This article gives an overview of the Keynote presentations at Energy Harvesting & Storage and Wireless Sensor Networks & RTLS USA 2011 conference held in Boston, MA last week. Leading innovators and adopters of energy harvesting and wireless sensor technologies discussed solutions, challenges and needs that will promote further adoption of energy harvesting in different verticals.
Ford - Volvo
After Raghu Das opened the conference with an overview of the state of the energy harvesting market in 2011 and its forecasted growth, Clay Maranville from the FORD Motor Company provided attendees with a range of considerations that guided FORD through the development of thermoelectric generators for their vehicles, looking at waste heat recovery as part of the company’s strategy on sustainable transportation.
Energy efficient transportation is becoming more and more imperative, both due to the increasing number of vehicles (car ownership in china is expected to reach 230M by 2030) as well as the increasing price of fossil fuels, making the development of ways to decrease wasted energy a necessity, both from an economic as well as an environmental standpoint.
Reducing total fuel consumption, weight and cost compared to an alternator/battery system would be the ideal way to implement thermoelectric energy generation. Replacing the alternator completely is a very challenging approach though so, at this point, supplementing it is a much more viable option. Recovering waste heat without interfering with the rest of the systems on the vehicle was a central development consideration and results on a vehicle demonstrated the recovery of around 275W at cruising speed.
Clay also briefly touched on wireless vehicle sensors, with considerations including the potential elimination of 1500 different types of wires, (over 4km in length, 40kg in weight) with reduced cost, weight and improved long term durability wireless solutions.
Michael Balthasar from the Volvo Group continued in a similar vein, focusing more on commercial vehicles rather than passenger cars, where fuel efficiency is also a top priority. The thermodynamic Rankine cycle approach is currently preferred due to higher efficiencies but thermoelectric generation is also important, where considerations at Volvo include lower cost, higher efficiency, and use of non-toxic materials. Such developments would make thermoelectric generation a preferred option.
Cost considerations are also important in the wireless sensors space, making sure that product, manufacturing as well as development & maintenance costs are reduced. Signal interference and cross communication have to be avoided at all costs and equally importantly, security of wireless communications is a high priority, making sure it is implemented with minimal energy consumption.
The Marketing Store
On a totally different sector, Warren Kronberger from The Marketing Store discussed the interest in the energy harvesting space from the perspective of a marketing company. Promotional toys incorporating electronics and interior design furniture are some of the types of products available from The Marketing Store that would benefit from energy harvesting technologies. Some of the bespoke toys incorporate proximity and sound sensors, currently utilizing batteries but energy harvesting could potentially lead to an enhanced role playing experience. Some interactive electronic toys (first introduced in 2003) are at times deployed in very large volumes of over 30,000,000 units in the space of a month and so, the overall opportunity in terms of harvesters necessary could be significant. For adults, harvesting ambient energy would make sense in retail applications, in order to power products incorporating interactive elements in their packaging, POP and window displays and signage or even incorporated into components of the final product. Warren also commented that safety concerns are quite relevant in this space, due to the close proximity and increased interaction of the consumer with these types of products (e.g. avoiding lead and other toxic materials, the disposal of electronic waste).
Dr Kars Michiel Lenssen from Philips Research Laboratories discussed electronic skin development, in collaboration with HP, and its power requirements in autonomous devices. Electronic skin describes the change of the appearance of surfaces electronically and remotely, with large size examples including smart windows and electronic wall paper(managing lighting, privacy, temperature, etc). In principle this application sounds very interesting but consumers become less enthusiastic when being faced with the potential of many more wires/cables and increased electricity bills. Hence, energy harvesting and wireless solutions are the main type of approach that would make sense in this space. Electrophoretic displays are one approach, being able to easily control transmission rates from 0 to 70% with 5 levels of grayscale in between with low power consumption (zero power consumed to maintain dark state, nanoWatts to maintain transparent state, milliWatts during changing states). The size of implementation ranges from portable electronics personalization all the way to potentially changing the colour of one’s entire home depending on weather conditions and whether one would desire to keep a building warmer or cooler.
Dr Lenssen also announced for the first time HP’s development of a different technology, based on electrokinetics. The electrokinetic panels are manufactured on a roll to roll process and can also operate with very little power provided, whether by indoor PV or RF power.
Georgia Institute of Technology
Professor Manos Tentzeris discussed the main foci of research at Georgia tech, including long range wireless power transfer (5-6 miles) as well as multiple mode energy harvesting and electronic skin applications.
The research group’s work on wireless sensor nodes follows a “three in one” approach, developing sensors, communication as well as power, integrating high efficiency nanotechnologies as well as low cost substrates. Paper electronics is one of the low cost substrate approaches, with examples such as RFID inkjet printed on paper. The substrate can be made hydrophobic (can be washed, rained upon) with 20 micron inkjet accuracy.
Inkjet-printed carbon nanotubes have been studied and used as gas sensors due to their high sensitivity to nitrogen, allowing to detect ammonia, nitrogen compounds etc), with applications including efforts to develop ways to stopping leakages before they become catastrophic.
The prolific group has also demonstrated solar smart skin for structural health monitoring, powering strai gauges and has shown how broadband RF harvesting can produce useful amounts of power, whereas narrowband gives very little power.
One Laptop Per Child (OLPC) - Infinite Power Solutions (IPS)
Richard Smith discussed the main needs of the highly ambitious project, and its charitable efforts to provide children all over the world with the necessary tools to promote education and opportunities even where availability of resources is scarce. Low power requirements, fault tolerance and robustness as well as mostly inexpensive devices (although current devices need to get to lower price point), with sunlight readable display are some of the main points Richard made during his presentation. OLPC has produced 2.2 million laptops since 2006, mostly deployed in Latin America. The 3rd generation of laptops goes into production in 2012 and there’s a tablet device under design as well.
Off grid power remains a challenge as there is no “one size fits all” solution at different sites, different environments, cultures, social requirements (e.g. Mongolia vs Kenya). Options discussed included:
Hand crank: one option that becomes feasible with the third generation of devices.
Madagascar’s waterwheel: In this set up, a 3KW turbine, is used. A water pool that fills up during the day powers the turbine during the night by hosing out the water from the pool onto it. The set up provides power for the village and part of it goes to powering OLPC laptops.
India’s cow power: In India, where there are no wind turbines, solar cells are expensive and there are no rivers set ups have been developed where cows provide power for dynamos.
Since for the developing world, the size of a laptop battery is meaningless - as Richard said during his presentation “How big does your battery have to be if there is no place to plug it in?”- opportunistic charging is the way forward: high charge rate, low power draw and being humanly feasible (relying on power you generate yourself) are the three main requirements for it. According to OLPC the ideal ration of charging time over runtime achieved is 1 to 10: 10 minutes charging for 100 minutes of runtime. That’s the kind of device the charity is working towards.
Infinite Power Solutions closed the keynote sessions with an overview of the ways the company is implementing complete solutions to energy harvesting requirements for further deployment of wireless sensor networks. The company’s proprietary solid state battery technology, the Thinergy Micro-energy Cells, along with collaborative work with leading low power electronics companies and energy harvester developers has led to a multitude of demonstrators that were showcased at the conference and tradeshow. During the IPS presentation, Mr Joe Keating discussed the topic of optimization of DC to DC buck conversion, in order to get the maximum possible energy out of storage cells.