I came across this information graphic through a, “I see an information graphic a day” blog. I am attracted to the simple use of colour and picto-graphic  illustrations. Alongside this I found this as a clear example of a strong information graphic as it is simple yet clear in its message.


What is sustainable energy?

Sustainable energy is energy that can potentially be kept up well into the future without causing harmful repercussions for future generations. A number of types of energy can be thought of as sustainable, and many governments promote their use and the development of new technologies that fit within this model. Increasing rates of energy consumption around the world have led to a corresponding rise in concerns about where the energy comes from and if it will become more scarce.

Several factors go into making energy sustainable. The first is whether or not the current use of the energy is something that could potentially persist into the future, which leads many forms of renewable energy to qualify as sustainable. People can generate energy from windmills, ocean waves, and the sun without running out of energy and resources, making these methods sustainable for use by future generations. By contrast, fossil fuels are not treated as sustainable because the Earth’s supplies of crude oil will eventually run out.

Another consideration is energy efficiency. Some forms of renewable energy, for example, take quite a lot of effort to actually generate, meaning that almost as much energy goes into their production as the sources themselves generate. Energy efficiency can also be used to describe the technologies that use energy, such as homes, cars, and businesses. Increased efficiency in the way energy is used makes sustainable energy stretch further.

Many people also feel that the environmental impact an energy source has is another facet of whether or not it is considered sustainable, which is why sources like nuclear power are often not treated as such. Although it meets the demands of renewability and energy efficiency, nuclear power can have a negative impact on the environment. Likewise, some of the methods used to produce solar panels, wind turbines, and other technology to convert renewable sources into energy are polluting, leading to concerns that such technology merely moves the pollution to a different place, making it unsustainable.

Another factor important to some people in the energy field is independence. Some critics argue that energy is not sustainable if a nation is forced to rely on another country to meet its energy needs, even if that energy is renewable, non-polluting, and efficient. For example, if the United States relied heavily on Canadian wind farms, this would violate the criterion of energy independence. Being able to meet one’s own energy needs as a nation is an important part of sustainable energy in the eyes of some people who are concerned about the intersection of energy and politics.

From this article I managed to develop an understanding in what the term sustainable energy resources means> it also introduced me to why the idea of relying on nuclear power plants would to be beneficial to us.


Energy harvesting

Energy harvesting (also known as power harvesting or energy scavenging) is the process by which energy is derived from external sources (e.g., solar power, thermal energy, wind energy, salinity gradients,[citation needed] and kinetic energy), captured, and stored for small, wireless autonomous devices, like those used in wearable electronics and wireless sensor networks.

Energy harvesters provide a very small amount of power for low-energy electronics. While the input fuel to some large-scale generation costs money (oil, coal, etc.), the energy source for energy harvesters is present as ambient background and is free. For example, temperature gradients exist from the operation of a combustion engine and in urban areas, there is a large amount of electromagnetic energy in the environment because of radio and television broadcasting.


Energy harvesting devices converting ambient energy into electrical energy have attracted much interest in both the military and commercial sectors. Some systems convert motion, such as that of ocean waves, into electricity to be used by oceanographic monitoring sensors for autonomous operation. Future applications may include high power output devices (or arrays of such devices) deployed at remote locations to serve as reliable power stations for large systems. Another application is in wearable electronics, where energy harvesting devices can power or recharge cellphones, mobile computers, radio communication equipment, etc. All of these devices must be sufficiently robust to endure long-term exposure to hostile environments and have a broad range of dynamic sensitivity to exploit the entire spectrum of wave motions.

[edit]Accumulating energy

Energy can also be harvested to power small autonomous sensors such as those developed using MEMS technology. These systems are often very small and require little power, but their applications are limited by the reliance on battery power. Scavenging energy from ambient vibrations, wind, heat or light could enable smart sensors to be functional indefinitely. Several academic and commercial groups have been involved in the analysis and development of vibration-powered energy harvesting technology, including the Control and Power Group and Optical and Semiconductor Devices Group at Imperial College LondonIMEC and the partnering Holst Centre,[1] AdaptivEnergy, LLCARVENIMIT Boston, Victoria University of Wellington,[2] Georgia TechUC BerkeleySouthampton UniversityUniversity of Bristol,[3] Nanyang Technological University,[4] PMG PerpetuumVestfold University CollegeNational University of Singapore,[5] NiPS Laboratory at the University of Perugia,[6] Columbia University,[7] Universidad Autónoma de Barcelona and USN & Renewable Energy Lab at the University of Ulsan (Ulsan, South Korea). TheNational Science Foundation also supports an Industry/University Cooperative Research Center led by Virginia Tech and The University of Texas at Dallas called the Center for Energy Harvesting Materials and Systems.

