I would like to thank Forum contributor Leslie Lim for reinvigorating the discussion on whether solar panels are in fact counter-effective in reducing local warming (Installing rooftop solar panels may not result in much energy savings, April 24).
Most commercially available solar panels are between 15 per cent and 22 per cent efficient. The efficiency of solar panels degrades over time as they are exposed to the elements. High temperatures in tropical regions will cause more rapid degradation, partly because heat induces microscopic cracks that disrupt electricity flow.
A typical solar panel, assuming 15 per cent efficiency, produces about 900 watt-hour (Wh) of electricity per square metre per day. The actual output may vary from day to day, depending on weather conditions.
The same solar panel will absorb, on average, about 1,800Wh per square metre of heat energy from the sun per day. This means that it absorbs approximately twice the amount of heat energy that it produces in electricity.
This heat energy is mostly dissipated into the environment, giving rise to the urban heat island effect. In fact, it is not uncommon for solar cells to reach temperatures in excess of 70 deg C during periods of bright sunlight in Singapore.
When placed together in an array, solar panels behave like a huge man-made radiator. Studies done on solar farms in the desert found that they gave rise to new microclimatic conditions which were more extreme than the surrounding desert.
In the Singapore context, large solar installations have the potential to disrupt and exacerbate local weather patterns. This is especially so as we are an island nation.
Water covers a large portion of Singapore's geographical surface, and it can also absorb large amounts of energy from the sun. This tremendous ability to store and release heat over long periods of time gives our lakes, reservoirs, rivers and surrounding seas a central role in stabilising the climate system.
By blocking sunlight from entering the water, a floating solar farm effectively negates the role of a body of water to act as a natural climate stabiliser.
Before Singapore fully executes its plan to quadruple solar energy use by 2025, studies should be conducted on its unintended consequences, including whether there is any link between having several large floating solar farms here and an increase in the incidence and severity of flash floods.
Peter Heng Teck Wee