EPSRC Energy Harvesting Network

EH Network Blog

The EH Network blog is updated with regular postings from international experts in Energy Harvesting. If you are interested in posting a blog entry, we would be delighted to hear from you - please email info@eh-network.org for further information.

Funding competition to support energy harvesting for autonomous sensing

Date of Entry: 10 Oct 2012
Authored by: Simon Aliwell, Zartech Ltd,

The UK's Technology Strategy Board has made available one million pounds for a series of collaborative projects on energy harvesting for autonomous sensing. The aim is to support demonstration of low power energy harvesting in new and challenging real world applications, the exploration of novel energy harvesting techniques for practical use and the potential to improve harvesting through developments in areas such as power management systems.

This is the perfect opportunity for companies whose sensing solutions are limited by the lifetime and reliability issues of batteries to evaluate whether energy harvesting might be a solution for their particular applications. The application process is simple (single stage) and quick and the competition is designed to allow those needing to address powering of autonomous sensors to access energy harvesting expertise.

The projects are expected to last 6-18 months and can attract public funding of up to 75% with a maximum grant of £100k for an individual project. They must be industry led and have at least two collaborating partners. There is plenty of energy harvesting expertise in the UK that could help companies assess the potential of the technology. There are several of the world's leading academic groups with practical experience in energy harvesting systems development and deployment, a number of technology consultancies with relevant experience and a small number of companies that sell either energy harvesting systems or components.

To find out more about the competition please refer to the briefing document.

The official Technology Strategy Board call briefing event is on 23 October 2012 in London or alternatively there is a webinar on the same date.

A series of regional workshops have been organised by the Knowledge Transfer Networks to promote the call and to help organisations explore ideas and find partners. Details of these can be found here.

The Energy Harvesting Network can also act as 'broker', putting interested parties in contact with potenital industrial and/or academic collaborators. To take advantage of this service, please email info@eh-network.org.

To stay informed on further competitions, events and other developments in the field we recommend that you join the Technology Strategy Board's Energy Harvesting Special Interest Group. This and the Energy Harvesting Network are both good sources of information on potential partners to provide the necessary energy harvesting expertise for your project.

Highlights of Energy Harvesting & Storage Europe 2012

Date of Entry: 21 May 2012
Authored by: Simon Aliwell, Zartech Ltd, Costis Kompis, Vodera Ltd,

Ever since we wrote the study 'Energy Harvesting for Remote and Wireless Sensing' back in 2008 we have made a point of keeping an eye on developments in the field. The study is available to download by clicking here. It has been interesting to follow the successes of some and the ongoing development challenges of others. Many of the issues and challenges remain the same. We attended last week's IDTechEx conference, Energy Harvesting & Storage Europe in Berlin so have provided some highlights below. Hopefully these will provide the reader with some leads for further investigation in their particular areas of interest.

The conference itself was, as usual, well organised and attracted a good crowd of around 300 delegates. The programme covered a range of topics from end user needs through to technology solutions. It is worth bearing in mind that this is a commercial conference. This was reflected in some of the talks being a bit too much of a sales pitch and revealing nothing of any significance on how performance was achieved. In an emerging technology area that is still trying to establish credibility this seems a shortsighted approach by some of the companies. The exhibition part of the conference was excellent and probably the highlight of the programme for us - a great opportunity to quiz companies in more detail and see some concrete demonstration of energy harvesting in action. This is the 3rd year in a row that the conference has been held in Germany. This has taken advantage of the concentration of energy harvesting expertise in the country but it may be time to move to another country now to access a new crowd.

User needs and experiences

We are always keen to hear the views of potential end users of energy harvesting technology. Their interest and efforts to explore the possibilities is a good indicator of the health of the sector and progress in demonstrating real benefit. Somewhat disappointingly there were no real indications of new applications or sectors - the usual sectors of automotive, aerospace, industrial machinery and smart buildings seem set to continue to dominate. In addition, in most sectors outside of smart buildings, the technology still appears to be at the demonstrator stage with volume sales yet to take off.

Volvo, the truck and bus company rather than the car company, gave an excellent account of the potential for energy harvesting and the challenges to be overcome. There were some very clear messages on the cost savings in all manner of areas from fuel consumption, manufacturing costs and workshop time but also some caveats in terms of the need to deal with a conservative business, long product cycles and the need for safety critical systems. Encryption of wireless signals was also highlighted as key to prevent vehicle hacking and packaging to survive harsh environments and protect against ingress of water and dust is important. Amongst the wish list of requirements were auto grade components, complete assemblies, high volume and low costs and the development of low power sensor communications standards for safety critical systems. Volvo have two energy harvesting demonstrators planned for the end of the year.

