Solar Thermal Energy | Electrical Seminar Topic
Solar Thermal Energy
Solar thermal energy (STE) is a technology for harnessing
solar energy for thermal energy (heat). Solar thermal collectors are classified
by the United States Energy Information Administration as low-, medium-, or
high-temperature collectors. Low-temperature collectors are flat plates
generally used to heat swimming pools.
Medium-temperature collectors are also
usually flat plates but are used for heating water or air for residential and
commercial use. High-temperature collectors concentrate sunlight using mirrors
or lenses and are generally used for electric power production. STE is
different from and much more efficient than photovoltaics, which converts solar
energy directly into electricity.
While existing generation facilities provide
only 600 megawatts of solar thermal power worldwide in October 2009, [note 1]
plants for an additional 400 megawatts are under construction and development
is underway for concentrated solar power projects totalling 14,000 megawatts.
Systems for utilising low-temperature solar thermal energy include
means for heat collection; usually heat storage, either short-term or inter
seasonal; and distribution within a structure or a district heating network. In
some cases more than one of these functions is inherent to a single feature of
the system (e.g. some kinds of solar collectors also store heat). Some systems
are passive, others are active (requiring other external energy to
function).
Heating is the most obvious application, but solar cooling can be
achieved for a building or district cooling network by using a heat-driven
absorption or adsorption chiller (heat pump). There is a productive coincidence
that the greater the driving heat from insolation, the greater the cooling
output. In 1878, Auguste Mouchout pioneered solar cooling by making ice using a
solar steam engine attached to a refrigeration device.
In the United States, heating, ventilation, and air
conditioning (HVAC) systems account for over 25% (4.75 EJ) of the energy used
in commercial buildings and nearly half (10.1 EJ) of the energy used in
residential buildings. Solar heating, cooling, and ventilation technologies can
be used to offset a portion of this energy.
In Europe, since the mid-1990s
about 125 large solar-thermal district heating plants have been constructed,
each with over 500 m2 (5400 ft2) of solar collectors. The largest are about
10,000 m2, with capacities of 7 MW-thermal and solar heat costs around 4
Eurocents/kWh without subsidies.[8] 40 of them have nominal capacities of 1
MW-thermal or more.
The Solar District Heating program (SDH) has participation
from 14 European Nations and the European Commission, and is working toward
technical and market development, and holds annual conferences.
