Energy payback time

Finally, as with any new product, dedicated recycling processes need to be developed, both for recycling during production and for end-of-life recycling. Although the energy payback time is already favorable, a further reduction to less than 6 months is possible. 

The energy intensity of the processes contributes to the energy payback time of modules. Current silicon feedstock production is energy intensive, around ISOkWhkg . Together with the low silicon utilization, this leads to a module energy payback time between 1.5 and 4 years, which, although much shorter than the module lifetime, needs to decrease. 

The primary energy payback time is 3.1 years, and the GHG emissions payback time is 3.1 years. With a thirty year life cycle for all system components and the replacement of gasoline ICE vehicles with H2 FCVs, the payback time estimates translate into vehicle operation with 27 years of fossil fuel free energy use and zero GHG emissions. The sensitivity results indicate that a + 25% change in all life cycle estimation parameters change the primary energy payback time by + 0.80 years and the GHG emissions payback time by + 0.81 years. 

V. Fthenakis and E. Alsema, Photovoltaic energy payback times, greenhouse gas emissions and external costs, Progress in Photovoltaics Research and Applications 14 275-280 (2006). 

In addition to the cost effectiveness of silicon ribbons, energy payback time (i.e. the time needed to produce the amount of energy that was consumed during the manufacturing of a solar system) is drastically reduced. In a recent life-cycle analysis of crystalline silicon wafer based PV systems, it was demonstrated that the energy pay-back times can be reduced by half (based on cut multi-crystalline wafers), by the use of RGS ribbons for systems in central Europe [97]. 

Nijs, J. Mertens, R. Van Overstraeten, R. Szluf-cik, J. Hukin, D. Frisson, L. Energy payback time of crystalline silicon solar modules. Adv. Solar Energy 1998, 11, 291-327. 

Today the energy payback time, defined as the time necessary for a silicon solar panel to generate the energy equivalent to that used to produce it, is 3-4 years. Panel lifetime is normally more than 20 years. 

KAT 97] Kato K., Murata A., Sakuta K., Energy payback time and life-cycle CO2 emission of residential PV power system with silicon PV module. Appendix B-8 of the Enviroiunental Aspects of PV Power Systems , Utrecht University, Utrecht, 1997. 

PV systems are often compared in terms of their energy payback time ... 

Some values of energy payback times for different PV technologies will be given in the following sections. 

The International Energy Agency (lEA) has estimated the energy payback time of c-Si PV modules, incorporated as a grid-connected, rooftop installation, as 1.5-2 years, based on 2006 figures for the cost of a 13-14% efficient c-Si-based system, irradiated at 1700 kWh m yr and a performance ratio (which accounts for losses in the system, due to... 

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