ABB presented on integrated and modular energy harvesting solutions for the process industry. Their interests appear to cover everything from field instrumentation to condition monitoring of machines, motors and power products. They have looked at kinetic, thermal and photovoltaic harvesting and have been field trialing solutions. There is a particular interest in true broadband vibrational harvesters should these become available. Intrinsic safety was highlighted as a critical need for some applications.

TRW Conekt presented on the needs of both the automotive and aerospace sectors. There were clearly a number of similarities between the two in terms of operating environment but some key differences include acceptable cost and regulation. In the automotive sector, particularly for tire pressure monitoring, it would appear that energy harvesting needs to become cheaper than batteries. In aerospace it is much less price sensitive as whole life costs are considered. Certification for automotive applications is by regional approval but for aerospace is worldwide. The case was made that holistic integrated design of hardware, software and power sources is required for optimum performance. The question was raised as to whether or not we have arrived at the right low power radio protocols yet noting that the most successful systems so far have tended to use proprietary protocols.

Product innovation

There were also a number of interesting technical developments presented in the area of product innovation.

A novel use of thermal energy harvesting was presented by MSX Technology. They are using a wireless acoustic sensor to keep a cooking pot at simmer temperature by detecting the formation of steam bubbles. The feedback wirelessly to the hob sensor control allows better control of heat and therefore significantly reduced waste heat. This has been pitched as a low cost solution with thermal harvesters supplied by Micropelt. Their hope is that demand will be driven by new EC directives on energy saving.

Micropelt and Texas Instruments have been working together and have developed a new microcontroller platform for condition monitoring sensors with local intelligence. They claim to enable lean wireless sensor networks powered by TI's new Ferroelectric RAM MCU and Micropelt's embedded thermo-harvesting power modules. The Wolverine platform claims to cut power consumption in half compared to the competition setting new standards for energy efficiency in microcontrollers.

G24 Innovations described their dye sensitized cells as the world's most powerful indoor photovoltaic modules claiming better efficiency than amorphous silicon and increasing efficiency with increased temperature (Si-based solutions have problems with reduced efficiency in hot climates). The advantages of flexibility of the cells and having the option of different colours will suit some applications. Several applications from electronic shelf labels, a wireless Bluetooth keyboard (developed with Logitech) and wireless blind and shade systems were described. Production capacity has been ramped up and a second line is in place and ready for commissioning. G24i claim a cost per kW/hr of $37 compared to that of $128-180 for batteries.

Solar Print and Analog Devices presented together on their glass dye sensitised cell solution for powering wireless networks.

The Fraunhofer IZM presented on the development of a prototype power supply for a Bluetooth music headset ski helmet with glove control using solar power. Most focus appeared to be on how to integrate high efficiency crystalline silicon cells into bendable modules for fitting to curved surfaces.

Technology developments

It was interesting to hear of developments in East Asia as these often get ignored in the usual focus on the traditionally strong energy harvesting centres in Europe and the USA. Hanyang University in South Korea has been carrying out feasibility studies on using piezoelectric energy harvesting. Case studies included using a waterflow driven propeller impacting a piezo strip to light up over 1,000 LEDs. Vibration in a Maglev train was harvested using a design that incorporated a box of 'bouncing' steel balls on top of a piezoelectric base. A further high-speed train application assessed vibrational energy available at various points in the cabin. The National Institute of Advanced Industrial Science and Technology (AIST) in Japan described thermoelectric conversion films fabricated through printing processes. They have developed new materials, a carbon nanotube-polymer composite with high thermoelectric conversion characteristics (a ZT of around 0.1) so avoiding the issues of high cost rare bismuth and tellurium. They have also developed suitable fabrication processes to produce large area flexible and low cost devices. They appeared to be targeting quite high temperature differentials getting several hundred microwatts per square centimeter off of a differential of 100 degrees. Questions of durability to high temperature breakdown were a concern although it was claimed that suitable polymer selection would address this. IBULE Photonics of Korea have developed a piezo generator based on a PMN-PT single crystal instead of the usual PZT material. The material is lead magnesium niobium along with lead titanium for the piezoelectricity giving a claimed 3x higher piezoelectric mechanical stress.

There was a good cluster of presentations on heat energy harvesting with some new technologies or advances in production capability.

