What Is The Flow Of Electricity Generation?

Electricity generation is the process of generating electric power from primary energy sources. The overall process can be divided into several major steps that convert raw fuel sources into usable electricity for homes, businesses, and industries.

It all starts with extracting fuels like coal, natural gas, uranium, or renewable sources like wind, solar, and hydropower. These raw fuels then go through preprocessing steps to convert them into a form suitable for electricity generation. The preprocessed fuel is then burned or undergoes a chemical reaction in a generator to convert the fuel’s energy into mechanical power. This mechanical power spins a turbine that is connected to an electrical generator to produce electricity.

The generated electricity is then stepped up to high voltages for efficient transmission over long distances through transmission lines and towers. Near the end users, the transmission voltage is stepped down at substations and distributed locally at lower voltages through the distribution grid. The end users consume the distributed electricity to power homes, buildings, factories, and more. Any excess electricity can also be stored using large-scale batteries or other energy storage methods.

While electricity improves modern life, its generation can also have environmental impacts. Steps are often taken to minimize pollution and carbon emissions during the electricity generation process through regulations, efficiency improvements, and emission controls.

This overview summarizes the multi-step process that converts raw energy sources into usable electricity for society. The following sections will examine each step of this important process in greater detail.

Table of Contents

Fuel Extraction

The first step in electricity generation is extracting the fuel source. The most common fuels used for electricity generation are:

Coal – Coal is a fossil fuel extracted through mining. Coal can be mined from underground mines or surface mines.
Natural gas – Natural gas is extracted by drilling gas wells into gas reservoirs. Natural gas is often found with crude oil deposits.
Uranium – Uranium is mined from underground or open pit uranium mines. Uranium ore is extracted and processed into uranium fuel for nuclear reactors.

Petroleum – Crude oil and petroleum products like diesel and heavy oils are extracted from underground reservoirs through oil wells and drilling.
Renewables – Renewable energy comes from naturally replenished sources. Common renewable fuels are biofuels, hydropower, wind, and solar.

The fuel type determines the electricity generation method. Each fuel has advantages and disadvantages in cost, efficiency, sustainability, and environmental impact.

Fuel Preprocessing

Most fuels used for electricity generation require preprocessing before they can be burned efficiently in power plants. This involves cleaning and preparing the fuels through various methods:

Coal is crushed and screened to achieve the desired size for combustion. Impurities like rocks and dirt are removed via washing and gravitational separation. Preprocessing reduces ash content and increases the heating value of coal.

Natural gas contains impurities like water, hydrogen sulfide, carbon dioxide, and mercury that must be removed. Gas processing systems use absorbers, membranes, and sulfur recovery units to purify natural gas before it enters pipelines.

Biomass like wood and agricultural waste is shredded into uniform chips or pellets for co-firing with coal. Densification via pelletization facilitates handling, storage, and transportation.

Petroleum fuels including fuel oil and diesel undergo fractional distillation and cracking to isolate usable fractions. Desulfurization removes sulfur compounds that would produce air pollution.

Combustion

Combustion is a key step in the electricity generation process where chemical energy stored in fuels like coal, natural gas, or biomass is converted into heat energy. This occurs through the burning or oxidation of the fuel source. Oxygen in the air combines rapidly with the carbon and hydrogen in the fuels in an exothermic chemical reaction, releasing heat. The fuels do not spontaneously combust, but require an ignition source and input of oxygen to start and sustain the combustion. The amount of heat released depends on the calorific value of the fuel.

The combustion process takes place in a contained chamber like a boiler or combustion turbine. Here the air and fuel are mixed intimately to enable efficient burning. The heat of combustion is transferred to water pipes or engine components, which convert the heat into mechanical energy and eventually electrical energy. Controlling the combustion process is critical to maximize efficiency while minimizing harmful emissions. Proper ratios of fuel and air must be maintained, along with sufficient turbulence for mixing, and temperatures high enough for combustion but low enough to avoid material failures.

Heat Transfer

The heat generated from the combustion of fuel must be captured and transferred to boil water into steam. This is done through heat exchangers that transfer the heat from the combustion gases to water pipes containing high-pressure water. As the water absorbs the heat, it starts to boil and turn into high-pressure steam.

This high-pressure steam then moves into a separate section of pipes and vessels known as the steam circuit. The steam circuit transports the steam to the turbine component. As the high-pressure steam moves through the turbine blades, it causes the turbine to spin. This spinning turbine converts the heat energy from combustion into mechanical energy.

The steam then exits the turbine blades into a condenser unit. The condenser cools the steam back into water so that it can be pumped back to the heat exchanger to repeat the cycle. This process of heating, boiling, spinning the turbine, and condensing the steam into water again is known as the Rankine cycle – the fundamental concept used in most electricity generating plants powered by coal, nuclear, natural gas, biomass, and concentrating solar power.

