Large and small fuel-cell charger (via Lilliputain)

Lilliputian Systems has recently announced their partnership with Brookstone (retailers of everything) to sell their portable Silicon Power Cell system that is capable of re-charging just about every mobile device with one butane cartridge, for several weeks at a time. The smaller charger can supposedly handle recharging a smartphone 10 times, and the larger charger can handle 20 times (3W output on both). The portable charger, a little bigger than a pack of cigarettes, houses a chip that takes advantage of a solid oxide fuel cell which converts butane into electricity with only a tiny amount of CO2 and water-vapor as a by-product. Although the internal temperature reaches 750 °C (1380 °F), the heated core is insulated so well that it can be touched. Conveniently, the butane cartridges are about the size of a cigarette lighter and come in various sizes with the smallest being able to provide ten charges before needing to be replaced.

A series of LED’s lets you know what’s happening with the device: Green lets you know your device is charging, Red to let you know your low on fuel, and Blue to inform you that a new cartridge has been inserted and ready to go. The portable charger is equipped with a USB port that allows for just about any mobile device such as phones, tablets, MP3 players and cameras to get a boost when you need it (especially at trade shows). There’s no word yet on the exact MSRP will be, but the charger is rumored to run anywhere from $150 US to $200 with the recyclable recharging butane cartridges going for $2 to $5 US depending on the size. An interesting sidenote is that the company states that you will be able to carry these butane filled chargers on airplanes, but regular lighters are still not allowed. It’s unknown at this time as to exactly when Lilliputian’s Silicon Power Cell will be available , but chances are that it will be out within a few months.

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(Left) Intelligent Textiles showing off their conductive "e-textiles" (Right) Conductive vest, looks exactly like its non-electrical original

Ask any soldier and they’ll tell you that the more gear you use when you ‘kit up’ the harder it is to move. Communication systems like the PRC-153, while smaller than their predecessors, take up a lot of real-estate on plate-carriers and tactical vests alike. Add up all the other electronic gadgets such as GPS units, tactical tablets and NVG systems and you’ll quickly get lost in the cluster that used to be your body-armor. Oh I almost forgot; each one of those ‘cool’ gadgets requires power, and this power usually (9 times out of 10) comes in the form of batteries, lots and lots of batteries.

To help free up some of the clutter and weight associated with these electronics, a UK company called "Intelligent Textiles" has designed an electrically conducive yarn that can be woven into uniforms or body-armor. The ‘e-textile’ allows for power to be transferred from a single battery pack to any location with a plug built-in to the fabric such as helmets, gloves, backpacks, sleeves or pant legs. The company states that even the soldier’s weapon can be outfitted to take advantage of the fabric and future versions will even come with a fold-out keyboard. This advanced electrical textile does away with a lot of the cable clutter as well as cutting all the batteries carried down to just one needed to power almost everything the soldier carries.

Intelligent textiles have fielded a prototype for testing purposes future versions will need to be waterproofed so the fabric doesn’t short-out or rust in wet environments. The company is currently in talks with BAE Systems with hopes to have their e-textile uniforms on the field by 2017.

This is not the first to propose conductive thread. A team of researchers assembled from different schools developed a wire with a cotton substrate. Their work was for everyday use, not just for the world's war fighters, thankfully.

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The cockroach fuel-cell volunteer (via ACS Publications)

The living-cell battery from the Matrix movies is real, but not for us humans.

Scientist Daniel Scherson and his team from Case Western Reserve University, Ohio, have take to immobilizing insects and turning them into living fuel-cells. Using a "False Death's Head Cockroach," also know as a discoidalis,  the team was able to insert electrodes made of thin carbon fibers sealing in a glass capillary tube into incisions made in the insect. The biofuel cell using the roach's "trehalose" sugar as a fuel mixed with oxygen to generate electricity. The outcome maxed out at approximately 55 μW/cm² at 0.2 V.

The Trehalose based fuel-cell. "bienzymatic trehalase|glucose oxidase trehalose anode and a bilirubin oxidase dioxygen cathode using Os complexes grafted to a polymeric backbone as electron relays was designed and constructed." (via ACS Publications)

Although the glass tube,  two pins through the pronotum, two more pins the posterior of the abdomen, and a series of staples to hold the cockroach down did no significant damage to the insect's critical organs, we can all assume it was not a pleasant experience for our insect friend. There may be a reprieve for the living creatures on this project. The team was able to achieve similar results with the same procedure on a Shiitake Mushrooms.

