Fascinating power perspectives, all in one place!
Bill Schweber - February 22, 2013
We've all heard the expression "can't see the forest for the trees," when you are so close to a situation that you can’t see the big picture. But I also like to think about when you can't even see the other trees in your area, because you are so focused on the tree at which you are looking.
That's why I make a conscious effort to look at publications outside my immediate interest zone, to get ideas, insight, and new perspectives. I usually do this with the print editions (so-called "dead-tree" versions) because it's actually much faster to browse and graze via print, when you are not looking for a specific answer to a question you already have (plus, it has that carry-it-anywhere, instant-on aspect.) Print is excellent as a random-access, undirected discovery medium for some things; that's all I'll say about print vs. web as information resources here.
One of the publications I read is Defense Tech Briefs, sibling of NASA Tech Briefs, Medical Tech Briefs, among others. The February issue had five interesting power-related items, spanning lab developments, field test, and full production. I thought, "why keep all this good stuff to myself?" and decided to share them with you, with some comments. So here goes (note that online access is free, but you do have to register, which is a very worthwhile tradeoff):
- "Trends in Military System Thermal Management" is a lousy headline for a fascinating article on a new approach to cooling. You are probably familiar with passive approaches using heat sinks, cold plates, and heat pipes, as well as active ones using fans and even pumped fluids. But did you know about annealed pyrolytic graphite (APG), which is encapsulated in a structural shell made from aluminium or copper, for example? It's not just a lab dream; it’s in use in military applications. The article has some solid specifications for key parameters and more.
- "Quantitative Analysis of a Hybrid Electric Humvee for Fuel Economy Improvement" looks at field tests of a military vehicle that was retrofitted as an HEV. Whatever you think about HEVs (or EVs) for average consumers, the military wants fuel economy because fuel is expensive and often dangerous to transport, especially in combat zones. This brief story gave good insight into pros and cons.
- "Looking Under the Hood of a Military Power Supply" is an overview of the requirements for mil-qualified supplies, which are extensive and depend on end-application: operating temperature (of course), shock and vibration, thermal shock, humidity and moisture, EMI, solar radiation. It also looks at some trends in performance and monitoring.
- "Bi-Axial Vibration Energy Harvesting" shows how a harvesting transducer and reporting array can incorporated into an airframe to capture vibrational energy - not an easy challenge, compared to a harvesting-sourced building or bridge monitor.
- "Silicon Heat Pipe Array" is another way to possibly harness the "something special" about silicon. A standard heat pipe uses a metal tube with an internal working fluid, but what if you could make that tube out of silicon? Could you then connect it directly to the die or device of interest? Could you make it in a more thermally efficient geometry? Could you reduce local hot spots on a PC board?
That's it: a quintet of short but readable power-related articles that may get you thinking differently or at least thinking.I'll wager that there are other sources you check regularly, both online and on paper, to keep up with developments of interest outside your immediate niche. Care to tell us what they are?