Newfie joke (Newfie’s are Canadians from Newfinland)

Here’s a Newfie joke; it was originally another joke, but I tweaked it because I was in Frankenmuth today watching folks snow sculpt and ice-fish. As for Newfinland, it’s basically the Appalachia of Canada. The folks there aren’t considered to be particularly bright. Anyway.

So this Newfie decides it’s time he took up ice fishing. It’s winter and all his other Newfie friends ice fish. So he gets a setup with an ice drill, a few short fishing poles, a plastic pail to sit on, and a little tent, and he goes to set it up on the ice early one morning.

He finds a nice, empty spot, but as soon as he’s set up the pail and tent but he hears a voice from somewhere around him, “Go home, there are no fish under the ice.” He looks all around but he can’t see anyone. Who said that? Was that comment for him? He goes back to start drilling, and he hears the voice again. “Go home; there are no fish under the ice.” Well, he still can’t see anyone, but figures that maybe he should go to a different spot. He picks up his stuff, moves about 50 feet away and starts to set up again, when he hears the voice again, just as loud. “Go home, there are no fish under the ice.” “Who are you?” yells the Newfie to no-one in particular, “God?” “I’m the rink manager. There are no fish under the ice.”

Helium leak detector repaired and refurbished in Frankenmuth

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To those who know Frankenmuth, MI, it is generally as “Little Bavaria,” the German-themed vacation town of quaint houses and shops; of cheese, wurst, beer, Christmas ornaments, and Oom Pa Pa bands. I know it in a slightly different way as the only town to get your helium leak detector repaired. There are at least three shops in Frankenmuth that repair helium leak detectors (or make new specialty versions), and this is the source of the reference leaks that most qualified shops use. So I was here yesterday and today, both for the World-class snow sculpture contest, and to get my helium leak detector looked at. It was acting funny; it turns out there was a leak in the leak detector plus a bad potentiometer on a switchover circuit. The leak is already fixed, and I should have it back in my shop next week (Wednesday).

Snow-sculpting in Frankenmuth 2013; I was there to have my helium leak detector fixed.

Snow-sculpting in Frankenmuth 2013; I was there to have my helium leak detector fixed.

veeco He-leak detector at REB Research.

Purifying the Hydrogen from Browns gas, HHO, etc.

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Perhaps the simplest way to make hydrogen is to stick two electrodes into water and to apply electricity. The gas that is produced is mostly hydrogen, and is sometimes suitable for welding or for addition to an automobile engine to increase the mileage. Depending on the electrodes and whether salt is added to the water, the gas that is produced can be Browns gas, HHO,  town gas, or some relative of the three. We are sometimes asked if we can purify the product of this electrolysis, and my answer is typically: “maybe,” or “it depends.”

If the electrode was made of stainless steel and the water contained only KOH or baking soda, the gas that results will be mostly hydrogen and you will be able to purify it somewhat with a polymer membrane if you wish. The gas isn’t very explosive generally, since most of the oxygen that results from the electrolysis will go into rusting out the electrodes. The reaction is thus, H2O + Fe –> H2 + FeO. To see if this is what you’ve got, you can use determine the ratio of gas production with a simple version of the Hoffman apparatus made from (for example) two overturned glass jars, or by separating the electrodes with a paper towel. You can also determine the H2 to O2 ratio (if you know a bit more physics) from a measure of the amperage and the rate of gas production. The hydrogen you form with steel plates will always contain some oxygen though, as well as some nitrogen and water vapor. While a polymer membrane will remove most of the oxygen and nitrogen in this gas, it won’t remove all, and it will not generally remove any of the water. With this gas, I suspect that you would be better off just using it as it is. This is particularly so if the fraction of oxygen is more than a few percent: hydrogen with more oxygen than this becomes quite explosive.

Since this gas will contain water, you probably don’t want to store it, and you probably don’t want to purify it over a metal, either, There are two reasons for this: the water can condense out during storage, and will tend to rust whatever metal it contacts (it’s often alkaline). What’s more, the small amount of oxygen in the hydrogen is likely to react over a hydrogen storage metal to form water and heat. This may give rise to the explosion you were trying to avoid. This is clearly the quick a dirty approach to making hydrogen.

