The Potential of Combined Heat and Power (CHP) Technology

Current global energy scenario and the shift towards renewables

The global energy scenario is undergoing a significant transformation. Historically, the world has relied heavily on fossil fuels, such as coal, oil, and natural gas, which have powered industrial growth and economic development. However, this reliance has had severe environmental consequences, including air pollution, climate change and resource depletion. In recent years, there has been a pronounced shift towards renewable energy sources. This transition is driven by a combination of factors, including technological advancements, the decreasing costs of renewable energy technologies, government policies and a growing public awareness of environmental issues. Countries around the world are setting ambitious targets to increase the share of renewables in their energy mix. The primary sources of clean energy include biomass, solar, wind, hydro, and geothermal power. These sources are sustainable and have a minimal environmental impact compared to conventional fossil fuels, which are finite and release harmful pollutants and greenhouse gases. The importance of clean energy lies in its potential to mitigate climate change, limit environmental pollution and provide a sustainable energy future. Technologies like Combined Heat and Power (CHP) further support this transition by improving energy efficiency through the simultaneous generation of electricity and useful heat, especially when using renewable fuels like biomass. Clean energy technologies, including CHP, help reduce the dependency on fossil fuels, enhance energy security and promote economic growth by creating jobs in new industries.

Introduction to Combined Heat and Power (CHP): Enhancing efficiency in pre-transition energy systems

Combined Heat and Power (CHP), also known as cogeneration, is a highly efficient energy system that generates electricity and useful thermal energy in a single, integrated process. Unlike conventional power plants that discard the heat produced during electricity generation, CHP systems recover and use this heat for various applications, such as heating and cooling buildings. The basic working principle of CHP involves the simultaneous production of electricity and heat from a single fuel source, such as biomass, biogas or biomethane. A typical CHP system includes a prime mover (such as a gas turbine, steam turbine, or reciprocating engine), an electricity generator and a heat recovery system. The prime mover generates electricity and the waste heat from this process is captured and used for heating purposes, which significantly enhances overall energy efficiency.

Types of CHP systems

• Micro-CHP systems: are designed for residential or small commercial applications and provide both electricity and heat to individual homes or small buildings. They typically use renewable fuels, such as biomass, to offer a compact and efficient local energy solution.

• District CHP systems: are larger systems used to supply power and heat to multiple buildings, such as those in a university campus, residential district or even an entire city. They are centrally located and distribute electricity and heat through an extensive network of pipes and wires, making them suitable for community-wide energy solutions.

Advantages of CHP system

• CHP systems can achieve efficiency levels of over 90%, compared to 30-60% for conventional power plants. This increased efficiency translates to lower resource costs and savings on energy bills.

• The simultaneous generation of electricity and use of waste heat in CHP systems increases overall efficiency, maximising the use of clean fuel sources like biomass, biogas, or biomethane.

• CHP systems enhance energy security by reducing the reliance on external power supplies and increasing the resilience of the energy infrastructure.

Renewable energy sources for CHP

Integrating renewable energy sources with CHP systems significantly improves the efficiency of sustainable energy solutions. These include the following examples:

1. Biomass: The combustion or gasification [1] of biomass (from organic materials, such as wood chips, agricultural residues and dedicated energy crops) to generate electricity and heat produces steam that drives a turbine connected to a generator, and the residual heat is captured for thermal applications. Biomass is considered carbon-neutral as the CO2 released during combustion is offset by the CO2 absorbed during growing the biomass source.

2. Biogas: Methane-rich biogas (produced through the anaerobic digestion of organic waste materials, such as agricultural waste, manure, sewage sludge and food waste) can be used as a fuel in CHP systems to generate electricity and heat. Using biogas in CHP systems improves waste management and reduces methane emissions from landfills, contributing to environmental sustainability.

3. Solar thermal: CHP systems use solar collectors to capture sunlight and convert it into thermal energy. This thermal energy produces steam or hot water that drives a turbine or engine to generate electricity, and the residual heat is used for heating applications. Solar thermal CHP is particularly effective in sunny regions and can be integrated with other renewable sources to enhance a system’s reliability.

4. Geothermal: CHP systems exploit the Earth's natural heat by tapping into geothermal reservoirs to produce steam. This steam drives a turbine connected to a generator to produce electricity, and the remaining thermal energy is used for heating purposes. Geothermal energy provides a constant and reliable energy source with a minimal environmental impact.

GDSO Project Spotlights – Bio-FlexGen

In the context of Europe’s Green Deal and its drive towards sustainable energy solutions, various EU-funded projects are playing a pivotal role. Recent technological innovations have significantly enhanced the efficiency and feasibility of renewable-powered CHP systems. One groundbreaking example is the Bio-FlexGen project, funded by the EU Green Deal Call, which aims to develop a CHP plant with several unique, patented features.

Figure  1: Bio-FlexGen CHP plant (Source: Bio-FlexGen)

Bio-FlexGen is improving the use of biomass and green hydrogen to deal with changes in seasonal energy and heat demand. When demand is low, the plant will produce climate-positive green hydrogen from biomass to complement other renewable sources, such as wind and solar. The project aims to reach 55% electrical efficiency from biomass by 2030. Bio-FlexGen’s CHP plant has three unique, patented features:

• High-pressure gasifier that makes converting biomass into energy more efficient;

• Novel combustion chamber capable of generating temperatures up to 1400°C, which increases the system's performance;

• Biomass-fired top cycle (BTC) gas turbine technology that generates electricity from forestry and agricultural waste at twice the efficiency of standard steam-cycle technologies.

