Another Idea for Carbon Capture

I’m not a giant fan of Carbon capture technology.  This is basically “clean coal” to the max, and clean coal is a scam. Using complicated and expensive technology to undo some (but not all) of the mess made by other complicated and expensive technology will not solve the planet’s problems.

Still, there are some interesting possibilities for, say, creating hydrocarbon fuels out of non-fossil materials.  Done right, you might get the advantages of conventional fuels, without increasing the amount of Carbon in the atmosphere. 

Case in point, this fall MIT researchers report a process that efficiently converts CO2 into formate which can be used to rune fuel cells [2]. 

I had to look up “formate”, which is several forms of HCO2.  The material can be stored as crystals, which when dissolved in water work great in fuel cells. 

The technology involves chemical reactions that convert CO2 into liquid potassium or sodium bicarbonate solutions.  These solutions are pushed through an electrolyzer which makes liquid foraite.  (I gather that liquid to liquid conversion is very efficient.) The liquid formate can be used or dried to store for later use.

The overall idea is to suck CO2 from the air or other places you don’t want it, to make fuel that generates electricity.  Part of the idea is to use solar or other clean power to run this process, accumulating foraite for later use, e.g., at night and in the winter.  The drying step uses evaporation, too, i.e., solar power.

Formate can be a very efficient fuel, so the whole cycle generates a lot of electricity per gram.  The process should be competitive with conventional batteries.  Since it pulls in CO2 from the air, there is no increase in Carbon.

I don’t fully grok the chemistry here.  I’m also a bit hazy on where the CO2 comes from, and where it goes when power is generated.  These details could make a lot of difference about the overall impact of the process.

But, overall, this sounds like an interesting technology.  As Prachi Patel notes, these solid crystals are way easier to handle and store than Hydrogen gas, and the efficiency is way better than a lot of Hydrogen-to-fuel processes under development [1].

So, yeah.  Definitely worth looking into.

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1. Prachi Patel, MIT Turns Captured Carbon Into Fuel–Efficiently, in IEEE Spectrum – Energy, November 7, 2023. https://spectrum.ieee.org/carbon-capture-2666142039
2. Zhen Zhang, Dawei Xi, Zhichu Ren, and Ju Li, A carbon-efficient bicarbonate electrolyzer. Cell Reports Physical Science,   November 15 2023. https://doi.org/10.1016/j.xcrp.2023.101662

PS. Wouldn’t “bicarbonate electrolyzer” be a great name for a band?

Direct Lithium Extraction Is Coming

Lithium is the flavor of the month this year.  Electric vehicles and lots of other stuff needs batteries, and Lithium ion batteries are a leading technology.

Battery tech is all about capacity and weight, of course, and Lithium batteries are winning the game right now (despite well know safety risks).  Everyone needs more and more Lithium.

And, as we have all learned, Lithium is a pretty exotic product.  It comes from relatively few places, and it is “mined” through nasty extraction and separation processes.  And it’s damn expensive, too.

Even a dumb old socialist like me recognizes this as an opportunity for innovation.  Come up with a better and cheaper way to get Lithium, and, ka-ching, you win!

So I’m not surprised to read this fall  about a variety of better ways to get Lithium [1].

Conventional extraction pulls out underground brine, and leaves it to evaporate in ponds.  Lithium is extracted from the salts, and the rest is discarded as waste.  This is incredibly damaging to the area, and is not a sustainable process.

The newer methods are “Direct Lithium Extraction”, DLE.  The idea is to extract the brine, pull out only the Lithium, and then pump the brine back underground.  When this works, it gets more Lithium sooner, and does a lot less damage to the land and water.

The key, of course is in getting the Lithium out.  Several technologies are being developed to do this.

Interestingly, the new technologies may enable the extraction of Lithium from the traces typically found in oil and gas drilling water.  This would be a huge new source of Lithium, and one that is available closer to home. 

It isn’t clear exactly what technologies will be the best for this process, but it seems very clear that there will be a revolution in Lithium extraction.  It will be cleaner, faster, and there will be a lot more sources.

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1. Prachi Patel, Could Direct Lithium Extraction Be a Game-Changer? , in IEEE Spectrum – Energy, October 31, 2023. https://spectrum.ieee.org/direct-lithium

Carbon Negative Concrete?

