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Getting Power Readings from the MSP430 Solar Energy Harvesting Development Tool

Thaddaeus Voss
Prodigy 20 points

Hello,

I have been reading about the MSP430 Solar Energy Harvesting Development Tool.  I am very interested in this Development Tool, however, I have one quick question.

I would like to read the output power of the solar cell.  As I understand it, this development tool can transmit the voltage reading (probably an open circuit voltage) from the solar cell at different time intervals. However, this is not a power reading.  Does anyone know of a way that I can derive a power reading from the voltage reading over time? Or if there is a way to derive a power reading at any time based on circuit elements?

Here is the datasheet for this development tool if you would like to look at the circuitry (page 12) as well as a sample output with voltage readings (page 16)  :

http://www.ti.com/lit/ug/slau273d/slau273d.pdf

  • 0
    Guru 227245 points

    Thaddaeus Voss said:
     Does anyone know of a way that I can derive a power reading from the voltage reading over time?

    power is voltage * current. Over time, it is energy (integral over time interval for U*I). If you have two solar cells and know their U/I curve, you could read the U from both, one open loop (and maybe significantly smaller), one used with a load, and calculate by the open loop voltage of one cell and the loaded voltage of the other the current drawn from the other and therefore the momentary power provided by the loaded cell (if both cells are equally exposed to sunlight).
    Or you'll need a current sensor of some sort (which unfortunately will cause a voltage drop and power loss)

    If you can enable and disable the load on the cell, you might be able to measure both voltages, open loop and loaded, form the same cell. But this will limit the time the cell provides power and therefore reduce performance too.
    You can't eat the cake and keep it.

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