Heating oil as a fossil fuel

Even today, oil heating systems are among the most widely used heating systems in Germany. Whether using calorific value or condensing technology, an oil boiler is characterized by its economical operation, its proven technology and, last but not least, its energy-rich fuel.

How crude oil became fuel oil

Crude oil is a mixture of at least 500 components. Among other things, kerosene, gasoline, diesel and, of course, heating oil can be produced from crude oil (oil that has already been extracted). Before the crude oil can be used as heating oil in the combustion chamber of a heating system, it must first undergo several processes. Experts divide this process into distillation, conversion and refining. During distillation, the crude oil is broken down into different product groups characterized by their different boiling ranges. The second step involves converting the hydrocarbons into larger, smaller or differently structured molecules. This is necessary because the demand for "light" products is constantly increasing. And because crude oil has a high sulfur content, which would release toxic sulfur dioxide during combustion, it is desulfurized in the final step, refining.

The different types of fuel oil

Not all heating oil is the same. In this country, this fuel is standardized. DIN 51603-1 and DIN SPEC 51603-6 subdivide the heating oil into:

  • Standard heating oil EL
  • Low-sulfur heating oil EL 
  • Bio heating oil.

The former is no longer produced in Germany. Almost all private households use EL low-sulfur heating oil instead. It was originally developed for condensing boiler technology. However, thanks to its numerous advantages, such as clean and virtually odorless combustion and a reduction in sulfur content of around 20 percent, EL low-sulfur heating oil has now become established. The abbreviation EL stands for "extra light liquid". Oil condensing boilers that burn only low-sulfur EL heating oil must be fitted with a green filling tube cap.

In addition to low-sulfur EL heating oil, there is also premium heating oil and bio heating oil. Compared to "standard EL heating oil," the former contains special additives that, for example, extend the storage period or reduce deposits. Bio heating oil, on the other hand, is made from renewable raw materials such as rapeseed, sunflowers or soybeans and is added to the low-sulfur EL heating oil. The calorific value of heating oil is approximately 45.5 MJ/kg. This corresponds to 10.74 kilowatts per liter. In comparison, natural gas has a calorific value of about 36 to 50 MJ/kg. Depending on the grade, however, the oil calorific value may vary slightly. When placing an order, suppliers often specify the calorific value of oil in addition to the calorific value.

Heating oil can also be produced regeneratively, for example with the help of rapeseed plants.

Heating oil can also be produced regeneratively, for example with the help of rapeseed plants

The oil tank as an important component of an oil heating system

In order for the heating oil to enter the combustion chamber automatically and in a well-dosed manner, it must be stored. The tank required for this purpose is usually made of metal or plastic. To increase the tightness, many tanks are double-walled and also have safety components such as the limit value sensor or other measuring instruments. The former prevents the heating oil from leaking out in the event of overfilling and entering the groundwater or soil.

The picture shows various plastic tanks for fuel heating oil.

Above or below ground storage possible

The heating oil can be stored either above ground or underground. For the above-ground variant, the site-built and the battery tank come into question. The former is assembled directly on site and depends on the available space. Battery tanks consist of individual modules that can be connected to form a single unit. If there is no free space inside the building, system owners can also store the heating oil underground. The so-called underground tank is more expensive to purchase and install than its above-ground counterparts. On the other hand, it does not take up any space inside the building and can be "buried" almost invisibly.

Oil tanks in flooded areas

Regardless of the type of installation, every oil tank must meet high safety standards. These are firmly anchored in the "Ordinance on Installations for Handling Substances Hazardous to Water" (VAwS). Accordingly, tanks with a capacity of more than 5,000 liters must be installed in a separate room. The installation room itself must also meet certain requirements and, for example, have a self-closing door or a fire resistance class. If the tank is located in a flood zone, the entire installation must be flood-proofed. As a general rule, both the installation and the dismantling of an oil tank may only be carried out by a specialist.