Despite its
limitations, the global growth rate of solar photo voltaic
installations has spurted.
Those who dislike nuclear energy because of its safety problems
strongly tout solar energy as a clean and renewable alternate for
India. India experiences clear sunny weather for over 250 days a year,
with the average daily solar energy incident over the country
being as high as 5.8 kilowatt-hours per square metre, With a land
area of roughly 3 million sq km, this translates to a total energy
incidence of 6000 trillion units/year (1 unit = 1 kilowatt hour).
As compared to this, the Ministry of Power has fixed the electricity
generation target from conventional sources for the year 2008-09 at
0.75 trillion units, which is not even 0.1 per cent of the incident
solar energy. Therefore, the potential for the sun to meet all
our energy needs and liberate us from the dependence on limited and
polluting fossil fuels is overwhelming. The question is: Can this
potential be translated practically and economically into actuality?
A much-explored method of tapping solar energy is the photovoltaic
conversion of solar light to electricity. While a number of materials
are known to enable this conversion, the most popularly deployed is
semiconductor grade silicon. But, manufacturing semiconductor silicon
is a very complex, elaborate and energy — an intensive process which
employs a number of toxic chemicals. This makes the material very
expensive.
On top of this, the conversion efficiency (electrical energy produced
as a percentage of incident solar light energy) for this material is in
the range of eight to 15 per cent, depending on what type of
silicon is used (amorphous or single crystal or polycrystalline).
The net effect of all this is that solar photovoltaic (SPV) energy
systems are expensive in terms of the capital needed. At present,
commercially available systems cost around $ 6 to $ 8 per installed
peak watt. Compare this with the capital cost of fossil fuelled power
plants at $ 1 to $ 2 per installed watt (depending on the
technology and fuel) and it becomes apparent why there is no runaway
popularity of SPV systems.
The advent of thin film technologies raises the hope of mass production
of basic SPV stock, leading to economies of scale and lower
prices.
One technology which mimics nature’s method of converting
sunlight to energy, has shown considerable promise in eventually
producing SPV power at costs comparable to conventional grid
electricity. Called Dye Sensitised Solar Cell (DSSC) technology,
this promises to deliver SPV power at a cost of around $1 per peak
watt, which is competitive with conventional grid power.
The other severe limitation for SPV systems is the diffuse nature of
incident solar energy. Calculating on the basis of roughly 10 sq. m of
panels per kilowatt, a 400 megawatt power plant would occupy 4
sq. kms of land for its panels. Clearly, SPV is not the answer
for large capacity utility scale power plants .
However, the possibility of hundreds of small, stand alone SPV power
generating units interconnected to the grid is being explored.
One example in India is Sagar Island in West Bengal’s Sunderbans where
25 SPV power plants with a total capacity of 1 W have been connected to
the grid.
Despite its limitations, the global growth rate of SPV installations
has spurted in the last few years with the backing of hefty subsidies
offered by governments in countries like Germany, Japan, Spain and the
US. According to the Earth Policy Institute, global SPV
production has been almost doubling every year from 2002 and
jumped to 3800 MW in 2007.
Preliminary data indicates that the world total for SPV
installed capacity stood at 12,400 megawatts by the end of last year.
In India the installation of SPV systems for feeding power into the
grid has been meagre so far due to lack of adequate incentives. The
government of India has recently announced a new set of initiatives for
installing SPV systems, such as paying Rs15 per unit of power fed to
the grid, 20 per cent of capital provision for SPV related projects in
SEZs, for example.
But all said and done SPV systems will only form the fringe
of the nation’s power generation capacity, which is expected to rise
from 1,45,000 MW now to nearly 4,00,000 MW by 2030.
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