DC-Based Open Energy System
A Sustainable, Dependable, and Affordable Solution
for Next-Generation Electrical Power Infrastructures

Mario Tokoro
Sony Computer Science Laboratories, Inc.
©2015 Sony Computer Science Laboratories, Inc.

PowerServer

PowerPacket

PowerServerClient

DC Bus Line
ClientClientTable-top Experiments, 2005©2015 Sony Computer Science Laboratories, Inc.

in Sony CSL

Ghana Expedition, 2010©2015 Sony Computer Science Laboratories, Inc.

Supported by JICA

Okinawa, 2012©2015 Sony Computer Science Laboratories, Inc.

Sony CSL - OIST Joint projectBangladesh, 2014©2015 Sony Computer Science Laboratories, Inc.

Supported by MOE, Japan

Okinawa, since Dec. 2014©2015 Sony Computer Science Laboratories, Inc.

Supported by Okinawa Prefecture Government

Our Fundamental Thought
Sustainable Do not pass on liability to next generation
Dependable Keep risk manageable
Affordable

Accessible to everyone on earth©2015 Sony Computer Science Laboratories, Inc.

Conventional Power Systems©2015 Sony Computer Science Laboratories, Inc.

Our Approach
Sustainable

Renewable Energy Sources, which areDistributed,Unstable,
withDo not pass Intermittent,
on liability toandnextgeneration
Batteries

Local Consumption of the Locally Produced
Self-Supporting
as much, in the form ofKeeprisk manageable
Dependable byBottom-Up, Autonomous, and Interconnected

Affordable

System can start Small yet Expandable in theAccessible
formof Bottom-Up,
to everyone
Autonomous,on earth andInterconnected©2015 Sony Computer Science Laboratories, Inc.

Open Energy Systems©2015 Sony Computer Science Laboratories, Inc.

Conventional systems

Open Energy Systems• Centralized energy source• Transmission for distantconsumption• Top-down configuration withcentral control• Flow based, synchronous
load/supply balancing• Distribution network• Distributed energy sources• Local consumption of the locallyproduced• Bottom-up and flexible configurationof distributed autonomous systems• Stock based, asynchronous
load/supply balancing• Exchange network©2015 Sony Computer Science Laboratories, Inc.

How do we achieve OES?
DCOES Technologies©2015 Sony Computer Science Laboratories, Inc.

Renewable Energy Sources

http://commons.wikimedia.org/wiki/File:Machikawa_power_station_1.jpg#/media/File:Machikawa_power_station_1.jpg©2015 Sony Computer Science Laboratories, Inc.

©OISTBatteries / Energy Storage©2015 Sony Computer Science Laboratories, Inc.

SONY Ferro-Phosphoric Acid Li-Ion Batteries• Full use of capacity• Long life under tough conditions• Inherent safety:no thermal runaway• Fast Charging time:
1 hour for >90% capacity• Eco-friendly:
no rare metals©2015 Sony Computer Science Laboratories, Inc.

SONY Ferro-Phosphoric Acid Li-Ion Batteries©2015 Sony Computer Science Laboratories, Inc.

How to balance the PV generation
and battery capacity?

©2015 Sony Computer Science Laboratories, Inc.

Batteries cannot take whole energy produced by PV©2015 Sony Computer Science Laboratories, Inc.

Variety in usage pattern

Image ©2014 DigitalGlobe, Map data © 2014 Google, ZENRIN©2015 Sony Computer Science Laboratories, Inc.

Energy Exchange Technology
Exchange energy among batteries
In the form of DC
In order to maximize the use of PV panels andbatteries
through complementing difference in usage
patterns©2015 Sony Computer Science Laboratories, Inc.

ACfor transformers• Reactance loss of power isnot negligible• Interconnection ofnetworks is difficult due tosync.
Frequency

DCfor batteries• Efficient DC/DC converters
are now available• Interconnection ofnetworks is easy (no sync.
is necessary)

Phase
Voltage©2015 Sony Computer Science Laboratories, Inc.

VoltageBase Theory

Constant Voltage Source keeps
the grid voltage at 350V

Constant Current Sources
set desired current

One Voltage Source and n Current Sources
with Durable and Flexible Distributed Control©2015 Sony Computer Science Laboratories, Inc.

m-to-n Energy Exchange#0
DC/DCCV

VG=350V

#1
DC/DC

CC

#2
DC/DC

CC

#3
DC/DC

#4
DC/DC

CC

#5
DC/DC

CC

CC

IG=2A

IG=2A

IG=2A

IG=4A

IG=2A

2A

2A

2A

4A

2A
350V Bus line

2A
Set the Grid to 350V by CV mode (#0)
Deal 1: Send energy from #1 -> #3
Deal 2: Send energy from #4 -> #2, #5©2015 Sony Computer Science Laboratories, Inc.

2A

2A

DC/DC converter can have 3modes:• Waiting (stop)• Constant Voltage mode (CV)• Constant Current mode (CC)Energy Exchange Policies• Baseline policy– Capacity available for giving/receiving– Request for consumption• Advanced policies– Prediction based on past usage pattern– Weather forecast for generation and consumption– Dynamic pricing reflecting demand and supply©2015 Sony Computer Science Laboratories, Inc.

