Fuel cells plugged for forklifts

  • 04-Oct-2011 10:42 EDT
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Yale is among the forklift manufacturers that accommodate Plug Power GenDrive fuel-cell systems, which are designed to run for a full 8-h shift without refueling.

While engineers in almost all companies involved in designing parts and systems for vehicles are sweating over weight reduction, their counterparts at Plug Power are metaphorically sitting back and fanning themselves. They have many things to worry about, but mass reduction isn’t one of them.

In fact, for Plug Power’s main end-use customer base, mass reduction is frowned upon. Material-handling equipment such as forklifts wouldn’t be of much value if they did not have a heavy counterweight.

The fuel-cell systems that Plug Power delivers to end-use customers—including Walmart and Coca-Cola, and other companies for whom material-handling activities are extensive—are more dead weight than anything else. A steel or cast-iron housing for the fuel-cell system accounts for about 50% of the product’s weight. The actual fuel-cell stack accounts for only about 10%, with the remainder including a hydrogen tank, battery, cooling system, electronics, etc.

Forklifts with electric propulsion motors are designed so the batteries (or fuel-cell system) that powers them serve as the counterweight. In that respect, battery or fuel-cell systems can be thought of as aftermarket products, and so for Plug Power and its competitors the end user is the customer, not the forklift maker. Large and heavy lead-acid battery packs traditionally have been used, but much lighter fuel-cell systems have made deep penetration because of the efficiencies they offer.

Plug Power’s GenDrive fuel cell is engineered as a replacement product, so a big lead-acid battery array can be removed from a forklift and a GenDrive unit plugged in with no modification to the vehicle.

Plug Power is not alone in offering a fuel-cell solution to supply power for material-handling equipment, but it is the most successful with an 85% market share, said Dustan Skidmore, Director of Systems Engineering, in an interview with SAE Off-Highway Engineering. The GenDrive, the Latham, NY-based company’s solution, pairs a Ballard proton exchange membrane fuel cell with a lithium-ion battery designed and assembled by Plug Power in America using cells supplied from China by MGL. Some competitors use different types of fuel-cell and battery technology (including lead-acid) combinations.

Plug Power’s approach is to use a large fuel cell and a small battery, which has several advantages, said Skidmore, a 13-year company veteran. For one thing, the fuel-cell system is able to constantly charge the battery. That’s a huge improvement over a solution using lead-acid batteries, which are so heavy they must be craned off forklifts and placed on shelves for more than 8 h to recharge. That means more than one battery pack is needed for each forklift, and it means a vast amount of floor space—100,000 ft² (9000-m²) in some cases—must be dedicated to battery recharging.

Another disadvantage in operations that run longer hours is that some of the charging must take place during day shifts when utility rates are high. Perhaps even more detrimental is the fact that the battery-swapping operation takes time. There is no battery swapping in Plug Power’s solution, as the Li-ion battery pack and fuel-cell system are designed for a life of 10 years.

Instead of battery swapping, GenDrive requires hydrogen refueling. Hydrogen is the fuel for the fuel cell. Refueling takes about 120 s. Skidmore noted that hydrogen refueling stations are small and so several of them can be deployed throughout a facility. In comparison, some facilities using lead-acid battery technology have only one large swap station (because of their large size) and operators must wait their turn for time-consuming battery swapping.

No wonder companies with large-scale material-handling operations have moved to fuel-cell technology. Skidmore noted that fuel cells are not as good a solution for smaller operations because of the high cost of hydrogen distribution. But it is for larger operators who can amortize the cost across many vehicles.

The up-front cost of a fuel-cell system is higher than that of a lead-acid system, he acknowledged, but that expense is recouped via higher productivity and lower overhead expenses.

Skidmore said Plug Power is exploring opportunities in other industries, including airport tugs.

In addition to seeking new markets, the company is working with its OEM partners toward better integration of fuel cells with the forklift. “We’ve just started to scratch the surface” in that regard, Skidmore said. He’d like to see the trucks “designed around fuel-cell systems, which I think will happen someday.” He’d also like to see manufacturers incorporate counterweight into the base vehicle architecture instead of accounting for it via the fuel-cell system.

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