Tag Archives: power

Change home air filters 3 times per year

Energy efficient furnaces use a surprisingly large amount of electricity to blow the air around your house. Part of the problem is the pressure drop of the ducts, but quite a lot of energy is lost bowing air through the dust filter. An energy-saving idea: replace the filter on your furnace twice a year or more. Another idea, you don’t have to use the fanciest of filters. Dirty filters provide a lot of back-pressure especially when they are dirty.

I built a water manometer, see diagram below to measure the pressure drop through my furnace filters. The pressure drop is measured from the difference in the height of the water column shown. Each inch of water is 0.04 psi or 275 Pa. Using this pressure difference and the flow rating of the furnace, I calculated the amount of power lost by the following formula:

W = Q ∆P/ µ.

Here W is the amount of power use, Watts, Q is flow rate m3/s, ∆P = the pressure drop in Pa, and µ is the efficiency of the motor and blower, typically about 50%.

With clean filters (two different brands), I measured 1/8″ and 1/4″ of water column, or a pressure drop of 0.005 and 0.01 psi, depending on the filter. The “better the filter”, that is the higher the MERV rating, the higher the pressure drop. I also measured the pressure drop through a 6 month old filter and found it to be 1/2″ of water, or 0.02 psi or 140 Pa. Multiplying this by the amount of air moved, 1000 cfm =  25 m3 per minute or 0.42 m3/s, and dividing by the efficiency, I calculate a power use of 118 W. That is 0.118 kWh/hr. or 2.8 kWh/day.

water manometer used to measure pressure drop through the filter of my furnace. I stuck two copper tubes into the furnace, and attached a plastic hose. Pressure was measured from the difference in the water level in the hose.

The water manometer I used to measure the pressure drop through the filter of my furnace. I stuck two copper tubes into the furnace, and attached a plastic tube half filled with water between the copper tubes. Pressure was measured from the difference in the water level in the plastic tube. Each 1″ of water is 280 Pa or 0.04psi.

At the above rate of power use and a cost of electricity of 11¢/kWhr, I find it would cost me an extra 4 KWhr or about 31¢/day to pump air through my dirty-ish filter; that’s $113/year. The cost through a clean filter would be about half this, suggesting that for every year of filter use I spend an average of $57t where t is the use life of the filter.

To calculate the ideal time to change filters I set up the following formula for the total cost per year $, including cost per year spent on filters (at $5/ filter), and the pressure-induced electric cost:

$ = 5/t + 57 t.

The shorter the life of the filter, t, the more I spend on filters, but the less on electricity. I now use calculus to find the filter life that produces the minimum $, and determine that $ is a minimum at a filter life t = √5/57 = .30 years.  The upshot, then, if you filters are like mine, you should change your three times a year, or so; every 3.6 months to be super-exact. For what it’s worth, I buy MERV 5 filters at Ace or Home Depot. If I bought more expensive filters, the optimal change time would likely be once or twice per year. I figure that, unless you are very allergic or make electronics in your basement you don’t need a filter with MERV rating higher than 8 or so.

I’ve mentioned in a previous essay/post that dust starts out mostly as dead skin cells. Over time dust mites eat the skin, some pretty nasty stuff. Most folks are allergic to the mites, but I’m not convinced that the filter on your furnace dies much to isolate you from them since the mites, etc tend to hang out in your bed and clothes (a charming thought, I know).

Old fashioned, octopus furnace. Free convection.

Old fashioned, octopus furnace. Free convection.

The previous house I had, had no filter on the furnace (and no blower). I noticed no difference in my tendency to cough or itch. That furnace relied for circulation on the tendency for hot air to rise. That is, “free convection” circulated air through the home and furnace by way of “Octopus” ducts. If you wonder what a furnace like that looks like here’s a picture.

I calculate that a 10 foot column of air that is 30°C warmer than that in a house will have a buoyancy of about 0.00055 psi (1/8″ of water). That’s enough pressure to drive circulation through my home, and might have even driven air through a clean, low MERV dust filter. The furnace didn’t use any more gas than a modern furnace would, as best I could tell, since I was able to adjust the damper easily (I could see the flame). It used no electricity except for the thermostat control, and the overall cost was lower than for my current, high-efficiency furnace with its electrical blower and forced convection.

Robert E. Buxbaum, December 7, 2017. I ran for water commissioner, and post occasional energy-saving or water saving ideas. Another good energy saver is curtains. And here are some ideas on water-saving, and on toilet paper.

Of horses, trucks, and horsepower

Horsepower is a unit of work production rate, about 3/4 of a kW, for those who like standard international units. It is also the pulling force of a work horse of the 1700s times its speed when pulling, perhaps 5 mph. A standard truck will develop 200 hp but only while accelerating at about 60 mph; to develop those same 200 horsepower at 1 mph it would have to pull with 200 times more force. That is impossible for a truck, both because of traction limitations and because of the nature of a gasoline engine when attached to typical gearing. At low speed, 1 mph, a truck will barely develop as much force as 4-5 horses, suggesting a work output about 1 hp. This is especially true for a truck pulling in the snow, as shown in the video below.

