Electricity: battery or capacitor charging or discharging – Wind – solar – thermal – or fuel-cell source
Reexamination Certificate
2001-08-31
2004-09-21
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Wind, solar, thermal, or fuel-cell source
Reexamination Certificate
active
06794844
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a fuel cell system for power generation and more particularly to a method for controlling fuel cell outputs to be compatible with an energy storage device.
BACKGROUND OF THE INVENTION
Fuel cell systems offer many advantages over conventional sources. In a fuel cell, electricity is generated electromechanically through the reaction of hydrogen with oxygen. The only reaction emission involved is water vapor, which is essentially harmless to the environment. This is in contrast to a conventional power generation system, which releases harmful emissions such as hydrocarbons, carbon monoxide and other chemicals.
Fuel cell systems that are used for power generation must be controlled to meet electrical demand under normal, as well as transient, operating conditions. Long term fluctuations in the external load must be taken care of within the fuel cell system through the system controls that lead to fuel and oxidant energy input and output.
The fuel cell power generation systems are typically complex in that they require a power conversion stage for interfacing the fuel cell and energy storage. The power conversion stage modifies the output voltage of the fuel cell to be compatible with the load or with additional power conversion stages such as an inverter. Efficiency losses are incurred and additional cost added for each power conversion stage. Therefore, these power generation systems tend to be very costly.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for controlling a fuel cell system. It is another object of the present invention to reduce the overall cost of a fuel cell power generation system by eliminating the need for multiple power conversion stages. It is a further object of the present invention to manipulate fuel cell system variables in response to the total power load on the fuel cell in combination with an energy storage device.
In carrying out the above objects and other objects and features of the present invention, a control system and a method are provided for separately controlling variables such as the mass flow, pressure, temperature, humidification, and utilization of air and fuel, to adjust the voltage of a fuel cell stack. According to the present invention, the fuel cell is directly paralleled to the energy storage device without the need for a power conversion stage. The fuel cell voltage is controlled in such a manner that it is made compatible with voltage characteristics of the energy storage device as a function of load current and the state of charge of the storage device.
The present invention may be useful in low cost, hybrid battery systems, where a fuel cell is partnered with an energy storage device. In such devices, the fuel cell provides long term power and the energy storage device provides peaks of power and/or the ability to store power regenerated from the load.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.
REFERENCES:
patent: 3987352 (1976-10-01), Hirota
patent: 4961151 (1990-10-01), Early et al.
patent: 5916699 (1999-06-01), Thomas et al.
patent: 6087812 (2000-07-01), Thomas et al.
patent: 6628011 (2003-09-01), Droppo et al.
patent: 0136187 (1985-04-01), None
patent: 1160120 (2001-12-01), None
patent: 2002-34171 (2002-01-01), None
patent: WO 02/25761 (2002-03-01), None
Hochgraf Clark
Singh Prabhakar
Kajander John E.
Tso Edward H.
Visteon Global Technologies Inc.
LandOfFree
Method and system for fuel cell control does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for fuel cell control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for fuel cell control will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3232896