And speaking of Carbon neutral building materials….

I know that cement is a messy energy sink, but I hadn’t realized that it accounts for about 3 times the Carbon emissions as aviation (which “gets plenty of flak for it”, as Prachi Patel says [2]).  This explains why there is increasing attention to new ways to do concrete (and, of course, things to replace it, such as fungi).

Concrete is actually pretty complicated, which is good and bad.  The good thing is that there are a lot of targets for improvements.  The bad thing is that you may need to fix a lot of things to have much impact.

This spring researchers at Washington State report progress on replacing some of the emission-generating materials with Carbon absorbing materials [1].  When this works, the concrete is not only low emissions but actually locks up Carbon “forever”.

The WSU technique substitutes biochar for some of the cement in the concrete.  Creating cement is one of the biggest source of Carbon emission, so adding waste materials (captured Carbon) offsets and reduces emissions. 

The problem is, biochar itself isn’t particularly good cement, and the resulting concrete isn’t strong enough.

The new process pretreats the biochar with wastewater laced with calcium.  This causes the biochar to react with CO2 in the air, forming CaCO2. (Let’s turn biochar into limestone…. : – ) )  Adding this to the cement makes nice, pretty strong concrete.  Concrete which has absorbed more CO2 than it emitted.

Neat.

There is plenty of work to do.  This has to work economically at very large scale.  The novel concrete has to really work outdoors for a long time.  The concrete has to work with steel reinforcement with excess corrosion.  And so on.  And, by the way, this will need reliable sources of biochar and wastewater.

So, we’ll see.

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1. Zhipeng Li and Xianming Shi, Towards sustainable industrial application of carbon-negative concrete: Synergistic carbon-capture by concrete washout water and biochar. Materials Letters, 342:134368, 2023/07/01/ 2023. https://www.sciencedirect.com/science/article/pii/S0167577X23005530
2. Prachi Patel, Concrete Goes Carbon-Negative, in IEEE Spectrum – Energy, May 8, 2023. https://spectrum.ieee.org/concrete

More Thin Solar Technology

We’ve made a lot of progress deploying solar generation world wide.

But lets face it.  Today’s home and commercial solar panels are old technology.  They are successful in part because we’ve had decades to optimize them, pushing cost down and efficiency up.

But they are fragile, and they are heavy.  This is clearly a “first generation” technology:  it works pretty well, but we will look back on it and laugh.  Made of glass? Big (and heavy) as a storm window? 

These days, there is a lot of development in new technologies, and most of them are aiming to be thinner and lighter.

This winter researchers at MIT report yet another variation, a very thin, flexible printed photovoltaic collector [2].  This technology combines various electronics and  organic photovoltaic material printed on a cloth backing.  The result is thin and flexible, and generates a lot of electricity per kilogram (about 18 times conventional PV by weight).  (It’s about 1/10 the power per area.)

The developers envision a “solar carpet” that can be installed by unrolling it on a roof [1].  The light weight means that many more structures could be solarized, including light roofs, tents, and boat sails.

So that’s cool.

The demo is promising, and the techniques are manufacturable at scale.  It will be necessary to make it rugged enough to survive in the real world.  This should be doable, but there is a lot of work to do before we have a carpet that works on the roof, or that you can, you know, walk on.

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1. Prachi Patel, Paper-Thin Solar Makes Any Surface Photovoltaic, in IEEE Spectrum – Energy, December 21, 2022. https://spectrum.ieee.org/thin-film-solar-panels
2. Mayuran Saravanapavanantham, Jeremiah Mwaura, and Vladimir Bulović, Printed Organic Photovoltaic Modules on Transferable Ultra-thin Substrates as Additive Power Sources. Small Methods, n/a (n/a):2200940, 2022/12/09 2022. https://doi.org/10.1002/smtd.202200940

Yet More Radiative Cooling

OK, a headline about “Zero-Energy Tech” catches the eye, especially from IEEE Spectrum which is hardly peddling BS [1].  And, indeed, this is about “zero external energy”—passive heating and cooling.

The technology in question is interesting because it does both passive heating (switching on solar absorbtion) and cooling (blocking solar and emitting IR).  There are technologies that do this (e.g., this or this), but this one does both, and switches modes in response to conditions.  I.e., when it is cold, it turns on the heat, and vice versa [2].

