Lithium-air batteries are currently in the works, and IBM predicts that batteries “that use the air we breath to react with energy-dense metal” will result in smaller, lighter rechargeable batteries that last ten times longer than today’s lithium-ion types. Whilst such batteries could be used in everything from cars to home appliances, it is also suggested that small items such as cell phones might not need batteries at all. IBM is trying to reduce the amount power required for such devices to less than 0.5 volts per transistor. At those rates, it is claimed, they could be powered via “energy scavenging” – like already-existing kinetic wrist watches that get their power from the user’s arm movements, or experimental piezoelectric devices.

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RavenSkin insulation stores up daytime heat for release when temperatures drop

RavenBrick, the company that brought us the smart tinting RavenWindow, has added to its folio of temperature regulating building materials with RavenSkin. Unlike traditional insulation that blocks all heat equally, this innovative wall insulation material absorbs heat during the day to keep the interior cool and slowly releases the stored heat at night to warm the building when the sun goes down. Read More

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Powering Up

the Battery-Free World

The amount of electricity generated by vibration is proportional to the frequency and amplitude of the vibrator, which means that maximizing both will easily increase output. Because of the way vibration-based generators work, however, fine adjustment is needed to ensure they resonate at a particular frequency, and the inherent vibrational frequency must be matched to the application.

A look at the vibration parameters for the announced prototypes reveals just what application each firm is aiming at. Sanyo Electric, for example, plans to having people wear its device and set the frequency to 2Hz ^Note . Murata Manufacturing chose 10Hz to 20Hz, which is a neat fraction of the 50Hz/60Hz frequency of commercial power. Their decision, explains a source at the firm, was that the large number of vibration sources in that range would provide a wide range of applications. Omron, on the other hand, comments that “about 30Hz is common in factories, vehicles and bridges, for example.”

Note Sanyo Electric is now developing a prototype measuring 23mm x 42mm x 6mm, capable of generating 120?W.

Omron is planning to wait until the market scale becomes a little clearer, and ship product in 2011, according to Masashi Doi, manager, core technology centerof the firm. The company has already shifted its development target from boosting generating performance to assuring reliability. Many wireless sensor networks are expected to be “plug and forget,” capable of running for at least five years without needing anything, so reliability assurance is critical.

Troubling Patents

Patents could pose a thorny problem for practical applications, though. Basic patents do exist for energy harvesting, and some people in the industry have warned that care will be needed when launching business in the field. They are held by EnOcean ^{Note 9)}, and already eighteen key patents in energy harvesting have been identified in the firm’s portfolio.

Note 9) EnOcean began research into energy harvesting in 1995, when it was still a research arm of Siemens AG of Germany. It became an independent venture business in 2001, acquiring all related patents from Siemens in return for 19% of its issued stock.

Fig. 10 Patents held by EnOcean

The patents are for “transmitting collected data using power acquired through energy harvesting technology,” which covers a wide range of applications.

Of these, the strongest is said to be international patent WO 98/36395 (Fig. 10), which covers a very wide scope. It has been granted in a number of nations already, including Germany, the US and China. The patent was filed in Japan in 1998, but patent examination was refused and as a result the patent has not been granted. EnOcean refused to accept the judgment, requesting reconsideration in 2008.

A number of manufacturers planning to ship products using energy harvesting technology as early as 2011 are worried about possible patent issues, but EnOcean Chief Executive Officer (CEO) Markus Brehler has said “Our business is shipping products, not arguing about patents.” In any case, though, care will be needed in export sale.

1) Harrop, P. et al., Energy Harvesting and Storage for Electronic Devices 2010-2020, IDTechEx Ltd., July 2010.

2) Innovative Research and Products, Inc., ULTRA-LOW POWER (MICROWATT) ENERGY HARVESTING FOR WIRELESS SWITCHES AND WIRELESS SENSOR NETWORKING TYPES, APPLICATIONS, NEW DEVELOPMENTS, INDUSTRY, April 2010.

3) Roundy, S. et al., “A study of low level vibrations as a power source for wireless sensor nodes,” Computer Communications 26, Issue 11, pp. 1131-1144, July 2003.

