How to choose a cogeneration unit for the needs of an industrial plant?

So why is this process so difficult? First of all, each industrial sector is characterized by a different energy consumption profile, and demand can change dynamically depending on the season or changes in production processes. Additionally, legal requirements and fuel availability in a given location introduce further variables. In this article, we will introduce the types of cogeneration and suggest how to choose a CHP unit to best meet the investor's needs.

Let's start by explaining what cogeneration is. Cogeneration is the combined production of electricity and heat, in short, CHP - Combined Heat and Power. This is a device that simultaneously produces two types of energy, using much less fuel than if, for example, electricity and heat were produced separately.

Cogeneration, in addition to heat and electricity, can also produce cold. In the case of combined production of cold with electricity and heat, we are already talking about trigeneration. Thanks to this, cogeneration becomes a very interesting and energy-efficient solution that can be used in many sectors and industries - not only in industrial companies.

A cogenerator consists of two main components: a drive device and an electric generator. The drive device can be an engine with an internal combustion chamber, such as a diesel engine adapted to burn gas, or a gas turbine. In both cases, the drive device sets in motion an electric generator, the electrical power of which is usually 40–45% of the rated power of the engine or turbine. In addition to electricity, the cogenerator also produces heat energy recovered from hot exhaust gases and from the engine casing.

How to Choose the Size of a Cogeneration Unit

When talking about cogeneration units, we often use power, which determines their size. In this article, we will use the division used by the Energy Regulatory Office in the cogeneration bonus system.

• Small cogeneration units (up to 1 MW): These are micro- and small cogeneration installations often used in facilities such as hotels, hospitals, shopping centers, industrial plants, or housing estates.
• Medium-power units (from 1 MW to 50 MW): Often used in larger industrial plants, municipal heating plants, and commercial or business complexes.
• Large cogeneration units (over 50 MW): Installations used in large combined heat and power plants. They provide both electricity and heat on an industrial scale and for entire cities. They are often key sources of energy in energy systems, ensuring stability and reliability of supply.

The size of cogeneration units differs primarily in the range of power and the scale of applications, which determines their use in different types of industrial plants.

Does a Larger Cogeneration Unit Mean Better Efficiency?

One common mistake is to assume that a larger cogeneration unit will automatically provide better efficiency. In reality, it is crucial to properly match the device's power to the actual energy consumption profile. Cogeneration units are best suited for plants that consume electricity and heat or cooling at a similar level throughout the year. For example, these are companies in the food, paper, or chemical industries.

Generating Cold in Trigeneration

Trigeneration is an advanced energy process in which electricity, heat, and cold are generated simultaneously. It is an extension of traditional cogeneration, where only electricity and heat are produced. In trigeneration, part of the waste heat from the electricity generation process is used to generate cold using refrigeration devices, such as absorption chillers.

The choice between classic cogeneration and trigeneration depends on the nature of the production processes and the demand for heat and cold. In an industrial plant, where there is a high demand for electricity and heat at the same time, standard cogeneration may seem sufficient. However, if the plant also requires cooling, e.g., for product storage, trigeneration may prove more effective.

Cogeneration and Process Steam Generation

In plants where technological processes require high temperatures, process steam can be an important factor when choosing cogeneration. It allows for the simultaneous production of electricity and steam, making it an ideal solution for industries such as chemical or paper.

Here you will find an example of cogeneration designed and built by us in Schumacher Packaging - at the time of its commissioning in September 2024, it was the largest cogeneration unit operating on LNG gas in southern Poland: case study DB Energy - Schumacher Packaging.

Cogeneration Bonus

The cogeneration bonus is a form of financial support. It can be used by entities that build new or modernize existing units generating energy in cogeneration. This refers to high-efficiency cogeneration units, i.e., those with an efficiency higher than 75%. Its aim is to promote and stimulate the development of modern energy technologies that contribute to the reduction of CO₂ emissions. The cogeneration bonus in 2024 amounts to PLN 161.24 for every 1 MWh of electricity produced.

"Depending on the size of the unit, various forms of support are offered as part of the cogeneration bonus. For units generating less than 1 MW of electricity, a guaranteed bonus is available - awarded for each new unit of this capacity that meets the emission and efficiency criteria. Due to its attractiveness, this is a form of support that we often recommend. Obtaining a bonus for units with higher capacity is much more complicated and is related, among other things, to the obligation to discharge part of the generated heat into the public grid." says Kajetan Wiśniewski, Project Engineer at DB Energy.

The guaranteed premium solution was used, for example, by Słodownia Soufflet, where, in addition to other activities within the framework of thermal energy and modernization of the cooling system, we installed two cogeneration plants and a heat pump. You can find this implementation here: case study DB Energy - Słodownia Soufflet.

Let's Sum Up - What to Look for When Choosing Cogeneration?

When choosing a cogeneration unit, it is important to take into account environmental conditions, such as fuel availability and emission requirements, as well as the profile of electricity and heat consumption in the plant, including heat parameters or cooling demand in the case of trigeneration. The possibilities of using support systems, such as the cogeneration premium or EU projects, which can significantly improve the profitability of the investment, are also important. Matching the technology to these factors allows for achieving maximum efficiency and financial benefits.

Cooperation with experienced technology partners who can conduct a detailed analysis and design a "tailor-made" solution allows not only to maximize financial benefits but also to reduce the risk associated with the installation not being adapted to the specifics of the plant.

Selecting a cogeneration unit is a process that requires taking into account many variables: from the specifics of production processes, through available fuels, to emission requirements and the technical capabilities of the plant. Examples from various industries show that the key to success is an individual approach and adaptation of technology to actual needs.