Cool. (And warm!)

The Nankai University researchers were inspired by two kinds of biological systems, leaves that furl and unfurl in response to conditions, and animals with seasonal pelts that are light and dark depending on conditions.  The technology doesn’t seem to have much to do with how the natural systems actually work, so lets call in ‘bio-inspired’.

I think this is probably targeted for structures.  The outside of your house furls up and turns gray in winter, generating gentle warmth inside.  In the summer, the panels unfurl and radiate heat out to space, cooling the interior.  This might not be all the heating an cooling needed, but it would be a zero input boost.

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1. Prachi Patel, Zero-Energy Tech Heats When Cold and Cools When Hot, in IEEE Spectrum – Energy, September 29, 2022. https://spectrum.ieee.org/passive-radiative-cooling-device
2. Quan Zhang, Yufeng Wang, Yiwen Lv, Shixiong Yu, and Rujun Ma, Bioinspired zero-energy thermal-management device based on visible and infrared thermochromism for all-season energy saving. Proceedings of the National Academy of Sciences, 119 (38):e2207353119, 2022/09/20 2022. https://doi.org/10.1073/pnas.2207353119

Hydrogen Fuel from the Air!

So, yeah, let’s use solar energy to generate Hydrogen from water.

But, wait.  Many places don’t have water to spare.  Burning drinking water for fuel may not be an ideal solution, e.g., in a desert.  Plenty of sun, no water.

This summer, researchers in Australia report a system that harvests water from the air to generate Hydrogen [1] . They use a sponge filled with hygroscopic solution, i.e., a chemical that absorbs water from the air.  Current from a photovoltaic cell or wind turbine drives a reaction to split the water and collect Hydrogen which can be used as fuel.  It’s totally passive, relying on ambient air flow.

Cool!

This technique works even if the air is dry—some chemicals work at 4% humidity.

The researchers calculate that the technique generates 745 L of hydrogen per square meter a day, “enough to heat a home” [2].

Even cooler!

Everything depends on finding the best hygroscopic chemicals, something that is cheap, safe, and reliable.   I’ll note that this might be combined with other absorbing technologies, to harvest drinking water or achieve passive cooling.

And, of course, this might be built into structures or vehicles.  It would be neat for the roof of a house or car (or dirigible!) just suck water out of the air to generate fuel! (And remember, human occupants are emitting humidity all the time!)

I want it!

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1. Jining Guo, Yuecheng Zhang, Ali Zavabeti, Kaifei Chen, Yalou Guo, Guoping Hu, Xiaolei Fan, and Gang Kevin Li, Hydrogen production from the air. Nature Communications, 13 (1):5046, 2022/09/06 2022. https://doi.org/10.1038/s41467-022-32652-y
2. Prachi Patel, Engineers Make Green Hydrogen From Air, in IEEE Spectrum – Energy, September 12, 2022. https://spectrum.ieee.org/engineers-make-green-hydrogen-from-air

Artificial Leaf Technology Advancing

Beyond photovoltaics, solar driven hydrogen extraction has been coming on fast.  (E.g., this or this.)  the idea is simple: input sun, air, and water; output hydrogen or other useful chemicals.

This concept is sometimes called ‘artificial photosynthesis”, though that’s a bit misleading because the processes are different.  And, by extension, there are a number of light and thin devices that are tagged “artificial leaves”.

The attraction is obvious, especially for marine applications.  “Leaves” float on water in the sunlight, and out comes H2 that can be used as fuel.  Problem solved!

This summer, researchers at Cambridge University report on a new, light weight artificial leaf that generates hydrogen or syngas [1].  The basic principle has been under development for more than a decad, but the new research addresses the useability [2].  The goal is to match the size and weight of a natural leaf, with similar or better productivity.

The details are out of my specialty area, but if I understand correctly, the units can produce a couple of grams of H2 per hour per gram of device.  So, covering a swimming pool sized area of water might produce a kilogram or two of hydrogen each day (I think).  This could be enough to fuel a boat or vehicle for a day. 

Which would be cool.

This technology depends on the catalyst used, so productivity could potentially improve, possibly a lot.

