Today’s post comes from my reading of Google Cites Progress on Thermal Solar. Let’s take a look at thermal solar power and see how it might apply to the green data center.
Unlike solar cells, which convert sunlight directly to electricity, thermal solar uses a field of mirrors (called heliostats) that focus the sunlight on a boiler at the top of a central tower. The resulting steam drives a turbine, which drives a generator, to produce electricity.
So what are the pluses and minuses of solar cells vs thermal solar? Solar cells are expensive to make and far less efficient than thermal solar. In a thermal system, the mirrors can also follow the sun, getting maximum benefit from the sun. The steam generated by the boiler can also be used to generate power through the night, when solar cells wouldn’t function at all. Also, the mirrors of the thermal system can be replaced without interrupting power generation. Both the mirrors of the thermal system and solar cells require cleaning to maintain efficiency.
On the other side of things, thermal solar is far more complicated than solar cells and it doesn’t (yet anyways) scale down to small installations. Thermal solar requires a large amount of space for the mirror field, so you’re not going to see this occupying the wasted space of a flat data center roof!
So, just how does thermal solar fit in to data center green energy? I see this only being practical for the very largest facilities, with large amounts of clear flat space for the mirror field (kind of negates the green benefit to cut down tons of trees to build this type of facility), and lots of sunlight.
On the bad side, lots of sunlight implies a location with high ambient air temperatures, so no energy saving from free air cooling. Add to that having a massive flat roof absorbing heat from the sunlight without the shade of a solar cell array to keep it cool and I have to question whether this is a practical idea at all.
Vern, SwiftWater Telecom
Data center, web hosting, Internet engineering