omenti

who are you going to call?

Drop two pieces of bread into the toaster and push the lever down.  You go about your business getting the rest of breakfast ready and then, after a few minutes, two pieces of toast pop up.  Have you ever thought about what's going on?

 

We usually think about the toaster receiving the bread and giving it back to us after a few minutes - electric heating somehow.  Someone from a few thousand years ago might wonder where the bread came from and what kind of magic transformed it into something similar but different after a few minutes.  He might wonder if the lever was some kind of prayer or incantation.  We can examine the process at a variety of levels and can find considerable depth.  We know the cord is plugged into a socket which has a path though a series of transformers and wires that usually lead to a generator that is turned by spinning a turbine with falling water or steam superheated by nuclear fission or the burning of fossil fuels.  When the switch goes on the load on the generators increases by a bit more than we're using.  The steps required advances small and large over the decades in science and technology.   For example getting the of generation and transmission of electricity to work efficiently depends on an understanding of Maxwell's equations and a fair amount of math.  

 

We don't think about these things because we trust them. There's a solid bedrock of reliable knowledge in much of our technology even though we're not one hundred percent sure of the science.  Our trust in science is nearly universal even though some of us chose to deny certain aspects.  Global warming deniers and flat earthers have no problem using the Internet - computer mediated communication built on silicon based semiconductor technology, fiber optics and much more.   Their mistrust is often based on something in their personal value system that to first order may seem orthogonal to the scientific arguments.

 

Not many people have a good handle on how science is done and how it progresses.  Many of us had to memorize the steps in "the scientific process" in elementary school, but it turns out it's messy and there's no formal process.  In college you may have come across Karl Popper's notion of falsifiability and Thomas Kuhn’s paradigm shifts. Both of these models have been shown to be wrong.  The view among many scientists and philosophers of science is science is more or less makeshift, but produces reliable knowledge and tends towards self-correction and reliable knowledge over time.

 

A few years ago a few lectures by Naomi Oreskes at Princeton gave me the basis of something I'm more comfortable with even though it's not complete. She argues reliable knowledge is based on five factors:  method, evidence,  consensus, values and humility.  I won't go into these as each is a deep subject, suffice it to say that the last three are deeply social - something many "hard" scientists tend to have a difficult time admitting.  Science is deeply collaborative and these social aspects often determine what is worked on as well as how it, and the people who did it, are perceived. 

 

Although most people trust much of science, personal and group values can get in the way of trusting certain aspects as well as certain scientists.  We've witnessed this up close with the pandemic, global warming and evolution.  I worry that many scientists have made a mistake by hiding their values (that's changing with some of us) as well as separating science and technology.  The separation of science and technology was value based and began to become dominant after WWII. Somehow science was to be the pure pursuit of nature even though it's linked to technology at the hip.  Often technologists are well versed in the science underlying their work and some venture into applied science.  Scientists, particularly experimentalists, are by necessity amateur technologists.  I've done some technology and have a bit of a feel for it, but I'm certainly not skilled - I do much better on the science side.  I'm in as much awe of great technologists as I am of great scientists. 

 

A final point.  Who should you trust to do science?  If the light in your house keep going out when you plug the toaster in, it probably makes sense to call a licensed electrician.  When a pipe in your house bursts spewing out gallons per minute, you call a licensed plumber and not an electrician or dentist. A trip to the dentist and not the Ghostbusters is in order when you hit a cherry pit in a piece of pie and a tooth falls out.  And when you're thinking of the long term - say your children's lives - listening to experts on global warming makes sense while listening to Mobil-Exxon or the Farmer's Almanac doesn't.  In each of these areas there are mostly good players and a few bad ones. You find the good ones from the consensus of their community. 

 

a thread of ev history

There's a nice vantage point in  Point Loma in San Diego with a monument to Juan Rodriguez Cabrillo.  In 1542 he made the first contact with the indigenous people of the area.  Not much happened, but sailing Northwards a few days later he noted smoke hanging over what is now Los Angeles.  Enough that he called one of the bays  Baya de los Fumos - Bay of the Smokes.