Typical power densities available from energy harvesting devices are highly dependent upon the specific application (affecting the generator’s size) and the design itself of the harvesting generator. In general, for motion powered devices, typical values are a few µW/cm³ for human body powered applications and hundreds of µW/cm³ for generators powered from machinery.[8] Most energy scavenging devices for wearable electronics generate very little power.[9][verification needed]

[edit]Storage of power

In general, energy can be stored in a capacitorsuper capacitor, or battery. Capacitors are used when the application needs to provide huge energy spikes. Batteries leak less energy and are therefore used when the device needs to provide a steady flow of energy.

[edit]Use of the power

Current interest in low power energy harvesting is for independent sensor networks. In these applications an energy harvesting scheme puts power stored into a capacitor then boosted/regulated to a second storage capacitor or battery for the use in the microprocessor.[10] The power is usually used in a sensor application and the data stored or is transmitted possibly through a wireless method.[11]


The history of energy harvesting dates back to the windmill and the waterwheel. People have searched for ways to store the energy from heat and vibrations for many decades. One driving force behind the search for new energy harvesting devices is the desire to power sensor networks and mobile devices without batteries. Energy harvesting is also motivated by a desire to address the issue of climate change and global warming.


There are many small-scale energy sources that generally cannot be scaled up to industrial size:

  • Some wristwatches are powered by kinetic energy (called automatic watches), in this case movement of the arm is used. The arm movement causes winding of its mainspring. A newer design introduced by Seiko (“Kinetic”) uses movement of a magnet in the electromagnetic generator instead to power the quartz movement. The motion provides a rate of change of flux, which results in some induced emf on the coils. The concept is simply related to Faraday’s Law.
  • Photovoltaics is a method of generating electrical power by converting solar radiation (both indoors and outdoors) into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of cells containing a photovoltaic material.
  • Thermoelectric generators (TEGs) consist of the junction of two dissimilar materials and the presence of a thermal gradient. Large voltage outputs are possible by connecting many junctions electrically in series and thermally in parallel. Typical performance is 100-200 μV/K per junction. These can be utilized to capture mW.s of energy from industrial equipment, structures, and even the human body. They are typically coupled with heat sinks to improve temperature gradient.
  • Micro wind turbine are used to harvest wind energy readily available in the environment in the form of kinetic energy to power the low power electronic devices such as wireless sensor nodes. When air flows across the blades of the turbine, a net pressure difference is developed between the wind speeds above and below the blades. This will result in a lift force generated which in turn rotate the blades.
  • Piezoelectric crystals or fibers generate a small voltage whenever they are mechanically deformed. Vibration from engines can stimulate piezoelectric materials, as can the heel of a shoe.
  • Special antennas can collect energy from stray radio waves [12] or theoretically even higher frequency EM radiation.[citation needed]
  • Power from keys pressed during use of a portable electronic device or remote controller, using magnet and coil or piezoelectric energy converters, may be used to help power the device.[13]

[edit]Ambient-radiation sources

A possible source of energy comes from ubiquitous radio transmitters. Historically, either a large collection area or close proximity to the radiating wireless energy source is needed to get useful power levels from this source. The nantenna is one proposed development which would overcome this limitation by making use of the abundant natural radiation (such as solar radiation).

One idea is to deliberately broadcast RF energy to power remote devices: This is now commonplace in passive Radio Frequency Identification (RFID) systems, but the Safety and US Federal Communications Commission (and equivalent bodies worldwide) limit the maximum power that can be transmitted this way to civilian use. This method has been used to power individual nodes in a wireless sensor network[14]

[edit]Biomechanical harvesting

Biomechanical energy harvesters are also being created. One current model is the biomechanical energy harvester of Max Donelan which straps around the knee.[15] Devices as this allow the generation of 2.5 watts of power per knee. This is enough to power some 5 cell phones. The Soccket can generate and store 6 watts.[16]

[edit]Photovoltaic harvesting

Photovoltaic (PV) energy harvesting wireless technology offers significant advantages over wired or solely battery-powered sensor solutions: virtually inexhaustible sources of power with little or no adverse environmental effects. Indoor PV harvesting solutions have to date been powered by specially tuned amorphous silicon (aSi)a technology most used in Solar Calculators. In recent years new PV technologies have come to the forefront in Energy Harvesting such as Dye Sensitized Solar Cells (DSSC). The dyes absorbs light much like chlorophyll does in plants. Electrons released on impact escape to the layer of TiO2 and from there diffuse, through the electrolyte, as the dye can be tuned to the visible spectrum much higher power can be produced. At 200 lux a DSSC can provide over 15 µW per cm².

