1. Solar Energy, Solar Power, Solar
Thermal systems & solar
terminologies
Lecture # 2
2. Solar Energy
• Solar energy is radiant light and heat from the Sun that is harnessed using
a range of ever-evolving technologies such as solar
heating, photovoltaics, solar thermal energy, photosynthesis.
• It is an important source of renewable energy and its technologies are
broadly characterized as either passive solar or active solar depending on
how they capture and distribute solar energy or convert it into solar power.
• Active solar techniques include the use of photovoltaic
systems, concentrated solar power and solar water heating to harness the
energy.
• Passive solar techniques include orienting a building to the Sun, selecting
materials with favorable thermal mass or light-dispersing properties, and
designing spaces that naturally circulate air.
3.
4. Solar Power
• Solar power is the conversion of sunlight into electricity, either directly
using photovoltaics (PV), or indirectly using concentrated solar power.
• Concentrated solar power systems use lenses or mirrors and tracking systems
to focus a large area of sunlight into a small beam. Concentrated solar
power (CSP, also known as "concentrated solar thermal") plants use solar
thermal energy to make steam, that is there after converted into electricity by a
turbine.
• Photovoltaic cells convert light into an electric current using the photovoltaic
effect. Photovoltaic (PV) systems use solar panels, either on rooftops or in
ground-mounted solar farms, converting sunlight directly into electric power.
5. Solar Heating System
Any system which utilizes solar energy to heat a building is
Known as a solar heating system.
Solar heating systems are classified into two types
depending upon the extent to which solar equipment and
building design features are utilized to heat the house with
solar energy as:
• active solar heating system
• passive heating system
6. Active solar heating system
• an active system is one which involves collector
hardware and fluid-moving equipment to circulate fluid to
collect and distribute solar heat in the building.
• By hardware and fluid movers we mean pumps and
blowers, and other devices such as motorized dampers
and valves to direct fluid flow in the system. It is called
“active” solar heating system because it uses pumps and
fans to transfer the heat. It has two types
• Solar water heater
• Solar air heater
7.
8.
9. Passive Solar Heating System
• Passive design is incorporated into the building design
and does not depend primarily on forced circulation of a
fluid either to collect or distribute solar heat to various
parts of the building. Alternatively passive heating could
be defined as one in which thermal energy flows by
natural means.
10. Types of Solar Passive System
• There are two types of Solar Passive system
• Direct Gain
• Thermal storage wall
11. • Direct Gain
The simplest type of
passive heating uses
direct solar gain, in
which solar radiation
enters a building
enclosure through glass
walls or roofs and is
absorbed by massive
walls and floors within
the building.
12. • Solar Thermal Storage
wall
In addition to storage in the
interior walls and floors ,
heat is stored in a masonry
wall or water containers
along the south wall. With
an insulating curtain behind
the thermal wall, the rate of
heat delivery can be better
regulated than direct gain
passive systems.
13. Beam radiations
The solar radiations received from the sun without having been scattered by the
atmosphere. Beam radiations are often referred as direct solar radiations .
Diffuse radiations
The solar radiations received from the sun after its direction have been changed by
scattering by the atomosphere
These are also referred as sky radiations or solar sky radiations
Total solar radiations
The sum of the beam and diffuse solar radiations on a surface
They are often refered to as global radiations
Solar terminologies
15. Irradiance (G), W/m2
The rate at which the radiant energy is incident on a surface per unit
area of the surface.
16. Radiosity or radiant exitance, W/m2
The rate at which radiant energy leaves a surface per unit area by
combined emission, reflection and transformation
Emissive power or radiant Self- existance, W/m2
The rate at which radiant energy leaves a surface per unit area by
emission only
