Main  主要

Solar photovoltaic (PV) technology is one of the world’s most promising renewable energy generation technologies1. Global PV installed capacity increased from 0.8 GW in 2000 to 891.3 GW by 20212, and approximately 13,345 GW are projected to be in operation by 20503,4,5,6,7,8. Nevertheless, the booming PV technology9,10, particularly in the domain of utility-scale installations, has concurrently imposed substantial pressures on land resources9,11. Furthermore, the deployment of utility-scale photovoltaic (USPV) facilities alters the preexisting land-cover types, impacting the carbon (C) pool (including vegetation C and soil C) of the hosting ecosystem. These changes can subsequently affect the C footprint of the USPV plants12,13.
太阳能光伏(PV)技术是世界上最具前景的可再生能源发电技术之一。全球光伏装机容量从 2000 年的 0.8 吉瓦增长到 2021 年的 891.3 吉瓦,预计到 2050 年将运营约 13345 吉瓦。然而,蓬勃发展的光伏技术,特别是在大型电站领域,同时对土地资源施加了巨大压力。此外,大型光伏(USPV)设施的建设改变了原有的土地覆盖类型,影响了宿主生态系统的碳(C)库(包括植被碳和土壤碳)。这些变化随后可能影响 USPV 植物的碳足迹。

Although recent years have witnessed an emerging focus on this issue, the predominant emphasis has been on the assessment of individual USPV plants with specific land-cover types14, or on a regional scenario analysis using integrated assessment model15. To our knowledge, a comprehensive evaluation covering global USPV plants sited on different land-cover types and with diverse land management strategies remains absent, which has resulted in unknown global patterns and massive uncertainty about the magnitude of the USPV effect on the C pool of the hosting ecosystem, as well as its role in the C footprint of USPV plants. Further complications arise from the fact that highly accurate worldwide USPV time series data are lacking, particularly concerning the installation dates of these facilities16,17,18,19,20,21. This is because the key factors used to assess changes of the C pool and C footprint, including the PV panel efficiency, the emission intensity associated with PV panel manufacturing and the land-cover type both before and after the construction of USPV facilities, exhibit variations over time. Resolving these major gaps should improve our understanding of how the C pool is altered by USPV deployment, what role it plays in the C footprint of USPV plants and how the land of USPV plants should be managed to achieve mutual benefits in USPV development and ecosystem C pool enhancements.
尽管近年来人们开始关注这一问题,但主要精力集中于评估具有特定土地覆盖类型的单个美国光伏电站 14 ,或使用综合评估模型进行区域情景分析 15 。据我们所知,目前尚缺乏对全球不同土地覆盖类型、采用多样化土地管理策略的美国光伏电站进行全面评估的研究,这导致全球模式未知,美国光伏电站对宿主生态系统碳库的影响程度及其在美国光伏电站碳足迹中的作用存在巨大不确定性。进一步复杂化的是,由于缺乏高精度的全球美国光伏时间序列数据,特别是这些设施的建设日期数据 16,17,18,19,20,21 ,使得评估碳库和碳足迹变化的关键因素——包括光伏板效率、光伏板制造相关的排放强度以及美国光伏设施建设前后的土地覆盖类型——随时间变化而难以确定。 解决这些主要差距将有助于我们更好地理解碳库如何因大型光伏系统部署而改变,它在大型光伏系统碳足迹中扮演什么角色,以及如何管理大型光伏系统的土地以实现大型光伏系统发展与生态系统碳库增强之间的互利共赢。

In this study, we leveraged a time series dataset of USPV plants to quantify the alterations in land cover and the subsequent changes in the C pool of the hosting ecosystem induced by USPV deployment and elucidate its role in the C footprint of USPV plants. Our dataset encompasses USPV plants worldwide and includes diverse historical data, particularly the installation date, thus allowing us to discern a global pattern in the response of C pool to the rapid expansion of USPV and its contribution to the C footprint of USPV plants, examine how it reacts to changes in climate, microclimate and technology levels, and offer insights for land management strategies of USPV plants.
在本研究中,我们利用了美国光伏电站的时间序列数据集,以量化土地覆盖的变化以及由美国光伏电站部署引起的宿主生态系统碳库的后续变化,并阐明其在美国光伏电站碳足迹中的作用。我们的数据集涵盖了全球的美国光伏电站,并包括多样化的历史数据,特别是安装日期,从而使我们能够揭示碳库对美国光伏电站快速扩张的响应模式及其对美国光伏电站碳足迹的贡献,考察其如何对气候变化、微气候和技术水平的变化做出反应,并为美国光伏电站的土地管理策略提供见解。

