Interplay Between Rooftop Solar Photovoltaics and the Urban Thermal Environment: A Case Study of Lucknow, India

Abstract

Rapid urbanization in Indian cities has intensified Urban Heat Island (UHI) effects, increased surface temperatures and placing additional stress on urban energy systems. While rooftop solar photovoltaic (PV) installations are primarily deployed for renewable energy generation, they also influence urban thermal behavior by modifying radiative exchange processes, surface albedo, and roof shading. Focusing on Lucknow, a rapidly expanding city in northern India, this study investigates the interplay between rooftop solar deployment and the urban thermal environment within dense built-up areas using satellite-derived Land Surface Temperature (LST) data. Multi-temporal Landsat imagery for 2019 and 2023 was processed in a GIS framework to analyze spatial patterns of LST, ?LST, and the distribution of urban heat and cool zones. Results indicate a reduction in peak surface temperature from 39.7 °C in 2019 to 34.6 °C in 2023, with pronounced cooling observed in environmentally buffered zones such as the Gomti River corridor, Kukrail Reserve, and Cantonment area. During the same period, solar-covered rooftop area expanded by approximately 131%, increasing from 170,472.20 m² to 393,974.23 m². Spatial correlation analysis shows that wards with higher rooftop solar density tend to exhibit comparatively lower LST values, suggesting localized thermal moderation associated with PV installations through shading and reduced heat absorption. In addition to thermal implications, the growth in solar generation from 58.24 GWh to 132.75 GWh annually corresponds to an estimated avoidance of about 93,487 tCO? yr?¹, equivalent to roughly 93,000 carbon credits under India’s Carbon Credit Trading Scheme. The findings highlight rooftop solar photovoltaics as a dual-benefit strategy contributing to both urban heat mitigation and low-carbon energy transition. This study provides empirical evidence for integrating distributed solar infrastructure into climate-sensitive urban planning, offering actionable insights for developing thermally resilient and sustainable cities in rapidly urbanizing regions.

Introduction

This study examines how rapid urbanization in Indian cities, particularly Lucknow, has intensified the Urban Heat Island (UHI) effect and how rooftop solar photovoltaic (PV) systems influence urban temperatures. While solar panels are mainly used for energy production, they also affect surface temperature by changing heat absorption, shading rooftops, and altering surface reflectivity.

Using Landsat satellite data from 2019 and 2023, the study analyzes changes in Land Surface Temperature (LST) across urban areas. Results show a significant decrease in peak surface temperature from 39.7°C to 34.6°C, with stronger cooling in greener or environmentally protected zones like the Gomti River corridor, Kukrail Reserve, and Cantonment area.

During the same period, rooftop solar coverage increased by about 131%, from 170,472 m² to 393,974 m². Areas with higher solar panel density generally showed lower surface temperatures, indicating that rooftop solar installations contribute to localized cooling through shading and reduced heat absorption.

Additionally, solar energy generation increased from 58.24 GWh to 132.75 GWh, leading to an estimated reduction of about 93,487 tons of CO? per year, equivalent to roughly 93,000 carbon credits under India’s carbon trading system.

Conclusion

This study used satellite-derived thermal datasets (Landsat 8 OLI/TIRS) and geospatial analysis in ArcGIS 10.8 to thoroughly assess the association between LST and rooftop solar photovoltaic (RSPV) adoption in Lucknow city from 2019 to 2023. There was an apparent decline in surface temperature throughout the urban fabric, with the maximum LST falling from 39.7°C in 2019 to 34.6°C in 2023, suggesting a slow but discernible urban cooling trend. The analysis of rooftop solar expansion shows that the total solar panel area rose by more than 131%, from 170,472.20 m² in 2019 to 393,974.23 m² in 2023. This translates to an increase from around 102,917 panels to approximately 218,882 panels, assuming an average solar module size of 1.8 m² per panel as reported by the International Energy Agency (International Energy Agency, 2021a) and the National Renewable Energy Laboratory (National Renewable Energy Laboratory, 2022). This growth decodes into an increase in clean energy output from 58.24 GWh to132.75 GWh annually, mitigating about 93,487 tonnes of CO2 emissions annually, or 93,000 carbon credits under the Government of India\'s Carbon Credit Trading Scheme (Government of India, 2023) . The dual environmental role of photovoltaic (PV) systems is demonstrated by the regional association between lower LST values and rooftop solar density: thermal mitigation by lowering rooftop heat absorption and providing shade; and decrease of carbon emissions by replacing grid power derived from fossil fuels. Lucknow city 39potential to reduce carbon emissions increased in tandem with the growth in solar energy output. The carbon offset increased from 41,635 tCO?/year in 2019 to 93,487 tCO?/year in 2023 based on the Central Electricity Authority\'s (Central Electricity Authority, 2023)emission factor of 0.708 tCO?/MWh. This is equivalent to 93,487 carbon credits that may be monetized under India\'s Carbon Credit Trading Scheme (CCTS, 2023). These numbers highlight rooftop solar expansion\'s combined environmental advantages of reduced grid dependency while decreasing localized heat accumulation. PV systems boost microclimatic cooling through energy conversion, shading, and decreased heat storage on built-up surfaces, as established by spatial overlay analysis, which showed that locations with higher rooftop solar density showed comparatively lower mean LST values. On the other hand, thermally persistent areas like Balaganj, Faizullaganj, and Charbagh still have high surface temperatures, which highlights the need to expand the use of solar panels, reflective roofs, and green spaces in busy commercial regions. According to the ?LST map, Lucknow\'s cooling impacts are spatially diverse, with the southern and southwest regions of the city seeing the strongest cooling. Wards in the vicinity of Alambagh, Charbagh periphery zones, Sarojini Nagar, Raja Bijli Pasi, and residential areas near the airport show moderate to high cooling, with ?LST values between ?3.54 °C and ?2.54 °C, and in isolated pockets reaching ? ?4.5 °C (very strong cooling). Clustered rooftop solar arrays and relatively lower building densities, which improve shading and decrease surface heat storage, are characteristics of these places. Overall, the research suggests convincing evidence that rooftop solar adoption serves as an approach for both adaptation and mitigation of climate change, concurrently reducing urban heat and offsetting carbon emissions. Sustainable Development Goals SDG 9 (Affordable and Clean Energy), SDG 11 (Sustainable Cities and Communities), and SDG 13 (Climate Action) are all in line with these research results. Lucknow serves as an example for mid-sized Indian city that want to move toward carbon-neutral, thermally resilient urban systems by encouraging targeted renewable energy. In order promote data-driven urban planning, climate-sensitive design, and low-carbon growth paths for the future, the approach that was created for Lucknow can be used to other Indian metropolitan areas

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Copyright © 2026 Sushil Chandra, Fariha Fatima, Ali Niazi, Sahab Deen. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.