CH- 7 SOLAR SYSTEMS Marks: 08 (12)
Solar cells:
Principle:
Solar cell works on principle of photovoltaic effect. Solar cells collect solar radiation from the sun and actively convert that energy to electricity.
Solar panels are comprised of several individual solar cells.
These solar cells function similarly to large semiconductors and utilize a large-area p-n junction diode.
When the solar cells are exposed to sunlight, the p-n junction diodes convert the energy from sunlight into usable electrical energy.
The conversion of sunlight to usable electrical energy is called the Photovoltaic Effect.
Construction:
The surface layer of p-type material is extremely thin, so that light can penetrate to the junction.
The nickel plated ring around the p-type material is positive output terminal, and the plating at the bottom of the n-type is negative output terminal.
Working:
When light, in the form of photons, hits our solar cell, its energy frees electron-hole pairs. Each photon with enough energy will normally free exactly one electron, and result in a free hole as well.
If this happens close enough to the electric field, the field will send the electron to the N side and the hole to the P side.
This causes further disruption of electrical neutrality.
If we provide an external current path, electrons will flow through the path to their original side (the P side) to unite with holes that the electric field sent there.
The electron flow provides the current, and the cell's electric field causes a voltage. With both current and voltage, we have power, which is the product of the two.
Use of solar cell in street light:
The solar street lights system convert sun energy to electricity and the system is prompted to turn on as the darkness approaches. Therefore, these lights automatically switch on after the sunset and after sunrise it switches off.
This system consists of the following parts:
Solar panels
LED light
Rechargeable battery
Controller
Pole
Solar panels: In solar street lights, the solar panel is one of the most important parts. Solar panel consists of number of solar cell connected in parallel and series to get sufficient voltage and current. Solar cells convert solar energy from sun into electrical energy.
LED Light: In modern solar street lights, LEDs are used as lighting source and LED provide much brighter light with lower energy consumption. The energy utilization of LED lamp is lower than the conventional lamps. LED lights offer many benefits like Long life, durability, Eco-friendly and zero ultraviolet radiations.
Rechargeable Battery: In solar street lights, a battery is used to store electricity from the solar panel during the day time. It provides energy in the night time. The capacity and lifetime of the battery is very important as they affect the backup power.
Controller: The controller controls the battery from overcharging and under charging conditions. By receiving the power from solar panels it continuously charges the battery in day time and while in evening it supplies the battery power to set of LED street lights. In solar LED street lights, a controller is very important as it usually decides to switch on or switch off the lighting and charging.
Pole: For every street light, a strong pole is necessary. Especially for a solar street light, there are some components like fixtures, batteries and panels mounted on the top of the pole,
Applications of solar cells:
Calculators
Solar water heater
Solar water pumps
Satellites
Solar lighting
Solar car
Solar Power Station (Block diagram):
In this system, sunlight energy is converted into electrical current with the help of solar cells. This system consists of solar cells, inverters and a substructure with which the solar cells are mounted on the roof surface.
Solar panel consists of many cells connected together to form an array.
As soon as sunlight hits the solar cells, a direct current is created in the silicone wafers of the cell. The direct current (DC) flows to an inverter that converts it to alternating current (AC) with a voltage of 230 volts.
Normally, 100% of the electrical energy thus produced is fed into the public power grid and sold to the local grid operator in terms of the Renewable Energy Act (EEG). Alternatively, power you produce yourself can also be consumed directly in the house.
Battery bank consists of many batteries to store electric energy generated during day time. This energy is used by during night. Electric meter is used to measure electric power consumed as well as electric power generated. It records difference between consumption and generation.
Maintenance of Solar cells:
Since a solar panel system needs to absorb energy from the sun, the most vital component of solar panel care is to keep the panels clean.
We can usually clean solar panel using the same equipment that we use to wash our residential and automobile windows.
Cleaning kit consists of liquid soap, wiper and brush.
Don't allow dirt and other environmental elements from settling on the panels for too long.
Solar panels generally require very little maintenance since there are no moving parts.
A few times a year, the panels should be inspected for any dirt or debris that may collect on them.
Standard solar panel maintenance is the best way to make sure they are always producing efficiently.
Keep track on how much energy is being produced by solar panel.
Questions
Marks wise Questions: 1M(2), 3M(2), 4M(1)
1. Fill in the blanks-
Solar cell works on ------------
----------cell is used for conversion of light energy into -------energy.
Amount of electric energy generated in solar cell depends upon ---- of incident of light.
-------- power generation protects environment.
Solar cell is also called-----------.
To increase the current rating of solar panel the cell array are connected in ---------.
Answers: 1. Photovoltaic effect 2. Solar, electric 3. Intensity 4. Solar
5. Photovoltaic cell 6. Parallel.
2. Answer the following.
With diagram explain the construction and working of solar cell. Draw its symbol.
Write a note on maintenance of solar cell.
State applications of solar cell.
Explain solar power station with block diagram.
Explain use of solar cell in street light.
