Online proceedings - EDA Publishing Association

Power monitoring data detected by wireless sensor nodes
was analyzed in individual stores. The result obtained in one
store was summarized in Fig. 5, showing the result of power
profiling of CVS. Horizontal axis presents day’s average
temperature in Tachikawa area (in the center in terms of
north and south and a little west of Tokyo Metropolitan area).
Power consumption of display cooler and freezers and
air-conditioning changed largely with temperature. More
detail, power consumption of display cooler increases in a
parabolas fashion with increasing temperature. That of
air-conditioning shows minimum around 15 degree in spring
and autumn season. These changes cause this trend of total
power consumption of CVS against average temperature.
On the contrary, power consumption of equipment worked
by “single-phase AC” and some equipment worked by
“three-phase AC” kept almost constant with temperature
changes. There is a lot of equipment worked by single-phase
AC. As shown in Fig.6, the equipment used on shop counter,
such as heating food and coffee machine, and lighting shows
large contribution to total power consumption. It can be
assumed that power consumption of single-phase AC shows
similar values due to day’s temperature.
Single-phase AC (200V)
Wireless
Sensor Nodes
Three-phase AC (200V)
11-13
May 2011, Aix-en-Provence, France
Power Consumption kWh/day
Though the equipment of store H is older than that of store J,
power consumption of store H shows similar changes with
the store J. This is because store H has good installation
environment of outdoor-unit. On the contrary, the oldest
equipment of store F shows different changes with other
stores. This may be caused by degradation of equipment and
characteristic with non-invertor.
Store G
Microwave
Lighting
(shop, name board)
Water heater
Lighting
(equipment)
Heating food,
Coffee-machine etc.
Fig. 6. Power consumption of individual equipment in single-phase AC.
.
300
250
200
150
100
50
Display Cooler and Freezers (Walk-in Type)
2000/8(6horsepower,6doors)
Deteriorated equipment
Different environment “outdoor-unit”
2005/8(6horsepower,6doors)
Energy-saving equipment
2006/8(6horsepower,7doors)
ATM
2005/4
(6horsepower,7doors)
東 D文 化
武 F蔵 砂 川
多 G摩 関 戸
砂 J 川
矢 H野 口
2010/3(8horsepower,7doors)
Fig. 4. Example of sensor installation.
0
0 5 10 15 20 25 30
Average Temperature ℃/ day
Fig. 7. Estimate cause of power difference between stores.
Power Consumption kWh/day
900
800
700
600
500
400
300
200
100
0
Winter Spring/Autumn Summer
For heating
Air-conditioning
Display cooler and freezers
Ice-cream, Fryer, etc.
Single-Phase AC(200V)
1 6 11 16 21 26 31
Average Temperature ℃/ day
Fig. 5. Schematic power consumption in CVS.
Three-phase AC (200V)
Fig. 7 shows both fitted curve of individual stores and
features of equipment which are installation date and
performance. The latest equipment in store J shows low
power consumption. As the equipment gets older in store D,
F & G, curves shift direction to larger values without store H.
IV. SUMMARY
We have applied prototypes of wireless sensor nodes and
network system to monitoring the power consumption of
equipment in convenience stores as one of the important
applications for commercial power monitoring. The
prototype of sensor node is a wireless current clamp-on type
probes integrated with a thermometer and the system enables
simultaneous monitoring of 50 power lines. Using the sensor
nodes and system, power consumption monitoring of 10
convenience stores has been successfully demonstrated. It
has been found that for this application, besides the low cost
of sensor systems, ease of installation and undisturbed
environment in setting monitoring system were strongly
required. For achieving these properties and the low cost of
sensor systems, it would be necessary to have wireless and
non-battery system, small size sensor nodes.
ACKNOWLEDGMENT
The authors thank Seven-Eleven Japan Co., Ltd. for the
assistance of the power monitoring experiment in the stores.
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