“The hidden we see at last; the perfectly obvious, it seems to take a little longer.“

Edward R. Murro

“The time will come when our descendants will wonder that we did not know such obvious things.“

Seneca

Everyone has probably heard the saying “everything is energy” – be it in connection with physical theories from atomic structures to quantum states, or be it in relation to cosmic or esoteric views of reality(s)….

For decades, however, there was no sign of this realization being put into practice. At least not in the academic world of science. And outsiders had hardly a chance to be listened to – let alone that someone would have seriously dealt with their proposals to investigate new energy converters that feed from so far undefined sources. And so it took many years before it was finally acknowledged that there were in fact many new energy reservoirs that no one had previously known about. And that even more are still being discovered… of which a few examples will first be given.

The initial spark for the field of research now known as Micro Energy Harvesting (MEH) was the development of the legendary jogging shoe by Joe Paradiso, a researcher at the Massachusetts Institute of Technology (MIT) in Cambridge, USA, who in the late 1990s presented an ordinary running model that sent a weak electrical pulse through the sole with each step. When deformed, the piezoelectric ceramics embedded in the rubber emit enough energy to power, say, a small GPS navigation transmitter. The shoe will never be developed into a mass-produced product, but others are taking the idea and implementing it in a variety of ways. I report about this in details at corresponding paragraph Backpack and Running Shoe of chapter Muscle Power (s.d.).

By the way, in industry and building services engineering one speaks less flowery of energy-harvesting, but more sober of energy-autarkic systems.

And naturally also here are forerunners – and diverse realizations of astonishing sustainability show, our ancestors seemingly were more intelligent than following generations, who were blinded by ‘cheap oil’, ‘clean atomic energy’ and similar fairy tales…

The Piezo Effect effect, for example, was discovered as early as 1880: in certain materials – mostly crystals – an electrical voltage is generated when they are deformed. In the meantime, this effect is used in numerous devices, e.g. in inkjet printers, quartz clocks or electric lighters.

There are numerous other effects that allow energy to be extracted. As an example, consider the history of using atmospheric pressure to power clock movements.

The Amsterdam regent and mayor Jakob Dircksz de Graeff and the medical doctor, chemist and later councillor Pieter Jansz Hooft, who jointly run a chemical laboratory in Amsterdam, invent a ‘perpetual motion machine’ that actually works – as it derives its energy from changes in air temperature and pressure and is therefore also known as the barometric clock.

The picture of the device published by Hiesserle of Choda shows an outer glass tube through which a fluid moves (C and D), which is said to rise and fall as with the ebb and flow of the tide.

The invention is presented in 1604 by the muscle-power submarine designer Cornelis Jacobszoon Drebbel at the court of the English Stuart king James I, Drebbel passing it off as his own work and showing a patent obtained in 1598. The hoax blows up when he is unable to repair the machine, which has been broken by the Queen’s carelessness. One of Drebbel’s descendants later wasted the remains of the machine, so that a more exact description or even reconstruction could not be made until now.

In 1751, the French clockmaker Le Plat was the first to succeed in using the air as a drive, although he exploited the draught by means of a large paddle wheel – so that one could also speak of a wind-driven clockwork.

In the 1760s, the English automaton builder and clockmaker James Cox, together with the Belgian constructor Jean-Joseph Merlin (who, among other things, also invented a roller skate, see below), used air pressure fluctuations to drive a floor clock, which became known as Cox’s Timepiece (or Cox’s perpetual motion).

It is said to have contained 68 kg of mercury to record the changes in air pressure.

The first clock powered purely by atmospheric pressure was created about one hundred years later by the Austrian engineer Friedrich Ritter von Lössl. In 1880, the first autodynamic clock made by Lössl was installed in Vienna’s Cottagegarten. The movements and winding mechanisms of his clocks soon became so sophisticated that he could guarantee their operational reliability for decades.

