Submitted by Sabre
The Future of transportation: It’s a relay race…not a marathon
In 2007, Shai Agassi starting a company called Better Place. The concept behind it was changing out batteries that power a car, instead of filling your car with gasoline. Shai Agassi looked at the problem correctly. He saw transportation fuel as a never ending relay race. But what if there was a technology that could do the same thing, without changing out the battery?
Let’s start with the problem. Gasoline is a finite resource but it provides a vehicle an uninterruptible power supply (UPS) limited only by the size of the vehicle’s tank. The focus of scientists and engineers today is to develop a battery that can compete with gasoline as the vehicle’s fuel source. As I hope to show, that is proving to be a near impossible task.
Examine the Chevy Volt. The battery pack in the Chevy Volt weighs about 400 pounds. Running the Volt on the battery pack alone gives you between 25 to 50 miles of range after every six to eight hours of charging time. Once the battery pack is depleted, the gasoline engine kicks in (yes, the Volt has a gasoline engine).
What about hybrids like the Prius? This is where I will focus on the shortcomings of lithium ion.
The battery packs in the likes of a Prius are designed for longevity. Hybrid batteries use in the neighborhood of 15%-20% of their available power, as the batteries simply cannot handle deep discharges without dramatically reducing the life of the battery. So, a system of electronics is set-up in a hybrid to manage the amount of charge in the pack at all times.
This is where battery chemistry kicks in and it is not good. If only 15-20% of the battery power is available, batteries would still be acceptable if they could re-charge quickly. They cannot. Batteries have a fixed rate charge capability. If that limit is pushed, then the life of the battery decreases. Furthermore, batteries trickle charge the last 20% or so of their capacity, making them even more problematic, as that is the part that vehicles use for power to maintain longevity of the battery pack.
As a result, hybrids and vehicles like the Volt, lend themselves to stop and go traffic and short hauls. The battery pack does not lend itself to anything but that type of driving.
To counter these shortcomings, oceans of money are being spent on research projects throughout the world to develop a longer lasting battery. The scientific community is looking at the electrification of transportation as a duration/density issue or more simplistically a marathon. In Energy Secretary Chu’s words, here is what we need.
It will take a battery, first that can last for 15 years of deep discharges. You need about five as a minimum, but really six- or seven-times higher storage capacity and you need to bring the price down by about a factor of three. And then all of a sudden you have a comparably performing car; let's say a mid-sized car which has a comparable acceleration and a comparable range.
Is this possible? http://www.youtube.com/watch?v=h8xlezXxcDk Consider the first minute of this clip. It took twenty years to double the density of lithium ion batteries. Argonne’s partnership hopes to double density levels in the next three. Again, this is all about running a marathon when it comes to using batteries.
But there is a different way of looking at the electrification issue. Is there a technology that would lend itself to that of a relay race, instead of a marathon? The answer is undeniably yes. It is the capacitor.
A capacitor is a form of passive energy storage. It does nothing but hold a charge and release a charge. But the qualities of a capacitor lend itself perfectly for transportation in all areas but one (density) and that may be changing. Consider the following characteristics of some ceramic capacitors.
• Almost instant charge and discharge rates
• Long Life (will most likely outlast the car)
• Not sensitive to deep discharges
• No cell balancing (Batteries in series have voltage issues that require electronic monitoring)
• No thermal runaway(Batteries are at risk of over-heating)
Visually, it would look like the following. The vehicle would have capacitor banks (ESS). While one bank is charging, the other bank is discharging its power. Hence, you have a never ending relay race between the capacitor banks.
The source of the power for charging the banks could come from a few sources.
Wheel production of electrical power.
Each wheel contains an electric motor which converts friction into electrical energy. This is done by using the resistance when applying braking force and the movement of the car.
The electric motor applies resistance to the drivetrain causing the wheels to slow down. The energy from the wheels turns the generator which slows the vehicle down, which then produces electricity and stores it in the ESS.
There are a few individuals/organizations that are looking at this age old technology, Joel Schindall at MIT and this outfit in Germany http://www.super-kon.uni-halle.de/project_super_kon.pdf to name two of them. But the overriding issue with capacitors is energy density. While no one doubts the capability of capacitors to hold a charge, no one has solved the density issue. In my next update, I’ll present the case of an American company that may have a working model with enough density…sorry Eestor fans I am still waiting.