My Science School

        The wind is a major source of renewable energy that is also useful to generate power. You must have seen windmills in real life, or on television. They are set up on farms for power generation.

        Although they look like fans, windmills work in just the opposite way. In fans, electricity is used to make wind, but in windmills, wind is used to make electricity.

        Let’s see how they work. When the wind blows, it turns the blades of the windmill. This in turn, spins a generator inside, and produces electricity.

         A single windmill can generate only a small amount of electricity. Hence, power companies build wind farms with a large number of wind turbines.

        In many countries including Denmark and Portugal, wind power contributes largely to power production.

        Yet another form of energy comes from ocean tides, which again, can be used to produce electricity. Just like wind turbines, there are tidal turbines too. They are turned by ocean currents. The spinning turbines are connected to devices that generate electricity.

         Here again, the process and products are safe, as there are no harmful emissions made.

 

As the name suggests, solar power plants use sunlight for power production. There are two different technologies used for solar power production these days- using photovoltaic plants and solar thermal systems.

Photovoltaic cells, or PV cells, produce electric current when exposed to light. They are also called solar cells. They contain silicon, a naturally occurring element found in sand. When sunlight hit silicon, there happens a chemical reaction. As a result, electrons move, and electric current is produced. A group of PV or solar cells create a solar panel. A number of solar panels form a solar array, and they generate solar energy.

In solar thermal systems, sunlight is collected and concentrated to produce high temperature heat that is needed to generate electricity. All the systems have solar energy collectors with two components - a ‘reflector’ that captures and focus sunlight onto the ‘receiver’. In the system here, a heat transfer liquid is heated and circulated in the receiver. It is used to produce steam. The steam is then converted to mechanical energy in a turbine, which powers a generator to produce electricity.

          Electric power transmission means the transfer of electric power from one place to another in large quantities.

           Typically, this happens between a power plant and a substation situated near a populated area. A substation is where voltage is transformed from high to low or vice versa using transformers. When power is transmitted from substations to consumers, the process is called power distribution. Normally, transmission takes place at very high voltage, like 110 kV or above. This is, because of the large amount of power involved in this.

            Over long distances, electricity is transmitted through overhead power transmission lines. But in places that are environmentally sensitive, or where there is very high population, transmission takes place underground. They have high installation cost and operational limitations, yet their maintenance cost is lower.

               The network of power stations, transmission lines, and substations is together known as a transmission grid. 

        From the moment power is generated in a plant, it goes through various stages before reaching our homes.

         Let’s see how power travels. From the electricity generating plants, current is sent through transformers to increase the voltage, so that it can be pushed longer distances.

         Electric power then reaches a substation. Here, the voltage gets lowered, so that it could be sent to smaller power lines.

         From there, it travels through various distribution lines, and reaches your neighbourhood where smaller transformers reduce the voltage, so that you can take safe power to your homes.

        From the transformer, power is carried through service drops, or smaller overhead electrical lines to your homes. It also passes through the ‘meter’ installed in the house that can measure how much power is used by the family.

        The current moves straight to the service panel, where fuses protect the wires inside the house from overloading. Keep in mind that children should never touch this panel!

         It is from here that power finally moves to the switches and outlets all over the house.

 

       Overhead power lines are structures for electric power transmission and distribution across large distances. They also make the cheapest method for transmitting power.

         In usual cases, overhead power lines have one or more conductors suspended by towers. One of the major duties of these power lines is to maintain enough space or clearance between these energized conductors and the ground, in order to avoid danger.

           These days, power lines can be operated at voltages of 765,000 volts or even more, between conductors. Depending on their range of voltages, overhead power lines can be classified as low voltage, medium voltage, high voltage, extra high voltage, and ultra high voltage.

              However, these power lines are extremely dangerous, and one has to keep a safe distance from them. Unlike household power cords, overhead power lines are not insulated. Even if it looks like insulation, it might be a weatherproofing material. 