Batteryless TV remote control from Arveni for Philips

[edit]Piezoelectric energy harvesting

The piezoelectric effect converts mechanical strain into electric current or voltage. This strain can come from many different sources. Human motion, low-frequency seismic vibrations, and acoustic noise are everyday examples. Except in rare instances the piezoelectric effect operates in AC requiring time-varying inputs at mechanical resonance to be efficient.

Most piezoelectric electricity sources produce power on the order of milliwatts, too small for system application, but enough for hand-held devices such as some commercially available self-winding wristwatches. One proposal is that they are used for micro-scale devices, such as in a device harvesting micro-hydraulic energy. In this device, the flow of pressurized hydraulic fluid drives a reciprocating piston supported by three piezoelectric elements which convert the pressure fluctuations into an alternating current.

As piezo energy harvesting has been investigated only since the late 1990s,[17] it remains an emerging technology. Nevertheless some interesting improvements were made with the self-powered electronic switch at INSA school of engineering, implemented by the spin-off Arveni. In 2006, the proof of concept of a battery-less wireless doorbell push button was created, and recently, a demonstrator showed that classical TV infra-red remote control can be powered by a piezo harvester. Other industrial applications appeared between 2000 and 2005,[18] to harvest energy from vibration and supply sensors for example, or to harvest energy from shock.

Piezoelectric systems can convert motion from the human body into electrical power. DARPA has funded efforts to harness energy from leg and arm motion, shoe impacts, and blood pressure for low level power to implantable or wearable sensors. The nanobrushes of Dr. Zhong Lin Wang are another example of a piezoelectric energy harvester.[19] They can be integrated into clothing. Careful design is needed to minimise user discomfort. These energy harvesting sources by association have an impact on the body. The Vibration Energy Scavenging Project[20] is another project that is set up to try to scavenge electrical energy from environmental vibrations and movements. Xudong Wang’s microbelt can be used to gather electricity from respiration.[21] Finally, a millimeter-scale piezoelectric energy harvester has also already been created.[22]

The use of piezoelectric materials to harvest power has already become popular. Piezoelectric materials have the ability to transform mechanical strain energy into electrical charge. Piezo elements are being embedded in walkways[23][24][25] to recover the “people energy” of footsteps. They can also be embedded in shoes[26] to recover “walking energy”. Researchers at MIT developed the first micro-scale piezoelectric energy harvester using thin film PZT in 2005.[27] Arman Hajati and Sang-Gook Kim invented the Ultra Wide-Bandwidth micro-scale piezoelectric energy harvesting device by exploiting the nonlinear stiffness of a doubly clamped microelectromechanical systems (MEMSs) resonator. The stretching strain in a doubly clamped beam shows a nonlinear stiffness, which provides a passive feedback and results in amplitude-stiffened Duffing mode resonance.[28]

[edit]Pyroelectric energy harvesting

The pyroelectric effect converts a temperature change into electric current or voltage. It is analogous to the piezoelectric effect, which is another type of ferroelectric behavior. Pyroelectricity requires time-varying inputs and suffers from small power outputs in energy harvesting applications due to its low operating frequencies. However, one key advantage of pyroelectrics overthermoelectrics is that many pyroelectric materials are stable up to 1200 ⁰C or higher, enabling energy harvesting from high temperature sources and thus increasing thermodynamic efficiency.