Another version of electrolysis gas, one that’s even quicker and dirtier than the above involves the use of table salt instead of KOH or baking soda. The hydrogen that results will contain chlorine as an impurity, and will be quite toxic, but it will be somewhat less explosive.The hydrogen will smell like bleach and the water you use will turn slightly greenish and quite alkaline. Both the liquid and gas are definitely bad news unless your aim was to make chlorine and alkali; this is called the chlor-alkali process for a reason. On a personal note, as a 12 year old I tried this and was confused about why I got equal volumes of gas on the cathode and anode. The reason was that I was making Cl2, and not O2: the chemistry is 2 H2O + 2 NaCl –> H2 + Cl2 + 2 NaOH. I then I used the bromide version reaction to make a nice sample of bromine liquid. That is, I used KBr instead of table salt. Bromine is brown, oily, and only sparingly soluble in water.

Another version of this electrolysis process involves the use of graphite electrodes. If you are lucky, this will give you a mix of CO and hydrogen and not H2 and O2. This mix is a called “town gas.” It’s a very good welding gas since it is not explosive. It is, however, quite toxic. If you begin to get a headache using this gas stop immediately: you’re experiencing CO poisoning. The reaction here is H2O + C –> H2 + CO. CO headaches just get worse and worse until you die. If you are not lucky here you can get HHO instead of town gas, and this is quite explosive: H2O –> H2 + 1/2 O2. The volume ratio will be a key clue as to which you are making; another clue is to put a small volume in a paper bag and light it. If the bag explodes with a terrific bang, you’ve made the wrong gas. Stop!

With all of these gases I would recommend that you add a polymer of paper membrane in the water between the electrodes. Filter paper will work fine for this as will ceramic paper; the classic membrane for this was asbestos. If you keep the two product gas streams separate as soon as they are formed, you’ll avoid most of your explosion-safety issues. Few people take this advice, I’ve found; they think there must be some simpler way. Trust me: this is the classic, safe way to make electrolysis hydrogen.

A balloon filled with pure hydrogen will not ignite. To show you, here is a 2.5 min long video where I poke a lit cigar into a mylar balloon filled with hydrogen from my membrane reactor generators. Note that this hydrogen does not even burn in the balloon because it is oxygen free. As a safety check try this with your hydrogen, but only on a much-smaller scale. Pure hydrogen will not go boom, impure hydrogen will. My advice: keep safe and healthy. You’ll feel better that way, and your heirs will be less inclined to sue me.

In case you are wondering how electrolysis hydrogen can add to the gas mileage, the simple answer is that it increases the combustion speed and the water vapor decreases the parasitic loss due to vacuum. I’ve got some more information on this here. I hope this advice helps with your car project or any other electrolysis option. In my opinion, one should use a membrane in the water to separate the components at formation in all but the smallest experiments and with the smallest amperage sources. Even these should be done only in a well-ventilated room or on a car that is parked outside of the house. Many of the great chemists of the 1800s died doing experiments like these; learn from their mistakes and stay among the living.

What causes the swirl of tornadoes and hurricanes

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Some weeks ago, I presented an explanation of why tornadoes and hurricanes pick up stuff based on an essay by A. Einstein that explained the phenomenon in terms of swirling fluids and Coriolis flows. I put in my own description that I thought was clearer since it avoided the word “Coriolis”, and attached a video so you could see how it all worked — or rather that is was as simple as all that. (Science teachers: I’ve found kids love it when I do this, and similar experiments with centrifugal force in the class-room as part of a weather demonstration).

I’d like to now answer a related question that I sometimes get: where does the swirl come from? hurricanes that answer follows, though I think you’ll find my it is worded differently from that in Wikipedia and kids’ science books since (as before) I don’t use the word Coriolis, nor any other concept beyond conservation of angular momentum plus that air flows from high pressure to low.

In Wikipedia and all the other web-sits I visited, it was claimed that the swirl came from “Coriolis force.” While this isn’t quite wrong, I find this explanation incomprehensible and useless. Virtually no-one has a good feel for Coriolis force as such, and those who do recognize that it doesn’t exist independently like gravity. So here is my explanation based on low and high pressure and on conservation of angular momentum.  I hope it will be clearer.

