Combined Heat and Power Plants and Cogeneration - our detailed guide
CHP power plant 10 min read

Combined Heat and Power Plants & Cogeneration – our detailed guide

Combined Heat and Power (CHP) plants, efficient in simultaneously generating electricity and heat, are gaining popularity for their environmental benefits. They range from small-scale to larger units, fitting various energy needs. The core technology of CHP involves cogeneration, using engines and generators to optimize energy usage.
24. Oct 2023
Team PowerUP

Combined heat and power (CHP) plants are gaining popularity, and for good reason. These innovative systems, based on the principle of cogeneration, simultaneously generate electricity and heat from a single energy source. In addition to their high efficiency, they also offer significant environmental benefits

In this article, we will explore the world of CHPs in depth, illuminating their functionality, benefits, and applications, and demonstrating why they are regarded as a pivotal technology for the future of energy supply.

What is a Combined Heat and Power Plant (CHP)?

A combined heat and power plant is a compact energy system that utilizes the principles of cogeneration to produce both electrical energy and heat from a single fuel source.

In contrast to conventional power plants, which only generate electricity and often leave the resulting heat unused, the CHP ensures that this heat is utilized for heating purposes or hot water production. This approach maximizes energy efficiency and minimizes fuel consumption

The core component of a CHP is typically an internal combustion engine, similar to those used in cars, which drives a generator to produce electricity. During this process, heat is also generated, which can be injected, for example, into the heating circuit of the building. CHP systems can be built in various sizes and capacities, ranging from small units for single or two-family homes to larger systems for multi-family homes or industrial applications. They are typically designed to precisely match the heat demand and required electrical power of the specific facility.

Principle of Combined Heat and Power (CHP)

How does CHP work? The basic principle of combined heat and power (CHP) represents a revolutionary method in energy production. While conventional power plants primarily generate electricity and often waste the resulting heat, CHP utilizes both forms of energy simultaneously. By combining electricity and heat generation in a single process, a significantly higher efficiency and reduced fuel consumption are achieved.

CHP is based on the simple concept of not considering the heat generated during electricity generation as waste, but rather utilizing it purposefully for heating or hot water supply. This simultaneous generation of electrical and thermal energy results in a significant reduction in the consumption of primary energy sources and, consequently, a decrease in CO₂ emissions.

It is the principle of cogeneration that makes block heat and power plants so efficient and sustainable, thus establishing them as a future-proof solution for the growing challenges in the energy sector.

The difference between nano, micro and mini CHPs

CHPs come in different sizes and power classes that can be specifically tailored to the respective energy needs. The terms micro, mini, and nano CHP refer to the size differentiation of these systems.

  • Nano CHP

The nano CHP is the smallest variant of CHPs and is particularly suitable for very small units such as one-room apartments or tiny houses. With an output of less than 2 kW, they are highly compact and efficient in buildings with very low energy demand.

  • Micro CHP

A micro CHP is designed to provide energy for single-family to two-family homes. It typically has an electrical capacity of up to 15 kilowatts (kW) and can effectively meet the daily energy requirements of such households.

  • Mini CHP

In contrast, a mini CHP is more powerful and is suitable for larger buildings such as apartment buildings, small commercial enterprises, or public institutions. These systems typically have an electrical power output ranging from 15 to 50 kW.

Despite their varying sizes and capacities, all of these systems are based on the principle of combined heat and power (CHP) and generate both heat and electricity simultaneously. The most suitable system depends on factors such as the size of the building, the heat demand, and the desired level of self-sufficiency.

Technology and Components

The technology behind combined heat and power (CHP) plants is impressive in terms of its efficiency and potential for energy savings. At the heart of these systems is cogeneration, which allows for a dual energy output. But which components are responsible for achieving this level of performance?

The main components of a CHP are:

A CHP plant is a complex system that consists of several key components. Each of these components plays a crucial role in operating the CPH efficiently and reliably.

Combustion engine
  • Combustion engine: The engine is the core component of the CHP. It converts the fuel – often biogas or natural gas – into mechanical energy. Depending on the type of fuel used, it can be a gasoline engine, a diesel engine, or other types of engines.
  • Generator: The generator converts the mechanical energy provided by the internal combustion engine into electrical energy. The electricity generated in this way can either be used on-site or fed into the public grid.
  • Heat exchanger: The heat exchanger is a key component in cogeneration. It captures the waste heat from the combustion engine and utilizes it for generating heat. This heat can then be used for various purposes, such as heating rooms or providing hot water.
  • Buffer storage: The buffer storage stores excess heat that is not immediately consumed. It ensures a consistent supply of heat, even when the CHP is not running.
  • Control and regulation technology: The control unit oversees and regulates the operation of the CHP plant. It ensures that the CHP plant ramps up or down as needed, thereby optimizing efficiency and fuel consumption.

