Off-grid Solar System Installed on Building Wall

2014/05/08 17:36
Kenji Kaneko, Nikkei BP CleanTech Institute

Obayashi Corp announced April 25, 2014, that it has developed the "Solar Power Generation Cladding System," external eaves equipped with solar cells, and installed it at its facility in Kiyose City, Tokyo.

The facility is the "Open Labo-2," a new laboratory at Obayashi Corp Technical Research Institute. The system includes solar cells and exterior curtain walls. It is an off-grid system that does not send electricity generated to a power grid inside the building and uses the electricity directly for powering external power-saving windows and window shades.

Obayashi employed a laminated glass-type crystalline silicon (Si) solar cell. Because the cell allows any combination of cells and can be dealt as laminated glass for buildings, it becomes possible to design the system in accordance with the design of the building. The system can be installed like eaves and does not obstruct views while blocking sunlight during a summer season.

The system stores electricity generated in a rechargeable battery while controlling it with a controller, converts it into alternating-current (AC) electricity with an inverter and directly uses it for driving the motors of power-saving windows, window shades, etc.

Because the system is an off-grid type, it can also be used for business continuity plans (BCPs) (e.g. powering lighting equipment and charging mobile phones). An off-grid system whose capacity is less than a certain level does not require prior consultation with a power company, etc and is not regulated by law. Therefore, it is relatively easy to install such a system.

In general, solar power generation is susceptible to weather conditions and, thus, unstable. So, when a solar power generation facility is connected to a grid to sell electricity, prior consultation with a power company is required, and the facility stops operation in case of power outage, making it impossible to function as an emergency power source.

Moreover, though there are demands to install solar cells not only on roofs but on exterior walls of buildings, the introduction cost of cells becomes very high in consideration of design and their power generation efficiencies become low. As a result, when solar cells on external walls are connected to a power grid, it is difficult to ensure sufficient effects. The Solar Power Generation Cladding System was developed to address such issues.