Cogeneration plant and process
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Solution Overview
Problem
Combined heat and power plants with fuel cell systems face challenges in isolated operation due to rapid load changes, which accelerate aging and increase costs, and existing solutions either exclude peripheral components or use expensive energy storage to mitigate dynamic loads.
Innovation Solution
A controlled resistance load is connected in parallel to the energy source to dissipate excess electrical power as heat, allowing the system to operate continuously while managing dynamic loads and extending the service life of the fuel cell plant, with an inverter arrangement and control electronics regulating voltage and current to maintain constant power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the combined heat and power plant operates in isolated mode with dynamic loads, then the plant can provide emergency power supply and continue operating during grid failures, but the rapid load changes accelerate fuel cell aging and increase system costs
Solution Approach 1:
A controlled resistance load is introduced as an intermediary component between the fuel cell stack and the electrical consumers. This resistance load acts as a buffer that absorbs rapid load changes through controlled power dissipation, preventing direct transmission of dynamic stress to the fuel cell stack while maintaining isolated operation capability.
Solution Approach 2:
The invention converts the potentially harmful effect of excess electrical power (which would otherwise cause rapid fuel cell response and aging) into a beneficial thermal output. The controlled resistance load dissipates fluctuating electrical power as controllable heat, which can be utilized for process heating or water heating, thereby extending fuel cell life while maintaining isolated operation.
2Adaptability or versatility
If the fuel cell system is designed for maximum dynamics to handle isolated operation, then the plant can respond to load changes, but the costs for components increase and stack degradation accelerates
Solution Approach 1:
The controlled resistance load serves as a cost-effective intermediary that provides the necessary dynamics for isolated operation without requiring expensive modifications to the fuel cell stack or control systems. The resistance load absorbs dynamic stress, allowing the use of standard, lower-cost fuel cell components.
Solution Approach 2:
The invention uses a relatively simple and inexpensive resistance load (such as heating elements or resistors) to handle the dynamic stress that would otherwise require costly, specialized fuel cell components. The resistance load is a consumable component with lower cost and simpler replacement compared to upgrading the entire fuel cell system for maximum dynamics.
3Power
If excess electrical power is dissipated without utilization, then the system can maintain constant power delivery, but energy efficiency is reduced
Solution Approach 1:
The invention transforms the wasted excess electrical power into useful thermal energy through the controlled resistance load. Instead of simple dissipation, the electrical energy is converted to controllable heat output that can be utilized for process heating, water heating, or space heating, thereby maintaining constant power delivery to the fuel cell while improving overall energy efficiency.
Solution Approach 2:
The controlled resistance load provides multiple functions simultaneously: it maintains constant power delivery to protect the fuel cell, converts excess electrical energy to thermal energy, and provides controllable heat output for various thermal needs. This multi-functionality eliminates the trade-off between power stability and energy efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the combined heat and power plant to maintain operation during isolated conditions with dynamic loads while ensuring a long service life for the fuel cell system, improving efficiency and reducing costs by converting excess power into usable heat for the plant's processes.
Implementation Method 1
A controlled resistance load (12) is connected in parallel to the energy source (2)... dissipate excess electrical power as heat
Implementation Method 2
a fuel cell stack with at least one fuel cell... Combined heat and power plants with solid oxide fuel cell systems have a relatively high electrical efficiency of up to 60%
Implementation Method 3
an inverter arrangement, by means of which the direct current from the energy source is converted into alternating current that conforms to the grid
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a combined heat and power plant (1) for providing electric power and heat, wherein the heat can be supplied to at least one process in which heat is used. The combined heat and power plant (1) has an electric energy source (2), in particular a fuel cell stack having at least one fuel cell (26), and an inverter system (3) downstream of said energy source (2) for connection to an electrical consumer (4), in particular a power grid. In order to, during island operation, be able to continue to operate the combined heat and power plant (1) while at the same time supplying one or more dynamic loads, the inverter system (3) has a controlled resistance load (12) connected in parallel to the energy source. A sum of the electric power supplied from the energy source (2) to a consumer (4) and the electric power consumed by the resistance load (12) is kept constant, wherein power not needed by the consumer (4) is dissipated by controlling the resistance load (12).