The Lössl clock in the photo is self-winding due to fluctuations in atmospheric pressure. It remains in Vienna until 1894, but then has to make way for the construction of the city railway on the Währingergürtel. In 1897 Lössl donated it to the municipality of Aussee (today Bad Aussee), where it is still standing – in the meantime, however, for unknown reasons electrically operated, as if there were no more air pressure fluctuations nowadays…

In 1928, the Swiss engineer Jean-Léon Reutter developed the first prototypes of a table clock that draws its energy from the smallest atmospheric changes, and received the French patent for it just one year later. In contrast to the Lössl clock, which operated purely on ambient air, Reutter used a mixture of liquids as the working fluid for his clock, which reacted to both temperature and air pressure fluctuations. Other designers who continued to work on the concept were C. Paganini and T. Dieden.

Since Antoine LeCoultre opened his first watch shop in Le Sentier in 1833, and to this day, the Geneva watch manufacturer Jaeger Le Coultre has distinguished itself with Reutter’s ingenious invention of making even minimal temperature differences serviceable – for example with the Atmos table clock. This technique can be considered one of the first recent practical implementations in the field of energy harvesting.

The initial designs still work with the expansion of a mercury column, later a gas mixture is used. In the 1930s, Jaeger LeCoultre took over Reutter’s design, patented the watch and has been building it in series ever since. Today, Jaeger LeCoultre uses ethyl chloride, which already evaporates at 12°C. The secret lies in the material values of the ethyl chloride. The secret lies in the substance values of the working medium, which is also known to doctors as an anaesthetic.

The technology itself is quite simple: a pressurised can contains a gas mixture that expands as the temperature rises and contracts as the temperature falls. This movement is used to wind the mainspring of the watch. Since this fluctuation already exists between day and night, the watch does not need any battery or winding. A temperature difference of just one degree is enough to keep it running for 48 hours.

The really ingenious thing about the Atmos clock, however, is that it can be bought, that it works, and that it also refutes two assumptions that seem to be generally valid: firstly, that the ability to convert heat into work is independent of the properties of the material, and secondly, that a machine that extracts work from the heat of the environment – i.e. a perpetual motion machine of the second kind – is impossible.

Thermodynamically, only a perpetual motion machine of the first kind is impossible, but the actual existence of a perpetual motion machine of the second kind, which has already existed for many years, is at least astonishing. However, as soon as the reservoir of the energy used is known, one can confidently dispense with such misleading terms – because the energy source of the Atmos clocks is literally in the air.

Since this watch has a great symbolic value in Switzerland and serves as a figurehead for the lasting function and exact precision of a Swiss movement, it is still given away by the Swiss government to state guests and celebrities. This may be one of the 76 pieces of the Atmos 566 models, designed by designer Marc Newson in transparent and blue Baccarat crystal, which displays the time as well as the current star chart – and costs between $2,600 and $70,600.

Another pioneer of energy harvesting is the electrical engineer and inventor Nikola Tesla, who, in addition to the wireless transmission of electrical energy by induction, also worked on devices for the use of radiant energy and was granted two patents for this in 1901 (US No. 685,957 and 685,958). In these patents he lists in detail UV light, cathode rays and X-rays.

Tesla also calculates the resonance frequency of the earth, assuming that the electromagnetic waves with this frequency (6 – 8 Hz) are generated by the planet through lightning. However, the phenomenon of the Earth’s resonance frequency was not ‘officially’ discovered until 1952 by the physicists Winfried Otto Schumann and Herbert L. König, who continued to investigate it experimentally in the following years at the Technical University of Munich. When they were able to prove it in 1960, the new name Schumann resonance soon became widespread.

The fundamental wave of the Schumann resonance is 7.8 Hz, plus various harmonics between 14 and 45 Hz. The electromagnetic waves of these frequencies form standing waves along the circumference of the earth, which are ‘heated’ by lightning and other processes in the atmosphere and ionosphere. I will report in detail below on some approaches and methods for using these energies to generate electricity.

In the meantime, there is already a whole range of products in the field of energy harvesting. Here is an example:

In 2001, EnOcean GmbH was founded as a spin-off of Siemens AG, based in Oberhaching near Munich, which develops and markets a maintenance-free and flexible ‘batteryless wireless sensor technology’. The basic idea is based on a simple observation: When sensors record measured values, the energy state always changes as well. If a switch is pressed, the temperature changes or the light intensity varies, this always generates enough energy to send radio signals over a distance of up to 300 metres.