One way to directly convert waste heat into electricity is by executing the Olsen cycle on pyroelectric materials. The Olsen cycle consists of two isothermal and two isoelectric field processes in the electric displacement-electric field (D-E) diagram. The principle of the Olsen cycle is to charge a capacitor via cooling under low electric field and to discharge it under heating at higher electric field. Several pyroelectric converters have been developed to implement the Olsen cycle using conduction,[29] convection,[30][31][32][33] or radiation.[34] It has also been established theoretically that pyroelectric conversion based on heat regeneration using an oscillating working fluid and the Olsen cycle can reach Carnot efficiency between a hot and a cold thermal reservoir.[35] Moreover, recent studies have established polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] polymers [36] and lead lanthanum zirconate titanate (PLZT) ceramics [37] as promising pyroelectric materials to use in energy converters due to their large energy densities generated at low temperatures. Additionally, a pyroelectric scavenging device that does not require time-varying inputs was recently introduced. The energy-harvesting device uses the edge-depolarizing electric field of a heated pyroelectric to convert heat energy into mechanical energy instead of drawing electric current off two plates attached to the crystal-faces.[38]


In 1821, Thomas Johann Seebeck discovered that a thermal gradient formed between two dissimilar conductors produces a voltage. At the heart of the thermoelectric effect is the fact that a temperature gradient in a conducting material results in heat flow; this results in the diffusion of charge carriers. The flow of charge carriers between the hot and cold regions in turn creates a voltage difference. In 1834, Jean Charles Athanase Peltier discovered that running an electric current through the junction of two dissimilar conductors could, depending on the direction of the current, cause it to act as a heater or cooler. The heat absorbed or produced is proportional to the current, and the proportionality constant is known as the Peltier coefficient. Today, due to knowledge of the Seebeck and Peltier effects, thermoelectric materials can be used as heaters, coolers and generators (TEGs).

Ideal thermoelectric materials have a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Low thermal conductivity is necessary to maintain a high thermal gradient at the junction. Standard thermoelectric modules manufactured today consist of P- and N-doped bismuth-telluride semiconductors sandwiched between two metallized ceramic plates. The ceramic plates add rigidity and electrical insulation to the system. The semiconductors are connected electrically in series and thermally in parallel.

Miniature thermocouples have been developed that convert body heat into electricity and generate 40μW at 3V with a 5 degree temperature gradient, while on the other end of the scale, large thermocouples are used in nuclear RTG batteries.

Practical examples are the finger-heartratemeter by the Holst Centre and the thermogenerators by the Fraunhofer Gesellschaft.[39][40]

Advantages to thermoelectrics:

  1. No moving parts allow continuous operation for many years. Tellurex Corporation[41] (a thermoelectric production company) claims that thermoelectrics are capable of over 100,000 hours of steady state operation.
  2. Thermoelectrics contain no materials that must be replenished.
  3. Heating and cooling can be reversed.

One downside to thermoelectric energy conversion is low efficiency (currently less than 10%). The development of materials that are able to operate in higher temperature gradients, and that can conduct electricity well without also conducting heat (something that was until recently thought impossible), will result in increased efficiency.

Future work in thermoelectrics could be to convert wasted heat, such as in automobile engine combustion, into electricity.

[edit]Electrostatic (capacitive) energy harvesting

This type of harvesting is based on the changing capacitance of vibration-dependent varactors. Vibrations separate the plates of an initially charged varactor (variable capacitor), and mechanical energy is converted into electrical energy. An example of an electrostatic energy harvester with embedded energy storage is the M2E Power Kinetic Battery. Another example is CSIRO’s Flexible Integrated Energy Device (FIED)[42] Yet another example is the Tremont Electric nPower PEG.[43] Finally, there is the Regenerative shock absorber.

Electrostatic energy harvesters need a polarization source to work and to convert mechanical energy from vibrations into electricity. The polarization source should be in the order of some hundreds of volts ; this greatly complicates the power management circuit. Another solution consists in using electrets, that are electrically charged dielectrics able to keep the polarization on the capacitor for years.[44]

[edit]Magnetostatic energy harvesting

Magnets wobbling on a cantilever are sensitive to even small vibrations and generate microcurrents by moving relative to conductors due to Faraday’s law of induction. By developing a miniature device of this kind in 2007, a team from the University of Southampton made possible the planting of such a device in environments that preclude having any electrical connection to the outside world. Sensors in inaccessible places can now generate their own power and transmit data to outside receivers.[45]

One of the major limitations of the magnetic vibration energy harvester developed at University of Southampton is the size of the generator, in this case approximately one cubic centimeter, which is much too large to integrate into today’s mobile technologies. The complete generator including circuitry is a massive 4 cm by 4 cm by 1 cm[45] nearly the same size as some mobile devices such as the ipod nano. Further reductions in the dimensions are possible through the integration of new and more flexible materials as the cantilever beam component. In 2012 a group atNorthwestern University developed a vibration-powered generator out of polymer in the form of a spring.[46] This device was able to target the same frequencies as the University of Southampton groups silicon based device but with one third the size of the beam component.

