High resolution global spatiotemporal assessment of rooftop solar photovoltaics potential for renewable electricity generation

ARTICLE https://doi.org/10.1038/s41467-021-25720-2 OPEN High resolution global spatiotemporal assessment of rooftop solar photovoltaics potential for renewable electricity generation 1234567890():,; Siddharth Joshi 1,2,3 ✉, Shivika Mittal4, Paul Holloway Brian Ó Gallachóir 1,2,3 & James Glynn 1,2,3,7 2,5, Priyadarshi Ramprasad Shukla6, Rooftop solar photovoltaics currently account for 40% of the global solar photovoltaics installed capacity and one-fourth of the total renewable capacity additions in 2018. Yet, only limited information is available on its global potential and associated costs at a high spatiotemporal resolution. Here, we present a high-resolution global assessment of rooftop solar photovoltaics potential using big data, machine learning and geospatial analysis. We analyse 130 million km2 of global land surface area to demarcate 0.2 million km2 of rooftop area, which together represent 27 PWh yr−1 of electricity generation potential for costs between 40–280 $ MWh−1. Out of this, 10 PWh yr−1 can be realised below 100 $ MWh−1. The global potential is predominantly spread between Asia (47%), North America (20%) and Europe (13%). The cost of attaining the potential is lowest in India (66 $ MWh−1) and China (68 $ MWh−1), with USA (238 $ MWh−1) and UK (251 $ MWh−1) representing some of the costliest countries. 1 SFI MaREI Centre for Energy Climate and Marine, Cork, Ireland. 2 Environmental Research Institute, University College Cork, Cork, Ireland. 3 School of Engineering, University College Cork, Cork, Ireland. 4 Grantham Institute–Climate Change and the Environment, Imperial College London, London, United Kingdom. 5 Department of Geography, University College Cork, Cork, Ireland. 6 Global Centre for Environment and Energy, Ahmedabad University, Ahmedabad, India. 7 Center on Global Energy Policy, Columbia University, New York, USA. ✉email: NATURE COMMUNICATIONS | (2021)12:5738 | https://doi.org/10.1038/s41467-021-25720-2 | www.nature.com/naturecommunications 1 ARTICLE F NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-25720-2 rom powering the National Aeronautics and Space Administration (NASA’s) Vanguard satellites in 1958 to lighting homes in sub-Saharan Africa, solar photovoltaics (PV) technology has come a long way. Rooftop Solar photovoltaics (RTSPV) technology as a subset of the solar photovoltaic electricity generation portfolio can be deployed as a decentralized system either by individual homeowners or by large industrial and commercial complexes. Over the past decade, reduction in the deployment cost coupled with policy-driven initiatives has led to a rapid uptake of RTSPV globally. Between 2006 and 2018, the installed capacity of the RTSPV has grown from 2.5 GW to 213 GW- an 85-fold increase globally1. With an additional capacity installation of 41 GW, RTSPV currently accounts for 40% of the global cumulative installed capacity of the solar PV and nearly one-fourth of the total renewable capacity additions in 2018— surpassing the combined new installed capacities of both coal and nuclear. At the same time, RTSPV technology has demonstrated a steep decline in its deployment costs which ranged between 63 and 265 $ MWh−1 in the year 2019—a reduction of between 42 and 79% over 2010 values2. Globally, nearly 800 million people were without electricity in 2018, the majority of who are living in rural areas3. Here, the role of decentralized rooftop PV in advancing the ethos of the Sustainable Development Goal (SDG) 7 becomes very important. The fast installation time and low levelised cost of RTSPV can aid in mitigating the problem of energy access by making citizens or communities a prosumer. The prosumer can generate and consume electricity as per their requirements without depending exclusively on a centralized grid infrastructure. As the fastest deployable energy generation technology with the highest yearon-year growth rate4, solar PV technology is projected to supply 25–49% of the global electricity needs by 2050 while providing employment for up to 15 million people between 2018 and 20505. Out of this, RTSPV deployment will contribute up to 40% of the total solar PV-derived electricity generation by 2050. Increased deployment of RTSPV can support displacing fossil fuels out of the current energy generation mix as can be observed in the successful implementation of rooftop photovoltaics in Germany. As the demand for electricity as an energy source increases in the future, RSTPV based generation sources will form a large part of the future renewable-based generation portfolio. This shift in the current generation mix coupled with the future low carbon generation capacity expansion can aid in reducing the energy-derived greenhouse gas emissions and also aid in advancing the SDG13 goal of combating climate change with cobenefits for the SDG3. RTSPV technology can thus lead to consumer-driven breakthroughs in tackling climate change, reducing local air pollution, accelerating development, and providing affordable energy access to areas lacking electrification. To better understand the role that an RTSPV system can fulfill in the future, a global harmonized geo-mapped assessment of its technical potential and the costs associated with attaining the technical potential is pertinent especially when such assessments at a global level are lacking. RTSPV systems are deployed as a decentralized system contrary to the utility-scale solar PV systems, which increases the complexity of its assessment as the smallest unit of deployment becomes a rooftop as opposed to a large plot of a green or brownfield site. Along with the complexities associated with accurately determining the rooftop area, assessment of seasonal variations of its potential is also important to understand the supply dynamics of variable renewable energy (VRE) technologies like RTSPV. This highlights the need for a high-resolution spatiotemporal assessment that accurately represents the geographical variability of the built environment along with impacts of seasonal changes in solar insolation. 2 Current research primarily focuses on utility-scale solar PV resource assessment at a global scale. A similar assessment has not been done for decentralized RTSPV at a scale greater than regional/national levels6–9. As a result, energy system models and research informing climate change policy have not fully considered the role of solar PV in meeting the climate change mitigation goals10. Assessment of RTSPV potential requires an underlying dataset of building footprints, solar insolation mapping, and technology-specific information like panel size, conversion efficiency, and system losses. The current literature is adequate in providing global information on the latter two categories, with the largest inaccuracies11 attributed to the demarcation and calculation of building footprints which require large data and costly information processing hardware to extract buildings from satelli (...truncated)