Here, a semi-truck (of milk) is being pulled out of the snow by a team of horses going perhaps 1 mph. The majority of work is done by the horse on the left — the others seem to be slipping. Assuming that the four horses manage to develop 1 hp each (4 hp total), the pull force is four times a truck at 1 mph, or as great as a 200 hp truck accelerating at 50 mph. That’s why the horse succeed where the truck does not.

You will find other videos on the internet showing that horses produce more force or hp than trucks or tractors. They always do so at low speeds. A horse will also beat a truck or car in acceleration to about the 1/4 mile mark. That’s because acceleration =force /mass: a = F/m.

I should mention that DC electric motors also, like horses, produce their highest force at very low speeds, but unlike horses, their efficiency is very low there. Electric engine efficiency is high only at speeds quite near the maximum and their horse-power output (force times speed) is at a maximum at about 1/2 the maximum speed.

Steam engines (I like steam engines) produce about the same force at all speeds, and more-or-less the same efficiency at all speeds. That efficiency is typically only about 20%, about that of a horse, but the feed cost and maintenance cost is far lower. A steam engine will eat coal, while a horse must eat oats.

March 4, 2016. Robert Buxbaum, an engineer, runs REB Research, and is running for water commissioner.

Advanced windmills + 20 years = field of junk

Everything wears out. This can be a comforting or a depressing thought, but it’s a truth. No old mistake, however egregious, lasts forever, and no bold advance avoids decay. At best, last year’s advance will pay for itself with interest, will wear out gracefully, and will be recalled fondly by aficionados after it’s replaced by something better. Water wheels, and early steamships are examples of this type of bold advance. Unfortunately, it is often the case that last years innovation turns out to be no advance at all: a technological dead end that never pays for itself, and becomes a dangerous, rotting eyesore or worse, a laughing-stock blot or a blot on the ecology. Our first two generations of advanced windmill farms seem to match this description; perhaps the next generation will be better, but here are some thoughts on lessons learned from the existing fields of rotting windmills.

The ancient design windmills of Don Quixote’s Spain (1300?) were boons. Farmers used them to grind grain or cut wood, and to to pump drinking water. Holland used similar early windmills to drain their land. So several American presidents came to believe advanced design windmills would be similar boons if used for continuous electric power generation. It didn’t work, and many of the problems could have been seen at the start. While the farmer didn’t care when his water was pumped, or when his wood is cut. When you’re generating electricity, there is a need to match the power demand exactly. Whenever the customer turns on the switch, electricity is expected to flow at the appropriate amount of Wattage; at other times any power generated is a waste or a nuisance. But electric generator-windmills do not produce power on demand, they produce power when the wind blows. The mismatch of wind and electric demand has bedeviled windmill reliability and economic return. It will likely continue to do so until we find a good way to store electric power cheaply. Until then windmills will not be able to produce electricity at competitive prices to compete with cheap coal and nuclear power.

There is also the problem of repair. The old windmills of Holland still turn a century later because they were relatively robust, and relatively easy to maintain. The modern windmills of the US stand much taller and move much faster. They are often hit, and damaged by lightning strikes, and their fast-turning gears tend to wear out fast, Once damaged, modern windmills are not readily fix, They are made of advanced fiberglass materials spun on special molds. Worse yet, they are constructed in mountainous, remote locations. Such blades can not be replaces by amateurs, and even the gears are not readily accessed to repair. More than half of the great power-windmills built in the last 35 years have worn out and are unlikely to ever get repair. Driving past, you see fields of them sitting idle; the ones still turning look like they will wear out soon. The companies that made and installed these behemoth are mostly out of the business, so there is no-one there to take them down even if there were an economic incentive to do so. Even where a company is found to fix the old windmills, no one would as there is not sufficient economic return — the electricity is worth less than the repair.

Komoa Wind Farm in Kona, Hawaii June 2010; Friends of Grand Ronde Valley.

Komoa Wind Farm in Kona, Hawaii, June 2010; A field of modern design wind-turbines already ruined by wear, wind, and lightning. — Friends of Grand Ronde Valley.

A single rusting windmill would be bad enough, but modern wind turbines were put up as wind farms with nominal power production targeted to match the output of small coal-fired generators. These wind farms require a lot of area,  covering many square miles along some of the most beautiful mountain ranges and ridges — places chosen because the wind was strong

Putting up these massive farms of windmills lead to a situation where the government had pay for construction of the project, and often where the government provided the land. This, generous spending gives the taxpayer the risk, and often a political gain — generally to a contributor. But there is very little political gain in paying for the repair or removal of the windmills. And since the electricity value is less than the repair cost, the owners (friends of the politician) generally leave the broken hulks to sit and rot. Politicians don’t like to pay to fix their past mistakes as it undermines their next boondoggle, suggesting it will someday rust apart without ever paying for itself.

So what can be done. I wish I could suggest less arrogance and political corruption, but I see no way to achieve that, as the poet wrote about Ozymandias (Ramses II) and his disastrous building projects, the leader inevitably believes: “I am Ozymandias, king of kings; look on my works ye mighty and despair.” So I’ll propose some other, less ambitious ideas. For one, smaller demonstration projects closer to the customer. First see if a single windmill pays for itself, and only then build a second. Also, electricity storage is absolutely key. I think it is worthwhile to store excess wind power as hydrogen (hydrogen storage is far cheaper than batteries), and the thermodynamics are not bad

Robert E. Buxbaum, January 3, 2016. These comments are not entirely altruistic. I own a company that makes hydrogen generators and hydrogen purifiers. If the government were to take my suggestions I would benefit.