       A transformer is an electrical device that transforms electricity from high to low voltage and vice versa. It is an important component for power transmission. Let’s get to know why.

       We saw the process through which electric power reaches our homes. When electricity travels from a power plant, it comes in a very high voltage. This is because the voltage from the plant is ‘stepped up’ by transformers before they are transmitted.

       The voltage has to be increased because electric power has to travel very long distances, and that too, with minimal loss of energy. We should know that energy is lost in the process of power transmission. But if the voltage is high, energy loss would be low.    

        But do our homes need this kind of voltage? Absolutely not! Before the power reaches houses, the voltage has to be lowered, or stepped down. This is where transformers again become important. They step down voltage from high to low. 

         Electric meters are devices that we commonly see in houses and offices. They are used to measure the total electrical energy consumed by the appliances in a house or office. The devices are installed by the electric power company that supplies electricity.

          If you take a close look at these meters, you can see a few digits. They denote the number of units of electricity that has been consumed so far. Our electricity bill depends totally on this reading.

          There are different types of electric meters available in the market. One is the electro-mechanical meter, which is most commonly used in our country. It has a magnetic metallic disc attached, which rotates, depending on the power passing through it. The rate of this rotation decides the reading on the meter.

          Then there are electronic meters that are popular in cities. In these, readings appear digitally on the display fixed on the meter.

          The newest in this league is the smart meter. They are electronic meters, but they have an added advantage. These smart meters are connected back to the utility (which provides us electricity) through the internet. Hence, no official will have to come in person and take the readings. The readings are sent through the internet, which makes the job easier. 

Electric power is always represented in terms of watts (W) or kilowatts (kW). A thousand watts together make a kilowatt.

Watts describe the rate at which electricity is consumed during a specific period. Take the case of a 15-watt LED bulb. It draws 15 watts of power at any moment when turned on.

Let’s look at other examples to understand the concept better. The power rating of a typical incandescent light bulb used in houses is between 25 to 100 watts. To produce a similar amount of light, fluorescent lamps consume 5 to 30 watts, and LED lamps use 0.5 to 6 watts.

Coming to power stations, a typical power station that uses coal to generate electricity produces around 600 to 700 megawatts. A megawatt is equivalent to one million watts! The term ‘watt’ was named after James Watt who developed the steam engine. Watt-hour is quite different from a watt. It is a measure of electrical energy equivalent to a power consumption of one watt for one hour.

 

      Short circuit is a term we hear often, and it is something that is dangerous, for sure. Let’s see what exactly a short circuit is.

       It is a problem that arises when two or more wires in an electrical circuit, that are not supposed to come in contact, touch each other. This action is immediately followed by a very high current flowing through the circuit. This can result in a lot of dangers, like sudden fire, destruction of the components in the circuit, or melting of insulation. Sometimes there can also be an electrical explosion, or what is known as an ‘arc flash’.

            Scary, isn’t it? However, there are fault protection devices like circuit-breakers and fuses that can detect a short circuit. 

          As we saw earlier, a fuse is a device that is provided in an electrical circuit to protect the appliances connected to it from damage. It is a safety tool that limits current in a circuit.

          Structurally, a fuse is a short piece of wire made up of elements like zinc, copper, silver, aluminium, which have high resistance, and a low melting point. In case of overheating due to excess current, the fuse tends to melt and separate. It thus prevents fire outbreaks and also protects humans from electric shock.

           Fuses, in general, are used in all types of electrical and electronic applications.

            Depending on their uses, there are different types of fuses available. One is the cartridge fuse, which is used to protect electrical appliances like motors, air-conditioners, refrigerators, pumps etc., where high voltage rating and currents are required.

           Then there are blade type fuses that come in a plastic body with two metal caps, to be fitted in a socket. These fuses are mostly used in automobiles for wiring and protection from short circuit.

           Another category is of reset-table fuses. They can be used multiple times without being replaced. Such fuses are seen in nuclear systems, or in aerospace systems.

