1. Defining CPS Challenges in a Sustainable Electricity Grid AUTHORS: Jay Taneja, Randy Katz, and David Culler Computer Science Division University of California, Berkeley Presenting by: Phanindar Reddy Tati

2.  Abstract  Introduction  The California Electricity Grid  Towards A Sustainable Grid  Opportunities for Cyber Physical Systems  Conclusion Contents:

3.  Cyber-Physical Systems (CPS) are characterized as complex distributed systems exhibiting substantial uncertainty due to interactions with the physical world. Today’s electric grids are often described as CPS because a portfolio of distributed supplies must be dispatched in real-time to match uncontrolled, uncertain demand while adhering to constraints imposed by the intervening transmission and distribution network. With the increased control complexity required by deep penetration of fluctuating renewable supplies, the grid becomes more profoundly a CPS and needs to be addressed as a system. In this evolving CPS, a large fraction of supply is under-actuated, a substantial portion of demand needs to become dispatchable, interactions among distributed elements are no longer unidirectional, and operating requirements of elements are more dynamic. To more sharply define these CPS challenges, we obtain a yearlong, detailed measurement of the real-time blend of supplies on the primary California grid dispatched to meet current demand and then scale the solar and wind assets, preserving uncontrolled weather effects, to a level of penetration associated with California’s 2050 GHG targets. In this representation of a future sustainable grid, we assess the impact of demand shaping, storage, and agility on the reconstituted supply portfolio, characterize resulting duration curves and ramping, and investigate the distributed control and management regime. We articulate new operational and market opportunities and challenges that may materialize from intermittent periods of abundance and scarcity in the overall energy network. We find that in a sustainable grid, lulls in renewable production during winter are more critical than peaks in demand during summer, capacity for load shifting and energy storage are more valuable as renewables penetration increases, and that grid balancing requires integrated management of supply and demand resources. Abstract:

4.  How Electricity Grid is a CPS?  As renewable resources increases, Grid gets more complex  Interaction among distributed elements are no longer unidirectional  System needs to be more dynamic  To discuss more sharply in real time, California Electricity Grid considered  In this paper, Authors discusses about  Sustainable Grid  Impact of demand shaping, storage  Investigated Distributed control and Management  New operational and Market opportunities, Challenges Continued… ABSTRACT

5.  A portfolio of electric power generation resources must be managed dynamically to meet an uncontrolled time-varying demand  Primary control loop is managed by an operator to avoid iterative unit commitment problem; based on a prediction of load, generation capacity  Matching of generation to load is refined through hour-ahead and 5- minute ahead markets based on recently observed demand  Generators to manage mismatches  Utilizing Information Technology- ‘SMART METERS’ Introduction: ABSTRACT INTRODUCTION

6.  Smart Meters  Monitors loads  Delivery of signal to trigger response from demand  Checks power quality at intermediate points Continued… Information PlanesPhysical Planes Classic Grid ABSTRACT INTRODUCTION

7.  Integration of large amounts of renewable resources makes the Electricity Grid more challenging  To achieve deep penetration of renewable resources  Zero-Emissions Load Balancing Continued… model LOAD-FOLLOWING-SUPPLYSUPPLY-FOLLOWING LOAD ABSTRACT INTRODUCTION

8.  PROBLEM: Maintaining the dynamic match between supply and demand in a grid with a deep penetration of Renewables  Methods:  Pervasive monitoring, modeling  Mitigation employing a rich information plane  Distributed intelligence  Basis for this Study:  Data released by California Independent System Operator (CA ISO)  Authors performed a scaling study if much larger array of renewable assets were deployed Continued… ABSTRACT INTRODUCTION

9.  Authors answering a question  What would the grid be like with a deep penetration of renewables today?  Not considering changes in Demand  Dynamics are not universal but Methodology is similar Continued… ABSTRACT INTRODUCTION

