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The energy invested in photovoltaic modules has been investigated on the basis of currently operating commercial production lines in France. The analysis was made for two types of solar cells, polycrystalline silicon and amorphous silicon. The energy which was calculated in this way was compared with the energy produced by these modules under operating conditions in various European climates. An average energy pay-back time of 1.2 years for amorphous silicon modules and 2.1 years for crystalline silicon modules was found. It can be anticipated that these energy pay-back times will decrease in the future.
Palz et al. (Tue,) studied this question.