Page 15 - A Comprehensive Guide to Solar Energy Systems

Chapter 1 • Why Solar Energy? 7

is paid for PV-generated electricity that is fed into the grid. This premium can be several
times higher than the normal tariff paid for fossil-fuel-generated electricity. This has led
to the establishment of a large number of wind farms, as well as many rooftop PV systems
for individual houses.
In spite of its intermittent nature, solar power from PV panels has many advantages:
• The wafer panels are manufactured in modular form and can be retrofitted to roofs
anywhere the sun shines.
• PV panels can be installed where the power is needed thus eliminating the need to
integrate into grid systems. This is particularly important in areas, which do not have
grid electricity.
• Often, particularly in hot countries, which have a high demand for air conditioning,
the generation of PV electricity coincides with the greatest need for electricity during
the day.
• PV electricity is useful over a wide range from the charging of mobile phones, street
lighting using LEds, telecommunications [20], space vehicles, solar pumps [21], and
grid electricity.
Concentrated photovoltaics (CPV) use optical lenses or curved mirrors to concentrate
light onto small but highly efficient solar cells. often these systems are fitted with cooling
systems because the efficiency of PV decreases with cell temperature [18].
Most (99%) of European solar cells are connected to the grid while off-grid systems are
more common in Australia, South America, Africa, and South Korea [22].
PV systems are found in three marketing area: residential rooftop, commercial roof-
top, and ground-mounted utility-scale systems (solar farms). In 2013, rooftop systems ac-
counted for 60% of the global installations; this is changing rapidly with a shift toward util-
ity-scale systems and as of 2017 utility systems in the United States have a higher installed
capacity than the sum of residential and commercial. Residential systems are typically
around 10 kW while commercial systems reach megawatt scale. The utility-scale power
plants are in the range of 100–500 MW and moving to the 1 GW capacity, and are becoming
more common especially in hot regions of the world. Three years ago, California’s 550 MW
(Topaz Solar farm) was the world’s largest solar project. A year later, another large Califor-
nian solar farm (the 579 MW Star Solar farm) was built followed in 2016 by India’s 648 MW
Kamuthi Solar Power Project. This was surpassed in 2017 by China’s Longyangxia dam
Solar Park of 850 MW [23].
A solar farm PV system connected to the grid, consists of the solar array and additional
components usually called “balance of system” (BoS), which includes power conditioning
equipment, and dC to AC power converters (called inverters) (Chapter 15).
The efficiency of commercial PV modules is about 16% and the modules are expected
to have a life-time of 25 years. Higher efficiencies have been recorded [24].