Nextreme described their microscale thin film thermoelectric technology and high volume semiconductor manufacturing processes. They made the very strong case that the predicted large markets ($6bn by 2020) for thermoelectric devices will require very substantial cost reductions and widespread wireless sensor network deployment. Their process uses 400x less Te than conventional TEGs and this could become key with the trend to rapidly increasing Te costs. Interesting practical solutions e.g. harvesting off the hot and cold pipes under a sink or on the waste trap as well as turbine bearing condition monitoring were described.

ST Microelectronics described a completely new thermal harvesting approach using bimetals which snap up and down around specific pre-defined temperatures. A significant potential advantage is that the devices would be able to work without the need for a heatsink - usually a rather bulky element of a thermal energy harvester. The harvesting devices are constructed by combining the bimetal with a piezoelectric material in a shock layout or by direct patterning of the bimetal on the piezoelectric. The snap temperature does not change with scale and scaling laws seem to work in favour of scaling down in size - several small matrixed bimetals can replace one large on resulting in increases in power and be surface and shape adaptive at the same time. Concerns of fatigue lifetime were claimed to not be a problem having demonstrated thousands of cycles although this may still not address the issue of lifetime of the piezoelectric components. It was also claimed that the matrixed approach could be used to address different temperature ranges in a single device by coupling bimetal with different snap temperatures.

Marlow Industries also covered thermal energy harvesting and power management but the presentation was more tutorial in style so did not reveal much detail on their own developments.

Piezoelectric energy harvesting received a fair bit of attention this year.

Arveni work in the area of mechanical push button or vibration energy harvesting and their key USP appears to be a very high claimed conversion efficiency (some 13x better than their competition). No information was however supplied to explain how this was achieved. They demonstrated their usual batteryless TV remote control based on 2-way radio developed for Philips. This is still a prototype rather than having started achieving product sales. Arveni now also appear to be working on using their technology for powering industrial wireless sensor networks.

Meggitt Sensing Systems talked about the performance of fully integrated vibrational energy harvesters based on PZT. They have taken a thick film manufacturing approach by screen-printing on micro-machined silicon cantilevers. Through their internal spin-off company, InSensor, they offer various mass-beam geometries including unimorphs and bimorphs and can manufacture in high volumes. Their focus would appear to be devices that are designed to operate with relatively modest acceleration levels achieving something like 15-20 microwatts at 0.5g.

One of the main criticisms of piezoelectric materials is their brittle nature that results in failure after repeated bending. Algra have come up with a piezoelectric switch design that works without displacement. Greater than 5N pressure on the piezoelectric material is sufficient to activate the device as a handheld remote control. The use of a laminated multilayer casing with support rather than clamping for the piezo layer appears to be an important aspect of the design. It has been applied to light switching, garage door openers and other home automation applications. Further applications are envisaged in push stop buttons on buses, batteryless pH meters, e-ink display, various industrial push buttons etc.

Low power electronics and energy management was also a major area of focus.

Infinite Power Solutions, well known for their THINERGY Micro-energy thin film rechargeable cells, made the case that Bluetooth Low Energy is the protocol to enable personal sensor networks that are powered using energy harvesting. The claim is that it can increase battery run time up to 10x over traditional sensor network protocols.

Imperial College London focused on power electronic interfaces for energy harvesting devices. They criticised the approach of many researchers in measuring the power output of EH devices. Three research questions relating to power conditioning, adaptability (improving electromagnetic coupling of piezoelectric harvesters) and damper strength (electronics tuning of resonant harvesters) were highlighted with some (at least partial) solutions suggested.

There were a number of presentations on microcontrollers addressing various issues. Anagear presented a new controller for smart power management in both battery supplied and self-powered wireless sensor nodes. It was claimed that this could provide a solution to the 'cold start' problem. The circuit is in prototype form with manufacturing expected shortly. Microchip presented another family of microcontrollers that can operate with as low as 45uA/MHz at 3V. Energy Micro presented on a new 32Bit microcontroller claimed to be the world's most efficient at 32bit. By taking an industry standard ARM Cortex-M3 processor and integrating modules they have managed to increase its power efficiency by a factor of 4. The microcontroller is provided as a developer toolkit.

There were also a series of presentations that related more to the wireless sensor network aspects than energy harvesting itself.

Libelium described some quite largescale wireless sensor network deployments (up to 1,000 nodes) in a smart cities project. They have been taking a horizontal and modular approach and can accommodate over 60 sensors and interface all key protocols (ZigBee, Bluetooth, 3G, GPRS).

