An international group of scientists has created a new model for the assessment of rooftop photovoltaic solar panels (RPVSPs) in urban microclimates.
The module utilizes the latest weather research and forecasting (WRF) model, integrating the building energy model (BEM) and the building effect parameterization (BEP) into it. The model was validated against ten observation stations in Kolkata, India, using experimentally validated models.
“While existing literature reports on the impact of RPVSP on the urban environment, most are based on in situ field experiments or building-scale simulations, lacking a comprehensive multicity-scale analysis. These studies also neglect convective heat transfer between the roof surface and the back of solar panels,” said the academics. “Our study addresses these gaps by incorporating new parameterizations for RPVSPs, including convective heat transfer, resulting in more aligned results with other studies incorporating similar considerations.”
The combined approach, named the WRF/BEP + BEM model, can calculate heat exchange, momentum, humidity, and turbulent kinetic energy flux between buildings and the outdoor environment under stable atmospheric conditions. It was initially tested in the Indian city of Kolkata and then validated in Sydney, Australia; Austin, Texas, USA; Athens, Greece; and Brussels, Belgium, to ensure that the findings are not limited to a specific climatic zone.
“Five experiments were conducted to assess the regional impact of extensive RPVSPs deployment during the current heatwave month in Kolkata. The control simulation used a roof albedo of 0.15 and no RPVSPs,” the group explained. “The experiments explored RPVSPs scenarios with coverage fractions of 0.25, 0.50, 0.75, and 1.0 on city rooftops. Standard RPVSP parameters, including albedo, conversion efficiency, and emissivity, were set to 0.11, 0.19, and 0.95, respectively.”
According to the data collected in Kolkata, RPVSPs can increase daytime near-surface air temperatures by up to 1.5 C, as they absorb approximately 90% of solar energy, converting up to approximately 20% of it into electricity, while the remainder contributes to their warming. At nighttime, on the other hand, full city PV coverage can reduce nighttime maximum near-surface air temperatures by up to 0.6 C. In peak heat hours, the roof surface temperature would rise by up to 3.2 C and have an average cooling of 1.4 at night.
The near-surface air temperatures were similar across the board. Sydney experienced a 0.8 C cooling at night and a 1.9 C rise during the day; Austin showed a cooling of 0.7 C and a rise of 1.8 C, while Athens had 0.4 C and 1.2 C, respectively. Brussels's results showed a night cooling of 0.3 C and a day rise of 1.1 C.
“Our study also reveals that rooftop photovoltaic solar panels significantly alter urban surface energy budgets, near-surface meteorological fields, urban boundary layer dynamics, and sea breeze circulations,” the group added. “Elevated urban temperatures due to RPVSPs installation enhance lower atmospheric mixing and raise the planetary boundary layer (PBL) height by up to 615.6 m, reducing ground-level pollution.” PBL represents the lowest part of the atmosphere, which is directly influenced by the Earth's surface.
The findings were presented in the study “Rooftop photovoltaic solar panels warm up and cool down cities,” published in Nature Cities. The research was conducted by Researchers from India's University of Calcutta, the Indian Institute of Technology Kharagpur, Jadavpur University, the USA's Massachusetts Institute of Technology (MIT), the University of Texas at Austin, China's Chinese Academy of Sciences, and Australia's University of New South Wales.
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Your theory is wrong. Pv panel convert dun light heat to current and use in building or home. As per thermodynsmic law one energy convert to electric energy and it balance total energy. It means pv panels actually absorb heat and produce electric current.
Your story is incorrect.
I agree with Muhammad tahir
Ok so the panel absorbs 90 % and 20% is bled off as electricity leaving 70% in the panel. The question is how much is radiated back to space and how much is radiated down underneath the panel? Also for the future, could not a reflective layer built into the back of the panel enhance the amount that is radiated back to space?
I do sort of agree to you, Muhammad.
Just reading the article quickly, I totally and utterly agree with you! It sounds like either (a) a report generated by the oil and gas industry to do down alternative energy, or (b) someone in a university had to get something or other together to justify their position! I immediately thought ‘really?’ much the same as you.
It’s not clear from this reporting if these conclusions apply equally to all solar installations, regardless of the volume of air or the angle between the solar panels & the roof or pavement surface below. Many rooftop solar installations provide very little air space between the panels & the roofing surface below. Solar parking lot canopies provide a much, much larger separation between the panels & the pavement surface heat sink.
Waiting myself for the study showing that cooling the city back down at least 1.5°C by having similar area of IR emission white self-cleaning stuff in the area looks tacky just about any arrangement you try, and the rejoinders; Memphis camo is okay, and that human civilization was only ever a jagged heap of domes or whatever.
I don’t understand. In my Texas solar installation, on my roof, the panels decrease the roof surface temperature by +30°f in full summer sun. I have FLIR images showing this. The panels absorb a sizable portion of the IR wavelength, enough to make them immensely cooler than the surrounding fully exposed asphalt shingles. So how can they PRODUCE excess heat regardless of the space between panel and roof surface?
I have the same experience. I have panels on top of a flat concrete roof. On a hot sunny day I have felt the roof and can feel that the roof area under the panels is cooler than the area without the panels. The top of the panels may be hotter than the bare roof, but who cares.
Wrong perception
This story is completely wrong, the suns heat is absorbed and converted to heat eventialy no mater what is recivng it, there is some reflecting back from the glass, which reduces what effect you are trying to put forth, looks like anouther hit story from a oil paid hack.
A few points
Have solar on my metal roof and the metal roof now expands/pops much less, like never, compared to before. Much less heat is bleeding down into my attic and home so less electricity used.
How much heat is given off from a coal fired plant or nuclear plant in producing the same amount of electricity – also figure the heat given off by the locomotives hauling in the coal.
Basically the article should consider all factors from all sources of power generation rather than cherry pick.