Tuesday, November 26, 2013

Battery Applications and Parameters

The following are notes on Batteries for their common applications and parameters
  • Battery Applications
    • Portable Applications
      • Portable electronics, laptops, iphones, toys, medical devices
      • battery used to start engine in cars is the largest market
        • lead acid and lithium ion
      • High energy batteries, highest energy for given size
    • Stationary Applications
      • Pairing with with intermittent sources of electricity
      • high energy is less important
  • Common Forms Factors of Batteries
    • Button Cells in Watches
    • Cylinder Cells
    • Lithium Ion
    • Prismatic Cells
  • Sizes of Batteries
    • 4.5-volt (3R12) battery 
    • D Cell
    • C cell
    • AA cell
    • AAA cell
    • AAAA cell
    • A23 battery
    • 9-volt PP3 
    • button cells
  • Types of Batteries
    • Chargeable or non-chargeable
    • Battery Chemistry
      • Alkaline 
      • Lead acid 
      • NiCd nickel cadmium
      • NiMH nickel metal hydride
      • Lithium ion
  • Important Parameters of Batteries
    • Energy (Watt Hour)
      • Energy Density - Energy Per Unit Volume
      • Specific Energy - Energy Per unit Weight
      • Characterize the total amount of energy it carries, lifetime of battery once you charge it up, distance of electric car
    • Power (Watt)
      • How fast you can take the energy out of a battery
      • Power Density Power per unit volume
        • Example more important for Laptop, fitting into size constraint for a high usage device
      • Specific Power Power per unit weight
        • Car, heaviness of battery impacts performance
      • Life
        • Cycle Life, times we can charge and discharge a battery with its capacity still above 80% of the original
        • Calendar Life Time a battery can last if left on shelf
          • Electrical car ensure it can last for about 10 years?
      • Safety
        • Battery intrinsically is in unstable state
      • Temperature Performance
      • Cost
        • Currently its difficult to justify batteries for cars and grid use

Electrical Engineering ToC

Table of Contents

  1. Batteries
    1. Battery Applications and Parameters
    2. Battery History
  2. Digital Design
    1. Finfet

Thursday, November 21, 2013

Notes - Sustainabiltiy and Energy Storage Stystems

The following are notes on the sustainable energy sector and the potential of energy storage technologies.
  • Sustainability
    • Energy storage is useful in order to balance the grid
      • grid balancing is making sure that the amount of energy being produced by the grid is equal to the amount of energy being used by it
    • Issues it solves
      • As the amount of renewable sources continue to increase, the fluctuating nature of the energy production means that we will need to capture any "excess production" in the case that renewable sources produce too much energy
      • This becomes profitable if storage beats the costs of turning on and off other generators such as coal, gas, etc.
    • Issues facing growth of industry
      • We would require variable renewable sources to generate greater than about 20% of our electricity in order for this to become viable
        • variable includes wind/solar, production dependent on variable sources
        • non variable renewable includes hydropower, biomass, geothermal because their sources are controllable

      • As is clearly shown in the above solar amounts to .12% of our total energy production, and wind amounts to 3.36% for a total of about 3.48%
        • Solar although it is a rapidly growing field is still dependent on subsidies, although this may soon change, something needs to change in the market in order for there to be an increase in buyers
        • Wind is completely dependent on government subsidies. There is near 0 production when subsidies are taken away, so wind development relies on smart governmental decisions
          • Cue Government shutdown
        • Additional Complications
          • there is steep competition given by China which has better economies of scale as they are investing heavily into the older silicon based solar which is cheaper to purchase
            • Note China as a whole is not yet profiting, but they are gaining a powerful grip on the market
          • US is "going big" in solar arena by increasing efficiency of their cells
            • this would need to be coupled with trends i.e. requires help from mainstream media in order to become successful
              • Exceptions - First Solar, although product has increase in efficiency, a byproduct was that the it "looks better" as electrodes are attached beneath rather than on top of the modules in order to increase efficiency
              • This is similar to Apple which used a sleek design in order to sell the product, meeting the social needs of the user
            • Similar story to Solyndra this means US companies require large initial investments, reduces amount of entrepreneurs capable of accessing the market
  • Energy Storage
    • There are two divergent paths a company can take
      • Invest into countries outside of the US
        • By taking control of third world countries there is a potential to have access to the infrastructure of an entire market over time
        • Can sell to a more mature market
      • Invest into a longer time span
        • assumes that the US will not tolerate other countries exceeding our infrastructure base
          • Has some merit i.e. average internet speed competition of Asian countries now being counteracted with Google fiber and other extreme high speed connections
          • Fiber slowly replacing copper

