dr. roger dougal professor university of south carolina
TRANSCRIPT
Dr. Roger DougalProfessorUniversity of South Carolina
Integrated Energy Management at Consumer
INTEGRATED ENERGY MANAGEMENT AT THE CONSUMER SITE
Roger A Dougal, Gregory Professor and Chair of EE
University of South CarolinaCo-director, GRAPES
Site Director, Electric Ship R&D Consortium
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Integrated Energy Management at Consumer
Energy Management System
Integrate renewable sources, energy storage, and load management in homesEfficient all-in-one power electronics package to manage DC and AC power flowsIntegrate smart grid, home, and web communicationsPermit islanded operation during outages
React to time-of-use or real-time pricingUse PV and battery to reduce consumption at peak timesManage loads, safely and transparentlyCoordinate plug-in electric vehicles (PEV)Participate in load curtailment programs with minimal inconvenience to homeowner Reduce monthly cost for customers
Reduce grid-side demand during peak times
Residential example
Integrated Energy Management at Consumer
The Opportunity
Widespread adoption of photovoltaics appears inevitable – competitive with user pricesOther on-site power alternatives (e.g. fuel cells) are likely to become viablePower pricing is volatile – minute-by-minuteReal time or time-of-use pricing encourages responsible power behavior – become more “Danish”Scheduling of power flows can produce financial rewardsEnergy storage is coming (even if only in the form of EVs)Local management of power offers price and security advantagesEmerging markets in power aggregation offer business opportunitiesUbiquitous internet permits coordination
Source: Photovoltaic (PV) Pricing Trends: Historical, Recent, and Near-Term Projections, US DOE Nov 2012
Source: PJM.com 2013-02-09
Integrated Energy Management at Consumer
Our Research Environment
Bring the EE perspectiveHybrid power sources, ship power systems – all tough power balancing problems because self-contained – like a microgrid.Multidisciplinary – power electronics, power systems, electrochemical power sources, pv power sources, energy storage, controls, thermal systems.
Integrated Energy Management at Consumer
Back to the FutureP
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Local dc Generation
Distant ac Generation Local dc Generation
Integrated Energy Management at Consumer
Time sensitive loads
Electric Power Problem is Partly a Thermal Problem
Shrinking:desktops becoming
iPads
Shrinking:Incandescents
becomingCFLs, LEDs
Better thermal efficiency of home envelope increases thermal time constant, and enables greater flexibility in power scheduling
Majority of residential electric
load is thermal
Time insensitive loads
Integrated Energy Management at Consumer
Opportunities to Reduce Cost
Reduce demandReduce loads , especially during peak pricing intervals – e.g. raise thermostatRespond to utility requests for curtailment
Time-shift consumptionMove loads temporally from peak price time to other time, e.g. pre-cool house, pre-heat water, before on-peak pricing intervalStore energy in battery, use or sell back to grid later
Manage renewable powerMove renewable power use to high price timesSell excess power to utility at high price times
Integrated Energy Management at Consumer
Why does Time affect Cost?
0 2 4 6 8 10 12 14 16 18 20 22 240
10
20
30
Hour
¢/k
Wh
On-peak
Shoulder
Off-peak
Winter pricing strategy
Morning peak Evening peak
Afternoon dip(insolation, not home, etc)
Characteristic winter day demand
~25%
Integrated Energy Management at Consumer
Southeastern Pricing Schedules
1 4 7 10 13 16 19 220
5
10
15
20
25
30
35
Hour
¢/kW
h
Time of Use Pricing is (currently) a consumer optionTOU schedules vary between providers, some offering two-tier and some three-tier Typically 12 hours off-peak and 6 hours on-peak; off-peak during weekendsSchedule varies by seasonSome utilities offer load curtailment programs: reduce baseline load for a period of time and receive a $/kW reward
TOU weekday schedule, SCE&G (www.sceg.com)
SummerWinter
Time Of Use pricing encourages “Danish” (responsible) behavior
Integrated Energy Management at Consumer
PV Power Feed-in Pricing
Time of use (TOU) is the most widely adopted time-varying pricing structure todayFeed-in tariffs vary widely throughout the country. More progressive states have high FITs for PV while others only accept solar energy at “avoided cost” (SC: Duke, Santee Cooper, SCE&G)Dynamic pricing mostly used for commercial and industrial sites as well as load curtailment programs
Integrated Energy Management at Consumer
Local Energy Management
DC - AC
Inverter
Current usual PV implementation:Grid-interactive inverter and “Net metering”. During grid failure, PV cannot supply house.
