective reality.

If the electrical grid we have today largely works, even though it's primarily powered by combustion of hydrocarbon fuels, then the only proper task to pursue was to replace the burning of hydrocarbon fuels while leaving the grid relatively unchanged.  Knowing that electronics or electrical devices were unable to do that without massive increases in electrical energy storage, that strategy was doomed to failure and should've been discarded as unworkable.  Instead, they doubled-down on what clearly couldn't work, and in point of fact, didn't.  Hundreds of billions of dollars did not need to be spent to keep CO2 emissions exactly where they were when the Energiewende project began.  The requisite technologies already existed to do that, most notably nuclear thermal and solar thermal power.  Both technically feasible solutions were rejected for entirely ideological rather than technical reasons.  If the same amount of money was spent on nuclear reactors as was spent on photovoltaics, wind turbines, and batteries, 100% of Germany's electrical energy could have been provided without burning any coal or gas.

This is the unavoidable problem associated with mixing ideology and technical subject matter.  The ideology only reinforces itself, even when the fundamentals of the technical solution are firmly set against the ideology.  You cannot run an industrial economy using electronic energy generating and storage devices, which is why Germany is now well into the process of rapidly de-industrializing.

Project Design Goal
I would like to achieve complete replacement of the burning of hydrocarbon fuels to generate electricity and heat.  That is my goal, because it represents the lion's share of all hydrocarbon fuel energy consumption.  The present fixation on burning hydrocarbon fuels for transport has been thoroughly unhelpful and has resulted in no practical solutions.  If we had a magic wand to wave to electrify all vehicles, that would result in an 8% to 10% reduction of the hydrocarbon fuel energy presently consumed, at most.  If the cost of doing is changing every other aspect of how energy is produced and consumed, then that's a bridge too far.

Prudent Methodology for Employment of a New Engine or Fuel
When the US military considers using a fundamentally new type of engine or fuel, they follow a logical progression of applications of the new technology.

1. Stationary power plants and portable electric generators - power-to-weight can largely be ignored, so only efficiency matters greatly
2. Ships, tanks, or other large vehicles - power-to-weight ratio is far less critical than overall efficiency
3. Smaller vehicles such as trucks and other utility vehicles - power-to-weight is more important
4. Light aircraft - power-to-weight starts to become a significant factor in the usability of the vehicle
5. Heavy aircraft - power-to-weight is of critical importance

The reason that logical progression exists, is to minimize developmental risk or maximize the probability that the engine or fuel is suitable to task.  If you can power a portable generator, then you can try running your new engine or fuel in a large vehicle such as a ship or main battle tank or armored personnel carrier.  If power-to-weight ratio is still sufficient, then maybe it's suitable for light vehicles that require lighter engines to, you know, remain light.  If the new engine successfully powers a fleet of light vehicles, then perhaps the same basic technology in a weight-optimized format could also power a light aircraft like a drone or lower performance utility / observation aircraft.  At that point, assuming development has cemented the engine's requisite reliability / durability / power-to-weight, then and only then will the engine be used to power a heavy aircraft such as an attack helicopter or long range cargo transport.

Along the way, you discover that certain engines and fuels, which may be suitable for less demanding applications, don't work so well when you attempt to apply them to applications where power-to-weight and reliability become increasingly critical to the general usability of the vehicle.  That automatically excludes solutions which have insufficient power or unmanageable weight.  That's why we gave up trying to power long range strategic bomber aircraft using onboard nuclear reactors.  Until the aircraft was scaled-up past the point where it made sense for a strategic bomber, the weight of a properly shielded reactor was unmanageable.

Materials Suitable for Thermal Energy Storage
All great in theory, kbd512, but how and why does that apply to energy storage?

To answer that question, we must ask another question:

What are the most important qualities or attributes of a bulk energy storage medium?

1. It must be affordable and abundant so that it can be deployed at truly a massive scale.  This implies, water, salt, rock, sand, and CO2, with steel and concrete storage containers.  There are no other "more abundant" materials that you can extract from the natural environment with minimal processing and ease of shipment.  Steel and concrete are the only structural materials we produce in sufficient quantity to actually matter, with all other types of metal combined being a very distant second to steel.  Steel and concrete also happen to be the lowest cost structural materials suitable for storing thermal energy.

2. An energy storage material must not experience any significant degradation over periods of time measured in decades, because it must match the design service life of a prototypical thermal power plant, which is 75 years.  Preferably, the material used would be endlessly reusable and would not degrade at all over time.  Solid rock will ultimately crack from thermal cycling, but salt and sand are generally thought of as "forever materials", at least until you achieve temperatures that would melt steel.

3. The energy storage medium must be endlessly recyclable without significant loss of material, because this ultimately ties back to the energy storage capacity of the material being used.  It cannot generate massive amounts of toxic waste for us to contend with, either, because our ability to recycle materials and contend with toxic waste is rather limited.  Most toxins are diluted with sufficient volumes of water.  They don't actually "go away" and are not "rendered harmless", they're simply dispersed to the point of being survivable by most living things.  For a simple singular metal such as Aluminum, meaning a bar of a particular Aluminum alloy, we can recycle that quite readily and easily, and it's thermodynamically very advantageous for us to do so.