       Telegraphy, a technology developed in the early 18th century, revolutionized long-distance communication. It was a simple electrical circuit that transmitted electric signals over a wire, between stations.

        Through the telegraph lines, messages could be sent back and forth as bursts of electricity. It was the connection between electricity and magnetism that led to this path-breaking invention.

           By the end of the 19th century, another invention surfaced - the telephone. It was a different and advanced device that improved communication between long distances. In a telephone, an electric current carries the sound. Here again, the invention followed the principle of electromagnetism.

          Another important device that works on the same principle is the loudspeaker. It converts an electrical signal from devices like a radio, or television into sound. For this purpose, the signals have to be connected to an electronic amplifier.

         Generally, a loudspeaker is built using a coil of thin copper wire, a still paper cone and a circular magnet. When electrical signals are passed through, the coil of copper wire moves back and forth. This, along with the magnet, causes the paper cone to vibrate and reproduce sounds.

          Taking into consideration the above mentioned devices, as well as other equipment, one can say that no invention in recent times has been complete without electricity. 

          The electrical sector of any country in the world depends mainly on its economic system, and policies adopted by its government.

          Hence, the whole process of power production and transmission in a country need not be the same as others. In some of them, generation, transmission and distribution of electricity are done by a government controlled organization. But in some others, privately owned companies will have shares too.

         Just like the operation, the voltage and frequencies for providing electrical power to appliances too, differ from country to country.

 

Continue reading "Why is it said that electricity distribution is different in every country? "

        The power sector of India is known to be one of the most diversified and powerful ones in the world. Sources of electricity generation here include conventional sources like coal, natural gas, oil, lignite, hydro and nuclear power, and also non-conventional sources like solar, wind, agricultural and domestic waste.

        The country has witnessed a very fast growth in electricity generation since 1990. In the year 2015, the country became a power surplus nation that possessed huge electric generation capacity. But many villages in India do not have power connection even now.

        By mid-2016, India’s power generation capacity crossed the 300,00 MW (megawatt) mark, including more than 42,848 MW renewable energy sources such as solar and wind power plants. This means, the country’s renewable energy sector is considered very important.

         About 65 per cent of the electricity produced in India is from thermal power plants. More than 20 per cent of the power comes from hydroelectric power plants and 3 per cent from nuclear plants. The rest is from alternate sources. 

          A power grid refers to an interconnected network for distributing electricity to consumers.

          It was in the 1960s that India began utilizing the grid management system on regional basis. The power grid system was then geographically divided into five regions for better management. These regions are - northern, eastern, western, north eastern and southern grids.

          They were established to enable the transmission of surplus electricity between states in each region.

          Towards the 1990s, the Indian government started planning for a national grid. As a result, the above mentioned regional grids were interconnected.

          In October 1991, the first interconnection was made, between the north eastern and the eastern grids. A few years later, in 2003, the western grid got connected with the above. This process followed in the later years as well. The northern grid was also interconnected in August 2006.

          In December 2013, the remaining grid- southern was connected to the central grid in a synchronous mode. Thus, the aim to build ‘One Nation - One Grid - One Frequency - was achieved.

           There are many reasons why renewable energy is important for the world and its future.

            The main advantage of these energies is that they are free of pollution. Renewable resources are way cleaner than fossil fuels because they don’t produce toxic wastes.

             Next, the reserves of these energies are never ending unlike coal, gas, oil or nuclear sources. Hence, they’re named renewables!

             Power production from fuels and other non-renewables demand a large-scale import of these resources at high prices. Also, their cost depends on the international market. In the case of renewable resources, it’s not needed as most of the energies depend on the Sun.

              There are many countries that depend largely on renewable resources. For instance, Denmark, UK, Scotland and Ireland make great use of wind energy.

              Denmark, which has been a pioneer in the field, gets around 42 per cent of its power from wind plants.

              And there are countries like China, and India that use of hydro power for electricity, which is equally safe.