 

It's not clear what caused the smoke.  The Los Angeles region hosts three types of temperature inversions, each capable of trapping air masses close to the ground allowing smoke to build.  The region may have had one of the highest population density in North America in the 16th century, so it's possible the smoke was from thousands of fires - the region certainly held smoke in later centuries.  It's also possible there were large fires in the hillsides fanned by Santa Anna winds.

 

Before WWII Los Angeles, apart from areas around chemical plants, had fairly clear air most of the time.   That all changed after the war and by the fifties a thick brownish much often dropped visibility to a few blocks.  The brown smog was different from either smoke produced by wood fueled fires or the smogs coal burning was know for.

 

While the LA area was a natural environment for temperature inversions, it also hosted centers of intellectual curiosity.  A few years after the war Los Angeles decided to tackle the problem and created the first air pollution district in the country.  Arie Jan Haagen-Smit of Caltech managed to figure out what it was by 1950.  Sorting out how it was produced took a few more years.   He was able to show eighty percent came from  the automobile.

 

Caltech became a breading ground for ideas to deal with automotive smog.  By the mid 1960s Haagen-Smit and others were thinking about modern incarnations of electric cars. Wally Rippel was a student fascinated by the idea of electrifying transportation. His aha moment came when he showed electrifying the automotive fleet would only require a twenty percent increase in electricity generation.  (the number today is considerably less than ten percent). Wanting to move things along Rippel did what any Caltech student would do.  He challenged MIT to a race.

 

The Caltech team added over a ton of lead acid batteries to an old VW van for the Pasadena → Cambridge trip, while MIT converted a Corvair for their trip to Pasadena. MIT finished about a day and a half faster, but they broke down several times requiring towing more than once. The van, on the other hand, just motored through without incident and were declared winners.  

 

The 70s saw further development at several engineering schools. Recognizing batteries were heavy,  Caltech worked on early hybrid cars that would drive short distances on power from smaller battery packs before starting up a gasoline engine.  Along the way they develope regenerative braking to boost efficiency.  The first energy crises hammered home the idea that efficiency was important.  A Scientific American article appeared in 1973 telling the story of efficiency and declaring a person on a bicycle one of the most efficient forms of transportation in nature .. Steve Jobs later riffed on that calling personal computers bicycles for the mind.  An electric bike would be about twice as efficient as a human powered bike.  That led to work on motors and controllers. Unfortunately the American book disappeared and plans for a safe cycling infrastructure died.  Electric bikes would have to wait a few decades.

 

 

 

In the 80s Rippel was working with Paul MacCready's AeroVironment, something of a Caltech spinoff, on a specialized, almost anything goes, solar powered car for the five day World Solar Challenge race in Australia.  GM footed the bill for Sunraycer team and the car buried the competition.  GM engineering worked with them and the collaboration continued.  Learnings from the solar races went into new motor and controller designs as well as a recognition that aerodynamics were very important gave people the feeling something practical could be done.  Enthusiasm within GM's engineering community talked the company into building the EV1 - the first production modern electric car .  GM corporate didn't know what to do with it.. much has been written on how and why the project was killed after three years of production and extremely enthusiastic customers. Other than its batteries, the EV1 was more sophisticated than current electric cars.

 

Rippel and a few others from the EV1 experience founded AC Propulsion, building a demonstrator called the tzero.  More a proof of concept, it was sportscar designed to impress wealthy tech types defeating a stream of Ferraris and Porsches along the way. Martin Eberhard tried to convince them to take it to production, but the jump in scale was too much for them.  Instead he co-founded a company called Tesla well before Musk entered the scene.

 

Electric car history has many threads.  I'm familiar with this as I heard bits and pieces in school and through people I know.   The deeper story requires many more angles, but it's sticking how much can take place with just a few people.

 

I'm a believer in efficiency and infrastructure.  Moving towards safe active transport (walking, cycling and e-bikes) offers a much greater improvement over conventional electric cars.  (long story, willing to argue) 

 

A bit of early history. International Rectifier funded a solar car project in 1960.  Silicon solar cells were still very new and exotic.  IR provided solar cells to the space program, but wanted to grow a commercial market.  Doing the math they realized powering a home would be incredibly expensive, but a short range vehicle for city use might be practical earlier.  To make a statement they sent a solar panel to Charles Escoffery who converted a 1912 Baker Electric.  The world's first useable solar car.