The team stated that the goal is to power micro and nano devices with a semi-recharging battery. (ie: The insect eats, and then recharges its core, so to speak.) Research funding was provided by the National Science Foundation. Read about the whole project after the link.

It is a shame that creatures have to suffer so much for our benefit and gain.

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Vertical Turbine (via Eastern Wind Power)

All routes and avenues within renewable energies must be explored, if stopping climate change is the goal. It is no secret that urban areas will be crucial in our conversion. Eastern Wind Power (EWP) is focusing precisely on this gluttonous concentration of energy drains with their new urban wind turbines.

A wife and husband duo with a background in public and construction services put together a team of structural engineers and architects to address environmental issues in the urban setting.

Eastern Wind Power is manufacturing vertical axis wind turbines (VAWT) with the intent of putting them in high-rise buildings where they can exploit high winds. Their biggest turbine is a 50-kW turbine with 20-foot blades and a 15-foot diameter. They hope to set up on rooftops in groups of 10-12 to create “Sky Farms” that can generate 10% of a building’s electrical needs (45,000 kWh/year). The turbine generates power at a low speed of 9.4 mph and shuts down at 90 mph. They are also making a 30-kW turbine for high wind areas, but details are not available.

EWP is working with Siemens to develop their own inverter system, which will improve their turbine's efficiency along with the lightweight rotors. A concern with VAWT on root tops in urban areas will be ice forming on the blades so EWP is also working with M3 to test ice resistant coatings. They are currently testing prototypes on Mt. Washington to test how the coatings perform during the harshest winter in the U.S.

It is very inspiring to see that non-engineers can still achieve a goal revolutionizing the energy field and improve urban environments. It is either EWB or the IMPLUX vertical turbine, guaranteed to not hurt a bird.

There are many reasons why there a few wind options in urban areas. I discussed many of there, after this link.

However, are all the wind farms a good idea? One person thinks they will deplete the world of its kinetic energy.

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(Via MAKANI POWER)

Remember flying a kite as a child? At times, it could almost pull you over. Corwin Hardham, CEO of MAKANI POWER, wants to harness that power for an alternative wind turbine. Hardham's team at MAKANI POWER created the Makani Airborne Wind Turbine, an energy absorbing kite.

The Makani Airborne Wind Turbine would hold the same purpose of a traditional tower turbine, energy generation. The kite is designed to withstand the force of the wind, and follow the same arc of a traditional turbine blade. The airborne turbine has the same rated power, but has twice the consistently of the best wind turbine operating today.

The company stated the airborne turbine will weigh just a tenth, and cost half the price, of a normal tower turbine. A traditional 1-megawatt wind turbine can exceed 100 tons; where Makani’s turbine weight is significantly lighter while still providing the same power output. The turbine gets its advantage from a carbon-fiber wing and a lightweight motor.

The Makani Airborne Wind Turbine’s motorized fixed-wing gliders circle a circumference of 26 feet. When at 1,000 feet and traveling 150 miles per hour, the turbine creates resistances against the high altitude winds which spin the small propeller blades along its chassis. While at flight, it is constantly streaming electricity to the grid connection strapped to the ground.

What about days with little wind? The glider will draw power from the grid to keep it airborne. If enough time of no wind passes, the kite will be reeled in for deployment in more favorable conditions. The small propellers create a loud buzzing sound, which the team is currently focused on eliminating.

In the end, the Makani Turbine's power output costs 3 cents per kilowatt hour, which is on par with today's modern wind farms. However, when factoring in the initial cost of the device and installation, the Makani Turbine comes out on top.

The Makani Airborne Wind Turbine not only won this year’s Breakthrough Award in energy from Popular Mechanics, it also received a $3 million dollar grant from Department of Energy’s ARPA-E program, in addition to, $20 million in venture capital funding from Google. In 2013, Makani Power plans to launch a prototype of the new design and become commercialized by 2015.

Eavesdropper

A few weeks ago I checked out Ben Bova’s Able One from my library in the format of a preloaded digital audio player.  The device is like a portable MP3 player dedicated to playing a single book.

I found the player did not work on a NiMH cell but worked fine on an alkaline. I mention this in an offhand tweet.  The manufacturer, Playway,  responded immediately offering to help in any way possible.  I decided to test the unit on the bench first.

