MHI has developed an amorphous-silicon (a-Si) / microcrystalline-Si (µc-Si) tandem photovoltaic (PV) module production technology that achieves 50% higher maximum power output(150 watts per module) than the company's conventional a-Si PV modules that it now produces.

MHI plan is to construct a commercial production plant for the new thin-film PV modules on the premises of its Nagasaki Shipyard and Machinery Works' Isahaya Plant where the company's a-Si PV module production base is located. The new plant will have a capacity of approximately 270,000 modules a year, an amount equivalent to 40MW peak generation. Construction of the plant has commenced this February, with product shipments scheduled to begin in April 2007. (The investment sum is approximately 10 billion yen.)

In preparation for production of the new tandem-type PV modules, MHI and the New Energy and Industrial Technology Development Organization (NEDO) have been jointly developing the production technology since 2000. The tandem-type PV module is being viewed as the next-generation of thin-film PVs. The tandem PV modules consist of a a-Si PV layer and a µc-Si PV layer on top. The tandem PV can absorb a broader range of wavelengths of solar light (from UV to infrared) than the conventional a-Si PV, and thus achieves higher power conversion efficiency.

The keys to realizing both high efficiency and productivity with a-Si/µc-Si tandem-type PV modules lie in a) the light trapping technology for efficient utilization of solar light, and b) the technology for high-speed, high-quality µc-Si thin-film deposition. MHI has been working on these challenges leveraging its in-house capabilities in design and manufacturing of major production equipments, including plasma CVD (chemical vapor deposition), the core technology of the production process, and production know-how accumulated with a-Si PV modules. At its verification facility the company achieved the targeted power conversion efficiency and productivity on actual size modules (1.4 x 1.1 meter), leading to the decision to mass-produce the a-Si/µc-Si tandem PV modules.

Since PV systems do not emit carbon dioxide (CO2) on generating electricity, they are drawing much attention as one of the technologies to prevent global warming. In recent years, the solar cell world market has been expanding rapidly at roughly 30% annual rate. MHI launched industrial production of a-Si PV modules in 2002 and has sold the products worldwide, especially in Germany and other European markets. To meet expanding demand, the company has recently been producing at full capacity.

Another aspect of the thin film PV technology is, that it has, unlike crystalline Si PVs requiring polycrystalline or monocrystalline silicon material, which nowadays are short in supply, essentially no constraints on raw material side. There fore, the supply of PVs based on this technology is only limited by its production capacity and greatly contributes to stable cost and stable supplies of PVs.

To seize this best timing of demand growth and supply constraint on crystalline Si PVs for marketing the a-Si/µc-Si tandem PVs, MHI decided to build the new PV production plant. The total production capability of both a-Si PV factory and a-Si/µc-Si tandem-type PV factory will be 50MW, and MHI is targeting 15 billion yen in PV module sales in fiscal 2008.