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.
Cumulative installed solar photovoltaic (PV) capacity (CIPC) grew from less than 1 MWp in 1975 to around 180 GWp at the end of 2014 (refs 1, 2, 3), with a compound annual growth rate (CAGR) of 45%. As shown in Fig. 1, major installation markets at the beginning of the 1990s were Japan and Italy, but from 2005 to 2014 Germany was the leading PV market in terms of CIPC4. It is expected that China will surpass Germany as the country with the largest CIPC during 20155. The strong growth can largely be attributed to successful government support schemes, like Germany’s feed-in tariff, but also to rapidly falling prices of PV systems.
Figure 1: Historical PV market developments.
(a) Development of total Cumulative Installed PV Capacity (all PV technologies) from 1975–2014 with a CAGR of 45%; data taken from1,2,3,16,25,46, and expected development from 2015–2020 (CAGR: 18%1,). (b) Development of CIPC from 1992–2014 for 5 main markets; data taken from2,46. (c) Development of total capacity share from 1993–2014 for 5 main markets; data taken from2,46.
PV electricity has large social and governmental support, as during its operation no harmful emissions are released. Over the whole life-cycle of a PV system, it pays back the energy invested and greenhouse gas (GHG) emissions released during its production multiple times6,7,8,9. As PV systems operate over a period of up to 30 years, there is a significant time-lag between the investments, in terms of cumulative energy demand (CED) and GHG emissions, and the benefits obtained due to delivery of electricity and replacement of high-environmental impact electricity from fossil fuel sources. Coupling the rapid growth of PV with this context of upfront investments has led to some concerns, regarding the PV industry’s environmental sustainability. A fast growth of installed PV capacity could result in the creation of an energy sink, as the PV industry could embed energy in PV systems at a rate outpaced by these system’s ability to deliver it back. The same can be true for GHG emissions, when the production of PV systems releases more GHG emissions than the electricity produced with PV can offset by replacing more GHG intensive electricity. Although there is evidence that shows that CED and GHG emissions are correlated10, this is not necessarily the case.