I powered the player on a bench supply and connected it to earphones with the volume set toward the higher end of the range.  It worked reliably down to 1.1V and sometimes as low as 1.01V.  When I started from zero and increased the voltage, the unit came up just above 1.1V, not much hysteresis.  This is lower than a NiMH cell, so why wouldn’t it run on one?

I tried adding some series resistance.  I repeated the test with series resistance and a capacitor across the battery terminals.  The cap was a 470uF electrolytic with 0.62 ohms ESR.

The measured average current was around 50mA.  I expected the current flow to have a high peak to average ratio.  I did not, however, observe much variation in current on the scope at any point from powerup to play.

The unit would not run on the AAA NiMH cell even with the 470uF cap across the terminals.  (Not surprising; BFC alone is rarely a solution to any problem.)  The NiMH AAA I was using is advertised to have a resistance of 120 milliohms, at DC and 1Hz.  I verified this by measuring the cell's voltage with a 10 ohm resistive load.  The load only pulled it down to 1.26V.

The unit would run on a D-size NiMH, corroborating the idea that internal cell resistance plays some role.

One idiosyncrasy in the player I discovered was if I ran the unit at a higher voltage, let the voltage fall to below 1.2V, and then let the voltage rise to 1.4V, the unit would shut off.  I do not know if this is related to the trouble running off a NiMH cell.

Although I was very careful to limit my current and voltage, at some point unit stopped working and appeared to be broken.  So I e-mailed Playaway again.  I sent them all my test results, told them the player broke during bench testing, and audaciously asked if they would give me schematics and a new one to test.  I thought some customer relations person would ignore my message or tell me to leave them alone.  Surprisingly, they forwarded the message on to an engineer.  They couldn’t provide schematics but said the unit does sometimes brownout in the 1.25V range.  Although the player belonged to my library and it broke on my bench, they offered to replace it for me.

I would love to know why the unit works on a bench supply but not a NiMH battery.  What stands out in my mind, though, is how quick Playaway was to respond to my offhand tweet and how they offered me a replacement after I apparently broke one testing it.  People used to say manufacturers of amateur radio equipment had to have good service because if customers were dissatisfied a handful of people might hear them talking about it on the air.  Social media have vastly increaesd this process.

Does anyone have any ideas why a player would work on a bench supply but not on a NiMH?

(Pictures via Etham Erkan Aktakka and the University of Michigan)

Electrical devices connected to the nervous system controls him. It makes him move, do things, and all the energy from every movement is harvested for their controller. Sound like a science fiction plot with humans at the mercy of technologically, and energy deficient, overlords? No, it is real. In reality, we are the ones levering our technical might over lesser creatures.

At the University of Michigan (UM), Ethem Erkan Aktakka with Hanseup Kim and Khalil Najafi found that it is too difficult to make  a micro-air vehicle (MAV) and moved on to the control of nature's own complex mini-machines, insect. Nervous system control of insects is nothing new, see the neural controlled roach, but the team overcame a major challenge in the usage of insects as MAVs by harvesting power from the living organism itself.

The platform they chose was the Green June Beetle, a rather large and slow insect common in the U.S.  summer months. The team attached a cantilever beam actuated piezoelectric element across the beetle's wings. This produced 11.5 µW. The team then attached two separate beams, one of each wing. This produces 7.5 µW per wing. The final device was a spiral piezoelectric element attached to the thorax, generating 22.5 µW.

At higher wing rates, 85-105 Hz, the spiral produced 45 µW. Placing the beam at the optimal position, closer to the wing muscle's base, yielded 115 µW. Although vibration harvesters, solar panels, and heat to energy devices have been used to power insect control circuits, the UM system has a greater reliability and produces power several magnitudes higher in some cases. Aktakka explained, "The developed device concept enables the practical deployment and extended operation of the same harvester on any individual of the same species, in addition to a great reduction in overall device weight compared to resonant harvesters. A significant power output can be obtained regardless of several Hz of shift in the flapping frequency, or the ambient conditions such as light or temperature.”

The search-and-rescue flag was raised in the further developing of this technology. It is human safety at the cost of lifetime servitude by insects. The project is funded DARPA in the Hybrid Insect MEMS program.

Where these three requirements must be met:

1. Demonstrate reliable bio-electromechanical interfaces to insects
2. Demonstrate locomotion control using MEMS platforms (Micro-Electro-Mechanical Systems)
3. Demonstrate technologies to scavenge power from insects.

I can not help but feel bad for these beetles. The compunctious cost of science.

