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Towards Slack Analysis

Prabal Dutta and Jay Taneja

LoCal Winter RetreatJanuary 15, 2010

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Motivation: the changing energy landscape

Dispatchable Sources

Oblivious Sinks

Non-Dispatchable Sources

Aware Sinks

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Growing fraction of energy sources are renewable

• Renewables Portfolio Standard (RPS)– 36 of 50 states have set goals– Range from 10% to 25%

• California RPS– 2008: 10% (actual) – 2010: 20%– 2020: 33%

• California Mix (2008)– Biomass: 2.1%– Geothermal: 4.5%– Small Hydro: 1.4%– Solar: 0.2%– Wind: 2.4%

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Implications of “Do Nothing Well”

TX packet at 1% duty cycle (20 ms / 2 s)

4,000 ms

640,000 ms

86,400,000 ms

[Farkas00]

30 ms

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“Doing Nothing Well” on the desktop

Before installingAutoShutdownManager

After installingAutoShutdownManager

~100

x

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Over the next decade

• Sources– Increasingly non-dispatchable– Geographically distributed– Non-dispatchable loads are economically derated

• Sinks– Increasing power-proportional– Increasingly networked and intelligent– Increasing numbers of plug-in hybrid electric

vehicles

• The question: how to match supply and demand?

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The matching problem

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Outline

• Problem

• Solution Sketch

• Source Example

• Sink Example

• Other Opportunities

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What not to do: forced load shedding

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Load sculpting by squeezing, shifting, and splitting

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Towards a methodology for sculpting

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Outline

• Problem

• Solution Sketch

• Source Example

• Sink Example

• Matching Problem

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Average hourly wind speed over one year

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Average hourly wind speed over one year

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Change in average hourly wind speed

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Change in average hourly wind speed

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Probabilistic “slack” in energy production

p > 30%

p > 20%p > 20%

p < 10%p < 10%

With 90% probability, Average wind speed will change less than

±2 mph in the next hour

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Outline

• Problem

• Solution Sketch

• Source Example

• Sink Example

• Other Opportunities

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A “LoCalized” refridgerator

Switch/Meter

Energy Storage

Temp,Hum,Light

Sensors

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The life of the kitchen fridge

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Refrigerator operating cycle

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Temporal slack

Average Slack = 25 min (per 41 min cycle)Average Energy per cycle = 0.05 kWh

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Aggregating temporal slack

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Towards a measure of energy slack

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Outline

• Problem

• Solution Sketch

• Source Example

• Sink Example

• Other Opportunities

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Generalizing to the home

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Many, many open questions

• Slack metric– A single value?– A portfolio of values?– A CDF?– Formalization– Positive slack vs negative slack?

• Sculptability of other loads?

• Sculptability of other sources?

• Algorithms for dynamic demand response– Match, in real-time, sources and sinks