Linear Technology / Dust Networks claimed that the two major WSN challenges (battery lifetime and reliability) are no longer an issue. By using time synchronised channel hopping battery lifetime can be extended to 5-10 years and reliability to 99.99% for a network that has 50 motes, 7 hops over 3 floors exchanging 100,000 packets a day. With regards larger deployments, examples were given e.g. a 700 acre oil refinery of Chevron instrumented by Emerson. Also it was reported that NTT was able to cut significantly the energy costs in their data centres. They praised the arrival of WirelessHART.

EnOcean, who have developed their own ultralow power radio protocol and a very successful ecosystem of smart building product suppliers around this standard, addressed issues of security in their early systems. A rolling code has been proposed to offer fraud resistance against reply attacks. Encryption has been added as a protection against eavesdroppers.

Wibicom, a small technical consulting company in the field of wireless communications showed 'WibiSol' a concept antenna with an integrated dye sensitised cell which harvests energy from ambient light or the sun and simultaneously transmits and receives RF signals.

Poster sessions

There was more representation of the academic community in the poster sessions with academic groups from across Europe including Germany, UK, Sweden, France, Czech Rep., Poland, Latvia, Italy and Belgium presenting. The posters covered mainly basic research but several also had a clear focus on applications of energy harvesting. Some highlights include:

Riga Technical University, Latvia featured flat inductors for energy harvesting, investigated the creation of electromagnetic harvesters with flat architecture and evaluated their performance. The key advantage of such design is avoiding a rigid construction for the harvester, where an empty space for the magnet's motion must be ensured. The ultimate goal is to use such harvesters in wearable systems integrated in clothes. Theoretical results for 3 shapes (square, rhombic and circumference) of inductors were compared.

Newcastle University, UK presented a range of on-chip solutions for voltage sensing and voltage monitoring. Their work is motivated by the need to have non-invasive operations. Their voltage sensors and monitors avoid using conventional analogue to digital converters that are power costly, slow and occupy a large area. The proposed sensing method is based on sampling energy into storage and mapping this energy into a code. The implementation uses elastic digital circuits leading to a low energy solution because they only consume power when they actively perform conversions. Using UMC 90nm technology node the conversion time was 1.2us, the dynamic power consumption 76uW with cell leakage power 7uW.

Universita degli Studi di Modena e Reggio Emilia, Italy presented an autonomous wireless sensor to enhance safety in vehicles equipped with tow bars by taking into account if a trailer is connected to the vehicle. Overturning vehicles lead to preventable fatal accidents. The device scavenges energy from the vehicle's vibration using a piezoelectric module. Data are transmitted to the stability control algorithm running on the vehicles ECU so as to dynamically adjust the vehicle's model parameters to consider the current real operative conditions.

Cranfield University, UK presented the advances in self-powered wireless sensor nodes for structural health monitoring. The system is designed to harvest energy from wing vibrations of aircraft in active service and should be able to use that energy to measure aircraft wing fatigue and inflight loading. The system features a novel piezoelectric harvester based on a macro-fibre composite. A patent pending solution integrates impedance matching, power management and smart switching. The power harvested is 1.8-12mW at 1-10Hz and 230-570 uStrain representing one of the best performances reported.

The Best Poster award was given to Erasmus University College, Belgium for the topic Ambient Energy Powered Smart Meters. The poster presented initial yet promising results on a micro-turbine based energy harvester that could be added to water pipes in order to autonomously measure and transmit to the utility companies the amount of water used. The authors had used a 3D printer to produce models of the turbine and compared several ways to retrofit them on existing water pipe installations.

And that folks is the highlights as we saw them. If there are any inaccuracies in the above please feel free to let us know. If you would like to know more about what is reported here or would just like some help in finding out more about energy harvesting in general do get in touch.

Simon Aliwell: simon.aliwell@zartech.co.uk
Costis Kompis: costis.kompis@vodera.com

This report is also available to download as a pdf.

Batteries Not Enough - A Case for Energy Harvesting

Date of Entry: 13 Oct 2011
Authored by: Simon Aliwell, Zartech Ltd,

A common question when considering energy harvesting solutions to wireless powering of devices is: "...why can't we just use batteries? Surely with batteries lasting longer these days, being energy dense and being cheap these will do nicely."

Batteries, however, have three major limitations:

- Reliability
- Environmental impact
- Lifetime and cost of changing

There are a number of areas where the use of batteries to power wireless devices, often sensors of one sort or another, is impractical because batteries do not provide a high enough level of reliability. A typical cause of this will be high environmental temperatures. In industrial sensing situations there are therefore applications where and energy harvesting solution provides the missing reliability. These will tend to be high value but often niche applications.