All hurricanes are associated with low pressure zones. This is not a coincidence as I understand it, but a cause-and-effect relationship. The low pressure center is what causes the hurricane to form and grow. It may also cause tornadoes but the relationship seems less clear. In the northern hemisphere, the lowest low pressure zones are found to form over the mid Atlantic or Pacific in the fall because the water there is warm and that makes the air wet and hot. Static air pressure is merely the weight of the air over a certain space, and as hot air has more volume and less density, it weighs less. Less weight = less pressure, all else being equal. Adding water (humidity) to air also reduces the air pressure as the density of water vapor is less than that of dry air in proportion to their molecular weights. The average molecular weight of dry air is 29 and the molecular weight of water is 18. As a result, every 9% increase in water content decreases the air pressure by 1% (7.6 mm or 0.3″ of mercury).

Air tends to flow from high pressure zones to low pressure zones. In the northern hemisphere, some of the highest high pressure zones form over northern Canada and Russia in the winter. High pressure zones form there by the late fall because these regions are cold and dry. Cold air is less voluminous than hot, and as a result additional hot air flows into these zones at high altitude. At sea level the air flows out from the high pressure zones to the low pressure zones and begins to swirl because of conservation of angular momentum.

All the air in the world is spinning with the earth. At the north pole the spin rate is 360 degrees every 24 hours, or 15 degrees per hour. The spin rate is slower further south, proportionally to the sine of the latitude, and it is zero at the equator. The spin of the earth at your location is observable with a Foucault pendulum (there is likely to be one found in your science museum). We normally don’t notice the spin of the air around us because the earth is spinning at the same rate, normally. However the air has angular momentum, and when air moves into into a central location the angular speed increases because the angular momentum must be conserved. As the gas moves in, the spin rate must increase in proportion; it eventually becomes noticeable relative to the earth’s spin. Thus, if the air starts out moving at 10 degrees per hour (that’s the spin rate in Detroit, MI 41.8° N), and moves from 800 miles away from a low pressure center to only 200 miles from the center, the angular momentum must increase four times, or to 40 degrees per hour. We would only see 30 degrees/hr of this because the earth is spinning, but the velocity this involves is significant: V= 200 miles * 2* pi *30/360 = 104 mph.

To give students a sense of angular momentum conservation, most science centers (and colleges) use an experiment involving bicycle wheels and a swivel chair. In the science centers there is usually no explanation of why, but in college they tend to explain it in terms of vectors and (perhaps) gauge theories of space-time (a gauge is basically a symmetry; angular momentum is conserved because space is symmetric in rotation). In a hurricane, the air at sea level always spins in the same direction of the earth: counter clockwise in the northern hemisphere, clockwise in the southern, but it does not spin this way forever.

The air that’s sucked into the hurricane become heated and saturated with water. As a result, it becomes less dense, expands, and rises, sucking fresh air in behind it. As the hot wet air rises it cools and much of the water rains down as rain. When the, now dry air reaches a high enough altitude its air pressure is higher than that above the cold regions of the north; the air now flows away north. Because this hot wet air travels north we typically get rain in Michigan when the Carolinas are just being hit by hurricanes. As the air flows away from the centers at high altitudes it begins to spin the opposite direction, by the way, so called counter-cyclonally because angular momentum has to be consevered. At high altitudes over high pressure centers I would expect to find cyclones too (spinning cyclonally) I have not found a reference for them, but suspect that airline pilots are aware of the effect. There is some of this spin at low altitudes, but less so most of the time.

Hurricanes tend to move to the US and north through the hurricane season because, as I understand it, the cold air that keeps coming to feed the hurricane comes mostly from the coastal US. As I understand it the hurricane is not moving as such, the air stays relatively stationary and the swirl that we call a hurricane moves to the US in the effective direction of the sea-level air flow.

