What is energy? By definition, energy is the ability to do work. That can happen in different ways because there are many different forms of energy.

Kinetic energy

The first form of energy is thekinetic energy. Vehicles such as cars, motorcycles or airplanes have such a kinetic energy when driving or flying. Kinetic energy also can be used to deform things. For example, if a car has an accident and drives against an object or if the car rushes into another car or tree, the car will break, and the tree willbe damaged. Thus, the kinetic energy was transformed into deformation energy.

Potential energy

Another form of energy is the potential energy. The concept of potential energy can be explained to the children by the following example. If you are sitting on a bike on a hill or a mountain, the bike has potential energy, because it can roll down the mountain. On the way down the bike becomes faster and faster (without braking), it is accelerated. This is called doing “acceleration work”. Therefore, a body or an object has potential energy when it is able to fall or move down. Hydroelectric power stations also use this form of energy. They pond the water of a river in a water reservoir. The larger the reservoir, the more energy can be generated. The water is drained controlled. Thus, turbines from the potential energy of the water generate electrical energy.

Elastic energy

The third form of energy is the elastic energy. Springs like those found in mattresses or sofas have this elastic energy. For example, a spring that is tensioned can shoot e.g. a ball upwards. This is how catapults work. When the ball flies up, it’s called “lifting work”.Thus, the elastic energy of the spring is transferred into the kinetic energy of the ball. When an object etc. is deformed but can returnto its original state, it has elastic energy.

These three forms of energy, the kinetic energy, the potential energy and the elastic energy, are called mechanical energies.

Electrical energy

In addition to the mechanical energy, there are other forms of energy, too. One of them is the electrical energy.An example of the electrical energy is the electricity we see as a light in a lamp. In power stations, electrical energy is obtained, for example, by the transformation of thermal energy. The electrical energy is transported to our houses via powerlines. Electricity is very important to make many things work (e.g. the light, the stove etc.). Thus, it is the most versatile form of energy.

Electricity can be produced in many different ways. Therefore,the energy has first to be transformed. You can gain electricity from the following sources:

  • Wind from wind turbines,
  • Hydropower (from rivers) from hydropower stations,
  • Solar energy from solar cells and photovoltaic systems,
  • Coal, oil, gas are burned and the resulting heat can be transferred into electricity,
  • Nuclear energy in nuclear power stations also generates heat by the splitting of atomic nuclei, which is transformed into electricity.

Magnetic energy

Furthermore, there is the magnetic energy. You can find this form of energy only in magnets, for example in a horseshoe magnet. They can act repulsive or attractive.

Thermal energy

Another form of energy is thethermal energy. You can find this form of energy for example in steam, because it is very hot. The enormous heat of volcanoes can also be used for the generation of energy. Geothermal energy can be used to heat water for the heating of residential buildings.

Solar energy

The solar energy is very important for every human being. You can find this solar energy in the radiation of the sunlight. It is essential for our life on the earth. The sun transfers about four million tons of hydrogen into energy every second. On the one hand, this is known asthermal energy. On the other hand, this energy produces visible light, the solar radiation, which reaches the earth after only eight minutes. However, there is only a small part of the solar radiation, which arrives at the earth. Nevertheless, this small part of the solar energy is sufficient forthe life of our planet. Nowthe hydrogen on the sun can still supply the earth for about five billion years.

Nuclear energy

Nuclear energy is the energy between the particles in the atomic nucleus. Therefore,you can find the nuclear energy in atoms. They can produce huge amounts of energy. This happens, for example, in nuclear power stations.

Chemical energy

The last but very important form of energy is the chemical energy. The body can getthis form of energy for example by the consumption of food or beverages. The chemical energy in our bodies can then be transferred into other forms of energy, such as thermal energy or kinetic energy. Even when a fire burns, chemical energy is transformed into thermal energy. For example, chemical energy is stored in oil, gas, coal and wood, which can be transferred into thermal energy by burning.

