Basic Load Resistance: Maximize Power Output

[cj]

Basic Load Resistance??

I'm a high school science teacher. I have a lab activity that explains how to measure the current v. voltage characteristics for a solar cell. Finding the load resistance that provides the maximum amount of power generated is also covered.

Question: What are the practical ramifications of this? I'm thinking that the idea is to either a) match the resistance of the load attached to the solar cell as a way to maximize power, and/or b) match the solar cell's electrical characteristics to the load resistance as a way to maximize power. What more can be said about resistance? I checked wikipedia, but found it pretty cryptic.

Am I right? What other correlations can I make? I have the feeling I can be making a lot more out of this activity, and would appreciate any feedback.

- Chris

 

[berkeman]

I'm a high school science teacher. I have a lab activity that explains how to measure the current v. voltage characteristics for a solar cell. Finding the load resistance that provides the maximum amount of power generated is also covered.

Question: What are the practical ramifications of this? I'm thinking that the idea is to either a) match the resistance of the load attached to the solar cell as a way to maximize power, and/or b) match the solar cell's electrical characteristics to the load resistance as a way to maximize power. What more can be said about resistance? I checked wikipedia, but found it pretty cryptic.

Am I right? What other correlations can I make? I have the feeling I can be making a lot more out of this activity, and would appreciate any feedback.

- Chris

The maximum power point for a solar cell is where you get the most energy out of it. You have the DC-DC converter circuit (or DC-AC inverter circuit) modulate its input conditions to interface to the solar cell output at the MPP.

I Googled solar cell maximum power point, and got some good hits. There appear to be some teacher resources in the hit list as well (but I didn't open them):

http://www.google.com/search?source...enUS301US302&q=solar+cell+maximum+power+point

.

 

[skeptic2]

Question: What are the practical ramifications of this? I'm thinking that the idea is to either a) match the resistance of the load attached to the solar cell as a way to maximize power, and/or b) match the solar cell's electrical characteristics to the load resistance as a way to maximize power. What more can be said about resistance? I checked wikipedia, but found it pretty cryptic.

- Chris

This is an excellent question. The first practical ramification of this that comes to mind is the need for a dynamic matching network to match the output impedance of the solar cells to the charging impedance of the rechargeable batteries. When a cloud passes in front of the sun, the matching network would adjust its input impedance to the now higher impedance of the solar cells. Likewise when the batteries are somewhat discharged, the network would present a lower impedance to the batteries.

Such a network could be a variation of a DC-DC converter in which the step up or step down ratio could be dynamically changed.

Edit: Sorry Berkeman, I didn't read your response before I responded. I see how similar mine is to yours now.

 

[cj]

Berkeman and skeptic2 - thank you very much! These are two fantastic responses that are really enlightening. I'm pouring over maximum power point materials and am learning a lot. Thank you both again.