Electricity and electrical power. What is it?

Electricity and electrical power. What is it?

Civilization relies on electricity daily, and we think of it mainly as a stream of energy flowing through the wiring to power outlets that allows us to light our homes or cook our meals. What is electricity, and where does it come from? In this article, we'll examine the basic concepts and units of measurement and reveal how to produce electricity.

Electricity and electrical power symbol

What are electrical energy and electric power?

So, like a barrel of oil, "energy" is a quantity. Although there are several units for measuring energy, the joule is arguably the most often used.

One newton of force applied through one meter produces one joule of work. 

Illustration of 1 joule

For a practical example, it takes about 1 Joule of energy to lift an apple one meter.

Whether thermal, light, or electrical energy, energy generally enables us to do particular work. In the case of electricity, this is electrical work: charging an electric car, lighting a torch, or providing lighting for an entire city. To understand how electricity works, let's explain the basic concepts.

Electric power indicates a quantity of energy used over time since it represents the rate at which that beneficial work is accomplished. The Watt is the accepted unit of power. Therefore, a 60 Watt light bulb uses 60 Watts, which is equivalent of 60 Joules per second.

Electric power, as we think of it, is the product of two components:

  • The flow of electrons through a conducting material, such as copper wire, is known as current (I), and it is measured in amperes (A), also known as "amps." Current can be compared to the quantity of liquid moving through a pipe or hose.
  • A measurement of the electric potential between two terminals is voltage (V). Voltage is not a "natural" unit of measure; instead, it is equal to the power-to-current ratio. Voltage can be compared to the pressure in a pipe or hose. The liquid will flow through the pipe quickly if there is a significant pressure difference between the two ends of the pipe. The fluid will move slowly through the pipe if there is a little pressure differential. No liquid flows at all if the pressure difference is precisely zero.

Thus, power, as we think of it, is really:

Power (P) = Voltage (V) × Current (I)            

= Volts × Amps              

= Watts

What is electrical power?

What is the difference between electrical energy (Wh) and power (W)?

The energy exchange trades electrical energy, not electrical power. How to distinguish one from another?

Electric power, measured in Watts, refers to the rate of flow of electricity. Electricity-powered appliances like light bulbs and toasters typically take control from the electric grid measured in Watts. Watts are frequently used to calculate an electrical production capability of a power plant. Finally, we frequently use the Watt unit to represent the electricity movement via transmission lines. Therefore, a power plant's capacity equals the greatest instantaneous rate at which it can produce energy.

On the other hand, electric energy refers to the entire quantity of electricity used over a certain amount of time. We encounter it in everyday life as an electricity consumption expressed in watt-hours.

Here are the most commonly used metric units for energy: 

  • One kilowatt (kW) is one thousand watts, and one kilowatt-hour (kWh) is one thousand watts-hours.
  • One megawatt (MW) is one thousand kilowatts, and one megawatt-hour (MWh) is one thousand kilowatt hours (also one million W/Wh).

It often needs to be clarified whether MW or MWh are the correct units. The power plant produces electricity at a rate of 4 MW. The total amount of electric energy it generates in one hour is 4 MWh; in 30 minutes, it produces 2 MWh. The "hour" has been used as the standard unit of time for measuring electric energy, which causes misunderstanding. The "hour" in MWh is a code term for a quantity (like a barrel of oil).

Here is an example in practice:

  • A generator produces 4 MW of power continuously for three hours.
  • The total electric energy output for this power generator during these 3 hours would be:

4 MW × 3h = 12 MWh

Chart showing constant power in MW
4 MW of constant power for three hours

How is electricity generated?

Simply put: we all have the same energy, electricity, in our sockets, but how it is produced can vary. Electricity, in the form of use, does not exist by itself. We must obtain electricity by converting other forms of energy through power stations, which convert primary energy into mechanical, light, or thermal energy.

The so-called primary energies include renewable energies (solar, wind, hydro, geothermal, biomass) and non-renewable energies, i.e., fossil resources (coal or oil). These are converted into electricity, i.e., secondary power, using photovoltaics, generators, and the like.

In Europe, we mainly see these types of power plants:

  • nuclear power plants
  • steam power plants
  • steam and gas-fired power stations
  • fossil fuel-fired combustion ('thermal') power stations
  • hydroelectric and pumped storage power plants
  • geothermal power plants
  • photovoltaic power plants
  • wind power plants
  • biomass and biogas production
  • combined heat and power generation

Once the electricity is generated, it enters the grid, which is the network of transmission lines and substations that transport electricity to homes and businesses - but before that, energy is traded between buyers and sellers on the electricity market. Each power plant has a different production cost, determining the price at which they sell its electricity to the market. The energy market is a complex system that involves many players, including generators, distributors, and retailers. To learn more about the electricity market, check out our article "Understanding the Electricity Market: A Comprehensive Guide."

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