ملف كامل عن الطاقة الشمسية و وتطبيقاتها مع صور توضحية متحركة

ملف كامل عن الطاقة الشمسية و بالصور المتحركة

WHAT IS SOLAR ENERGY

energy from the sun and without its presence all life on earth would end. solar energy has been looked upon as a serious source of energy for many years because of the vast amounts of energy that are made freely available, if harnessed by modern technology.

A simple example of the power of the sun can be seen by using a magnifying glass to focus the suns rays on a piece of paper. Before long the paper ignites into flames.

This is one way of using the suns energy, but flames are dangerous and difficult to control. A much safer and practical way of harnessing the suns energy is to use the suns power to heat up water. 

A magnifying glass can be used to heat up a small amount of water. A short piece of copper tube is sealed at one end and filled with water. A magnifying glass is then used to warm up the pipe. Using more than one magnifying glass will increase the temperature more rapidly. After a relatively short time the temperature of the water increases. Continuing to heat the water will cause water vapour to appear at the top of the tube. In theory, with enough patience, several magnifying glasses and very strong sun light enough heat should be generated to boil the water, producing steam. This is one way of harnessing solar 

solar powered printing press. It used the energy of the sun to boil water, producing steam. The steam was used to drive a steam engine which provided the power to drive the mechanical printing press. The machine was unreliable and very expensive to manufacture. 

Modern solar panels are a combination of magnifying glasses and fluid filled pipes. The solar panel seen opposite has a glass front which is specially made to focus the power of the sun on pipes behind it. The pipes carry a special fluid that heats up rapidly. They are painted black to absorb the heat from the sun. The silver reflective surface behind the pipes reflects sun light back, further heating the pipes and the fluid they contain. The reflective surface also protects anything behind the solar panel (such as a roof).

The heat produced in the pipes is then used to heat a tank of water. This saves using electricity or gas to heat up the water tank

 

A BASIC HEAT EXCHANGER

The fluid filled pipe from the solar panel enters the water tank and coils round many times. The heat from the pipes is transferred to the water in the tank. A small device in the tank stirs the water to help with the transfer of the heat from fluid pipes

One common use of solar power is to heat domestic water. Although a typical system is expensive to buy, it pays for itself over a period of five to ten years. Also owning and using a system such as this shows that the owner is serious about saving energy and protecting the environment.

A typical solar water heating system is seen in the diagram below. The suns rays pass through the glass panel, warming the fluid pipes inside the unit. The pipes are painted black to ensure that they absorb as much heat as possible. The reflective silver surface behinds the pipes reflects heat back onto the pipes, further raising the fluids temperature.

The fluid pipes running through the solar panel are sealed and the fluid is pumped round the sealed system. The pipes run through the domestic water tank and the heat they carry is transferred to the water in the tank. The coil of pipes is called a ‘heat exchanger’.

Often solar panels (sometimes called collectors) are placed on the roof of a building where the sun’s rays are not blocked out by trees or other obstructions. Solar panels are quite expensive to manufacture and at the moment they are not widely used in countries such as the UK. Why do you think this is so

PARABOLIC SOLAR COLLECTORS

Solar power is energy from the sun. Although the sun is 150 million kilometres away it is still extremely powerful. The amount of energy it provides for the earth in one minute is large enough to meet the earth’s energy needs for 

one year. The problem is in the development of technology that can harness this ‘free’ energy source

Solar collectors are one way of focussing the suns rays to heat up fluids. A typical array of solar collectors is seen opposite. They are basically unusually shaped mirrors (parabolic in shape) that focus the heat of the sun on a pipe carrying a special fluid. The temperature of the fluid in the pipe increases as it flows down the pipe, along the solar collectors. The pipe extends the entire length of the mirrors.

This type of set up works at its best in desert areas where there is no shortage of sunlight and very little cloud. 

The hot fluid in the pipe can be used, through a system of heat exchangers, to produce electricity or hot water

The special fluid inside the pipes can be replaced with water. The concentrated heat from the parabolic collectors turns the water into steam. The jet of steam is used to turn turbines producing electricity. This system works well in desert regions due to the hot climate.

the photographs show an arrangement of parabolic solar collectors. Notice the 

suns energy is focused on the 

water pipe at its centre

A SOLAR FURNACE

The picture below shows the parabolic reflector of the Odeillo-Font-Romeau Solar Furnace in France. 63 flat mirrors automatically track the sun and concentrate the light on a reflector. The reflector then concentrates the rays to produce 1000 kilowatts and a temperature of 33,000degrees centigrade. This is used to power a furnace 

producing steel from iron ore.

The production of steel or aluminium requires very large amounts of energy. This is normally provided by electricity, gas or fossil fuels. The solar furnace relies on the power of the sun. The picture below shows how the sun’s rays are focussed on the crucible holding the ore. The ore is heated to a very high temperature until it becomes molten, then it is poured. Pollution is kept to a minimum as solar power is a clean source of energy.