For tornadoes, I’m sorry to say, this explanation does not work quite as well, and Wikipedia didn’t help clear things up for me either. The force of tornadoes is much stronger than of hurricanes (the swirl is more concentrated) and the spin direction is not always cyclonic. Also tornadoes form in some surprising areas like Kansas and Michigan where hurricanes never form. My suspicion is that most, but not all tornadoes form from the same low pressure as hurricanes, but by dry heat, not wet. Tornadoes form in Michigan, Texas, and Alabama in the early summer when the ground is dry and warmer than the surrounding lakes and seas. It is not difficult to imagine the air rising from the hot ground and that a cool wind would come in from the water and beginning to swirl. The cold, damp sea air would be more dense than the hot, dry land air, and the dry air would rise. I can imagine that some of these tornadoes would occur with rain, but that many the more intense?) would have little or none; perhaps rain-fall tends to dampen the intensity of the swirl (?)

Now we get to things that I don’t have good explanation for at all: why Kansas? Kansas isn’t particularly hot or cold; it isn’t located near lakes or seas, so why do they have so many tornadoes? I don’t know. Another issue that I don’t understand: why is it that some tornadoes rotate counter cyclonicly? Wikipedia says these tornadoes shed from other tornadoes, but this doesn’t quite seem like an explanation. My guess is that these tornadoes are caused by a relative high pressure source at ground level (a region of cold ground for example) coupled with a nearby low pressure zone (a warm lake?). My guess is that this produces an intense counter-cyclonic flow to the low pressure zone. As for why the pressure is very low in tornadoes, even these that I think are caused by high pressure, I suspect the intense low pressure is an epee-phenomenon caused by the concentration of spin — one I show in my video. That is, I suspect that the low pressure in the center of counter-cyclonic tornadoes is not the cause of the tornado but an artifact of the concentrated spin. Perhaps I’m wrong here, but that’s the explanation that seems to fit best with the info I’ve got. If you’ve got better explanations for these two issues, I’d love to hear them.

Hydrogen Cylinders versus Hydrogen Generators for Gas Chromatography

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Hydrogen is an excellent cover gas for furnace brazing and electronic manufacture; it’s used as a carrier gas for gas chromatography or as a flame-detector gas, and it’s a necessity for ammonia production and most fuel cells. If you are working in one of these fields you can buy bottled hydrogen (cylinders) or a hydrogen generator . The main difference is cost. Cylinder hydrogen is typically the choice for small demand applications. A palladium membrane hydrogen purifier is added ( we make these) if high purity is important. Hydrogen generators are more generally used for larger -demand applications. They are more expensive at the start, but provide convenience and long-term savings. The essay below goes through the benefits and drawbacks of each as applies to gas chromatography.

Point of use Cylinder Hydrogen Is Simple and Allows Easy Monitoring and Control. At the smallest laboratories, those with one or two gas chromatographs, you’ll generally find you are best served by a single hydrogen cylinder for each GC, aided by a hydrogen purifier of some sort. This is called “point of use” hydrogen. Each cylinder is typically belted to a wall and used until the cylinder is empty. At that point, the application is stopped (the purifier is often stopped too) and a new cylinder switched in. There is usually a short break- in period where GC results are unreliable, but after one or two runs, everything is as before. The biggest advantage here is simplicity including ease of pressure control and monitoring. You can always check the pressure right by the GC and adjust it as needed. Long term cost is usually higher, though, and you have to stop whenever a cylinder needs switching.

Multi-cylinder Systems or Generators Provide Fewer interruptions. Larger laboratories tend to use multiple hydrogen cylinders with complex switchover systems, or hydrogen generators. Multiple cylinders are racked together and connected to a manifold and a single, larger purifier (we make these too). Tanks are emptied in series so that there is no disruption. When each tank empties, it is switched out in a way that maintains the flow. One problem is that the pressure and flow does not typically stay constant as the cylinders switch and as additional GCs or other processes are brought on line or taken off.

Purity can suffer too, as there is more tubing and more connections in the system. There is thus more room for leaks and degassing. This can be solved by replacing the single large purifier by point-of-use purifiers, installed just prior to the GC or other application.

Cylinder packs come with a safety disadvantage: with so many cylinders, there is a potential for disastrous leaks or mistakes that empty many cylinders at once — too fast to disperse the large amount of hydrogen released. Maintenance becomes an issue too since the manifolds and automatic switches become complicated quickly. Complex systems can require a trained technician to trouble-shoot and maintain; I sometimes do that, and customers don’t seem to mind, but it’s an issue.