10.  CA ISO:  Independent, non-profit corporation that monitors, controls electric power  Has 25,865 mile network  Released hourly supply data for it’s 10 different types of generation sources The California Electricity Grid INTRODUCTION THE CALIFORNIA ELECTRICITY GRID

11.  Here, Overall demand is defined as the sum of these generation sources.  Electricity demand varies on multiple timescales:  Daily: Peaks in late afternoon  Weekly: Weekends 9.6% less than week days  Seasonally: Winter 15.8% less than summer  CHALLENGE: Matching highly-variable electricity demand with a portfolio of generation resources  33% of power should be produced from Renewable resources by 2020 (wind, solar, geothermal, biomass, biogas, hydroelectric) Continued… INTRODUCTION THE CALIFORNIA ELECTRICITY GRID

12.  Temporal Variations:  Nuclear resources- Stable base load  Hydroelectric- More power in summer  Thermal- To meet day-to-day variations Continued… INTRODUCTION THE CALIFORNIA ELECTRICITY GRID

13. Continued… Solar and Wind Power in California:  Solar -403MW  Wind -2.8GW  Day Time- More Solar power  Night- More Wind power  Combination could do better  Unpredictable resources INTRODUCTION THE CALIFORNIA ELECTRICITY GRID

14.  Scaling Methodology: To model a sustainable grid of scale CA ISO with a large fraction of renewable energy  Scale solar and wind each by constant factor  Reduce imports, thermal power until demand equals generation  Energy produced beyond present-day energy is Excess  Assumptions:  Proportional scaling of wind and solar hourly through yearly  Estimated solar based on distribution of length of the day  Geographic diversity of both wind and solar is similar in future  Authors selected 60% renewables threshold Towards A Sustainable Grid: THE CALIFORNIA ELECTRICITY GRID TOWARDS A SUSTAINABLE GRID

15. Continued… THE CALIFORNIA ELECTRICITY GRID TOWARDS A SUSTAINABLE GRID

16.  Characterization of a grid with 60% renewables  Summer, Excess power  Exported or used to enable new energy-agile practices  Winter, less power  Still has to meet day-to-day demand Continued… THE CALIFORNIA ELECTRICITY GRID TOWARDS A SUSTAINABLE GRID

17.  A grid with deep renewables as predicted in the sustainable grid, presents a family of CPS challenges and opportunities  Cooperative portfolio Management: Opportunities for Cyber Physical Systems THE CALIFORNIA ELECTRICITY GRID TOWARDS A SUSTAINABLE GRID

18. Continued… Loads-Following Supply  Operators controls supply to match the demand  Existing grids works on this Supply-Following Loads:  Shifts the part of burden of maintaining the match onto demand  From periods of deficit to excess  Shifts to thermal at points of deficit THE CALIFORNIA ELECTRICITY GRID TOWARDS A SUSTAINABLE GRID

19.  Use of Storage:  128GW storage/ worldwide  99.9% hydroelectric (Stores water)  Allows shaping of supply rather than demand and is substitutable for any type of power generation Continued… THE CALIFORNIA ELECTRICITY GRID TOWARDS A SUSTAINABLE GRID

20.  Load curtailment and Energy Efficiency:  From Summer to Winter, Operator targets the critical hours (where power generation is costly)  Reduction of energy consumption at any hour of the day becomes more valuable  More energy-efficient demand improves performance  Energy-storage is more valuable Continued… THE CALIFORNIA ELECTRICITY GRID TOWARDS A SUSTAINABLE GRID

21.  Modern electric grids are CPS  Build a model of what the grid would look like with sufficient sources to provide 60% of the electricity consumed  Introduced Supply-following loads  Discussed energy storage, demand curtailment  This study is preliminary step  These CPS efforts will move us a step closer to the sustainable grid design  As resources are being consumed rapidly, sustainable grid is necessary Conclusion: TOWARDS A SUSTAINABLE GRID CONCLUSION