1. Design another industrial application of a parabolic collector system. For example, the system could be used to produce electricity for a remote farm OR produce hot water for [a public bathing area

WHAT IS PHOTOVOLTAICS

Photovoltaic cells look similar to solar panels but they work in a different way. Solar panels are use to produce hot water or even steam. Photovoltaic panels convert the sunlight directly into electricity. A typical example of a device powered by photovoltaic cells is a solar powered calculator. This type of device only needs a small amount of electrical power to work and can even be used in a room with artificial light (bulbs / fluorescent light).

Although we see photovoltaic cells powering small devices such as calculators they have a more practical application especially in the third world. Photovoltaic cells have been developed that will provide electrical power to pump drinking water from wells in remote villages. British Telecom have developed a system that can be used to power a radio telephone system. During the day the cells power the phone and also charge batteries. The batteries power the phone during the night. Often photovoltaic cells are used as a backup to conventional energy. If conventional fails the cells are used to produce electricity.

A TYPICAL PHOTOVOLTAIC CELL Silicon is a material known as a ‘semiconductor’ as it conducts electricity and it is the main material for photovoltaic cells. Impurities such as boron or phosphorus are added to this base material. These impurities create the environment for electrons to be freed when sunlight hits the photovoltaic panel. The 

freeing of electrons leads to the production of electricity

The diagram above shows a basic photovoltaic cell. The blue represents the main material, silicon. The black round and irregular shapes represent the impurities of boron or phosphorous. As the sun/light strikes the cell the impurities free up electrons which ‘bounce’ around at incredible speeds. This creates an electrical charge.

AN ARRANGEMENT OF PHOTOVOLTAIC PANELS - ARIZONA (USA)

1. Make a list of devices that are powered by photovoltaic cells.

2. Describe devices that you think could be powered by photovoltaic cells (fully powered or as a backup to the 

PRACTICAL APPLICATIONS OF PHOTOVOLTAICS

In the example shown below photovoltaic panels are used to produce electricity which powers a water pump, pumping drinking water from a well. This is especially useful in agriculture and in the third world where wells can be extremely deep. The power produced by the photovoltaic panels is also used to power a purification system, cleaning the water, removing dangerous impurities and harmful bacteria. 

When not being used to pump water, the electricity can be stored in batteries so that the pump can be used at 

night

The phone box seen opposite is powered directly by photovoltaic cells during the day. The batteries are also charged during sun light hours. 

This type of communication system is ideal for remote areas where electricity from the power grid is not available. They have been tested in third world countries and have proved successful. However, the priority for most third world countries is to ensure that people in remote areas have clean drinking water rather than Hi-Tech communication systems.

In industrial / developed countries photovoltaic cells are used to power automatic weather stations. Next time you drive down a motorway / highway watch out for photovoltaic systems as they are sometimes used to power electronic systems measuring traffic congestion and traffic flow.

The photovoltaic panel is being placed on the roof of a single story house in a village in Africa. The panel will provide enough electrical power for a phone. This is the only phone for a radius of 100 miles. It is an essential tool of communication for the whole village as well as the surrounding area.

QUESTION:

1. With the aid of diagrams and notes, describe a new way in which photovoltaic cells could be used to provide

ADVANTAGES AND DISADVANTAGES OF SOLAR POWER

1. Solar energy is free although there is a cost in the building of ‘collectors’ and other equipment required to convert solar energy into electricity or hot water.

2. Solar energy does not cause pollution. However, solar collectors and other associated equipment / machines are manufactured in factories that in turn cause some pollution.

3. Solar energy can be used in remote areas where it is too expensive to extend the electricity power grid.

4. Many everyday items such as calculators and other low power consuming devices can be powered by solar energy effectively.

5. It is estimated that the worlds oil reserves will last for 30 to 40 years. On the other hand, solar energy is infinite (forever)

.

1. Solar energy can only be harnessed when it is daytime and sunny.

2. Solar collectors, panels and cells are relatively expensive to manufacture although prices are falling rapidly.

3. Solar power stations can be built but they do not match the power output of similar sized conventional power stations. They are also very expensive.

4. In countries such as the UK, the unreliable climate means that solar energy is also unreliable as a source of energy. Cloudy skies reduce its effectiveness.

5. Large areas of land are required to capture the suns energy. Collectors are usually arranged together especially when electricity is to be produced and used in the same location.

6. Solar power is used to charge batteries so that solar powered devices can be used at night. However, the batteries are large and heavy and need storage space. They also need replacing from time to time. QUESTIONS:

1. What is your opinion of solar energy ?

2. Do you think solar energy will answer the worlds energy crisis ?

3. Does solar power cause any pollution or damage to the environment ?

4. Research the internet to find information / pictures on unusual solar powered devices. Present this information using software of your choice.

5. What devices in the future will be solar powered ? Explain your reasoning.

6. Draw a rich picture with SOLAR ENERGY at its centre. List associated words / themes around this main theme.

http://www.almohandes.org/vb/showthread.php?t=65153