Authors: Simon Aliwell, Zartech and Costis Kompis, Vodera
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. 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.
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.
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.
Any corrections to the above are welcomed by the authors Simon Aliwell email@example.com and Costis Kompis firstname.lastname@example.org