The BTC modular 25MWe [2] power plant will flexibly generate four different outputs: electricity, heat, hydrogen and CO2, from renewable biomass or green hydrogen, depending on market needs and energy demand. It provides biopower at 55% efficiency by converting variable supplies of different low-cost biomass residues. When energy demand is lower, it switches to renewable hydrogen for quick peak power generation.  The plant uses a process that gasifies biomass for use in a high-pressure gas turbine with steam injection. As a co-generation technology, it also repurposes waste heat for industrial and commercial purposes, offering a sustainable alternative to heat produced from fossil fuels. For more detailed information, visit the Bio-FlexGen Project website, watch their animated film, or check out their infographic, fact sheet, and brochure. Additionally, you can follow their updates on X and LinkedIn.

GDSO Project Spotlights – RESTORE

The RESTORE project aims to improve the use of renewable energy and waste heat through advanced thermochemical energy storage (TCES) [4] and thermodynamic cycles [5]. Its innovative methods provide a comprehensive solution for district heating and cooling networks by harnessing renewable energy sources and recovering waste heat.

Figure  2: TCES system (Source: RESTORE project)

The TCES system is key to the improved flexibility and efficiency of energy systems. It works by storing energy in a specially designed reactor filled with a solid material suspended in oil. During the charging phase, an energy-storing reaction occurs, and during discharge, the stored energy is released as heat. This heat exchange is linked to an Organic Rankine Cycle (ORC) [6], which is a thermodynamic cycle that converts heat into electricity using an organic fluid with a low boiling point, allowing it to operate efficiently at lower temperatures than traditional steam cycles. This helps convert thermal energy into electricity, similar to the way CHP systems operate.

RESTORE’s innovative approach complements CHP systems by providing an alternative method of energy storage and recovery. In CHP systems, where heat and power are generated simultaneously, integrating a RESTORE system could enhance overall efficiency by storing excess heat and converting it back to usable energy, thereby helping to balance energy loads and improve the flexibility of CHP operations, especially in district heating scenarios.

Operational highlights:

• Dual-purpose reactor: can operate in both charging and discharging modes, making it highly adaptable to varying energy demands. The reactor integrates with the thermodynamic cycles, similar to how CHP systems integrate with existing heating and power infrastructures.

• Efficient use of resources: The system’s ability to harness energy from renewable sources and recover waste heat makes it a valuable addition to the sustainability goals of CHP systems, enhancing their capability to operate on renewable energy.

For more detailed information, visit the RESTORE Project website and check out their key deliverables. Additionally, you can follow their updates on LinkedIn.

GDSO Project Spotlights – HYPERGRYD

The HYPERGRYD project is a smart energy system that integrates renewable energy sources with state-of-the-art digital and automation technologies to optimise both thermal and electric grids. The system enhances the management and efficiency of energy systems through an advanced, digitally-operated platform that can process complex data while seamlessly connecting different energy components.

For complex networks, such as district heating and cooling systems where efficient resource management is crucial, incorporating smart-grid technologies into CHP systems allows more flexibility and precise energy distribution and utilisation.

Highlights of this innovative strategy include the direct transfer of data from smart meters in Großschönau to the KTH database in Stockholm via the internet, which allows instant access to live data for programming. This has helped optimise the process and refine machine-learning models. Furthermore, the new database at KTH has significantly improved the efficiency of data analytics, mining and modelling.

Figure  3: Data transfer from energy smart meters in Großschönau to the KTH database in Stockholm via the internet (Source: HYPERGRYD project)

Operational highlights:

• Data-driven optimisation: Leveraging the Internet of Things (IoT) technology for real-time data collection, HYPERGRYD enhances monitoring and control within CHP systems. Advanced data integration allows immediate adjustments in energy production, aligning output with demand fluctuations and thereby reducing inefficiencies.

• User-centric digital platform: HYPERGRYD’s user-friendly digital hub integrates various energy sources and sinks. This significantly streamlines the management of CHP systems and facilitates easier incorporation of renewable energies, as well as more effective thermal and electrical energy distribution.

The application of HYPERGRYD’s smart grid solutions to CHP systems has several transformative benefits:

• Enhanced system responsiveness: Live data processing and automated adjustments in CHP systems enhances their responsiveness to demand changes, which improves both operational efficiency and system reliability.

• Increased renewable integration: HYPERGRYD’s integration with renewable energy sources improves the utilisation of renewables in CHP systems, contributing to the achievement of broader environmental and sustainability goals.

For more detailed information, visit the HYPERGRYD Project website and check out their key deliverables. Additionally, you can follow their updates on LinkedIn.

In conclusion, CHP technology is a cornerstone in the global shift towards renewable energy, offering a robust solution to enhancing energy efficiency, reducing carbon emissions and lowering operational costs. The ability to generate electricity while capturing heat in a single process allows CHP systems to optimise energy use, contributing significantly to environmental sustainability. Additionally, the integration of advanced energy storage, smart grid technologies and IoT innovations elevates the functionality and adaptability of CHP systems, ensuring that they meet the dynamic demands of modern energy networks and supporting the transition towards a sustainable and resilient energy future.

______________________________________________________________________

[1] Gasification: a process that converts carbon-rich materials into synthetic gas (syngas) by heating them with limited oxygen or steam at high temperatures.

[2] MWe: Megawatt electric

[3] Thermochemical energy storage: stores energy through reversible chemical reactions, where heat is absorbed during charging and released during discharging, allowing efficient, long-term storage with minimal heat loss.

[4] Thermodynamic cycle: a series of processes in which a system undergoes changes in temperature, pressure, and volume, returning to its initial state while converting heat into mechanical work or vice versa.