Earth Batteries and Joule Thieves
An Earth battery is a pair of electrodes made of two dissimilar metals, such as iron and copper, which are buried in the soil or immersed in the sea. Earth batteries act as water activated batteries and if the plates are sufficiently far apart, they can tap telluric currents. Earth batteries are sometimes referred to as Telluric power sources and Telluric generators.
One of the earliest examples of an earth battery was built by Alexander Bain in 1841. Bain buried plates of zinc and copper in the ground about one meter apart and used the resulting voltage, of about one volt, to operate a clock. Carl Friedrich Gauss, who had researched Earth’s magnetic field, and Karl A. von Steinheil, who built one of the first electric clocks and developed the idea of an “Earth return” or “ground return”, had previously investigated such devices.
The simplest earth batteries consist of conductive plates from different locations in the electropotential series, buried in the ground so that the soil acts as the electrolyte in a voltaic cell. As such, the device acts as a non-rechargeable battery. When operated only as electrolytic devices, the devices were not continuously reliable, owing to drought condition. These devices were used by early experimenters as energy sources for telegraphy. However, in the process of installing long telegraph wires, engineers discovered that there were electrical potential differences between most pairs of telegraph stations, resulting from natural electrical currents (called telluric currents) flowing through the ground. Some early experimenters did recognize that these currents were, in fact, partly responsible for extending the earth batteries’ high outputs and long lifetimes. Later, experimenters would utilize these currents alone and, in these systems, the plates became polarized.
It had been long known that continuous electric currents flowed through the solid and liquid portions of the Earth, and the collection of current from an electrically conductive medium in the absence of electrochemical changes (and in the absence of a thermoelectric junction) was established by Lord Kelvin.Lord Kelvin’s “sea battery” was not a chemical battery. Lord Kelvin observed that such variables as placement of the electrodes in the magnetic field and the direction of the medium’s flow affected the current output of his device. Such variables do not affect battery operation. When metal plates are immersed in a liquid medium, energy can be obtained and generated, including (but not limited to) methods known via magneto-hydrodynamic generators. In the various experiments by Lord Kelvin, metal plates were symmetrically perpendicular to the direction of the medium’s flow and were carefully placed with respect to a magnetic field which differentially deflected electrons from the flowing stream. The electrodes can be asymmetrically oriented with respect to the source of energy, though.
To obtain the natural electricity, experimenters would thrust two metal plates into the ground at a certain distance from each other in the direction of a magnetic meridian, or astronomical meridian. The stronger currents flow from south to north. This phenomenon possesses a considerable uniformity of current strength and voltage. As the Earth currents flow from south to north, electrodes are positioned, beginning in the south and ending in the north, to increase the voltage at as large a distance as possible.In many early implementations, the cost was prohibitive because of an over-reliance on extreme spacing between electrodes.
It has been found that all the common metals behave relatively similarly. The two spaced electrodes, having a load in an external circuit connected between them, are disposed in an electrical medium, and energy is imparted to the medium in such manner that “free electrons” in the medium are excited. The free electrons then flow into one electrode to a greater degree than in the other electrode, thereby causing electric current to flow in the external circuit through the load. The current flows from that plate whose position in the electropotential series is near the negative end (such as palladium). The current produced is highest when the two metals are most widely separated from each other in the electropotential series, and when the material nearer the positive end is to the north, while that at the negative end is towards the south. The plates, one copper and another iron or carbon, are connected above ground by means of a wire with as little resistance as possible. In such an arrangement, the electrodes are not appreciably chemically corroded, even when they are in earth saturated with water, and are connected together by a wire for a long time.
It had been found that to strengthen the current, it was most advantageous to drive the northerly electropositive electrode deeper into the medium than the southerly electrode. The greatest currents and voltages were obtained when the difference in depth was such that a line joining the two electrodes was in the direction of the magnetic dip, or magnetic inclination. When the previous methods were combined, the current was tapped and utilized in any well-known manner.
In some cases, a pair of plates with differing electrical properties, and with suitable protective coatings, were buried below the ground. A protective or other coating covered each entire plate. A copper plate could be coated with powdered coke, a processed carbonaceous material. To a zinc plate, a layer of felt could be applied. To use the natural electricity, earth batteries fed electromagnets, the load, that were part of a motor mechanism.