How do plants use solar energy? – Photosynthesis

Plants are actually small solar power stations, which do photosynthesis within their green leaves. More precisely, the photosynthesis takes place in the green pigment of the leaves, called chlorophyll. The chlorophyll is supplied with water by the veins of the leaves and gets CO2 through the leaves surfaces. The chlorophyll metabolizes the CO2 and the water into sugar using sunlight as an energy source. Sugar gives energy to plants – just as if food gives us chemical energy. Thus, photosynthesis is one of the few processes with which (physical) solar energy is naturally transformed into chemical energy. As a waste product, something important (especially for us) is additionally produced: oxygen. The plant is not able to use it and therefore releases it into the air. Therefore,it is due to the plantsthat we have the oxygen in our air, without whom humans and animals could not live. Plants also have another important function: they destroy CO2 . Because of e.g. coal-fired power stations, vehicles and aircrafts, we have more CO2 in the air than it is healthy for our planet. Therefore, we should treat our environment, the individual trees and plants with respect because they enable the life on earth. In addition, we should plant as many new plants as possible instead of cutting down the forests.

Units of energy

Energy units can easily be converted into each other:

1 000 J = 1 Kilojoule = 1kJ 

1 Million J = 1 Megajoule = 1 MJ

1 Milliarde J = 1 Gigajoule = 1 GJ 

1 Joule = 1 Wattseconde (Ws) 

3 600 KJ =  1 Kilowatt-hour (kWh)

1 Calorie (cal) = 4,18 Ws

1 Kilocalorie (kcal) =1.000 Calories

Energy conversion

Typically, not all energy can be used as it is. Often, the energy first has to be transferred, as in the case of electricity, for example. That is called“energy conversion“. This actually means that energy is transferred from one energy store to another during an event. For example, a hair dryer converts electricity into thermal energy. Within the conversion energy cannot disappear and be produced out of the nothing either. In order to get electricity, for example to use the hair dryer, energy which already exists, must first be transferred into electrical energy.The generation of electricity and heat in Germany (for 2016) from renewable energy sources:

  1. 59% bioenergy
  2. 20% wind energy
  3. 12% solar energy
  4. 6% hydropower
  5. 3% geothermal energy

Conscious acquaintance of energy

Even if we are trying to use more renewable energies, it is best for our environment to consume as little energy as possible

How can energy be saved?

  1. Save warm water: Those who take a short shower instead of bathing in a full bathtub can save a lot of water. In addition, the water-tap does not have to be turned on full and the temperature of the water does not have to be so hot. This isbetter for our skin, too. Even a full dishwasher is more efficient and saves more water than washing by hand. However, the dishwasher should not be switched on until it is full.
  2. Turn things you don‘t need at the moment off: Light, computer, television, water, etc. Some devices have a stand-by function that prevents them to switch off completely. To turn them off completely, a multiple socket which can be switch on an off, can be used.
  3. Economical heating: We consume the most energy in the household by heating. Therefore, in the winter, ventilation should be short and with windows fully open. A tilted window consumes more heating than it lets fresh air into the house. So, in winter you should turn the heating down (a little) and dress yourself warmer for saving energy.
  4. Use flushing tanks with modern automatic water saving system: These flushing tanks have an “economy button” with which only half of the water is used. This saves 20,000 liters of water in a year regarding a four-headed family.
  5. Well-isolated houses need less energy thanhouses, which have no good isolation: “Eco-Houses” or “Plus-Energy-Houses” are very well isolated and produce even more energy than the inhabitants themselves can consume.
  6. Use the car less: People, who walk, cycle or use public transport such as buses or trains also save energy.
  7. Do not forget the lid while cooking: Those who cook without a lid or open the lid frequently during cooking consume more energy. Without a lid, it takes longer until something starts to boil. Those who like to see what they are preparing can switch to glass lids.