Land-cover changes after USPV deployment
美国光伏电站部署后的土地利用变化

Based on the global inventory of PV solar energy generating units proposed previously16, we developed a time series dataset for global USPV installations constructed from 2000 to 2018, leveraging remote sensing data and machine learning algorithms (Supplementary Discussion, section A). On the basis of the dataset, we found that cropland, particularly that growing C3 crops, emerged as the preferred site for the deployment of USPV plants with the exception of Africa (Fig. 1a,c,d), which aligns with the outcomes of prior studies16. However, a reduced use of cropland for USPV deployment was witnessed, particularly for USPV plants constructed after 2013. This reduction in cropland use can be attributed to the geographical shift in USPV deployment focus from Europe towards Asia and North America22 (Supplementary Discussion, section B), where croplands were utilized less frequently for USPV construction compared with Europe. In addition, food security considerations may also have a role, as the increased size of USPV plants (Supplementary Fig. 1) necessitates expansive land areas for their construction. By contrast, since 2013, the use of grassland, dominantly C3 grassland, for USPV construction has increased by approximately 5% compared with prior years.
基于先前提出的全球光伏发电单元清单 16 ,我们利用遥感数据和机器学习算法,构建了一个 2000 年至 2018 年全球美国光伏电站部署的时间序列数据集(补充讨论,A 部分)。基于该数据集,我们发现耕地,尤其是种植 C3 作物的耕地,成为美国光伏电站部署的首选地点,除非洲外(图 1a,c,d),这与先前研究的结果 16 一致。然而,我们观察到耕地在美国光伏电站部署中的使用减少,尤其是在 2013 年后建设的美式光伏电站。耕地使用的减少可归因于美国光伏电站部署重点从欧洲转向亚洲和北美的地理变化 22 (补充讨论,B 部分),与欧洲相比,亚洲和北美的耕地在使用频率上较少用于美国光伏电站建设。此外,粮食安全问题也可能发挥作用,因为美国光伏电站规模的增加(补充图 1)需要更广阔的土地面积进行建设。 相比之下,自 2013 年以来,用于美国光伏电站建设的草地(主要是 C3 草地)使用量比前几年增加了约 5%。

Fig. 1: Land-cover patterns before and after USPV deployment.
图 1:美国光伏电站部署前后的土地利用模式。
figure 1

a, The spatial pattern of the land-cover type before USPV construction. b, The spatial pattern of the land-cover type after USPV construction. c, Changes of the proportion of different preconstruction land-cover types occupied by USPV plants from 2000 to 2018. d, Proportions of different preconstruction land-cover types occupied by USPV plants by continent. e, Changes in the proportion of different land-cover types after construction from 2000 to 2018. f, The proportion of different land-cover types after construction by continent. AF, Africa; AS, Asia; AUS, Australia; EU, Europe; NA, North America; SA, South America.
a,美国光伏电站建设前的土地利用类型空间模式。b,美国光伏电站建设后的土地利用类型空间模式。c,2000 年至 2018 年,不同建设前土地利用类型被美国光伏电站植物所占比例的变化。d,不同建设前土地利用类型被美国光伏电站植物所占比例按洲划分。e,2000 年至 2018 年,建设后不同土地利用类型比例的变化。f,建设后不同土地利用类型比例按洲划分。AF,非洲;AS,亚洲;AUS,澳大利亚;EU,欧洲;NA,北美洲;SA,南美洲。

Source data  来源数据

Several land management decisions may be implemented after the construction of USPV plants, including land clearing23, which removes the existing vegetation and covers the ground with gravel, potentially leading to a gradual loss of belowground C; maintaining the original land cover15; and converting to another land-cover type, which is usually grassland24. We found that, on average, over 77% of the land encompassing USPV plants was predominantly managed as grassland after construction, with a continuously increased proportion of approximately 15% from 2000 to 2018 (Fig. 1b,e). The adoption of land clearing regimes showed a decreasing trend overall but at high variability between 6% and 25%. Spatially, Europe exhibited the highest percentage of USPV plants managing their grounds as grassland at approximately 92%, followed by North America, Asia and Australia (Fig. 1f). However, over 45% and 40% of the grounds of USPV plants installed in Africa and South America were managed as bare land, respectively.
在美国家用光伏电站建设完成后,可能会实施几种土地管理决策,包括土地清理 23 ,这会移除现有植被并用砾石覆盖地面,可能导致地下碳逐渐流失;维持原始土地覆盖 15 ;以及转换为另一种土地覆盖类型,通常是草地 24 。我们发现,平均而言,超过 77%的美国家用光伏电站所涵盖的土地在建设后主要以草地为主管理,从 2000 年到 2018 年,其比例持续增加,约增加了 15%(图 1b,e)。采用土地清理制度总体呈下降趋势,但在 6%到 25%之间具有高度变异性。从空间上看,欧洲的美国家用光伏电站以约 92%的比例管理其土地为草地,其次是北美、亚洲和澳大利亚(图 1f)。然而,非洲和南美洲安装的美国家用光伏电站的土地中,分别有超过 45%和 40%被管理为裸地。

