The Logic of Energy Efficiency Alan Meier Lawrence Berkeley Na8onal Laboratory & UC Davis Energy Efficiency Center The Ques8on You want to remove 1 gram of mass from a car and obtain the greatest possible increase in vehicle efficiency. From what part of the vehicle do you remove the 1 g? A Demand-Side Perspective
Treating Energy Demand as a Black Box (and note the assumptions!)
https://flowcharts.llnl.gov/content/energy/energy_archive/energy_flow_2009/LLNL_US_Energy_Flow_2009.png
Electricity
Generation
Oil Gas
Use
Hydro
Everything else
Nuclear
Coal
Motors !
Electricity
Generation
Use
hydro
Everything
else
refrigerators
Everything else
Electricity
supply and demand
Oil
Supply
Consumption
Tire rolling
resistance
Saudi Arabia
Everywhere
else
Everything
else
Refrigerator Energy Use Over Time
United States Refrigerator Use v. Time
25
1,800
1,600
20
1,400
1,200
Refrigerator
Size (cubic ft)
15
1,000
800
10
600
Energy Use per Unit
(KWH/Year)
400
5
200
0
1947
0
1952
1957
1962
1967
1972
1977
1982
1987
1992
1997
2002
Refrigerator volume (cubic feet)
Average Energy Use per Unit Sold (kWh/yr)
2,000
Retrofit & Replacement (~1990)
Refrigerator Energy Use Over
Time
United States Refrigerator Use v. Time
25
1,800
1,600
20
1,400
1,200
Refrigerator
Size (cubic ft)
15
1,000
800
10
600
Energy Use per Unit
(KWH/Year)
400
5
200
0
1947
0
1952
1957
1962
1967
1972
1977
1982
1987
1992
1997
2002
Refrigerator volume (cubic feet)
Average Energy Use per Unit Sold (kWh/yr)
2,000
End Use Breakdown in a Single Building
A typical grocery
store has 150 –
200 electric
motors
Can you make a
chart like this
for a ship?
A device transforms energy into a
useful output, service, or product
Input
energy
Device
Losses
Output,
service,
product
A Service Plot Input Energy
Input energy required to provide
a level of service
pe
o
l
s
=
cy
n
e
ci
ffi
1/e
Output needed to
provide a level of service
Fixed consumption
(standby)
0
1
2
3
4
5
6
15
8
9
Output
Devices convert energy into some sort of output that provides a service. 10
Energy Use of Escalators:
Active & Standby
Propor8ons of ac8ve and standby mode to overall energy consump8on of two escalators. PowerConsumption
Consumption of
of Various
Today's Set-Top
Set TopBoxes
Boxes by Mode
Power
Standby/Off Mode
Consumption
(watts)
80
Standard
Receiver
n = 25
70
Active Mode
Stand-Alone
Digital
High Definition
Video
Recorder
(DVR)
(HD)
n = 8
Receiver
n = 9
Standard
Receiver
with
DVR
n = 5
HD
Receiver
DVR
n = 10
60
50
Power
40
30
20
10
0
•
•
Power consump8on does not differ significantly by mode No meaningful sleep or auto power down modes detected in any of the boxes surveyed. with
A Service Plot for Water Heating
A
Reduce demand
B
Input Energy
Reduce standby
C
Raise efficiency
D
E
0
1
2
3
Reduce demand
4
5
6
15
Output (liters of hot water)
8
9
10
Rack Design Strongly Affects Fuel Consump8on Drag Force (kiloNewtons) 16 12 8 4 0 Source: Whispbar 2011 Vehicle Alternators •  A car alternator generates about 800 kWh/year –  1/10 of average residen8al electricity use –  Cost of electricity is $1/kWh, about 5 x higher than grid electricity and about the same as PV electricity •  Virtually no literature on measured efficiency and output •  Alternator capaci8es are growing every year because of increasing electrical loads Categories of Energy-­‐Saving Ac8ons •  Direct energy savings –  Reducing demand for output –  Raising efficiency –  Reducing fixed consump8on •  Indirect energy savings –  Linked ac8vi8es –  Upstream/downstream ac8vi8es –  Savings through re-­‐design •  Changing the rules of the game Fuel Costs Usability is Important An interface that is difficult to use is an obstacle to correct opera8on An interface that is difficult to use is an obstacle to energy-­‐efficient opera8on – Digital programmable thermostats, plug-­‐in hybrids, u8lity bills, etc.
Thermostats Are Confusing to Operate Programmable Thermostats Recently Energy Star concluded that homes with programmable thermostats were using more energy than homes with manual thermostats In 2008 Energy Star terminated the specifica8on for programmable thermostats un8l it could “fix” the usability problem Goal: Quan8fying usability gives manufacturers and regulators a means of measuring improvement Premise: Improving the usability of thermostats will facilitate energy-­‐saving behavior How to Measure Usability in Thermostats? And now the video … How to Measure a Thermostat’s Usability? 1.
2.
3.
4.
Define tasks Quan8fy peoples’ ability to accomplish tasks Compute “score” based on metrics Compare to reference model Define Tasks Task 1: Turn the thermostat from off to heat. Task 2: Set the correct 8me. Task 3: Iden8fy the temperature the device is set to reach. Task 4: Iden8fy what temperature the thermostat is set to reach for Thursday at 9:00 PM. Task 5: Put the thermostat in hold or vaca8on to keep the same temperature while gone. Task 6: Program a schedule and temperature preferences for Monday through Friday. Details of Usability Tests •
•
•
•
•
•
5 thermostat interfaces 31 par8cipants 2 interfaces per person 6 tasks for each test 62 tests total > 350 videos! Distribu8on of Times for Subjects to Complete Task 1 Task 1: Turn the thermostat from off to heat. Average Time to Complete a Task by Model (a simple metric) Task 1: Turn the thermostat from off to heat. Conver8ng Task Time & Success into a Metric “Combined Comple0on Coefficient” #
ex &
M i = 2c%1 "
x(
1+
e
$
'
Where,
"0, if subject failed to complete task%
'
c =$
1,
if
subject
completed
task
#
&
t
x=
k
t = time for subject to complete task (in seconds)
!
k = an empirically - derived constant weighting
value of failures to complete
Note that Mi will always be between 0 and 1.
!
“Combined Comple8on Coefficient” based on 3 tasks – A Usability “Score” Conclusions Many different approaches to saving energy 1.  What are the services provided? 2.  Where does the energy actually go? 3.  What kinds of conserva8on measures can be applied? 4.  What are the economics? Think about removing 1 g …. end akmeier@lbl.gov Pentagon Fuel Study Findings
What Does Poor Usability Look Like? What “state” is
the device in?
What do the
labels tell us?
“folk labeling””