I make weapons too, but they don’t work

My company, REB Research, makes items with mostly peaceful uses: hydrogen purifiers and hydrogen generators — used to make silicon chips and to power fuel cells. Still, several of our products have advanced military uses, and these happen to be our most profitable items. The most problematic of these is the core for a hydrogen-powered airplane designed to stay up forever. An airplane like this could be used for peace, e.g. as a cheap, permanent cell tower, or for finding shipwrecks in the middle of the ocean. But it could also be used for spying on US citizens. Ideally I’d like to see my stuff used for desirable ends, but know it’s not always that way.

See, no matter how many times I pull the trigger the damn thing just won't fire! Gahan Wilson;

See what I mean? No matter how many times I pull the trigger the damned thing just won’t fire! Gahan Wilson;

I’d be less bothered if I had more faith that my government will only spy on bad guys, but I don’t. Our politicians seem focused on staying in office, and most presidents of the 20th century have kept enemies lists of those who they’d like to get back at — politics isn’t pretty. I’d be more picky if I could figure out how to sell more stuff, but so far I have not. I thus need the work. I take a sort-of comfort, however, in the fact that the advanced nature of the technology means that my customers keep having troubles getting things to work. My parts work, but the plane has yet to fly as intended. Perhaps, by the time they do get it flying, spying may have changed enough that my stuff will be used only for beneficial service to mankind, or as a stepping stone to more general use. Hydrogen as a fuel makes a lot of sense, especially for airplanes.

Robert E. Buxbaum, June 15, 2015. Here’s a description of my membrane reactors, and a description of my latest fuel cell reformer idea. There are basically two types of engineer; those who make weapons and those who make targets. I make the case here that you want to make targets. Some weapons have only one short day in the sun, e.g. the Gatling gun.

Loyalty, part 2: power hurts the leader

In a previous post, I made the case that one should avoid accepting loyalty requests as these are generally requests for your self-destruction. Someone who asks for loyalty is not saying he’ll provide you with good pay, a comfortable environment, empowerment, and good security. Rather that he wants your service despite little or not pay, discomfort, enslavement, and likely death or disgrace. There are some, few exceptions, but loyal service of this type rarely serves the servant.

Your chance of surviving as a minion is low; your chance as master is lower.

Your chance of surviving as a minion is low; your chance as master is lower.

I’d now like to claim that having loyal followers hurts the leader, too, costing him good service, and separating him from health, friends, and family. Most leaders are better off as half of a duopoly, without minions, and only loose control of their workers. The first reason for this is to note that minions don’t do good work relative to free men. They die for no good reason (e.g. you forgot to feed them), or they stop work and wonder what you’d like next, or they get drunk and gripe, or they beat each other up over fervor or small territorial issues. They very rarely innovate or work together, and for any complex project like taking over the world (or the tristate area) needs workers who do. Good work requires pride in achievement, and a loyal slave has none.

Having loyal followers precludes one from having a close relationship with the followers (you can’t appear weak), and also with friends (your minions must have one leader, not two). The leader gets used to being surrounded by sycophants, and begins to doubt those who behave otherwise. The boss will begin to distrust friends and allies, those he needs to stay in power, as these are the very people who could most easily assist others to take leadership from him. Over time, the king, boss, monopolist and dictator share less and less. As a result they end up secret and bitter, with many fears and none he can call close. And what pleasure is there in power, if one can’t share the rewards with friends and family, or share the burden with others.

Only support someone who could rule reasonably honestly and well. Chaos is worse than a dictator. Kanin from the New Yorker.

Only support someone who could rule reasonably honestly and well. Chaos is worse than a dictator. Kanin from the New Yorker.

A great number of kings have killed themselves in one way or another, very often because of overly large ambitions (see cartoon). King Saul, in the Bible is perhaps the first, Hitler is perhaps the most famous, and Colonel Qadhafi of Libya is perhaps the most recent. More often, maximum leaders are murdered, typically by friends and family. Famous examples include Julius Caesar, Augustus Caesar, and Nero; Charles I, Louis XVI, Richard III, and Tzar Alexander. Both the king of rock (Elvis) and the king of pop (Michael Jackson) killed themselves with drugs. Yet others died in needless wars or were exiled. Napoleon was defeated, exiled, returned, re-exiled and then murdered by an associate.  It’s not that safe to be the infallible king. Perhaps the wisest move is that of Pope Benedict, who last year left Rome for a life of monk-like solitude. Machiavelli points out, in “The Prince”, that only two Roman Emperors died of natural causes, one because he became emperor at a very old age, and the other was Marcus Aurelius, an advanced ruler who empowered his subjects.

The great leaders create so much space for others to lead that they are almost invisible: they lead by offering encouragement.

Political bosses and monopolist businessmen, though lower in power, don’t fare much better in life. Boss Tweed died in jail, as did Capone, Boss Pendergast. Even if they avoid jail, the fact that no one likes you takes a toll. No one liked Vanderbilt or Rockefeller, Carnegie, Morgan, or Fisk. While they lived, they could expect nothing more than senate investigations and ugly lampoons in the free press, plus an unfavorable memory after death. William Hearst and Howard Hughes died as virtual hermits, best remembered as the inspiration for “Citizen Kane” and “The Navigator.” Peter Cooper and Steve Jobs are different,  industrialists liked in life and in death; and Bill Gates may join them too. Their secret was to empower others.

