What is electricity

Electricity is a form of energy. Electricity is the flow of electrical power. All matter is made up of atoms, and an atom has a center, called a nucleus. The nucleus contains positively charged particles called protons and uncharged particles called neutrons. The nucleus of an atom is surrounded by negatively charged particles called electrons. The negative charge of an electron is equal to the positive charge of a proton, and the number of electrons in an atom is usually equal to the number of protons. When the balancing force between protons and electrons is upset by an outside force, an atom may gain or lose an electrical charge. When charges are "lost" from an atom, the free movement of these electrical charges constitutes an electric current.

An electric generator is a device for converting mechanical energy into electrical energy.  The process is based on the relationship between magnetism and electricity. When a wire or any other electrically conductive material moves across a magnetic field, an electric current occurs in the wire. The large generators used by the electric utility industry have a stationary conductor. A magnet attached to the end of a rotating shaft is positioned inside a stationary conducting ring that is wrapped with a long, continuous piece of wire. When the magnet rotates, it induces a small electric current in each section of wire as it passes. Each section of wire constitutes a small, separate electric conductor. All the small currents of individual sections add up to one current of considerable size. This current is what is used for electric power 

 
How hydraulics power plant works

 The basic concept of electricity generation is by transforming mechanical energy to electric energy.

Actually, hydroelectric power plants produce electricity by using the power of a floating water turn  piece called turbine, which then turns a metal shaft in an electric generator which is the motor that produces electricity.

The theory is to build a dam on a large river that has a large drop in elevation. The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, the water strikes and turns the large blades of a turbine, which is attached to a generator above it by way of a shaft. As the turbine blades turn, so do a series of magnets inside the generator. Giant magnets rotate past copper coils, producing alternating current (AC) by moving electrons

How fuel cell works

 A fuel cell is an electrochemical energy conversion device that converts hydrogen and oxygen into water, producing electricity and heat in the process. It is very much like a battery that can be recharged while you are drawing power from it. Instead of recharging using electricity, however, a fuel cell uses hydrogen and oxygen.

A fuel cell provides a DC (direct current) voltage that can be used to power motors, lights or any number of electrical appliances. There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by the type of electrolyte they use.

The proton exchange membrane fuel cell (PEMFC) uses one of the simplest reactions of any fuel cell. First, let's take a look at what's in a PEM fuel cell

• The anode, the negative post of the fuel cell, has several jobs. It conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. It has channels etched into it that disperse the hydrogen gas equally over the surface of the catalyst.
• The cathode, the positive post of the fuel cell, has channels etched into it that distribute the oxygen to the surface of the catalyst. It also conducts the electrons back from the external circuit to the catalyst, where they can recombine with the hydrogen ions and oxygen to form water.
• The electrolyte is the proton exchange membrane. This specially treated material, which looks something like ordinary kitchen plastic wrap, only conducts positively charged ions. The membrane blocks electrons.
• The catalyst is a special material that facilitates the reaction of oxygen and hydrogen. It is usually made of platinum powder very thinly coated onto carbon paper or cloth. The catalyst is rough and porous so that the maximum surface area of the platinum can be exposed to the hydrogen or oxygen. The platinum-coated side of the catalyst faces the PEM.

  The catalyst splits  into two H+ ions and two electrons (e-). The electrons are conducted through the anode, where they make their way through the external circuit (doing useful work such as turning a motor) and return to the cathode side of the fuel cell.

  Meanwhile, on the cathode side of the fuel cell, oxygen gas (O2) is being forced through the catalyst, where it forms two oxygen atoms. Each of these atoms has a strong negative charge. This negative charge attracts the two H+ ions through the membrane, where they combine with an oxygen atom and two of the electrons from the external circuit to form a water molecule (H2O).

  This reaction in a single fuel cell produces only about 0.7 volts. To get this voltage up to a reasonable level, many separate fuel cells must be combined to form a fuel-cell stack.

  PEMFCs operate at a fairly low temperature (about 176 degrees Fahrenheit, 80 degrees Celsius), which means they warm up quickly and don't require expensive containment structures. Constant improvements in the engineering and materials used in these cells have increased the power density to a level where a device about the size of a small piece of luggage can power a car.

   

  Chemistry of a Fuel Cell

  Anode side:
  2H₂ => 4H⁺ + 4e^-

  Cathode side:
  O₂ + 4H⁺ + 4e^- => 2H₂O

  Net reaction:
  2H₂ + O₂ => 2H₂O

How thermal power plant works

The major idea for electricity generation is to transform the mechanical into electrical energy.

Modern steam power plants consist of a large boiler that burns wood, coal, oil or natural gas to make heat. Running through the fire box and above that hot fire are a series of pipes with water running through them. The heat energy is conducted into the metal pipes, heating the water in the pipes until it boils into steam. Water boils into steam 100 degrees Celsius. The high temp and pressure steam hit a turbine and generate a rotational move; the turbine is attached to the generator by a shaft which produces electricity

 
How Nuclear power plant works

   A nuclear power plant is not all that different from coal, oil or gas fired plants. The main difference is that at a nuclear power plant, the heat used to make steam is produced by fission. Fission is the splitting of atoms into smaller parts. Atoms, themselves tiny, split when they are struck by even smaller particles, called neutrons. Each time this happens, more neutrons come out of the split atom and strike other atoms. This process of energy release is called a chain reaction. The plant controls the chain reaction using both boron and control rods to keep it from releasing too much energy too fast. Adding boron to the water and inserting control rods into the reactor vessel control the fission process by absorbing neutrons. In this way, the chain reaction can go on for a long time.

What radio active means

   Few natural elements have atoms that will split in a chain reaction. When an element contains atoms that split, it is said to be "radioactive." Iron, copper, silver and many other common metals are not radioactive. But uranium is. So uranium is suitable to fuel a nuclear power plant. The plant shields uranium from contact with the environment because radioactivity can be dangerous.

Heat makes it work

   As atoms split and collide, they heat up. The plant uses this heat to create steam. The pressure of the expanding steam turns a turbine which is connected to a generator.

 Getting a charge out of it

   After the steam is made, a nuclear plant operates much like a fossil fuel fired plant: the turbine spins a generator. The whirling magnetic field of the generator produces electricity. The electricity then goes through wires strung on tall towers you might see along a highway to an electrical substation in your neighborhood where the power is regulated to the proper strength. Then it goes to your home so you can do homework on your computer, watch television, play video games or have a cold snack from your refrigerator.

 

Clean air

   One of the greatest benefits of nuclear plants is that they have no smoke stacks! The big towers many people associate with nuclear plants are actually for cooling water used to make steam. (Some other kinds of plants have these towers, too.) The towers spread the water out so as much air as possible can reach it and cool it down. Most water is then recycled into the plant. The puffs you see coming out of a cooling tower are just clouds of water vapor.