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Powering Up

the Battery-Free World

One of the reasons that overseas manufacturers have pulled so far ahead of Japan in practical application is that domestic manufacturers are overly concerned with generating electricity. Many firms in Japan have been developing power generating devices for years, but the thrust of research and development has been boosting output. European and American firms more interested in combining the most useful characteristics of peripheral circuits, on the other hand, have taken the lead in market development.

Table 2 Energy Harvesting Consortium Members

The situation is beginning to change, however, as companies swing into action to make businesses out of the new technology. One symbol of the change is the establishment of the Energy Harvesting Consortium, which was established in May 2010 by thirteen companies (Table 2). With the addition of eight latecomers, the group is already collecting related industry information and stimulating discussion and exchange between member firms.

Corporate Aim Revealed through Frequency

Japanese companies are finally making the transition from competing to make a better generator to actually refining products. Some firms, for example, are actively working on products to generate electricity from vibration: Omron Corp. of Japan, Sanyo Electric Co., Ltd. of Japan and Murata Manufacturing Co., Ltd. of Japan are developing prototypes with very specific applications in mind (Fig. 9) ^{Note 7)}.

Note 7) The three companies are developing vibration-based generators utilizing a material called electret. When the areas of two opposing electrodes change as a result of vibration, it causes a change in induced charge, producing a current.

Fig. 9 Corporate Objectives Apparent in Waveband

Scope of application shown for vibration generators. The optimal target frequency varies with application, revealing each firm’s goals. (Diagram by Nikkei Electronics based on material courtesy Omron, plus papers presented by Sanyo Electric and Murata Manufacturing)

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Up the Battery-Free World

The idea behind wireless sensor networks is old, but a battery-free design would vastly expand its range of application. Voltree Power LLC of the US, a spin-off from the Massachusetts Institute of Technology (MIT) of the US, has been contracted by the US Department of Agriculture to construct a temperature sensor network in mountainous, forested regions of California ^{Note 6)}.

Note 6) The power source is based on technology developed by MIT utilizing the electric potential difference between the tree trunk and surrounding area, which is between 50mV and 200mV.

The objective is to detect forest fires and minimize damage. Considering the damage cause by such fires, and the cost of firefighting personnel, equipment and supplies, the economics of constructing and operating a wireless sensor network are clear indeed.

One application attracting considerable attention of late is health monitoring. Sensors are mounted on buildings and bridges, detecting structural change. The amount and speed of these changes are used to diagnose the health of the structure, with acquired data utilized in guiding maintenance and component replacement.

There is considerable demand for health monitoring in the motor and engine sectors, as well. Automobiles use a large number of sensors to detect the conditions of various components, and as a result use vast quantities of wire harnesses. If engine and motor heat and vibration energy can be used to drive wireless sensors, it would be possible to dramatically cut the number of wire harnesses needed.

Another application in the health monitoring field is the life recorder, managing people and animals. Mounted on livestock or wild animals, for example, it can provide not only position information, but also data such as body temperature and pulse. If they can be powered by animal body heat, then there is no need for battery replacement.

Simple Enough for Everyone

Energy harvesting technology is the key behind the popularity of wireless sensor network, and with continuing development and wider recognition, a host of new applications will no doubt be pioneered. One major change in the environment is that companies getting into the energy harvesting field can now pick up low-power peripheral components very easily.

A large number of generating devices are already available from companies like AdaptivEnergy LLC of the US and Perpetuum Ltd. of the UK. For wireless technology, modules on the market eliminate the need for specialized knowledge of high-frequency waves. Alps Electric Co., Ltd. of Japan, which is volume producing a sensor network module using GainSpan’s wireless transceiver IC, has received inquiries from over thirty firms already.

Japan “A Decade Behind”

While the technology seems to be taking off, there are some worries for Japan: Japanese industry is almost invisible in the field energy harvesting field. Some people in the field warn that Japan is a decade behind Europe and America.

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Powering Up

the Battery-Free World

Though the thermoelectric conversion device is small, the heat exchanger used to attain the high efficiency for a given temperature differential is relatively large. This component is expected to account for the majority of module cost. The heat exchanger is critical in determining electric conversion efficiency, and can as much as double output. Research in this area is sparse, and it is likely to develop into a major battleground for peripheral components.