These stark regional differences in management practices reflect varying approaches to USPV land stewardship. The high prevalence of grassland management in Europe demonstrates successful integration of ecosystem preservation with solar deployment, while the predominance of bare land management in Africa and South America suggests opportunities for improved land management strategies. Moreover, there was notable spatiotemporal heterogeneity of land-cover changes (Supplementary Fig. 2). For example, more than 90% of the croplands encompassing USPV plants were converted to grasslands in Europe, while approximately 20% of the croplands were changed to bare land in Asia. Potential explanations of this regional discrepancy include differences in climatic conditions, the availability of land types and local policies16,25,26,27,28.
这些在管理实践上的显著区域差异反映了美国光伏土地管理的不同方法。欧洲草地管理的普遍性表明了生态系统保护与太阳能部署的成功整合,而非洲和南美洲裸地管理的优势则暗示了改进土地管理策略的机会。此外,土地覆盖变化存在明显的时空异质性(补充图 2)。例如,在欧洲,包含美国光伏植物的大部分耕地(超过 90%)被转化为草地,而在亚洲,约 20%的耕地被改造成了裸地。这种区域差异的潜在解释包括气候条件差异、土地类型可用性和地方政策的差异。

C pool alterations from land-cover changes
陆地覆盖变化引起的碳库变化

The land-cover changes ensuing from the deployment of USPV plants induced alterations in the C pool of the hosting ecosystems. We estimated a global C pool change of 2.12.3+0.6TgC (ensemblemeandifferencetopercentile25+differencetopercentile75) from the hosting ecosystems induced by USPV installations constructed between 2000 and 2018, with apparent individual differences among USPV plants (Fig. 2a). Spatial analysis revealed that USPV plants sited in Europe were the predominant contributors to the C gain, amounting to 2.11.5+0.3TgC, followed by the installations in Asia. By contrast, a loss in the C pool was observed for USPV plants in the other continents, particularly North America by 0.60.3+0.1TgC. The C gain arose mainly from USPV plants that were sited on C3 cropland, which were subsequently converted to C3 grassland after construction (Fig. 2b), owing to the relatively large difference of C density between C3 croplands and C3 grasslands hosting USPV plants (Supplementary Fig. 3). By contrast, USPV plants sited on C3 grassland and C3 cropland whose grounds were managed as bare land dominated the C loss, attributed to the relatively large plant area and C density difference, respectively. Notably, the source of the C loss represented apparent variability at continent scale. USPV plants sited on C3 grassland resulted in the majority of C loss in Asia, while those located on forest area and shrubland dominated the C loss in Europe and North America, respectively (Supplementary Fig. 4).
由美国光伏电站的部署所引发的土地利用变化导致宿主生态系统的碳库发生改变。我们估计了 2000 年至 2018 年间由美国光伏电站建设所引起的宿主生态系统的全球碳库变化为 2.12.3+0.6TgC ( ensemble meandifferencetopercentile25+differencetopercentile75 ),其中美国光伏电站之间存在明显的个体差异(图 2a)。空间分析表明,位于欧洲的美国光伏电站是碳增加的主要贡献者,达到 2.11.5+0.3TgC ,其次是亚洲的电站。相比之下,其他大洲的美国光伏电站碳库出现了减少,特别是在北美地区减少了 0.60.3+0.1TgC 。碳增加主要来自位于 C3 农田上的美国光伏电站,这些电站建设后转变为 C3 草地(图 2b),这是由于 C3 农田和 C3 草地承载的美国光伏电站之间的碳密度差异相对较大(补充图 3)。相比之下,位于 C3 草地和 C3 农田且地面管理为裸地的美国光伏电站主导了碳的减少,这归因于相对较大的植物面积和碳密度差异。 值得注意的是,C 损失的来源表现出大陆尺度的明显变化。位于 C3 草地上的美国光伏电站导致了亚洲大部分的 C 损失,而位于森林区域和灌丛地带的光伏电站则分别主导了欧洲和北美的 C 损失(补充图 4)。

Fig. 2: C pool changes induced by USPV deployment.
figure 2

a, The spatial pattern of C pool changes. The numbers overlaid on the map denote ensemblemeandifferencetopercentile25+differencetopercentile75. b, Total C pool changes for USPV plants with different land-cover conversion types. MC, mosaic cropland; MHC, mosaic herbaceous cover; MNV, mosaic natural vegetation; MTS, mosaic tree and shrub; SV, sparse vegetation. c, Total C pool changes by construction year. Values larger than zero represent a C gain, while values smaller than zero represent a C loss. The absence of remote sensing data around 2012 leads to the exclusion of this year from the analysis (for further details, see the Methods).

Source data

Temporally, the C gain peaked at 0.42 TgC for USPV plants constructed in 2011, and showed a sudden decrease for those constructed in 2013, subsequently experiencing a continuous increase thereafter (Fig. 2c). The sudden decrease in the C gain was attributable to fewer USPV plants constructed in 2013, and most importantly the geographical shift in USPV deployment focus from Europe towards Asia and North America22 (Supplementary Discussion, section B). The land of the majority of USPV plants sited in Europe was maintained as grassland after construction, while in Asia and North America, more than 20% of the USPV plants led to the conversion of their grounds into bare land (Supplementary Fig. 2). Fortunately, the proportion of USPV plants managing their grounds as bare land showed a decreasing trend since 2014 (Fig. 1e), which can explain the continuous increase in the C gain from 2014 to 2017.