These technologies are now also marketed under the heading of low-power design. I will present more examples and implementations later.

About immense energy reservoir of ambient heat, often called anergy – in sense of waste-energy resp. (up to now!) not usable energy – I already reported at parts A and B. At chapter Heat-Energy of this part C I will present some more examples and implementations. At chapter Heat-Energy of this part C diverse methods are presented, how nevertheless effective usable energy resp. exergy can be produced by small differences of temperatures. Concerning energy-harvesting I will present actual status of techniques also further down.

Since the overarching technical term of energy harvesting has come into existence, things are moving much faster. For the first time, it is being seriously considered that there is actually an overabundance of a wide variety of usable forms of energy all around us.

With funding from the DFG and industrial partners, the new Micro Energy Harvesting Research Training Group will start its work at the University of Freiburg in October 2006, the first major research project on the topic of energy harvesting in Germany. Its goal is the systematic research, development and application of methods for energy conversion, storage and distribution for autonomous microsystems.

Nine professors and four young scientists from the Institute of Microsystems Engineering (IMTEK) and the Freiburg Materials Research Centre (FMF) will work together with the Fraunhofer Institute for Solar Energy Systems (FhG-ISE) as an associated partner to carry out future research, with 16 DFG-funded grants and a scientific coordinator. The budget amounts to € 2.4 million over 4.5 years. A further 5 industrial grants come from the Forum for Applied Microsystems Technology (FAM) and from national industrial companies.

For the scientists, the ‘harvesting’ of thermal, mechanical, optical or chemical energy from the environment of a microsystem represents a new, highly innovative and promising concept for supplying distributed systems with energy without power cables or batteries. These decentralized microsystems are currently spreading in rapidly growing numbers in various fields. In automobiles, for example, a large number of sensors record tire pressure, oil temperature, and important engine parameters, while in medical technology portable and implanted measurement systems for blood pressure, pulse, or blood sugar levels are in use. Distributed sensor and actuator systems in building technology determine temperature, humidity,_{CO2 content} and illuminance and control lighting, heating and air-conditioning systems. In production technology, networks of sensors and actuators control the flow of manufacturing processes.

In any case, the use of microsystems requires highly reliable, technically simple and durable energy supply methods that must also be completely maintenance-free. Just how sensible the developments in this sector are, which is trying, among other things, to reduce the use of batteries, can be seen from an estimate made public during the IDTechEx Energy Harvesting Europe conference in Munich in May 2010, according to which 253 billion non-recyclable batteries will end up in landfill sites in Europe over the next 50 years if better alternatives are not found.

Just how important the sector has become after only a few years is shown by the sales price of a corresponding study from February 2009. For the detailed technical information Energy Harvesting, Micro Batteries and Power Management ICs: Competitive Environment, the Irish company Research and Markets charges the hefty price of €1,593. At exactly the same time, the Energy Harvesting Journal goes online. Updated in October 2010, the 357-page report Energy Harvesting and Storage for Electronic Devices 2010-2020 is priced at $3,750 for the electronic edition and an additional $250 for the hard copy. The 2012 edition is already priced at $3,995.

In the following, I present the current state of research in this promising sector, along with very many different forms of implementation – and all at no cost.

In the course of updates, I have decided on an alphabetical order, even if this leads to overlaps between in some cases. Converting the movements of the human body into useful energy I treat in detail under Muscle Power, as it is not assigned to Micro Energy Harvesting. The exception is systems based on micromuscular movements such as those of the eyelid, fingers (in typing, for example), or heartbeat, which are listed here under biological transducers.

In many cases, the technologies have long histories and diverse antecedents, the mention of which should help put the use of the various energy reservoirs into a meaningful context.