The widespread use of batteries has created many environmental concerns, such as toxic metal pollution. Battery manufacture consumes resources and often involves hazardous chemicals. Used batteries also contribute to electronic waste. Any developments that lead to the proliferation of batteries is therefore likely to lead to enormous environmental concern.

Whilst many batteries are rated for a typically 3 year and sometimes up to 10 years lifetime, the reality is that in most real world applications they last significantly less, often months rather than years. Lifetime is dependent upon both the duty cycle of the tasks to be powered and on the environmental conditions under which this happens. Even if never taken out of the original package, primary batteries can lose 8 to 20 percent of their original charge every year at a temperature of about 20-30 degrees C by self discharge. Newer chemistry and modern lithium designs have reduced the self-discharge rate of rechargeable batteries to a relatively low level (but still poorer than for primary batteries). Start making the battery do some intermittent work and this lifetime reduces drastically making battery change a necessity in almost all applications. This is by far the biggest argument for energy harvesting.

This is an issue for those niche applications with wireless sensor nodes placed in hard-to-reach locations (e.g. inhospitable and remote or hazardous industrial environments or even medically implantable devices) making the changing of batteries regularly both costly and inconvenient.

However, it is also an issue on a massively larger scale for pretty mundane applications where the access to the batteries is perhaps not difficult due to remoteness but is nevertheless impractical or expensive. Where EH will come into its own is in powering all of those applications where battery change is just inconvenient due to a combination of cost and volume of such changes and the unpredictability of battery lifetime.

For example, EnOcean, a German energy harvesting company, already have energy harvesting powered solutions in >100,000 buildings. These include light switches, temperature controls, window contact sensors, lighting control - all elements of a smart building which enable them to produce an average annual energy savings of 60%. In just one example they have installed 4200 wireless and battery-less light switches, occupancy sensors and daylight sensors in a new building construction in Madrid. These are powered by energy harvesters and embedded in the building. This saved 40% of lighting energy costs by automatically controlling the lighting in the building, removed the need for 20 miles of cables, avoided the use and changing of 42,000 batteries (over 25 years) and saved 80% of the cost of retrofitting a wired solution.

Even more mundane is the example of US energy harvesting company that was approached by a company that runs the toilets in various public buildings e.g. airports. This company has a problem with the taps that use infrared sensors to detect hands and switch on water. Evidently they regularly stop working as they exhaust the 3 cell batteries that power them generally in around 3 months. Every time one of those taps goes down they get a call and have to send in a qualified plumber to scrabble under the sink and change the battery at a reported cost of $75 a time. There are undoubtedly countless other trivial examples that aren't about hazardous areas, deep sea, underground access, just inconvenient and expensive to change batteries due to who can or will change them. Another example would be the need that hotel chains have to periodically go around changing batteries on the key cars door locks on its rooms. There are current project investigating energy harvesting solutions based on piezoelectric materials and the pressure of inserting the card. Another simple but elegant solution to the cost of regularly having to go up and deal with door locks with dead batteries.

Texas instruments have developed EH test kits to complement EH suppliers devices and cite the applications in a wide range of areas including remote patient monitoring, efficient office energy control, surveillance and security, agricultural management, home automation, long range asset tracking, implantable sensors, structural monitoring and machinery/equipment monitoring.

So there are already millions of opportunities in currently battery-powered or direct wired devices where energy harvesting could save considerable sums of money in terms of labour. However, the even bigger opportunity is in the so-called 'Internet of Things', an ecosystem of wirelessly connected devices many of which have to be mobile and/or inaccessible for battery change. Cisco claim that already by 2010 the IoT contained 12.5bn connected devices, that by 2015 this will be 25bn and by 2020 it will be 50bn devices.

Cisco predict that as many as one trillion devices will become connected to the Internet. Such connections include sensors on electrical lines to conserve energy, RFID tags attached to shipping crates to track inventory, temperature sensors in lab refrigerators to preserve medical supplies, tiny humidity gauges scattered on a forest floor to assess fire danger, sensors drifting in the ocean to track pollution, or body worn sensors connecting your vital signs to a remote healthcare provider. For IoT to reach its full potential, sensors will need to be self-sustaining. Changing batteries in billions of devices deployed across the planet and even into space is not an option and furthermore the disposal implications of billions of waste batteries is huge. Energy harvesting technologies therefore need to step up with a solution that allows fit and forget powering of the device.

