In today’s class, we learnt about the Urban Heat Island (UHI) effect. Personally, I’m quite surprised how big a difference urban forms can have on surface and atmospheric temperatures. Dr Coleman mentioned that in some cities, the difference between surface and atmospheric temperatures can go up to 20 to 50 degrees!
In view of these, I wonder how the use of solar panels contribute to UHI. The Singapore government is pushing for increased utilization of solar energy, and by 2020, the goal is for solar panels to be installed at 5,500 HDB blocks – more than half of all blocks here! Knowing that these many buildings in Singapore will have their rooftops fitted with solar panels, I thought it would be interesting to know how these things differ in absorbing heat, compared to our usual rooftops.
The albedo – or reflection coefficient – of the earth is about 0.30 (on average). That means, 30% of light hitting the earth is reflected into space. Apparently, solar panels also fall into this range. On the other hand, the value for new concrete is about 0.5, while that for asphalt ranges from 0.04 to 0.12. Since many rooftops are composed of concrete, it seems that based on albedo values alone, solar panels do not seem that promising…
However, other than the albedo, other factors that are involved include the reduced absorption of heat by the building, due to the buffer space created by the solar panels. These help reduce air-conditioning energy consumption, which accounts for around 50-70% of our energy needs in our hot climate. And of course, don’t forget that solar panels themselves are also a source of clean energy! Numerous studies have also pointed out the benefits of solar panels on reducing global warming and UHI (links below).
In conclusion, in addition to methods such as urban greening, solar panels may be a possible way to reduce UHI in cities. In fact, solar cooling technology has been developed and is currently being tested at the United World College (UWC) in Singapore. This is the first and only school that uses renewable solar energy to run both the air-conditioning and hot water system using a hybrid system. This development will be an interesting one to watch. Find out more about it here.