Tag Archives: energy

Measuring Telluric Currents – First Trial

Way back in November of last year (2010), I wrote a short little article on telluric currents, their history, and related applications.  Now, in case you’re unfamiliar with this topic (as I was prior to November of last year), here’s the executive summary: telluric, or earth currents, are electrical currents which travel through ground or water, primarily near the surface of the earth.  They may be naturally occurring (due to changes in the earth’s magnetic field via solar wind), or man-made (e.g, from mineral exploration).

Well towards the end of my previous post, I expressed a desire to try and measure these currents.  Unfortunately at that time, it was winter, and I was in the process of relocating to Iowa.  But now that I’ve settled in here, and the ground has finally thawed, I’ve gone out and performed a quick first measurement.  Here’s the procedure I followed:

  1. Obtain two 36″ lengths of standard rebar and 100′ of insulated 14 AWG copper wire (solid core works, but I used stranded for better contact with the rebar).
  2. Sand/file any rust from the surface of the rebar (to reduce contact resistance).
  3. Strip about two inches of insulation from the ends of the wire, then fray these ends and wrap them tightly around one end of each piece of rebar.  Cover these attachment areas with electrical tape.
  4. Cut the wire, which is now linking the two pieces of rebar, at any point (this is where the multimeter will be inserted).
  5. Space the two lengths of rebar as far apart horizontally as possible, then drive them into the ground as deeply as possible (in my case, this was about 20″).  For my first test, I configured the two so that they would point north to south based on the map shown here and my location in Iowa).  In other words, if I were to stand at the southern-most length of rebar, facing the other rod, I would be facing north.  They were separated by the 100′ of wire.
  6. Measure both current (short circuit) and voltage (open circuit).
  7. Finally, if anyone should question what the @#$% you’re doing pounding rebar into the ground, simple employ this catch-all excuse: “solar flare protection.

So, without further ado, I give you my results (in low-quality cellphone pic format):

Telluric Current - Well, it is measurable...

If you can’t quite make out that reading, my apologies.  The meter indicates 0.55mA (DC).  Yea, not too incredible, I know.  I also measured the voltage between the two rebar rods, but at just 105mV, it’s not terribly impressive either.  So, at best, we’ve got 14.5uW of power to play with – barely enough to run a digital watch (please see this excellent page on Thevenin equivalent circuits and the maximum power theorem for details on how that number was calculated).

Overall, these results are a little disappointing, both in quality and in quantity.  I had hoped to reconfigure my rods a couple of times so as to measure the current’s heading as well.  Unfortunately, for this test I picked a slightly wooded area that also happened to be teeming with mosquitoes.  I’ll do a lot of things for the sake of science, but serving as a meal for blood-sucking insects isn’t one of those things.

In the future, I’d like to leave the rebar in place for a while longer – say, 24 hours – and record data continuously during that time.  I’ve read in a number of sources that telluric currents tend to vary over the course of a day.  So, when I did my test this morning (8:30AM CST), I may have been measuring things as a low point.  The only trouble with capturing data for such an extended length of time is that I’ll need to find a more controllable location, and I’ll need to figure out how to log the data automatically.  I’ve got a few development boards I can probably re-purpose for that though…

So, in summary, for round two of testing I shall make the following changes:

  • Take measurements with the rods configured along different compass headings.
  • Log data for a consecutive period of at least 24 hours.

If anyone has other suggestions, please leave a comment.  Stay tuned for more.  Thanks!

Plasma for Waste Disposal?

Plasma.  You’ve probably heard of it before (and hopefully somewhere outside of Best Buy).  It is the fourth state of matter (the first three being solid, liquid, and gas), in which molecules have been split apart into their most basic atomic form and ionized.  Accomplishing this splitting, or disassociation, requires huge amounts of energy.  So it’s not surprising that plasma plays a key role in a number of high-power applications including plasma cutters and fusion reactors.  Again, you’ve probably heard of those.  But I’ll bet you’ve never heard of dental plasma torches or plasma arc waste disposal.

