Re-assessment of net energy production and greenhouse gas emissions avoidance after 40 years

[mblakele]

Reading a popular summary motivated me to dig up the original: Re-assessment of net energy production and greenhouse gas emissions avoidance after 40 years of photovoltaics development : Nature Communications

Abstract: Since the 1970s, installed solar photovoltaic capacity has grown tremendously to 230 gigawatt worldwide in 2015, with a growth rate between 1975 and 2015 of 45%. This rapid growth has led to concerns regarding the energy consumption and greenhouse gas emissions of photovoltaics production. We present a review of 40 years of photovoltaics development, analysing the development of energy demand and greenhouse gas emissions associated with photovoltaics production. Here we show strong downward trends of environmental impact of photovoltaics production, following the experience curve law. For every doubling of installed photovoltaic capacity, energy use decreases by 13 and 12% and greenhouse gas footprints by 17 and 24%, for poly- and monocrystalline based photovoltaic systems, respectively. As a result, we show a break-even between the cumulative disadvantages and benefits of photovoltaics, for both energy use and greenhouse gas emissions, occurs between 1997 and 2018, depending on photovoltaic performance and model uncertainties.

Similar studies have been published before, but this one uses the most recent data and its methodology seems solid.

 

[nwdiver]

'Well-2-Wheels' calculations are always the most fraught with assumptions that cannot be known and estimates that are widely generalized. Aluminum is a great example. There's easily 1000 lbs of aluminum in a 8kW PV array with the racking and frames of the panels. You need 8MWh of electricity to produce that much aluminum and that's not taking into account other transport costs. BUT... recycling Aluminum consumes ~95% less energy than producing raw.

Even if you're not using recycled aluminum as the source... what are the odds that aluminum won't get recycled at the end of life? Which numbers should be used in the well-2-wheels calc? There's no simple answer.