Cogeneration of energy: what is it and how does it make us more efficient?

Cogeneration is a model that produces two types of energy, electrical and calorific. But what is cogeneration of energy and how does it make us more efficient?

What is cogeneration of energy?

The Institute for Diversification and Energy Saving (IDAE in Spanish) defines cogeneration as "the joint production, in a sequential process, of mechanical and/or electrical energy and useful thermal energy".

To understand this, you need to imagine a thermal energy generation plant that not only produces electricity, it also produces heat as a result of the combustion processes. Instead of letting the heat escape, it can be harnessed. For example, by installing a boiler with water. When the water is hot it can be used in a heating system. And if steam is produced, it can be used to move or activate machinery or to produce more electricity.

In the beginning, cogeneration was linked to industries whose operations generated high temperatures (chemical, metal, ceramics, food, paper, automotive); however, in recent years it is beginning to be implemented in other types of activities, such as sports centres (to heat swimming pools) or in the heating for large buildings (for example, hospitals and hotels).

Current town planning is also including it in its most sustainable proposals. In fact, the European Union (EU) has taken cogeneration into account in its energy policy for the reduction of gas emissions and carbon neutrality for 2050.

How can this type of system be implemented?

There are a number of types of energy cogeneration systems:

• Gas turbine: natural gas is burned in a chamber, where mechanical energy is produced that is subsequently transformed into electricity. The gases resulting from combustion are used to generate mechanical energy from the industrial process or to generate steam, with the same objective.
• Steam turbine: generates mechanical energy from steam. It does not depend directly on one type of fuel, so it is especially versatile.
• Combustion engine: In this case, water is replaced by oils that maintain the heat and help to cool engine components that overheat, by means of a heat-exchange system.

There is a third modality, trigeneration, which includes refrigeration and also takes advantage of the gases to provide CO2 to greenhouses or use them in the manufacture of carbonated beverages, thus increasing efficiency.

What do you need to be able to use energy cogeneration?

Here are the main requirements to be able to install energy cogeneration in a community or a company.

1. A preliminary technical study, undertaken by professionals, that analyses the specific case for installation and performance. This will help you to know in advance if the project would be feasible from the technical and financial point of view.
2. Preparation of a technical project, with the participation of accredited technicians, together with the corresponding budget.
3. Management of a connection point with an energy distribution company.
4. Execution of the project, with professional supervision.
5. Administrative regularisation, with the corresponding documentation, requests, permits and certificates, depending on the administration and type of installation.

An energy cogeneration installation usually consists of the following:

• Chamber or engine to burn the fuel and generate mechanical energy, which will be transformed into electricity.
• Raw material as a primary energy source. As already mentioned, these can be fossil fuels, biofuels or biomass.
• Electricity generator, which converts mechanical energy into electricity.
• System for making use of heat energy generated in the previous energy production process.
• Cooling system to prevent overheating of the system and/or water processing system in the case of water heating.

Advantages of cogeneration of energy

There are a number of benefits to the cogeneration of energy:

• Efficiency: It is estimated that between 10% and 30% of the energy is dispersed in a cogeneration process. This is equivalent to an improvement in energy efficiency of between 70% and 90%.
• Cost reduction: Not only in infrastructure but in associated costs such as raw material, since more energy is produced with the same investment. The surplus energy can also be sold to generate a profit.
• Reduction in emissions: Generation from heat energy is emission-free.
• Versatility: It can be incorporated or combined with other sustainable systems such as biomass, so it can potentially be green.
• Flexibility: It adapts to the needs of the environment.
• Independence: It promotes energy independence and self-sufficiency, as well as reducing the possibilities of supply cut-off.
• Circular economy: It consolidates the circular economy model, making the most of resources.
• Environment: the re-use of hot water from cooling circuits is an advantage, since some industries release this hot water into the environment, affecting the water temperature of rivers, seas and lakes, with the subsequent detrimental effect on biodiversity.