May 22, 2013

Tesla Announces Battery Swaps (kind of)

In case you missed it, Elon Musk, founder of Tesla Motors (the electric car company) recently tweeted that "There is a way for the Tesla Model S to be recharged throughout the country faster than you could fill a gas tank." There's only one way I know of to recharge an electric car faster than filling a gas tank and that is swapping a discharged battery for a fully charged battery. That is, instead of plugging the empty battery into a charger and waiting hours for it to recharge. you simply replace the empty battery with a full battery.
Then, in Tesla's most recent quarterly filing with the SEC they mention:
"Other factors that may influence the adoption of alternative fuel vehicles, and specifically electric vehicles, include...our capability to rapidly swap out the Model S battery pack and the development of specialized public facilities to perform such swapping, which do not currently exist but which we plan to introduce in the near future." (emphasis mine)
Although Tesla has not made an announcement to the press, this is a pretty forward-looking statement to put in your SEC filing. "Near future" could mean anything, but Tesla has put a stake in the ground that they will be developing battery pack swap stations.
Now, anyone who has been following the electric car industry for some time might ask: What about Better Place? Haven't they been doing battery swaps for some time? What's the big deal? (As a refresher, here's a link to Better Place's swappable battery packs for electric vehicles patent.)
The big deal is, Tesla is now the largest manufacturer of electric vehicles in the world, and has shipped more electric cars than any of the large car manufacturers. The biggest obstacle Better Place has faced is the old chicken-and-egg problem: Few car manufacturers were willing to produce cars that used Better Place battery packs until there were numerous Better Place swap stations, and nobody wanted to build swap stations until there were cars that used the battery packs. Although many manufacturers (and governments and fleet operators and so forth) have expressed interest in Better Place-like technology, adoption and deployment has been very disappointing.
Tesla completely sidesteps that issue because they are a car manufacturer. There is a clear benefit to them to deploy battery swap stations: They effectively give their cars infinite range, making them much more desirable. By being first movers, they can also dictate standards for swappable battery packs. (If you're going to build a new electric car after this, it had better be compatible with Tesla's swappable packs.) The sooner Tesla deploys these battery swap stations, the sooner they will establish a leadership position.
Posted by todd at 11:02 AM

May 20, 2013

Using OpenVSP and AutoDesk Project Falcon to model and test drone designs

I came across two tools recently that are handy for designing and testing drone models. The first is OpenVSP (VSP stands for "vehicle sketch pad") available as a free download from NASA. OpenVSP allows you to create models of airplane designs using a toolbox of common airplane objects such as wings, tube fuselage, pods, rotors/propellers and so forth.


It also contains more complex objects such as blended wing-body hybrids. The really cool thing is that all of these objects are parameterized with critical parameters such as the chord for a wing, the NACA airfoil number for a wing, the number of blades on a propeller, and so on. This allows you to quickly fuse together the plane design you desire and tune it with commonly-used aircraft design specifications.
Once you've created a design iteration you'd like to test, you can export an STL file (a common 3D CAD file format) of the design. Then, you can import that into AutoDesk's Project Falcon tool, another free download.

Project Falcon allows you to test your drone design in a virtual wind tunnel. It's a computational fluid dynamics (CFD) app that tests your drone design by simulating the flow of air over the drone's surface.




Falcon also calculates drag and lift forces and shows them in a handy graph. This allows you to fine-tune your design and get an idea how much payload your drone can carry.


The ability to view pressure points on the drone's surface can help you pinpoint problem areas that are causing your drone unwanted drag or loss of lift.

Fun Stuff

For those who are seeking an easy way to quickly iterate their drone designs, these two tools are great for tweaking your design using well-understood airplane and copter components. The virtual wind tunnel CFD capability in Project Falcon can give you an estimate of the flows that will affect your drone before you start building.

The Guts

I've forked the source of OpenVSP and made a handy Mac OSX app bundle available on github.

Posted by todd at 11:36 AM

May 15, 2013

Shelving Energy Storage Project

This week I decided to shelve the energy storage project we've been working on. (I might come back to it at some point in the future, but for now it's on hold.) Ideally, I should have been blogging about progress all along, but most of the work we were doing was confidential, with the potential for patent applications at the end of this year.
Here is a brief summary of the progress we made. It's not meant to be a complete detailed description (that may follow when there's time/energy), but just an overview of the project.

In May 2012 I undertook a project to find a way to meet or exceed the energy density of gasoline with a rechargeable electric storage device. (Briefly, energy density is the measure of how many energy can be stored in an object with a certain weight, such a car battery or a tank of gas.)
Starting from a clean slate, I was open to using any technology that would achieve that goal. I researched a wide array of technologies and partnered with experts in the field to build prototypes and experiment in the lab.

Over the course of about a year we were able to complete four major iterations:

1. Ultra Capacitor

The idea here was to use novel geometries and materials to achieve much higher capacitance than had previously been reported. However, after many months of modeling, simulation, and research, it became clear that the theoretical limit of ultracapacitor energy density was actually not much higher than the current levels achieved in the lab, and nowhere near as dense as batteries. The net result was covered in a previous blog post: a paper detailing the practical limits of energy density in ultracapacitors.
FatCap-TestRig01.jpg FatCap-nacre05_01.jpg

2. High Temperature Solid Oxide Fuel Cell (Lithium-Air)

This was a novel approach to lithium-air electrochemistry that used a LiCl+KCl eutectic mixture as the anolyte, and lithium metal as the fuel. We submitted preliminary patent application (PPA) for this idea to the US patent office. Since we're no longer pursuing this idea, I've decided to make the PPAs publicly available:

High-Temp01.jpg High-Temp02.jpg

3. High Temperature Cell with Cuprous Oxide cathode

The idea here was to continue using the high temperature LiCl+KCl eutectic mixture as the electrolyte, but eliminate the fragile and expensive SOFC catholyte disks. We were also able to drop the projected operating temperature range from 850C to 450C. A layer of high surface area copper was placed in contact with the electrolyte and continuously oxidized by exposure to air.

Low Temperature Cell with Deep Eutectic Solvent

The idea here was to replace the corrosive high-temperature LiCl+KCl eutectic with a new electrolyte based on deep eutectic solvents (DES).
Low-Temp-Cu2O-01.jpg Low-Temp-Cu2O-02.jpg Low-Temp-Cu2O-03.jpg

The executive summary is that none of these techniques achieved the energy density we were hoping to attain. In future blog posts I may add more details here. Feel free to direct questions to me.

Posted by todd at 09:51 AM