Hydrogen generators can be cheaper and you avoid cylinder changes; Hydrogen generators are fed by tap-water or a very large tank of methanol -water. Running out is less of a problem, and adding more water or methanol to the tank does not affect the hydrogen output.

Safety is improved by limiting the output of the generator to the amount the room will vent. A room with 100 ft3 of air and some circulation can generally host a hydrogen generator 2-3 slpm output with no fear of reaching explosive limits. It’s also worthwhile to fit the hydrogen generator with an alarm or safety that shuts down if a leak is detected (we provide these for purifiers too).

Generator Options: Methanol-based hydrogen generators or electrolysis. Both options are are available in outputs from 250 ccm to 50 slpm. For larger-yet output, you’ll probably want an electrolyzer. In general, either generator will pay for itself in the first year if you use the gas, continuously, or nearly so.

In Electrolytic Hydrogen generators Purified water, either purchased separately, or purified on-site is mixed with an electrolyte, generally KOH, and converted to hydrogen and oxygen by the electrolytic reaction H2O –> H2 + ½ O2.  As the hydrogen produced is generally “wet”, containing water vapor, the hydrogen is then purified by use of a desiccant, or by passage through a metal membrane purifier. Desiccants are cheaper, but the gas is at best 99.9% pure, good enough to feed FIDs, but not good enough to be used as a carrier gas, or for chemical production. Over time desiccants wear out; they require constant monitoring and changing as they become filled with water vapor. Often electrolytic hydrogen generators also require the addition of a caustic electrolyte solution as caustic can leak out, or leave by corrosion mechanisms.

In Reformer-based hydrogen generators a methanol-water mix is pumped to about 300 psi and heated to about 350 °C. It is then sent over a catalyst where it is converted to a hydrogen-containing gas-mix by the reaction CH3OH + H2O –> 3H2 + CO2. Pure hydrogen is extracted from the gas mix by passing it through a membrane, either within the reactor (a membrane reactor), or by use of a membrane purifier external to the reactor.

Cost comparisons. Hydrogen in cylinders is fairly expensive if you use gas continuously. In Detroit, where we are, hydrogen costs about $70 each cylinder low low-purity gas, or $200 for high purity gas. Each cylinder contains 135 scf of gas. If you use 1/10 cylinder per day, you will find you’re spending about $7,300 per year on hydrogen gas, with another $1000 spent on cylinder rental and delivery. This is about the cost of a comparable hydrogen generator plus the water or methanol and electricity run it. If you use significantly less hydrogen you save money with cylinders, if you use more there is significant savings with a generator.

Most hydrogen generators have delivery pressure limitations compared to cylinders. Cylinders have no problem supplying hydrogen at 200 psi or greater pressures. By contrast, generators are limited to only the 60-150 psig range only. This pressure limitation is not likely to be a problem, even for GCs that need higher pressure gas or when the generator must be located far from the  instruments, but you have to be aware of the issue when buying the generator. Electrolysis systems that use caustic provide the highest pressures, but they tend to be the most expensive, and least safe as the operate hot and caustic can drip out. Fuel cell generators and reformers provide lower pressure gas (90 psi maximum, typically), but they are safer. In general generators should be located close to the instruments to minimize supply line pressure drop. If necessary it can pay to use cylinders and generators or several generators to provide a range of delivery pressures and a shorter distance between the hydrogen generator and the application.

Click here for the prices of REB Research hydrogen generators. By comparison, I’ve attached prices for electrolysis-based hydrogen generators here (it’s 2007 data; please check the company yourself for current prices). Finally, the price of membrane purifiers is listed here.

Maintenance required for optimal performance. Often electrolytic hydrogen generators require the addition of a caustic electrolyte solution; desiccant purified gas will require the monitoring and changing of desiccant cartridges to remove residual moisture from the hydrogen. Palladium membrane purifiers systems, and reformer systems need replacement thermocouples and heaters every few years. Understanding the required operating and maintenance procedures is an important part of making an informed decision.