Although the overall impact of USPV deployments on the ecosystem C pool, quantified herein as a C gain of 2.1 TgC, may currently seem modest owing to the relatively limited spatial footprint of USPV plants constructed between 2000 and 2018 (<4,000 km2), it was projected that approximately 54,737 km2 of land will be occupied for USPV deployment by 2050 (Supplementary Discussion, section C), potentially leading to a considerable alteration of the terrestrial C pool13. Thus, we suggest that the impact of USPV deployment on land cover and the subsequent C pool of the hosting ecosystem should be carefully considered in PV planning and management25,29,30.

Effect of C pool change on C footprint of USPV

The C footprint of global USPV plants, defined as the greenhouse gas emissions per unit of power generation from a life cycle perspective, considering the contribution from C pool changes (ranging from 76.326.5+7.5 to 94.030.0+12.3 grams of CO2 equivalent (CO2e) per kilowatt-hour, with an average absolute value of 10.53.8+0.5g CO2e kWh−1) (Supplementary Fig. 5a), spanned from 7.87.4+25.6 to 182.729.6+31.9g CO2e kWh−1, with a mean value of approximately 56.30.1+3.4g CO2e kWh−1 (Supplementary Fig. 5b). The impact of changes in the C pool on the C footprint of USPV plants exhibited notable variability across individual plants, with a range extending from 112.94.5+48.2% to 106.019.9+42.4% (Fig. 3a), and an average absolute impact of 15.95.8+1.0% (Fig. 3b). In particular, USPV plants in Europe and North America were more sensitive to C pool alterations, with an average absolute impact (median value) reaching up to 14.30.8+6.0% and 11.61.5+6.6%, respectively. Therefore, ignoring the contributions from changes in the C pool can result in substantial misestimates of the C footprint of USPV plants.

Fig. 3: Effect of C pool changes on C footprint of USPV plants.
figure 3

a, The spatial pattern of the impact. The numbers overlaid on the map denote the absolute impact represented by ensemblemediandifferencetopercentile25+differencetopercentile75. b, The absolute impact of C pool changes on the C footprint of USPV plants estimated utilizing different C density datasets. n in the legend denotes the number of USPV plants included in the calculation. c, Projected changes in absolute impact of C pool changes on the C footprint of USPV plants estimated on the basis of the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) model.

Source data

Moreover, we performed a scenario analysis to reveal the impacts of technology innovation, which would lead to a reduction in the emission intensity of USPV construction, and the C pool alteration caused by climate change31 on the role of PV deployment induced C pool changes in the USPV C footprint among all the current USPV plants. Predicated on the anticipated reduction in emission intensity of USPV installations themselves (Supplementary Discussion, section D)32 and the predicted C density in the future (Supplementary Methods, section A), we estimated that the absolute impact of changes in the C pool on the C footprint of USPV plants will be amplified by around 1-, 2- and 7-fold by 2030, 2040 and 2050, respectively (Fig. 3c). We further investigated the contributions of technology innovation and climate-change-induced C pool alteration to the overall impact and found that the amplified impact was predominantly attributed to technology innovation rather than climate-change-induced C pool changes (Supplementary Fig. 6).

In addition, we compared the emissions or emission reductions induced by C pool changes due to USPV deployment with the emissions avoided by replacing fossil energy with PV power generation. Although the emissions or emission reductions induced by C pool changes were currently modest compared with the avoided emissions (an absolute ratio of approximately 1.9%), this figure is expected to increase continuously and rapidly as the electricity mix continues to decarbonize (Supplementary Discussion, section E), indicating that nature-based solution would become imperative to achieve climate targets33.

Implication for USPV land management

Given that C pool changes exert a critical role in the C footprint of existing USPV plants and they are induced by land-cover changes, we next conducted a scenario analysis to investigate the potential impacts of different land management strategies on the C pool of the hosting ecosystem and, subsequently, on the C footprint of these existing USPV plants. To do that, four hypothetical scenarios were designed to alter the current land management strategies of these global USPV plants (Methods). The findings revealed a substantial C gain totalling 4.64.3+1.8 and 10.61.3+13.1TgC (or 1.31.2+0.5 and 3.00.4+3.7kgCm2) under S2 and S3, which were 5-fold and twice that under the current baseline, respectively (Fig. 4a). By contrast, under S1 and S4, a potential C loss of 2.81.1+0.9 and 20.70.8+5.5TgC (or 0.80.3+0.2 and 5.80.2+1.6kgCm2) was estimated, and it was estimated that 53% of global USPV plants could achieve C pool enhancements by optimizing land management strategies according to the implication from the S3 scenario. Spatially, C loss predominantly originated from USPV plants sited in North America, Europe and Asia under S1 (Supplementary Fig. 7a), while approximately 80% of the C loss was induced by USPV plants located in Asia and Europe under S4 (Supplementary Fig. 7d). By contrast, USPV plants sited in Asia and Europe dominated the C gain by more than 97% and 88% under S2 and S3, respectively (Supplementary Fig. 7b,c).