Smart power router with Grid Disconnect
Whole-house power management system:During grid failure, system operates independently from grid, “islanded mode” maintaining power supply within the house
=/≈≈/=
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Integrated Energy Management at Consumer
Every Instance Different
Electric AC and Water Heaterbuilt 1995 - 99
Electric AC and Water HeaterBuilt 1995 - 99
Electric Heating & Cooling Built after 2000
Electric AC and Water Heaterbuilt before 1986
Electric Heating & CoolingBuilt 1995 – 99
Built before 1985
Jan 1, 2008 Jan 2, 2008 Jan 1, 2008 Jan 2, 200812 AM 12 AM 12 AM 12 AM
0 0
0
0
0
0
30
30
30
30
30
30
kW
kW
kWkW
kW
kW
From AEP data
Six different homes, six different power characteristics
Integrated Energy Management at Consumer
Storage is Useful
Avg. Demand
TOU Price
TOU Price
PV production does not always align with price peaks
Storage is required to decrease demand during peaks
Urban house<3000 sq. ft,.Electric water heating, Built prior to 1986
Avg. PV power
Avg. Demand
Avg. PV power
Mis-alignment during winter
Better-alignment during summer
Integrated Energy Management at Consumer
Power Conversion Circuits
Integrated Energy Management at Consumer
Control Hierarchy
System control is the highest decision-making level – the one that interfaces to external data sources and controlsApplication control layer bridges between the system and three lower control layersHardware control manages specific low-level switching actions at high frequencies (10’s of kHz and up) to manage voltage and current behavior for
Battery charge and dischargePower extraction from photovoltaicAC power flow to or from the grid
Integrated Energy Management at Consumer
Some Control Inputs
Battery charge or discharge rate
Thermostat setpoints
Power pricing
Battery state of charge
Predicted heating/cooling demands
Temperature
Wind
Rain/skycover
Water tempAnticipated PV production
Homeowner comfort preferences
Homeowner activities and behavior
Room temp
Anticipated next day
Actual next day
High LevelControl Decisions
Integrated Energy Management at Consumer
System Control
System control algorithmsBattery state-of-charge and state-of-health estimation Weather forecast and corresponding prediction of power consumptionPower price and estimated price behavior (in short-term markets)Load and homeowner behavior predictionPV power prediction
Integrated Energy Management at Consumer
Reduce On-Peak Demand
Solar power is small during (winter) morning and evening peaks.
Battery storage is required to shift energy into on-peak periods.
Integrated Energy Management at Consumer
Even Just a Battery Saves Money
Battery depth of discharge limited to 40%Charger and inverter costs/efficiencies consideredPayback period (including battery change-out) is 14 years(very dependent on power pricing, of course!)
No PV installed
Results from simulation
$0.20 /kWh on-peak
$0.06 /kWh off-peak
Price
Shift consumption from on-peak to off-peak
Integrated Energy Management at Consumer
System with Battery and PV
Complete system with 50 kWh batteries and CA=0.50 (kWp rating = 50% of daily energy demand in kWh)Customer #2 has a payback period of 15.44 years and displaces 9.90 MWh of on-peak energy consumptionAdding more PV capacity – e.g. say twice as much PV array
Does little to further decrease on-peak energy consumptionDramatically increases the payback period
Integrated Energy Management at Consumer
Short and Long Term Pricing22
Highly variable pricing
Many different power markets on different time scales.
In some markets, values can sometimes be negative
Encourages creative power management strategies
edata.pjm.com
Integrated Energy Management at Consumer
Extend to Commercial Customers23
Building Agent #1 Building Agent #2
Load & Source Agents Load & Source Agents
Status & Sensor Data Status & Sensor Data
Negotiation Agent
PVDiesel Gen
HVAC Battery Wind Lighting
Weather Data
(Internet)
Negotiation or biddingstrategy use
Requests for load curtailment
Weather Data
(Internet)
Market Price Data
(Internet)
Power Provider
Integrated Energy Management at Consumer
Representative Commercial
Nursing home in upper Midwest50 kW max demand
1 17 33 49 65 81 97 1131291451611770
10
20
30
40
Jan 6, 2012 Jan 7, 2013
kW
12 AM 12 AM
Measured power demand
Integrated Energy Management at Consumer
Forecasting Methods
Need to predict load and DERs available for bidding and energy management
Long-term - Seasonal or monthly baselineDay-aheadVery Short-term (15-min)
Several forecasting methods were examined
AutoregressiveExponential smoothingKalman based correction (for very short term)
Forecasting algorithms used by negotiating agent
Forecasting performance of day-ahead load and weather forecasting
4/6/2012 0:00 4/6/2012 5:00 4/6/2012 10:00 4/6/2012 15:00 4/6/2012 20:000
10
20
30
40
50
60
70
80
90
100
0
10
20
30
40
50
60
Nursing Home Day-Ahead Load & Temperature Forecast, Friday, April 6,
2012
Actual Load (kW) Forecasted Load (kW)Actual Temp (°F) Forecasted Temp(°F)
Load
(kW
)
Tem
pera
ture
(°F)
Forecasted Temp.
Forecasted Load
Error=5.90 %
Integrated Energy Management at Consumer
Load Leveling Strategy26
Battery storage only, no PVLimit peak grid demand to 35 kW (target)Uncertainty included for
Day ahead forecast15 min. battery scheduling
Grid demand limit is sometimes exceeded because of limited battery capacity
Integrated Energy Management at Consumer
Static On-Peak Shaving Strategy, with PV
On-peak
Off-peak
PV offsets grid demand
Battery is recharged during off-
peak
Battery peak shaving (2.7 kW) &
Curtailment (16.5% baseline)
Battery peak shaving (2.7 kW) &
Curtailment (16.5% baseline)
Battery is recharged during off-
peak
Accurate forecasted
peak matching
Lowest MAPE day forecast (5.9%)
Cloudy Day
Total Savings = $74 (24%
reduction)
Integrated Energy Management at Consumer
Presentation Take Aways
Energy storage and photovoltaic sources coordinated through power electronics and intelligent controls can provide cost benefits to residential and commercial power customers
Smart scheduling and coordination of power resources can have significant financial benefits and increase uptake of renewable energy resources
Many renewable sources of electric power are highly-variable, and non-dispatchable. Loads may be semi-predictable but only partially manageable. Load buffers are essential (batteries, or fast-ramping sources)
Sources fueled by renewable fuel would do well to consider ramp rate requirements and not assume constant output conditions. We can’t all try to be like nuclear plants!
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Dr. Roger DougalProfessorUniversity of South Carolina