6 ways to generate electricity
1. STATIC
The first type of electricity subjected to study was of a static nature. It is the type Thales of Miletus talks about, and scientists of the 17th century used to entertain salons. After a glass rod was rubbed with silk cloth, it could attract feathers and lift them off the table. The Mayor of the German Town of Magdenburg Otto von Guericke, already famed for his study of the vacuum by performing the Magdeburg hemispheres experiment, made the first attempt to build a machine that could produce static electricity, the sulphur globe. A sulphur ball was made by poring liquid sulphur in a glass sphere, after which the glass was broken and removed, and the remaining ball placed in a wooden frame with handle to spin it.
Others discovered later that the glass sphere itself could perform the same task. Francis Hauksbee, assistant and instrument maker to the great Isaac Newton, perfected the design in the early 18th century, and built the static electricity generator that became the consumer standard: the Hauksbee machine. Though intended as a scientific instrument, it acquired its true fame in salons and on fairgrounds. Scientist-showmen could now generate enough static electricity to charge human beings. One famous act consisted of suspending a boy from the ceiling, asking him to hold one hand above some brass flakes, while the other touched the electric generator. To the amassment of the audience the hand would lift up the brass flakes which then stuck to the boy. Another feat was the electric kiss: a young lady would be placed on a wooden step in front of the generator. After her hand had touched the machine, men who kissed her would physically feel the spark. Or a host would charge himself up, and through a spark would light up a glass of cognac. Although very spectacular, static electricity was of a fleeting kind. One moment it was there, the moment you touched it was gone.
Many theories were put forward. The most sustainable one probably comes from Benjamin Franklin, book publisher and later founding father of nothing less than the United States of America. He had a profound interest in science, and more specifically electricity. After attending a lecture in Boston in 1743, Franklin shipped over every experimental instrument he heard off, from the glass rod to the Hauksbee Machine, and started experimenting himself. His greatest contribution to the study of electricity is probably the notion that
electricity is not added to a surface, but rather something that is always there,
it is just un-balanced by certain acts. An object could have too much or too little electricity. As a faithful bookkeeper, Franklin referred to the states of an object as positive or negative. And the flow between the two as current.
Humans do not perceive static electricity below 1500 volt, but certain electrical parts do. So when you unconsciously charged yourself up, for instance by rubbing your feet over certain carpets, which can give you up to 12,000 Volts, you might damage electrical parts without even noticing, or throw a spark when you kiss your loved ones.
2. CHEMICAL
Although now mainly known as a device to store electricity, the battery as invented by Alessandro Volta in 1800 was actually a source of electrochemical energy. Volta had discovered that different metals combined provoked a sensation similar to static electricity. He built an experiment consisting of
a pile of alternating copper and zinc disks, separated by paper drained in acid.
On the wires connecting both ends of the pile, constant current could be observed. The experiment was called the voltaic pile, and formed the basis of most current forms of batteries.
Chemical energy is also produced by cells in the human body. Certain cells, called excitable cells can produce a small electrical charge which is referred to as a nerve impulse. They form the subject of advanced study in fields like neuroscience, but as of yet there are no examples of harvesting its energy.
3 MAGNETIC
Magnetism and electricity have long gone hand in hand. Both attracted lighter objects for inexplicable reasons. The relationship was abandoned as the discovery of electricity progressed. Until the Dane Christian Oersted in 1820 noticed how a compass needle deflected from magnetic north when electric current passed through a nearby wire. Soon after, Michael Faraday built on this discovery to design his electromagnetic rotation experiment. He filled a glass with mercury, placed a magnet inside it, and hung a copper wire from above that dangled in it. Then he wired up the copper wire and the mercury to a power supply. When current runs through the wires, the copper wire starts circling around the magnet. It was the first electric motor,
in the sense that it transformed electrical energy into motion.