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1. Virgil Andrei, Geani M. Ucoski, Chanon Pornrungroj, Chawit Uswachoke, Qian Wang, Demetra S. Achilleos, Hatice Kasap, Katarzyna P. Sokol, Robert A. Jagt, Haijiao Lu, Takashi Lawson, Andreas Wagner, Sebastian D. Pike, Dominic S. Wright, Robert L. Z. Hoye, Judith L. MacManus-Driscoll, Hannah J. Joyce, Richard H. Friend, and Erwin Reisner, Floating perovskite-BiVO4 devices for scalable solar fuel production. Nature, 608 (7923):518-522, 2022/08/01 2022. https://doi.org/10.1038/s41586-022-04978-6
2. Prachi Patel, Floating Artificial Leaf Turns CO2 Into Fuel, in IEEE Spectrum – Energy, August 25, 2022. https://spectrum.ieee.org/artificial-leaf-hydrogen-syngas

Better Air Conditioners Coming Soon

One of the reasons I was excited by 3D printing from the very beginning was because I foresaw that software controlled fabrication would be a perfect match for software optimization, including various kinds of AI. 

Once the design is represented in software, the next logical step is to sic machine learning on the case, to not only optimize design, but to generate totally new designs that puny Carbon-based units would never have conceived.

This is the mountain we have to climb, and hundreds of puny monkeys are swarming up that slope!   Buildings!  Launch pads on the Moon!  How about highly optimized rocket motors?

One of the most promising technologies is super optimized heat exchangers (as well as the closely related technology of catalytic reactors).  This has become serious demo-fodder for developers, not least because heat exchangers are beautiful as well as useful [1]. 

3D printed heat sinks designed with nTopology for use in electronics (Source: nTopology) (From [1])

Heat exchangers have been around for a long time and live mainly in the guts of our infrastructure.  But there is one application that is very much “customer facing”:  air conditioning.

And air conditioner is, at heart, just a heat exchanger, designed to push heat from where you don’t want it to somewhere you don’t care about.  And, as Prachi Patel notes, AC technology is basically unchanged for many decades.

This summer, Patel reports on developments using AI, bio-inspired designs, and 3D printed metal fabrication. [2]   Additive manufacturing can achieve complex designs not possible with other fabrication techniques, and AI can propose and evaluate many designs very rapidly. Since AI has achieved alien, super humanly weird solutions in many domains, we can expect that there could well be a number of really efficient AC designs.

Heat exchangers are the big energy suck in an AC, so a better design will really matter.  Ten times better?  [2] My guess is that may be possible, though maybe not entirely from redesigning the heat exchange.

One big question is how to manufacture the new designs at scale and low cost.  Can 3D printed metal fabrication mass produce components cheap enough to match conventional fabrication?  I’m no expert, but my guess is that it can, and if so, that will be really cool.

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1. Steven Goguelin, Better Heat Exchangers with Additive Manufacturing, in All3DP, August 18, 2021. https://all3dp.com/1/better-heat-exchangers-with-additive-manufacturing/
2. Prachi Patel, AI Could Make Air Conditioners 10x Better, in IEEE Spectrum – Artificial Intelligence, August 18, 2022. https://spectrum.ieee.org/ai-3d-printing-better-ac

More Ideas for Gravity Storage

If there is anything more basic than sunlight, it has to be gravity.  I mean, the sun itself is powered by gravity.  So yeah. 

These days there are quite a few ideas for storing power using gravity.

The basic idea is to use “excess” electricity, e.g., the sunlight at mid day, to move things uphill.  Then, when power is needed later, e.g., at night, the things are released to “fall” downhill, generating electricity.  Ideally, you can get almost all the input energy back out again. Thus, the energy is stored in the form of the potential energy of “up”.

This principle can be realized with water, with blocks, or, heck, with dirt.  One key technology is the duality of electric motors, which can reversed to generate electricity.  A simple example is an elevator that lifts its load, and then regenerates electricity from braking as it lowers the load.  Basically, the elevator is storing part of the energy used to lift, and releasing it on the return trip.

This spring researchers at the International Institute for Applied Systems Analysis outside of Vienna describe some new concepts for gravity storage based on regenerative braking [3].

One idea is to use the elevators in high rise buildings as an energy store [1].  So, during low use times the elevators can lift mass—say buckets of sand—to the roof.  Later on, the mass can be lowered down again, generating electricity from the braking system.

