GREEN ROOFS could help improve SOLAR PANEL efficiency
There’s been a movement in architecture over the past couple of decades to help tie together large urban developments with plant life and greenery. We’ve seen a few buildings, and hundreds a lot more renders, of tall skyscrapers and large buildings covered in vegetation.
The aesthetic is often a beautiful one, but the idea is done as much for its tangible benefits as for the sheer visual glory. Naturally, there’s the evident improve from plants converting carbon dioxide into delicious, life-giving oxygen. However, greenery on the roofs of buildings could also help improve the output of solar installations, according to a recent study from Sydney, Australia.
The solar installation on top of Daramu House, Sydney, complete with greenery on the roof. Source: UTS Report
The study was led by Dr Peter Irga of the university of technology Sydney, with a report published for the City of Sydney. The opportunity for the study came about precipitously, thanks to two similar office buildings located side by side in downtown Sydney. Each building had a photovoltaic solar system installed on the roofing to generate electricity. On one building, plenty of plants were placed on the roofing and around the solar panels, while the other building was left bare.
Over an eight month period, the roofing loaded with greenery was 3.6% a lot more efficient than the bare roofing over the course of the experiment. The difference between the two was as much as 20% at height generating times. This led to the green roofing netting 69 MWh of electrical energy versus 59.5MWh for the bare roof. The extra 9.5 MWh generated over the period of the experiment is worth a full $2595 at local market rates.
The crucial to the difference in performance came down to temperature. Solar panels don’t work as well at higher temperatures, with Irga noting that “Temperatures above 25 degrees make photovoltaic panels less efficient.” This can be problematic in a place like Australia, where sunlight is abundant in the summer months but daily temperatures routinely span from 30 to 45 degrees Celsius.
A graph showing the difference in performance between the solar installations on the two buildings. Arrows A, B and C point to areas where urban shading caused a discrepancy.However, note the large improve the green roofing variety receives at height times. The cooling effect is a lot of crucial during full sun conditions when temperatures are highest.Source: UTS Report
Green roofs cool buildings through a process called evaportranspiration, or a lot more accurately, the twin processes of evaporation and transpiration. Water from the soil and other rooftop surfaces is evaporated, minimizing heat in the air. Additionally, small holes in the plants of the green roof, called stomata, are essentially the pores with which the plant exchanges gases with its surroundings. The plants lose water through these stomata to the atmosphere, additionally adding to the cooling process. Ideally, the huge majority of this water comes from rainfall, avoiding irrigation costs that can spoil the efficiency and environmental benefits of the roofing as a whole.
Reportedly, temperatures were on the buy of 20°C lower on the green roofing compared to the otherwise identical bare-roofed office building. This is a exceptional figure, and one that speaks with the quality of the green roofing design in the experiment. This comes down to careful selection of the ideal plant species, which are able to survive and prosper on the roofing while also supplying good cooling performance.
Thus, this significant temperature drop allowed the solar panels to remain in a much a lot more efficient operating range, leading to that 3.6% efficiency gain. This figure was figured out under simulated lighting conditions, in buy to eliminate differences in the urban environment around the two buildings from spoiling the result. It may not sound like much, but huge amounts of money are spent annually researching for single-point percentage gains in solar panel efficiency. In comparison, supplying a cheap natural cooling option can have a remarkably outsized effect.
Rooftop solar installations and green roofs alike need to be created very carefully to deal with shading from surrounding buildings. This can impact the amount of power that can be generated, as well as require the use of proper plant species for the amount of sun available.
The green roofing supplies other benefits, too. The study reported that the roofing absorbed nearly 9 tonnes of greenhouse gases throughout the experiment, and minimized storm water outflows substantially as well. The plants were also much appreciated by the local wildlife. The team noted that insects and birds swiftly flocked to the greenery. even predator species were identified up on top of the building, something that was unusual to see on a tower in the central service district of Sydney.
Overall, it’s a project that demonstrates a lot of net benefits. Additionally, it needn’t only be limited to green roofs. other solar installations could benefit from co-located greenery which naturally cools its surroundings and leads to better solar variety performance. expect a lot more research in this area, particularly in a localized fashion. green roofs and similar technologies are highly dependent on local climatic conditions, and often need to be created to work with the local flora and fauna as well. For those that dive in, it appears there are significant gains to be had!