Vehicle Efficiency and Fuel Cell Balance of Plant System 

John Deere Corporation wants to assess the possibilities of using fuel cell systems on their tractors to make them more efficient.  First, background research on vehicle systems and efficiencies will be assessed.  Next, the fuel cell systems will be assessed with focus on the balance of plant (BOP) system.  The BOP system is a supporting system, which is needed for the fuel cell to produce energy, but does not generate any energy itself. 

Vehicle efficiency depends on two types of energy loss, heat loss and mechanical loss.  Heat loss is simply heat energy transferred to the surroundings.  Mechanical loss comes in the form of friction and pumping loss (in an internal combustion engine air and fuel must be pumped in and pumped out of the cylinders by the pistons).  Figure 1 is a schematic diagram that shows the losses of different components, which effect overall vehicle efficiency.

	Schematic diagram of powertrain with associated power losses. [1]

 

In a fuel cell, the balance of plant system is responsible for compressing air that is taken into the reactor, circulating cooling air, and processing information with electronic controls.  Some parts of this system are compressor and expander units, intake and exhaust systems, startup battery, and in some analysis, the fuel reformers.  Figure 2 shows a fuel cell system with some BOP components.  Research will be conducted to learn about all the components and the power losses associated with them.  This research will be directly used to build the computer model that will simulate fuel cell use in a powertrain of a vehicle.

Fuel Cell System: A) reactant air pump; B) humidifier; C) fuel cell stack; D) blower that blows air to cool stack; E) pump to pump fuel.  A, B, D, and E are part of the Fuel Cell Balance of plant system, while C is where the chemical reaction takes place. [2]

References

1. United States Department of Energy. April 20, 2003 <http://www.fueleconomy.gov/feg/atv.shtml>.

2. Larminie, James and Andrew Dicks.  Fuel Cell Systems Explained.  Wiley Publishers, 2003