We connected the outputs from the solar panels directly to the PC, so it has 16 V DC of power at its disposal. Depending on the intensity of sunlight at any given moment, though, these modules output anywhere between 12 and 20 V DC. That's why we chose a very special power supply - namely, the M2-ATX from Ituner - that can handle input voltages in a range from 6 to 28 V DC.

The Ituner M2-ATX power supply

Top view of low-voltage power supply

Because this is a low-voltage power supply, the maximum rated power for this device is a scant 160 W. The input voltage to the PSU is also very close to the output voltage it needs to produce for a PC. This narrow difference between input and output voltages has the happy consequence of enabling extremely high efficiency, compared to a PSU that handles conventional A/C power. We use this power supply to drive all the components in our solar-powered PC, including the monitor.

The Ituner M2-ATX includes only a single 5.25" drive connection and a single SATA connector, so we used a Y-adapter to hook up the rest of our components.

We used a Y-Adapter to route power to additional devices in our PC

We measured the efficiency of the power supply in our solar-powered PC at idle, and under heavy load, as shown in the following chart.

Efficiency for our low-voltage PSU