• maintain the rapid pace of progress in fuel cells;

• expand the markets and applications in which hydrogen-powered fuel cells can compete;

• enable the use of lower-cost hydrogen from diverse and environmentally friendly sources;

• enable highly efficient hydrogen production;

• reduce the cost of hydrogen delivery;

• reduce the costs of hydrogen storage technologies; and

• develop novel, advanced hydrogen storage technologies.

Full commercialization of fuel cell systems using hydrogen will require advances in hydrogen storage technologies. Developing systems to enable lightweight, compact, and cost competitive hydrogen storage will help make hydrogen fuel cell systems competitive in a wide range of portable and stationary applications, and enable longer driving ranges for a wider variety of transportation applications.

While hydrogen has the highest energy content per unit weight of any fuel, it has very low energy content per unit volume. This poses a challenge as increasing the energy content per unit volume for gaseous hydrogen storage requires either very high pressures or low temperatures. However, materials that bond to, or adsorb hydrogen, enable storage at high density in a compact container and at less severe conditions.

While the energy density challenge exists for all fuel cell installations that use hydrogen, the problem is most acute for light-duty vehicles where the storage systems must: operate within stringent size, weight and cost constraints; enable a driving range of more than 300 miles (generally regarded as the minimum for widespread driver acceptance based on the performance of today’s gasoline vehicles); and refuel at ambient temperatures fast enough to meet drivers’ expectations (normally only a few minutes). Most of the hydrogen that is used today is stored as a compressed gas (with pressures typically ranging from 150 to 700 bar) or a liquid (liquid storage requires cryogenic temperatures near 20 K).

The majority of the fuel cell vehicles in today’s demonstration fleets use high-pressure tanks rated at 350 or 700 bar for onboard storage of hydrogen gas. These tanks are more expensive, heavier, and require more volume than conventional fuel tanks. While possibly adequate for some stationary applications and vehicle platforms, they may be too expensive and bulky for many non-stationary applications and may not be able to provide a driving range that meets consumer expectations across the full range of light-duty vehicle platforms. In addition, the costs associated with high-pressure fast refueling adds to the overall costs associated with using hydrogen fuel cells. Therefore, to maximize the use of hydrogen as a zero-carbon fuel for fuel cells, advanced storage systems and technologies will be required, especially for automotive applications.

—DE-FOA-0000827

The FCTO is focused on the R&D of materials and approaches that will enable widespread commercialization of fuel cell systems for diverse applications across stationary, portable, and transportation sectors. R&D is concentrated on low-pressure, materials-based technologies and lower-cost, high pressure tank technologies for hydrogen storage systems to meet performance targets.

Three overarching performance targets for onboard hydrogen storage systems are: gravimetric capacity; volumetric capacity; and system cost. For 2017, the targets are 1.8 kWh/kg (5.5 wt.% H₂); 1.3 kWh/L (40 g H₂/L); and $12/kWh ($400/kg H₂ stored).

The Ultimate Full Fleet targets are 2.5 kWh/kg (7.5 wt.% H₂); 2.3 kWh/L (70 g H₂/L); and $8/kWh ($267/kg H₂ stored).

DOE targets for hydrogen storage. Click to enlarge.

As an example of the challenges these system targets represent, hydrogen gas alone (not including the tank) at 700 bar pressure and ambient temperature has a density of approximately 40 g/L, and thus is theoretically not able to meet the 2017 system level volumetric target when the volume of tank and rest of the system is included. Liquid hydrogen alone at its normal boiling point of 20 K has a density of 71 g/L, and also consequently is theoretically not able to meet the Ultimate Full Fleet volumetric target for the full system.

Projects funded through the FOA will be incorporated into FCTO’s applied hydrogen storage portfolio. The office encourages collaborative approaches with teaming across multiple entities including university, industry, and/or national labs with complimentary disciplines and expertise necessary for a holistic approach.

The FOA includes the following topics:

• Topic Area 1: Reducing the cost of compressed hydrogen storage systems. This includes, but is not limited to, novel tank designs and cost reduction concepts; carbon fiber reduction or elimination; Type III and Type IV tanks with alternative liner materials; conformable tank designs; alternative operating conditions (e.g., different operating pressure, or cold/cryogenic compressed hydrogen); and advanced state-of-the-art compressed tank manufacturing.

  The goal is to develop lower cost hydrogen storage systems, when compared to current 700 bar ambient temperature Type IV COPV systems, with the potential to achieve the 2017 ($12/kWh) and Ultimate Full Fleet ($8/kWh) hydrogen storage on-board, automotive cost targets, when manufactured at rates of 500,000 systems per year.

  A vehicle that achieves a fuel economy of 60 miles per kilogram of hydrogen (i.e., 60 miles per gallon gasoline equivalent), would require a useable hydrogen storage capacity of 5 kilograms or 167 kWh (at a lower heating value of 33.3 kWh per kilogram H₂) to meet a 300-mile driving range goal. This equates to about $2,000 and $1,300 for the complete vehicle hydrogen storage system at the 2017 and Ultimate target levels, respectively, which is approximately an order of magnitude higher than current conventional gasoline systems.

• Topic Area 2: Improved materials for fiber composites and balance of plant components. Currently, high-pressure (i.e., 350 to 700 bar) storage vessels are constructed using expensive high-strength carbon fiber. Strategies to lower the cost of high-pressure hydrogen storage COPVs include a reduction in the cost of the fiber composite either through the reduction in the cost of carbon fiber; substitution of the high-cost carbon fiber with lower cost alternatives; reduction in the amount of carbon fiber composite required; or through a combination of the above approaches.

  Approximately 50% of the cost of carbon fiber production is due to the precursor fiber with the other 50% due to the conversion processing. Low-cost carbon fiber precursors, low-cost carbon fiber manufacturing processes, and/or alternative structural materials such as glass or other inexpensive fibers are all potential solutions to reducing the overall system tank costs to meet the DOE 2017 performance and cost targets for onboard vehicle hydrogen storage.

  The overall performance of carbon fiber composites may also be improved through the use of fillers added to the composite that, for instance, improves the load sharing between the fiber and the resin matrix, thus reducing the amount of carbon fiber required to produce a composite of specified strength.

  The required BOP (balance of plant) components which are currently specialty components built in low-volumes from primarily 316L stainless steel are also a leading cost-contributor. Innovative concepts to identify materials for use in BOP components that are compatible for hydrogen service, and reduce the cost, weight and volume of the BOP are also sought.

• Topic Area 3: New hydrogen storage materials discovery. FCTO remains committed to the discovery, characterization, and development of advanced hydrogen storage materials. Analyses have shown that a reversible metal hydride with an enthalpy of hydrogen release of around 27 kJ/mol of H₂ and sufficient release kinetics at a temperature that waste heat from the fuel cell (i.e., 80 °C or less) can be used to provide the heat of desorption, must have a useable material gravimetric capacity of at least 11 wt.%.

EERE expects to make at least $4 million of Federal funding available for 2 to 4 new awards in FY14 under this FOA subject to the availability of appropriated funds.