If you have paper-thin strips of Aluminum metal coated with a sticky and typically toxic electrolyte substance, sealed inside a steel container, with Carbon and Copper, then our ability to efficiently recycle Aluminum transformed into an electrochemical battery cell, immediately drops off a cliff.  The batteries will come to the recycling center in all different shapes and sizes, and they're typically coated in plastic glued on top of the steel container surrounding the battery cell, so there's no simple electro-mechanical machine we can employ to cut open the battery at one end, remove the "jelly roll" of Aluminum / Copper / Carbon / electrolyte material, unravel the jelly roll, chemically remove the electrolyte, separate the anode and cathode materials, and then dump our strip of cleaned Aluminum alloy into the melting pot to be recycled.

In actual practice, we end up shredding those electrochemical batteries using an industrial shredder, and then using a lot of very toxic chemicals and high temperatures to extract the mess of different metals and other materials contained therein.  The purity of the extracted metals is insufficient to make a new battery of the same type, unless a lot more energy and processing is done to increase the purity of the extracted / recycled metals back to what is readily obtainable from virgin metals refined from ores.  That is why battery recycling is so limited, and so ineffective.  More energy and more technology is required to recycle them than is required to create them from scratch.  The same issue applies to most photovoltaics and wind turbines.  The CIGS photovoltaics are one possible exception, but they have shorter service lives, produce less power output than Silicon-based photovoltaics, and are not very durable on their own.

The Lead-acid batteries that are commonly recycled, at rates of 95%+, are easy to recycle for several reasons.  They use liquid Sulfuric acid electrolyte, not "jelly" or "paste" electrolyte, there is no "jelly roll" in a Lead-acid battery because they contain much thicker flat "waffle plates" of pure Lead, and all of them come in very similar packaging formats that tend to be quite large and easy enough for a human or machine to pick apart, which makes extracting the metal contents of a Lead-acid cell easy and advantageous to do.  Anyone who has worked on a car before has probably messed with extracting the components of a Lead-acid battery at some point, if they worked on the old style batteries that were user-maintainable.  I would use the Lead for fishing weights, and knew of other people who used them to make their own ammunition for target practice.  The problem, of course, is the relatively short service life of Lead-acid batteries, the low energy density per unit weight, therefore the extreme quantities of Lead that would be required to put enough electrical power storage onto the grid to matter.  The other obvious downside is the fact that Lead is toxic to humans, so a Sulfuric acid leak from a cracked case would cause Lead contamination of groundwater from leaking batteries by leaching some of the Lead from the electrode plates.  Gallium-Arsenide photovoltaics have the same problem of leaching Arsenic from cracked photovoltaics, and most of the chemical loss happens during the first month or two after it cracks.

4. The energy technology must not be subject to the sorts of malfunctions that all electrical and electronic devices are subjected to.  For example, you can't "hack" a tank of molten salt, because there are no network-enabled electronic control mechanisms that regulate the flow of the salt through the power plant, because no such devices are required or in any way helpful.  Electrochemical batteries, photovoltaics, and wind turbines include failure points that can shut down the entire plant, even if there is no actual problem with the input energy source.

If an energy generating or storage system is only manageable when all the control electronics function correctly, then it will ultimately malfunction and fail in a catastrophic way.  The nature of our universe is very unkind to electronics, even if hackers keep their grubby mitts off the system that keeps them alive.  I don't mean that the control system can cause a blackout, I mean that the batteries store sufficient energy that they can fry all the other electronics attached to the grid, because they can generate a multiple of the amount of energy flowing through the grid.  The grid itself might be just fine following such an event, but all the attached devices, which are largely electronic these days, probably won't be fine.  If such were not the case, then the Tesla PowerWalls we have attached to our home would not have such an elaborate multi-stage voltage regulation setup between them, the grid-tie, and the rest of the house.

The control systems that regulate power output onto the grid can and will "clamp down" on the power being regulated, but not before it does serious damage to all the grid-attached electronics.  The reason this is not a well known issue today is that there are no grid battery storage devices operating at the gigawatt scale to cause this type of issue.  Alternatively, we will require a gold-plated grid with dramatically greater control.  When you have batteries storing multiple gigawatt-hours worth of power for a major city, this problem will inevitably do serious damage, probably not to the grid itself, but to all the individual reasons for having the grid to begin with.

5. Environmental factors cannot significantly alter the ability of the energy generation or storage medium to continue operations at all.  All photovoltaics and wind turbines experience near-vertical drops and rises in power output when some event such as a cloud passing overhead or a lull in the wind occurs.  This de-facto mandates the use of very large and powerful electrochemical battery banks, else the grid crashes whenever demand exceeds supply or supply significantly overshoots demand (this scenario can be dealt with by dumping the power into the ground, but then that power is wasted).  Since this can and does happen multiple times per day, it sets hard limits on the scalability of any solution based upon photovoltaics, wind turbines, and batteries.  No present electric power grid is designed to handle gigawatt or terawatt scale power fluctuations.  The cost of upgrading the grid to handle such events is a multiple of what the grid presently costs the consumers of that energy.  The grid can handle gigawatts of power flowing through it, but you cannot add or subtract several gigawatts of power at the speed of flipping a lightswitch, else the end result is either no electric grid or no working devices attached to said grid.  This dictates that sudden onset events like a lull in the wind or cloud passing by, has virtually no impact on the output of the electric grid.

