The cumulative amount of clean electricity generated by solar panels over the past 40 years is soon to complete repaying the energy debt required to make the 230 gigawatts (GW) worth of solar currently installed around the world, according to a new study which addressed concerns of how much fossil fuel energy was being used to produce this new clean energy.
Cumulative installed solar photovoltaic (PV) capacity has grown from less than 1 megawatt (MW) in 1975, to finish 2015 with 230 GW worldwide — a growth rate of around 45%. As always, there were concerns raised, legitimately, regarding how much fossil fuel energy was being used to produce and transport this much solar energy, and the resulting greenhouse gas emissions from such manufacturing and transport.
Researchers from the Netherlands set out to solve this puzzle by analyzing the development of energy demand and greenhouse gas emissions associated with solar photovoltaic production. The authors relied on several different sources of data for their study, which was published in the journal Nature Communications:
- Historical data on the development of cumulative installed PV capacity (CIPC) including PV technology market shares
- PV cost data for the period under investigation
- Forecast of the development of CIPC and PV technology market shares
- Life-cycle assessment (LCA) results for PV for the period studied
The study analyzed monocrystalline and polycrystalline silicon based systems, and gathered results from a total of 40 life-cycle assessment studies conducted between 1976 and 2014. (The full study with complete methodology is free to read here.)
The results of the study showed that there “are strong downward trends for both energy demand and [greenhouse gas (GHG)] emission from PV production, and that these trends follow the experience curve law.” Specifically, the study concludes that for every doubling of installed solar PV capacity there is a resultant decrease in energy use of 13% and 12% (mono- and polycrystalline respectively), and resultant decrease of 17% and 24% in greenhouse gas footprint.
As such, and taking into account a worse-case solar PV performance scenario along with model uncertainties, the break even point for solar energy occurs in 2017 for net energy use, and in 2018 for greenhouse gas emissions avoidance. However, the authors note that it is likely both cumulative energy use and greenhouse gas emissions were already repaid back in 2011.
It is important to also note that the authors believe that, due to the rapid growth of the solar PV industry in recent years, the solar energy industry became a temporary net primary energy sink, as well as a temporary emitter of greenhouse gas emissions. This is due likely to the solar energy industry installing solar at such a pace that the energy it made could not quickly enough pay back the production debt. But as the solar industry matures and solar install rates level out, any temporary energy sink or greenhouse gas emissions will be quickly accounted for by the electricity generated.
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