Tho' starting with requisite praise and soothsaying, a paper questions the LCA of solar PV.

[NNadir]

The paper I'll discuss in this post is this one: Ignoring the Effects of Photovoltaic Array Deployment on Greenhouse Gas Emissions May Lead to Overestimation of the Contribution of Photovoltaic Power Generation to Greenhouse Gas Reduction Bin Zhang, Ruohui Zhang, You Li, Shiwen Wang, and Fu Xing Environmental Science & Technology 2023 57 (10), 4241-4252.

One cannot, these days, discuss solar PV energy in any terms than wild praise, although nearly 50 years of praise for it has obviously not done a damned thing to slow climate change, which is now here, worse than ever, and accelerating at the most rapid rate (2nd derivative) ever observed. Only an asteroid collision with Earth could go faster in terms of inducing rapid climate change from dangerous fossil fuel combustion; access to which is required for the solar industry to exist without exacerbating vast increases in human poverty.

We have spent trillions of dollars on solar energy in this century, and websites and literature all over the world sings its praises, and yet the most recent data we have on world energy production and consumption, the 2022 IEA World Energy Outlook, reports that solar energy produced just 5 Exajoules out of the 624 Exajoules consumed by humanity in 2021.

Yet the soothsaying about what solar could do, but never has done, continues, including the chant that solar energy is the "best option" for addressing climate change.

This paper, which begins with the word "Ignoring" is no exception. To wit, the first two sentences in introductory text:

To cope with the serious situation of climate change, carbon emission reduction has become the common consensus worldwide. (1) Many countries have set a goal for carbon neutrality. (2) Solar photovoltaics (PV) has the greatest potential to achieve this goal; PV power accounts for about 20 to 60 percent of the global electricity scenario in a largely or fully decarbonized context by 2050. (3)

Reference 3 is to a German publication written by German economists, not engineers:

Sebastian Weida, Subhash Kumar, Reinhard Madlener, Financial Viability of Grid-connected Solar PV and Wind Power Systems in Germany, Energy Procedia, Volume 106, 2016, Pages 35-45.

Nothing in the world is more important than economics, or so I hear.

The 12 month carbon intensity electricity production in Germany from the Electricity Map (Accessed March 22, 2023).



Among large countries in Europe, only Poland has a higher carbon intensity than Germany over 12 months, although Poland plans to replace its coal plants with nuclear, even as Germany has about completed its program to replace nuclear with coal. (To be fair, Serbia, Macedonia, Kosovo, Sicily, and Sardinia all have slightly higher carbon intensities than Germany over the last 12 months, but these do not represent major economies; France's carbon intensity, in "percent talk" is about 20% that of Germany.)
Anyway, before lapsing into soothsaying, the paper under discussion does hint at some of the things being ignored, consistent with the paper's title, while claiming, not quite believably for my mind, that solar arrays make great shelters for sheep:

Due to the lower power density of PV power compared to fossil energy, a large amount of land will be required to accommodate PV facilities in the future. (4) The management of solar parks as pasture is an ideal option in terms of reducing emissions from land use change and reducing the impact on native species in the hosting ecosystem. (5) Grasslands account for 30% of the world’s land area and have great potential to meet the demand for PV arrays, especially the deployment of PV arrays in grasslands, which will not preclude the ability of sheep to graze on the land around the PV arrays and provide shelter for sheep by the panels. (6−9) Therefore, grassland ecosystems rank highly in terms of their potential for PV array deployment. (10−12)

Grasslands? We don't need no stinking grasslands!!!!!

Then more soothsaying using units of peak power as opposed to acknowledging anything about the capacity utilization of solar arrays, "by 2035" soothsaying:

In recent years, the installed PV capacity in Northeast China has increased rapidly. (13) For instance, the total planned developable capacity of PV projects in Jilin Province amounts to 36.14 GW (by 2035), and dozens of concentrated solar power systems have been built in this province.