More Realistic Energy Distribution and Storage Solutions
Only thermal engines and thermal energy stores can supply power in the manner addressed by the 5 points listed above.  Of all the materials available for storing large amounts of thermal energy, only molten salts or crushed rock or sand are sufficiently chemically stable when heated to not degrade or strongly react with their storage container.

Rather than the endless attempts to overturn the basic physics of energy storage, I propose we start working with natural principles.  We only have one area of America where we can generate significant amounts of energy.  That happens to be the otherwise sparsely populated and rather barren Midwest, because it contains an expansive desert climate region wherein the Sun is almost always shining, even during the winter.  That area of the country also happens to contain staggering salt reserves.  Rather than shipping salt in from the other side of the planet, we will "mine" our own salt by scooping it off the ground from that part of our country.  If there are any impurities requiring removal, then we're going to do it there using highly concentrated solar thermal power from fresnel lenses that Terraformer has mentioned several times.  We will also use solar thermal heat to start melting metal to create the support structures and solar troughs to collect and store thermal power.  We'll start with imported or US manufactured Pig Iron, and finish with cold-rolled steel sheet and tubing.  Pig Iron requires coal, at least for now.  Over time, we will collect enough recyclable steel that burning more coal won't be required.  As-is, most American steel products derive from recycled steel.

In short, we will have a vertically-integrated factory that both produces the raw materials and resultant structures to collect and store solar thermal power.  At a national level, both power and industrial manufacturing must become one and the same.  Only light industrial activities can take place in areas that don't produce their own power.  That makes the energy producing and generating infrastructure independent, rather than co-dependent upon many other factories and nations or imported fuels.  As long as the Sun keeps shining, which I have good reason to believe is astonishingly reliable, such a system will continue to pay us back so long as we're intelligent enough to accept its importance.  Whenever a solar thermal power plant's service life concludes or it has been damaged by the environment, the scrap materials will be shipped back there for recycling into new solar thermal power devices or other products.

After the electric grid has been replaced with a sufficiently large "solar thermal engine" to power the entire country, the next logical step is synthesis of storable hydrocarbon fuels to power transport.  This will involve desalination and CO2 extraction from sea water.  The salt will be kept for additional energy storage.  The fresh water will be pumped via pipelines around the country, as tahanson43206 has suggested, to replenish local aquifers, irrigate crops, and to cover human consumption.

HVDC power lines will distribute power across the entire country, with the electrical energy being dumped into locally operated molten salt storage tanks that power their own local sCO2 gas turbines.  The end goal will be to ensure that every city or town has enough thermal power to continue generating electricity for about a week, even if the HVDC cable was suddenly cut or rendered inoperable.  The primary advantage to doing this is that the requirement for realtime load management across expansive regional electric grids can be offloaded to a more localized level.  There is no need to balance load and generation across dozens of power plants, to within a millionth of a second.  The local molten salt storage tanks are acting as difficult to over-power or under-power buffers that absorb excess power or operate without any power input over significant periods of time.  By eliminating local coal / gas / photovoltaic / wind turbine power plants, local land reverts back to more natural uses.  We'll collect all the trash generated by those failures to recycle what we can.

This electrical power distribution and buffering scheme does an end-run around centralized computerized control stations.  No computer is required because microsecond-to-microsecond control of the HVDC input is superfluous.  It's heating up a salt tank for a "mini grid" that only spans a single city or town or county.  The local power operator only monitors the temperature of their local molten salt storage tanks.  When the temperature is nominal, they pick up the phone, call the solar thermal engine operator back in the midwest, and tell them they have enough stored thermal power to last another day or week.  The solar thermal engine operator throws a switch to turn off the supply to Township A.  That process is then repeated for City B, and so on.

The local footprint of the power generating infrastructure is limited to their HVDC interconnect, molten salt tank farm, sCO2 power turbine, and electric generator.  If we're worried about local storage capacity, then we add more salt using the pile of salt accumulating at the solar engine farm in the Midwest due to water desalination used to make hydrocarbon fuels and fresh water.  Local natural gas lines will supply backup thermal energy, as required, to directly power the sCO2 turbines if something untoward happens to the HVDC interconnect.  Other parts of the country may have some of their own local solar thermal power generating infrastructure deployed where it makes sense, but the idea here is to provide highly reliable energy at the lowest possible cost, minimize pollution through drastic simplification of the power generation / distribution / storage infrastructure, and minimize land degradation associated with clear-cutting and paving over of local fields to make way for photovoltaics and wind turbines.

There's more to add to the detail level of the plan, but that's for later posts.