Energy  Management  in  Smart  Houses  with  Ba5eries,  Renewable  Energy  and  Context  Awareness  Baris  Aksanli,  Jagannathan  Venkatesh  and  Tajana  S.  Rosing  

University  of  California  San  Diego  

 MoHvaHon  

Renewable  Energy  and  Context  Awareness  

•  ResidenHal  energy  –  38%  of  total  energy  consumpHon  •  HVAC  and  appliances  –  80%  of  the  residenHal  energy  

A  smart  house  includes  renewable  energy,  ba5eries,  sensors  to  track  the  consumpHon  

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Pow

er (W

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Hour(h)

Renewable Gen Renewable Available Grid Consumption Battery Consumption

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Renewable Gen Renewable Available Grid Consumption Battery Consumption

Without  smart  control  and  ba5eries,  a  significant  amount  of  renewable  energy  can  be  wasted  

Residences  operate  in  a  constantly  changing  context:  •  UHlity  pricing  •  Renewable  energy  availability  •  User  behavior,  etc.  Leverage  context  to  save  operaHonal  energy  costs  

Energy  Genera.on/Consump.on  Predic.on  §  Predict  renewable  energy  genera/on  and  appliance  

energy  consump/on  over  a  24  hour  period  

Time  of  Day  

Day  of  Week  

Power  @  Interval  

Time  of  Day  

Day  of  Week  

On/Off   Mode  

User  Presence  

User  Presence  

Context-­‐Sensi.ve  Appliance  Modeling  §  Model  appliance  energy  use  with  constant,  linear,  

&  polynomial  models  §  Dependent  variables  are  context  variables  

(ambient  light,  user  presence,  etc.)  §  Extend  models  to  change  behavior  based  on  

context  Smart  Appliances  §  Schedule  appliances  based  on  predicted  energy  

availability  §  AddiHonally,  schedule  within  thresholds  based  

on  Hme-­‐of-­‐use  uHlity  price     Fixed Distributed Rescheduled Ideal

Avg.  Weekly  Grid  Energy(kWh) 65.3 41.5 30.8 26.4

Avg.  Weekly  Solar  Power  Use  (kWh) 22.2 39.9 47.7 50.1

Green  Energy  Efficiency  (%) 23.1 41.5 49.8 52.3

Scheme Light  (Lux) Power  (W) T o t a l   E n e r g y  (kWh)

Binary 472 175 21 Leveled 423 124 14.8 Automated 398 102 12.24

Ligh.ng  Automa.on  §  Automate  based  on  ambient  light  

intensity  and  user  presence  

HVAC  Automa.on  §  Automate  based  on  ambient  

temperature,  predefined  thresholds,  and  user  occupancy  

  Energy  (kWh) Energy  Price  .    

($/kWh) Net  Cost  ($)

Normal    consump.on 340.20 0.24 82.08

Context-­‐aware  consump.on 270.43 0.19 52.12

Ba5ery  ConfiguraHon  Study  Ba5eries  provide  energy  at  higher  electricity  prices  and  recharge  at  lower  prices.  

Previous  studies  do  not  model  the  nonlinear  properHes  of  the  ba5eries.  

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Eff

ectiv

e C

apac

ity (A

h)

Current (A)

LFP LA

Battery lifetime vs. depth-of-discharge Effective capacity vs. discharging current

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DoD level

LFP LA

Ba6ery  configura/on:  1.  Ba5ery  type  2.  Ba5ery  capacity  3.  Depth-­‐of-­‐discharge  limit  4.  Discharging  current  

BaWery  Configura.on  Analysis  1.   Capacity  Analysis:  Should  be  scaled  up  to  

meet  the  energy  demand  of  the  house.  2.   Discharging  Current  Analysis:  Should  be  

scaled  down  to  C/10-­‐C/20  interval  to  avoid  negaHve  effects  of  high  currents.  

3.   Depth-­‐of-­‐discharge  Analysis:  Depends  on  the  ba5ery  type.  For  LA  ba5eries,  it  is  around  20-­‐30%  and  for  LFP,  around  50%.  

2-day power profile of 3 houses from MIT REDD data set

Time Interval Pricing Case 1 Pricing Case 2 Peak 7am – 11 pm 35 ȼ/kWh 45 ȼ/kWh

Off-peak 11 pm – 7 am 10 ȼ/kWh 10 ȼ/kWh

Sample one-day CAISO electricity pricing

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12:00 AM 12:00 PM 12:00 AM

Ene

rgy

Cos

t (ȼ/

kWh)

Time

  LA LFP Capacity  (Ah) Savings  ($) Capacity  (Ah) Savings  ($)

House  1 N/A

359 298 House  2 138 89 House  3 324 233

Best battery capacity for Case 1 pricing

  LA LFP

Capacity  (Ah) DoD Dis.  Cur.  

Rate Capacity  (Ah) DoD Dis.  Cur.  

Rate House1 624 20% C/20 359 60% C/20 House2 255 20% C/20 138 60% C/20 House3 497 20% C/20 325 60% C/20

Best battery configuration for Case 2 pricing

  LA LFP Capacity  (Ah) Savings  ($) Capacity  (Ah) Savings  ($)

House  1 624 481 359 1145 House  2 255 166 138 413 House  3 497 352 325 1006

Best battery capacity for Case 2 pricing Best  configuraHon  with  C/20  current  and  60%  DoD  

This  work  was  supported  in  part  by  TerraSwarm,  one  of  six  centers  of  STARnet,  a  Semiconductor  Research  CorporaHon  program  sponsored  by  MARCO  and  DARPA.