Solar Freaks

Ok..

So, not content with my original nanometer project.. I've redesigned it.
Now, it has an on board IV sweeper to measure the output characteristics of the solar panel, and draw the solar panels I-V and power curves. It also can be used as a solar power meter (or a normal DC power meter) and read and log the output of the solar panels (Voltage, Current, mA/h) up to 20amps at 50 volts. Also can be used as a multimeter.

Has USB connectivity to send all information, data, logs, graphs to a PC.
Its due soon, I'm hoping to have the boards complete within the next few weeks. I'm currently finalizing the PC software.

This unit is very energy efficient, and goes to sleep when buttons aren't pressed for a minute, and only drains 1mA, while it continues to log output data of a solar setup. The original nanometer drew nearly 30mA continuously, and only handled 5 amps of current maximum.

This unit is FULL SMD.

If your wondering what those three big capacitors are for!? Well they are to load the panel so it can sweep the I/V curve.

Do you have a simulation tool that would allow using the per panel VI data to insert into large system model. If the actual data could be used to determine how various impairments on top of the VI data in a large series string and parallel combined would effect the total power would be handy. It would help show how an MPP optimizer or per panel DC-AC inverter would really perform if all the parameters could be added. Ever see a software tool or MatLab simulation like this?

pgrovetom wrote:Ever see a software tool or MatLab simulation like this?

Never seen one before. Its quite interesting actually, having a tool like that would help predict system performance when we have unmatched solar panels. Normally, when we design systems, we use matched panels, however over a long periods of time, solar panel characteristics do drift, and thus affect the entire system performance.

Ill start searching for this, if i cant find one, i might work on my own model. Very interesting indeed.

Some pictures of the working unit.
I tested a 6 watt panel on my light box, the data can be seen below.

Shown on display:
Open circuit voltage;
Max Power voltage;
Short circuit current;
Max Power current;
Actual Power;
Theoretical Power; http://www.solarfreaks.com/what-is-the-fill-factor-of-a-solar-panel-t138.html
Number of ADC samples.



Unit also stores the I/V curve data in a array and dumps it through the USB, so the curve can be displayed and analyzed in excel.
Ill show more pics soon.

The operation of the NanoMETER is very simple, and is based on a basic electronics principle; 'With finite current, the voltage across a capacitor can never change instantaneously'. When we connect a solar panel to the onboard capacitor bank, the voltage will begin to rise from 0 volts, all the way up to Voc, and our charge current will also vary, depending on our panels I/V curve. There is a MOSFET, near the capacitor bank at the back, which is used to discharge the capacitors by simply shorting them, and the energy is dissipated within the local parasitic resistances.

As the capacitor bank charges up, the CPUs onboard analogue to digital converter will take readings of both the voltages and the currents. The readings are stored in an array of Power objects, and later multiplied and compared, to find the peak power. The open circuit voltage and short circuit currents are also extracted, and a value of our panel’s theoretical maximum power is also given. Integration is used to calculate the Fill Factor.

Digital Infinite Impulse Response Filtering is used on both the voltage and current readings to sooth the effects of noise.



This is one of the reasons the Nanometer produces results that are so consistent.

Hey Tony,
any updates on this IV curve tracer? Could I buy a board from you?

thanks,
imran