Technical Library July 4, 2011

Technologies Contributing to Energy Reduction and Efficiency,
and Renewable Energy


1. Introduction

The Great East Japan Earthquake and accident at the Fukushima Dai-Ichi nuclear reactor dramatically changed Japan's electricity supply situation. People are questioning the safety of nuclear power and becoming increasingly interested in renewable energy. Both corporations and individuals are desperately searching for ways to overcome the power shortage that Japan now faces. Also, an increasing number of the nuclear power plants that were shut down for inspection following concerns about their safety are not being restarted. Therefore, electricity shortages that were previously confined to the disaster-stricken areas of northeast Japan and the Kanto area are now being experienced all across the country. This has further hastened the need to conserve energy, and find renewable energy sources.

Since Nichicon's management philosophy of contributing to a brighter future for society by creating valuable products while protecting the environment, on March 15, 2010, about a year before the Great East Japan Earthquake, the company inaugurated the Nichicon Energy Control System Technology (hereafter NECST) Project. Nichicon is already underway under the direct control of President and COO Sachihiko Araki with the NECST project which is aimed at achieving a stable supply of energy while protecting the environment. To achieve this, it will require that we decrease our dependency on fossils fuels and adopt more renewable energy. One form of renewable energy comes in the form of EVs, which are enjoying increasing popularity.

Mass-produced Electric Vehicles (hereafter EVs) currently being sold use an in-vehicle recharger made by Nichicon. Based on this recharger technology, Nichicon is working on a number of developments: rapid rechargers for battery charging infrastructure; systems combining solar power generation and charging equipment; charging equipment with lithium batteries; systems for peak load reduction. On this article are introduced a number of technologies and facilities: a photovoltaic power system with power storage bank for peak load reduction; a system for using wind power to reduce fluctuations in power generation; facilities for charging EVs using renewable energy and power storage technology.


2. Photovoltaic Power System with Power Storage Bank for Peak Load Reduction

This system combines solar power generation and storage functions to successfully reduce peak load.

In 2004, Nichicon developed a solar power generation system, which uses electric double-layer capacitors for the power storage bank, and combines electric double-layer capacitor technology and grid-connected power electronics technology. The system was installed on the roof of Nichicon's head office in Kyoto (photo 1). 2011 marks the system's seventh year of operation.

The system is made up of 10-kW solar panels, a DC-DC converter that contains a maximum electric power tracking control, a storage bank that stores the energy, and a power conditioner that sends the energy charged in the storage battery to the power grid (photo 2).

Thanks to this system, Nichicon received a subsidy from the New Energy and Industrial Technology Development Organization (hereafter NEDO) as a joint developer in the field testing of solar power generation and other new technologies for reducing peak load. Making use of this technology, Nichicon can comply with orders to reduce peak load during times of high electricity demand. When there is no need to reduce peak load, the electricity generated by solar power is output by the power conditioner to the grid; during peak load reducing times, the output from the solar panels, and the electricity in the power storage bank, are sent via the power conditioner as rated power to the grid.

Using electric double-layer capacitors for the power storage bank creates a system that offers long service life, a lead-free environment, and the ability to make use of stored electricity when demand is high. This system developed by Nichicon is still operating today. Nichicon will continue development on the system, combining it with lithium batteries to increase the peak load reduction, improving its compatibility with the grid, and making the energy generated more convenient to use. The result will be a system that can make up for electricity shortages and operate as a stand-alone system in case of emergencies.

Photo 1   Photo 2
Photo 1
Photovoltaic power system with power storage bank
  Photo 2
Converter and power storage bank

3. Wind Power Generation System with Power Storage Bank

Because the amount of power generated by wind is proportional to the cube of wind velocity, output fluctuates significantly. When a wind power generation system is connected to the power grid, factors like frequency fluctuation can hinder the operation of the grid.

To solve these problems, Nichicon is conducting verification experiments of a distributed energy system developed to ensure stable power to the grid through measures such as equipping the wind power generation system with a power storage unit that will help stabilize output.

This system is undergoing verification testing under a five-year plan in collaboration with Hokuriku Electric Power Company and other groups under a NEDO project titled Development of an Electric Energy Storage System for Grid-connection with New Energy Resources. The goal is to develop technology that will realize next-generation power storage systems. (Photos 3 and 4)

The storage unit of this system uses a lithium-ion battery. Through a battery management system, the battery cells are monitored and controlled in order to limit fluctuation in voltage and to give interconnected control with the power converter.

The power conversion section is equipped with futuristic functions needed to make it viable for use with renewable energy systems and smart grids: there are functions, for example, for maintaining the grid voltage, and for using electricity stored in the power storage bank to ensure operation can continue even if the voltage to the power grid suddenly drops.

Photo 3   Photo 4
Photo 3
Electric energy storage system for grid connection
  Photo 4
Hokuriku Electric's wind farm in Shiga, Ishikawa

4. Example of Combination of Solar Power Generator, Storage Battery, and Charger

This is an EV charging station that includes a storage function so that rapid recharging is possible even when using low-capacity power sources.

Rapid recharging systems use high-capacity power sources, which may require high voltages. In that event, expensive electrical and wiring installation is necessary. To solve the problem of how to enable rapid recharging when there is limited capacity from the alternating current (AC) system, Nichicon has developed a system combining solar power generation and a high-capacity storage battery. This system has been installed at the Suita Service Area on the Meishin Expressway (photo 5). With this system, electricity stored in the battery is used for rapid recharging-which is possible even when the capacity of the rapid recharger is only 6%. As well, still fresh in our minds is the Great East Japan Earthquake, which has resulted in gasoline and power shortages that have limited the movement of goods and services and people as well. With a system like the one installed at the Suita Service Area, solar power that is generated and stored can be used for off-grid systems that provide power in times of disaster and that make possible emergency-use rapid recharging. By installing this system in places such as freeway service areas, Nichicon can contribute to the promotion of renewable energy and help spread the use of EVs, which emit no CO2.

Photo 5
Photo 5
Energy-conserving and energy-storing rapid recharging system at the Suita Service Area

5. Conclusion

With the Great East Japan Earthquake and accident at the Fukushima Dai-Ichi nuclear reactor having created concern about a nationwide shortage of electricity, it is imperative that Japan finds ways to cut back on energy consumption, use energy more efficiently, and expand its use of renewable energy. Through developments such as a system for peak load reduction through a combination of renewable energy and power storage, and a rapid EV recharging system combining solar power and storage batteries, Nichicon has been conducting verification testing systems for helping in times of power shortages, providing power during emergencies, and promoting the spread of infrastructure for EVs. These developments have the potential to reduce CO2 emissions in a variety of applications, help accelerate the spread of EVs and EV infrastructure, and contribute to the realization a low-carbon, safe society.


Katsuhiko Furuya
NECST Project, Nichicon Corporation
From the Dempa Shimbun, July 4, 2011

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