A life cycle assessment of various photovoltaic cells (PVs), which revealed that polycrystalline silicon PVs have great potential for CO2 reduction at the current development stage, was performed. The effect of PVs on CO2 reduction was calculated to be greater than that of forests. To estimate the global temperature, an N-layer atmospheric model was used, and the energy radiation and absorption by the atmosphere were calculated. An accurate estimation was achieved with 8 layers of the atmosphere. This model was applied to estimate the effect of the increase in temperature due to the accumulation of energy on the Earth by PVs, and the effect of PVs on global warming was determined to be negligible. A strong correlation between the CO2 concentration and temperature increase was confirmed. Thus, CO2 reduction via PV installation seems to be an appropriate strategy against global warming. A new method for establishing a PV installation strategy was proposed, and a case study was conducted in Kyoto city. The findings revealed that no deforestation was required to meet the estimated power demand but that only installation on the existing artificial structure could meet it.
Muranaka et al. (Fri,) studied this question.