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Tuesday, June 11, 2013

Ultracapacitors in Tesla's Future?


In a recent earnings announcement for Tesla Motors, Elon Musk said that Tesla would demonstrate something that will make their superchargers look slow. “I mentioned that there would be an announcement on June 20... not an announcement... a demonstration,” said Musk.

Tesla's superchargers are the fastest, highest-power charging technology on the market today. They are the state of the art. So what could be faster? What could make rapid 20-minute supercharging look positively slow?

Most of the twitter-sphere, blogosphere, and autopress seem to agree that Tesla will demonstrate a battery swap station. There are statements like "Tesla will have swap stations like Better Place, but they will have a better business model or make them free."

Elon Musk has publicly talked about battery swapping several times. He has said that Tesla may offer an option to rent a high mileage pack for a roadtrips. Something like this would require the ability to swap battery packs but overall his comments about battery swapping have not been glowing. Battery swapping is not a "first principles" solution. Battery swap stations make an assumption that the current energy storage technology will not advance rapidly. Swap stations workaround batteries recharge time limitation. Tesla is not a half-measures workaround type of company. They prefer the pure play. The company is betting on the advancement of energy storage systems.

Despite the consensus on of cyberspace, I predict that they will not be showing a swap station on the 20th. It is not an Elon move. I have a different guess as to what Tesla will be showing. I think they will be showing a car that has ultracaps.
Why do I think it will be an ultracaps demo?

There are hybrid buses on the streets today that use large format ultracaps to store energy from regenerative braking. There are also wind turbines that use ultracaps to smooth out the variable power that intermittent wind can cause. Portland, Oregon's Tri-met recently announced that their light rail trains will be the first in the country to use ultracaps to improve power delivery from the overhead lines.

Given that there are many applications using ultracaps on the market today, including transportation uses, I think Tesla has made a prototype EV that has ultracaps rather than (or in addition to) batteries for the energy storage system (ESS).

Elon said that the demonstration will make the current Supercharger systems (still being rolled out) look slow. The bottleneck of the current system is not the ability to deliver energy. Delivering more energy may have some logistical problems, but it is not technically difficult. Rather, the limiting factor of recharge time is the ability of the batteries to absorb the energy. Ultracaps have no such limitation. Since ultracaps stores energy in an electric field, rather than in a chemical reaction, they can store the energy as fast as it can be delivered.
Ultracaps are Virtually Lightning in a Jar
Given the strategy for both the Tesla Roadster and the Tesla Model S has been to take commercial 18650 form-factor laptop batteries and pack them together for vehicle solutions, ultracaps would be the logical evolution beyond batteries.

Ultracaps have several advantages over batteries including charge-time and cycle life. They can survive hundreds of thousands more charge and discharge cycles than a battery can. There have been great strides in graphene supercapacitors recently. Including methods to make them significantly cheaper.

Batteries still have several times the energy capacity of ultracaps. So, if my speculation is correct and the demo is an ultracap car and an ultra-charged supercharger, then vehicle will likely have either a shorter range than the current production models, or it will be a hybrid energy storage system with both batteries, for range, and ultracaps, for fast charging and improved regen braking energy capture.

The Tesla Roadster has 6,831 batteries and the Model S has over 7000 of the 18650 laptop batteries. So, if there is any company out there that knows how to package a large number of little rechargeable devices together in a crash and fire-safe manner, it is Tesla.

We'll find out on June 20th!