“Improving CHP system performance requires regular maintenance, advanced equipment upgrades, and intelligent integration of renewable energy sources for efficiency.”
How can performance in combined heat and power (CHP) systems be improved?
Guidelines for Enhancement
GENERAL APPROACH
Combined Heat and Power (CHP) systems are a leading energy-saving solution that reduces waste and enhances efficiency. However, achieving optimal performance requires specific improvement strategies. This article provides guidance on improving CHP system efficiency through technical and managerial measures.
Periodic Maintenance and Equipment Optimization in CHP Systems
Regular maintenance is the first and crucial step to improving CHP system performance. Without frequent checks, equipment can wear out and operate less efficiently. Therefore, attention should be given to cleaning heat exchangers, inspecting electrical circuits, and ensuring motors operate steadily.
Additionally, using modern equipment such as high-efficiency turbines or advanced internal combustion engines can optimize operations. These devices not only reduce fuel consumption but also lower greenhouse gas emissions, thereby boosting overall efficiency.
Optimizing Operations and Energy Management
Operational and energy control measures should be applied to enhance CHP system performance. Continuous monitoring of parameters like temperature, pressure, and power output can help detect potential issues early. Furthermore, leveraging artificial intelligence (AI) and advanced analytics software supports comprehensive efficiency improvements
Synchronizing energy production and consumption is another effective solution. For example, during peak hours, the system can focus on electricity production, while in off-peak hours, it prioritizes heat generation, thereby optimizing operating costs.
Integrating Renewable Energy into CHP Systems
Incorporating renewable energy sources such as biogas or solar energy into CHP systems not only saves fuel but also reduces reliance on fossil fuels. This approach provides dual benefits: lower operational costs and decreased greenhouse gas emissions.
Moreover, utilizing renewable energy enhances the environmental friendliness of CHP systems and improves market competitiveness.
METHODS
Selecting and Optimizing Turbines for CHP Systems
Choosing the right turbine is critical to CHP system efficiency:
- Back-pressure turbines: Suitable for industries with high and stable heat demand, such as paper production and textiles. These turbines do not prioritize high-efficiency electricity generation.
- Condensing turbines (with steam extraction): Ideal for modern systems that must meet both electricity and heat demands, especially when these needs vary independently (e.g., low steam demand but high electricity needs).
Below are the advantages and disadvantages them when applied to thermal power plants:
| Characteristics | Back-pressure Turbine | Condensing Turbine |
|---|---|---|
| Operating Principle | Exhaust steam exits at a pressure higher than the condensation pressure and can be directly used for heating purposes (e.g., drying, heating). | Exhaust steam fully expands to a very low pressure, with extracted steam available for heating purposes. |
| Priority | Focuses on heat supply; exhaust steam can be utilized for industrial processes. | Primarily generates electricity, with heat supplied through adjustable steam extraction points. |
| Electricity Efficiency | Lower, as steam does not fully expand. | Higher, as maximum energy from steam is utilized for electricity generation. |
| Flexibility Between Electricity and Heat | Less flexible; fixed electricity-to-heat ratio, making it difficult to adapt to changing demands. | More flexible; steam extraction can be adjusted to meet heat demand while maintaining high electricity efficiency. |
| Suitable Applications | When heat is the priority (e.g., drying, heating processes). | When both electricity and heat demand need to be met simultaneously. |
| Investment Cost | Lower, with a simpler system. | Higher, due to a more complex system (requires condenser, recirculating pumps, and steam extraction system). |
| Maintenance and Operation | Easier due to simpler structure. | Requires higher maintenance and operational standards, especially for controlled steam extraction systems. |
| Limitations | Not optimized for electricity production. | High investment cost. |
Key Features:
Back-pressure turbines:
- Ideal for industries with large, stable heat demand (e.g., food drying, textiles, paper production).
- Do not require prioritizing high electricity efficiency.
Condensing turbines:
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- Suitable for industrial power plants combining power generation with heat supply.
- Perform well when heat and electricity demands vary.
Enhancing Steam Parameters in Turbines (for both types of turbines)
Increasing steam temperature and pressure reduces energy consumption for electricity generation and minimizes thermal losses in the condenser. However, improving these parameters often increases material costs for turbines, pipes, and boilers.
Principle:
Increasing the inlet steam temperature and pressure enhances the available thermal energy (enthalpy), allowing the steam to perform more work in the turbine.
Efficiency Gains:
- Higher steam temperatures increase the enthalpy difference during expansion, boosting power output.
- Reduced energy losses (lower entropy) in the cycle.
- Example: Reducing condensation pressure from 0.1 bar (~45°C) to 0.05 bar (~33°C) substantially increases recoverable turbine energy.
Figure 7 – The efficiency increases as the input steam parameter increases.
Reducing Condensation Pressure to Increase Turbine Power Output (for Both Types of Turbines)
Principle:
Reducing the pressure in the condenser through enhanced cooling lowers the exhaust steam temperature from the turbine. This process extends the steam expansion in the turbine, recovering additional energy before the steam condenses into water. At the same time, the lower condensation pressure creates a greater temperature difference between the turbine’s inlet and outlet steam.
Effectiveness:
-
- Increases the enthalpy difference between the turbine’s inlet and outlet, resulting in higher power generation.
- Reduces the heat loss discharged through the condenser, improving power generation efficiency.
Result: Electricity generation efficiency increases due to reduced heat energy loss to the environment.
Example: When condensation pressure is reduced from 0.1 bar (~45°C) to 0.05 bar (~33°C), the energy recovered from the turbine significantly increases.
Integration of Regenerative Feedwater Heaters (for Both Types of Turbines)
Applicable to: Both back-pressure and condensing turbines.
Solution: Extract a portion of the steam from the turbine to preheat feedwater before it enters the boiler.
Benefits:
- Reduces the heat required from the boiler.
- Enhances the Rankine cycle efficiency.
Utilization of Waste Heat (for Both Back-Pressure and Condensing Turbines)
Solution:
- Utilize waste heat from the condenser or exhaust steam to provide thermal energy for applications such as water heating, central hot water production, or operating absorption chillers.
Benefits:
- Improves overall energy utilization efficiency.
Optimization of Steam Extraction Systems (for Condensing Turbines with Steam Extraction)
Solution:
- Adjust the position and flow rate of steam extraction to balance electricity production with thermal demand.
- Use precise control valve systems to meet thermal requirements without significantly impacting power generation capacity.
Benefits: Enhances flexibility and energy efficiency.
Using a Reheat Boiler (for Condensing Turbines)
Solution:
- After partial expansion in the turbine, the steam is reheated in the boiler before continuing expansion.
Benefits:
- Increases power generation efficiency.
- Reduces entropy loss in the cycle.
Integration of Advanced Cooling Technologies (for Condensing Turbines)
Solution:
Apply dry cooling or recirculating cooling systems to lower the condenser’s temperature.
Benefits:
- Reduces condensation pressure.
- Increases power generation capacity.
Increasing the Exhaust Steam Temperature (for Back-Pressure Turbines)
Solution:
- Design a system that utilizes high-temperature exhaust steam (90–120°C) for processes such as drying or heating. Adjust the exhaust steam temperature to match the application requirements.
Benefits: Enhances the overall thermal efficiency of the system.
CONCLUSION
Improving efficiency in cogeneration systems requires a combination of factors, including regular maintenance, equipment optimization, and the utilization of renewable energy. These methods not only improve operational efficiency but also protect the environment and contribute to sustainable development.
By implementing these solutions, cogeneration systems (CHP) can become a powerful tool to conserve energy and reduce emissions effectively.