Applying Energy Harvesters to Textiles

Date of Entry: 08 Apr 2011
Authored by:

Energy harvesters enabling micro-power generation provide new levels of efficiency and automation in the built environment, process control, vehicles and healthcare. However, recently a large effort is being placed into developing the technology for integration into textiles. While on the surface this may seem niche, if we delve deeper we find there is a substantial opportunity for the technology here. Textiles are the most common human interface because 70% of surfaces touched each day are textiles, including clothes, bedding, wall covering, upholstery and flooring. Textiles are flexible, comfortable and consumer oriented. They are stretchable and conformable and they present large surface areas to work with. They are highly engineered and ordered structures produced by an established, efficient, global supply chain and a mass volume application platform.

Textile electronics is primarily used for sensing as in health monitoring, warming as in outdoor wear, display and lighting including illuminating t-shirts and party fashions and control as with sleeve controls for your iPod and woven rollable keyboards. Then there is logistics, notably RFID. That includes active RFID where there is a battery in the tag for real time location, mesh networking and so on. These batteries will have energy harvesting in future. Beyond clothing, the technology is being integrated into car and train seats. For example, EnOcean energy harvesters are used to monitor occupancy of seats in trains so that operators can judge when to add or remove carriages. The sensors are powered by the act of someone sitting on the seat.

Energy Harvesting and Sportswear

Adidas is moving forward with products such as the virtual trainer. Their subsidiary Textronics focuses exclusively on textile electronics, specifically Wearable Physiological Monitoring Systems. Here the vision is to easily measure body data to help the consumer manage health and wellness goals.

At Europe's largest event on Energy Harvesting & Storage (Munich, Germany June 21-22 http://www.IDTechEx.com/EHEurope), Decathlon (owned by Oxylane Group) will present on the opportunity for energy harvesting for electronics sports products. The presentation will cover energy requirements and user needs and requirements for energy harvesting products.

The Textile Becomes the Energy Harvester

Increasingly researchers are turning their attention to incorporating the energy harvesting elements into the textile itself. In the UK the University of Bolton has developed a novel technology that integrates piezoelectric polymer substrate and photovoltaic coating system to create a film or fibre structure that is capable of harvesting energy from nature, including sun, rain, wind, wave and tide.

The raw materials used are inexpensive starting with the piezoelectric material which is extruded and poled. Since the organic photovoltaic material system is made in a normal atmospheric environment, the cost associated with the whole structure is magnitudes less expensive than ceramic based photovoltaic. The resultant material system is flexible and can be incorporated in textiles for a wide variety of applications. The University will also be presenting at this event.

Researchers at the University of Southampton's School of Electronics and Computer Science (ECS) are developing technology that may enable people to power electronics through their clothes and the carpets they walk on. Dr Steve Beeby and his team aim to generate energy through people's movement, eliminating the need to change batteries on devices. In a project funded by the Engineering and Physical Sciences Research Council (EPSRC), the Southampton team will use rapid printing processes and active printed inks to create an energy harvesting film in textiles. This film can also be printed on carpets, enabling individuals to generate energy as they walk around the home or office.

In the US, Georgia Tech researchers led by materials-science Professor Zhong Lin Wang have made a flexible fiber coated with zinc oxide nanowires that can convert mechanical energy into electricity. The researchers say the fibers should be able to harvest any kind of vibration or motion for electric current. Gold-plated zinc oxide nanowires, each about 3.5 micrometers tall, are grown on a flexible polymer fiber and these nanowires brush against untreated nanowires, which flex and generate current. Yarn spun from the fibers could lead to fabrics that convert body movements into electric current.

Cetemmsa is another company overseeing research projects in the use of sensors in sportswear and accessories. The company hopes to develop a range of electronics that can be integrated into clothing which could appeal to athletes, including heart rate monitors, cooling technology and low-power lighting solutions. The company is also working on integrated power sources for added electronic functionality such as organic photovoltaics, as part of the EU-funded Dephotex project. Dephotex is a European collaborative research project, co-funded by the European Commission and will be carrying out research on Photovoltaic Textiles based on novel Fibres for 3 years from November 2008 to October 2011. Cetemmsa will be presenting on this at the IDTechEx Energy Harvesting & Storage event.

Solarprint, G24i and Konarka will also present on Photovoltaics, including covering new form factors of PV applicable to textiles. The IDTechEx "Energy Harvesting & Storage" event brings the whole topic together, exploring new leading edge work in sectors such as textiles. Register early to obtain the discount at http://www.IDTechEx.com/EHEurope.

