from rare or precious metals such as silver, tellurium, or indium, in-
su
ffi
cient facilities exist with which to recycle spent panels. Factors
associated with the maintenance of systems such as a shortage of skilled
manpower to meet growing demands for installation, maintenance,
inspection, repair, and evaluation of solar power systems are another
constraint as well. Furthermore, a lack of basic technical knowhow on
the user's behalf (especially in rural areas of the developing world) with
regard to solar power systems can result in irregular usage, over-
charging the battery, polarity reversal, by-passing the charge controller,
etc. which can all lead to system damage. Additionally, the plausibility
of cracks within the PV module, water intrusion, exposure to dust, and
algal growth can greatly lower the performance of the system. Poiso-
nous silicon tetrachloride, a byproduct of the polysilicon production
process, is costly (about $84,500 per ton) to process and recycle. To
make things worse, silicon tetrachloride is often dumped by most
manufacturing companies without proper pre-disposal treatment
[49]
.
Another obvious shortcoming is that solar energy can only be har-
nessed during the day and works most e
ffi
ciently when it is sunny.
Thus, solar energy is likely not the most reliable source of energy in
regions with unsustainable weather or climate conditions. Moreover,
air pollution levels at the installation area can also in
fl
uence the ef-
fectiveness of the solar cells
[50]
. Exposure to exhaust fumes and
aerosols was found to reduce the current of silicon solar cells by 10%
and 7%, respectively
[50]
. Finally, huge plots of land are often required
to generate solar power at large scales. The rule of thumb is that a
1 MW solar power plant with crystalline panels (about 18% e
ffi
ciency)
would require about 4 acres (16,187 m
2
) of land area, while thin
fi
lm
technologies (12% e
ffi
ciency) would require ca. 6 acres (24,281 m
2
)
[51]
.
3.2. Bene
fi
ts of solar energy technologies
It is well known that nothing can compare with the energy potential
of the sun. As solar power is theoretically abundant enough, it is more
than capable of ful
fi
lling the world's electricity demands. Because solar
energy is not only sustainable but also renewable, it is not necessary to
consider the notion that solar energy may eventually be depleted
[52]
.
Global warming is characterized by cataclysmic potential, thus por-
tending its harmful impact on the climate, environment (including
animals and plants), and human health
[53]
. Power plants (especially
coal-
fi
red) are a signi
fi
cant source of greenhouse gases (GHG), which
are responsible for approximately 25% of all anthropogenic emissions
[54]
. Hence, GHG emissions associated with the generation of solar
power (including manufacturing, installation, operation, and main-
tenance) are minimal
[55]
. The range of CO
2
emission per kilowatt-h
generated from coal, natural gas, and solar are estimated as 0.64
̴
1.63,
0.27
̴
0.91, and 0.03
̴
0.09 kg (emission ratio of 18:9.5:1), respectively.
As such, this comparison again con
fi
rms the superior environmental
friendliness of solar power among others
[15]
. Hence, solar power has
become one of the most feasible solutions to the current global warming
crisis, which if left unabated, could be extremely expensive with its
potential rami
fi
cations. Thus, mitigating global warming through the
substitution of coal and gas-based power sources with solar power will
eventually be environmentally, economically, and socially bene
fi
cial
toward achieving sustainable development.
Solar energy is considered to be a non-polluting, reliable, and clean
source of energy. Unlike other energy sources, its use is not accom-
panied by the release of harmful gases (e.g., oxides of C/N/S and/or
volatile organic compounds (VOCs)) and particles (e.g., soot, carbon
black, metals, and particulate matter (PM)). Such fossil fuel emissions
from gas-
fi
red power plants have been indicted with regard to causing
neurological damage, heart attacks, breathing problems, cancer, etc.
[56,57]
. Machol
[58]
reported that the replacement of fossil fuels with
renewable energy could minimize premature mortality rates, lost
workdays, and reduce the overall costs for healthcare. Additionally,
fossil fuel power plants require huge amounts of water for their
operation to exert a signi
fi
cant in
fl
uence on the current water shortage
issues. A limited accessibility to water during droughts and heat waves
has hindered the generation of electricity by limiting its generation
from power plants. On the other hand, electricity generated from solar
installations does not require water to operate; additionally, the ex-
istence of fuel by-products or the requirement for radioactive waste
storage is nonexistent.
When compared with fossil fuel technologies that are primarily
mechanized and capital intensive, solar power technologies are re-
garded as being more labor-intensive. A positive aspect of this notion is
that solar technologies should improve job opportunities. On average,
more jobs can be created per unit of electricity production with solar
energy as opposed to fossil fuels. The Solar Foundation
[59]
reported
that the solar industry employed around 208,859 workers in the USA on
either a part-time or full-time basis for manufacturing, installation, and
sales. Within a year, a growth rate of 20.2% was reported. Moreover,
the industries responsible for solar energy supply chain systems will
also bene
fi
t tremendously, while some unrelated local businesses (due
to an increase in shop and restaurant business hours) would also bene
fi
t
from an overall increase in income
[60]
. Furthermore, local solar en-
ergy projects would keep money circulating within the local economy,
thereby saving a substantial amount of money presently being used for
the importation of fossil fuels from other locations. From an economical
perspective, solar power is bene
fi
cial in a variety of ways due to tax
incentives, an elimination of electricity bills, increased property values,
and high durability.
The e
ffi
ciency of solar power technologies has increased greatly in
recent years and has been accompanied by a progressively steady de-
cline in costs, which are projected to drop even further. For instance,
the total cost of a PV module has been reduced from USD 1.30 per watt
(in 2011) to USD 0.50 per watt (in 2014) (ca. 60% cost reduction)
[61]
.
As the solar markets mature and more companies take advantage of the
solar economy, the availability and a
ff
ordability of solar power will
grow at an impressive pace.
Although solar power systems require an upfront investment for
their installation, they otherwise operate at very low costs. Unlike the
price of fossil fuels, which are prone to substantial price swings, the
fi
nancial demand for solar power is relatively stable over long periods.
Moreover, there are no (mechanically) moving parts in solar panels,
making them free of noise pollution and durable (no wear and tear),
with very little in the way of required maintenance. Moreover, solar
panels can be easily installed on roof tops and mounted onto building
walls, meriting their installation
fl
exibility. Furthermore, solar power
systems are less prone to large-scale failure because they are distributed
and composed of numerous individual solar arrays. Therefore, if any
section of arrays were found to be faulty, the rest could continue to
operate. However, additional solar modules could also be added over
time to improve the energy generation capacity. These notions reveal
huge advantages in the ruggedness and
fl
exibility of solar power sys-
tems over all other energy sources that have already been established.
4. Future prospects of solar technology
Solar energy is one of the best options to meet future energy de-
mand since it is superior in terms of availability, cost e
ff
ectiveness,
accessibility, capacity, and e
ffi
ciency compared to other renewable
energy sources
[62,63]
. For the
fi
rst time, researchers have successfully
measured in detail the
fl
ow of solar energy, in and between di
ff
erent
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