Finally the clean air work starting at Caltech lead to catalytic convertors, reformulated gasoline and any number of environment regulation that have saved many lives.  That work was an innovation. 

 

the utility of a color-coded battery

There have been predictions of a hydrogen economy for decades.  At first glance it seems like the ideal fuel.  Its specific energy - how much energy you get from a kilogram - is three times higher than gasoline.  And the byproducts of combustion with oxygen are heat and water.   So why hasn't it happened?  It turns out you should think of hydrogen as more of a battery than a fuel.

 

Hydrogen is the most common element in the Universe and common on the surface of the Earth.  Unfortunately the kind we need, molecular hydrogen H₂ , is very rare.  The only practical way to get it is to use a lot of energy to break down more complex molecules.  Methane is the most common, but other hydrocarbons like coal are used.  The process uses more energy than burning hydrogen releases and usually produces a lot of carbon dioxide and other waste products.  

 

There are many industrial uses of hydrogen, but the fossil fuel industry has been interested in expanding to new markets like transportation and heating.  They have the knowhow - all they need to do is scale their operations.  In fact they've been lobbying governments since the 80s and billions of government money have been spent investigating a fossil fuel driven hydrogen economy.   A good fraction of the funding went into the development of practical automotive fuel cells  - more on that later.

 

In grade school you probably used a battery and two wires to make a simple electrolysis machine that broke water into hydrogen and oxygen gas.  These days the best electrolyzers are something over 70% efficient.  Sounds great but there's another problem.  The energy per unit volume (energy density) of hydrogen gas at atmospheric pressure is about 2,800 times lower than gasoline.  A gas tank for a car would be bus sized.  The trick is to compress or liquify it.   Compressed hydrogen has about one seventh the amount of energy as the same volume of gasoline.  Liquid hydrogen is closer to a third.  Larger, heavier and more expensive than gas tanks, but more practical than attaching a blimp to your car.

 

A hydrogen fuel cell uses hydrogen and oxygen to produce electricity and water. The efficiency of a fuel cell running an electric motor is higher than that of an internal combustion engine so the hydrogen tank is small enough to fit in a car.   Before you can fuel the car the hydrogen needs to be compressed or liquified, both of which take a lot of energy.   About a third of the energy produced as electricity where electrolysis takes place makes it to the tank.  From there you about half of that getting it though the fuel cells and motor to the wheels.   But with the right power source it can be carbon-free.  Unfortunately most of the hydrogen cars to date use a dirtier hydrogen.  And that brings up a marketing term:  the color of hydrogen.

 

Green hydrogen is produced by electrolysis using electricity from a zero carbon source.  Brown hydrogen is produced from methane and black hydrogen from coal (much of the industrial hydrogen in Germany and China is black) Both forms have serious production carbon emissions that, when used in a hydrogen car, emit more than a conventional car.  Blue hydrogen is an attempt to deal with brown and black carbon emission problem.  It't still produced from methane or coal, but the carbon is captured and stored.  I consider that something of a pipe dream, but Japan is interested in blue hydrogen produced in Australia.¹  

 

Hydrogen is frequently mentioned as the future for low carbon airplanes.  Liquid hydrogen would be necessary and huge tanks would be needed.  There are several designs on the drawing board that couild happen in  fifteen years using turbofans designed to burn hydrogen.  They'd still produce some pollution (NO_x) from the heat of combustion and the extra water vapor would leave thicker contrails.²

 

Recent geopolitical issues have raised the issue of using hydrogen to heat homes and businesses rather than natural gas.. after all .. there's a large and very expensive infrastructure in place already.  Countries like England are experimenting with hydrogen/natural gas mixtures. You can get away with as much as 20% hydrogen and use the same furnace burners and conventional pipe infrastructure. In the UK new furnaces will have to have a dual fuel mode - natural gas or hydrogen.   An infrastructure problem is it takes about three times as much energy to move equivalent amount of hydrogen as methane. Also current pipelines may be too brittle over time.  Hydrogen leaks much more easily than methane (which is already a problem) and hydrogen leakage is an indirect greenhouse gas.  There are a lot of potentially expensive questions to answer, so I wouldn't pencil this in as a slam dunk.  On top of it you need to produce about three times as much energy to heat a house with hydrogen as you would with just electricity.  Use a heat pump and electric heating looks even better.

