This chapter presents the necessity for developing high performance, low-cost, and highly reliable solar cells in order to further deployment of photovoltaics, as well as the prospects and strategies for developing advanced solar cells.
Top1. Importance Of Solar Photovoltaics
As described in chapter 1, solar energy, including solar Photovoltaics (PV), is the only renewable energy resource that has enough terrestrial energy potential to satisfy a 20 TW or more carbon-free supply, because from the 1.2x105 TW (the solar constant is 1.76x105 TW) of solar energy that strikes the Earth’s surface, a practical sitting-constrained terrestrial global solar power potential value is about 600 TW, and thus, for a 10% efficient solar farm, at least 60 TW of power could be supplied from terrestrial solar energy resources (Lewis, 2005). According to the World Energy Vision 2100 recommended by WBGU (German Advisory Council on Global Change) (WBGU, 2003), as shown in Figure 1, solar electricity, including PV, is expected to become a major energy source with about 20% of the market in 2050 and about 70% in 2100. That means PV will play an important role to contributing to solving global environmental problems.
Figure 1. Transforming the global energy mix: primary energy supply until 2050/2010 (WBGU, 2003)
On March 11, 2011, heavy earthquakes and a tsunami struck the northeast region of Japan, damaging the Fukushima nuclear power plant No. 1, which now emits higher levels of radiation. Figure 2 shows changes in radiation levels in the northeast and Tokyo areas via distance from the Fukushima nuclear power plant reactor. Figure 3 shows changes in radiation levels in northeast of Japan and Tokyo areas via time (days) since March 15, 2011.
Figure 2. Changes in radiation levels in northeast and Tokyo areas via distance from the Fukushima nuclear power plant reactor
Figure 3. Changes in radiation levels in northeast areas via time (days) since March 15, 2011.
From Figures 2 and 3 we see that people must to live 30 km away from the center of the nuclear power plant in order to be safe from severe radiation exposure. Currently in Japan, 54 nuclear power plants are in operation and an additional 14 plants are planned. However, if almost all the nuclear power generating plants in Japan are heavily damaged in a similar way, it is presumed that possible living areas in Japan are reduced into 1/2 – 2/3 of the country, as shown in Figure 4.
Figure 4. Dark circles show areas with projected severe radiation levels; white circles show planned nuclear power plants
Therefore, further installation of nuclear power plants in Japan will be quite difficult, and further deployment of clean renewable energies, such as solar photovoltaics, will be necessary in order to create a low carbon society.
In order to overcome clean energy supply problems due to possible nuclear power plant crises, further deployment of PV power generating systems as well as further development in science and technology of PV are very important. Very large scale installation of PV power generating systems and further improvements in conversion efficiencies and reliability and lowering the cost of solar cells and modules are necessary.
This chapter presents prospects and strategies for developing advanced solar cells that are highly efficient, lower cost, and highly reliable.