He's being eaten alive by his power, money, and respect. In the end, he had none.

He’s being eaten alive by his power, money, and respect, as are all those he might love.

Woe to the wife, child or friend of the dictator. The wife and children of a king or king-pin rarely enjoy much of the power. The king-pin doesn’t trust them (often with good reason), and neither do the people. Stalin killed his wife and children as did Nero, Frederick the Great, Herod, Hitler, and quite a few others. It was said that is was preferable to be an animal in the courtyard of these greats than a son at their table. And even if the king or king-pin doesn’t kill his wife child or son, the people often do e.g. Marie Antoinette was killed shortly after Louis XVI and the Tzarina of Russia alongside Alexander III. Similarly, the wife of Hitler, the Mistress of Mussolini, and the wife of Nicolae Ceausescu all died at their husband’s side, sharing the punishment for their husband’s ambition.

The kings of Sparta fared relatively well, as did their wives, despite the militarism of Sparta. Their trick was that Sparta was a du-archy, a country with two kings. Sparta was strong and stable, and their kings (mostly) died at home. In business too, it seems the selfish leader should step back and become almost invisible. It helps him, and helps the people too. If the leader can’t share power this way, he or she should at least give people a simple choice between two things he controls and accepts (chocolate and vanilla; Democrat and Republican). Workers with a choice, even a small one, learn to act somewhat independently, and customers (or citizens) don’t complain as much either if they have some control over their fate. All will come to like the leader more, and the leader will like himself more. People stopped resenting Microsoft when there was a viable alternative, Apple, and Microsoft engineers benefitted by having a competitor to their products. I suspect that Bill Gates realized this would happen when he helped fund Apple’s return to the market. Unfortunately, most monopolists, bosses, and king-pins are too stupid, or too afraid to do this. In the end, it’s the trapped employee or follower who shoots the leader from behind.

Einstein on freedom producing good. I'd say freedom is also a good in itself

The ideal situation is a delicate balance between control and freedom. A great leader will empower those around him and support the opposition. That was the unrealized sense of Mao Tse Tung’s hundred flowers movement (let 100 flowers bloom; left 100 schools of thought contend). It’s political tensegrity. Most leaders can not let go to do this (Mao could not). Still, there IS a sanity clause, Virginia. And a leader should know that there is no benefit to the king who gains the whole world and loses his friends, family and sleep.

Robert Buxbaum. Remember, remember the 5th of November; those oppressed, and those imagining themselves oppressed rise and plot.

The future of steamships: steam

Most large ships and virtually all locomotives currently run on diesel power. But the diesel  engine does not drive the wheels or propeller directly; the transmission would be too big and complex. Instead, the diesel engine is used to generate electric power, and the electric power drives the ship or train via an electric motor, generally with a battery bank to provide a buffer. Current diesel generators operate at 75-300 rpm and about 40-50% efficiency (not bad), but diesel fuel is expensive. It strikes me, therefore that the next step is to switch to a cheaper fuel like coal or compressed natural gas, and convert these fuels to electricity by a partial or full steam cycle as used in land-based electric power plants

Ship-board diesel engine, 100 MW for a large container ship

Diesel engine, 100 MW for a large container ship

Steam powers all nuclear ships, and conventionally boiled steam provided the power for thousands of Liberty ships and hundreds of aircraft carriers during World War 2. Advanced steam turbine cycles are somewhat more efficient, pushing 60% efficiency for high pressure, condensed-turbine cycles that consume vaporized fuel in a gas turbine and recover the waste heat with a steam boiler exhausting to vacuum. The higher efficiency of these gas/steam turbine engines means that, even for ships that burn ship-diesel fuel (so-called bunker oil) or natural gas, there can be a cost advantage to having a degree of steam power. There are a dozen or so steam-powered ships operating on the great lakes currently. These are mostly 700-800 feet long, and operate with 1950s era steam turbines, burning bunker oil or asphalt. US Steel runs the “Arthur M Anderson”, Carson J Callaway” , “John G Munson” and “Philip R Clarke”, all built-in 1951/2. The “Upper Lakes Group” runs the “Canadian Leader”, “Canadian Provider”, “Quebecois”, and “Montrealais.” And then there is the coal-fired “Badger”. Built in 1952, the Badger is powered by two, “Skinner UniFlow” double-acting, piston engines operating at 450 psi. The Badger is cost-effective, with the low-cost of the fuel making up for the low efficiency of the 50’s technology. With larger ships, more modern boilers and turbines, and with higher pressure boilers and turbines, the economics of steam power would be far better, even for ships with modern pollution abatement.