This idea has the advantage that it is a retrofit on existing infrastructure.  I’ll note that buckets of sand on the roof are certainly more fireproof than a lot of battery technology, so that’s another plus.  The economic feasibility depend a lots on the cost of alternative storage such as batteries.

Now, retrofitting a building to safely accommodate significant additional mass on the roof may or may not be cheap and easy.  There may also be issues with noise and vibration in residential buildings.  Running the elevators all night might not be popular if they disturb the tenants.

A second idea in this same vein is to use electric trucks to haul heavy loads—e.g., sand—up a mountain [2]. The energy is release by coasting down the road with regenerative brakes on.   

This also builds on existing infrastructure.  The economics depend on the coast of trucks, which is falling, so that is a good point. 

This will only work in the right geography, and the perfect spot would be somewhere with a usable road already built, but not inhabited (e.g., a disused section of a mine or quarry pit).  Building new roads in pristine terrain is neither cheap nor desirable.  In addition to aesthetic considerations (roads, dust, big piles of sand), there may be safety issues.  This would not be a great thing to do on a busy, multi-use road, or where there is a lot of local and pedestrian traffic.

Altogether, these concepts seem pretty marginal to me. They are on the edge of economic feasibility and have potential side effects. interesting, but not likely to be widely deployed.

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1. Julian David Hunt, Andreas Nascimento, Behnam Zakeri, Jakub Jurasz, Paweł B. Dąbek, Paulo Sergio Franco Barbosa, Roberto Brandão, Nivalde José de Castro, Walter Leal Filho, and Keywan Riahi, Lift Energy Storage Technology: A solution for decentralized urban energy storage. Energy, 254:124102, 2022/09/01/ 2022. https://www.sciencedirect.com/science/article/pii/S0360544222010052
2. Julian Hunt, Jakub Jurasz, Behnam Zakeri, Andreas Nascimento, Paweł Dąbek, Roberto Brandao, Nivalde Castro, Paulo Schneider, Walter Filho, and Keywan Riahi, Electric Truck Gravity Energy Storage, a solution for long-term energy storage. SSRN Electronic Journal, 1  04/06 2022. http://dx.doi.org/10.2139/ssrn.4076988
3. Prachi Patel, Skyscrapers—A Gravity Energy Storage Boon, in IEEE Spectrum – Energy, June 16, 2022. https://spectrum.ieee.org/gravity-energy-storage-elevators-skyscrapers

Better Solar Cells With Thermal Generation

One thing about solar energy generation is that it only works while the sun is out.  PV panels produce no power at night. To get energy all the time,  solar power systems need to combine with storage and other sources.

Researchers at Stanford have been working on “anti solar” power, techniques for generating electricity from solar panels at night.  During the day, PV systems get hot in the sun, and at night they radiate heat into the cooler air.  Harnessing this heat can generate electricity.

How much electricity?  This spring the researchers report a demonstration that generates 50mW/m² [1].

OK, that’s not much, compared to hundreds of Watts per square meter from sunlight.  But even a little may be valuable [2].

This technology has a way to go.  For one thing, it will work a lot better when designed in from the start.  Current PV panels aren’t designed to maximize radiative cooling (they “waste” waste heat), so this can optimized.  And, of course, the whole idea depends on thermal connections which need to be very tight. Do we want to treat PV panels as thermal mass?

The thermal generating materials are generally expensive, so there needs to be serious attention to cost.  This technology is essentially competing with batteries or other storage which are developing rapidly, so the economics are surely a rapidly moving target. We’ll have to see.

Even if thermal generation is only a few percent of solar generation, I like the elegance.  I mean, the whole theme of solar power is capturing the sun’s energy.  It’s a shame to throw away this “excess heat”.  I want to catch as much as possible.

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1. Sid Assawaworrarit, Zunaid Omair, and Shanhui Fan, Nighttime electric power generation at a density of 50 mW/m2 via radiative cooling of a photovoltaic cell. Applied Physics Letters, 120 (14):143901, 2022/04/04 2022. https://doi.org/10.1063/5.0085205
2. Prachi Patel, These Solar Cells Produce Electricity at Night, in IEEE Spectrum – Energy, April 11, 2022. https://spectrum.ieee.org/solar-cell