It can be shown - I'm too lazy to reproduce the reference right now - that the capacity utilization worldwide averages about 22%. If this were to hold in the sheep shaded grasslands of Northeast China "by 2035," carrying too many significant figures by using the number of sideral seconds in a year, 31,558,149 seconds, since the soothsaying carries too many significant figures, this works out to about 0.25 Exajoules of energy production, not counting the thermodynamic losses from batteries and hydrogen and all the other thermodynamic nightmares about which our anti-nukes like to wax romantic. In terms of average continuous power, it works out to a little less than 8 GW, again ignoring thermodynamic losses for energy storage, the equivalent of about 8 medium sized nuclear plants, although nuclear plants, requiring less than 20 hectares of footprint each are not very useful for shading sheep.

(The nuclear plants, of course, would not require complete replacement every 25 years.)

The authors continue:

The sustained flux global warming potential (SGWP) and the sustained flux global cooling potential (SGCP) are important indexes to measure a substance released into the atmosphere, (14) and they are also the key life cycle impact indicators to quantify the environmental performance of solar parks. (15) For PV modules manufactured in Europe and China, the life-cycle greenhouse gas (GHG) footprints were estimated to be 37.3 and 72.2 g CO2-eq kW h–1, respectively. (16) Previous studies have considered the GHG footprint during the production, transportation, and waste treatment processes of solar parks. (17−19) However, such changes in land use may affect soil processes, plant community dynamics, (20) and GHG emissions in grassland ecosystems. Therefore, there is a lack of accurate measurements of GHG emissions during the operation periods of solar parks, which may lead to an inaccurate assessment of the GHG footprint.

Reducing GHG emissions is one of the main advantages of PV power generation. (21) In simulation studies, research in Poland has calculated that a kilowatt of installed solar power saves up to NO2 by 16 kg, SO2 by 9 kg, and CO2 by 600–2300 kg compared to fossil fuels. (22) A 50 MW solar park could reduce CO2 emissions by up to 45 million tons compared with fossil fuels per year in Egypt. (23) Another report indicated that PV power generation was expected to reduce 46.5 Tg of CO2 emissions compared with 600 MW of coal-fired supercritical units in China. (24)...

They discuss some other studies of what may be being ignored, and thus summarize their own questions about these results, that is, what they propose to study:

The influence of the solar park on hosting ecosystems can be summarized as follows: first, solar park construction involves clearing and grading the soil surface, digging trenches to lay electric cables, which may contribute to part of vegetation loss, soil compaction, and increased erosion risks. (20) Second, solar park management may involve regular mowing and cleaning to avoid fire hazards and the loss of power generation caused by vegetation shading and dust accumulating on the PV panels. (26) Third, the operation period of solar parks in hosting ecosystems results in land use changes; large-scale PV arrays in solar parks have the potential to affect land surface albedo, (27) cause shading (28,29) and intercept precipitation. (30) Changes in surface albedo and soil moisture may directly and indirectly affect soil temperature. (31−33) The shading and intercept precipitation of PV panels may alter soil moisture patterns in grasslands. (34) Previous research found that shading by PV panels in desert locations might raise the soil temperature during the winter but reduce it during the other three seasons, and soil moisture in the shading zone was significantly higher than in ambient zones. (35) The sheltered zone was cool and dry in summer, but the gap zone between the PV panels was colder than the ambient zone and sheltered zone in winter; the PV arrays significantly affected the aboveground plant biomass and the plant species on the grassland. (10)

Grassland? We don't need no stinking grassland!

Here's some graphics from the author's results:

The study area:



The caption:

Figure 1. (a) Location of the Honghua solar park in the Songnen Grassland, Northeast China. (b) Three experimental zones of Ambient (the reference zone outside the PV arrays), Gap (the gap zone between the PV panels), and Under (the sheltered zone under the PV panels). (c) Schematic diagram of the PV panel installation. Angle A is the installation inclination of the PV bracket, AB is the length of the inclined surface of the PV panel assembly, and AD is the distance between the front and back row of PV arrays.

The caption:

Figure 2. Month dynamics of average VPD (a) and PAR receipts (b) in different experimental zones. Ambient, the reference zones outside the PV arrays; Gap, the zones between the PV panels; Under, the sheltered zones under the PV panels.