Fig. 4: C pool and C footprint changes under different land management scenarios.
figure 4

a, C pool changes under different scenarios. Negative values represent a C loss, while positive values represent a C gain. b, Changes in C footprint of USPV plants under different scenarios compared with the current condition. Positive values represent an increase in the C footprint, while negative values denote a reduction in the C footprint. S1: the all-croplands postconstruction scenario under which the grounds of all USPV plants are managed as cropland; S2: the all-grasslands postconstruction scenario under which all the USPV plants manage their grounds as grassland; S3: the optimal scenario under which all the USPV plants manage their grounds with land-cover types optimized for the highest C density potential based on local environmental conditions; S4: the worst-case scenario under which the grounds of all the USPV plants are managed as bare land. n in the legend denotes the number of datasets used in the calculation.

Source data

An estimated average C footprint of 62.70.9+0.3 and 73.10.6+0.4g CO2e kWh−1 was obtained for global USPV plants under S1 and S4, respectively (Supplementary Fig. 8a,d), which were 11.57.4+8.7% and 30.013.7+11.7% higher than that of the current baseline (Fig. 4b). Notably, USPV plants in Europe were apparently more sensitive to C pool alterations under S1 and S4, with the C footprint increased by more than 20% and 50%, respectively. The potential explanation included the high C density of the hosting ecosystem in the USPV plants sited in Europe owing to managing the grounds as grassland after construction, and the relatively low C emission intensity associated with the manufacturing of USPV plant components in Europe (Supplementary Fig. 9). This observation further underscores the imperative of integrating C pool considerations into the comprehensive assessment of the C footprints of USPV plants, in light of the anticipated continual reduction in C emissions from USPV installations themselves32,34. By contrast, under S2 and S3, the estimated average C footprints of global USPV plants were 55.10.6+4.3 and 53.65.3+1.0g CO2eq kWh−1, respectively (Supplementary Fig. 8b,c), a reduction of 2.00.9+0.1% and 4.30.2+9.3% from the current baseline, with the most pronounced plant-scale decrease exceeding 100%. USPV plants sited in Asia, South America and Africa exhibited the greatest potential for C footprint mitigation, attributed primarily to the relatively high proportion of USPV plants currently managing their grounds as bare land in these continents (Fig. 1f).

Climate change may disturb the terrestrial C pool as well as affect the power generation potential of PV systems. Although we did not investigate this aspect in detail in our C pool impact estimation and C footprint accounting because it remains outside the scope of this study, it deserves attention and further investigation because climate change can exert a substantial influence on the C pool35,36,37,38 and can moderately affect PV power outputs39. In addition, the potential indirect land-use changes induced by USPV management decisions and their subsequent impact on the C pool warrant further investigation15.

Sensitivity to microclimate impact

Given that the existence of PV panels can alter the local albedo, affect the energy balance and further result in microclimate changes40, we carried out a sensitivity analysis to preliminarily reveal the impact of microclimate changes on our results. The sensitivity analysis comprised two components: an albedo-based analysis and a ‘whole scene’ assessment (Methods). The results presented here were estimated using the observation-based dataset. However, the results calculated utilizing the model-derived C density datasets can also be found in Supplementary Fig. 10 and the ‘Data availability’ section. For the albedo-based analysis, we found that, on average, the C pool of the hosting ecosystem after construction would be enhanced by ~16% to ~34%, primarily due to temperature decreases induced by the effective albedo increase estimated for most USPV plants (Supplementary Fig. 10a). An estimated average increase in C pool changes of ~30% to ~101% was then obtained (Supplementary Fig. 10b), which subsequently led to a reduction in the C footprint of USPV plants, spanning from approximately 4% to 12% (Supplementary Fig. 10c). Regarding the whole scene assessment, we found that, in general, lower temperatures and higher precipitation would lead to an increase in C pool of the hosting ecosystem after construction, with the highest C gain surpassing 60% (Supplementary Fig. 11a). By contrast, higher temperatures and lower precipitation would result in a C loss of up to approximately −40%. As a result, USPV-deployment-induced C pool changes would vary widely, ranging from −141.2% to 208.1% under different scenarios (Supplementary Fig. 11b). Correspondingly, the C footprints of USPV plants were projected to change by −26.2% to 12.7% (Supplementary Fig. 11c).

The results indicated that the C gain of the hosting ecosystem and the C footprint reduction of the USPV plants may be more substantial if microclimate impacts are considered. However, given the complexity of microclimate impacts exerted by PV panels24,41,42,43, which cannot be fully captured by the sensitivity analysis conducted in this study44,45,46, it is suggested that more studies on microclimate changes in response to PV deployment should be carried out across PV plants located in diverse ecosystems and climate zones to bridge the existing knowledge gap47.

Our study pioneers the evaluation of the impact that global USPV deployment has on the C pool of the hosting ecosystem, revealing its importance in the C footprint of USPV plants, although uncertainties remain (Supplementary Discussion, section F). Stakeholders, developers and policymakers can utilize our results to achieve a mutually beneficial outcome, simultaneously realizing C pool enhancements and reducing the C footprint of USPV plants.