Nuclear steam boilers can be very compact

Nuclear steam boilers can be very compact

Steam powered ships can burn fuels that diesel engines can’t: coal, asphalts, or even dry wood because fuel combustion can be external to the high pressure region. Steam engines can cost more than diesel engines do, but lower fuel cost can make up for that, and the cost differences get smaller as the outputs get larger. Currently, coal costs 1/10 as much as bunker oil on a per-energy basis, and natural gas costs about 1/5 as much as bunker oil. One can burn coal cleanly and safely if the coal is dried before being loaded on the ship. Before burning, the coal would be powdered and gassified to town-gas (CO + H2O) before being burnt. The drying process removes much of the toxic impact of the coal by removing much of the mercury and toxic oxides. Gasification before combustion further reduces these problems, and reduces the tendency to form adhesions on boiler pipes — a bane of old-fashioned steam power. Natural gas requires no pretreatment, but costs twice as much as coal and requires a gas-turbine, boiler system for efficient energy use.

Todays ships and locomotives are far bigger than in the 1950s. The current standard is an engine output about 50 MW, or 170 MM Btu/hr of motive energy. Assuming a 50% efficient engine, the fuel use for a 50 MW ship or locomotive is 340 MM Btu/hr; locomotives only use this much when going up hill with a heavy load. Illinois coal costs, currently, about $60/ton, or $2.31/MM Btu. A 50 MW engine would consume about 13 tons of dry coal per hour costing $785/hr. By comparison, bunker oil costs about $3 /gallon, or $21/MM Btu. This is nearly ten times more than coal, or $ 7,140/hr for the same 50 MW output. Over 30 years of operation, the difference in fuel cost adds up to 1.5 billion dollars — about the cost of a modern container ship.

Robert E. Buxbaum, May 16, 2014. I possess a long-term interest in economics, thermodynamics, history, and the technology of the 1800s. See my steam-pump, and this page dedicated to Peter Cooper: Engineer, citizen of New York. Wood power isn’t all that bad, by the way, but as with coal, you must dry the wood, or (ideally) convert it to charcoal. You can improve the power and efficiency of diesel and automobile engines and reduce the pollution by adding hydrogen. Normal cars do not use steam because there is more start-stop, and because it takes too long to fire up the engine before one can drive. For cars, and drone airplanes, I suggest hydrogen/ fuel cells.

Ivanpah’s solar electric worse than trees

Recently the DoE committed 1.6 billion dollars to the completion of the last two of three solar-natural gas-electric plants on a 10 mi2 site at Lake Ivanpah in California. The site is rated to produce 370 MW of power, in a facility that uses far more land than nuclear power, at a cost significantly higher than nuclear. The 3900 MW Drax plant (UK) cost 1.1 Billion dollars, and produces 10 times more power on a much smaller site. Ivanpah needs a lot of land because its generators require 173,500 billboard-size, sun-tracking mirrors to heat boilers atop three 750 foot towers (2 1/2 times the statue of liberty). The boilers feed steam to low pressure, low efficiency (28% efficiency) Siemens turbines. At night, natural gas provides heat to make the steam, but only at the same, low efficiency. Siemens makes higher efficiency turbine plants (59% efficiency) but these can not be used here because the solar oven temperature is only 900°F (500°C), while normal Siemens plants operate at 3650°F (2000°C).

The Ivanpau thermal solar-natural gas project will look like The Crescent Dunes Thermal-solar project shown here, but will be bigger.

The first construction of the Ivanpah thermal solar-natural-gas project; Each circle mirrors extend out to cover about 2 square miles of the 10mi2 site.

So far, the first of the three towers is operational, but it has been producing at only 30% of rated low-efficiency output. These are described as “growing pains.” There are also problems with cooked birds, blinded pilots, and the occasional fire from the misaligned death ray — more pains, I guess. There is also the problem of lightning. When hit by lightning the mirrors shatter into millions of shards of glass over a 30 foot radius, according to Argus, the mirror cleaning company. This presents a less-than attractive environmental impact.

As an exercise, I thought I’d compare this site’s electric output to the amount one could generate using a wood-burning boiler fed by trees growing on a similar sized (10 sq. miles) site. Trees are cheap, but only about 10% efficient at converting solar power to chemical energy, thus you might imagine that trees could not match the power of the Ivanpah plant, but dry wood burns hot, at 1100 -1500°C, so the efficiency of a wood-powered steam turbine will be higher, about 45%. 

About 820 MW of sunlight falls on every 1 mi2 plot, or 8200 MW for the Ivanpah site. If trees convert 10% of this to chemical energy, and we convert 45% of that to electricity, we find the site will generate 369 MW of electric power, or exactly the output that Ivanpah is rated for. The cost of trees is far cheaper than mirrors, and electricity from wood burning is typically cost 4¢/kWh, and the environmental impact of tree farming is likely to be less than that of the solar mirrors mentioned above. 

There is another advantage to the high temperature of the wood fire. The use of high temperature turbines means that any power made at night with natural gas will be produced at higher efficiency. The Ivanpah turbines output at low temperature and low efficiency when burning natural gas (at night) and thus output half the half the power of a normal Siemens plant for every BTU of gas. Because of this, it seems that the Ivanpah plant may use as much natural gas to make its 370 MW during a 12 hour night as would a higher efficiency system operating 24 hours, day and night. The additional generation by solar thus, might be zero. 

If you think the problems here are with the particular design, I should also note that the Ivanpah solar project is just one of several our Obama-government is funding, and none are doing particularly well. As another example, the $1.45 B solar project on farmland near Gila Bend Arizona is rated to produce 35 MW, about 1/10 of the Ivanpah project at 2/3 the cost. It was built in 2010 and so far has not produced any power.