Sunday, November 3, 2013

Physics - Classical Theory of Conduction

The following is a brief overview of the classical theory of conduction.

Fluid Analogy
First I would like to invoke the fluid analogy to electricity. Basically there are many similarities between different phenomena for fluid mechanics and electronics. The reason why we have this analogy is simply that most people are used to dealing with fluids, especially those of us with access to plumbing and running water. However, most of us don't even think about electricity, we just put a plug in an outlet and stuff works.

Now how does a battery work? Its no mystery though Bill O'Reilly might disagree. We can see on a battery's label a + and a - sign. We can think of this as a lake at the top of a mountain and a lake on the bottom of the mountain. They have different potential energy due to gravity. When we plug in a battery its like digging a trench to connect the two lakes and putting a water mill in between it to drive our machine.

Relation to Conduction
We can then relate two other phenomena. Current in a wire is very similar to trying to get water to move through a pipe. The smaller our pipe, the less current can get through, which is similar to a wire with high resistivity. In electronics we can think of a wire as a lattice of of atoms. Our electrical current is then though of as electrons traveling through this lattice. An electrical field caused by our difference in potential drives electrons through this lattice but the lattice is stationary and stops/causes ricochets when an electron hits it. We can describe this with the following two equations:

I =ΔQ/Δt = neAvd and
λ = <v> τ =1/naπr2 as

Where for the first equation I is the current described by n the number of electrons, with charge e, passing through an area A with electron drift velocity vd. The second equation gives us λ is the mean free path, or the average distance a particle travels before a collision with <v> the average velocity multiplied against τ the average time between collisions. Through this we can figure out resistivity and conductivity and can derive Ohm's law. 

V = IR

This is a great approximation but there are significant errors when scaled to different temperatures and other quantum effects.

Paper - Skill Acquisition

Skill Acquisition as a Function of Effort

This is a discussion of my viewpoints on skill acquisition in relation to effort/time investment. First I'd like to divide skill into two main components, mechanics and execution mainly in relation to a sport or game, though this can applies to pretty much any skill when substituting in different terminology. Mechanics for a sport is the player's trained skills. For an athlete it would be the capability to move his/her body in a given precise way. An example for tennis would be for a player's forehand, the strength of the hit, its precision, timing of the shot after the bounce, etc. Execution is the player's capability to perform those mechanics under pressure, in competitive situations, or when something is "on the line".

Mechanics for a person will usually rise when effort is put in. So classically we can think of skill as a function of effort as something like this.

However, this as with everything has major pitfalls. It is very possible for this to go negative like so after some initial improvement. 

How does this happen?
Unfortunately it has everything to do with luck and our environment. When acquiring a skill everyone usually learns from somewhere. It usually builds upon something that is taught to us directly, or builds on past experiences that we are able to connect with the skill we want to improve. With the internet we can also be "self-taught" and do our own research but that information was still written by someone else in the first place. In some rare occasions people are pioneers and must figure out things the first time through, but we won't go into that too much here.

The issue with this is that our information source can be wrong. Whether it be a coach or a teacher, or some random article on the internet we might just be going about something the wrong way and be ingraining into ourselves incorrect muscle memory. We could also be guided by correct information but interpret it the wrong way which will have the same effect, worsening our skill.

