Within the bounds of the delivery system, hydrogen is conditioned to permit bulk transport as a compressed gas or as a liquid; shipped via a bulk transport mode (e.g., transmission pipeline or truck) to a terminal where it may be further conditioned, stored, or transferred to a local distribution mode; and delivered to a refueling station where it is dispensed onto vehicles.

The H2A Delivery Components model focuses on components required to deliver liquid hydrogen or compressed hydrogen gas from a central production plant or distributed production unit to the nozzle of the dispenser. At this point, novel storage and delivery technologies, such as hydrogen carriers, are not modeled. The components that are modeled in Version 2.0 of the tool are listed below.

Pathway-Specific Components

• Truck—compressed hydrogen gas tube trailer (2700 psi)

• Truck—liquid hydrogen tanker

• Pipeline

• Liquefier

• Compressor (single-stage or multi-stage units)

Bulk Storage Components

• Compressed gas tube

• Bulk liquid tank

• Geologic/underground cavern

Transmission/Distribution Interface Components

• Pipeline to gas terminal (with either geologic or liquid storage for plant outages and demand surges)

• Pipeline to liquid terminal (with either geologic or liquid storage for plant outages and demand surges)

• "Pure" liquid H2 terminal (with either geologic or liquid storage for plant outages and demand surges)

• "Pure" gaseous H2 terminal (with either geologic or liquid storage for plant outages and demand surges)

Refueling Station Components

• Compressor

• Dispenser

• Daily storage (either in low-pressure vessels or as components of cascade charging system)

Integrated Refueling Station

• Gaseous (containing integrated compressor, cascade compression/dispensing, and storage)

• Liquid (containing integrated storage, vaporizer, and cascade compression/dispensing)

The model is written as a Microsoft Excel spreadsheet with a separate tab for each of the delivery components. The model calculates the cost contribution of each component within the delivery infrastructure to the $/kg cost of delivering hydrogen. This cost contribution is based on inputs provided by the user describing the amount of hydrogen to be delivered and basic capital and operating costs for the component.

Version 2.0 contains default values that represent currently available (2005) technologies and costs. These parameters can be changed by the user to simulate advancements in technology and changes in other costs.

Using the H2A Delivery Carriers Components Model

Hydrogen carriers have been under intense investigation for their potential to meet the DOE on-board storage goals. Potential alternative hydrogen carriers include metal hydrides, chemical hydrides, high-surface-area carbon sorbents, and liquid-phase hydrocarbons. While these alternative hydrogen carriers have the potential to provide on-board storage, they may also be used to improve the efficiency and cost of hydrogen delivery to refueling stations. Certain hydrogen storage technologies may not meet all of the requirements for use on-board vehicles but may be viable for hydrogen delivery because delivery components have less restrictive requirements than on-board storage regarding their volumetric and gravimetric capacity.

A hydrogen carriers' model was developed in Microsoft Excel to evaluate the cost associated with various carriers' delivery pathways. It serves as a tool to examine the cost of components associated with different pathways (liquid truck, solid-state truck, pipeline, etc) in which various carriers can be used for hydrogen delivery, to establish which components contribute significantly to the delivery cost, and to provide ranges for the characteristics of each component. The model has been developed in the H2A tools format and incorporates many of their features. The model contains macros that are necessary for proper operation.

H2A Delivery Scenarios Analysis Model

Like other H2A-developed tools, the Hydrogen Delivery Scenario Analysis Model (HDSAM) uses an engineering economics approach to cost estimation. For a given scenario (discussed below), a set of "components" (e.g., compressors, tanks, tube trailers, etc.) is specified, sized, and linked into a simulated delivery system or pathway infrastructure. Financial, economic, and technological assumptions are then used to compute the levelized cost of those components and their overall contribution to the delivered cost of hydrogen. Version 2.0 contains default values that represent currently available (2005) technologies and costs and current population and infrastructure characteristics. These parameters can be changed by the user to simulate advancements in technology and changes in other costs or relevant characteristics.

As in the H2A Delivery Components model, hydrogen delivery is defined to include the entire process of moving hydrogen from the gate of a central production plant onto a vehicle. Thus, delivery includes all transport, storage, and conditioning (e.g., compression, liquefaction, or for hydrogen carriers, hydrogenation/reprocessing of spent material) from the outlet of a centralized hydrogen-production facility to and including a refueling station that compresses, stores, and dispenses the hydrogen. Hydrogen delivery could also include compression, storage, and dispensing of hydrogen produced on site at a forecourt (e.g., distributed production). The current version of HDSAM (V2.0) does not model distributed production scenarios or hydrogen carrier pathways. Future versions of the model will include these options.

HDSAM draws upon the engineering economics calculations in the H2A Delivery Components Model. In effect, many of the "component" spreadsheets (or tabs) within the Delivery Components Model are embedded in HDSAM, which links them into appropriate combinations to define a delivery pathway, size the individual components consistent with a scenario's demand estimate, and calculate the cost associated with delivering a given quantity of hydrogen via the specified pathway.

Delivery Scenarios

The user defines a scenario by selecting a market type (e.g., urban, rural interstate, or a combination of the two); specifying its size, location (either a generic urbanized area of defined population or any of over 400 urbanized areas contained in a drop-down menu), and the market penetration of hydrogen-fueled vehicles in the total population of light-duty vehicles; selecting delivery modes for bulk transport from a production facility to a city gate and for local distribution; specifying a type of storage for plant downtimes and surge demands; and indicating a desired refueling station size.

Market size can vary from an urbanized area of 50,000 people to one of over 20 million people, and from an interstate highway segment of 10 mi. to 300 mi. (1000 mi. for pipeline delivery). Market penetration can vary from 1% to 100%. Bulk transport can be via gaseous tube trailer, liquid hydrogen truck, or gaseous pipeline. Local distribution is generally via the same mode; however, for bulk transport via pipeline, local delivery may also be accomplished by any other mode.

Storage for plant outages and surge demands can be in geologic formations or as liquid hydrogen, and refueling stations can range from 50 kg to 6000 kg of hydrogen dispensed per day. Thus, delivery scenarios are combinations of (a) markets, (b) market penetrations, (c) delivery modes, (d) downtime storage, and (e) refueling station size, with an associated set of assumptions about market demand and infrastructure.

In reality, however, delivery scenarios are even more variable. The user can define a scenario further by changing such default values as the distance from a central production facility to the edge of the urban area, the average fuel economy of hydrogen and conventional light-duty vehicles, the city's rates of motorization (e.g., vehicles per person) and vehicle utilization (e.g., miles driven per vehicle per year), financial assumptions, and the characteristics and cost of any component in the delivery pathway.

Delivery Pathways

Within HDSAM, user selection of a delivery mode invokes an associated chain of delivery "components" or processes required to satisfy market demand. For example, if the user selects liquid hydrogen truck delivery (with liquid storage for plant downtimes and demand surges) for a given market, penetration rate, and refueling station size, the model calculates not only the number and cost of the trucks required to deliver the fuel to refueling stations, but also the cost of appropriately-sized liquefiers, pumps, vaporizers, dispensers, truck loading facilities, and storage vessels at terminals and refueling stations. Collectively, these steps or "components" are known as a pathway.

The figure below illustrates three broad liquid hydrogen pathways contained in Version 2.0 of the model. Note that because delivery is broken down into bulk transmission and local distribution—each of which can be by a different mode—loading, conditioning, and storage activities normally associated with a terminal or depot can be located anywhere between the production plant and the city gate. In Pathway 1, they are co-located with production; in Pathways 2 and 3, they are at the city gate.