Robert E. Buxbaum, March 12, 2014. I’ve tried using wood to make green gasoline. No luck so far. And I’ve come to doubt the likelihood that we can stop global warming.

Nuclear fusion

I got my PhD at Princeton University 33 years ago (1981) working on the engineering of nuclear fusion reactors, and I thought I’d use this blog to rethink through the issues. I find I’m still of the opinion that developing fusion is important as the it seems the best, long-range power option. Civilization will still need significant electric power 300 to 3000 years from now, it seems, when most other fuel sources are gone. Fusion is also one of the few options for long-range space exploration; needed if we ever decide to send colonies to Alpha Centauri or Saturn. I thought fusion would be ready by now, but it is not, and commercial use seems unlikely for the next ten years at least — an indication of the difficulties involved, and a certain lack of urgency.

Oil, gas, and uranium didn’t run out like we’d predicted in the mid 70s. Instead, population growth slowed, new supplies were found, and better methods were developed to recover and use them. Shale oil and fracking unlocked hydrocarbons we thought were unusable, and nuclear fission reactors got better –safer and more efficient. At the same time, the more we studied, the clearer it came that fusion’s technical problems are much harder to tame than uranium fission’s.

Uranium fission was/is frighteningly simple — far simpler than even the most basic fusion reactor. The first nuclear fission reactor (1940) involved nothing more than uranium pellets in a pile of carbon bricks stacked in a converted squash court at the University of Chicago. No outside effort was needed to get the large, unstable uranium atoms split to smaller, more stable ones. Water circulating through the pile removed the heat released, and control was maintained by people lifting and lowering cadmium control rods while standing on the pile.

A fusion reactor requires high temperature or energy to make anything happen. Fusion energy is produced by combining small, unstable heavy hydrogen atoms into helium, a bigger more stable one, see figure. To do this reaction you need to operate at the equivalent of about 500,000,000 degrees C, and containing it requires (typically) a magnetic bottle — something far more complex than a pile of graphic bricks. The reward was smaller too: “only” about 1/13th as much energy per event as fission. We knew the magnetic bottles were going to be tricky, e.g. there was no obvious heat transfer and control method, but fusion seemed important enough, and the problems seemed manageable enough that fusion power seemed worth pursuing — with just enough difficulties to make it a challenge.

Basic fusion reaction: deuterium + tritium react to give helium, a neutron and energy.

Basic fusion reaction: deuterium + tritium react to give helium, a neutron and energy.

The plan at Princeton, and most everywhere, was to use a TOKAMAK, a doughnut-shaped reactor like the one shown below, but roughly twice as big; TOKAMAK was a Russian acronym. The doughnut served as one side of an enormous transformer. Hydrogen fuel was ionized into a plasma (a neutral soup of protons and electrons) and heated to 300,000,000°C by a current in the TOKOMAK generated by varying the current in the other side of the transformer. Plasma containment was provided by enormous magnets on the top and bottom, and by ring-shaped magnets arranged around the torus.

As development went on, we found we kept needing bigger and bigger doughnuts and stronger and stronger magnets in an effort to balance heat loss with fusion heating. The number density of hydrogen atoms per volume, n, is proportional to the magnetic strength. This is important because the fusion heat rate per volume is proportional to n-squared, n2, while heat loss is proportional to n divided by the residence time, something we called tau, τ. The main heat loss was from the hot plasma going to the reactor surface. Because of the above, a heat balance ratio was seen to be important, heat in divided by heat out, and that was seen to be more-or-less proportional to nτ. As the target temperatures increased, we found we needed larger and larger nτ reactors to make a positive heat balance. And this translated to ever larger reactors and ever stronger magnetic fields, but even here there was a limit, 1 billion Kelvin, a thermodynamic temperature where the fusion reaction went backward and no energy was produced. The Princeton design was huge, with super strong, super magnets, and was operated at 300 million°C, near the top of the reaction curve. If the temperature went above or below this temperature, the fire would go out. There was no room for error, but relatively little energy output per volume — compared to fission.

Fusion reaction options and reaction rates.

Fusion reaction options and reaction rates.

The most likely reaction involved deuterium and tritium, referred to as D and T. This was the reaction of the two heavy isotopes of hydrogen shown in the figure above — the same reaction used in hydrogen bombs, a point we rarely made to the public. For each reaction D + T –> He + n, you get 17.6 million electron volts (17.6 MeV). This is 17.6 million times the energy you get for an electron moving over one Volt, but only 1/13 the energy of a fission reaction. By comparison, the energy of water-forming, H2 + 1/2 O2 –> H2O, is the equivalent of two electrons moving over 1.2 Volts, or 2.4 electron volts (eV), some 8 million times less than fusion.

The Princeton design involved reacting 40 gm/hr of heavy hydrogen to produce 8 mol/hr of helium and 4000 MW of heat. The heat was converted to electricity at 38% efficiency using a topping cycle, a modern (relatively untried) design. Of the 1500 MWh/hr of electricity that was supposed to be produced, all but about 400 MW was to be delivered to the power grid — if everything worked right. Sorry to say, the value of the electricity did not rise anywhere as fast as the cost of the reactor and turbines. Another problem: 1100 MW was more than could be easily absorbed by any electrical grid. The output was high and steady, and could not be easily adjusted to match fluctuating customer demand. By contrast a coal plant’s or fuel cell’s output could be easily adjusted (and a nuclear plant with a little more difficulty).