Plasma Torch (Courtesy PyroGenesis via HSW)

So what’s the deal here?  Using plasma for waste disposal?  Sounds like overkill.  I mean, vaporizing trash with a torch that reaches temperatures of 25,000°F?  That’s more than twice the temperature at the surface of the sun.  Well, there actually are advantages to this.  For one thing, plasma torches can break down almost any material into its constituent atoms.  Plastics, metals, toxic compounds, medical waste, apple juice – basically anything except heavy radioactive materials (such as spent nuclear fuel rods) can be converted into gasses and slag (molten solid waste, shown below):

Plasma Furnace Slag Drain (Courtesy PyroGenesis via HSW)

As an added bonus, with plasma arc waste disposal, the byproduct gasses can actually be used as fuel.  In fact, these plasma converters, as they’re called, can generate more energy than they require for operation.  In other words, they convert waste into energy, similar to an old-fashioned incinerator.  But unlike incinerators, which burn waste in the presence of oxygen, plasma arc furnaces break apart waste using a process called pyrolysis, which can be done in an airtight container.  The result?  Fewer hazardous byproducts.

Anyway, I’ll stop here and refer you to HowStuffWorks for further information.  They’ve produced an excellent article on plasma converters which goes into more detail on how these systems work and where they’re currently being designed and used.

In other news, yes, this is my first post in three weeks.  My apologies for being so lazy, but I’ve been a little busy with moving from Troy, NY to Waterloo, IA for my new job with John Deere.  I’ve just wrapped up my second week of work and it’s been pretty exciting so far.  During my first week of orientation I toured a different Deere facility each day.  I saw some pretty amazing things there, including electrostatic painting robots, inductive heat treatment, and some pretty hefty robotic welding stations.  Perhaps in the future I’ll be able to write about some of these things (although the details of a lot of these systems are confidential).  Anyway, to my subscribers, thanks for sticking around!

Telluric Currents and the Earth Battery

(So it turns out I can pack boxes faster than expected!  Unfortunately that means I’m now just killing time until tomorrow when I load everything into the truck and head off for my new job in Waterloo, Iowa.  But here’s another article, just for you!  I know, I know, it’s not a project or a circuit, but I left my electronics stuff in St. Louis…)

You know what?  The Discovery Channel is right, the world is just awesome.

The other day I was surfing Wikipedia and happened across an article on telluric currents.  Apparently, changes in our planet’s magnetic field induce fairly substantial currents into the surface of the earth (both across lands and oceans).  Now, I’ve heard of the earth’s magnetic field, and I’m familiar with grounding rods acting as current paths.  But telluric currents?  Well, like 99.9% of all Wikipedia articles, it’s new to me.

Global Map of Telluric Currents, Created 1936 - This is likely no longer very accurate by today's standards.  Understandably, collecting such data wasn't so easy in 1936, so a lot of this map came from interpolation.

So what’s the deal with these mysterious earth currents?  Well believe it or not, this is a phenomenon which was first observed way back in the mid-1800s.  In fact, it used to wreak havoc with telegraph and, later, telephone lines.  You see, electrical currents tend to follow the path of least resistance.  So if there happens to be a wire connected between two points on the earth’s surface (e.g. a communications ground line), any current that might normally have flowed through the earth itself will instead flow along the lower-resistance wire.  For example, according to The Earth’s Electrical Environment (Pg. 244), between August 28th and september 2nd, 1859, an enormous geomagnetic storm induced 800V on a 600km wire in France.  Much later, on March 24, 1940, a similar event damaged two communications sites in Tromso, Norway:

“Sparks and permanent arcs were formed in the coupling racks and watch had to be kept during the night to prevent fire breaking out… One line was connected to earth through a 2mm thick copper wire, which at once got red hot, corresponding to a current more than 10amps.”

