The compact system, incorporates compound semiconductor CPV concentrator panels at an elevated position. They are claimed to offer 7.5 times greater output power than previous generations and are also thinner and lighter than conventional modules

Sumitomo Electric Industries, Ltd. (SEI) claims its new megawatt-class electric power generation/storage system consists of the world’s largest redox flow battery and Japan's largest concentrated photovoltaic (CPV) units.

The Company is currently constructing a facility to test the system at the Yokohama Works (Sakae-ku Yokohama), and plans to start the demonstration in July 2012.

With companies striving to meet strict energy supply conditions, demand for distributed power systems using renewable energy is expected to grow in the future. To respond to demand, SEI has been working on the research and development of technology for effective power conversion, control and generation as well as storage.

The Company began testing its micro smart-grid system at the Osaka Works last June.

In this setup, natural energy sources, including an in-house developed CPV system, and a small redox flow battery are DC-interconnected, and the energy management system (EMS) controls fluctuations in natural energy (excluding solar and wind power) and power consumption by relatively small electric loads. Again, the latter excludes lighting and home appliances.

As a result, SEI says the overall system enables the most reliable and efficient power control, particularly from general consumers' standpoint.

Recently, there has also been an increasing expectation for major energy consumers, such as plants and companies, to promote the use of renewable energy and energy saving measures. To accommodate this, SEI has developed a large-scale electric power generation/storage system consisting of a redox flow battery and CPV units. The system with megawatt-level capacity and output power will be tested on the premises of the Yokohama Works with the aim of accelerating the development and commercialisation of large power systems and related facilities.

The system consists of 28 III-V semiconductor CPV units with a maximum total power generation of 200 kW as energy sources and one redox flow battery. The battery has a capacity of 1 MW for 5 hours and acts as a storage facility of CPV-generated power and low-cost electricity provided by power companies during the night, while connected to external commercial power networks.

The EMS system aims to regulate the amount of electricity provided by power companies using the redox flow battery's charge/discharge control function. The system also aims to systematically use solar power using the battery to balance the fluctuations in CPV power generation that is susceptible to the weather.



Megawatt-Class Power Generation/Storage System　

The redox flow battery is a storage battery that comprises a charging/discharging cell section and a tank full of metal ion electrolyte. It charges and discharges through oxidation-reduction of vanadium or other ions.

The battery has a long service life as the electrodes and electrolyte are not subject to deterioration even after repeated charge and discharge operations. SEI says it is also easily maintained as it uses the same electrolyte in both the cathode and anode.

What's more, the battery is claimed to provide increased safety as it does not require any combustible substances and is operated at ambient temperatures. It is suitable for irregular, highly fluctuating charge/discharge operations, enabling accurate monitoring and control of stored electric power. Accordingly, it is an optimal storage battery for efficient use of renewable energy and surplus electricity supplied during the night.

The second part of the module is a CPV unit incorporating small-size photovoltaic cells for energy conversion, directing high-intensity sunlight converged by a lens to photovoltaic cells. The power generation efficiency of the CPV panel is claimed to be about twice that of silicon solar panels currently on the market as CPV cells are made from a special compound semiconductor material which SEI have remained tight-lipped about.

Installed at an elevated position, the concentrator panels provide usable space below them. The newly developed CPV unit offers 7.5 times greater output power (7.5 kW/unit), and yet the CPV panels are thinner and lighter than conventional ones.

The module comes with an energy management system (EMS), which monitors the amounts of electric power generated by the 28 CPV units, via commercial power networks which are stored in a redox flow battery, and consumed at an office or plant to manage the electric power flow. Obtained data is sent by optical communication networks to be collectively controlled at the central control server. This system will be used in the demonstration test held at the Yokohama to achieve optimal supply-demand balance (maximum demand control of 1 MW) and power demand control based on preset schedules.



Schematic and photo of  SEI Yokohama Works