explain the solar water heater and solar cell
Answers
Answer:
Solar water heater :
The main Principle is to focus solar energy to generate large amount of heat.
Solar water heating (SWH) is the conversion of sunlight into heat for water heating using a solar thermal collector.
A variety of configurations is available at varying cost to provide solutions in different climates and latitudes. SWHs are widely used for residential and some industrial applications.
A sun-facing collector heats a working fluid that passes into a storage system for later use. SWH are active (pumped) and passive (convection-driven). They use water only, or both water and a working fluid.
They are heated directly or via light-concentrating mirrors. The mirrors are usually Concave mirrors.
SOLAR CELLS:
The main Principle is convert a solar energy to electrical energy and store it in recyclable batteries
Solar cell, or photovoltaic cell, is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.
It is a form of photoelectric cell, defined as a device whose electrical characteristics, such as current, voltage, or resistance, vary when exposed to light.
Mainly semi- conductors are used in photo voltaic cells.
Solar water Heater :--------
Salient Features:------------
1) Fuel Saving :::- A 100 litres capacity SWH can replace an electric geyser for residential use and saves 1500 units of electricity annually.
2) Beneficial for Environment :::- A SWH of 100 litres capacity can prevent emission of 1.5 tonnes of carbon dioxide per year.
3) Total Life - 15 to 20 years approximately.
4) Costing :::- Rs.15000- 20,000 for a 100 litres capacity system and Rs.110-150 per installed litre for higher capacity systems.
5) Payback period :::- 3-4 years when electricity is replaced 4-5 years when furnace oil is replaced 5-6 years when coal is replaced.
Major Components:----------
1) Solar Collector, Its purpose is to collect solar energy
2) Insulated Tank, Its purpose is to store hot water
3) Supporting Stand
4) Connecting Pipes and Instrumentation, etc.
Working Principle :------------
→ The Sun rays fall on the Solar Collector. A black absorbing surface (absorber) inside the collector, which absorbs solar radiation and transfers the heat energy to water flowing through it. Heated water is collected in a tank which is insulated to prevent heat loss. Then Circulation of water from the tank through the collector and back to the tank continues automatically.
→ A Solar Water Heater consists of a Collector panel to collect solar energy and an Insulated Storage Tank to store hot water.
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Solar cell :---------
→ It essentially consists of a silicon PN junction diode with a glass window on top surface layer of P material is made extremely thin so, that incident light photon’s may easily reach the PN junction. When these photons collide with valence electrons’.
→ They comport them sufficient energy as to leave their parent atoms. In this way free electrons and holes are generated on both sides of the junction.
→ Due to these holes and electrons current are produces. This current is directly proportional to the illumination’s (mw/cm2) and also depends on the size of the surface area being illuminated.
→ Silicon and germanium are the most widely used semiconductors materials for solar cells although gallium arsenide, Indium arsenide and Cadmium arsenide are also being used nowadays.