Balance of Power

Electrical, not political. A DOE study found that - duh - if you give consumers information about time varying cost of electricity they will save money by shifting some power usage from peak to off-peak times. Consumers in the study lowered their electric bills by 10% and lowered their peak demand by 15%. This is a big deal because although the operating cost component of electricity (fuel) depends on the total energy consumed, the capital cost component (generating plants) depends on the peak power generation.


Solar power is particularly valuable to a utility because its peak production occurs in the middle of the day when summer demand from air conditioning is highest. But there's another peak around 5-6 when people come home from work and turn on appliances, and by then solar power production has fallen off. Thus adding photovoltaic power alone may not drastically reduce peak requirements for fossil fuel power plants.


Wind power along the California coast has an almost complementary generation curve to that of solar power, because of the onshore and offshore breezes in the mornings and evenings. Adding wind power alone may not drastically reduce peak fossil demand because the wind often dies down mid-day when the air conditioning load is highest.


But adding solar and wind power together could greatly reduce peak fossil demand, though perhaps not economically eliminate it entirely. Then if you added time of day metering to allow consumers to voluntarily shift their load, that would level even more peaks. Ditto various energy storage systems like the plan to use night time wind power to pump water back up a hydroelectric dam for use the next day, super capacitors, and plug-in hybrid cars. The key to effective and economical use of renewable energy is a balance of power supply with demand.


The computer industry tries to do the same thing with servers. Demand for computing services typically follows daily, weekly, and monthly cycles. When the data center is provisioned for the highest possible demand, there is a lot of wasteful excess capacity. Even with the most efficient hardware and the best power management software, running servers at low utilization is extremely wasteful compared to moderate utilization. So we try to balance computing supply with demand by virtualization and workload consolidation, especially if we can find workloads that are complementary (like wind and solar) in their resource requirements and/or their load versus time of day.


As network capacities increase and software becomes more sophisticated, you can imagine systems configuring computing resources worldwide to maximize computing power to the customer at minimum electric cost. Think of a customer connected from California in the middle of a hot day with time-of-day electric meters set to the highest price. Of course he might be routed to servers in Europe or India where the computing demand is off peak. He might also be routed to servers in Colorado where the computing demand might still be high, but the electricity demand and price might be lower. Or to Oregon where a heavy rainfall and cold wave might mean cheap renewable hydro-power, even at peak electric demand; and lower than usual data center cooling costs thanks to mixing filtered outside air.

Comments:

[Trackback] The Demand Response Research Center (DRRC) at LBNL provide a system that enables electric utility customers to automate energy load shedding during peak demand periods.  It's called Demand Response Automation Server (DRAS) .  Basically, ...

Posted by What happens downstream? on January 10, 2008 at 02:10 PM PST #

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I am a software engineer in San Diego, president of the Standard Performance Evaluation Corporation (spec.org), formerly a mathematician and a violist.

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