Specifically, this chapter addresses the following topics and implementations:

Atmospheric systems

Atmospheric Electricity
Lightning
Hygroelectricity
Air pressure
Humidity
Evaporation generator

Biological systems

Bacterial systems
Fluids
Insects and molluscs
Muscular systems
Plants
ph-value
Animals
Other Technologies

Fields and Waves

Electromagnetic Induction
Electrostatics
Radio waves
Light, UV, Infrared and Laser
Magnetic field
Sound
Triboelectricity
Heat

Mechanical Systems

Pressure
Piezoelectricity
Piezoelectric zinc oxide nanowires
Piezomagnetism
Raindrops
Shock absorbers
Road generators
Currents
Vibration

Other technologies

Bionic contact lenses

Atmospheric Systems

Atmospheric Electricity

As early as the 19th and early 20th centuries, various researchers investigated the possibility of extracting usable electricity from the electric field surrounding the earth. The Earth’s electrostatic field (o. Earth’s electric field) results from the excess electric charge on the Earth’s surface produced by ionizing radiation from space (solar wind).

The global atmospheric electric cycle, in turn, is the continuous movement of electric current between the ionosphere and the Earth’s surface. This flow is driven by thunderstorms, which primarily use lightning to create an electrical potential difference between the Earth’s surface and the ionosphere.

The first studies of atmospheric electricity can be traced back to the 1740s, when Benjamin Franklin and his friend Thomas-François Dalibard began their famous thunderstorm experiments.

And the world’s first electric motor is also an electrostatic one, invented in 1748 by Franklin – who is said to have used it to power a carillon. The inventor even claims to have turned a roasting spit with a turkey, but there is no evidence of this (the world’s first patent for an electromagnetic motor powered by batteries is filed by blacksmith Thomas Davenport in 1834; after initial rejection, it is granted in 1837 ).

The simplest version of Franklin’s electrostatic motor consists of a wooden disc lying horizontally, from which narrow glass strips with brass thimbles at the ends protrude all around. The disc is placed between two Leiden bottles of opposite polarity.

Franklin is not entirely happy with his motor, however, as it requires an additional force to rub the bottles. He then builds a second version of the machine without Leiden bottles, the rotor of which consists of a 17-inch glass disc rotating horizontally on low-friction bearings. Both surfaces of the disc are covered with a gold film, except for a border around the edge. The rotor is thus constructed like a modern flat-plate capacitor. On a single charge, this machine runs for 30 minutes at up to 50 rpm.

In 1752, the French physician, botanist, and encyclopedist Louis Guillaume Le Monnier (o. Lemonnier) observed atmospheric electrification even in fair weather. He was the first to prove that electricity could be moved through a conductor with his electrophysical experiments, in which he allowed electric current generated by a Leiden bottle to be carried through a cable about 1,850 m long.

Lemonnier’s experiments with atmospheric electricity are repeated and extended by the Italian natural philosopher Giovanni Battista Beccaria – who is also responsible for the spread of lightning conductors in Italy, which therefore become established there earlier than in the rest of Europe. Beccaria collects a large number of observations in which he combines a simple spherical electrometer with iron wires, kites and even rockets.

The Swiss naturalist Horace Bénédict de Saussure, who is appointed professor of philosophy at the Academy of Geneva in 1762 at the age of only 22, invents various types of instruments to explore atmospheric electricity – as does the English physicist John Canton, who, among other things, constructs an electroscope and determines the electric charge collected in Leiden bottles.

Using the instruments developed by Canton, the Italian physicist Tiberius Cavallo makes extensive observations in the field of amospheric electricity beginning in 1775 and also experiments with Franklin’s kite.

Around 1787, Italian scientist Alessandro Volta and British explorer Abraham Bennett independently discover successful methods for detecting and measuring atmospheric electricity. In the same year, Charles Augustin Coulomb is the first to determine the distribution of electricity in the air.

In 1845, the Italian meteorologist, seismologist and volcanologist Luigi Palmieri designed improved measuring instruments to investigate the electrical voltages in the atmosphere. In 1884 the German translation of his book ‘Die atmosphärische Elektricität’ was published.

The distribution of electricity in the air was studied in 1850 by the Italian physicist and neurophysiologist Carlo Matteucci, who used an improved Coulomb torsion balance for this purpose. He is also the first to succeed in directly measuring the electric current of a muscle.

