Fuel Cell System Water Self-Sustaining Control
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Solution Overview
Problem
Fuel cell systems face challenges in generating a sufficient quantity of condensed water, especially when operated at low S/C (fuel to oxidizer ratio), leading to an imbalance in latent heat/sensible heat ratios, which affects water self-sustaining states and power generation efficiency.
Innovation Solution
A fuel cell system incorporating a reforming unit, combustion unit, hot water storage tank, heat exchanger, and control device that adjusts the delivery quantity of stored hot water to optimize the temperature of the heat exchanger outlet, ensuring a sufficient quantity of condensed water is produced by controlling the target temperature based on the water self-sustaining state determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fuel cell system is operated at a low S/C ratio to achieve high efficiency, then power generation efficiency is improved, but the latent heat/sensible heat ratio in exhaust gas becomes smaller and insufficient condensed water is generated
Solution Approach 1:
The control device changes the target temperature parameter of the heat exchanger based on the water self-sustaining state determination. When condensed water quantity is insufficient, the control device adjusts the target temperature to optimize heat exchange conditions, enabling sufficient condensed water generation while maintaining high efficiency operation at low S/C ratios
Solution Approach 2:
The system implements feedback control by determining the water self-sustaining state based on actual condensed water generation and adjusting the heat exchanger target temperature accordingly. This closed-loop control ensures that condensed water quantity requirements are met while maintaining optimal power generation efficiency
2Quantity of substance
If the target temperature of the heat exchanger is decreased to increase condensed water production, then condensed water quantity is improved, but the temperature of stored hot water led out from the heat exchanger decreases
Solution Approach 1:
The target temperature of the heat exchanger is made dynamic rather than fixed. The control device continuously determines the water self-sustaining state and adjusts the target temperature accordingly, allowing the system to optimize between condensed water generation and hot water temperature delivery based on real-time operational conditions
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 configuration effectively increases the production of condensed water, even when the latent heat/sensible heat ratio is small, ensuring a necessary and sufficient quantity for power generation and maintaining a water self-sustaining state, thereby enhancing the system's efficiency.
Implementation Method 1
a heat exchanger that performs heat exchange between the combustion exhaust gas and the stored hot water
Implementation Method 2
condenses water vapor contained in the combustion exhaust gas
Implementation Method 3
a delivery device that is provided in the stored hot water circulation line and delivers the stored hot water to be circulated
Implementation Method 4
a heat exchanger stored hot water outlet temperature sensor that is provided between a stored hot water lead-out port of the heat exchanger and a stored hot water introduction port of the hot water storage tank and detects the temperature of the stored hot water led out from the heat exchanger
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A fuel cell system (1) includes: a fuel cell (34) generating power by fuel and oxidizer gas; a reforming unit (33) generating the fuel from a reforming raw material and reforming water and supplying the fuel to the fuel cell; a combustion unit (36) introducing combustible gas containing unused fuel from the fuel cell thereinto, burning the combustible gas, and leading out the combustion exhaust gas; a hot water storage tank (21); a heat exchanger (12) exchanging heat between the combustion exhaust gas and stored hot water, condensing water vapor in the combustion exhaust gas, and producing condensed water; a stored hot water circulation line (22) circulating the stored hot water; a delivery device (22b) provided in the stored hot water circulation line and delivering the stored hot water; a heat exchanger stored hot water outlet temperature sensor (22d) detecting the temperature of the stored hot water; and a control device (15) controlling the delivery quantity of the delivery device.