The fact that you can charge a mobile gadget not only from a conventional outlet or on-board network of a car, but also using the energy of fire, water and wind is no longer a secret for many. But how such devices work is a mystery from the category of the “black box” of the TV show “What? Where? When?”. In this article, we will figure out how the charges are arranged, using the energy of fire, water and air in their work.
History and theory of thermoelectricity
Next year, the discovery, which served as the starting point for a whole branch of physics, namely the study of thermoelectric processes, turns 200 years old. In 1821, the German physicist Thomas Johann Seebeck reported to the scientific community about a curious observation. Namely, about the occurrence of a magnetic field and the flow of electric current in a closed system of conductors, when heat or cold is applied to one of the points of the alloy of two metals.
In his experiments, Seebeck used a bismuth plate and a copper plate soldered to it. Between the two plates, the scientist left a gap in which a magnetic needle was placed.
When heat or cold was applied to one of the sides of the structure, the magnetic needle deviated from its original position, which indicated the occurrence of magnetic induction in the copper conductor. If a closed circuit consisting of two metals is opened, then a potential difference arises at its terminals when heated or removed from the junction. The German scientist called his discovery “thermomagnetism”. Later, the physical process of the occurrence of an electromotive force in the junction of conductors when the fusion point is heated was called the Seebeck effect.
In addition to the fact that this discovery gave a powerful impetus to research in the field of thermoelectricity, the Seebeck effect gave humanity a convenient tool for measuring temperatures, namely, thermocouples.
The next important milestone in the study of thermoelectric effects was the discovery of the French scientist Jean-Charles Peltier, made by him in 1834. He continued experiments with various metal junctions, and came to the conclusion that the greatest effect on the production of EMF in the circuit is achieved by using bismuth and antimony, elements with different conductivity (n-conductivity and p-conductivity). The serial connection of these elements with each other by copper jumpers, with strict observance of their alternation, led to the discovery.
Applying voltage to the contacts of such a circuit caused one side of the solderings to become very hot, and the other to rapidly lose heat. Moreover, the greater the voltage value was applied to the outputs of the circuit, the greater the temperature difference was established on the sides of the experimental element.
In fact, this was the second fundamental principle of thermoelectricity, the opposite of the Seebeck effect.
The effect discovered by the French scientist was named after him, and the device created was called the Peltier element.
Modern Peltier elements are produced on the basis of compounds of silicon germanide and bismuth germanide, which makes it possible, when a voltage of the order of 12–14 V is applied to them, to obtain a temperature difference of 80 ° C between the “hot” and “cold” sides, but these are maximum values. On average, Δt is 60°C.
Peltier elements are widely used in refrigeration units, especially in compact automobile refrigerators. The advantages of such a solution clearly include:
low efficiency;
dependence on ambient temperature;
high costs of electrical power to create a temperature difference on the sides of the element.
But the “miracles” do not end there. It turns out that when heat and cold are applied to different sides of the element, an electric current begins to flow through its transitions, and voltage is generated at the terminals. This feature of the Peltier element formed the basis of a whole class of alternative chargers that generate a charge current from simply heating its “hot” side and removing heat from the “cold” one.
How to charge a smartphone with fire
Devices suitable for charging mobile gadgets of this type have a different form factor. They can be made in the form of a mug, a kettle, a brazier or a small portable hearth for burning wood chips. The main thing that unites them is that to start generating electricity, one of the sides of the element needs to be heated.
The magnitude of the charge current directly depends on the temperature difference on the sides of the Peltier element.
To increase the value of the generated current, manufacturers of thermoelectric charges go to a number of tricks:
they are performed in the form of camping utensils (pots, pots, mugs, etc.).
The fire heats one side of the element, while the water effectively cools the other. True, this does not last long – sooner or later the water will boil and the temperature difference will decrease, but at the same time it becomes possible to cook a hearty dinner in the bosom of nature;
small batteries are built into the devices, which continue to charge the smartphone after the temperature difference on the sides of the Peltier element decreases;
equip their chargers with an efficient air cooling system to quickly remove heat from the “cold” side of the cell.
As for the practical side of the issue, the market for such devices is very extensive, starting with the devices of the American company BioLite, which has already made a name for itself, which has in its model range both small camping hearths (from 13,000 rubles),
and barbecues for a large company (from 21,000 rubles),
ending with a rather young start-up of the Tengu charging brazier (from 8,000 rubles) by a Russian engineer from Ufa.
All you need to charge your mobile phone or tablet is to collect a few dry branches or cones and start a fire. Further, the laws of thermoelectricity will do their job, it’s time to connect your smartphone to a USB port and replenish gadget batteries with energy!