In the 1850s and 1860s, the engineer Charles Hippolyte Vion from Paris proposed the technical use of the earth’s electric field. In 1860, he was granted US Patent No. 28,793 for a method of using atmospheric electricity.

Another attempt at the practical use of atmospheric electricity was made in 1864 by the American dentist and inventor Mahlon Loomis from Washington, Columbia. Loomis, dreaming of putting this source of energy at the service of mankind, proposes various devices for collecting it – moreover, in a series of experiments he succeeds in realizing a primitive form of wireless telegraphy.

The basic principle of his system is simple. In 1866, in Virginia, he launches kites covered with copper gauze from two mountain peaks about 22.5 km apart, each held by 180 m long thin lines of copper wire. Each wire runs through a galvanometer. As soon as one of the wires is grounded or removed from the ground again, there is a disturbance of the atmospheric electric field, which is registered by the galvanometer of the other kite.

Each time the action is repeated, the needle of the galvanometer strikes out. After Loomis obtains a patent for his invention in 1872 (US No. 129,971), he spends several years trying to improve his system and find support for it, but ultimately his ‘aerial telegraph’ dies with him in 1886.

Ironically, it was precisely in 1886 that German physicist Heinrich Rudolf Hertz first succeeded in transmitting electromagnetic waves from a transmitter to a receiver. In 1897, Hertz is also said to have proposed the installation of a 300-metre-long metal net with about 3.6 million collector needles, which would be lifted into the air by kites. By means of a special collector, atmospheric electricity should charge a battery of 20.000 accumulators.

So far, however, I could not verify this information, nor the information that Hertz (sometimes written only as Heinrich Rudolph in Anglo-Saxon literature), in 1898 designed an elliptical aircraft with faceted surfaces as an optimized collector, which also uses the Coanda effect to minimize the effect of the wind.

In 1870, German physicist Johann Christoff Poggendorff builds a very simple motor consisting of little more than a plastic disk (Poggendorff used glass at the time) and two electrodes. Although he was able to measure an efficiency of more than 50%, the inventor’s opinion that it would never be possible to build effective drives using this principle was shared by many scientists of his time. The attraction of these engines – which nevertheless no one can escape – lies in the fact that, even without achieving much power, they can in principle run forever.

The Austrian physicist Franz-Serafin Exner was also concerned with electricity in the atmosphere. In 1887 he invented a simple and compact aluminium blade electrometer, which was later further developed by the physicists Julius Elster and Hans Geitel, who used it to detect the presence of ions in the atmosphere.

Exner also aroused the interest of his student Victor Franz Hess in the subject of atmospheric electricity. In 1912, during one of his balloon ascents, the later Nobel Prize winner discovers cosmic rays, which he then calls cosmic radiation. In the early 20th century, balloon ascents provide information about the electric field in the upper atmosphere for the first time.

Mark W. Dewey from Syracuse, New York, is granted a patent in 1889 for a tower-like device designed to harness atmospheric electricity (US No. 414,943).

In 1901, engineer Andor Palencsár of Budapest, Hungary, patented a complicated system called ‘Apparatus for collecting atmospheric electricity’, consisting of a double-walled heated balloon covered by a movable net of pointed collectors (US No. 674,427, applied for 1900).

In this project, electricity is to be supplied to a rheostatic machine, a mechanical device for developing a spark current in the manner of a bottle battery, which goes back to the French physicist Raymond Louis Gaston Planté. The latter had invented the machine while investigating the differences between static electricity and dynamic electricity (i.e. from batteries).

Other patents of the period were by J. Gallegos of San José, Guatemala (Static electric Machine, U.S. No. 633,829, issued 1899); Elihu Thomson of Swampscott, Massachusetts (Electrostatic motor, U.S. No. 735,621, filed 1901, issued 1903); Harold B. Smith of Worcester, Massachusetts (Apparatus for transforming electrical energy into mechanical energy, U.S. No. 993,561, filed 1908, issued 1911); and Walter G. Cady of Hiddletown, Cnnecticut (U.S. No. 1,693,806, filed 1925, issued 1928).