How to select a cogeneration unit tailored to an industrial plant's needs?
Choosing the right cogeneration unit is a process that requires technical expertise and a deep understanding of the plant’s specific energy demands. In many cases, incorrect assumptions made during the planning phase can lead to a mismatch in unit capacity or the selection of technologies that fail to meet the plant’s energy requirements. This, in turn, results in suboptimal use of the cogeneration potential and increases the risk that the investment will not deliver the expected outcomes.
Why is this process so difficult? First of all, each industrial sector has a different energy consumption profile, and demand can change dynamically depending on the season or modifications in production processes. Additionally, legal requirements and fuel availability at a given location introduce further variables. In this article, we will explain the types of cogeneration and provide guidance on how to select a unit that best meets the investor's needs.
Let’s start by explaining what cogeneration is. Cogeneration, also known as Combined Heat and Power (CHP), is the simultaneous production of electricity and heat. It is a system that generates two types of energy at once, using significantly less fuel than if electricity and heat were produced separately.
Cogeneration can also produce cooling, in addition to heat and electricity. When cold is generated alongside electricity and heat, we refer to it as trigeneration. This makes cogeneration a very interesting and energy-efficient solution that can be applied in many sectors and industries – not just in industrial companies.
A cogeneration unit consists of two main components: the drive unit and the electric generator. The drive unit may be an internal combustion engine, such as a diesel engine adapted to burn gas, or a gas turbine. In both cases, the drive unit powers the electric generator, whose electrical output usually amounts to 40–45% of the nominal power of the engine or turbine. In addition to electricity, the cogeneration unit also produces thermal energy recovered from hot exhaust gases and the engine jacket.
How to select the size of a cogeneration unit?
When talking about cogeneration units, we often refer to their power, which determines their size. In this article, we will use the classification applied 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 residential areas.
- medium-sized units (from 1 MW to 50 MW) – commonly used in larger industrial facilities, 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. These are often key energy sources in power systems, ensuring stability and reliability of supply.
The size of cogeneration units differs primarily in terms of power range and scale of applications, which determines their use in various types of industrial plants.
Does a larger cogeneration unit mean better efficiency?
One common mistake is assuming that a larger cogeneration unit automatically ensures better efficiency. In reality, the key is properly matching the unit’s power to the actual energy consumption profile. Cogeneration units perform best in plants that consume electricity and heat or cooling at a stable level throughout the year. Examples include companies in the food, paper, or chemical industries.
Cooling production in trigeneration
Trigeneration is an advanced energy process in which electricity, heat, and cooling are produced simultaneously. It is an extension of traditional cogeneration, where only electricity and heat are generated. In trigeneration, part of the waste heat from electricity generation is used to produce cooling with the help of cooling devices, such as absorption chillers.
The choice between classic cogeneration and trigeneration depends on the nature of production processes and the demand for heat and cooling. In an industrial plant with high demand for electricity and heat, standard cogeneration may seem sufficient. However, if the plant also requires cooling, for example, for product storage, trigeneration may prove more efficient.
Cogeneration and process steam production
In facilities where technological processes require high temperatures, process steam may be a key factor when choosing cogeneration. It enables the simultaneous production of electricity and steam, making it an ideal solution for industries such as chemicals or paper.
Here you will find an example of a cogeneration unit designed and built by us at Schumacher Packaging – at the time of commissioning in September 2024, it was the largest LNG-fueled cogeneration unit in southern Poland:
Schumacher Packaging case studyCogeneration bonus
The cogeneration bonus is a form of financial support. It is available to entities that build new or modernize existing units producing energy in cogeneration. This refers to high-efficiency cogeneration units, i.e., those with an efficiency higher than 75%. The 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 is PLN 161.24 for each 1 MWh of electricity produced.
Depending on the unit size, different forms of support are offered under the cogeneration bonus. For units with electrical power below 1 MW, a guaranteed bonus is available – granted to every new or modernized unit that meets emission and efficiency criteria. Due to its attractiveness, this is often the form of support we recommend. Obtaining the bonus for higher-power units is much more complex and involves, among other things, the obligation to supply part of the generated heat to the public network, but it is also possible.
An example of using the guaranteed bonus is Soufflet Malting Plant, where, alongside other thermal energy projects and cooling system modernization, we installed two cogeneration units and a heat pump. You can find this case study here:
Soufflet Malting Plant case studyLet’s summarize – what to consider when choosing cogeneration?
When selecting a cogeneration unit, it is important to take into account environmental conditions such as fuel availability and emission requirements, as well as the plant’s energy consumption profile, including heat parameters and cooling needs in the case of trigeneration. It is also essential to assess the potential use of support systems such as the cogeneration bonus or EU projects, which can significantly improve the investment's profitability. Matching the technology to these factors allows for maximum efficiency and financial benefits.
Cooperating with experienced technology partners who can conduct a detailed analysis and design a tailored solution not only maximizes financial gains but also reduces the risk of installing a system that does not match the plant's specifics. Selecting a cogeneration unit is a process that requires consideration of many variables: from the specifics of production processes, through available fuels, to emission requirements and the plant’s technical capabilities. Examples from various industries show that the key to success is an individual approach and adapting the technology to actual needs.