Together, these main components form an efficient system that simultaneously produces both electrical and thermal energy, conserving resources and minimizing environmental impact.

Various drive technologies

Combined Heat and Power Plants (CHPs) can be operated with a variety of drive technologies. These technologies define how the CHP generates energy and what fuels it uses. Here are some of the most common drive technologies for CHPs:

Combustion engine: This is the most commonly used technology in CHP plants. The combustion engine utilizes fuels such as biogas, natural gas, or liquefied petroleum gas. It operates similarly to engines in vehicles, with the main distinction being in the energy conversion process: while vehicles convert energy into motion, CHP plants convert it into both electrical and thermal energy.

Stirling engine: A Stirling engine is an externally heated engine that operates on a closed-cycle principle. It can be powered by a variety of fuels and is characterized by its smooth operation and high efficiency.

Fuel cells: Fuel cells produce electrical energy through an electrochemical reaction between hydrogen and oxygen. They are highly efficient and ideally emit only water vapor as exhaust. They are regarded as one of the most promising technologies for CHP plants, especially in conjunction with renewable energy sources.

Gas turbines: Gas turbines are primarily used in larger plants or industrial applications. They utilize highly compressed gas to generate energy. While they are known for their high power output, they often require a more complex infrastructure.

The utilization of renewable energies in CHPs

The integration of renewable energies into block heat and power plants (CHPs) is becoming increasingly important as it enables sustainable and environmentally friendly energy production. CHPs that are based on renewable energy sources provide an efficient way to reduce carbon dioxide emissions while also decreasing reliance on fossil fuels.

Biogas is an excellent example of the utilization of renewable energies in CHP plants. It is produced through the fermentation of organic materials such as plant residues or manure. When biogas is burned in CHPs, it simultaneously generates both heat and electricity, thereby increasing its efficiency.

Solar thermal can also be combined with CHPs. In this system, the heat generated by solar panels is utilized to meet the building’s heating requirements or to heat water. In case of inadequate sunlight, the CHP can supplement and provide the necessary energy.

The feed-in tariff provides an additional incentive for the integration of renewable energies in CHPs. This system compensates energy producers for the electricity that is fed into the public grid, making investments in renewable energy sources more economically attractive.

In Germany, the Renewable Energy Sources Act (EEG) also plays a crucial role in promoting the use of renewable energy in CHPs. It establishes the legal framework and provides financial incentives for these kinds of investments.

Application and Integration

CHPs are not only technological masterpieces, but also highly versatile in their application. They can be found in a wide range of settings, including single and multi-family houses, industrial facilities, and municipal buildings. However, effectively integrating CHPs into existing systems and the public grid requires careful consideration. In this section, we will explore the diverse applications of CHPs and shed light on their successful integration into various environments.

The application areas of CHP plants

Combined heat and power plants are highly versatile systems that can be used in a wide range of applications, from private households to industrial facilities. Here are some of the most common areas where they are applied:

Single-family houses and two-family houses: Micro CHPs or Nano CHPs can be used in such residential buildings. They provide electricity and heat for the house and can also feed excess energy into the public power grid. This offers an efficient and cost-effective solution, especially in times of increasing electricity prices.

Multi-family houses: Mini CHPs or Micro CHPs are suitable for larger residential complexes. These systems can provide centralized heat generation and power supply for multiple units.

Swimming pools: CHPs are especially beneficial for swimming pools, as they can meet the high heat demand for the pool water and the premises. The combination of electricity generation and heat generation can result in significant cost savings.

Industrial facilities: In industrial plants with high energy demand, CHPs can contribute to optimizing energy consumption and reducing operating costs. The waste heat generated during production can be utilized for electricity generation or heating process water.

Public institutions: Hospitals, schools, and other public buildings can benefit from the advantages of combined heat and power (CHP) systems. By implementing CHPs, they can lower their energy costs and make a positive contribution to environmental conservation.

District heating networks: In urban areas, larger CHP plants or heating power plants can be used to supply multiple buildings through a district heating network.

District heating

Integration into the public grid

The integration of combined heat and power (CHP) plants into the public grid is a crucial aspect that provides both technical and economic benefits. It allows operators of CHP plants to not only generate energy for their own consumption but also to inject excess energy into the electricity grid. This integration facilitates a more efficient and sustainable use of resources

One of the main incentives for integrating CHPs into the public grid is the opportunity to receive a feed-in tariff for the electricity that is fed into it. This remuneration, which is governed by the Renewable Energy Sources Act (EEG), provides operators with an economic advantage and encourages the production of renewable energy.