Now Faraday wondered if it would also work the other way round: could motion be transformed into electrical energy. In 1831, he succeeded in what he called electromagnetic induction. He wrapped wire around a tube to form a coil, and then moved a magnetic bar through the coil. This provoked a slight electric current in the coil.
He perfected his experiment in an instrument he called the homopolar generator, but which would become known as the Faraday disk. A conducted copper disk was placed in a magnetic field. When the disk was turned, a stream of current was generated from the difference between the centre and the edge of the disk. Although far from perfect, the Faraday disk was a proof of principle that would inspire others to built the dynamo and the generators that produce most of the electricity on the grid. Apart from solar energy, most other sources of power use electromagnetic machines to transform heat into electricity. Coal, gas as well as nuclear power stations drive turbines that make coils spin in a magnetic field and so produce electricity.
4. PIEZO-ELECTRIC
Around 1880 Jacques and his younger brother Pierre Curie discovered the relationship between the crystal build-up of materials, and its ability to
create an electrical charge under mechanical stress.
They showed how compressing quartz, sugar cane, topaz and Rochelle salt generated an electric charge, and that quartz and Rochelle Salt (a lab-made salt) were best able to do so. Practical applications remained limited to and shielded of by the military industry. Until post-war Japan started its post-war technological boom. They produced buzzers where the push of the button created a current, and famously also piezo-electric igniters in which the push of a button generates a spark. Now built in in almost every gas cooker, the piezo-electric lighter became famous in the 1930s as an automobile electric cigarette lighter. By pressing the lighter a spark was created which lit a gas inside the lighter. No wiring was required at the time. Currently running shoes linked to an electronic device (be they for measuring your distance or for lighting up your soles red and green) often contain piezo-electric patches, and energy harvesting devices like floor tiles that can recuperate the mechanical energy of pedestrians or revellers on a dance floor also rely on piezo-electronics.
Another use of the piezo-electric effect, is in quartz clocks. Quartz generates electricity when compressed, but reversely it also bends when electronic current is applied to it. Because the signal or oscillation it produces is not effected by temperature or movement, quartz is often used as a time keeping device. Hence the quartz watch.
Automobiles no longer use a piezo-electric cigarette lighter. They kept the plug and often even its characteristic shape, however, but get power straight form the 12 Volt battery in the car, making the cigarette lighter actually actually a plug. Many 12 Volt devices have been built to be charged via this plug. However, mobile phones run on 5 volts so conversion needs to take place before you can plug them in.
5. THERMAL
In the 19th century Seebeck and Peltier experimented separately from each other with the observation that a difference in temperature can produce a potential difference and so electric current. The Seebeck effect describes how temperature differences translate directly into electricity; while Peltier looked more at the heat that emerges or disappears at a junction of two currents.
The Seebeck effect is a small device that translates heat in into current.
Used in the gas industry and to power space probes, it is only recently used in the car industry to harvest waste heat. The Peltier effect is used in small refrigerators that have no moving parts or fluids. Increasingly, the thermoelectric effect is increasingly used as a form of energy recycling, in which waste heat is converted in electric power. Finally, the thermocouple is a device based on the Seebeck effect, and which measure the voltage difference between two conductors, and allows so to measure temperature very accurately.
6. OPTICAL
Edmond Becquerel discovered in 1839 that platinum or gold plates
unevenly exposed to sunlight produced an electric current.
The phenomenon remained largely unnoticed, because practically unusable. It was only in 1954 that the first practical solar cells were produced at Bell Labs in New Jersey. They called it a great possibility for telephone services. (There is that mobile phone again!) Solar panels gained fame when they were used to power satellites in the 1960s. Improved efficiency, reduced cost, environmental concerns but also rising cost of other sources of energy raised the profile of solar power as a valuable alternative to traditional sources of energy. In 2016 the European Union had a surface of solar panels the size of 9,500 football fields, and provided 3% of its electricity. Thanks to Edmond Becquerel, 10 days per year the European Union can be powered by the sun.