 

Hydrogen could be used store power for the grid, but that gets into comparing many forms of energy storage, so not now.

 

My gut tells me hydrogen could see niche applications..  Long distance trucking if battery development plateaus  soon (I wouldn't bet on that, but I wouldn't want to be a truck manufacturer) and aviation in the long term (15 years at the earliest).  

 

But a final comment - if you have enough it will gravitationally collapse and fusion ignites - you have a star.  We happen to have one.  The trick is just one of collection.  So in that sense life on Earth and almost everything we do is part of an hydrogen economy, but the convertor is about 150 million kilometers away.

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¹ Japan is big on hydrogen and had originally envisioned scaling up nuclear power, but that pathdied with a tidal wave.)  At this point I think blue hydrogen has underpants gnome issues.

² Contrails appear to be serious global warming issues.   It's possible that leaving them at night doesn't make sense and flights may have to occur at lower altitudes - say 20,000 feet rather than over 30,000.  That would mean slower speeds which means propellers may be practical so liquid hydrogen powering fuel cells to run electric motors may make sense.

 

 

building blocks

Watching Apple's Mac Studio announcement yesterday took my mind to something Carl Sagan said in the Cosmos series.

The Mac Studio's underlying technology goes far beyond the many tens of thousands of person-hours Apple has invested.  The semiconductor industry that stands on the shoulders of Bell Laboratories back to the fundamental work of James Clerk Maxwell and before.  Apple and others are able to come up with advances that strike us as dramatic as they make an impact on our lives.  The impact of some innovations like the electric light, the telephone, the automobile, powered flight, radio, the atomic bomb and the Internet have changed how we see ourselves.   But take a look and they're all built on long chains of invention and innovation that are often forgotten.

 

This comes to mind with the horrors going on in Ukraine.  Russia has always had brilliant minds.  They've made stunning advances in physics and math, but they haven't been as successful as the West in building on that.  A good deal of their technology is derivative.  In the past 25 years this may be by design. Most of the export value comes from extraction - oil and other natural resources. These industries seem to fall under the direct control of Putin's friends.  More technical industries are still under oligarchs, but these aren't super high profit.  As long as the core players can control them, the real focus of the economy is what can be run by shear force and power rather than technology and sound business practices.  (note - this is speculation as I'm certainly not a Russian expert..  so take it with a grain of salt).  

 

High tech industry is required for the military and some consumer use.  Although that is supposed to be home-brew there is a lot of importing and rebranding. I've seen that in electronics used in physics experiments and am told is standard operating procedure.

 

So imagine you can't important and rebrand the CNC tools necessary to make jet engines.  Can you make the tools yourself. What if you can't even make precision bearings?  What if China doesn't allow electronics into the country (they probably will, but now they can be the Mafia dons)?  Sanctions can make a medium and longterm impact.  

 

You don't need to make your Apple pies from scratch - we have our universe - but few companies or countries have the capability to build objects of the modern world without technologies that exist outside.  All of these long threads few of us think about until they aren't available.  Think about all of those high value products waiting for fifty cent ICs that were designed twenty years ago...

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PS - I'd love a Mac Studio, but it's way beyond my budget. 

 

 

on nuclear winter

Talks and discussions on the impact of nuclear war - even small exchanges.  It's an important, but potentially triggering, subject. If the current situation in Ukraine is keeping you up, please skip this one for awhile.

 

The first two videos are short TED talks from the last decade. 

 

The last is an excellent discussion lead by Andy Revkin.

 

flavors of augmented reality

Augmented reality has been with us for a long time.  Glasses and contact lenses turn the eye into a two element lens to correct issues with our eye's lens.  We use sunglasses to change the intensity and/or polarization of incoming light.  Some of these are responsive to changes in the scene around us.  Some of us wear hearing aids.  A few use assistive animals like seeing eye and epilepsy dogs. 

