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Can the Sun Realistically Power Datacenters?
1sockchuck writes: A massive solar array in central New Jersey provides the daytime power for a server farm delivering online financial services for McGraw Hill. The 50-acre field of photovoltaic solar panels symbolizes a new phase in the use of renewable energy in data centers. Massive arrays can now provide tens of megawatts of solar power for companies (including Apple) that can afford the land and the expense. But some data center thought leaders argue that these huge fields are more about marketing than genuinely finding the best approach to a greener cloud.
Can a certain number of solar panels power a datacenter with a given load? Sure! Just not 24/7. But that doesn't mean they can not. Your datacenter takes 1 MW/h. You receive roughly 8 hours of usable sunlight, so you need 3MW/h capacity of solar panels to produce the power you need. During the day, the power company will take your excess power, and light up factories, offices, Air Conditioning, etc... During the night, you will use the power company to power your datacenter, when it has to keep its power systems up anyways, and therefore has excess capacity. Look up the terms "base load" and "peak load", understand that not everything that plugs into the power grid needs to be up 24/7 ( not even all servers, look up "DRS"). So can that much power be produced to have a "net neutral" load on the grid? Sure!
But there is always the desire to be completely self-reliant. In this area, I always liked the idea of using the excess power during the day to lift water to a lake high up, and running hydro at night to power the datacenter. This is of course expensive, especially since power companies have excess power at night anyways, since the cycle time to stop / start producing base power won't allow the company to shut down X generators at night.
Average solar insolation is more like 5 sun-hours/day, not 8, in good locations. Much less in places like Germany. If you want autonomy on the shortest day of the year, you may have less than 2 full sun hours, which means 12 MW of capacity, but that doesn't account for a cloudy day, in which case you may get less than 1 full sun hour insolation.
So, bottom line is there are a lot of ways to look at the numbers, but to be truly autonomous with no grid support, you need a lot of capacity.
Sadly, there just aren't enough places with lakes to store anything like the amount of power we'd need to store.
This is actually a silly concern. Electricity demand is highest in the middle of the day when the sun is shining. That is also when the spot price for power is highest. It makes no sense at all to store that power to sell it in the middle of the night, when prices are far lower.
Storing solar power is an issue in niche applications, and it is an issue in a future fantasy world where 100% of our power is solar. But it is not an important issue in the real world, and is unlikely to be for a long, long time.
data centers generally aren't lacking for available roof space so no taking up any more land.
Above the atmosphere, at the equator, the average insolation (that is, the amount of incoming solar energy, averaged over the course of a day) is about 400 watts per square meter. At the bottom of the atmosphere in an ideal location (like the Sahara) it's closer to 300 W/sq. m. In most places where people want to have data centers, the number is closer to 200 W/sq. m...or worse. And the efficiency of commercial solar panels runs about 20%, so you're down to 40 watts per square meter.
200 watts is (optimistically) about the draw of a single server, so you're looking at powering one server for every five square meters of rooftop. If you want to run on rooftop solar, then you're going to have to design a data center with very short racks and very wide aisles.
~Idarubicin