Mitsubishi Electric Opens Its 2nd PV Cell Production Facility

Mitsubishi Electric Corporation has completed construction of PV Cell Plant #2, a new photovoltaic (PV) cell production facility at its Nakatsugawa Works Iida Factory in Nagano Prefecture. By March 2011, the company will raise its annual PV cell/module production capacity by 50 megawatts (MW) to 270MW, and ultimately plans to reach an annual capacity of 600MW at an early stage.

The global PV market is expected to grow from 5,550MW in fiscal 2009 (April 2008 – March 2009) to approximately 8,000MW in fiscal 2012 (April 2011 – March 2012), with the introduction of new PV-related stimulus programs in Japan, feed-in-tariff systems spreading in Europe, as well as projected growth in the North American market. Mitsubishi Electric‘s expansion of production capacity is in response to this sharp increase in global demand for PV systems.

Adding to its current lineup of polycrystalline silicon PV modules, Mitsubishi Electric plans to install new equipment at its Iida Factory to manufacture monocrystalline silicon PV cells, and start production by March 2011. At the same time, the company will build new production lines to manufacture monocrystalline silicon PV modules at its Nakatsugawa Works Kyoto Factory in Kyoto Prefecture. Monocrystaline silicon PV modules will enable PV systems to generate relatively more electricity on limited surfaces compared to polycrystalline silicon PV modules.
Furthermore, using the technologies that enabled Mitsubishi Electric to achieve the world’s highest photoelectric conversion efficiency of 19.3% in a 150mm x 150mm polycrystalline silicon PV cell, the company plans to develop highly efficient monocrystalline silicon PV cells. Mitsubishi Electric intends to incorporate these PV cells in its future PV modules.

In addition, to respond mainly to the large increase in demand for PV inverters for residential-use in the 2/3
Japanese market, Mitsubishi Electric will raise its monthly PV inverter production capacity at its Nakatsugawa Works by 50% from 4,000 units to 6,000 units in May 2010.

global.mitsubishielectric.com

Mitsubishi Sets New Bar For Efficiency of PV Cells

Mitsubishi Electric Corporation announced it has set two world records for photoelectric conversion efficiency in polycrystalline silicon photovoltaic (PV) cells, achieved by reducing resistive loss in the cells. Photoelectric conversion efficiency is the rate at which sunlight energy is converted into electricity, with higher rates meaning more output.

In response to the growing demand for PV systems that help tackle global warming, the global production of PV cells has reached 5,500 megawatts (MW) in the fiscal year ending March 2009 (FY2009), and is expected to reach 8,000 MW in FY2012. With the use of crystalline silicon PV cells continuing to increase, PV cell manufacturers are looking for ways to improve the conversion efficiency of these cells to gain more output power from limited surfaces. At the same time, PV cell manufacturers are trying to achieve more output power while reducing the thickness of PV cells, thereby reducing their dependence on silicon and the related risk of sharply fluctuating prices for this material.

One of the world records is a 19.3-percent efficiency rating for photoelectric conversion of a practically-sized polycrystalline silicon PV cell of 100 squared centimeters or larger, with the PV cell measuring approximately 15 cm x 15 cm x 200 micrometers. The rating is 0.2 points higher than the company’s previous record of 19.1 percent.

The second world record, achieved with the same technologies in an ultra-thin polycrystalline silicon PV cell measuring approximately 15 cm x 15 cm x 100 micrometers, is an efficiency rating of 18.1 percent, a 0.7-point improvement over the company’s previous record of 17.4 percent.

The conversion efficiency rates have been confirmed by the National Institute of Advanced Industrial Science and Technology (AIST), in Japan.

Mitsubishi Electric will be developing mass-production technology to deliver these high conversion rates in commercial PV modules. The company also aims to increase the output of its PV systems by combining this technology with PV inverters capable of high-efficiency conversion of DC current to AC. By improving the efficiency of its PV systems, Mitsubishi Electric expects to contribute to environmental preservation as well as sustainable societies.

Background

Previously, Mitsubishi Electric, with support from the New Energy and Industrial Technology Development Organization (NEDO) under the Ministry of Economy, Trade and Industry (METI), improved the conversion efficiency of its PV cells by developing a low-reflection, honeycomb-textured surface that reduces sunlight loss due to reflection. In 2008, the company achieved a world-record photoelectric conversion efficiency rating of 17.4% with an ultra-thin polycrystalline silicon PV cell measuring about 15 cm x 15 cm x 100 micrometers.

Mitsubishi Electric also developed a reflective structure for the rear surfaces of PV cells to capture infrared rays that otherwise would pass through the cells and thus not be harnessed to generate electricity. Using these technologies, in 2009 Mitsubishi Electric achieved another world-record of 19.1 percent with a polycrystalline silicon PV cell measuring approximately 15 cm x 15 cm x 200 micrometers.

To further improve these photoelectric conversion efficiencies, however, the company decided to develop a new technology to reduce resistive loss.

Main Developments

1. 19.3% efficiency in polycrystalline silicon PV cell (15 cm x 15 cm x 200 micrometers).  A certain amount of electricity generated in PV cells is dissipated as heat due to resistive loss between silicon wafers and electrodes, so reducing the contact resistance at electrodes can improve conversion efficiency. Mitsubishi Electric’s new technology applies a treatment to the wafer prior to electrode formation to improve electrical contact performance, thereby reducing resistive loss by 4 percent compared to previous PV cells. The 0.2-point improvement over the previous record of 19.1% enables the electrical output in a cell of practical measurements to increase by approximately 1%, from 4.16W to 4.2W.
2. 18.1% efficiency in ultra-thin polycrystalline silicon substrate (15 cm x 15 cm x 100 micrometers)
   By applying the above-mentioned technologies in a practical-size, ultra-thin polycrystalline silicon wafer measuring approximately 15 cm x 15 cm x 100 micrometers, Mitsubishi Electric improved photoelectric  conversion by 0.7 points to 18.1%.

www.mitsubishielectric.com