Ramp mitigation through short-term solar forecasting

Predictive Learning for Energy Storage Dinos Gonatascpgonatas@cpg-advisors.net(978) 254-1301

Ryan HannaCenter for Renewable Resources and IntegrationMechanical and Aerospace Engineering UCSDrehanna@eng.ucsd.edu

1UCSD Microgrid

Overview:42 MW Peak Load- 66% efficient27 MW gas cogeneration10,000 tons steam-chillers7,800 tons electric chillers

Energy Storage:3MW/ 6 MWh2MW/ 4MWh BYD systemZBBSanyoBMW 2nd life battery

UCSD Battery/ BMW Project

UCSD Battery/ BMW Project

UCSD Solar ForecastingWhy Forecasting?Why Forecasting?

Anticipating where ball is going to be

Cornerback Malcolm Butler acts on prediction to affect outcome(decisive play clinching Superbowl 49)

Use CasesBuilding load forecasting + batteries (and/or PV)Grid Storage/ non-transmission alternativesRamp smoothing for PV generationArchitecturePredictive analytics collects and analyzes sensor data/ grid statusDrives optimization engine, controlling battery state of charge, eg. with Modbus interfaceInvertersEnergy Storage/ BMSPredictive AnalyticsSystem Optimization/ batery controlsSensordataGridstatusWeather/ other dataMicrogridBuilding Load Forecasting

6 hour forecast: using previous time history + weather dataKey for deciding when to charge/ discharge battery for demand managementpredictionactual12Economics of Bad ForecastsSolar Ramp Problem 14ImplicationsLarge production fluctuations cause instability in weak electric grids such as Hawaii, Puerto RicoPenalties imposed when output changes more than 10%/minute Avoiding penalties using batteries for storing excess production is $$$

How to Smooth Out Steep Ramps?Ramp exceeding limitsProposed Solution: Smart Ramp Smoothingby Predicting Impending Power Changes

+Sky Imaging Camera/Production ForecastingPV + Inv controlPV + Forecast PV + StorageInverter and Battery Controls17Smart Forecasting AlgorithmGreen: measured black: USI nowcast red: USI 15 min forecast issued at 1732

Power Generation (arbitrary units)Plant APlant BPlant CPlant DLarge altocumulus cloud field is about to shade the plants18Cloud Prediction Using Sensor ArraysPredictions from SMUD sensor array19Simulated 5% Ramp Control w/o Forecasting: Steep Output Ramps 5% ramp limitRamp Smoothing With BatteriesWithout Forecasting5% ramp limitRamp SmoothingWith ForecastingRamp smoothed outBattery cycle anticipates PV ramp(just as football player anticipates where ball is thrown)

Knowing Future Production Mitigates RampsRamp smoothed outKnowing Future Production Mitigates RampsRamp smoothed outRamp Violations Eliminated With Right Combination of Forecast and Battery10% Ramp limit24kW PV array

For a battery of a given size, discharging it less extends cycle life (= cost reduction)

DoD 80% 3000 cycles

DoD 60% 5000 cycles

DoD 40% 10000 cyclesConclusions:Implementing forecasting in energy storage can enhance performance 2xReduce battery size 50%, or with fixed battery size, enhance performance or reduce cyclingSame as lowering battery cost