Methods

Developing a time series dataset

We developed a time series dataset of global USPV installations leveraging remote sensing data and machine learning algorithms (see the overall flow chart in Supplementary Fig. 12). This dataset encapsulates key details such as the construction date of each USPV plant, along with installed capacity, panel efficiency and ground coverage ratio.

A state-of-the-art global inventory of solar PV energy generating units that contains all the commercial, industrial and USPV installations around the world deployed before 2018 was used as the basic data16. We selected 37,106 out of 68,661 generating units from the inventory according to the definition of USPV from International Energy Agency (IEA), that is, greater than 1 MW nameplate capacity48. Then, spatial clustering was performed to amalgamate the generating units referring to the same plant using a neighbourhood search distance of 400 m (ref. 21). This process resulted in 28,769 USPV plants used for installation date identification.

Landsat 5 and Landsat 8 atmospherically corrected surface reflectance data with 30-m resolution49,50 served as the primary inputs for implementing the temporal cluster matching (TCM) algorithm20,51 coupled with the Pettitt change-point detection algorithm52 to identify the construction date of each USPV plant. The temporal coverage of Landsat 5 and Landsat 8 remote sensing data spans from 1984 to the present, with a gap between May 2012 and February 2013, when Landsat 5 was decommissioned and Landsat 8 was not yet in operation. The decision against utilizing Landsat 7 data to bridge this gap stems from the scan line corrector malfunction in May 2003, which substantially compromised the utility of the data post-failure53. Consequently, the absence of remote sensing data during this interim period may influence the identification accuracy of the construction date from May 2012 to February 2013, leading to the exclusion of this period from our comprehensive analysis.

The TCM algorithm, initially developed by the Microsoft AI for Good Research Lab in collaboration with Stanford RegLab20,51, is predicated on the observation that the construction of a PV plant alters the colour and texture characteristics of the land, making the PV plant’s footprint distinct from its surroundings. Utilizing k-means clustering, the algorithm partitions pixels within the PV plant area and its surroundings into k clusters, subsequently calculating the discrete distribution of cluster indices for both the PV plant and its surrounding area separately. Kullback–Leibler (KL) divergence is used to determine the extent to which the colour and texture characteristics within the PV plant area diverge from those of the surrounding landscape. A higher KL-divergence value suggests a greater likelihood that a PV plant has been constructed. The integration of the Pettitt change-point detection algorithm with the TCM algorithm was undertaken to identify the construction dates of USPV plants instead of using the decision threshold method originally used in the TCM algorithm to identify PV construction based on whether the KL-divergence value exceeds the threshold. The rationale behind this modification lies in the observation that the decision threshold exhibits variability across diverse PV plants52, making it challenging to accurately ascertain the construction date of USPV plants worldwide using a single threshold. The Pettitt change-point detection algorithm, by contrast, offers a more generalized approach that accommodates the heterogeneity of PV plants, circumventing the subjective determination of a decision threshold, thereby enhancing the accuracy of construction date identification across the global spectrum of USPV plants.

The installed capacity of each USPV plant was estimated as16

CAC=A×GTI×GCR×η÷PVOUT÷ILR,
(1)

where CAC is the installed capacity of a USPV plant, A is the area of the USPV plant, GTI is the incident irradiance at the optimal tilt angle of the USPV plant location, which is obtained from the Global Solar Atlas54, GCR is the ground coverage ratio, η is the panel efficiency, PVOUT is the PV solar energy production intensity, which is also obtained from the Global Solar Atlas, and ILR is the inverter loading ratio.

By utilizing our identification of the construction dates for USPV plants, we incorporated time-varying values of GCR, η and ILR into equation (1), as opposed to using constant values. GCR was calculated on the basis of the latitude and the mounting types used55. Given the unavailability of specific mounting type data for each USPV plant, we relied on the global market distribution of PV mounting types, which encompasses both fixed-tilt and tracking axis56. The annual variation in η for various panel types was obtained from the literature57,58,59. Similar to the mounting type, the exact panel types utilized in each USPV plant were not directly accessible. Thus, we applied the global market shares of different PV panel types60, including monocrystalline silicon (Mono-Si), polycrystalline silicon (Poly-Si), amorphous silicon (a-Si), cadmium telluride (CdTe) and copper indium (gallium) selenide (CI(G)S), to compute a weighted average η for USPV plants constructed in different years. The data for the annual ILR were sourced from the Energy Information Administration61.

The estimation of land-cover changes resulting from the deployment of USPV plants was conducted leveraging the identified construction dates of these plants. The European Space Agency (ESA) Climate Change Initiative 300-m-resolution land-cover data covering 1992–2020 were used to determine the preconstruction land-cover types62. To assess the dominant land-cover types present at the USPV plant locations after construction, the ESA WorldCover dataset for the year 2021, featuring a higher resolution of 10 m, was used63. The enhanced resolution of the ESA WorldCover data facilitates the accurate extraction of the predominant land-cover type within the boundaries of the USPV plants.

