Cogeneration units – Biogas

Cogeneration units are equipment for combined power and heat generation. It is a gas combustion engine driven by a three-phase generator which generates electricity. The cooling of the engine, oil and combustion products generates heat.

Electricity is used to cover own consumption, or is sold to the distribution network. Cogeneration units can also run in an island operation mode, and can therefore be used as a stand-by source of electricity.

Cogeneration units can also be driven by biogas.

Biogas is a promising fuel for cogeneration units, especially because of pertaining to the category of renewable energy sources. Today, it is mainly used in waste water treatment plants and biogas plants. When examining the possibilities for installing a biogas-based cogeneration unit, it is necessary to know some information that is crucial to the implementation of the plan, such as:

1. Biogas properties – represent the basic information on fuel properties, mainly about its usability with regard to harmful additives, as well as information on its energy properties – calorific value. The following information is important in particular:

• methane content (the entire gas composition, if possible);
• stability of the gas quality;
• content of harmful additives.

2. Biogas production, possibility of biogas storage in gas-holders – information on gas possibilities and volumes;

3. Possibilities for biogas distribution. Consider which of the following ways of operation is to be applied:

• CU operation with biogas only;
• combined operation with natural gas + biogas (switch between fuels);
• mixing of biogas and natural gas.

4. Requirements for the cogeneration unit functions:

• parallel operation with the network (P)
• parallel operation, including the possibility of the island operation mode (P, I)
• parallel operation with the function of a stand-by source (P, E)

5. Power consumption of waste water treatment plants and biogas plants, power take-off rates