Power Exchange Network
Scalable Architecture
When necessary

When necessary

Most exchanges happen at the lowest level!
©2015 Sony Computer Science Laboratories, Inc.

©2015 Sony Computer Science Laboratories, Inc.

DCOES@OIST20 System Structure (1)• Configuration of each house

PVChargerBattery48VDC

EnergySystemController
Bi-directional
DC/DCInverterand ACswitch

100VAC©2015 Sony Computer Science Laboratories, Inc.

Energy ServerSystem350VDC

DCOES@OIST20 System Structure (2)• 19 houses connectedhouse 1house 2house 19...
350VDCPower LineswitchswitchswitchswitchCommunication Line
©2015 Sony Computer Science Laboratories, Inc.

switchswitchswitchswitchswitchEnergy Server System• SONY 48V Li-Ion battery modules• 350V Grid
• Energy exchange module, DCDC
• DC to AC inverter for appliances• AC backup by utility company

EMU
Main Controller
PV Charger
PV Charger
BMU
Battery 1.2kWh
Battery 1.2kWh
Battery 1.2kWh
Battery 1.2kWh
DC-DC Conv.
Inverter©2015 Sony Computer Science Laboratories, Inc.

350V DC Power Lines (Privately Owned)©2015 Sony Computer Science Laboratories, Inc.

Example Daily Operation©2015 Sony CSLPerformance Evaluation©2015 Sony Computer Science Laboratories, Inc.

Performance Evaluation
Distributed stand-alone

Centralizedvs

Bottom-up by individuals• Flexible in size and variety withincremental costs• Failures do not cause total systemoutage• May not be efficient overall©2015 Sony Computer Science Laboratories, Inc.

Top-down by a single entity• Fixed in size with high initial costs• Single failure may cause total systemoutage• Efficient for a predefined users andusage patterns

DCOES: Distributed System with Energy Exchange

DCOES• Flexible in size and variety
with incremental costs• Failures do not cause total
system outages©2015 Sony Computer Science Laboratories, Inc.

• High efficiency and flexibility
in size and variety

Variety in usage pattern (Winter)

Q3
MedianQ1xoutlier©2015 Sony Computer Science Laboratories, Inc.

Variety in usage pattern (Spring)

Q3MedianQ1xoutlier©2015 Sony Computer Science Laboratories, Inc.

Performance Result and Estimation(Current OIST configuration with baseline policy)
Winter: Real OIST Data (19 houses) Spring: Real OIST Data (19 houses) Summer: Simulation (19 houses)
2015/1/1- 1/31
2015/4/16- 5/16
2015/7/16- 8/15

100%
80%
60%

60%
40%

34%

38%

42%

67%

74%

63%

71%

77%

Stand Alone
DCOES
Centralized

20%0%StandWinteraloneSpring
DCOES Summer Centralized

Self-sufficiency ratio = (Energy used - Energy bought)/ Energy used©2015 Sony Computer Science Laboratories, Inc.

Performance Result and Estimation(Solar x2, Battery x2 with baseline policy)
Winter: Real OIST Data (19 houses) Spring: Real OIST Data (19 houses) Summer: Simulation (19 houses)
2015/1/1- 1/31
2015/4/16- 5/16
2015/7/16- 8/15

100%

87%

80%
60%

67%

94% 96%90%

96% 99%73%

57%

Stand Alone
DCOES

40%

Centralized

20%0%WinterSpringSummer

Self-sufficiency ratio = (Energy used - Energy bought)/ Energy used©2015 Sony Computer Science Laboratories, Inc.

Next Plans©2015 Sony Computer Science Laboratories, Inc.

DCOES/LV for Houses in a Community

350V DC Line
PV: 3-5kWp
Batt.: 5kWh©2015 Sony Computer Science Laboratories, Inc.

DCOES/MV for Larger Communities

DCOES/LV

DCOES/LV

DCOES/LV

DCOES/LV

DCOES/LV

DCOES/MV
DCOES/LV©2015 Sony Computer Science Laboratories, Inc.

DCOES/LV

DCOES/
LV

350V DC Line
PV: 3-5kWp
Batt.: 5kWh + 1KV LineDCOES/MV for Eco Campuses

1KV DC Line
PV: 100kWp
Batt.: 500kWh©2015 Sony Computer Science Laboratories, Inc.

DCOES/HV for Cities

DCOES

DC based Open Energy System
For sustainable mankindand development©2015 Sony Computer Science Laboratories, Inc.

Acknowledgements
Sony Computer Science Laboratories, Inc.

H. Kitano, Y. Tokuda, S. Tajima, T. Yoshimura, Y. Ishibashi, T. Morita,
A. Werth, D. Kawamoto, D. Yanagidaira, N. Matsuda, A. André

Okinawa Institute for Science and Technology

T. Sakagami, K. Kuwae, M. Nishimura, H. Kitano, J. Dickison

Okisokou Co. Ltd

K. Nishime, Y. Toma, H. Yoshida, Y. Ohshiro, Y. Higa, T. Nagata

Sony Energy Devices Corporation
Sony Business Operations
Sony Corporation
JICA (Japan International Cooperation Agency)
MOE (Ministry of the Environment), Japan
Okinawa Prefecture Government, Japan©2015 Sony Computer Science Laboratories, Inc.