IDTechEx event: Energy Harvesting & Storage Europe and Wireless Sensor Networks & RTLS 2010

Date of Entry: 20 Jul 2010
Authored by: Steve Beeby, University of Southampton,

Munich seems to be the place for energy harvesting events with the IDTechEx event Energy Harvesting & Storage Europe and Wireless Sensor Networks & RTLS 2010 being held there on the 26th & 27th May.

This was a successful event with just under 250 delegates. The plenary talks successfully addressed the challenges faced when combining energy harvesting and wireless sensors in different practical environments. A good example of this was the presentation by Thomas Becker from EADS who posed the question: do we need energy harvesting and wireless sensor networks in aeronautical applications? Thomas provided clear motivation for such systems, namely decreased maintenance effort and increased lifetime of aircraft, but also highlighted the challenging requirements particular to the application. For the wireless aspect, the network would require certification and need to be totally reliable. The environment was very challenging with temperatures ranging from -55 to +85 oC, plus humidity variations, icing, exposure to hydraulic fluids, structural aging effects and vibrations. The system would be expected to work for a lifetime of 30 years. EADS has evaluated various types of energy harvesting. Vibration energy harvesting in rotor craft has been demonstrated obtaining mW of power from 17 Hz vibrations. On fixed wing aircraft, thermoelectric harvesting appears more attractive but issues remain regarding their successful integration and no solution is expected within the next 5 years.

Haydn Thompson from Rolls Royce continued the theme with a talk on self powered wireless sensors. The environment within an aero-engine is clearly even more challenging than the standard aeronautical specification with temperature variations ranging from -55 to 1300 oC! The potential for energy harvesting is clear - batteries are okay for test be applications but are totally unsuitable for production systems where there is plenty of vibration and thermal energy available to be harvested. Both vibration and thermal energy harvesting had been demonstrated with 100 mW and 200 mW being demonstrated form each approach respectively. The size of the energy harvesters remains an issue and much work remains to be done to develop harvesters for this application.

Other interesting talks on energy harvesting included a presentation from Pavegen Systems Ltd who have developed an energy harvester than looks like a conventional paving slab but that is able to develop between 2 and 3.75 W from an average footfall. They are seeking to licence the technology to act as a localised power supply for low level lighting and operation of systems at bus stops for example.

After the plenaries there were two parallel streams on energy harvesting and wireless sensor networks and an exhibition from various organisations and companies involved in energy harvesting. These included presentations form Microstrain, Cranfield University, University of Southampton, US Space and Naval Warfare Systems Command (SPAWAR), EnOcean, IMEC Holst Centre, Arveni, Humdinger and Meggit Ferroperm. These talks focused on the more technical issues relating to energy harvesting including aspects of piezoelectric vibration energy harvesters, MEMS implementations, increasing vibration bandwidth and thermoelectric energy harvesting. The talk from Cranfield on modelling of piezoelectric energy harvesting was, for me at least, very interesting. They have successfully modelled piezoelectric harvesters using ANSYS and we at Southampton have benefited from this research which has improved the accuracy of our simulations. The talk from Humdinger was on the novel topic of energy harvesting from airflows by exploiting aeroelastic flutter. They have developed a small harvester able to harvest about 1% of the wind energy obtaining 200 micro Watts at 3.5 m/s airflows. The research into MEMS energy harvesters mentioned at this conference was technically interesting but, as is often the case, felt like investigating solutions without a problem. The laws of physics do not favour microscale vibration energy harvesting and applications for low power, high frequency, albeit small, harvesters are not yet obvious. As power requirements fall and MEMS technology and materials evolve I'm hopeful this won't remain the case.

The next two energy harvesting events organised by IDTechEx will be held on the 13-14 October in Hong Kong and 16-17 November in Boston. A discounted rate will be available to Network members and further details will be available on the website.

Energy Harvesting for Wireless Automation

Date of Entry: 29 Mar 2010
Authored by: Simon Aliwell, Zartech Ltd,

I attended the above-named conference in Munich last week (24th and 25th March) and I have outlined below a few top-level things I took away.

On the conference itself, this was a relatively small event with around 60 delegates and very much focused on the practical end of energy harvesting. This meant a predominantly industrial audience and a focus on the here and now of application. The small size also ensured a good networking opportunity. I found it very useful for gauging the state of development since a study we published in mid 2008.

The development of energy harvesting technology in Europe still appears to be being driven by small companies - the usual suspects e.g. EnOcean, Perpetuum, Micropelt etc. There does however appear to have been a growing interest and involvement by some larger players e.g. Texas Instruments.

