Smarter, Cooler, Greener: The Promises and Paradoxes of Solar-Powered Cities

 

By Mariana Meneses

A recent study by Yuekuan Zhou and Jiangyang Liu, researchers at the Hong Kong University of Science and Technology, explores how emerging digital technologies are helping cities become more energy-efficient and sustainable. Published in the peer-reviewed journal Energy and Buildings, the research focuses on tools like artificial intelligence (AI), smart sensors, digital twins, and blockchain to improve how urban infrastructure uses energy, especially in buildings, which are among the largest contributors to carbon emissions.

These technologies are making buildings “smarter” by enabling systems to adapt in real time. AI, for example, can forecast a building’s energy use and automatically adjust heating or cooling to optimize efficiency. Digital twins, which are virtual replicas of physical structures, allow engineers to test improvements and monitor energy performance more effectively. In real-world applications, such innovations have cut electricity use by as much as 79%.

The study also highlights how cities can coordinate diverse energy sources, including solar panels, batteries, and hydrogen systems, through “multi-agent energy management.” Instead of depending on a single centralized grid, independent systems communicate and collaborate to reduce consumption and manage supply more efficiently. This distributed approach has helped lower energy peaks and extend battery life by minimizing unnecessary use.

Furthermore, the researchers underscore the importance of flexibility and resilience in the face of climate change. As extreme weather events become more frequent, digital systems can quickly adapt to shifting demands or disruptions. Whether during a heatwave or blackout, these technologies help keep essential services running.

 

 

Cooling the City: Strategies That Reflect, Absorb, or Backfire

In the search for cooler, more livable cities, not all solutions are equally effective, while some can even backfire. A research letter published in the journal Advancing Earth and Space Sciences in 2024 by researchers from the UK, the Netherlands, Spain and Finland, led by University College London’s O. Brousse, used advanced climate modeling to test how different urban cooling strategies performed during two of the hottest days in London’s recent history.

The researchers tested nine common interventions across the Greater London area, including cool roofs, green roofs, rooftop solar panels, street-level vegetation, and air conditioning. Among all strategies, cool roofs – which reflect more sunlight by employing techniques like light color pigments and special materials – were the most effective, reducing outdoor temperatures by about 1.2°C on average and up to 2°C in some locations. In contrast, green roofs that are covered with vegetation to absorb solar energy had minimal overall impact, only offering some daytime cooling. Solar panels provided moderate benefits.

 

The study also examined how these interventions affected the surface energy balance, which helps explain why temperatures change.

Cool roofs worked mainly by reflecting more sunlight and reducing the heat absorbed and released by buildings. Green roofs cooled the city during the day but stored heat that was released at night, which sometimes made nighttime temperatures warmer. Solar panels reduced heat absorption by converting sunlight into electricity, especially helping to cool the city in the late afternoon and evening. Importantly, while solar panels could produce enough energy to power air conditioning, they wouldn’t prevent the warming effect that AC systems have on the surrounding air unless used strategically.

Although the research focused only on two days and has some limitations, such as not testing newer technologies or long-term consequences, the results highlight key insights for urban planning. The authors stress the importance of combining different strategies, considering local building types and conditions, and continuing research to inform decisions that can make cities more resilient to extreme heat.

Solar Heat Dilemma: When Clean Energy Warms the Air

While the London study highlighted the moderate cooling potential of solar panels, new research suggests that their large-scale deployment may come with unintended consequences.

Researchers from India, US, China and Australia, led by University of Calcutta’s Ansar Khan, published a study in the journal Nature Cities in 2024 in which they examine how large-scale installation of rooftop photovoltaic solar panels (RPVSPs) can affect city temperatures.

 

 

While these panels are a valuable source of renewable energy, they can also unintentionally raise daytime temperatures.

In Kolkata, for example, simulations show that RPVSPs could increase daytime temperatures by up to 1.5 °C while slightly lowering nighttime temperatures by around 0.6 °C. The warming happens because the panels absorb sunlight, generate heat, and enhance airflow that transfers this heat to the surrounding air. These effects are not unique to Kolkata, as similar patterns were observed in Sydney, Athens, Austin, and Brussels, highlighting that solar panels can reshape urban climates depending on location and design.

Unlike many earlier studies that focused only on individual buildings or used simplified models, this research used an advanced weather modeling system to simulate RPVSP effects on temperatures at a city-wide scale. The model included factors often overlooked in past research, such as the heat transfer between the panels and the roof beneath them. This revealed that the panels act as two heat sources (top and bottom), leading to stronger heat release during the day. While some previous studies showed cooling effects from solar panels, this study emphasizes that in hot and humid environments, the warming effect may dominate unless improvements are made to panel design and placement.