 

Some of these applications like glasses have fixed characteristics. Others like dogs can be highly adaptable.   Apple offers good example of computationally adaptive AR with AirPods and the cameras on iPhones and iPods.  The technical press tends to describe AR as overlaying a computational display - often information from the cloud keying on local state information like who you are, what you're interested in, your location, and so on.  

 

As it happens reality is much richer than what we experience with our senses.  Visible light is only a tiny segment of the electromagnetic spectrum and soundscapes are much richer. There can be any number of useful and recreational explorations into the larger reality - science does this all the time.  Wearable AR can open up wider videos into the incredible richness of reality itself.

 

It's been interesting watching Apple's shift in how they position their watch.  At first there seemed to be an assumption that it was a fashion accessory like a normal watch with some extra complications.  After a few generations it evolved into a health and safety wearable.  Initially Apple's visual AR device will probably offer simple visual overlays that you might see on a smartphone but with time I suspect it develop a strong health component that will be a major attraction.  People with serious glaucoma could get a view of the areas their eyes are missing.  As displays get better perhaps a visual AR wearable could replace glasses entirely matching your prescription and becoming a computational tool with the tricks we see in computational photography.  "zoom to the moving target and slow motion..." or "reduce glare from the water.."    It's easy to sit down and come up with a dozen ideas that aren't games.  The list gets even richer when you start linking in other sensors. 

 

We'll see wearable AR used in many modes, but I suggest the augmentation of local reality will be very important in ways we don't yet appreciate.  There are a lot of hurdles that make me think early devices will be crippled, but after a decade this could be a very rich area indeed.

 

 

 

 

 

meshes and trees

A few weeks ago an unexpected email arrived from Germany.  A physics postdoc and had come across an ancient transition radiation detector in storage at CERN a few months before.  It seemed like it could be useful in an experiment her group was thinking about. She had a few questions and it turned out I was the best person to talk to.

 

Many people think science is done with sparkling new state-of-the-art kit.  A few pieces perhaps, but very old equipment is updated, repaired and repurposed where it might be useful.  An experiment I was part of in the early 80s required a very large magnet.  The best bet was one that had been a cyclotron at Berkeley fifty years earlier.  It worked well,  but we had to tap into institutional knowledge that had migrated out of physics entirely.  That knowledge combined with technology that hadn't been invented at the time gave us something fantastic.  

 

I have no idea how my old detector made its way from Brookhaven National Laboratories to CERN.  The documentation and lab books were packed with it, but they made assumptions that the people who built it would be involved.   That meant me.  I asked for photos of some of the lab book pages and then it came back.  I listened to her ideas, offered some suggestions and wished we had her experience back then..  Of course that experience came years later.

 

These interactions spanning several decades may not be common, but twenty year interactions of hardware, software and people.  It's all a mesh.  Old apparatus islands that have been repurposed and grafted onto new apparatus.  It's an organic process that's difficult to map out and impossible to predict.   Diagrams it would look like flocks of meshes that are grafted together with a lot of institutional knowledge.  No one has a complete picture and local expertise is critical.  A team sport spanning decades.  It isn't easy, but it works.

 

Last week I came across something by Frank Oppenheimer in the 30s:

 

 

 

It's one of the better commentaries I've seen on how science progresses.  The same is probably true for many other fields.  I suspect it's true for any infrastructure involved in messy and complex endeavors where creativity and insight come into play.  

 

I've been fascinated watching the techno-solutionist approach to cities - the so-called smart city.  These are often based on a "start with internet and build up" model.  They try to measure everything and automate control.  Sensors embedded everywhere and tree-like computational structures making decisions to smooth out - well - everything.  A fundamental problem is we don't know what is being measured and what the biases - social and technical - are.   A simple truth I've learned from my exposure to sports science is you have to know exactly what's being measured and exactly where it is useful. (duh!)   Often current measurements and/or models just don't work.  Something complex like a city is that on steroids with the tree-like information structures introducing a certain rigidity.

