Suitability of PEM fuel cells for underground mining vehicles
Hydrogen fuel cells are a known technology, having been applied to stationary (e.g. equipment, buildings, and power plants) and vehicle applications (e.g. transit buses and space shuttles). There is currently a growing need to provide alternate power systems to diesel fuel for underground mining vehicles to improve underground air quality and reduce production costs and greenhouse gas emissions.
Fuel cells offer a total solution, reducing heat and noise generation as well as having no emissions, contrary to diesel engines. They produce water and electricity. Fuel cells are electro-chemical devices that directly convert the chemical energy of hydrogen fuel into electric power.
Fuel cells have not been exposed to underground mine air and physical conditions. A testing program was carried out to provide information on the vulnerabilities of fuel cells as part of a number of proof-of-concept projects to apply hydrogen power to underground mining vehicles. The fuel cell type of choice for the industry, the Proton Exchange Membrane, would function at the range of temperatures encountered in underground and surface operations, and use hydrogen that is stored under low pressure and risk.
A small fuel cell stack was tested in a cooperative project between CANMET Mining and Mineral Sciences Laboratories, the Fuelcell Propulsion Institute, Inco, the Ontario Ministry of Labour, Sandia National Laboratories, and H-Power. The tests were carried out to collect information on the electrical output, material resistance, and physical resistance of a 35 W output power plant under representative mine operating conditions. Exposure of the system to dust could result in unwanted dust accumulation on fuel cell membranes, air and hydrogen delivery pathways, and corrosion of membranes from sulphide dust and water concentrations, which would reduce the production of electricity and life of the system; gases may similarly corrode the fuel cell membrane, or at certain concentrations, prevent the hydrogen from being delivered to the membrane surface. Exposure of the fuel cell stack to representative shock and vibration could affect the sealed state of the stack or misalign or fracture cell frames.
The measure of the impact of the underground tests were quantified using the consistency of the power output of the fuel cell stack through the voltage-amperage output (V-I curve), the physical integrity of the stack, as well as accumulation and contamination on the power plant parts and cell membranes as identified through visual inspection. The tests were carried out at Inco’s 175 Orebody mine site and Stobie mine.
Environmental monitoring of dust (mineral and diesel particulate matter) and gases (H2, CO, CO2, NO, NO2, and SO2) was carried out. The water from the fuel cell was also collected for analysis. Tests were carried out with an operating fuel cell placed on the drift wall of draw point with a diesel LHD moving muck back and forth, tele-operated from surface. While inoperative, the stack was placed over a rear wheel of the LHD chassis on a rigid part of the frame and the vehicle carrying out normal duty cycles. An accelerometer to quantify the imposed shock and vibration and the fuel cell stack was installed on the same metal plate.
The test results provided showed that the unit was not affected by the underground conditions; physically and electrically the unit performed without any reduction in operation or adverse effects imposed. No hydrogen leaks occurred. No physical or chemical damages were recorded on the fuel cell stack after inspection. While the fuel cell air intake was filtered, the effluent water collected from the operating stack contained small amounts of mineral dust. This is indicative that the stack was able to flush particles that were present.