Now telluric currents aren’t all bad.  In fact, they’ve recently been used to map and explore underground structure.  By taking measurements of voltage and current along an array of points at the earth’s surface, scientists can characterize the conductivity of different areas of the ground.  This method can even be used to identify mineral or petroleum deposits.  For more details on this, see this article on Magnetotellurics.

An example of data produced using the methods of Magnetotellurics

Well as you may have guessed, naturally-occuring telluric currents can even be harnessed to provide electrical power.  Of course, this requires a wire of substantial length.  And this point, combined with the fact that there’s not much energy to be drawn from most telluric currents anyway, makes this an impractical power source.  However, there is one related invention which at least solves the length issue: the earth battery.  Basically, the earth battery works just like any other chemical battery – you insert two electrodes made of different metals into the ground, and the earth acts as your electrolyte.  The ground needs to be slightly wet for this to really work properly.   But with such close spacing, you’re not really deriving energy from the earth’s magnetic field, you’re just making a simple chemical battery (like that potato battery you made in elementary school).  However, earth batteries did work well enough to power some early telegraph stations.  If you’re curious, here’s the patent for an improved earth battery, issued in 1874.

By the way, in researching for this article, I ran across a (seemingly) amazing “patent” for a device that claims to be able to produce 3000W of electrical power from a 500W input.   It says this can be accomplished through a simple high-frequency oscillator and a half-mile antenna which derives energy through resonance with telluric energy.  Now, I’ll let you come to your own conclusions, but I think this is bunk.  For one thing, US Patent #253,765 is for a portable fence, not an electrical power accumulator (and I couldn’t find this “patent” via term searches).   But secondly, how could telluric currents possibly resonate at 500kHz?  Everything I’ve read describes naturally-occuring telluric currents as having periods on the order of, at shortest, minutes.  Which means we’re talking about frequencies in the millihertz, not kilohertz.  In fact, most telluric current oscillations are diurnal, meaning they follow a daily, 24-hour cycle.  Oh and third, the rest of the website hosting that “patent” is unbelievably sketchy…

Anyway, if you’re curious, take a read through this chapter, available for free online, and tell me what you think.   I’d absolutely love to try this out sometime.  Anyone have any suggestions for how to do it?  I’m thinking of just buying the cheapest, longest length of wire I can get from Home Depot, along with a couple of pieces of re-bar.  Then I’ll just go find a field somewhere, set my two electrodes pointing north and south (as that seems to be the predominant direction of telluric current flow in the US), then check it with a voltmeter.  Perhaps nobody would mind if I tried this at a park someplace… 🙂

Unique Energy Storage

What do you think poses the greatest challenge for technological advancement today?

Well if you were to ask me, I’d say energy – both its creation and storage.  This may be obvious, but without sufficient energy, manufacturing, research, and educational facilities won’t be accomplishing much.  But even if scientists were to find a source of limitless, cheap energy, if it’s not portable, there’s still a problem.  For instance, what’s holding back the advancement of electric cars?  The cost and weight of batteries.  Why aren’t solar and wind energy more widely accepted?  Admittedly, cost is a big factor, but renewable sources like these operate on their own timeline.  Clearly, we can’t rely on solar power at night, so we need a means of storing up that energy during the day.

Now sadly, I don’t have a solution to either of these problems.  If I did, I wouldn’t be blogging, I’d be swimming in my money bin a la Scrooge McDuck.  Fortunately, there are researchers working on both energy creation and storage.  In this post, I’d like to mention just a few of the more interesting techniques, past and present, for the storage of energy.

Ultracapacitors

Alright, I’ve got to mention this one first, since it comes from my alma mater.  Researchers at Rensselaer Polytechnic Institute (RPI) have just received $2 million from the National Science Foundation (NSF) to help develop new ceramic materials for energy storage.