Conclusion:

Cylinder hydrogen supplies are the simplest sources for labs but present a safety, cost, and handling concerns, particularly associated with cylinder change-outs. Generators tend to be more up-front expensive than cylinders but offer safety benefits as well as benefits of continuous supply and consistent purity. They are particularly attractive alternative for larger labs where large hydrogen supply can present larger safety risks, and larger operating costs.

R. E. Buxbaum, January 30, 2013, partially updated Apr. 2022.

The joy of curtains

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By Dr. Robert E. Buxbaum January 18, 2013

In our northern climates most homes have double-paned windows; they cost a fortune, and are a lot better than plain glass, but they still lose a lot of heat: far more than the equivalent area of wall. The insulation value is poor mostly because the thickness is low: a typical double pane window is only ½” thick. The glass panes have hardly any insulation value, so the majority of the insulation is the 0.3″ air space between them. Our outer walls, by contrast, are typically 6” thick filled with glass –wool. The wall is 12 times as thick as the window, and it turns out that the R value is about 12 times as great. Since window area is about 1/10 the wall area, we can expect that about half your homes heat goes out through the windows (about half the air-conditioner cooling in the summer too). A good trick to improve your home’s insulation, then, is to add curtains as this provides a fairly thick layer of stagnant air inside the room, right next to your windows.

To see how much you can save by adding curtains, it’s nice (for me, and my mind-set mostly) to talk in terms of R values. In the northern USA, the “R” value of a typical, well-insulated outer wall is about 24. What that means is that it takes 24°F and one square foot of wall to remove 1 BTU per hour. That is, the resistance to heat loss is 24 °F.hr.ft2/BTU. The R value for a typical double pane window is about 2 in the same units, and is only 1 if you have single panes. The insulating quality of our windows is so poor that, for many homes, more heat is lost through the windows than through the rest of the wall space.

To figure out how much heat is lost through your windows take the area in square feet multiply by a typical temperature differential (50°F might be typical in Michigan), and divide by the R value of your paned windows (1 or 2) depending on whether it’s single or double paned. Since heat costs about $10/MMBTU ($10 per million BTU) for a gas heated house, you can figure out what a small, 10 ft2 window costs a typical Michigan householder as follows, assuming a single pane (R=1):

Q = Area* ∆T/R = 10 ft2 * 50°F/1 = 500 BTU/hr. Here Q is the heat lost per unit time, ∆T is the temperature difference between the window surface and the room, and A is the ara of the window surface.

Since there are 24 hours in a day, and 30.5 days in a month the dollar cost of that window is 500*24*31.5*10/1,000,000 = $3.78/month. After a few years, you’ll have paid $200 for that small window in lost heat and another $200 in air conditioning.

A cheap solution is to add curtains, shades, or plastic of some sort. These should not be placed too close to the window, or you won’t have a decent air gap, nor so far that the air will not be static in the gap. For small gaps between the window glass and your plastic or curtain, the heat transfer rate is proportional to the thermal conductivity of air, k, and inversely proportional to the air gap distance, ∂.

Q = ∆T A k /∂.

R  = ∂/k.

The thermal conductivity of air, k, is about .024 BTU/ft. hr°F. We thus confirm that the the R-value for an air gap of 9/16” or 1/20 foot is about 2 in these units. Though the typical air gap between the glass is less, about .3″ there is some more stagnant air outside the glass an that counts towards the 9/16″ of stagnant air. The k value of glass or plastic is much higher than of air, so the layers of glass or plastic add almost nothing to the total heat transfer resistance.

Because the R value of glass and plastic is so low, if you cover your window with a layer of plastic sheet that touches the window, the insulation effect is basically zero. To get insulation value you want to use a gap between about ½” and 1” in thickness. If you already have a 2 paned window of R value 2, you can expect to be able to raise your insulation value to 4 by adding a plastic sheet or single curtain at 9/16” from the glass.

Sorry to say, you can’t raise this insulation value much higher than 4 by use of a single air gap that’s more than 1″ thick. When a single gap exceeds this size, the insulating value drops dramatically as gas circulation in the gap (free convection) drives heat transfer. That’s why wall insulation has fiber-glass fill. For your home, you will want something more attractive than fiberglass between you and the window pane, and typical approaches  include cellular blinds or double layer drapes. These work on the same principle as the single sheet, but have extra layers that stop convection.