Because of the need for heat balance, it turned out that at least 9% of the hydrogen had to be burnt per pass through the reactor. The heat lost per mol by conduction to the wall was, to good approximation, the heat capacity of each mol of hydrogen ions, 82 J/°C mol, times the temperature of the ions, 300 million °C divided by the containment time, τ. The Princeton design was supposed to have a containment of about 4 seconds. As a result, the heat loss by conduction was 6.2 GW per mol. This must be matched by the molar heat of reaction that stayed in the plasma. This was 17.6 MeV times Faraday’s constant, 96,800 divided by 4 seconds (= 430 GW/mol reacted) divided by 5. Of the 430 GW/mol produced in fusion reactions only 1/5 remains in the plasma (= 86 GW/mol) the other 4/5 of the energy of reaction leaves with the neutron. To get the heat balance right, at least 9% of the hydrogen must react per pass through the reactor; there were also some heat losses from radiation, so the number is higher. Burn more or less percent of the hydrogen and you had problems. The only other solution was to increase τ > 4 seconds, but this meant ever bigger reactors.

There was also a material handling issue: to get enough fuel hydrogen into the center of the reactor, quite a lot of radioactive gas had to be handled — extracted from the plasma chamber. These were to be frozen into tiny spheres of near-solid hydrogen and injected into the reactor at ultra-sonic velocity. Any slower and the spheres would evaporate before reaching the center. As 40 grams per hour was 9% of the feed, it became clear that we had to be ready to produce and inject 1 pound/hour of tiny spheres. These “snowballs-in-hell” had to be small so they didn’t dampen the fire. The vacuum system had to be able to be big enough to handle the lb/hr or so of unburned hydrogen and ash, keeping the pressure near total vacuum. You then had to purify the hydrogen from the ash-helium and remake the little spheres that would be fed back to the reactor. There were no easy engineering problems here, but I found it enjoyable enough. With a colleague, I came up with a cute, efficient high vacuum pump and recycling system, and published it here.

Yet another engineering challenge concerned the difficulty of finding a material for the first-wall — the inner wall of the doughnut facing the plasma. Of the 4000 MW of heat energy produced, all the conduction and radiation heat, about 1000 MW is deposited in the first wall and has to be conducted away. Conducting this heat means that the wall must have an enormous coolant flow and must withstand an enormous amount of thermal stress. One possible approach was to use a liquid wall, but I’ve recently come up with a rather nicer solid wall solution (I think) and have filed a patent; more on that later, perhaps after/if the patent is accepted. Another engineering challenge was making T, tritium, for the D-T reaction. Tritium is not found in nature, but has to be made from the neutron created in the reaction and from lithium in a breeder blanket, Li + n –> He + T. I examined all possible options for extracting this tritium from the lithium at low concentrations as part of my PhD thesis, and eventually found a nice solution. The education I got in the process is used in my, REB Research hydrogen engineering business.

Man inside the fusion reactor doughnut at ITER. He'd better leave before the 8,000,000°C plasma turns on.

Man inside the fusion reactor doughnut at ITER. He’d better leave before the 8,000,000°C plasma turns on.

Because of its complexity, and all these engineering challenges, fusion power never reached the maturity of fission power; and then Three-mile Island happened and ruined the enthusiasm for all things nuclear. There were some claims that fusion would be safer than fission, but because of the complexity and improvements in fission, I am not convinced that fusion would ever be even as safe. And the long-term need keeps moving out: we keep finding more uranium, and we’ve developed breeder reactors and a thorium cycle: technologies that make it very unlikely we will run out of fission material any time soon.

The main, near term advantage I see for fusion over fission is that there are fewer radioactive products, see comparison.  A secondary advantage is neutrons. Fusion reactors make excess neutrons that can be used to make tritium, or other unusual elements. A need for one of these could favor the development of fusion power. And finally, there’s the long-term need: space exploration, or basic power when we run out of coal, uranium, and thorium. Fine advantages but unlikely to be important for a hundred years.

Robert E. Buxbaum, March 1, 2014. Here’s a post on land use, on the aesthetics of engineering design, and on the health risks of nuclear power. The sun’s nuclear fusion reactor is unstable too — one possible source of the chaotic behavior of the climate. Here’s a control joke.

Land use nuclear vs wind and solar

An advantage of nuclear power over solar and wind is that it uses a lot less land, see graphic below. While I am doubtful that industrial gas causes global warming, I am not a fan of pollution, and that’s why I like nuclear power. Nuclear power adds no water or air pollution when it runs right, and removes a lot less land than wind and solar. Consider the newly approved Hinkley Point C (England), see graphic below. The site covers 430 acres, 1.74 km2, and is currently the home of Hinkley Point B, a nuclear plant slated for retirement. When Hinkley Point C is built on the same site, it will add 26 trillion Watt-hr/ year (3200 MW, 93% up time), about 7% of the total UK demand. Yet more power would be provided from these 430 acres if Hinkley B is not shut down.

