Research and Development of Autonomous Distributed Power
System and Contribution to Regional Decarbonization

Kotaro Jinushi＊1

OES Project, Planetary Navigation GroupSony Computer Science Laboratories, Inc.

1. Introduction

At Sony Computer Science Laboratories (Sony CSL), we arepromoting the introduction of renewable energy through researchand development of the Open Energy System™ (OES)—namely,
a concept that will form the basis of distributed power systems
using distributed renewable energy and change the nature ofsociety. The contents of this research and development, examplesof demonstration experiments, and future developments aredescribed hereafter.

2．Background of the need for distributed
power systems

As reaffirmed in the Sixth Assessment Report of theIntergovernmental Panel on Climate Change (IPCC), which is
the intergovernmental organization that collects and organizes
scientific studies on global warming, climate change is being
driven by global warming[1]. Countries are also increasingly
moving to counter carbon-dioxide emissions, which are closelyrelated to global warming.
Japan can be taken as an example country. In October 2020,
Japan’s Prime Minister Suga announced the policy goal of
reducing emissions of greenhouse gases such as carbon dioxide
to virtually zero (so-called “carbon neutrality”) by 2050. To
achieve this goal, the energy-conversion sector (primarily powergeneration by power plants)[2], which emits the largest amountof carbon dioxide by sector, must be decarbonized; that is, powergeneration must stop depending on burning carbon-dioxideemitting coal, natural gas, etc. In fact, the Sixth Strategic Energy
Plan approved by the Japanese Cabinet in October 2021 clearlystates that renewable energy must be introduced to the maximum
possible extent.
As pointed out in the Net Zero 2050 report [3] of theInternational Energy Agency (IEA), which makes policy
recommendations on energy issues in general, to achieve
decarbonization by 2050, it will be necessary to (i) shift fromconventional fossil fuels (which emit CO2) to renewable-energy
sources such as solar and wind power and (ii) make maximum useof those sources. These renewable-energy sources are also called“variable renewable energy” in a way that indicates the amountof electricity generated by them fluctuates with variable weather

Daisuke Kawamoto＊2

OES Project, Planetary Navigation GroupSony Computer Science Laboratories, Inc.

and other factors. As for electricity systems, it is essential that
supply (generation) and demand (consumption) always match. It
is therefore necessary to be able to balance the fluctuating amountof electricity generated by renewable-energy sources with demand.
As one renewable-energy source, solar-power generation
benefits from ease of introduction, so it will be installed in variousplaces. In conjunction with this trend, the nature of electricitytransmission networks will also change. Conventionally, largescale power plants were built far from the power-consumption
areas. From the power plants, electricity only flowed one-way via
transmission lines toward the consumption areas. As stated in theSixth Strategic Energy Plan, since fewer suitable sites are available
for construction of large-scale solar power plants, it is necessary to
install solar-power-generation facilities on the roofs of houses, on
idle land in municipalities, and in various other locations where
solar power has not been introduced before. As a result, power willflow “in” from the extremities of the power network in a mannerthat was not previously anticipated. Dealing with this new trend
will also be a challenge.

3．Our approach

As for transitioning the electricity system to generation fromrenewable-energy sources and promoting decarbonization, twoissues must be addressed: (i) coordinating the ability to balance
supply and demand and (ii) managing the new electricity network.
Sony CSL has focused on “microgrids” as a mechanism forutilizing distributed renewable energy. A microgrid is a distributed
power system that enables control of the balance between demandand consumption in a small, regional (community size) basis,stable operation of the electricity system, and connection withexisting power systems. A microgrid is a distributed power systemthat generates, stores, and distributes the electricity consumed
within a certain area while being able to adjust locally. OES isa concept centered on a distributed power system that utilizes
this microgrid mechanism to maximize the use of renewableenergy and achieves regional energy circulation. As for the coretechnology of OES, we have developed the “autonomous powerinterchange system” (APIS), which is a control technology that
establishes a microgrid by autonomously matching supply anddemand on a one-to-one (peer-to-peer) basis and flexibly adapting＊1 Kotaro Jinushi’s affiliation is as of January 2023.
＊2 Daisuke Kawamoto’s affiliation is as of January 2023.

New Breeze Spring 202411the power supply by utilizing storage batteries connected by DC
private lines.

4．Our technology

As explained below, APIS consists of two technologies: (1)physical peer-to-peer power interchange and (2) autonomous
distributed cooperative control.
(1) Physical-peer-to-peer (PP2P) power interchange
A feature of this technology is that power is interchanged
between storage batteries by using constant-current control toadjust the power balance between the storage batteries. In thecase of conventional power interchange using voltage control, it isdifficult to achieve quantitative power interchange within a single
power network. Constant-current control enables PP2P powerinterchange through flexible battery combinations such as manyto-many, one-to-many, and many-to-one, so it becomes possible
to adjust the balance between demand and supply. PP2P powerinterchange between five storage batteries in a DC power network
is shown schematically in Figure 1.
■ Figure 1: PP2P power interchange(2) Autonomous distributed cooperative control
As for APIS, each storage battery is controlled by softwarewith the same functions. The software transfers power according
to the trading conditions set for the storage batteries, i.e., target
SoC (state of charge) for each time period, amount of electricity
to be interchanged, electricity prices, etc. (hereafter, simply“conditions”). Each storage battery periodically compares its“conditions” with the target SoC and offers to interchange power
flexibly with the other storage batteries. The battery receiving theoffer checks its SoC and other conditions and decides whether toaccept the proposal. If it accepts the offer, a deal will be concluded,and power will be interchanged (Figure 2). This conditions foreach storage battery can be set in units of time. The conditions canbe changed all at once from the server side. While each storage
battery can autonomously perform power interchange, it is also
possible to control power interchange from the APIS controlcenter side.
Combining these two technologies has the following twobenefits.