My favorite version of the double drapes is the federalist version, where the inner drape is near transparent, shim cloth hangs close to the window, with a heavier drape beyond that. The heavier curtain is closed at night and opened in daytime; where insulation is needed, the lighter cloth hangs day and night. This looks a lot better than a roll-type window shade, or bamboo screen. Besides, with a roll-shade or bamboo, you must put it close to the window where it will interfere with the convection flow, that is cold shedding from the shut window.

Another nice alternative is a “cell shade” These are folded lengths of two or more stiff cloths that are formed into honeycombs ½” to 2” apart. This empty thickness provides the insulating power of the shade. Placed at the right distance from the window, the cell shade will add 3 or more to the overall R value of the window (1/12 ft / .024 BTU/ft. hr°F = 3.5 ft2hr°F/BTU). As with a bamboo screen, all this R value goes away if the shade is set at more than about 1” from the window or an interior shade. At a greater thickness that this, the free convection flow of cold air between the window and the shade dominates, and you get a puddle of cold air on the floor. 

I would suggest a cellular shade that opens from the bottom only and is translucent. This provides light and privacy; a shade that is too dark will be left open. Behind this, my home has double-pane windows (when I was single the window was covered by a layer of plastic too). The see-through shade provides insulation while allowing one to see out the window (or let light in) when the shade is drawn. You want to be able to see out; that’s the reason you had a window in the first place. Very thick, insulating curtains and blinds seem like a waste to me – they are enough thicker to add any significant R-value, they block the light, and if they end up far from the window, the shedding heat loss will more than offset any small advantage from the thick cloth.

One last window insulation option that’s worth mentioning is a reflective coating on the glass (an e-coating). This is not as bad an idea as you might think, even in a cold climate as in Detroit. A surprising amount of heat tends to escape your windows in the form of radiation. That is, the heat leaves by way of invisible (infra –red) light that passes unimpeded through the double pane glass. In hot climates even more heat comes in this way, and a coating is even more useful to preserve air conditioning power. Reflective plastic coats are cheap enough and readily available, though they can be hard to apply, and are not always attractive.

You can expect to reduce the window heat loss by a factor of 3 or more using these treatments, reducing the heat loss through the small window to $1.00 or so per month, far enough that the main heat loss is through the walls. At that point, it may be worth putting your efforts elsewhere. Window treatments can save you money, make a previously uninhabitable room pleasant, and can help preserve this fair planet of ours. Enjoy.

Updated, Feb 9, 2022, REB.

Engineering joke

An optimist says the cup is half full.

A pessimist says the cup is half empty.

An engineer says the cup is twice as big as it has to be.

(A quantum physicist might say that the water isn’t in the cup till he looks at it; then again, the quantum physicist isn’t there until someone looks at him. And that’s why I’m an engineer).

What is the best hydrogen storage medium?

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Answering best questions is always tricky since best depends on situation, but I’ll cover some hydrogen storage options here, and I’ll try to explain where our product options (cylinder gas purifiers and methanol-water reformers) fit in.

The most common laboratory option for hydrogen storage is inside a tank; typically this tank is made of steel, but it can be made of aluminum, fiberglass or carbon fiber. Tanks are the most convenient source for small volume users since they are instantly ready for delivery at any pressure up to the storage pressure; typically that’s 2000 psi (135 atm) though 10,000 (1350 atm) is available by special order. The maximum practical density for this storage is about 50 g/liter, but this density ignores the weight of the tank. The tank adds a factor of 20 or to the weight, making tanks a less-favored option for mobile users. Tanks also add significantly to the cost. They also tend to add impurities to the gas, and there’s a safety issue too: tanks sometimes fall over, and compressed gas can explode. For small-volume, non-mobile users, one can address safety by chaining up ones tank and adding a metal membrane hydrogen purifier; This is one of our main products.

Another approach is liquid hydrogen; The density of liquid hydrogen is higher than of gas, about 68 g/liter, and you don’t need as a tank that’s a big or heavy. One problem is that you have to keep the liquid quite cold, about 25 K. There are evaporative losses too, and if the vent should freeze shut you will get a massive explosion. This is the storage method preferred by large users, like NASA.

