Page 28 - Sphere No.28 (Mar 2011)

26 Sphere
According to Mr Lau, there were a number
of technical reasons for choosing TFPV panels
rather than the more common modules which use
thicker layers of crystalline silicon. These are the
types of panel used for the 350 kilowatt instal-
lation at the Electrical and Mechanical Services
Department in Kowloon Bay, and the 198 kilowatt
system at the Hong Kong Science Park, both of
which were completed in 2005.
“We have been studying these TFPV pan-
els compared with the conventional crystalline
silicon panels,” said Mr Lau. “One reason we
chose the thin film ones is that in producing those
panels much less silicon is required. On the other
hand, it takes a large amount of silicon to produce
conventional panels, which means you expend a
lot of energy on producing the panels and then
you wait for several years before the solar energy
can pay back the energy used in making the pan-
els. Conventional panels have a payback period of
about three or four years, as opposed to one and a
half years for PV panels. The panels have a design
life of 20 years.
“The second reason is that conversion effi-
ciency of conventional panels drops quickly under
high temperatures, while that of amorphous thin
film panels does not. Amorphous thin film panels
maintain roughly the same conversion efficiency,
so they are more suitable for a tropical or sub-
tropical environment.
“Finally, thin film panels maintain a good
percentage of conversion efficiency under weak
sunlight conditions. The conventional ones do
not. That means thin film panels can harness more
energy over a year.”
HK Electric’s findings so far are that better than
expected power output can be achieved in condi-
tions of low irradiance.
The adoption of solar energy is now a well es-
tablished international trend, notwithstanding the
still relatively high costs involved. The panels are
generally perceived as being environmentally su-
perior to most alternative energy sources, because
they emit no gaseous or liquid pollutants and do
not produce noise.
“Solar and wind power generation are growing
fast,” stated Mr Lau. “In 2010 installation of solar
photovoltaic systems crossed the threshold of 10
gigawatts globally in a single year – setting a new
record and once inconceivable number. Expecta-
tions for next year are close to 20 gigawatts. The
global market has been growing at a phenomenal
rate – an average of 47 per cent per annum over
the past five years.”
In some respects Hong Kong is well positioned
to harness solar energy. A generally sunny climate
The System’s solar
panels use advanced
Amorphous Silicon
Thin Film Photovoltaic
technology, so they
harness more energy
than other panels, are
more environmentally
friendly to produce and
are better suited to a
sub-tropical climate.