 

There are a few types of people who thrive in the messy environment of a city.  Impedance matchers - those who can connect and explain across disciplines, and synthesizers come to mind.  (many others too - artists for example)  They respond to intellectual and system friction and help spark creativity. They're ground zero essentials for  creativity and invention.  I have doubts that the techno-solutionist cities can be terribly creative in the long run.

a song by Malvina Reynolds comes to mind

 

people beyond the numbers

 

"Track is nothing but numbers. A good mathematician probably could be a good track coach."

 

A quote from the head coach of the University of Oregon's track and field program.   They've picked some metrics that aren't applicable to sport which force young women to endanger themselves mentally and physically.  It turns out to be a way to turn a "fitness goal" into body shaming and performance on the field can suffer.   Here's a good piece on the subject.  Unfortunately Oregon isn't alone. 

 

Just what needs to be measured and how is it analyzed and interpreted.  In this case it's an outdated belief that thin people can run faster and jump higher.  It may be true to a point, but going past that point can reduce performance and lead to Relative Energy Deficiency in Sport.   Sadly RED-S is common among female athletes - often the result of the athletes and their coaches not being aware of the last few decades of health and fitness in sports research.  They may be very good at measuring body fat percentages, but that's barking up the wrong tree.

 

People, it turns out, are complicated.  Traditionally medicine has been based on a biomedical model.  Simply speaking you measure something and react (treat medically or create a fitness goal in sports) based on the number and then repeat the steps.  For many medical conditions measurements and treatments are coarse enough that it works well enough - it's often all there is.  

 

In the past twenty years there's been a recognition that the mind is involved.The mind and body react together to what we forecast might happen in the near future.¹  Sometimes the mental component is small but it's can very large - particularly in competition.   To get a handle on the mental side athletes are often asked to keep detailed training diaries on how they feel at various times of the day .  A coach looks for changes and tries to adjust the training accordingly.   To go deeper here's been explosive growth in the use of sports psychologists in professional and D-I college sports.

 

There's also been an explosion in wearable fitness devices.  They can be great when the simple biomedical model applies.  Using them to improve fitness levels works for many people who aren't at peak performance levels.  Many paths can result in improved fitness and motivation is extremely important.  Professionals find them useful in some areas of training - checking heart rates during aerobics for example,  but don't find them terribly useful outside training.  

 

And back to the amateur.  You may have the twin goals of weight management and improved fitness.  Exercise is almost always great for health and probably worth the price of a wearable if you have motivation issues, but weight management is poorly dependent on exercise.  A device may tell you how many Calories of kilojoules you've used during a session, but sadly it's incorrect to assume that's tied to how much you eat.  Metabolism is very complex and the body and mind adjust it to match new conditions.  So you lose weight at first, but then it comes back even though you're exercising and eating the same.   There are good evolutionary reasons for this that we've abundanced our way out of.

 

Assume you have a device that can measure a few metrics that are well-understood.  How the information is used can be tricky.  We're seeing a lot of amateur mistakes with date analysis in the pandemic - and often by people who should know better.  It's common in fitness training and undoubtedly in many fields.   My friend Greg Blonder put together two pieces of information that presented together are misleading.

 

You plot the amount of ketchup on the horizontal axis, and Tastiness on the vertical.
A hamburger is very desirable with a little ketchup, ever more so slathered. Liver is highly detested, but LOTS of ketchup helps. So more ketchup is better for either meal, but worse overall. The undesirability of liver skews the results when you aggregate data.  

 

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¹ In the literature the mind-body models are sometimes called anticipatory regulation or predictive processing.  Journalist Mike Finch and sports scientists Ross Tucker and John Kiely talk about this and a few other training issues associated with elite sport in episode 26 Tucker's The Real Science of Sport podcast.  If you have any interest in sports science this is one of the best podcasts around. 

 

 

opportunity++

Now it's posh, but London's Soho district was a rather unfortunate place in the mid 19th century.  The region was experiencing dramatic growth, but it didn't connect to London's sewer system.  Residences crammed in with slaughter houses and rendering plants overloaded a primitive sewer system that was unable to serve everyone.  Cesspools ran over and untreated waste flowed directly into the Thames.  This was taking place during a worldwide pandemic. London had seen outbreaks before, but the 1854  outbreak on Broad Street changed the course of history.

