Many warehousing and distribution centers operate 24 hours a day, seven days a week. Unfortunately, today's battery-powered forklift trucks interrupt the flow, sometimes needing up to three time-consuming battery changes during the course of a day. Fuel cells are emerging as a cost-effective alternative to battery technology because they last longer, fuel faster, weigh less, and eliminate harmful emissions.
Fuel cells have the potential to effectively lower total logistics cost, said Fuel Cells 2000 program director Jennifer Gangi. They require minimal refilling, and need less maintenance than conventional electric forklifts as there are fewer moving parts and no batteries that require periodic charging.
Fuel cells also ensure steady power delivery and performance, she added. Unlike battery-powered forklifts which slowly decrease in voltage output as batteries discharge, the voltage delivered by fuel cells remains constant.
Moreover, fuel cells do away with the numerous interruptions in current input and output electric forklifts experience due to the frequent starting and stopping during use.
Fuel Cells 2000 (www.fuelcells.org) is an activity of the Breakthrough Technologies Institute, a non-profit, independent, educational organization that identifies and promotes environmental and energy technologies that can improve the human condition.
Energy conversion
Fuel cells were invented more than 100 years ago, said Gangi, but have really just gained attention in the past decade or so.
A fuel cell is an energy conversion device that continuously transforms the chemical energy of a fuel and an oxidant into electrical energy. It combines hydrogen and oxygen to produce electricity, with water and heat as its by-product.
“Since the conversion of the fuel to energy replaces combustion with an electrochemical process, the process is clean, quiet, and highly efficient - two to three times more efficient than fuel burning, she explained. “Think of it as a battery that never runs down or requires recharging. As long as fuel is supplied, the fuel cell will continue to generate power.”
The voltage from a single cell is about 0.7 volts, just about enough for a light bulb. Fuel cells are scalable, so stacking cells together multiplies the operating voltage until the desired power output is reached. Larger stacks can be linked together as well.
When pure hydrogen is used as the fuel source, the fuel cell is a zero emission technology, Gangi said.
“Hydrogen can be generated from a variety of sources. Using a reformer, hydrogen can be stripped from a number of hydrocarbon fuels, including natural gas, methanol, propane, biomass, and gasoline. The emissions from reforming these various hydrocarbon fuels would still be cleaner than those from a combustion process.”
Besides being a potential zero-emission device, she said fuel cells offer numerous other benefits, including high efficiency and reliability, low noise and heat signature, high quality power, and fuel flexibility.
Pem Cells
There are several different types of fuel cells, each using a different chemistry.
One of the most promising for forklifts, especially in high-throughput warehousing and distribution applications, is the hydrogen-fueled proton exchange membrane (PEM) fuel cell, noted Gangi. In addition to having a high power density, this fuel cell has a relatively low operating temperature, meaning it doesn't take very long for the fuel cell to warm up and begin generating electricity.
In research for the US Department of Energy, Battelle Memorial Institute found that PEM fuel cell-powered forklifts on a lifecycle cost basis require approximately 48% to 50% less investment than battery-powered forklifts in applications where forklifts run continuously.
The study also showed that while PEM fuel cell-powered forklifts require more capital investment than present alternatives, they provide significant savings in operation and maintenance. For one thing, shifting from batteries to hydrogen fuel cells increases worker productivity as there is no need to stop and change batteries.
Efficiency Gains
Gangi said recent field tests indicated that hydrogen fuel cell forklifts ran three times as long between fueling, with much shorter refueling times - minutes compared to a half hour or longer to change out a battery. This resulted in “significant increases” in productivity and paybacks on investment of less than four years for many operations.
As for getting hydrogen, she said individual warehouses and distribution centers can install their own hydrogen fueling station inhouse, or use mobile fuel trucks.
“Another advantage of hydrogen fuel cells over conventional technology is weight and mass,” said Gangi. “Batteries are heavy and take up a lot of storage space while only providing up to six hours of run time.
“Fuel cells last more than twice as long - 12 to 14 hours, and there is no more need for battery storage and changing rooms, leaving more warehouse space for products.”
As fuel cell technology evolves and the costs come down, Gangi predicted more and more companies will incorporate fuel cell forklifts into their warehousing operations to reap the potential environmental and economic benefits.