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We have had a pretty hot week in New York City, so when I was sitting on a friend's couch I couldn't help but notice a consistent source of heat radiating from the entertainment center that was about a foot away.  Upon closer inspection, I noticed that his Motorola cable box was putting out a TON of heat – while it was OFF.

After I thought about the amount of waste heat this device was dumping into a non-air conditioned room 24/7, I started to wonder about the parts and how long they will survive if they are always warm enough to make a breeze.  Is it just a few chips that are blazing hot?  If so, those suckers have to be operating outside of suggested conditions.

Since the designer of the Motorola box made me so keenly aware of the poor thermal designs that  plague some consumer products, I thought I'd write about how an engineer can determine when kinda hot is too hot.  Who knows – maybe it'll save some part someday from getting slowly fried!

For this article's example, if you'd like to follow along I'll be using a datasheet for an LM317, a standard 3-terminal linear voltage regulator.

Here's what you'll need to determine thermal design quality:

1. Thermal resistance of the part given the heat sinking design.
   There are two parameters that need to be looked up: (1) the thermal resistance from the datasheet and (2) the conditions under which that number is determined.  With our LM317, we find theta JA, the thermal resistance from the die junction to the ambient temperature, to be 70-245°C/W depending on the package selected.  Through-hole components make the conditions for this spec straight forward since they are expected to stand up off the board, but there is a third consideration for SMT parts: heat sinking to the PCB.  This is where the datasheets can be a little... optimistic.  With roughly ½ of the part's surface area soldered to the board, this can either help or hurt the thermal conductivity.  In the case of the soldering the large thermal pin to a tiny pad, the board will act as an insulator.  However if the PCB designer uses a large hunk of copper for the thermal pad, heat is quickly wicked away from the part giving better performance.  Sometimes this information is hidden away in an app note, but in our case the plots can be found on page 9 of the datasheet.  Thankfully ON semi specs their parts without the use of a huge copper pad, however one must be wary of 'front-page' thermal specs without considering the heatsinking conditions under which they are valid.  For our LM317 example, we will use a figure of 70°C/W.

2. Ambient temperature in the area surrounding the chip.
   This is not the ambient temperature that the human operator will be in, but the temperature of the ambient air around the part itself.  Will the unit be placed in an enclosed cabinet that doesn't allow air flow?  How about the enclosure of the product itself?  Will the inside of the case get much warmer than the air of the room?  The part's ambient temperature acts as the lowest temperature a part can be, so any increase in temperature from the part's power dissipation will add to this minimum.  For our LM317 example, we will assume it will be in an ambient temperature of 40°C.

3. Power dissipated in the part
   This is my favorite point to consider because it is pure circuit analysis and one can actually calculate a quantitative  number.  The key here is to be sure to find the worst-case power consumption of the part in question.  In the simple case of our LM317 linear regulator, let's say it's dropping a 5V rail to create a 3.3V rail and will need to supply 500mA of current at most.  Therefore we can calculate full-on power dissipation as:
   
           P = (Voltage In  - Voltage Out) * (I)   or (5V – 3.3V) * 0.5A = 0.85 Watts
   
   Of course not all parts are that straightforward, and some switchers may require the use of SPICE to determine the dissipated power (LTspice is my favorite for this kind of simulation).  But in the end, a figure in Watts is what you want to have.

4. Max die temperature of the part
   This can also be found in the datasheet, but often times engineers use this figure to insert a margin of safety.  For instance, some parts have a max die temperature of 150°C, but many experienced engineers will tell you that a part that has a die temperature of over 100°C deserves at least a second look. Keeping the part at a lower temperature than is needed not only gives protection against design errors, but it also ensures that the users who will inevitably operate the unit outside suggested operating conditions will not be disappointed.  In our LM317 case, we won't want it to rise above 100°C.  Somewhere out a person is enjoying the extra caution I took as she sits in a sauna with my design running like a champ.  I just know it.

Now that we have all that, follow this equation:

             Die Temp Max >= (Ambient Temperature) + (Theta JA) * (Power Disipation)

So in our 317 example, we find:

            (40°c) + (70°C/W) * (0.85W) = 99.5°C

Since the assumed worst-case conditions will result in a temperature rise of 99.5°C inside the part, we can safely say the design constraints have been met with 50°C remaining for safety margin.   Success!

I know it can be troublesome to complete a calculation like this for every part that could be hot, but by the time proto boards come back from manufacturing, you'll be happy that you haven't created a glorified hot plate that needs redesign!