GM’s newly announced hydrogen fuel cell concept vehicle, the Sequel (earlier post), is big.

Slightly larger in its dimensions than the Cadillac SRX crossover or Chrysler’s 300C, the Sequel weighs much more than either: 4,774 pounds compared to 4,164 for an SRX or 3,758 for the 300C.

Yet GM engineers have designed a new fuel cell power system that moves the Sequel along from 0–60 mph in less than 10 seconds and supports a 300-mile range.

GM’s goal is to design and validate a fuel cell propulsion system by 2010 that is competitive with current internal combustion systems on durability and performance, and that ultimately can be built at scale affordably.

We’ve achieved remarkable gains in range and acceleration by using our fuel cell system technology that exists today. That’s a real breakthrough. For anyone tracking the viability of fuel cell vehicles, this is encouraging news.

Today, with Sequel, the vision is real—not yet affordable, but doable.

—Larry Burns, GM vice president of research and development and planning

The Sequel combines a new fuel cell system, higher-pressure hydrogen storage, enhanced by-wire controls substituting for mechanical systems and new rear-wheel hub motors to deliver the large-vehicle-equivalent performance GM is seeking.

The GM-designed fuel cell delivers 25% more power than its predecessor in the Hy-Wire. The fuel cell power module consists of the fuel cell stack, the hydrogen and air processing subsystems, the cooling system and the high-voltage distribution system. This power module delivers 73 kW of high-voltage power for the electric traction motors, as well as auxiliaries like HVAC (heating, ventilation and air conditioning), the by-wire electronics and the battery.

The new fuel cell also uses a new air intake system that is more efficient, quieter and lighter than its predecessor. Additional radiators are located under the Sequel’s hood, directly behind the headlights, and in the rear of the vehicle, behind the taillights. These necessary design features help pull heat away from the fuel cell system, allowing Sequel to operate in hotter ambient temperatures.

A fuel cell system is more efficient than an internal combustion engine, but its energy conversion is totally different and requires much more heat to be removed via the coolant. With its three openings in the front, the extra opening for the HVAC and the two additional openings in the rear, you can easily recognize that Sequel was designed for heat rejection. We expect excellent performance at high ambient temperatures, typical of what you would experience in the desert.

—Lothar Matejcek, project manager, GM Fuel Cell Activities, Mainz-Kastel

The Sequel uses three traction motors—a single transverse-mounted motor in the front and two rear wheel hub motors—that deliver a total of 110 kW of power.

The front traction system incorporates a 60 kW electric motor from Siemens that delivers 1,740 lb-ft (2,350 Nm) torque at the wheels. The system incorporates the requisite power electronics and planetary gear.

The rear traction system includes the twin 25 kW rear wheel hub motors (designed by GM), and power inverters. Each wheel hub motor delivers 369 lb-ft (500 Nm) of torque, giving the Sequel total torque at wheels of 2,506 lb-ft (3,398 Nm).

A 65 kW Li-Ion battery system from Saft provides extra power to the three electric motors during acceleration. It also stores power regenerated during braking to help extend the vehicle’s overall mileage range.

Advances in high-pressure hydrogen storage, developed by GM in conjunction with Quantum Technologies, support Sequel’s 300-mile range. Three lightweight, carbon composite tanks store hydrogen at 10,000 psi (700 bars), compared to 5,000 psi (350 bars) in Hy-wire, Sequel's concept predecessor. Sequel can carry 8 kg of hydrogen, more than double that of GM’s HydroGen3 fuel cell vehicle. The larger tanks also enable a better ratio of stored hydrogen mass versus fuel storage system mass.