This article is the second part of the overview of Keynote presentations at Energy Harvesting USA 2011 conference held in Boston, MA last week.
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 strain 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 ponts 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.