The authors argue that better understanding these thermal side effects is essential for urban planning and climate adaptation. While solar panels reduce dependence on fossil fuels and help power cooling systems like air conditioners, they also lower their own efficiency as temperatures rise. The study suggests that future policies should balance the benefits of clean energy with potential urban heating risks. It also calls for advancing solar panel technologies and combining them with smarter cooling strategies to avoid trading one environmental problem for another.

 

 

Innovation Spotlight: The Quest for More Efficient Energy Systems

In 2024 TQR published an article on solar energy technology, which is advancing rapidly with new materials like perovskite that are poised to surpass the efficiency limits of traditional silicon-based solar cells.

While silicon still dominates the market and powers about 4.5% of global electricity, researchers at Oxford and in South Korea are achieving record efficiencies with ultra-thin, flexible perovskite layers and quantum dots. These innovations could double current efficiency levels and make solar viable on more surfaces—from rooftops to backpacks—though challenges remain with durability and large-scale production. As massive solar farms expand worldwide, concerns grow over their environmental impact and worker safety, highlighting the need for more compact, efficient systems. Looking ahead, the integration of solar power into hydrogen fuel production offers a promising path toward cleaner energy and a reduced reliance on fossil fuels.

Still, even the most advanced technologies face roadblocks without the right policy and infrastructure, especially in regions with pressing energy needs.

 

 

Case Study: Solar Potential in Nigeria’s Cloudy Southeast

Published in 2024 in the  journal Sustainable Energy Research by researchers led by Samuel Ikemba, from the Nigeria Atomic Energy Commission, a study investigates the solar energy potential of five southeastern Nigerian cities using a Long Short-Term Memory (LSTM) neural network for machine learning. Despite frequent cloud cover and extended rainy seasons, these cities were found to hold strong potential for solar power generation. By analyzing two years of hourly weather data from NASA and training the model on real-time data from a solar plant in Ulsan, South Korea, researchers achieved highly accurate solar energy forecasts.

These results support prioritizing solar infrastructure investment in the areas researched, and the study is grounded in the wider context of Nigeria’s chronic power supply issues. While fossil fuels dominate the country’s energy mix, growing concerns about climate change and energy access have fueled interest in renewables, especially solar. However, efforts have been hampered by outdated infrastructure, regulatory barriers, and underinvestment. The research highlights the importance of combining technical innovation, like machine learning for accurate forecasting, with supportive policy and private-sector incentives to tap into renewable resources.

The Waste We Don’t See: Solar’s Looming Afterlife

As cities and countries scale up solar power, another challenge is beginning to surface: what happens when solar panels reach the end of their lifespan?

Researchers from Egypt, led by the American University in Cairo’s Yasmin R. Maghraby, published a review article in the journal Solar Energy in 2025 that addresses an emerging sustainability challenge: what to do with the massive wave of end-of-life (EOL) solar panels expected in the coming decades?

Although solar photovoltaic (PV) panels are a clean source of energy, they typically last 20–30 years and contain both valuable and hazardous materials. With early solar installations now reaching their expiration, global PV waste is projected to reach up to 78 million tons by 2050. The authors emphasize that improper disposal poses environmental and health risks due to toxic elements like lead, cadmium, and tin. At the same time, effective recycling could help reduce the production costs of new panels and lower the energy demand tied to silicon manufacturing.

 

 

The paper also reviews several existing recycling methods (for example, chemical, physical, thermal, and hybrid) used to recover materials from old panels.

However, the authors point out that these technologies are still limited by high costs, low recovery efficiency, and lack of scalability. A major barrier is the global shortage of dedicated recycling plants, meaning that in most places EOL panels are not being properly dismantled or repurposed. This presents both a technological and policy gap in the solar industry.

To move toward more sustainable solar energy systems, the paper calls for stronger regulations and expanded recycling infrastructure. Some countries, particularly in the European Union, have introduced producer responsibility laws and recycling fee requirements for PV manufacturers. Still, many regions remain in the early stages of addressing this issue. The authors argue that well-designed policies, investment in recovery technologies, and mandatory data reporting from solar manufacturers are crucial steps to ensure that the environmental benefits of solar energy are not undermined by growing volumes of poorly managed waste.

 

 

Building Smarter, Cleaner, and More Circular Cities

As the global push for sustainable energy accelerates, the promise of solar power is both bright and complicated. Innovations in efficiency and smart infrastructure are making cities more adaptive and intelligent, but as the evidence shows, even green technologies can generate new challenges from urban overheating to long-term waste.

If the goal is truly sustainable development, then cities must embrace not only cleaner energy systems but also smarter planning and circular design. That means looking beyond installation toward integration, maintenance, and afterlife. The future of solar energy won’t be defined solely by how much we can generate, but by how thoughtfully we manage its full lifecycle.

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