VPD = Vapor Pressure Deficit.

PAR = Photosynthetically active radiation.



The caption:

Figure 3. Soil temperature (ST), soil moisture (SM), pH, total organic carbon (TOC), total nitrogen (TN), carbon nitrogen ratio (C/N), nitrate nitrogen (NO3––N), ammonium nitrogen (NH4+–N), available phosphorous (AP), plant height (Height), coverage (Cover), and density (PD) in the L. chinensis community, Forb community, and A. scoparia community in different experimental zones (Ambient, the reference zones outside the PV arrays; Gap, the zones between the PV panels; Under, the sheltered zones under the PV panels) (mean ± SE). Different letters represent significant differences among different experimental zones (p < 0.05). ns indicates that the difference is not significant.

The caption:

Figure 4. Temporal variations of CO2 (a) flux, CH4 (b) flux, and N2O (c) flux in different experimental zones during the growing season (mean ± SE). Ambient, the reference zones outside the PV arrays; Gap, the zones between the PV panels; Under, the sheltered zones under the PV panels. Significance levels are as follows: *p < 0.05, **p < 0.01 and ***p < 0.001, ns, no significant difference.

The caption:

Figure 5. Average fluxes of CO2, CH4, and N2O in the L. chinensis community (L. chinensis), Forb community (Forb), and A. scoparia community (A. scoparia) in different experimental zones (Ambient, the reference zones outside the PV arrays; Gap, the zones between the PV panels; and Under, the sheltered zones under the PV panels) (mean ± SE). Different letters represent significant differences among different experimental zones (p < 0.05). ns indicates that the difference is not significant.

The caption:

Figure 7. SGWP between ambient zones (Ambient) and PV array zones (a), GHG footprint during operation from the gap zones (Gap) and the shelter zones (Under) under the PV panels in the PV arrays (Eh) (b), and the missing percentage of GHG footprints of PV facilities reported in literature compared to ours (c). Yue:, (16) Mar:, (75) Nia:, (76) Mil:, (77) Lec:, (78) Kim:, (79) Ito:, (80) Hou:, (81) Her:, (82) Bey:, (83) Ber:, (84) Bos:. (85) The significance levels are as follows: *p < 0.05, **p < 0.01 and ***p < 0.001, ns, no significant difference.

The caption:

Figure 8. SEMs to identify the explanatory variables of CO2 flux (a), CH4 flux (b), and N2O flux (c). Numeric values adjacent to arrows are standardized path coefficients, analogous to relative regression weights, and indicative of the effect size of the relationship (n = 225). Continuous and dashed arrows indicate positive (red color) and negative (green color) effects, respectively. For each model, the proportion of variance explained (R2) and the various goodness-of-fit statistics are shown below the response variables. Significance levels are as follows: *p < 0.05, **p < 0.01 and ***p < 0.001. Abbreviations: Zone, different experimental zones (Ambient, Gap, and Under); PCT, different PCTs (L. chinensis community, Forb community, and A. scoparia community); ST, soil temperature; SM, soil moisture; C/N, soil carbon nitrogen ratio; PD, PD.

The author's conclusions:

The main processes of PV arrays affecting grassland vegetation, such as shading by PV panels, changing the surface temperature and precipitation distribution, and affecting the evaporation of surface water are approximately the same in grasslands at different locations, as demonstrated by previous studies of solar parks in Oxfordshire (UK), (10) the South Moravian Region (CR), (98) and Southern France. (99) China’s grasslands cover 392.8 million ha, accounting for 40% of the national land area. (100,101) The L. chinensis meadow selected for this study is located in the Songnen grassland in Northeastern China, which is the most typical and largest grassland type in China and has good representativeness. Therefore, we are confident that the field results of this study can be largely extended to grasslands in other parts of the world and are of general significance.

Ah...wonderful...392.8 million hectares of grasslands are available to be industrialized into solar parks, and plenty of shade for sheep.

We're saved.

History will not forgive us (for thinking so), nor should it.

Have a nice evening.