[edit]Blood sugar energy harvesting

Another way of energy harvesting is through the oxidation of blood sugars. These energy harvesters are called Biofuel cells. They could be used to power implanted electronic devices (e.g., pacemakers, implanted biosensors for diabetics, implanted active RFID devices, etc.). At present, the Minteer Group of Saint Louis University has created enzymes that could be used to generate power from blood sugars. However, the enzymes would still need to be replaced after a few years.[47] In 2012 a pacemaker was powered by implantable biofuel cells at Clarkson University under the leadership of Dr. Evgeny Katz. [48]

[edit]Tree based energy harvesting

Tree metabolic energy harvesting is a type of bio-energy harvesting. Voltree has developed a method for harvesting energy from trees. These energy harvesters are being used to power remote sensors and mesh networks as the basis for a long term deployment system to monitor forest fires and weather in the forest. Their website says that the useful life of such a device should be limited only by the lifetime of the tree to which it is attached. They recently deployed a small test network in a US National Park forest.[49]

Other sources of energy from trees include capturing the physical movement of the tree in a generator. Theoretical analysis of this source of energy shows some promise in powering small electronic devices.[50] A practical device based on this theory has been built and successfully powered a sensor node for a year.[51]

[edit]Future directions

Electroactive polymers (EAPs) have been proposed for harvesting energy. These polymers have a large strain, elastic energy density, and high energy conversion efficiency. The total weight of systems based on EAPs is proposed to be significantly lower than those based on piezoelectric materials.

Nanogenerators, such as the one made by Georgia Tech, could provide a new way for powering devices without batteries.[52] As of 2008, it only generates some dozen nanowatts, which is too low for any practical application.

Noise harvesting NiPS Laboratory in Italy has recently proposed to harvest wide spectrum low scale vibrations via a nonlinear dynamical mechanism that can improve harvester efficiency up to a factor 4 compared to traditional linear harvesters.[53]


I arrived at this Wikipedia page from Google searching a word I hoped to understand more. I am curious as to how thermoelectrics work and how thermoelectrics could give us a better outcome in 2100.


How Do Nuclear Plants Work?

In a nuclear-fueled power plant – much like a fossil-fueled power plant – water is turned into steam, which in turn drives turbine generators to produce electricity. The difference is the source of heat. At nuclear power plants, the heat to make the steam is created when uranium atoms split – called fission. There is no combustion in a nuclear reactor. Here’s how the process works.

There are two types of nuclear reactors in the United States:

Pressurized Water Reactor

Pressurized Water Reactors (also known as PWRs) keep water under pressure so that it heats, but does not boil. This heated water is circulated through tubes in steam generators, allowing the water in the steam generators to turn to steam, which then turns the turbine generator. Water from the reactor and the water that is turned into steam are in separate systems and do not mix.

View animated image of a Pressurized Water Reactor

Source: Nuclear Regulatory Commission

Boiling Water Reactor

In Boiling Water Reactors (also known as BWRs), the water heated by fission actually boils and turns into steam to turn the turbine generator. In both PWRs and BWRs, the steam is turned back into water and can be used again in the process.

View animated image of a Boiling Water Reactor

Source: Nuclear Regulatory Commission



World Energy and Population Trends to 2100


Throughout history, the expansion of human population has been supported by a steady growth in our use of high-quality exosomatic energy. The operation of our present industrial civilization is wholly dependent on access to a very large amount of energy of various types. If the availability of this energy were to decline significantly it could have serious repercussions for civilization and the human population it supports. This paper constructs production models for the various energy sources we use and projects their likely supply evolution out to the year 2100. The full energy picture that emerges is then translated into a population model based on an estimate of changing average per-capita energy consumption over the century. Finally, the impact of ecological damage is added to the model to arrive at a final population estimate.

This model, known as the “World Energy and Population” model, or WEAP, suggests that the world’s population will decline significantly over the course of the century.


I sought from this paper, information on the regulated expected use coming towards 2100. Using the graphs as visual s helped me understand which aspects of the information I was taking in was most important.