Electricity Generation

The most common method for generating electricity is through electromagnetic induction, which uses the principles of magnetism and motion. This process involves turbines that are spun by the kinetic energy of steam, water, wind or other sources. The turbine is connected to a generator comprised of conductors surrounded by magnets. As the turbine spins the generator, it causes the conductors inside to rotate through the magnetic field, inducing a flow of electrons and creating AC electricity.

The generator contains a rotor attached to the turbine shaft that rotates within a stator that produces the magnetic field. As the rotor spins, it generates a changing magnetic field around the stator which induces voltage and current. The electricity is then channeled and regulated before being sent to transformers to increase the voltage for efficient transmission over power lines. Generators can utilize electromagnets or permanent magnets depending on the design. Larger power plants tend to use electromagnets made of coiled wire that become magnetic when current flows through them. The electricity generation process continues to be refined for greater efficiency, reliability and sustainability.

Electricity Transmission

After electricity is generated at power plants, it needs to be transported long distances to homes, businesses and other end users. This is done through electricity transmission infrastructure such as high voltage power lines. Electricity is stepped up to very high voltages like 115 kV or 500 kV for efficient transmission over long distances via overhead transmission lines or underground/underwater cables.

Using high voltages reduces electricity losses since less current is required to transmit a given amount of power. Transmission systems interconnect different generating plants and allow multiple sources to feed into the grid. Transformers are used to step up voltage at the generating end and step down voltage closer to end users.

Transmission systems must be carefully controlled and monitored to maintain voltage, frequency and power flow stability. Advanced technologies like real-time monitoring, automation and FACTS devices help optimize transmission system operation. Overall, electricity transmission is critical for delivering electricity from power plants to load centers over long distances.

Electricity Distribution

The step after electricity transmission is distribution, which involves carrying electricity to end-use customers. Electricity enters a distribution substation and transformer where voltage is stepped down again before being sent through distribution lines across an interconnected grid of streetlight circuits, residential circuits, commercial circuits, and industrial circuits.

The local distribution grid consists of lower voltage lines and substations that deliver electricity to homes, businesses, schools, and other end users. Distribution lines carry electricity from the transmission system and regional substations to neighborhood transformers located near homes and businesses.

Transformers on the poles and underground further reduce electricity to the proper voltage for use in homes or buildings. From the transformer, power travels over service drop lines to the customer’s service entrance equipment and into the home’s internal wiring to be used for lighting, appliances and devices. Protective devices like fuses are installed at various points to help prevent power surges and short circuits.

Utility companies own and maintain the distribution grid up to and including the home’s meter. Anything past the meter into the home’s electric panel and outlets is the customer’s responsibility. Smart meters for two-way communication have also been installed by many utilities to enable better monitoring and management of electricity distribution.

Energy Storage

Excess electricity that is generated can be stored for later use during periods of high demand. This helps balance electricity supply and demand. Common ways to store electricity include batteries, pumped hydro storage, compressed air energy storage, flywheels, and supercapacitors.

Batteries are one of the most widely used forms of energy storage. They convert electricity into chemical energy and then convert it back to electricity when needed. Lithium-ion batteries have become popular for grid-scale energy storage due to their high energy density, low self-discharge, and low maintenance requirements. Flow batteries like vanadium redox are also gaining popularity for utility-scale applications.

Pumped hydro storage accounts for around 95% of all utility-scale electricity storage worldwide. It works by using excess electricity to pump water uphill into a reservoir. When electricity is needed, the water is released to run downhill through turbines that generate electricity. This is a mature technology but requires specific geographic conditions.

Compressed air energy storage compresses air in an airtight underground cavern using cheap excess electricity. The pressurized air is then released to drive a turbine and generate electricity when required. Flywheels and supercapacitors can also store electricity through mechanical and electrostatic means respectively. Overall, energy storage enables greater flexibility and efficiency in electricity grids.

Environmental Impacts

The process of generating electricity from fossil fuels like coal and natural gas has significant environmental impacts. Most notably, burning these fuels produces air pollutants like carbon dioxide, nitrogen oxides, sulfur dioxide, particulate matter, and mercury. This leads to problems like acid rain, smog, respiratory illnesses, and climate change.

Fossil fuel power plants are the largest emitters of greenhouse gases like carbon dioxide, which trap heat and warm the planet. This contributes to global climate change, leading to problems like rising sea levels, extreme weather, ecosystem damage, and more. Coal power plants are especially carbon-intensive.

Other environmental effects come from mining and drilling for fuels. Coal mining can pollute waterways and lead to deforestation. Fracking for natural gas uses a lot of water and has been linked to groundwater contamination. Nuclear power avoids emissions, but carries risks of accidents and radioactive waste. Overall, the lifecycle impacts of electricity generation are major environmental concerns.