The only thing we can really get out of this situation is experience. Usually by doing something for a long period of time, we can then make a realization on how to correct our errors, or observe or be observed by others and make the correction by fixing that information returning us to our original rate of improvement. However, there is a possibility of getting worse. This is a very important concept to understand, there is no fairness in the world, spending effort does not necessarily mean you will improve, but it does give you the chance to improve/change where you are.

Also not spending effort will always result in a decrease in skill over the course of a long period of time. Again things are not fair here, breaks can sometimes result in a breakthrough as you gain a new perspective. This phenomena is often talked about by academics, but it also applies to sports and other motor based skills as your muscles have an opportunity to loosen up on their habits/memory which can lead to greater control with additional information/accidental improvements. This means that a person's skill level is often riddled by positive and negative interjections like this, where mechanics raise and fall temporarily. Sometimes a person is able to grasp their sudden improvement and retain parts of it/all of it and increase their skill over a very rapid period of time, but it can also sink and again result in a decrease in mechanics if analyzed incorrectly.

Execution is essentially a person's mental game. Very few people have managed to obtain a stable mental game and it is affected by a wide range of events. A person's relationships, their confidence, their job, anything that causes mental stress or happiness outside of the pursuit of that skill can affect their ability to perform that skill. A graph that represents this would be something like the following.

This is the roller coaster ride of ups and downs that everyone experiences which is linked to our maturity. Speaking of which as we mature, we are able to clamp down on these variations, and improve based which can be represented with the following.

Basically as we mature we become more predictable and are able to reduce the impact of our emotions into our skills, thereby making our performance more reliant on our mechanics rather than state of our emotions. However this is one of the most difficult things to do, and honestly achieving this does not necessarily mean you will be the most successful, but I will discuss that at another time as it relates more to successful personalities, and less to the process of acquiring a skill.

Friday, November 1, 2013

Physics - Quantum Tunneling

The following is a brief overview of Quantum tunneling.

What is it?
Quantum Tunneling is the effect where a particle tunnels through a barrier it could not penetrate in classical physics.

Why does it happen?
Quantum physics tells us that matter exhibits both particle and wave-like behavior. Therefore if we apply this idea to an electron going up against an potential barrier, we can relate its behavior similarly to a more well known event, light traveling through a material such as glass. In this case, the brightness of the light passing through the surface is reduced and some is reflected back away from the observer behind the glass. With our electron, some of its probability function travels through the potential well, and some of it reflected, depending on the width of the energy barrier, which we can relate the opacity of an object.

Brief Overview of Formulation
The time independent Schrodinger equation is as follows

(-ħ2/2m)(d2Ψ(x)/dx2) + U(x)Ψ(x) = EΨ(x)

The full derivation will be done elsewhere but we can use these to get the solutions for traveling waves, which represents the probability function of a particle in motion. This represents our electron moving. Using the WKB approximation and a few other mathematical tricks such as series expansion, we arrive at the following equation for T the transmission coefficient or percentage chance at quantum tunneling.

The important part of this equations are, x1 and x2 which are the classical turning points for the energy barrier. We can therefore see that this equation depends primarily on two characteristics, the difference in energy between the particle/wave represented as E. V(x) which is the potential of the energy barrier given x, and the width of the barrier x where a higher energy difference results in a lower transmission coefficient, and a greater "width" again results in a lower transmission coefficient.

Relation to Electrical Engineering
This is a material science concept and when used in reference to tunneling in electrical components, we don't have to go into the full Feynman path integral method to just get an idea of how it works. We can get a good idea of the effects with the explanation above. Tunneling occurs with barriers the size of around 1-3 nanometers which will be extremely significant when dealing with finfets which promise to move the total size of the transistor to around the 10 nm range. Efforts must be made to maintain detection of the on and off state due to thermal noise and summation of inductance effects of nearby inductance effects. This means design rules must be made with greater spacing margins than might be otherwise done for normal mosfet design.