A solar panel is composed of a package of photovoltaic cells. It can be used in a larger photovoltaic system for generating and supplying electric energy for residents and other commercial applications. Solar radiation that falls directly on the solar panel is converted into direct current. The electric energy output of each panel varies from 100 to 320 W.
A solar thermal collector, on the other hand, collects heat by direct absorption of sunlight. It consists of a collector that converts energy from sunlight into a more usable form of energy. Solar collectors may be referred to as solar parabolic apparatus for more complex installations and solar air heat for less complex installations. The more complex collectors are employed in solar power plants for heating water to produce steam which in turn drives a turbine connected to an electric generator for generating electricity. However, the less complex collectors are used in commercial and residential buildings for supplemental space heating.
Most of the solar panels are around 11-15% efficient. The efficiency of the panels is measured by the amount of sunlight hitting the panel, which in turn gets converted into electricity. Solar panels with small surface area are highly efficient. Efficiency of the panels is also affected by the orientation of the panel, pitch or tilt of the roof and panel, temperature and shade of the roof.
The performance of the solar thermal collector depends on the following criteria:
- Area of the solar collector
- Total amount of solar radiation incident on the collector
- Positioning of the collector’s tilt and the collector’s orientation.
However, solar collector efficiency is influenced by several factors like heat gain, surface area, the conversion factor and heat loss through conduction and convection. Low-temperature solar collector models operate at high efficiency levels when temperature difference is between 5 and 30°C (41 and 86°F) and medium-temperature models operate when temperature difference is between 15 and 200°C (59 and 392°F).
The key benefits of solar panels include the following:
- Noise-free with no moving parts
- Low maintenance cost
- Easy to install
- Promotes energy independence
- Operates efficiently with beam or diffuse solar radiation.
The key benefits of solar thermal collectors include the following:
- It is sustainable to high temperatures
- High efficiency
- Utilization of larger area by using inexpensive mirrors
- Redirection of concentrated light to a suitable location through optical fibers
- Heat can be stored for power generation during overnight and cloudy conditions.
The following are some of the disadvantages involved in the utilization of solar panel:
- High initial costs
- Repairing of damaged solar panel installations is expensive
- It does not produce power during night or inclement weather conditions
- Efficiency of solar panels can be affected by pollution.
Certain disadvantages of solar thermal collectors include:
- Inability to produce electricity under diffused light conditions
- It requires sun tracking for maintaining sunlight focus.
Some of the applications of solar panels include the following:
- Solar-powered radios
- Solar-powered fans
- Solar flashlights
- Solar night lights
- Charging batteries.
Solar thermal collectors find applications in the following:
- Solar-assisted cooling, especially for commercial building and offices with central air-conditioning systems
- Pool heating – Swimming pools utilize more amount of energy for maintaining the desired temperature. It is possible to significantly reduce pool heating energy by using flat plate solar thermal collectors.
- Supplemental heating – Solar thermal collectors can store heat in summer for use in winter.
- It can also be used for domestic purpose like heating hot water for washing clothes and showers.
Sources and Further Reading