If there is primary energy, there must also be secondary energy. The prefix alone suggests this. The following text will deal with secondary energy. What is secondary energy? It is best to start directly with a definition of secondary energy. Secondary energy includes the types of energy that do not come directly from nature. So, in that sense, it is converted primary energy. Primary energy includes lignite, petroleum, and natural gas, but also solar energy, wind power, hydroelectric power, geothermal power, and tidal energy.1 Secondary energy examples include electricity derived from primary energy. Indeed, without technical means, energy from sunlight or wind cannot be used to heat or run other electrical appliances such as the television or oven. Therefore, the primary energy of the sun must be converted into secondary energy. Solar thermal or photovoltaic systems take over this part and provide electricity or heat for consumers at the end of the utilization chain. In the case of wind energy, wind turbines are used, and tidal power plants, for example, are needed to harness the power of water.
Now that the definition of secondary energy has been clarified, the next question is how primary energy is converted into secondary energy and what challenges arise. What is clear is that depending on the primary energy source and the conversion process, there are many different types of secondary energy and secondary energy sources. Electricity is generated from solar, wind and hydro power. Coke is produced from hard coal. Crude oil serves as the basis for heating oil, gasoline and liquid gas. But that is by no means the end of the story. Secondary energy sources are numerous. Coal briquettes for the stove or barbecue, district heating, coke oven gas, but also charcoal, fuels and various gases are examples of secondary energy sources. In power plants and refineries, primary energy is converted into secondary energy. However, losses occur during the conversion process. Some of the energy is lost. Often in the form of waste heat. This also happens during transport via heat and power grids to consumers. At the same time, the conversion plants, such as refineries, themselves consume secondary energy. Therefore, only about two thirds of the energy reaches the consumers.2
It works more efficiently with other energy carriers such as hydrogen and methanol. The advantage of both secondary energy carriers is also their storability and transportability. After production, hydrogen and methanol can be used wherever they are needed. To be able to reuse both as secondary energy, a converter is needed. In this case, it is fuel cell technology. As the name of the fuel implies, either the hydrogen fuel cell or the direct methanol fuel cell is used. SFC Energy offers its customers both fuel cell variants and, as a pioneer, has more than 20 years of experience in manufacturing and using the units. The EFOY direct methanol fuel cell and the EFOY Jupiter hydrogen fuel cell supply numerous applications with energy – or more precisely, clean secondary energy. This is a good thing in itself, since fuel cells help to achieve the ambitious climate protection goals of the EU and the German government and to reduce primary energy consumption. Fuel cells from SFC Energy are therefore a secondary energy application.
Why is it so important to reduce primary energy consumption? And what is it all about? First of all, primary energy consumption refers to the energy content of all primary energy sources used.3 Important: In addition to the useful or final energy that is essential for consumers, the losses for the production and transport of the raw materials used are also included in the balance.4 An example illustrates the calculation. If homeowners need about 20,000 kilowatt hours per year to heat their home with a gas heater, the consumption of primary energy is actually higher than the 20,000 kilowatt hours of useful energy consumed. The primary energy consumption is likely to total about 22,000 kilowatt hours. Of this, 20,000 kilowatt-hours is the final energy consumption for heating the house and the losses in generating the heat. 2,000 kilowatt hours are accounted for by losses in the extraction, processing and distribution of the natural gas. To calculate the primary energy consumption, the efficiency principle is necessary.5
For this purpose, the amount of raw material used is multiplied by the respective calorific value for energy sources such as coal, gas, wood or oil. Assuming the combustion of ten liters of heating oil, this results in a primary energy consumption of 98 kilowatt hours (calorific value = 9.8 kilowatt hours per liter). In the case of electricity from hydro, wind or solar power plants, only the amount of electrical energy generated is included in the primary energy consumption. Thus, experts assume an efficiency of 100 percent for renewable energies.6 Thus, if primary energy consumption is to decrease, a further expansion of hydro, wind and solar power plants is important and inevitable. Only in this way will it be possible to achieve the climate protection targets. In Germany, primary energy consumption is declining. According to AG Energiebilanzen, it was 11,691 petajoules in 2020 – 16.8 percent of which was accounted for by renewable energies. The year before, primary energy consumption was 12,779 petajoules, of which renewable energies accounted for about 15 percent.7 The direction is right, but there is still a lot to do. Always in view: the inseparable pair of secondary energy and primary energy.