Moving on to metal hydrides. These are heavy and rather expensive but they are safer than the two previous options. To extract hydrogen from a metal hydride bed the entire hydride bed has to be heated, and this adds complexity. To refill the bed, it generally has to be cooled, and this too adds complexity. Generally, you need a source of moderately high pressure, clean, dry hydrogen to recharge a bed. You can get this from either an electrolysis generator, with a metal membrane hydrogen purifier, or by generating the hydrogen from methanol using one of our membrane reactor hydrogen generators.

Borohydrides are similar to metal hydrides, but they can flow. Sorry to say, they are more expensive than normal metal hydrides and they can not be regenerated.They are ideal for some military use

And now finally, chemical materials: water, methanol, and ammonia. Chemical compounds are a lot cheaper than metal hydrides or metal borohydrides, and tend to be far more readily available and transportable being much lighter in weight. Water and/or methanol contains 110 gm of H2/liter;  ammonia contains 120 gms/liter, and the tanks are far lighter and cheaper too. Polyethylene jugs weighing a few ounces suffices to transport gallon quantities of water or methanol and, while not quite as light, relatively cheap metallic containers suffice to hold and transport ammonia.

The optimum choice of chemical storage varies with application and customer need. Water is the safest option, but it can freeze in the cold, and it does not contain its own chemical energy. The energy to split the water has to come externally, typically from electricity via electrolysis. This makes water impractical for mobile applications. Also, the hydrogen generated from water electrolysis tends to be impure, a problem for hydrogen that is intended for storage or chemical manufacture. Still, there is a big advantage to forming hydrogen from something that is completely non-toxic, non-flammable, and readily available, and water definitely has a place among the production options.

Methanol contains its own chemical energy, so hydrogen can be generated by heating alone (with a catalyst), but it is toxic to drink and it is flammable. I’ve found a  my unique way of making hydrogen from methanol-water using  a membrane reactor. Go to my site for sales and other essays.

Finally, ammonia provides it’s own chemical energy like methanol, and is flammable, like methanol; we can convert it to hydrogen with our membrane reactors like we can methanol, but ammonia is far more toxic than methanol, possessing the power to kill with both its vapors and in liquid form. We’ve made ammonia reformers, but prefer methanol.

How much wood could a woodchuck chuck?

How much wood could a woodchuck chuck, if a woodchuck could chuck wood. It’s a classic question with a simple answer: The woodchuck, also known as a groundhog or marmot, is a close relative to the beaver: it looks roughly the same, but is about 1/5 the weight  (10 pounds versus 50 pounds), and beavers do chuck wood, using their teeth to pile it onto their dams. I’ll call the tooth piling process chucking, since that’s what we would call it if a person did it by hand.

Beaver Dam

A beaver dam. From the size of this dam, and the rate of construction (one night) you can figure out how much wood a beaver could chuck, and from that how much a woodchuck could.

A reasonable assumption, is that a wood chuck would chuck about 1/5 as much wood as a beaver does. You might think this isn’t very much wood — and one researcher claimed it would be less than 1/2 lb. — but he’s wrong. A beaver is able to build a dam like the one shown in a single night. From the size of the dam and the speed of building you can estimate that the beaver chucked on the pile about 1000 lbs of wood per night (beavers work at night). To figure out how much wood a woodchuck would chuck, divide this rate by 5. Based on this, I’d estimate that a woodchuck would chuck some 200 lbs per day, if it chose to.

Woodchucks don’t chuck wood, as the question implies. Unlike beavers they do not build wood dams or lodges. Instead they live in burrows in the ground. Also woodchuck teeth are not so useful. Woodchucks do kick up a lot of dirt digging a burrow, as much as 700 lb/ day of dirt, but the question implies that this activity should not be counted as chucking. Well, now you know: it’s 200 lbs/night.

Robert Buxbaum. This post is revised January 30, 2020. My original estimate, from  January 2013 was half the value here. I’d come to believe that wood-chucks/ groundhogs are 1/10 the size of a beaver, so I’d estimated 100 lb/night.