Expanding Application in Wireless Sensor Networks

Advancement in high-efficiency peripheral circuits and generators with low power consumption has finally made energy harvesting a practical technology. And now that the foundations are in place, the applications are beginning to take shape. The technology is likely to be used diversely, not only in existing switch applications for lighting and such (Fig. 7).

Fig. 7 New Ideas Pioneer New Applications

There is a wide range of possible applications. Especially promising ones include health monitoring for bridges and vehicles, and implementations in animal husbandry and agriculture. (Illustration: Reiko Kusumoto)

One of the most promising applications is wireless sensor networks. Data acquired by the sensors only has to be transmitted a few times an hour, which means power consumption is low. This level is quite possible for an energy harvesting system (Fig. 8).

Fig. 8 New Wireless Sensor Node

The “Mr. Shoene” wireless sensor node released by Seiko Instruments (SII) in Sept. 2010 uses the firm’s proprietary special low-power wireless technology. Power consumption is low and the device is non-directional, making it possible for signals to route around obstacles.

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No Power through

Energy Harvesting:

Powering Up

the Battery-Free World

Stepping Up from only 20mV

Co2 to energy

The impact of higher power supply circuit performance is dramatic, because just how efficiently the power supply can handle the minute trickles of power gained through energy harvesting-how little loss there is-is key. Recently, even ultra-low voltages can be harvested efficiently.

Linear Technology Corp. of the US began volume production of the LTC3108 DC-DC converter, offering relatively high step-up efficiency from even an extremely low 20mV, in December 2009. With a thermocouple, the firm says, it can produce electricity from a temperature difference of only 1°C. An engineer involved in power supply circuit development for years is amazed: “They can use voltages a whole order lower than we can as energy sources!” ^{Note 2)}.

Note 2) The LTC3108 uses an internal n-channel metal oxide semiconductor field effect transistor (MOSFET) with external step-up transformer and capacitor, forming a resonant step-up oscillator. A transformer with a 100:1 ratio would boost 20mV to 2.0V.

According to Tony Armstrong, Director of Product Marketing, Power Products at Linear, the firm began development of the LTC3108 in about the summer of 2007, predicting growth in the energy harvesting field.

Ultra-Low Dissipation Wireless ICs

Lower dissipation by wireless transceiver ICs has also had an enormous effect, along with power supply circuits. Standby dissipation, previously about 1?A, has now been slashed to about 0.2?A thanks to smaller geometry and innovations in communications control.

One company that stands out in the energy harvesting field when it comes to wireless transceiver ICs is venture firm EnOcean GmbH of Germany. The amount of power consumed by the firm’s “EnOcean” standard for wireless communication between equipment is one digit smaller thanother methods.

Fig. 4 EnOcean Emphasizes Low Power Consumption and Ease of Use

The single design means a signal is sent only three times in 30ms (a), helping reduce standby current to only 0.2?A (b). The wavebands used vary by nation and region. Ease of use has been enhanced by modularization (c).

Power consumption was slashed by eliminating unnecessary functionality. Frank Schmidt, Chief Technical Officer (CTO) of the firm, stresses the key is simple control. Wireless ICs used in switch applications, for example, send only three 1ms signals every 30ms for on/off control (Fig. 4) ^{Note 3)}.

Note 3) The latest specification further improved convenience by supporting feedback from the receiver to the transmitter.

There are also efforts under way to apply low-power wireless LAN to energy harvesting wireless communication. GainSpan Corp. of the US, with founders including engineers from Intel Corp. of the US, has developed a wireless LAN IC with a standby current consumption of no more than 1?A: between 10% and 1% of standard designs ^{Note 4)}. This is about the same level as ZigBee. It offers an advantage in that existing wireless LAN access points can be utilized. Standardization has also started on ZigBee Green Power, however, a version of ZigBee tweaked for energy harvesting applications. The standard is expected to be finished by the end of 2010.

Note 4) Lower dissipation was achieved in part by frequent clock gating and use of sleep mode.

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When ecoBiz Participant Australian Country Choice transported goods between their warehouse and factory, their forklift had to travel around the entire factory to reach the adjacent warehouse.

They decided to build a new door in factory next to their warehouse.

This simple measure means the forklift travels a more efficient route, and they are now saving 184 tonnes of forklift gas, equivalent to over 600 tonnes of greenhouse gas, each year!

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