DIY Solar-Powered PC: Solar Components

Polycrystalline Solar Cells Produce 260 Watts

Of course, the most important component in any solar array is the solar modules themselves. These convert the energy in the sun's rays into direct current (DC).

Each solar panel delivers up to 130 Watts of electricity.

For our solar array we used two PX 130/6 solar modules, each of which produces a nominal maximum output of 130 Watts. We purchased these modules in advance from German manufacturer Sunset Solar; similar offerings from Kyocera and Sun Electronics are available in North America.

Specification tag from the solar module

To meet the values called for in the power output specs, the modules must be exposed in an area where incident solar energy achieves levels of at least 1,000 Watts/m2 at a radiation spectrum with an air mass (AM) of 1.5 (ozone value; see this explanation at Newport Corporation for all the related details) at a temperature of 77° F (25° C). Energy output from solar cells decreases as ambient temperature levels increase.

Because the efficiency of a solar converter decreases until it approaches the nominal maximum output during the first year of use, we purchased solar cells with about ten percent higher power output than we needed. That's why our solar cells also produce "extra power." Because we included two solar modules in our design, on peak sunshine days we have over 260 Watts at our disposal. For the polycrystalline silicon solar cells we chose for our installation, power conversion efficiency typically operates at about ten percent.

Over time, the position of the sun in the sky changes regularly. In Munich, it rises in the east, appears in the south at mid-day, and sets in the west. Because we wanted to collect as much solar power as possible, we positioned the solar cells for maximal efficiency, and set them up so they could orient themselves toward the sun automatically. Because the inclination of our arrays couldn't be completely optimal owing to technical installation issues, we were only able to collect 80% of the theoretical maximum from our arrays. Those who follow our lead will realize different levels of efficiency as well, simply because no real situation ever achieves theoretical perfection.

On those perfect sunny days where not a single cloud occludes the sky with between 8 and 18 hours of sunshine, we could theoretically accumulate up to 2.6 kWh of power. Assuming something less than perfection, particularly because of the ever-changeable weather, we assume that our actual collection will fall somewhere between 1 and 2 kWh less than that amount.