To ensure a continuous and stable energy supply, CHPs can also be combined with a buffer storage. This storage system stores the excess energy produced during periods of low demand and releases it during peak times. This allows for increased system efficiency and grid stabilization.

Modern CHP plants are equipped with technologies that facilitate their seamless integration into the public grid. This includes control techniques that ensure the electricity generated meets the standards and requirements of the grid.

The successful integration of CHPs into the public grid requires technical expertise, starting from the planning and installation phase and extending to ongoing maintenance. However, this integration offers substantial advantages in terms of cost-effectiveness and contribution to sustainable energy generation.

Excess Energy and Storage

The efficient utilization of energy plays a crucial role in modern energy production, particularly in the context of combined heat and power generation. Frequently, combined heat and power plants (CHPs) generate more energy than is currently needed. This raises the issue of how to effectively manage surplus energy and determine the optimal storage solution.

A buffer storage is an essential component in many CHP systems. It is responsible for storing the excess heat generated by CHPs. During periods of low energy demand, the excess heat is stored in the buffer storage. When the energy demand increases, the buffer storage releases this stored energy, ensuring a constant and reliable energy supply.

In addition to traditional buffer storage, there are also innovative solutions based on renewable energies. For example, excess energy can be utilized to produce hydrogen through electrolysis, which can then serve as an energy storage medium.

When there is excess electrical energy, it is also advantageous to feed it into the public power grid. This enables CHP operators to benefit from feed-in tariffs and simultaneously contribute to the stability of the electricity grid.

Excess energy from block heating power plants (CHPs) can also be utilized to support other energy generation systems such as solar thermal or photovoltaic systems. By combining different energy sources, an even more efficient utilization of the generated energy can be achieved.

The economic viability of CHP plants

The decision to operate a combined heat and power plant (CHP) is often based not only on ecological considerations, but also on economic profitability. When used correctly, CHP plants can offer substantial cost savings for consumers and businesses

The feed-in tariff is a crucial factor for many CHP operators. If a CHP system produces more electrical energy than is needed, this surplus energy can be fed into the public grid.

Since the price of electricity tends to increase, CHPs offer a solution to control these costs. By generating their own electricity, operators can decrease the price per kilowatt-hour and take advantage of stable energy costs.

In Germany, there are various programs and initiatives, such as the KfW subsidy (KfW), that provide financial support for the installation and operation of CHP plants. These grants and loans can greatly reduce the initial investment costs.

One of the main advantages of CHPs is their high efficiency. In comparison to traditional methods of energy generation, where a significant amount of energy is often wasted as heat, CHPs utilize both the electrical energy and the produced heat, leading to a more efficient energy yield. At PowerUP, we can further enhance this efficiency with our specially developed spare parts and customized services.

Comparison to other heating systems

CHPs are just one of many options when it comes to heating systems. However, they stand out due to their ability to simultaneously generate electricity and heat. But how do they compare to other heating systems?

Electricity-generating heating: CHPs are essentially heating systems that also generate electricity. This means that they not only produce heat, but also generate electrical energy. This dual usage significantly increases overall efficiency compared to conventional heating systems that only generate heat.

Heat pump: The heat pump is a modern heating technology that extracts heat from the environment – such as the soil, air, or groundwater – and uses it for space heating and water heating. While heat pumps are highly efficient and generate minimal CO₂ emissions, they do not produce electricity like CHPs.

Heat pump

District heating: District heating originates from large heat and power plants and is distributed to consumers through a network of insulated pipes. CHPs can be utilized for district heating generation, but they have the advantage of being installed closer to the point of consumption, minimizing energy losses.

Solar thermal and photovoltaic systems: Solar thermal systems utilize solar energy to generate heat, while photovoltaic systems convert solar energy into electrical energy. Both systems are environmentally friendly, but their efficiency is highly dependent on the level of solar radiation. In contrast, CHP plants can consistently provide energy regardless of weather conditions.

Traditional heating systems: Many households still rely on conventional heating systems, such as oil heating. While these systems may be more affordable initially, they cannot match CHPs in terms of efficiency, CO₂ emissions, and operating costs.

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Frequently Asked Questions

What is the difference between electricity generation and heat generation in CHP plants?

How does the efficiency of a CHP (cogeneration) system differ from that of traditional heating power plants?

Why should one opt for a CHP?

Which fuels can be used in a Blockheizkraftwerk (BHKW)?

How does the feed-in tariff for CHPs (Combined Heat and Power) work?

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