The Google Earth Engine (GEE) platform was used to acquire and preprocess remote sensing data for our analysis, which included tasks such as image clipping, cloud cover filtering and image band extraction. GEE is a comprehensive platform designed for Earth science data and analysis at a planetary scale, which houses a vast catalogue of satellite imagery and geospatial datasets including the Landsat series datasets. More details can be found at https://earthengine.google.com. The calculation of the KL divergence for the USPV plants was also performed utilizing GEE, leveraging a corresponding Python package64,65. The Pettitt change-point detection and subsequent postprocessing operations were conducted offline using Python, ArcGIS and other auxiliary software and tools.

Quantifying impacts on C pool

We leveraged several C density datasets to investigate C pool changes induced by worldwide USPV deployment, encompassing one observation-based and ten model-derived datasets (Supplementary Methods, section B, and Supplementary Table 1). In instances where some grid cells lack C density data for specific land-cover types present before or after USPV construction, owing to the relatively coarse spatial resolution of the C density datasets when compared to the scale of an individual USPV plant, an extrapolation method was used. This method estimates the C density for each land-cover type on the basis of the similarity of temperature and precipitation in the cell to those in the other cells with the same land-cover type containing C density data. A threshold of 1 °C for temperature and 50 mm for precipitation was utilized to identify cells with similar climatic conditions. The average C density value from these similar cells was then allocated to the cells lacking C density information. Data on the annual average temperature and total precipitation for each cell were sourced from the ERA5-land hourly dataset with a spatial resolution of approximately 0.1° (ref. 66).

We calculated C pool changes induced by a USPV plant, denoted as Ieco, by multiplying the difference in C density before and after construction by the plant’s area (equation (2)). The C density difference was estimated by comparing the mean C density (averaged over multiple decades) of land-cover types before and after construction. This mean C density data were calculated individually on the basis of each of the 11 C density datasets.

Ieco=A×(CDAmeanCDBmean),
(2)

where CDAmean is the mean C density of the hosting ecosystem within the boundary of the USPV plant after construction, CDBmean is the mean C density of the hosting ecosystem within the boundary of the USPV plant before construction. Both CDAmean and CDBmean encompass the C density of both vegetation and soil for all land-cover types, except for cropland. For cropland, only the C density of soil is considered, predicated on the understanding that the majority of vegetation C in cropland returns to the atmosphere in the form of CO2 within a short time period67. CDAmean and CDBmean were derived from the previously mentioned C density datasets, based on the land-cover types identified before and after the construction of the USPV plant.

Accounting for USPV C footprint

The C footprint of each USPV plant was assessed leveraging the developed time series dataset. The system boundaries encompass emissions or emission reductions from PV panel manufacturing, the balance of system (BOS) and the hosting ecosystem. Emissions arising from transportation, operation and maintenance, and the end-of-life phase were excluded, because the contribution from these phases is comparatively minimal68,69, and the majority of USPV plants are still in operation, leading to a lack of data regarding the end-of-life stage.

The emission from PV panel manufacturing for a specific USPV plant, denoted as Ep, is calculated on the basis of the emission intensity of PV panel manufacturing, the nominal capacity of PV modules, trade data of PV panels and the market share distribution of various PV panel types

Ep=CDC×j=1m(Spanelj×i=1n(Stradei×EFij))
(3)
CDC=CAC×ILR,
(4)

where CDC is the nameplate capacity of the PV modules installed within the PV plant, Spanelj is the market share of the panel type j, Stradei is the market share of PV panels exported from country or region i to the nation hosting the PV plant, inclusive of domestic supply, EFij is the emission intensity of panel type j produced in country or region i, m = 1, …, 5 denotes the enumeration of PV panel types, specifically Mono-Si, Poly-Si, a-Si, CdTe and CI(G)S, and n denotes the enumeration of countries or regions producing PV panels.

We compiled a year-specific country-to-country trade look-up table for PV panels using data from the International Trade Centre Trade Map70 to obtain country-specific market share information for PV panels. This approach accounted for the trade matrix among countries, rather than relying on an overall market share that overlooked country-specific differences. In addition, the proportion of domestic PV panel supply was derived from a report by the IEA Photovoltaic Power Systems Programme71. These datasets were amalgamated to calculate the year- and country-specific Stradei. The emission intensities of the various types of PV panel manufactured in distinct countries or regions were taken from the existing literature and the ecoinvent database (Supplementary Table 2). For panel types supported by ample data, regression analyses were conducted to obtain the temporal evolution of emission intensity for our analysis. By contrast, for panel types without sufficient data (for example, only 1 or 2 years of data available), a default reduction rate in emission intensity was used (a 45% decrease from 2011 to 2020), as documented in a special report by the IEA32.

The emissions from the BOS, denoted as EBOS, encompass emissions from the mounting system, emissions related to electric installations (excluding inverters) and emissions from inverters.

EBOS=Em+Eei+Einverter
(5)
Em=A×GCR×EFm
(6)
Eei=CDC÷570×EFei
(7)
Einverter=CAC÷500×2×EFinverter,
(8)

where Em represents the emissions from the mounting system, Eei denotes the emissions from the electric installation and Einverter represents the emissions from the inverters utilized within the PV plant. Correspondingly, EFm is the emission intensity for the mounting system, EFei denotes the emissions from the electric installation component for a module with a capacity of 570 kWp and EFinverter denotes the emissions from an inverter with a capacity of 500 kW. The factor of 2 is introduced to account for the 15-year lifespan of an inverter, which is half of the lifespan of a PV plant. All emission intensity figures used in the calculation of the BOS emissions were sourced from the ecoinvent database.