Maxwell Ultracaps

Now supercapacitors such as those pictured above, have been around for a number of years.  However, they’re still very expensive and although they offer impressive power densities (i.e. the ability to charge and discharge rapidly), they can’t match the energy density (the quantity of energy stored per unit volume) of batteries.

Fortunately, this new research into nanostructured capacitors may yield better results.  According to Doug Chrisey, a professor in RPI’s materials science department (one place I rarely dared to visit as a student), these new capacitors will be smaller, lighter, and more efficient than batteries.  How will this be accomplished?  By constructing a capacitor from extremely thin layers composed of “a mix of ferroelectric nanopowder and low-melting, alkali-free glass.”  Sounds intriguing…  Sadly, it’ll be years before the results of this research are known and available to consumers.

Antimatter

Now here’s an approach to energy storage that’s even further off into the future.  It may also be completely impractical.  Nevertheless, it’s still really cool.  See, when matter and antimatter collide, they release an extraordinary quantity of energy – approximately 10,000 times the energy produced by nuclear fission.  Yea, wow indeed.

Visual Approximation of a Matter-Antimatter Collision

So the idea here is to produce a bit of antimatter, store it as fuel, and then use it as needed.  You’d only need to store a few nanograms of antimatter to power your Tesla Roadster.  The trouble comes in production.  It’s expensive.  And slow.  Not to mention difficult to store.  Extrapolating from data on the 2004 production of antiprotons at CERN, to obtain just one gram of antimatter would require $100 quadrillion and 100 billion years.  And despite the vast amounts of energy invested in antimatter production thus far, the sum of all antimatter ever created would only provide enough energy to light a bulb for a few minutes.  Better luck next century guys.

Flywheels

When you think of a flywheel, you probably picture a heavy metal disc of some sort (I think there might be a joke in there someplace).  At first glance, it doesn’t seem like much of an energy storage device.  But you’d be wrong about that.  With enough speed and inertia, flywheels can store over 100kWh as rotational kinetic energy.  They can also be “charged” and “discharged” quite rapidly (on the order of minutes).  Here’s one example which stores roughly 500Wh and can source up to 1kW, the NASA G2 flywheel:

NASA's G2 Flywheel

To reduce frictional losses in the G2, the flywheel itself is suspended within a vacuum on magnetic bearings.  It can be rotated at up to 60,000RPM.  In terms of energy and power density, flywheels can actually out-perform most batteries.  The problem?  Cost, as usual.

Now the “charging” of such a device is performed by powering a motor which spins up the flywheel.  To “discharge” the flywheel, a generator (which could be the same motor used in spin-up) is used to convert that stored rotational energy back into electricity.

One interesting application of flywheel energy storage is the Incredible Hulk roller coaster at Universal in Orlando, FL.  In order to power the coaster’s initial uphill launch, the ride uses several motor-generator sets attached to large flywheels to store and release enormous amounts of energy.  Without these flywheels to provide this initial boost of power, Universal would have needed to build an entirely new electrical substation (or risk brownouts every time the ride launched).

Flywheels have also been used to provide energy for vehicles, such as the Gyrobus, as early as the 1940s.  Prototype charging stops were installed in Switzerland in the early 1950s, but the idea never really caught on.  Gyrobusses were limited to distances of about 6km at speeds of up to 60km/h.  They also had issues with gyroscopic forces tending to tip the vehicles.  However, research is still proceeding on flywheels for use in electric trains.  A 133kWh flywheel developed at UT Austin can accelerate an electric locomotive from rest all the way up to cruising speed.

One final interesting note.  I haven’t been able to confirm this, but I’ve heard that a large flywheel, used to provide pulse power to a particle accelerator, once failed catastrophically (i.e. exploded).  The resultant shockwave was detected hundreds of miles away on seismographs.  This is one problem you won’t have to worry about with supercaps…

Anyway, I’d love to hear your thoughts on energy storage and production, so feel free to leave a comment below.  Thanks!