A Green Roof or Rooftop Solar?
Sourced from The Conversation
Growing city populations and limited space are driving the adoption of green roofs and green walls covered with living plants. As well as boosting biodiversity, green roofs could play another unexpectedly valuable role by increasing the electricity output of solar panels.
As solar panels heat up beyond 25℃, their efficiency decreases markedly. Green roofs moderate rooftop temperatures. So we wanted to find out: could green roofs help with the problem of heat reducing the output of solar panels?
Our research compared a “biosolar” green roof – one that combines a solar system with a green roof – and a comparable conventional roof with an equivalent solar system. We measured the impacts on biodiversity and solar output, as well as how the plants coped with having panels installed above them.
The green roof supported much more biodiversity, as one might expect. By reducing average maximum temperatures by about 8℃, it increased solar generation by as much as 107% during peak periods. And while some plant species outperformed others, the vegetation flourished.
These results show we don’t have to choose between a green roof or a solar roof: we can combine the two and reap double the rewards.
How was the study done?
Many studies have tested a single rooftop divided into “green roof” and “non-green roof” sections to measure the differences caused by vegetation. A problem with such studies is “spatial confounding” – the effects of two nearby spaces influencing one another. So, for example, the cooler green roof section could moderate the temperature of the non-green section next to it.
In studies that use distinct buildings, the buildings might be too far apart or too different in construction to be comparable.
The two buildings in our study were the same height, size and shape and located next to each other in Sydney’s central business district. The only difference was Daramu House had a green roof and International House did not.
From the Living Architecture Monitor
