In the heart of Taipei’s urban sprawl, where concrete stretches as far as the eye can see, a quiet revolution is unfolding on the rooftops. Su Ying-Ming, a researcher at the Department of Architecture at National Taipei University of Technology, has been peering into an unexpected ally in the fight against the urban heat island effect: green roofs topped with solar panels. His findings, published in the *E3S Web of Conferences* (translated as the *Environment, Energy and Sustainability Web of Conferences*), could reshape how cities balance renewable energy goals with the need for cooler, more livable spaces.
For years, rooftop solar panels have been a symbol of progress in Taiwan’s push to meet its COP28 commitments—generating 27–30% of its energy from renewables by 2030, with half of that coming from solar. But as Su points out, these panels don’t just generate electricity; they also absorb heat, often exacerbating the very problem they’re meant to help solve. “Conventional PV panels can trap heat beneath them, raising the temperature of the roof surface and the air around them,” Su explains. “In a dense city like Taipei, that’s the last thing we need.”
Enter the shallow substrate green roof-integrated PV system. By layering a thin bed of vegetation beneath solar panels, Su’s team discovered that temperatures could be reduced by up to 1.5°C compared to conventional PV setups. The real game-changer, however, came when irrigation was introduced. Under those conditions, the system slashed temperatures by 4.2°C compared to bare concrete roofs—a 10.2% drop that could mean the difference between an oppressive rooftop and one that’s merely warm. The vegetation’s evapotranspiration, combined with the cooling effects of moisture, created a localized microclimate that not only kept the roof itself cooler but also accelerated the recovery of relative humidity in the afternoon, aiding in surface cooling.
The implications for the energy sector are significant. Cooler panels operate more efficiently, meaning higher energy output and longer lifespans for the systems. For urban planners and developers, the research suggests a dual-purpose solution: meet renewable energy targets while mitigating the urban heat island effect. “This isn’t just about slapping solar panels on a roof anymore,” Su says. “It’s about designing systems that work *with* the environment, not against it.”
The study, conducted on the rooftop of the Integrated Technology Complex Building at National Taipei University of Technology, measured air temperature and humidity over 17 days in October 2025. Three rooftop configurations were compared: green roof-integrated PV, conventional PV, and bare concrete. The results were clear—vegetation made a measurable difference. Heat accumulation beneath conventional PV panels was found to increase adjacent concrete temperatures by 4.3%, a finding that underscores the need for better thermal management in urban solar installations.
As cities worldwide grapple with the dual challenges of climate change and energy demand, Su’s research offers a practical, scalable solution. The shallow substrate green roof-integrated PV system isn’t just a niche experiment; it’s a blueprint for future urban design. And with Taiwan’s ambitious solar goals looming, innovations like these could be the key to making renewable energy not just viable, but *sustainable* in every sense of the word.