Nuclear land use vs solar and wind; British Gov't. regarding their latest plant

Nuclear land use vs solar and wind; British Gov’t. regarding their latest plant

A solar farm to produce 26 trillion W-hr/year would require 130,000 acres, 526 km2. This area would suggest they get the equivalent of 1.36 hours per day of full sun on every m2, not unreasonable given the space for roads and energy storage, and how cloudy England is. Solar power requires a lot energy-storage since you only get full power in the daytime, when there are no clouds.

A wind farm requires even more land than solar, 250,000 acres, or somewhat more than 1000 km2. Wind farms require less storage but that the turbines be spaced at a distance. Storage options could include hydrogen, batteries, and pumped hydro.; I make the case that hydrogen is better. While wind-farm space can be dual use — allowing farming for example, 1000 square km, is still a lot of space to carve up with roads and turbines. It’s nearly the size of greater London; the tourist area, London city is only 2.9 km2.

All these power sources produce pollution during construction and decommissioning. But nuclear produces somewhat less as the plants are less massive in total, and work for more years without the need for major rebuilds. Hinkley C will generate about 30,000 kg/year of waste assuming 35 MW-days/kg, but the cost to bury it in salt domes should not be excessive. Salt domes are needed because Hinkley waste will generate 100 kW of after-heat, even 16 years out. Nuclear fusion, when it comes, should produce 1/10,000 as much after-heat, 100W, 1 year out, but fusion isn’t here yet.

There is also the problem of accidents. In the worst nuclear disaster, Chernobyl, only 31 people died as a direct result, and now (strange to say) the people downwind are healthier than the average up wind; it seems that small amounts of radiation may be good for you. By comparison, in Iowa alone there were 317 driving fatalities in 2013. And even wind and solar have accidents, e.g. people falling from wind-turbines.

Robert Buxbaum, January 22, 2014. I’m president of REB Research, a manufacturer of hydrogen generators and purifiers — mostly membrane reactor based. I also do contract research, mostly on hydrogen, and I write this blog. My PhD research was on nuclear fusion power. I’ve also written about conservation, e.g. curtainsinsulation; paint your roof white.

Camless valves and the Fiat-500

One of my favorite automobile engine ideas is the use of camless, electronic valves. It’s an idea whose advantages have been known for 100 years or more, and it’s finally going to be used on a mainstream, commercial car — on this year’s Fiat 500s. Fiat is not going entirely camless, but the plan is to replace the cams on the air intake valves with solenoids. A normal car engine uses cams and lifters to operate the poppet valves used to control the air intake and exhaust. Replacing these cams and lifters saves some weight, and allows the Fiat-500 to operate more efficiently at low power by allowing the engine to use less combustion energy to suck vacuum. The Fiat 500 semi-camless technology is called Multiair: it’s licensed from Valeo (France), and appeared as an option on the 2010 Alfa Romeo.

How this saves mpg is as follows: at low power (idling etc.), the air intake of a normal car engine is restricted creating a fairly high vacuum. The vacuum restriction requires energy to draw and reduces the efficiency of the engine by decreasing the effective compression ratio. It’s needed to insure that the car does not produce too much NOx when idling. In a previous post, I showed that the rate of energy wasted by drawing this vacuum was the vacuum pressure times the engine volume and the rpm rate; I also mentioned some classic ways to reduce this loss (exhaust recycle and adding water).

Valeo’s/Fiat’s semi-camless design does nothing to increase the effective compression ratio at low power, but it reduces the amount of power lost to vacuum by allowing the intake air pressure to be higher, even at low power demand. A computer reduces the amount of air entering the engine by reducing the amount of time that the intake valve is open. The higher air pressure means there is less vacuum penalty, both when the valve is open even when the valve is closed. On the Alfa Romeo, the 1.4 liter Multiair engine option got 8% better gas mileage (39 mpg vs 36 mpg) and 10% more power (168 hp vs 153 hp) than the 1.4 liter cam-driven engine.

David Bowes shows off his latest camless engines at NAMES, April 2013.

David Bowes shows off his latest camless engines at NAMES, April 2013.

Fiat used a similar technology in the 1970s with variable valve timing (VVT), but that involved heavy cams and levers, and proved to be unreliable. In the US, some fine engineers had been working on solenoids, e.g. David Bowes, pictured above with one of his solenoidal engines (he’s a sometime manufacturer for REB Research). Dave has built engines with many cycles that would be impractical without solenoids, and has done particularly nice work reducing the electric use of the solenoid.

Durability may be a problem here too, as there is no other obvious reason that Fiat has not gone completely camless, and has not put a solenoid-controlled valve on the exhaust too. One likely reason Fiat didn’t do this is that solenoidal valves tend to be unreliable at the higher temperatures found in exhaust. If so, perhaps they are unreliable on the intake too. A car operated at 1000-4000 rpm will see on the order of 100,000,000 cycles in 25,000 miles. No solenoid we’ve used has lasted that many cycles, even at low temperatures, but most customers expect their cars to go more than 25,000 miles without needing major engine service.

We use solenoidal pumps in our hydrogen generators too, but increase the operating live by operating the solenoid at only 50 cycles/minute — maximum, rather than 1000- 4000. This should allow our products to work for 10 years at least without needing major service. Performance car customers may be willing to stand for more-frequent service, but the company can’t expect ordinary customers to go back to the days where Fiat stood for “Fix It Again Tony.”