Michael Kanellos at Greentech media has a story about an interesting concept for energy reduction that is new to me: switching a data center to DC power.
SAP is making some energy retrofits to save money, and while the three biggest savers are the usual ones that we all know about (substitute a solar array for utility power, switch lighting to LEDs, cut airfares by videoconferencing, ) the fourth caught my attention. SAP is converting their data center to DC.
Solar panels make power in DC current, and they lose some efficiency by having to be converted (that’s what inverters do) to AC. So this will leverage the investment they are also making in solar: about $1.2 million. Like most businesses who get their own renewable power, they will save big time just by making their own energy with solar.
But, their planned solar array would produce about 15% more if it could be used without an inverter by being delivered directly in its native DC current. A 24 KW DC system will deliver about 20 KW of power once converted to AC. Conversion to AC loses about 15%.
They figure that with this move to go DC in the data center, if the solar was able to deliver its DC current straight to the data center without any losses due to conversion to AC, that would save as much as 40 percent of their power consumption.
Without their own solar, but just regular utility AC, they calculate conversion to DC for the data center would save only 15 to 20 percent.
This is an exciting experiment. Nobody has tried this, to my knowledge, at least not on this scale. Off-gridders and RV-ers use DC appliances so that one tiny solar panel can more efficiently power a computer and a fridge etc, but SAP is on a different scale.
Alternatively, just to convert the data center to DC current, without going solar, would involve installing a ” rectifier” that can convert grid AC power to DC to run the computers and storage equipment. DC rectifiers save power by reducing the number of times power gets converted from AC to DC and vice versa before it powers a server.
But if they could eliminate the step of converting to AC, using solar off the roof, the DC rectifier could take a nap and just take raw solar power in its natural state: DC. This would save money twice: no $128,000 rectifiers to convert grid AC to DC, plus no inverters to convert the roof solar to AC, before it gets “rectified” again back into DC.
Worth taking a look at how this could be done: an exciting experiment.
Image: Daniel Howherd
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