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Effective use of renewable energy: By exchanging power
between storage batteries, it is possible to adjust the supply-anddemand balance of renewable energy (the amount of which isgenerated is expected to fluctuate) and use it effectively.
Regional circulation of energy: Controlling the charging anddischarging of individual storage batteries by using APIS makes
it possible to collect surplus electricity within a certain region
at specific facilities. It will also be possible to transfer surplus
electricity to the large batteries of EVs and transport it to the placethat it is needed in a manner that achieves “energy circulation”
within the region.
■ Figure 2: Autonomous distributed control of household
power supply by APIS

5．Example demonstration of OES
We first tested APIS at 19 residences for teachers on thecampus of the Okinawa Institute of Science and Technology
Graduate University (OIST). Solar panels and storage batteries
equipped with APIS were installed at each residence and operatedfrom December 2014 to March 2020. (This demonstration
experiment was selected as Okinawa Prefecture’s “SubtropicalIsland-type Energy Basic Technology Research Subsidy Project”
and was conducted as a joint venture with OIST, OkisokouCo., Ltd., and Sony Business Operations Corporation). This
experiment demonstrated that a new distributed power system
can be constructed in parallel with the conventional powersystem, operate stably, and consume more renewable energy thansimply installing solar panels and storage batteries at each home
(Figure 3).
■ Figure 3: Effects of power interchange in Okinawa
Self sufficiency rate

Jan. Feb. Mar. Apr. May June July Aug.

Simulation from OIST’s actual data (from 2015)

APIS can be constructed relatively easily by connecting eachstorage battery with a private DC line. However, installing new
private DC lines faces issues such as high installation cost, which
limits the locations where they can be installed. With that issue
in mind, we are expanding and demonstrating APIS to enable
power interchange similar to that described above by utilizing AC
distribution lines that are already installed.
The location of the expanded demonstration of APIS isUmaba School Cottage, a “workcation” facility in Shiraji Umaba,
Ikeda-cho, Miyoshi City, Tokushima Prefecture (Figure 4). Since
October 2021, a power-interchange demonstration experimentusing storage batteries (Figure 5) connected to the AC wiringof this building has been conducted in collaboration with theConsortium for the Creation of Environmentally FriendlyWorkation Models, a consortium of industry, government, and■ Figure 4: Umaba School Cottage and solar-power
generation■ Figure 5: Installed storage batteries(Murata Manufacturing Co., Ltd.)

academia.
At the same time, we are verifying the charging anddischarging of fixed amounts of electricity from EV storage
batteries via CHAdeMO using ECONET-Lite. In 2023, abattery-storage system and expanded APIS were installed atother facilities in the city. We plan to implement two-way powerinterchange between multiple points (i.e., those facilities) by using
an actual power-distribution network and EVs.
We want to demonstrate that this battery-storage system andexpanded APIS can be used to effectively utilize renewable energy,
contribute to the decarbonization of the region, and promote
the circulation of energy within the region by supplying surplus
daytime solar power generated by households in the region tocommunity centers that consume electricity during the daytime.

6．Future developments

Our goal is to implement a new distributed power system,
mainly based on renewable energy, to promote decarbonizationand increase regional energy independence. To help achieve thisgoal, APIS was released on an open-source basis in December
2020 [4]. We hope that this open-source release will promote
open innovation and that we can introduce APIS widely. We arealso thinking about redefining APIS for matching surpluses andshortages of various goods and expanding it into a system thatcombines excess and shortages in the flow of goods and people
within a certain area in a way that makes efficient use of them.
For example, when EVs are recharged in areas with electricity
surpluses and transported to places with electricity deficiencies,
people can be transported in those EVs, thereby contributing tosecondary transportation in those areas. We are also considering
combining APIS with smart agriculture. When the timing andquantity of agricultural crops to be harvested are estimated, if asurplus of agricultural produce is estimated, it can matched withthe demand of organizations within the region and supplied tothem. We believe it is possible to expand APIS to such an intraregional distribution system. Pursing these kind of distributed
systems that are not limited to electricity, and their social
implementation, cannot be achieved by Sony CSL alone. We
therefore strongly desire to promote APIS while co-creating itwith various organizations.
(This is a translation of the January 2023 issue of the ITU Journal)
References[1] IPCC Sixth Assessment Report First Working Group Report,
https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf[2] J CCCA 4-04 Carbon-dioxide Emissions by Sector in Japan (2020), https://www.jccca.org/
download/65477?parent=chart&p_page=3#search (viewed 2022/11/17)[3] IEA Net Zero by 2050 https://www.iea.org/reports/net-zero-by-2050[4] Sony CSL APIS https://github.com/SonyCSL/APIS

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