How to charge your smartphone with water, wind or muscle power
The idea of obtaining electrical energy from the energy of rotation is not new. Perhaps she was born simultaneously with the invention of electricity. The simple observation that an electric current begins to flow in a conductor coil, when a magnet is brought to it, gave rise to the development and improvement of devices for generating electrical energy.
Generator device
An electrical energy generator is an electrical machine in which the mechanical energy of rotation is transformed into electrical energy.
There are several options for the design of electric generators, but all of them are united by one principle – when a conductor made in the form of a frame interacts with a magnetic field, an electric current begins to flow in it, and a potential difference (voltage) appears at the terminals of the frame. Moreover, the values \u200b\u200bof that voltage, that current strength, directly depend on the frequency of rotation of the conductor in a magnetic field. It is clear that in order to achieve the greatest effect and efficiency, the electric generator of such single frames contains several tens or even hundreds. Together, they form the winding of the generator, in which an electric current is produced.
According to the type of energy generated, electrical machines are divided into direct and alternating current generators. Structurally, alternators are somewhat simpler, since they do not have a collector and brush assembly, and, accordingly, alternating current machines require much less attention and maintenance costs.
It is for this reason that alternators are widely used in compact chargers, but since gadgets require constant voltage and current for their charging, the simplest rectifier and stabilizer are included in the charger circuit.
In industrial and domestic generators, the magnetic field in which the conductor frames are placed creates excitation windings, to which direct current is supplied from an external energy source or a rectified electric current generated by the electrical machine itself (self-excited generators). Such a design is quite difficult to implement on a miniature scale, so compact generators used in chargers are equipped with permanent magnets.
The strength of the magnetic field depends on the type of magnet and its strength, which ultimately affects the magnitude of the generated current. The best representatives of compact generators are equipped with neodymium magnets.
Another important factor responsible for the efficiency of the charger and its ability to generate a sufficient amount of energy is the minimization of energy losses during its conversion. First of all, this concerns mechanical losses from friction that occur during the rotation of the rotor. It is highly desirable that the rotor axis of such a generator be mounted on rolling bearings, and not on brass bushings imitating a plain bearing. Such a design will allow the rotor to start rotating when minimal effort is applied to it, which is especially important in installations operating from a breath of wind or water movement. When generating energy from the flow of water, it is important to ensure the complete tightness of the structure, thereby eliminating even a hint of moisture getting inside the device.
The charging device powered by water or wind energy is similar. An impeller is put on the shaft of the generator rotor, which is set in motion by flows of one or another element passing through its blades.
When used to generate muscle strength, a step-up gearbox is added to the design of the device, which allows you to get a sufficient number of revolutions on the generator shaft, which is necessary to generate electricity of the specified parameters. In this case, the handle of the charger does not have to be rotated with fanaticism.
Approximately three minutes of turning the mechanical charging handle will give you one minute of talk time, which can be crucial in an emergency.
As for practical application, chargers built on an electrical energy generator are perhaps the most common category of camping chargers. Starting from the most common bicycle dynamos (from 500 rubles)
and mechanical chargers (from 400 rubles),
to micro hydroelectric power plants that use the energy of the flow of a stream or river in their work. To charge your smartphone with such charging, you will need to find a place on the shore where there is at least a small but steady movement of water. Water flowing through the blades will rotate the generator shaft, charging the internal battery. Devices of this kind are indispensable in traveling on the water surface, from a leisurely trip on a raft to extreme rafting on a mountain river. When traveling, when conditions permit, the charger turbine should always be left overboard of the craft, using every opportunity to store energy.
The cost of such a universal impeller starts from 18,000 rubles. The “feature” of a particular model (produced in Canada, by the way) is omnivorous, it successfully works both from the flow of water or air currents, and from the muscular strength of the traveler.
Synergy of substances and elements
You can charge a mobile phone not only with fire, water or wind taken separately, but also with a combination of several external influences at once. You can also enlist the help of other structures and substances.
Chemical substances
Prominent representatives of this family of chargers are chemical fuel cells that generate electricity due to certain chemical reactions occurring in them. The main essence of these processes is a chemical reaction, the reverse of the process of electrolysis (the decomposition of water into hydrogen and oxygen when an electric current is applied to it). In compact fuel cells, instead of classical hydrogen, which has not yet been learned how to produce cheaply, methyl alcohol is used, which contains a sufficient amount of hydrogen in its composition.
As a result, during the interaction of hydrogen and oxygen contained in the air, in an electrolyte enclosed in a proton-exchange membrane that does not release negatively charged particles beyond its limits, free electrons arise, which, moving along the conductor, create an electric current in it.
