1 Towards Slack Analysis Prabal Dutta and Jay Taneja LoCal Winter Retreat January 15, 2010

2 Motivation: the changing energy landscape Dispatchable Sources Oblivious Sinks Non-Dispatchable Sources Aware Sinks

3 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%

4 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

5 “Doing Nothing Well” on the desktop Before installing AutoShutdownManager After installing AutoShutdownManager ~100x

6 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?

7 The matching problem

8 Outline Problem Solution Sketch Source Example Sink Example Other Opportunities

9 What not to do: forced load shedding

10 Load sculpting by squeezing, shifting, and splitting

11 Towards a methodology for sculpting

12 Outline Problem Solution Sketch Source Example Sink Example Matching Problem

13 Average hourly wind speed over one year

14 Average hourly wind speed over one year

15 Change in average hourly wind speed

16 Change in average hourly wind speed

17 Probabilistic “slack” in energy production p > 30% p > 20% p < 10% With 90% probability, Average wind speed will change less than ±2 mph in the next hour

18 Outline Problem Solution Sketch Source Example Sink Example Other Opportunities

19 A “LoCalized” refridgerator Switch/Meter Energy Storage Temp, Hum, Light Sensors

20 The life of the kitchen fridge

21 Refrigerator operating cycle

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

23 Aggregating temporal slack

24 Towards a measure of energy slack

25 Outline Problem Solution Sketch Source Example Sink Example Other Opportunities

26 Generalizing to the home

27 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