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Climate Change Corner
Use of renewable energy in Hong Kong
With a sub-tropical climate and its coastal location, Hong Kong has its share of wind and sunlight as sources
of renewable energy. Assessment by the Hong Kong Observatory indicates that the wind power potential
for Hong Kong is restricted to hilltops and offshore areas. On the other hand, the abundance of solar
energy suggests that rooftops in buildings offer good opportunities for receiving this inexhaustible source of
energy, as part of our move towards a low-carbon economy.
Results of solar measurements in 2009 show that the annual total direct solar radiation received by a plane
surface optimally facing 120° from north and tilting at 40° from the horizon, was about 1570 MJm-2, or on
average, 4.3 MJm-2 per day. Assuming that 30% (about 28 km2) of the total surface areas of residential,
public rental housing, commercial and industrial buildings and government, institution and community
facilities in Hong Kong, can be used for installing PV-type solar panels of 20% efficiency, the annual total
solar thermal energy that can be collected will be about 24 TJ per day, or 5.4% of total electricity
consumption in Hong Kong.
Another development involving solar energy is the increasing popularity of solar thermal collectors, which
convert sunshine into heat. Calculations show that, for a house with a rooftop of 100 m2, about 530 litres of
warm water of 42 oC can be produced per day in the cool months if 20% of the rooftop surface area is
deployed for solar-thermal collectors. This amount of warm water is sufficient for 13 persons assuming
that each of them consumes 40 litres of water in a shower. The savings in electricity amounts to nearly
$400 per month in the cool months.
Here are just two examples of how solar energy can be meaningfully explored in Hong Kong. Both of
them also act to reduce rooftop temperature, thus reducing the demand for fossil-based energy and aiding in
the combat of the effects of climate change. With further development in green technology, there is
potential for even greater use of solar energy in future.
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This article is contributed by B Y Lee and H Y Mok of Hong Kong Observatory with the co-ordination of
the Environmental Division.