The Baghdad Battery, sometimes referred to as the Parthian Battery, is the common name for a number of artifacts created in Mesopotamia, during the dynasties of Parthian or Sassanid period (the early centuries AD), and probably discovered in 1936 in the village of Khuyut Rabbou’a, near Baghdad, Iraq. These artifacts came to wider attention in 1938 when Wilhelm König, the German director of the National Museum of Iraq, found the objects in the museum’s collections. In 1940, König published a paper speculating that they may have been galvanic cells, perhaps used for electroplating gold onto silver objects. Though far from settled, this interpretation continues to be considered as at least a hypothetical possibility.If correct, the artifacts would predate Alessandro Volta’s 1800 invention of the electrochemical cell by more than a millennium. The artifacts consist of terracotta pots approximately 130 mm (5 in) tall (with a one-and-a-half-inch mouth) containing a copper cylinder made of a rolled-up copper sheet, which houses a single iron or (galvanized nail) rod. At the top, the iron rod is isolated from the copper by bitumen plugs or stoppers, and both rod and cylinder fit snugly inside the opening of the jar, which bulges outward toward the middle. The copper cylinder is not watertight, so if the jar was filled with a liquid, this would surround the iron rod as well. The artifact had been exposed to the weather and had suffered corrosion, although mild given the presence of an electrochemical couple. This has led some to believe that wine, lemon juice, grape juice, or vinegar was used as an acidic electrolyte solution to generate an electric current from the difference between the electrochemical potentials of the copper and iron electrodes. König thought the objects might date to the Parthian period (between 250 BC and AD 224). However, according to St John Simpson of the Near Eastern department of the British Museum, their original excavation and context were not well-recorded (see stratigraphy), so evidence for this date range is very weak. Furthermore, the style of the pottery is Sassanid (224-640).
“Joule thief” is a nickname for a minimalist self-oscillating voltage booster that is small, low-cost, and easy-to-build; typically used for driving light loads. It can use nearly all of the energy in a single-cell electric battery, even far below the voltage where other circuits consider the battery fully discharged (or “dead”). Hence the name suggests the notion that the circuit is stealing energy or “Joules” from the source. The term is a pun on the expression “jewel thief”, one who steals jewelry or gemstones.
The circuit uses the self-oscillating properties of the blocking oscillator, to form an unregulated voltage boost converter. As with all power conversion technology, no energy is actually created by the circuit. Instead, the output voltage is increased at the expense of higher current draw on the input. As a result, the amount of power entering the circuit is the same as the amount leaving, minus the losses in the conversion process.
The circuit works by rapidly switching the transistor. Initially, current enters the transistor base terminal (through the resistor and secondary winding), causing it to begin conducting collector current through the primary winding. This induces a voltage in the secondary winding (positive, because of the winding polarity, see dot convention) which turns the transistor on harder. This self-stoking/positive-feedback process almost instantly turns the transistor on as hard as possible (putting it in the saturation region), making the collector-emitter path look like essentially a closed switch (since VCE will be only about 0.1 volts, assuming that the base current is high enough). With the primary winding effectively across the battery, the current increases at a rate proportional to the supply voltage divided by the inductance. Switch-off of the transistor takes place by different mechanisms dependent upon supply voltage.
The predominant mode of operation relies on the non-linearity of the inductor (this does not apply to air core coils). As the current ramps up it reaches a point, dependent upon the material and geometry of the core, where the ferrite saturates (the core may be made of material other than ferrite). The resulting magnetic field stops increasing and the current in the secondary winding is lost, depriving the transistor of base drive and the transistor starts to turn off. The magnetic field starts to collapse, driving current in the coil into the light emitting diode (raising the voltage until conduction occurs) and the reducing magnetic field induces a reverse current in the secondary, turning the transistor hard off.
At lower supply voltages a different mode of operation takes over: The gain of a transistor is not linear with VCE. At low supply voltages (typically 0.75v and below) the transistor requires a larger base current to maintain saturation as the collector current increases. Hence, when it reaches a critical collector current, the base drive available becomes insufficient and the transistor starts to pinch off and the previously described positive feedback action occurs turning it hard off.
To summarize, once the current in the coils stops increasing for any reason, the transistor goes into the cutoff region (and opens the collector-emitter “switch”). The magnetic field collapses, inducing however much voltage is necessary to make the load conduct, or for the secondary-winding current to find some other path.
When the field is back to zero, the whole sequence repeats; with the battery ramping-up the primary-winding current until the transistor switches on.
If the load on the circuit is very small the rate of rise and ultimate voltage at the collector is limited only by stray capacitances, and may rise to more than 100 times the supply voltage. For this reason, it is imperative that a load is always connected so that the transistor is not damaged. Note that, because VCE is mirrored back to the secondary, failure of the transistor due to a small load will occur through the reverse VBE limit for the transistor being exceeded (this occurs at a much lower value than VCEmax).
The transistor dissipates very little energy, even at high oscillating frequencies, because it spends most of its time in the fully on or fully off state, thus minimizing the switching losses.
The switching frequency in the example circuit opposite is about 50 kHz. The light-emitting diode will blink at this rate, but the persistence of the human eye means that this will not be noticed.
When a more constant output voltage is desired, a voltage regulator can be added to the output.
Joule Thieves can be used with Fuji Circuits (flash circuit board from disposable fuji cameras) to really ramp up the power!
Capacitors can be used to store up and release the telluric energy collected by an earth battery. Using capacitors and a Fuji Circuit it is possible to get an earth battery to provide short periods of high power load. Joule Thieves and Fuji Circuits are also used to draw current from low output batteries