 

John Snow is famous for mapping out cholera deaths in the area and noting a cluster served by a water pump on Broad Street. The pump drew water from a well that was contaminated by human and animal sewage. The Broad Street pump was removed from service, but didn't make much of a dent in the three or four thousand cholera deaths in London.  What made a difference was what he did next. - an analysis of deaths in regions served by water pumped from the Thames.  He set up a double blind experiment and showed cholera was carried by an agent in the water rather than the dominate theory that it was "bad air" (miasma).  It was the beginning of scientific epidemiology and modern public health. 

 

There's a pub named in his honor near the location of the pump that started his line of reasoning.

 

Over the last year and a half we've been  learning just how important public health is.  It seems odd to unquestionaingly spend so much on a war industry when a pandemic mixed with politics and a fear of science has prove more lethal than war.  That aside we're learning fresh air is critical with airborne spread diseases.  During an outbreak that means masks universally worn as a first and final line of defense and frequent air changes.  With the delta variant of SARS-CoV-2  it looks like you need at least fifteen air changes an hour to qualify as safe with minimal masking.  Outside of clean rooms and operating theaters that's a tall order indoors.  We can get part of the way there with in-room air cleaners, upgraded HVAC systems and opening windows when you can.  I've been spending some time doing this to learn a bit and have come to the conclusion that, although effective, it's sort of a piano wire and chewing gum approach.   Real fixes require an architectural design approach informed by science to create new spaces as well as retrofit existing ones.  Very few people do the science and much needs to be done.  New technologies probably need to be developed and there needs to be a better understanding of what can be done with what exists.. 

 

Creating clean spaces goes well beyond the current pandemic.  Clean indoor rooms can have an impact on the flu plus there are a number of chemicals that outgas that we mostly ignore.  And many of us have had to deal with PM 2.5 pollution from forest fires and combustion.    The question is how do you make this desirable enough that we learn how to make and implement better designs than we have?   How do you spark a revolution in public health that involves architecture design and retrofit on a massive scale?

 

Unfortunately successful public health measures are often seen as expensive overkill.  Perhaps carbon dioxide concentration is the answer.  Over the years studies have shown decreases in cognitive functions and alertness linked to higher  CO₂ concentrations.¹ Generally 1000 parts per million is seen as a boundary, but some studies show decreased mental ability around 800 ppm.  Many offices and schools regularly exceed 1000 when occupied.  Your car is probably several thousand in a half hour  if you aren't bringing in outside air.  How much would a school spend to upgrade the mental ability of its students?  Would a company pay extra for more alert workers who function at higher cognitive levels and get sick less often? And what about homes?  Many homes are worse than offices - maybe working from home should be rethought or at least certified.   

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¹ A fairly recent study on cognitive function associated with CO₂ and VOC exposure 

 

 

getting to clean enough

It's becoming clear that the SARS-CoV-2 virus will be around for a long time.  We're probably much closer to the beginning than the end.   Hotspots will shift and new variants arise so it makes sense to be ready to mitigate risks as much as possible.  Vaccinating the world should be a high priority along with next generation vaccines, better treatments, testing, high quality masks when the risk is high, etc. etc.  

 

Improving local air quality is low hanging fruit.  To first order that means high quality masks in hotspots along with fresh air.   Room air filtration and circulation can be a powerful tool.  As living animals we exhale carbon dioxide.  In pristine location, say a mountain top in Hawaii, you can measure the baseline concentration. Air is about 420 ppm (parts per million) carbon dioxide - a bit over 0.04%.  Enclosed spaces with people have higher concentrations.  You're breathing some of the air from other people.  If people are the only source, you can calculate the percent of the total air in the room that's exhaled:

        CO₂ concentration (ppm)        % of total air that is exhaled 

                    420                                                  0%

                    600                                                0.5%  

                    800                                                1.0%

                    1000                                              1.5%

                    2400                                               5.0%

 

With these numbers it was believed the risk is low for up to an hour if everyone was wearing a simple cloth mask and one person was infected with the alpha variant with carbon dioxide concentrations as high as 800 ppm.  The delta variant changes the threshold.   Now the one hour number is about 600 ppm with everyone wearing a surgical mask.¹  Of course the probability of an infected person being in the room is low if you're in an area where the infection rate is low.  

