Week 5 Challenge

1. Consider a scenario where an aggressive driver is accelerating very rapidly and braking harshly in a city driving. Is battery better a choice to supply power than UC in this scenario?

1. True
2. False

Why?

Answer:

False. In this scenario, battery is not a better choice in the given driving scenario.The drivers driving pattern can be concluded here as short power transients. So here Driver is accelerating and we all know how the power demand shoots up at the time of acceleration though for a short time.

In the above graph, Pa represents the acceleration power. This power is only needed when we are accelerating. So It is still dominant amongst all even though we need this power for short time only. Here the Battery can supply this demand but the cost of manufacturing such batteries is extremely high. On the other hand ultracapacitor holds very high power which it releases on demand and it can get charge quickly too. This quality of having high power density makes the ultracapacitor a perfect choice of power source for such transient power demands.

2. Consider the following components.

1) Lead acid battery 2) Nickel cadmium battery 3) Nickel Metal hydride battery 4) Lithium ion (specify chemistry) battery 5) Ultra Capacitor

Note: In case of a range of energy density, take the average value for the plot.

Create a plot with energy density on the X Axis and cell voltage on the Y axis.

Comment on the capabilities of these batteries based on the plot created.

Answer:

Energy density is the measure of how much energy a battery contains in proportion to its weight. This measurement is typically presented in watt-hours/kilogram. The higher the energy density, the longer the runtime. The values of energy densities of different batteries and cell voltage are shown in the below table and also the same is represented in the X-Y plot shown below.

Battery Name	Energy density	Cell voltage
Lead-acid battery	35-40	2.1
Nickel Cadmium	40-60	1.2
Nickel Metal Hydride	60-120	1.2
Lithium-ion	100-265	3.6/3.7/3.8/3.85
Ultracapacitor	89.6	3.5

Lead-acid batteries have relatively low energy density. Nickel Cadmium has a much higher energy density compared to lead-acid batteries. Ni-MH batteries can have two to three times the capacity of NiCd batteries of the same size, with high significance and also much less than lithium-ion batteries. Lithium-ion batteries have a high energy density. Energy density is more in ultracapacitors compared to capacitors.

3. For the above-mentioned components on the same plot (retain the previous plot) created in the previous

Create a plot with power density on the X axis and cell voltage on the Y axis.

Answer:

Power density is the the battery's capacity to absorb and deliver electricity is referred to as power density. i.e., a battery with a high-power density will charge more quickly than one with a low power density.

The power density of the above set of batteries is as shown below.

Battery name	Power density (W/Kg)	Cell voltage (V)
Lead-acid battery	180	2.1
Nickel Cadmium	150	1.2
Nickel Metal Hydride	1000	1.2
Lithium-ion	340	3.6
Ultracapacitor	496	3.5

The power density plot of the batteries is shown below in the plot.

4. Consider the following scenario:

A battery has just been manufactured in the industry and has been connected to a charger for the first time. The electrode marked as (1) in the picture below is the negative electrode.

1. True
2. False

Answer:

It is true that the number indicated as 1 is a -ve electrode. Lithium-ion batteries generate DC power by utilizing chemical reactions. During discharge, lithium ions from the -ve anode move through the electrolyte to gets intercalate the +ve cathode. During charging, electrons move from anode to cathode in the external circuit.

During the electrochemical process, the anode is -ve and the cathode is +ve. At the first time charging, the lithium-ion from the cathode gets attached to anode and it forms the inseparable layer on the anode. A solid Electrolyte Interface (SEI) is formed at the anode. Anode gets decomposed if it comes in contact with the electrolyte. SEI protects the anode.