The power output of a specific PV plant at time t, denoted as Pout(t), was calculated by the PV power generation potential (PVpot) and the installed capacity of the plant72 as

Pout(t)=PVpot(t)×CAC
(9)
PVpot(t)=PR(t)RSDS(t)RSDSSTC
(10)
PR(t)=1+γ[Tcell(t)TSTC]
(11)
Tcell(t)=c1+c2TAS(t)+c3RSDS(t)+c4VWS(t)
(12)

where PVpot(t) is the PV power generation potential of the PV plant at time t, PR(t) is the performance ratio, encapsulating the effects of temperature on the efficiency of PV cells, RSDS(t) is the surface-downwelling shortwave irradiance at time t, RSDSSTC is the irradiance under standard test conditions (1,000 W m−2), Tcell(t) is the temperature of the PV cell at time t, TSTC is the temperature under standard test conditions (25 °C), TAS(t) is the surface air temperature at time t and VWS(t) is the surface wind velocity at time t. The variables γ, c1, c2, c3 and c4 are PV panel type-specific factors sourced from the existing literature57,72.

The hourly data for TAS, RSDS and VWS were acquired from the ERA5-Land dataset, which is a widely used reanalysis dataset produced by the European Centre for Medium-Range Weather Forecasts with a spatial resolution of approximately 11 km (ref. 73). The hourly power output for each USPV plant, spanning from 1991 to 2020 for each type of PV panel, was calculated utilizing equation (9), and the market shares of the different PV panel types were used to compute a weighted average power output. This output was then aggregated to reflect the total power generated over the plant’s operational lifespan. Moreover, a degradation rate of 0.7% per year was incorporated into the power output calculations across the 30-year lifespan of the USPV plant74.

Finally, the C footprint of a USPV plant, denoted as Fc, was calculated as

Fc=Ep+EBOS+EecoPout
(13)
Eeco=3.67×Ieco,
(14)

where Eeco is the emission from alterations in C pool induced by USPV deployment. The coefficient of −3.67 converts changes in C pool into equivalent releases or sequestration of CO2.

Designing land management strategies

Four hypothetical scenarios were designed to alter the current land management strategies of the existing global USPV plants. These scenarios aimed to explore the potential impacts of different land management strategies on the C pool of the hosting ecosystem and, subsequently, on the C footprint of these USPV plants. The first (all croplands postconstruction) scenario (S1) assumes that the grounds of all these USPV plants are managed as cropland. The second (all grasslands postconstruction) scenario (S2) assumes that all these USPV plants manage their grounds as grassland. The third (optimal) scenario (S3) assumes that all these USPV plants manage their grounds with land-cover types optimized for the highest C density potential based on local environmental conditions. The fourth (worst case) scenario (S4) assumes that the grounds of all these USPV plants are managed as bare land.

Analysing the impact of microclimate changes

Given that USPV deployment can result in microclimate changes but with large uncertainties24,41,42,43, we performed a sensitivity analysis to reveal the potential impact of USPV-induced microclimate changes on our results. The sensitivity analysis comprised two components: an albedo-based analysis and a whole scene assessment. For the albedo-based analysis, we selected surface air temperature as a proxy for microclimate impact estimation, because temperature was proved to be most affected by USPV construction attributed to effective albedo change (reflectivity of PV panel plus solar conversion efficiency75)45,46. In addition, other microclimate impacts, such as reduced evaporation caused by the PV panels, could also be partially reflected through changes in temperature. A total of four scenarios were set, including ±0.5, ±1, ±1.5 and ±2 °C after construction, of which the direction of temperature change was determined by the direction of change in the effective albedo. The effective albedo of the USPV area was deemed to decrease for USPV plants sited on bare land, while the opposite is true for those sited on the area with the other land-cover types76. The decrease in effective albedo will lead to an increase in surface temperature because more energy will be absorbed by the ground, while the increase in effective albedo will result in a cooling effect. Then, the C density of the hosting ecosystem of each USPV plant after construction was estimated leveraging the extrapolation method mentioned before based on the four scenarios, and subsequently, C pool changes, the C footprint and the contribution of C pool change to the C footprint were calculated. Given the complexity of the microclimate impacts of USPV plants, which affect not only temperature but also other meteorological variables, particularly precipitation, we conducted a whole scene assessment. This assessment considered the effects of changes in both temperature and precipitation, as well as their combined impacts. Specifically, we set up four temperature change scenarios (±0.5, ±1, ±1.5 and ±2 °C) and four precipitation change scenarios (±20%, ±30%, ±40% and ±50%). Unlike the albedo-based analysis, the whole scene assessment did not constrain the direction of temperature and precipitation changes, aiming to provide a comprehensive understanding of the potential influences of these changes on our results, even though some scenarios may not occur in reality.