 

It would be good to know the concentrations where ever you go:   offices, classrooms, stores, theaters, taxis, airplanes etc.²  Consumer grade carbon dioxide meters can be purchased for $100 to $300.  If you're really interested I can make a recommendation, but I've only used a few.  We'll probably see a rapid improvement as these are going to be essential tools.  Japan is requiring them in many public places and school rooms.³  It's important to have an NDIR sensor (basically it's doing spectroscopy with an infrared laser to measure concentration  - there are many other techniques, but this is the cheapest with enough accuracy and repeatability).  These are accurate to about 50 ppm, so ignore the more exact looking reading and just round up to the next multiple of 50  - if it reads 537 just call it 550.    It takes about two minutes to get a stable reading and you'll want one that stores measurements.  The model I like talks to an iPhone app which gives you a nice chart of the day.   For businesses and schools it's a good way to check if the rooms are getting good airflow.   I saw one schoolroom that exceeded 3000 ppm when students were present. It turned out an air return duct was blocked - a thirty minute fix gave the students clean air again.

 

High carbon dioxide concentrations make people drowsy and sap cognitive abilities.  It hasn't been carefully studied, but readings over 1000 ppm can make you drowsy and perhaps a bit feeble minded.  One Army study suggests 800 ppm should be a warning level.  Half-jokingly I told a superintendent that he could justify the cost of measurement though improved test scores.  It turned out that's what sold him.  Maybe it's a way to upgrade the collective intellectual capacity of an office.  Another benefit is a possible reduction in airborne diseases like the flu.  

 

You can't always open windows and doors to get a solid draft, but HVAC systems can often have their fan settings increased and room vents adjusted. High quality filters can capture viruses along with other particulate like some from a fire.  MERV-13 is a sweet spot for price,  the ability to snare virus sized particles and not requiring more powerful fans.  And you can buy or build portable air cleaners.

 

The hot ticket for rolling your own is a very simple design known as the Corsi-Rosenthal cube.  Here's the public domain diagram we used to build 84 of them for about $5,000  (the cost shown in the drawing doesn't involve much shopping around).  We used the cardboard from the shipping boxes the fans came in.  The shroud is very important.  Square corners disturb the airflow and can drop the unit's efficiency by about a third. A normal sized classroom for 30 to 40 students probably needs two units.  Keep them away from walls, doors,  and openable windows.  The filters will probably last the school year if you turn them off when people aren't in the room.  Most of the classrooms are showing readings under 600 ppm with these and the school's HVAC system fans all on high.  The boxes make a big difference.  Commercial air cleaners with good filters probably make more sense in offices and schools if they want to go long term, but 600 cfpm MERV-13 filters are about $500 and in short supply these days.   Like carbon dioxide meters I suspect we'll see some movement on air filter and fan design. 

 

Some learnings:

Duct tape is frustrating!

Schools have mountains of duct tape.

Eighth graders are the perfect people to enlist if you want to build a lot of them.  Eighth grade girls if you want them to be semi-presentable.

_________

¹ These are rule of thumb numbers based on empirical evidence.  But it's complex with many confounding factors. 

² A closed car can be spectacularly high. I sat in my car for fifteen minutes with one other person and recorded 3800 ppm!  You can drop this by opening the windows.  Opening them diagonally makes a lot of sense for creating airflow.  Airliners have good general circulation, but a given row can be bad.  A flight is probably much safer than a half hour Uber ride if the driver has the windows up.

³ People are already taking measurements in gyms, restaurants, etc and putting them online with locations and business names. It's ad hoc and not very standardized, but there are over 100 locations in NYC the last time I checked.  It makes much more sense for a business to do their air handling homework and post numbers in their establishment as well as their website.  Hopefully at some point a respectable aggregator will step in.