Solar panel + green roof trial
A joint study by BCA, NParks and NUS found that photovoltaic panels installed with a green roof produce an average of 1.3% more electricity in open air conditions because they run cooler, and the roof itself cools, reducing the building's cooling needs.
SCOPE OF THE STUDYBetween November 2021 and October 2022, four different setups were compared on the roof of Alexandra Primary School in Bukit Merah:
Bare concrete roof
Green roof alone
Solar panels alone
Solar panel + green roof combination
The findings were published in June in the journal Applied Energy.
COOL PANELS, HIGH EFFICIENCYPanels integrated with a green roof produced more electricity than systems installed solely on the concrete surface. The research team notes that moisture released from plant leaves and soil cools the panels through evaporation and transpiration, limiting heat-related efficiency loss. In outdoor tests, the average production increase was 1.3%.
LESS COOLING LOADA green roof reduces air conditioning consumption by lowering roof surface and ceiling temperatures. This increases electricity production and saves energy on the consumer side.
CITY-SCALE POTENTIALIf Singapore's existing 1,640 MW of photovoltaic capacity were to be deployed on green roofs, it is estimated that an additional 3.4 GWh could be generated annually – equivalent to the annual electricity consumption of approximately 7,400 HDB flats.
BIODIVERSITYFive shade-tolerant species were tested, with Pilea depressa showing the best growth. Plants growing in the shade of the panels covered approximately 20% more area compared to those installed with green roofs alone. Observed insect and disease problems did not significantly impact growth. The researchers emphasize that this approach could also support urban biodiversity.
EXPERT OPINIONSAssoc. Prof. Stephen Tay (NUS): “The common belief that plants cannot thrive in shade is challenged by these results; PV + green roof support each other.”
Poh Choon Hock (NParks): “Plants adapt to new environments over time; added value to the urban ecosystem is possible.”
Selvam Valliappan (BCA): “This is a true win-win: it increases urban greenery while also contributing to building owners’ net-zero goals.”
MESSAGE FOR POLICY AND PLANNINGThe team emphasizes that policies and zoning guidelines in tropical cities could be updated to encourage such hybrid roof solutions, and that scalable pilots in public buildings and residential blocks would yield rapid results.
Source: Headline News
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