Solar power has been developed in two main directions, one using
photovoltaic (PV) technology and the other concentrating the sun’s rays
to heat water directly.
PV cells convert solar energy into el...
ectricity using semiconductors
of two types. The more common crystalline silicone type is 14%–20%
efficient. The other type, which uses a thin film, is less than 12% efficient
but is cheaper to make and more suitable for places with sunlight broken up and reflected by, for example, clouds and nearby structures.
A panel’s capacity factor is a measure of its effective utilization. A solar
panel rated for 1 kilowatt (kW) can theoretically produce 8,760 kilowatthours
(kWh) annually. However, actual output depends on the amount
of energy in the sunlight, which depends on the location, daylight
hours, cloud cover and how it reflects light, and ambient temperature.
Considering these uncontrollable nature-linked parameters, the actual
output of a 1 kW solar panel may be only 1,300 kWh in a year. That works
out to a capacity factor of 15%, which is typical.
Concentrated solar power uses an array of mirrors to cause the sun’s
rays to converge on a central tower to heat fluid and raise steam to run a
turbine, much as in a conventional thermal power plant. This technology
has the option, with added cost, to store solar energy in salt solution and
use it to generate electricity at night. Several configurations are used to
concentrate the solar energy, their efficiencies ranging from about 10% for
flat mirrors to over 30% for centralized towers and parabolic dishes.
Photovoltaic technology has been applied various ways since the
1960s. Despite being safe, clean, and extremely reliable, and its requiring
no fuel and little maintenance, it has always been too expensive to achieve
grid parity, or the ability compete commercially on the grid without
subsidies. This drawback may be changing, however, as the decades-long
decline in PV module prices has accelerated in the last 5 years, leading
some to speculate that grid parity is likely by the mid-2010s.
Should grid parity be achieved, it will have immense implications for
all Asian countries, as they all need more power sources and have solar
resources ranging from good to excellent. However, availability only
during daylight hours, combined with the challenges of finding large
tracts of land to accommodate large PV capacity, may limit penetration
unless cheaper storage is developed. Meanwhile, PV is already the
cheapest way to electrify small communities remote from the grid and
thus has a potential role in providing electricity to hundreds of millions
of Asians currently without power.
Asia’s solar resource is shown in Figure 2.3.3. Lighter, more energetic
colors indicate areas with more sunlight. Places close to the Equator
have more hours of sunshine annually, but islands and coastal areas have
more cloudy days that diffuse the sunlight. The sun is weaker at higher
latitudes and never directly overhead, requiring that PV panels be fixed at
an incline to capture the most solar energy. PV panels that track the sun
as it rises and sets every day capture more sunlight than do fixed ones but
with higher capital and maintenance costs for the tracking device.
Tilting and tracking even out spatial variation in the solar resource.
From the worst site to the best site in Asia, the capacity factor for fixed
arrays varies from 10% to 20%, and most sites across the continent can
achieve at least a capacity factor close to 16%. Thus, tilting and tracking
makes solar energy accessible virtually anywhere in Asia. PV technology has become cheaper over the decades it has been
commercially available, and recently at an accelerated pace. The cost
of crystalline silicon modules fell from about $80/watt in 1977 to less
than $10/watt by the late 1980s and $4/watt in early 2008 (Economist 2012). At this point the price dropped off a cliff, halving in 2008-2009.
Suppliers ramped up production to obtain subsidies offered to renewable energy installations in Canada, Germany, and Spain, and they shifted manufacturing to lower-cost producers in the PRC that already had
the skills for manufacturing semiconductors. Rapid cost declines have
continued since then—recently reaching $0.70/watt—with radical implications for the PV industry. Module manufacturers have expressed
some concern about overcapacity and low price, but production continues
to expand as they find new ways to cut costs and learn from experience.
------ Notes: Color bar shows average global radiation on the horizontal in kWh/m2. For selected locations, the capacity factors for fixed arrays and tracking
photovoltaic systems have been calculated with RETScreen 4 software. The capacity factor—percentage of actual energy of the theoretical energy
production—is given for some locations; there are two values, one for a fixed system and another for tracking system.
---- Source: Meteonorm. www.meteonorm.com.