Fuel Cell-Battery Hybrid Golf Cart
The Project
The purpose of the Fuel Cell-Battery Hybrid Golf Cart project is to educate our members and the community at large about the practical applications of hydrogen power in a mobile system. Funded by an $20,000 IRA fund for the 07/08 school year, the system is designed to be built from mostly off the shelf components.
Mobile Power Platform
The entire fuel cell system, including fuel cell stack, storage containers, and control electronics, are entirely separate from the main body of the golf cart. Designed to be "plug and play", these components will be housed in a specially designed compartment that will be easily removable. By making the fuel cell portion of the hybrid power system removable, we allow lab testing to be done on the system without needing to take apart the golf cart. Future phases, with the inclusion of an AC/DC converter, will allow the use of this compartment as a mobile generator, serving as a demonstrator unit for static technology as well.
The Fuel Cell System
The fuel cell system we've decided on is based on the Nexa Power Module built by Ballard Power Systems and distributed by Heliocentris.
Nexa Power Module
The Nexa Power Module is the first mass-produced, publicly available fuel cell on the market. It is designed for use in mobile applications and is the preferred educational test-bed for many universities and government programs. It has an peak power output of 1.2 kW and has many integrated control systems to make it safe and easy to use. Humidity, voltage, cooling, gas compression, and several safety systems come integrated into the module. It also has the ability to output measurements of these parameters to a computer using a serial data port and specialized software. We've deemed this the optimal option for our project, and we're not the only ones! NASA's Glenn Research Center has built a very similar vehicle utilizing two of the Nexa Power Modules. See the report here.
DC/DC Converter
Because the nominal output voltage (24V) of the Nexa Power Module is anything but stable, a DC/DC converter is necessary. Heliocentris offers one that is specially designed for the Nexa and for use in hybrid systems. The electronics not only provides a stable output voltage for the system but includes a serial port for data acquisition and power management electronics for battery/fuel cell hybrid operations. This makes it perfect for our uses.
Ovonics Metal Hydride Storage Tanks
Three 900L Ovonics Metal Hydride tanks store enough fuel to operate the Nexa for up to 150 minutes. This allows us to space out refueling times which are time consuming and faintly dangerous. These tanks are the safest and most practical means of storing hydrogen in mobile applications. They provide a flow rate perfect for the system and are able to store more fuel than similarly sized compressed hydrogen tanks. For more information on metal hydride storage, see this article at Wikipedia
The Golf Cart
We've chosen to use a 1997 Club Car Golf Car as our mobile base for this project. We'll modify the cart to support our Mobile Power Platform design.
Phase II
Future phases of the project will expand the Mobile Power Platform to include a second Nexa to increase the peak power output to 3.4kW, much decreasing the load that batteries in the current design have to cover during peak power usage. We will also add a "generator" element to the platform, allowing the use of AC power for use as a demonstrator unit. The batteries in the hybrid system will be replaced with ultracapacitors that have much greater flexibility in a system like this. Ultracapacitors can be charged/discharged much more quickly and for an indefinate amount of cycles and are much faster to respond to changes in the load. An IRA funding proposal to complete Phase I and move on to Phase II for the 08/09 school year.