It is still only building automation and condition monitoring that have established themselves as viable applications so far. EnOcean have built an impressive market in the former and Perpetuum are establishing sales in the latter. The rest of the industry is still at the stage of R&D or exploring applications and trying to find that combination of volume and value to enable a viable business model.

The aerospace industry has a very real need for energy harvesting but there are some significant technical challenges of operating in such a harsh environment including extremes of temperature, weight, size and concerns about reliability to be overcome as well as finding the right type of energy harvesting for the specific applications. Nevertheless, this sector is relatively price insensitive so does offer hope for a reasonably significant and high value market if the technical issues can be overcome. Work so far has established that there is no one best energy harvesting technology and certainly no multi purpose solution possible.

The impending legislation on tire pressure monitoring in the EU could offer a huge market but indications so far are that the motor industry and legislators do not put a particularly high value on safety, seeking energy harvesting solutions costing cents rather than Euros. This is going to severely restrict the possible solutions.

Efforts to establish standards have certainly moved along in the last year and a half since I paid it much attention. At the level of being able to compare devices and ensure standard interconnection for power sources to wireless sensing devices there appears to have been progress through ISA100. This is about to become more formalised but is certainly heading in the right direction and addresses a significant concern we have heard time and again from end users of the technology. At the level of communications protocols there are two current approaches. The EnOcean Alliance has set a very low power wireless standard designed specifically for the needs of the building automation market. The ZigBee standard has now, with energy harvesting in mind, also been working on a lower power standard. This appears to be much more of a time consuming compromise effort and as such is not as low power as the EnOcean alliance standard but does promise a wider compatibility with other wireless devices in the overall ZigBee family of standards. There were arguments for both approaches and some concern that the EnOcean Alliance standard might not be as open as the ZigBee one. Nevertheless it is hard to argue with well the rapid progess and over 100,000 buildings having EnOcean technology installed and a full supply chain already in existence. I expect it will continue to be a case of horses for courses with each finding its champions for some time to come.

There have certainly been a number of advances in power management over the last 18 months with a number of speakers touching on this topic. It appears to be one of the main factors in driving up the amounts of useful energy made available from energy harvesting devices.

A concern expressed at the conference was that with improvements in battery lifetime outpacing improvements in energy harvesting and its cost reduction the situation where the battery lasts longer than the product it is powering is not far off. In this scenario the case for energy harvesting needs to be more clearly made. This means that consumer goods may not necessarily be the ideal market. We need to be finding those application where the lifetime of the battery is still not enough e.g aerospace and building management where lifetimes of 25 years + are wanted or those applications where environmental conditions are such that batteries can just not be relied upon.

There was an impressive demonstration of the Infinite Power Solutions 'Thinergy' a thin film flexible micro-energy cell rechargeable battery. The size of a large postage stamp and apparently able to handle 20 years plus of use with more than 45,000 charge and full discharge cycles. As the energy storage part of an energy harvesting solution this looks to have enormous potential and some very interesting applications have been demonstrated over the last year or so. It will be interesting to see whether in time this becomes the complementary component that allows energy harvesting to overcome its limitations of intermittency. Definitely one to watch.

Anyway, there was plenty more at this conference so if you need pointing in the direction of particular expertise please get in touch.

If you are interested in energy harvesting generally and particularly in the development of new research challenges in this field I encourage you to join the Energy Harvesting Network at www.eh-network.org.

Next we look forward to 'Energy Harvesting & Storage Europe and Wireless Sensor Networks & RTLS 2010' on 26th & 27th May, again in Munich. We have negotiated a 60 percent discount on this for members of the Sensors & Instrumentation KTN and the Energy Harvesting Network so if you are interested please do get in touch.

Incorrect or outdated information?

Please contact info@eh-network.org if any of information on this page is out-of-date or incorrect.


The data on this page has been contributed by the energy harvesting community. Any views and opinions that are expressed do not necessarily reflect those of the Energy Harvesting Network and, while we strive to provide a reliable resource, we take no responsibility for the accuracy of the information shown.
University of Southampton For comments on the website, please email webmaster@eh-network.org. For general enquiries, please email info@eh-network.org.
Website designed and maintained by Geoff Merrett and Kai Yang. Developed for screen resolutions of 1280x1024 or higher.
Tested with Internet Explorer 8, Mozilla Firefox 3, Google Chrome 3, Apple Safari 4 and Opera 10.