Department of Electrical and Electronics Engineering

Course : Renewable Energy Sources

Course Code: 19EEE121

By
Mrs. Soumya R M

Department of Electrical and Electronics Engineering

 Solar Pond

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 Solar Pond
➢ Solar pond

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 Solar photovoltaic systems
➢ Solar photovoltaic (PV) systems convert solar energy directly into electrical energy.
➢ Basic conversion device used is known as a solar photovoltaic cell or a solar cell.
➢ A solar cell is basically an electrical current source, driven by a flux of radiation. Solar cells were first produced
in 1954 and were rapidly developed to provide power for space satellites based on semiconductor electronics
technology.
➢ Solar cell is the most expensive component in a solar PV system (about 60 per cent of the total system cost)
though its cost is falling slowly. Commercial photocells may have efficiencies in the range of 10–20 per cent and
can approximately produce an electrical energy of about 1 kWh per sq. m per day in ordinary sunshine.
➢ It has a life span in excess of about 20 years. As a PV system has no moving parts it gives almost maintenance
free service for long periods and can be used unattended at inaccessible locations.
➢ Applications : Major uses of photovoltaics have been in space satellites, remote radio communication
booster stations and marine warning lights.
➢ These are also increasingly being used for lighting, water pumping and medical refrigeration in remote areas
especially in developing countries.
➢ Solar powered vehicles and battery charging are some of the recent interesting application of solar PV power.

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 Contd…
➢ Major advantages of solar PV systems over conventional power systems are:
➢ It converts solar energy directly into electrical energy without going through thermal-mechanical link. It has no
moving parts.
➢ Solar PV systems are reliable, modular, durable and generally maintenance free.
➢ These systems are quiet, compatible with almost all environments, respond instantaneously to solar radiation
and have an expected life span of 20 years or more.
➢ It can be located at the place of use and hence no or minimum distribution network is required, as it is
universally available.
➢ It also suffers from some disadvantages such as:
➢ At present the costs of solar cells are high, making them economically uncompetitive with other conventional
power sources.
➢ The efficiency of solar cells is low. As solar radiation density is also low, large area of solar cell modules are
required to generate sufficient useful power.
➢ As solar energy is intermittent, some kind of electrical energy storage is required, to ensure the availability of
power in absence of sun. This makes the whole system more expensive.
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 Contd…
➢ Typical Solar Cell

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 I–V Characteristics
The well-known characteristic of an ordinary silicon PN junction is shown in Fig. 6.13 as dark characteristic
with the junction not illuminated. Mathematically this is given by:

where Io is reverse saturation current, VT is known as voltage equivalent of

temperature and is given as:

where, k is Boltzmann’s constant (in J/K), T is temperature in

Kelvin and q is charge of an electron in coulombs.

At room temperature (20 °C) the value of VT is 25.283 mV.

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 Contd..

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 Contd..

Figure (a) Schematic symbol of photovoltaic cell (b) I-V characteristic, maximum power point (c)
P-V characteristics
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 Contd..
➢ The schematic symbol of a solar PV cell with standard sign convention for voltage and current is shown in Fig. 6.14(a).
Adopting standard sign convention for a solar PV cell the characteristic of Fig. 6.13 will be redrawn as shown in Fig. 6.14(b).
Mathematically, the I-V characteristic of a solar cell may be written (as per standard sign convention of an energy source) as:

In order to obtain as much energy as possible from the rather

costly PV cell, it is desirable to operate the cell to produce
maximum power. The maximum power (Pm)
point can be obtained by plotting hyperbola defined by V × I =
constant, such that it is tangential to I-V characteristic. The
voltage and current corresponding to this point are peak point
voltage, Vm and peak point current, Im respectively. Thus there
is only one point on the characteristic at which it will produce
maximum electrical power under the incident illumination level.
Figure 6.14 (a) Schematic symbol of photovoltaic cell (b) I-V
characteristic, maximum power point (c) P-V characteristics
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 Contd…
➢ ‘fill factor’, FF which indicates the quality of cell, is defined as the ratio of the peak power to the product of
open circuit voltage and short circuit current, i.e.,

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 SOLAR CELL CLASSIFICATION
➢ Solar cells may be classified on the basis of (i) thickness of active material, (ii) type of junction structure, and (iii)
the type of active material used in its fabrication, as shown in the chart below (Fig. 6.18).

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 SOLAR CELL, MODULE, AND ARRAY CONSTRUCTION
➢ The basic cell structure of a typical N-on-P, bulk silicon cell is shown in Fig. 6.28.
➢ The bulk material is P-type silicon with thickness 100 to 350 microns,
depending on the technology used.
➢ A thin layer of N-type silicon is formed at the top surface by diffusing an impurity
from Vth group (phosphorus being most common) to get a PN junction.
➢ The top active surface of the N layer has an ohmic contact with metallic grid structure
to collect the current produced by impinging photons.
➢ The metallic grid covers minimum possible top surface area
to leave enough uncovered surface area for incoming photons.
➢ Similarly, the bottom inactive surface has an ohmic metallic contact
over the entire area.
➢ These two metallic contacts on P and N layers respectively form the positive
and negative terminals of the solar cell.

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 Solar PV Module
➢ A bare single cell cannot be used for outdoor energy generation by itself. It is because
➢ (i) the output of a single cell is very small and
➢ (ii) it requires protection (encapsulation) against dust, moisture, mechanical shocks and outdoor harsh conditions.
➢ Workable voltage and reasonable power is obtained by interconnecting an appropriate number of cells.
➢ Cells from same batch are used to make PV module. This is done to ensure that mismatch losses are minimal in the module.

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 Contd…
➢ Solar PV Panel

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 Contd..
➢ Solar PV Array
➢ In general, a large number of interconnected solar panels, known as solar PV array, are installed in an array
field. These panels may be installed as stationary or with sun tracking mechanism.
➢ It is important to ensure that an installed panel does not cast its shadow on the surface of its neighboring
panels during a whole year.
➢ The layout and mechanical design of the array such as tilt angle of panels, height of panels, clearance among
the panels, etc., are carried out taking into consideration the local climatic conditions, ease of maintenance,
etc.

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 SOLAR PV SYSTEMS
➢ Solar PV systems are broadly classified as:
➢ 1. Central Power Station System
➢ Central PV power stations are conceptually similar to any other conventional central power station.
➢ They feed power to grid. These are being proposed in few MW range to meet daytime peak loads only.
➢ Central PV power stations of up to 6 MWp (peak MW) capacities have already been experimented within USA
and Europe.
➢ 2. Distributed System
➢ Distributed form of energy use is unique and much more successful with solar and most
other renewable energy sources. These systems can be further divided into three groups:
(a) Stand Alone or Off Grid
(b) Grid-Interactive or Grid Tied
(c) Hybrid PV System

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 Contd..
(a) Stand Alone or Off Grid
➢ It is located at the load center and dedicated to
meet all the electrical loads of a village/community
or a specific set of loads. Energy storage is generally
essential.
➢ It is most relevant and successful in remote and
rural areas having no access to grid supply.

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 Contd..
➢ Grid-Interactive or Grid Tied

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 Contd..
➢ Hybrid PV Systems

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 Contd..
➢ Applications of Solar PV Systems
➢ Grid Interactive PV Power generation
➢ Water Pumping
➢ Lightning
➢ Medical Refrigeration.

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 THANK YOU

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