The main “feature” of a chemical fuel cell is its incredibly high efficiency and the absence of any harmful emissions. The output is pure energy and a few drops of water.
The only thing that strongly hinders the development of this technology is the understanding that methanol is poisonous and its widespread use can be fraught. An additional factor preventing the development of such fuel cells is their high cost. Indeed, expensive gold and platinum are used as catalysts on the cathode and anode of the installation.
Another pair of chemical elements, namely magnesium and carbon (coal), also has a good potential. Placing two electrodes from these elements in a container of water gives a voltage of about 2 V at their terminals.
Chargers powered by chemical fuel cells were actively promoted and sold in 2013-2014. Today they are no longer available for sale. Apparently the technology did not justify itself, or appeared prematurely.
Fire and Water
In one children’s logic game there is a question: “What will happen if you combine fire and water?”. The correct answer is “Steam”, and this, for a moment, is one of the first movers that stood at the dawn of widespread electrification. It was steam engines that set in motion the first electric generators. Therefore, many will surely like the steampunk steam engine on their desktop.
The principle of its operation is quite simple: the water in the boiler boils and turns into a gaseous state – steam, which in turn pushes the piston of the cylinder that drives the flywheel. By attaching a generator shaft to it, we get a working model that generates electricity. Yes, it will have a weak efficiency, you won’t take it with you on a hike, but once you are in a place where “stationary” electricity has not yet reached, it will definitely work to charge a smartphone or light a small light bulb.
A steam engine is a pressure vessel! It must be handled with extreme care, in compliance with all necessary safety measures!
fire and air
Another curious device that allows you to get the energy of movement from heating the air is the Stirling engine.
The authorship of this design belongs to the Scottish priest Robert Stirling, who patented his invention in 1816.
The principle of operation of the installation is outrageously simple. The engine works solely due to the temperature difference of the working fluid enclosed in the cylinder. The Stirling engine uses air as the working fluid.
To start a Stirling engine, it is enough to heat the air in the “hot” part of the cylinder for 20–30 seconds. The air heated on one side of the cylinder expands and pushes the working piston, after which it cools down in the regenerator, compresses and pulls the piston back. The displacement piston is responsible for the rapid movement of air in the cylinder from the hot side to the cold side and vice versa.
This cycle continues as long as the temperature difference between its sides is maintained in the working cylinder. The engine stops when the air temperatures in both parts of the cylinder equalize.
To ensure the operability of the structure, it is important that two conditions are met:
The working and displacement pistons must be attached to the flywheel with a certain shift (as a rule, a circular shift is 90 °);
The displacement piston, unlike the working one, should not fit tightly against the walls of the cylinder, ensuring the free movement of the working fluid from the hot to the cold part of the chamber and vice versa.
Further – a matter of technology, we connect a generator to the flywheel shaft and collect the much-needed energy.
The advantages of this design include:
omnivorous. It absolutely does not matter what kind of fuel to heat or cool part of the working cylinder;
simplicity of design. A minimum of parts and a simple assembly scheme makes this type of engine extremely efficient, having simply a huge working resource;
economy. It doesn’t take much energy to create a temperature difference. The working fluid (air) is not consumed at all;
environmental friendliness. The Stirling engine does not emit exhaust gases into the atmosphere, does not create increased levels of noise and vibration during its operation.
The disadvantages of this design include:
the impossibility of removing high power from the motor shaft;
the complexity of regulating the operating mode and the speed of rotation of the flywheel;
inertia of the system;
large dimensions and material consumption. To obtain more or less adequate power levels, the size of the cylinder must be impressive, and the manufacture of the walls of the regenerator necessary for cooling the working fluid requires a large amount of metal.
What a steam engine
that the Stirling engine
are not “exclusive”. Commercial copies can be easily bought at local online stores that specialize in the sale of demonstration and educational models, or ordered directly from the Middle Kingdom. Most of them are made there anyway.
The only thing is that it will not work out of the box to charge the phone with models of these engines, they will need to be finalized in terms of installing a generator with the necessary output parameters. In general, a task for real enthusiasts who are not afraid to pick up a tool.
A steam engine model will cost from 15,000 rubles, and a small Stirling engine from 2,500 rubles. The cost of models that can be upgraded for the needs of charging mobile gadgets starts from 4500 rubles.
Results
Of course, all of these devices today are quite exotic and still not very common in everyday life, but the principles embedded in them have great potential in the field of energy production from alternative sources. Therefore, only one thing can be said unequivocally, being away from an electrical outlet and having at least one of these devices in your arsenal – it will not be difficult to get some energy for lighting or charging a smartphone.
